:Acta . Ndurochlrurgica
Acta Neurochir (Wien) (199 l) I 11: 22-32
9 Springer-Verlag 1991 Printed in Austria
Surgical Approaches to Thoracic Disc Herniations M. EI-Kalliny i j . M. Tew Jr. 1, 2, H. van Loveren 1, 2, and S. Dunsker 1, 2 1 University of Cincinnati College of Medicine, Cincinnati, Ohio 2 Mayfield Neurological Institute, Cincinnati, Ohio, U.S.A.
Summary Early diagnosis of thoracic disc herniations has become more common with the advent of spinal magnetic resonance imaging (MRI). This early diagnosis combined with choosing the optimal surgical approach, to ensure adequate decompression without excessive cord and root manipulation, will achieve the optimum results. It is now clear that more lateral and anterior approaches to the thoracic spine are required to achieve this goal. We report our experience in the operative management of 21 patients with thoracic disc herniation using three different surgical approaches: transpedicular-transfacetal, posterolateral-extrapleural (costotransversectomy) and transthoracic-transpleural. The clinical and radiologic findings and results in all of our cases are reviewed as are the technique of and indication for each of the three surgical approaches.
Keywords: Thoracic disc herniation; magnetic resonance imaging; transpedicular-transfacetal approach; transthoracic-transpleural approach; posterolateral-extrapleural approach. Introduction
Thoracic disc herniations account for less than 2% of all disc operations 2' 12, 13, 15, 18. Carson et al., estimated an annual incidence of one patient per year per 1,000,000 population 9. This rare incidence has been attributed to the relatively limited mobility of the thoracic spine, a consequence of the small size of the thoracic intervertebral discs, restraints of the rib cage and sternum, and anterior-posterior orientation of the apophys+al joints 10,20, 21.22,26. More recently, modern imaging techniques, particularly MRI, have demonstrated a greater prevalence of thoracic disc herniation than previously suspected 6, 3s Symptomatic disc herniation has been reported at every level of the thoracic spine. Herniations at the lower four thoracic interspaces account for one-half to two-thirds of the cases. The middle third of the thoracic spine ranks second; least common are herniations in
the upper thoracic spine. The predominance of herniation at the lower four interspaces has been attributed to the relatively greater mobility of this region 8, 31, 32 The diagnosis of a thoracic disc herniation is suggested by a history of spinal trauma, midthoracic or upper lumbar back pain, numbness or pain distributed in a radicular pattern, paresthesias of the lower extremities and an unsteady spastic gait 2, 4. 5, 18. MRI is currently the most effective screening test in the diagnosis of this disease 6, 31, 35. Its advantages include both sagittal and horizontal imaging, its noninvasive character, the absence of radiation, excellent patient tolerance, and the ability to perform the test in an outpatient setting. In our experience, MRI has a greater than 95% diagnostic accuracy. Myelography followed by post-myelography computed tomography (CT) have comparable accuracy as the sole imaging modality and may also be used to confirm MRI findings 6, 31, 35 Decompressive laminectomy, especially in association with disc removal, has long been discredited as a surgical therapy for thoracic disc herniation because of an unacceptably high incidence of spinal cord damage 1, 3, 7, 13, 15, 16, 23-25, 31. This is due to the narrowness of the subarachnoid space around the thoracic spinal cord and of the thoracic canal 2o. When surgery is attempted in this situation, the slightest manipulation of the cord in order to achieve a transdural or extradural disc excision can be hazardous 1, 7 This dismal prognosis associated with a direct posterior approach has led neurosurgeons and orthopedic surgeons to search for more lateral and anterior approaches to avoid manipulation of the spinal cord 1, 18, 31. In 1960, Hulme advocated a posterolateral-extrapleural approach (costotransversectomy) for thoracic disc herniations. He used this approach in six patients,
38
64
55
66
18
37
44
4
5
6
7
8
9
10
F
M
M
F
F
F
F
F
transthoracic-transpleural hyperreflexia, mild spastic weakness
back pain and bilateral radicular pain, paresthesia both legs
T7-T8 (central calcitied)
transfacetal-transpcdicular
sensory level, hyperreflexia and upgoing toes
back pain unilaterally radiating around abdomen, staggering gait, l'hermitte phenomenon
transthoracic-transpleural
posterolateral-extrapleural
bilateral transfacetal-transpedicular transdural excision of penetrating hard disc
transfacetal-transpedicular !
transfacetal-transpedicular
transfacetal-transpedicular
T7-T8 (lateral)
progressive spastic gait, hyperreflexia and sensory level, Brown Sequard syndrome
localized spinal tenderness
mild paraparesis and hyporeflexia
paraparesis and decreased vibration sensation
paraparesis and sensory level
flaccid monoparcsis and Brown Sequard syndrome, Sensory level L1
posterolateral-extrapleural
paresthesia both legs, l'hermitte phenomenon, Scheuermann's disease
back pain, intercostal neuralgia
back pain and bilateral radicular pain, motor weakness, urinary and fecal incontinene
back pain and motor weakness, tingling and numbness both legs, urinary retention
back pain, bilateral radicular pain, numbness and motor weakness
back pain, paresthesia, motor weakness and urinary urgency
spasticity and hyperreflexia in both legs
T5 T6 T6-T7 (central)
T7-T8 (laterocentral)
T10-TI1 (centrolateral)
T12-L1 (centrolateral)
T1 l-T12 (laterocentral)
T10 Tll (laterocemral)
motor weakness, urinary urgency
~i 9
~-
E
~ >
"~
35
T11 T12 (centrolateral)
transfacetal-transpedicular
3
F
hypoalgesia, C7, Tt, motor weakness of the right hand
32
neck pain, right arm and axillary pain, numbness and tingling
2
M
C6-C7 C7-T1 T 1-T2 (lateral)
54
Approach
1
Signs
~
Symptoms
Location
Age
Case
Sex
:~
Table t. Clinical Findings in 21 Patients with Thoracic Disc Herniation
Age
38
51
32
51
70
68
38
45
43
42
43
Case
11
12
13
I4
15
16
17
18
19
20
21
Table 1 (continued)
F
F
F
F
M
M
F
F
M
F
M
Sex
T1 l-'1"12 (centrolateral calcified)
TI0-T11 (central)
TI I-'1712 (centrolateral)
T8-T9 (centrolateral calcified)
T8-T9 (centrolateral)
T7-T8
Tg-T10 (centrolateral)
T7-T8 (central)
T1 l-T12 (central)
T1 l-T12 (laterocentral)
T6-T7 (central calcified)
T6-T7 (laterocentral)
Location
transthoracic-transpleural posterolateral-extrapleural
progressive spastic paraparesis, sensory level at L1 mild paraparesis and sensory level at L1
back pain, paresthesia and motor weakness back pain, bilateral radicular pain in flanks, lower abdomen and both thighs
posterolateral-ext rapleural
spastic weakness and sensory level at T9
paresthesia both legs, motor weakness, urinary precipitancy
transthoracic-transpleural
transthoracic-transpleural
sensory level at T12, hyperreflexia
back pain, unilateral radicular pain, numbness both legs
mild hyperreflexia, upgoing toes
transthoracic-transpleural
hyperreflexia and spasticity
back pain, bilateral radicular thoracic pain
back pain radiating into right thigh, motor weakness
transthoracic-transpleural
spastic paraparesis, hyperreflexia and sensory level
back pain, weakness and paresthesia
posterolateral-extrapleural
trans facetal-transpedicular
spasticity and hyperreflexia
testicular pain, clumsiness of both legs
spastic weakness and hyperreflexia
transthoracic-transpleural
hyperreflexia and spasticity
paresthesia both legs, occasional radicular pain, motor weakness
back pain, unilateral radiating pain
transfacetal-transpedicular
spasticity and hyperreflexia
back pain and unilateral radicular pain, motor weakness
Approach
Signs
Symptoms
o
:n
P~
o
m"
o
>
.~ r~
7"
.~
M. E1-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations f o u r o f w h o m s h o w e d i m p r o v e m e n t 15. I n 1958, C r a f o o r d a n d c o - w o r k e r s r e p o r t e d the first successful t h o racic disc r e m o v a l u s i n g t h e t r a n s t h o r a c i c - t r a n s p l e u r a l a p p r o a c h 10. P e r o t , M u n r o , R a n s o h o f f a n d c o - w o r k e r s in 1969 also r e p o r t e d the t r a n s t h o r a c i c r e m o v a l o f hern i a t e d discs w i t h e n c o u r a g i n g results 28. I n 1978, P a t terson and Arbit described their transpedicular-transf a c e t a l a p p r o a c h t h a t a l l o w e d t h e s u r g e o n to e n t e r the
25 pain in eight. Twelve patients had a sensory deficit in the form o f decreased sensation to pin-prick, decreased vibratory sense in one or both lower limbs, and a definite thoracic sensory level. Weakness was present in ten patients with the degree of weakness ranging from mild monoparesis to complete paraplegia. There was increased tone associated with hyperreflexia in 12 patients and flaccid weakness with hyporeflexia in two patients. One patient experienced weakness in one lower limb. A Brown-Sequard syndrome was found in four patients and was associated with lateral or centrolateral herniations.
disc s p a c e m o r e l a t e r a l to t h e spinal c o r d in o r d e r to p e r f o r m a d i s c e c t o m y 27. W e p r e s e n t o u r e x p e r i e n c e in the s u r g i c a l m a n a g e m e n t o f 21 p a t i e n t s w i t h t h o r a c i c disc h e r n i a t i o n . T h e clinical r a d i o l o g i c f i n d i n g s , results are d i s c u s s e d as are the t e c h n i q u e s o f s u r g i c a l m a n a g e m e n t
a n d t h e i r in-
dications.
Clinical Material and Methods Clinical Findings
Twenty-one patients (7 men and 14 women) were surgically managed during the period between July 1985 and January 1990. The youngest patient was an eighteen-year-old male who had Scheuermann's disease (kyphotic deformity with multiple disc herniations at the apex of the kyphos) 12.33, 36; the oldest patient was a seventyyear-old female. The mean age was 47 years and there was a female predilection in our patients. Patient data are summarized in Table 1. A history of spinal trauma was obtained in 13 patients. There was mild trauma in 12 patients from torsional injury or from lifting heavy objects. Trauma was severe in one patient previously involved in an automobile accident. The duration between the trauma and the onset of a symptom ranged between one and six years. Lower thoracic or upper lumbar back pain were the initial presenting symptoms in 15 patients. The back pain was associated with a radicular component in 13 patients. The nature of the radicular pain depended on the level of involvement. In three patients with mid-thoracic herniation, the pain was likened to unilateral intercostal neuralgia 19,22, 34 One patient had unilateral testicular pain and another had unilateral anterior thigh pain. One patient with multiple cervicothoracic disc herniations (C6-C7, C7-T1, T1-T2) had right arm and axillary pain. Another two patients had unilateral radiating abdominal pain. In five patients, the radicular pain was bilateral; it radiated into the lower abdomen in three and radiated around the chest in another two patients. This type of presentation was usualiy associated with myelopathy 19,32 Eight patients complained of numbness and tingling in one Ieg. Paresthesia involving both lower limbs and ascending upwards to the lower or mid-abdomen were found in three patients. Eleven patients complained of weakness in one or both legs. Six patients had urinary urgency associated in one patient with bowel dysfunction. In two patients, L'hermitte's phenomenon was described in which an "electric-like" sensation of the lower half of the body was produced upon sudden flexion of the spine or upon straining ~' 5, 12, i9 On examination, significant mid-thoracic and upper lumbar tenderness was found in 13 patients with reproduction of the radicular
Fig. 1. Axial post-myelography CT scan (A) and a Tl-weighted MRI (B) of the thoracic spine of a 32 year-old woman (Case 2) showed a laterocentrai TI I-T~2 herniated disc causing moderate spinal cord compression
26
M. Ei-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations
Radiologic Findings
Management and Surgical Techniques
MRI was the initial tool used for establishing the diagnosis in 19 of the patients. Myelography and post-myelography CT were used for diagnosis in two patients and were confirmatory in six other patients. Disc herniation was single in 16 patients and multiple in five. One patient with Scheuermann's disease had contiguous disc herniations at T5-T6 and T6-T7. X-ray of the thoracic spine showed anterior wedging at multiple thoracic levels from T 6 T 8 with ten degree kyphotic angulation. Another patient had three contiguous lateral disc herniations at C6-C7, C7-TI and T1-T2. The most common appearance of the herniated thoracic discs in Tl-weighted MRI images was of an intermediate signal-intensity mass (dense soft tissue material) protruding posteriorly at the level of the disc space (Figs. 1 and 3). This intermediate-intensity mass appeared to be limited by a narrow low-intensity band, isodense with cerebrospinal fluids (CSF). This appearance may be explained by the central intermediate-intensity material representing the herniated nucleus itself and the surrounding low signal representing the intact posterior longitudinal ligament 35 In two patients the herniated material was of low signal intensity, similar to CSF. This indicated calcification of the disc material. Two other calcified discs were shown by postmyelography CT scan. A T2 weighted sagittal image with resulting inversions of the CSF signal allowed an accurate assessment of the intervertebral disc-CSF interface and the degree of spinal cord compression (Fig. 5). Sagittal and horizontal MRI views defined the strategic location of the herniation (whether central, centrolateral, or lateral), and also showed any migration away from the level of the disc space.
Surgical decompression and excision of a herniated thoracic disc were performed in our patients because of significant root and/or cord compression as indicated by clinical history, neurologic examination and radiologic studies.
Transpedicular-transfacetal Approach ~,27, 31. This surgical approach was used in eight patients and was associated with hemilaminectomy in two patients. Opening the dura and removal of an intradural disc herniation was needed in one patient. The approach was bilateral in one patient due to the difficulty of achieving the discectomy through a unilateral approach. Five of the patients had disc herniations below the level of T10 and two patients had mid-thoracic herniations at T7-T8 and T8-T9. The eighth patient required a transpedicular approach for T1-T2 and C7-T1 disc herniations. All of these patients had lateral disc herniations with or without a central component (Fig. 1). The lateral decubitus position was used. After x-ray localization, the facets posterior to the appropriate disc space and the superior half of the pedicle inferior to the disc space were drilled off. The disc space was entered lateral to the spinal cord and discectomy was performed. After creating a central cavity, posterior disc material was pushed away from the root and spinal cord (Fig. 2).
Posterolateral-extrapleural Approach (Costotransverseetomy)7, 16,23, 3o, 3~. This approach was used in five patients with centrolateral herniations. The herniations had not migrated upwards or downwards under the posterior surface of the vertebral body (Fig. 3). The herniations were between T7 and T9 in four patients and in T11-T12
Fig. 2. Transpedicular-transfacetal approach: (A) Lateral decubitus position is used with affected side up. Midline or paramedian skin incision is done. (B) The facets posterior to the appropriate disc space and the superior half of the pedicle inferior to the disc space are drilled off. (C) In case of intradural penetration of disc fragment, hemilaminectomy can be done followed by opening the dura and retrieval of the intradural fragment
M. EI-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations
27
Fig. 3. A sagittal T~-weighted MRI (A) showed mixed signal intensity of the disc herniation with severe cord compression. (B) Axial TIweighted MRI showed centrolateral disc herniation in the same patient
A
B
C
D
Fig. 4. Posterolateral-extrapleural approach (costotransversectomy). (A) A prone position is now preferred in order to obtain a straight lateral x-ray for localization. A long curved paramedian incision is done with outward convexity. The apex of maximum convexity shouId be 20 cm from midline. (B)-The rib leading to the disc space (15 cm) and the rib above are removed. (C) The proximal 3 cm of the rib leading to the involved disc space is disarticulated from the facets (T 8 in case of TT-T8 herniated disc). (D) The transverse process is removed and the pedicle below the level of the herniated disc are drilled off. The posterior surface of the superior and inferior vertebral bodies are drilled off and discetomy is done. The herniated fragment is then pushed into the emptied disc space
28 space in one other; two of the herniations were calcified. The rightsided approach was used in all of the patients. The approach was made from the side with more deficits found on neurologic examination. In cases where the herniation was central
M. E1-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations in location and in the absence of lateralizing findings or root pain, the right-sided approach was used to avoid the risk of injuring the artery of Adamkiewicz, which usually originates from the left lower intercostal vessels from T8 to L211, tT. 20 The prone position was used in the last three patients for whom this approach was employed (Fig. 4). This position was preferred over the three-quarter prone position in order to obtain a straight lateral or anteroposterior intraoperative x-ray. This proved important because counting the correct rib is crucial to the success of the procedure. If it became necessary to approach the T7-T8 intervertcbral disc, the top of the eighth rib was followed to the demifacets of T7 and T8 vertebral bodies and to the intervertebral disc. If the neurovascular bundle of the eighth rib is followed instead, the wrong level (T8-T9) is reached. It was preferable to expose the rib above as well as the rib leading to the disc space in order to increase the available space to perform discectomy and decompression. Sometimes the rib below was also exposed in order to gain even more exposure. After exposure, the transverse process was removed as well as 2 to 3 cm of the exposed proximal rib which was disarticulated from the demifacets. The pedicle below the level of the herniated disc was drilled off and the lateral aspect of dural sac identified. The disc was incised and discectomy was performed with a curette and a pituitary rongeur. The posterior surface of the superior and inferior vertebral bodies were drilled off and the herniated disc was separated and pushed into the emptied disc space for later removal. Calcified discs were carefully removed using an air drill.
Transthoracie-transpleuralApproach29,3~.This procedure was chosen
Fig. 5. Axial plain CT scan of the thoracic spine (A) of 44 year-old woman showing a T v - T 8 central calcified herniated disc. A sagittal T2-weighted MRI (B) of the same patient showing hypointense signal of the calcified herniated disc with moderate spinal cord compression
for patients with central and centrolateral herniations, particularly those with calcified discs (Fig. 5). It was used in eight patients, most of whom had large central disc herniations. In two patients, the disc was calcified. Some of these herniations had also migrated upwards or downwards, and the main disc fragment was often obscured by the posterior surface of the vertebral body. The approach was also used in a patient with multiple adjacent disc herniations associated with kyphos deformity (Scheuermann's disease). The approach allowed resection of the kyphotic vertebrae and full thoracic cord decompression. The left lateral decubitus position was used (Fig. 6). In order to obtain adequate exposure of the anterolateral surface of the involved disc space, the rib on the level of the affected disc space was removed. For example, the eighth rib was removed to expose the T7-T8 disc space. The approach can be done through the intercostal space one level above the involved disc space without any rib resection, but the exposure is likely to be limited. After exposure of the anterolateral surface of vertebral column, the head of the rib (8th rib) was removed from its articulations with the transverse process and demifacets of the vertebrae. The pedicle was then drilled off to expose more of the lateral surface of the spinal cord. Resection of the posterior surfaces of the inferior and superior vertebral bodies was done to create a cavity through which the herniated disc fragment could be retrieved. The disc was then removed with a high speed drill and curettes after having been pushed away from the spinal cord. The spine is usually stable because two-thirds of the vertebrae are still intact, together with facets and posterior structures. Therefore, no fusion is required. Postoperativ~ morbidity was often significant after this approach because part of the lung must be collapsed and the pleura opened. However, postoperative morbidity resolved in most cases.
M. EI-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations
29
Results
Immediately after surgery, eleven patients showed significant improvement of their back and radicular pain. Eleven patients had disappearance of their paresthesia and nine patients showed improvement of their weakness. After a follow-up period of three months to four years with a mean of one year, eight patients (38%) were made asymptomatic and showed marked improvement of their neurologic deficit (cured). Another nine patients (43%) showed significant improvement of their symptoms and neurologic deficits. The total improvement rate was 81%. Three patients were unchanged (14%) after surgery. One of the three showed no change of his motor functions (spastic paraparesis) after a transthoracic approach. This same patient developed a postoperative stroke. Another patient experienced no change of her intercostal neuralgia after a posterolateral-extrapleural approach. The third unchanged patient continued to have low backache and paresthesia of the lower limbs after a transpedicular-transfacetal approach. One patient (5%) became worse and remained so after a transthoracic approach for a centrally herniated disc. This deterioration was attributed to manipulation of an already compromised cord. Our results are summarized in Table 2. Persistent pleural effusion occurred in two patients after the transthoracic-transpleural approach. It was treated conservatively in one patient and required reexploration and sealing of a dural tear with fibrin glue in the second.
JZ
Fig. 6. Transthoracic-transpleural approach. (A) Left lateral decubitus position is used. Transverse skin is done over the rib to be removed. (B) The rib on the affected disc space is removed (8th rib in TT-T8 herniated disc). The head of the rib is then disarticulated from the demifacets and the transverse process. (C) The pedicle inferior the disc space is drilled off to expose the lateral surface of the spinal cord. The posterior surface of the superior and inferior vertebral bodies are drilled off and disc is removed. The herniated disc then can be pushed into this cavity to be removed
Discussion
Thoracic disc herniations are now recognized during the early stage of nerve root irritation or mild cord compression. We believe that in the presence of a history of trauma, numbness and painful paresthesia, midthoracic or upper lumbar back pain, and an unsteady
Table 2. Postoperative Results. Follow-Up P e r i o d - 3 Months-4 Years, Mean = 1 Year Cured
Improved
Unchanged Worse
Transpedicular-transfacetal Transthoracic-transpleural Postcrolateral-extrapleural
4 3 1
3 3 3
i 1 t
0 1 0
Total
8 (38%)
9 (43%)
3 (14%)
1 (5%)
Cured: Have no symptoms or deficits. Improved: Have some residual deficit with no symptoms.
Total 8 (38%) 8 (38%) 5 (24%) 21
30
M. E1-Kallinyet al.: SurgicalApproachesto ThoracicDisc Herniations
spastic gait, the correct clinical diagnosis should be made in the majority of patients. This underscores the importance of choosing the optimal surgical approach that minimizes root and cord manipulation and maximizes favorable results. Choosing the optimal approach in thoracic disc herniation depends to a large extent upon the training and experience of the individual neurosurgeon, as well as the general medical condition of the patient. Patients in poor general condition should not undergo a lengthy and formidable operation. The patient in our series who developed a postoperative stroke probably did not tolerate a period of hypotension during a transthoracic approach. A number of other factors, however, must also be considered when determining which of the three operative techniques to employ 3l. These factors are summarized in Table 3. The location and size of the herniated portion of the thoracic disc as determined by MRI or postmyelography CT are of utmost importance. Lateral herniations are best managed using the transpediculartransfacetal approach. The transthoracic-transpleural approach, however, is most effective for central herniations. Centrolateral herniations can be repaired using the posterolateral-extrapleural approach. In addition, the level of the herniation should be a major consideration. At the extremes of the thoracic spine from T2-T4 and from T10-T12, a thoracic disc can only be reached with great difficulty using the transthoracic approach. Moreover, the scapular girdle blocks lateral access from T2-T4 making the costotransversectomy also very difficult in this region. Consequently, we recommend the transpedicular approach from T2-T4. In fact, we used this approach in one case in our series of multiple high thoracic disc herniations.
Table 3. Important Factors in Choosing a Surgical Approach 1. Trainingand experienceof surgeon 2. Generalmedicalconditionof patient 3, Locationof disc (central, lateral, or centrolateral) 4. Sizeof disc herniation 5. Levelof disc herniation 6. Multiplicityof disc herniation 7. Migrationof disc fragment(upwards or downwards) 8. Associatedspinaldiseases(thoracicstenosis,Scheuermann'sdisease) 9. Consistencyof disc (hard, soft, or calcified) 10. Locationof artery of Adamkiewicz 11. Intraduralrupture of disc
The posterolateral and transpedicular approaches are good options from T10-L1 which is the region most commonly affected by thoracic disc herniation. C7-T1 herniations can be regarded as lower cervical disease and can be managed using the standard anterior cervical discectomy. Between T4 and T10, the level of herniation is not as important a factor, and the location and size of the herniation should be given greater weight. Migration of a disc fragment upwards or downwards necessitates a more anterior approach in which part of the vertebral body must be removed in order to retrieve the free fragment. The anterior approach is also indicated in patients with Scheuermann's disease to correct both the kyphotic deformity and the disc herniation. We used this strategy in our series in a patient with Scheuermann's disease 35, 36. Because a corpectomy is performed with this procedure, a fusion is needed followed by an extended period of bracing and bed rest. Fusion is not necessary following the standard transthoracic and other two approaches because the limited amount of bone resection does not affect the stability of the spine. Calcified central discs should also be managed using the transthoracic-transpleural approach. An anterior approach should be used under ,these circumstances because access to the anterior and anterolateral regions of the spinal canal is more direct than with a posterolateral approach. We used an anterior approach in two patients with calcified central herniations. When the calcified herniations were more centrolateral in location, costotransversectomy can be performed, as we did in two patients in our series. These calcified discs should be drilled until a very thin shell remains before being delivered out. The transthoracic approach should be done from the right side to avoid injury of the artery of Adamkiewicz. Also, the right-sided approach allows a more adequate exposure. Moreover, extreme care should be exercised when working near the intervertebral foramina at these levels, especially on the left, when a transpedicular or posterolateral approach is employed. We found that intradural penetration of a disc fragment necessitates the use of a transpedicular approach followed by a laminectomy. In such a case, the herniated disc is first removed extradurally. Following this, the dura is opened posteriorly and residual penetrated fragment is excised 31. Finally, if any canal stenosis is present in addition to the disc herniation, the posterior approach offers the most advantage overall. Through a laminectomy,
M. E1-Kallinyet al.: Surgical Approaches to Thoracic Disc Herniations combined with drilling unilaterally the facetal joint with the pedicle, the disc can be removed and the spinal cord decompressed during the same operation 3. Conservative treatment still has a place in the management of patients with mild cord compression. It is now recognized, largely because of the use of M R I , that a minimal amount of compression is often welltolerated and that immediate surgical therapy is not indicated. In addition, M R I can be used in conjunction with conservative therapy to monitor any changes in the amount of compression over time and to determine when surgery is advisable. There has been marked improvement in the results of surgery of thoracic disc herniations after abandonment of decompressive laminectomy with intradural and/or extradural removal of disc herniation. O f 119 cases involving laminectomy reviewed by Arce et al., 28% were made worse and 11% remained unchanged. By contrast, less than 5% of our patients were made worse after surgery while 14% were unchanged. This lack of improvement in our series is best explained by a relatively long period of spinal cord compression prior to surgery. Moreover, our overall improvement rate of 81% was similar to a series reported by Sekhar et al., in which 10 out of 12 patients (83%) were cured or improved after using more anterior approaches for cord or root compression. Our improvement rate of 87.5% (7 out of 8 patients) using the transpedicular approach again is similar to the results of a series reported by Arce et al., in which 82% of patients that were reviewed, twenty-seven patients were improved or made asymptomatic. In this same series, 11% remained unchanged and 7% were made worse. No patient in our series undergoing a transpedicular approach was made worse, and 12.5% remained unchanged. O f five cases operated on using the costotransversectomy approach, four (80%) were cured or improved and one patient (20%) was unchanged. This is similar to the series of 43 cases collected from the literature by Arce et al., in which 88% were improved or made asymptomatic and 12% remained unchanged 1, 31 All 12 cases collected from the literature in which the transthoracic approach was used were improved or made asymptomatic. N o patient was unchanged or worse after this approach. In our series six patients were improved or cured. One patient was unchanged and one patient was made worse due to manipulating compressed spinal cord. The changes of successful treatment in thoracic disc
31 herniations depend on the preoperative neurologic status. With the use of M R I in diagnosis, we will be better able to operate on patients with mild preoperative neurologic deficits. In addition, further refinement of microsurgical technique will help to achieve favorable results. I n s u m m a r y , it is now possible to diagnose thoracic disc herniations during the early stages of nerve root irritation and mild spinal cord compression. While nonsurgical therapy can still be used in the initial treatment of the disease, m a n y patients will eventually require surgery. Determining which of the surgical approaches is most appropriate entails considering the a n a t o m y of the herniation as seen by M R I and/or CT, the ability of the patient to undergo a major operation, the presence or absence of coexisting spinal diseases such as thoracic stenosis or Scheuermann's disease, and the surgeon's level of expertise. By taking such a comprehensive approach, one can expect gratifying surgical results with a minimum of postoperative complications.
Acknowledgement The authors wish to thank Janet C. Witzleben for editorial support and Glorya Lang O'Conner for administrative support.
References 1. Arce CA, Dohrmann, GJ (1985) Thoracic disc herniation. Surg Neurol 23:356-361 2. Arseni C, Nash F (1960) Thoracic intervertebral disc protrusions: A clinical study. J Neurosurg 17:418-430 3. Barnett GH, Hardy RW Jr., Little JR et al (1987) Thoracic spinal canal stenosis. J Neurosurg 66:338-344 4. BenjaminV, Ransohoff J (1982) Thoracic disc disease. In: Rothman RH, SimeoneFA (eds)The Spine, Vol 1, t9, W. B. Saunders Company, Philadelphia, pp 500-507 5. Benson MKD, Byrnes DP (1975) The clinical syndromes and surgical treatment of thoracic intervertebraldisc prolapse. J Bone Joint Surg 57B: 471-477 6. Blumenkopf B (1988) Thoracic intervertebral disc herniations, diagnostic value of magnetic resonance imaging. Neurosurgery 23:36-40 7. Capener N (1954) The evolution of lateral rhachotomy. J Bone Joint Surg 36B: 173-179 8. Caron JP, Djindjian R, Julina H et al(1971) Les hernies discales dorsales. Ann Med Intern (Paris) 22:675-688 9. Carson JP, Gumpert J, Jefferson A, Julian H et al (1971) Diagnosis and treatment of thoracic intervertebraldisc protrusions. J Neurol Neurosurg Psychiatry 34:68-77 10. Crafoord C, Hiertonn T, Lindblom K, Olsson SE (1958) Spinal cord compression caused by a protruded thoracic disc. Report of a case treated with antero-lateral fenestration of the disc. Acta Orthop Scand 28:103-107 11. Crock HWJ, Yoshizawa H (1977) The blood supply of the vertebral column and spinal cord in man. Springer, Wien New York
32
M. E1-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations
12. De Palma AF, Rothman RH (1970) The intervertebral disc. W. B. Saunders Company, pp 171-180 13. Gowers WR (1892) Diseases of the nervous system, 2nd ed, Vol 1. Churchill, London, 260 pp 14. Hawk WA (1936) Spinal compression caused by ecchondrosis of the intervertebral fibrocartilage with a review of the recent literature. Brain 59:204-224 15. Hulme A (1960) The surgical approach to thoracic intervertebral disc protrusions. J Neurol Neurosurg Psychiatry 23:133-137 16. Larson SJ, Holst RA, Hemmy DC et al (1976) Lateral extracavitary approach to traumatic lesions of the thoracic and lumbar spine. J Neurosurg 45:628-637 17. Lazorthes G, Poulhes J, Eastide G, Chanholle AR, Zadeh O (1962) La vascularization de la Moele Epiniere Pathologic Vasculaire de la Molle. XXV Reunion Neurologique Internationale, Masson et Cie, Paris, pp 5-27 18. Lobosky JM, Hitchon PW, McDonnell DE (1984) Transthoracic anterolateral decompression of thoracic spinal lesions. J Neurosurg 14:26-30 19. Logue V (1952) Thoracic intervertebral disc prolapse with spinal cord compression. J Neurol Neurosurg Psychiatry 15:227-241 20. Louis R (1983) Surgery of the spine. Surgical anatomy and operative approaches. Springer, Berlin Heidelberg New York, pp 24-66 21. Love JG, Keller EJ (1950) Root pain and paraplegia due to protrusions of thoracic intervertebral discs. J Neurosurg 7:62-69 22. Love JG, Schorn VG (1965) Thoracic-disc protrusions. JAMA 191:627-631
23. Menard V (1900) Etude pratique sur le mal de pott. Paris 24. Middleton GS, Teacher JH (1911) Injury of the spinal cord due to rupture of an intervertebral disc during muscular effort. Glasgow Med J 76:1-6
25. Mixter WJ, Barr JS (1934) Rupture of intervertebral disc with involvement of the spinal canal. N Engl J Med 211:210-215 26. Muller R (1951) Protrusion of thoracic intervertebral discs with compression of the spinal cord. Acta Med Scand 139:99-104 27. Patterson RH, Arbit E (1978) A surgical approach through the pedicle to protruded thoracic discs. J Neurosurg 48:768-772 28. Perot P, Munro DD (1969) Transthoracic removal of midline thoracic disc protrusions causing spinal cord compression. J Neurosurg 31:452458 29. Ransohoff J, Spencer F, Siew F, Gage L (1969) Transthoracic disc protrusions causing spinal cord compression. J Neurosurg 31:459-461 30. Seddon HJ (1936) Pott's paraplegia; prognosis and treatment. Br J Surg 22:769-799 31. Sekhar LN, Janetta PJ (1983) Thoracic disc herniations: Operative approaches and results. J Neurosurg 12, 3:303-305 32. Tovi D, Strang RR (1960) Thoracic intervertebral disc protrusions. Acta Chir Scand [Suppl] 267:1-41 33. Van Landingham JH (1954) Herniation of thoracic intervertebral discs with spinal cord compression in the kyphosis dorsalis juvenilis (Scheuermann's disease). Case Report. J Neurosurg 11: 327-329 34. Verbiest H (1954) A radicular syndrome from development narrowing of the lumbar vertebral canal. J Bone Joint Surg (Br) 36:230-237 35. William MP, Cherrman CR, Husband JE (1989) Significance of thoracic disc herniation demonstrated by MR Imaging. J Comp Assist Tomogr 13 (2): 211-214 36. Yablon JS, Kasdon DL, Levine H (1984) Thoracic cord compression in Scheuermann's disease. Spine 13:896-898 Correspondence and Reprints: M. E1-Kalliny, M.D., University of Cincinnati College of Medicine, Cincinnati, Ohio, U.S.A.
Acta Neurochir (Wien) (199 l) I 11: 22-32
9 Springer-Verlag 1991 Printed in Austria
Surgical Approaches to Thoracic Disc Herniations M. EI-Kalliny i j . M. Tew Jr. 1, 2, H. van Loveren 1, 2, and S. Dunsker 1, 2 1 University of Cincinnati College of Medicine, Cincinnati, Ohio 2 Mayfield Neurological Institute, Cincinnati, Ohio, U.S.A.
Summary Early diagnosis of thoracic disc herniations has become more common with the advent of spinal magnetic resonance imaging (MRI). This early diagnosis combined with choosing the optimal surgical approach, to ensure adequate decompression without excessive cord and root manipulation, will achieve the optimum results. It is now clear that more lateral and anterior approaches to the thoracic spine are required to achieve this goal. We report our experience in the operative management of 21 patients with thoracic disc herniation using three different surgical approaches: transpedicular-transfacetal, posterolateral-extrapleural (costotransversectomy) and transthoracic-transpleural. The clinical and radiologic findings and results in all of our cases are reviewed as are the technique of and indication for each of the three surgical approaches.
Keywords: Thoracic disc herniation; magnetic resonance imaging; transpedicular-transfacetal approach; transthoracic-transpleural approach; posterolateral-extrapleural approach. Introduction
Thoracic disc herniations account for less than 2% of all disc operations 2' 12, 13, 15, 18. Carson et al., estimated an annual incidence of one patient per year per 1,000,000 population 9. This rare incidence has been attributed to the relatively limited mobility of the thoracic spine, a consequence of the small size of the thoracic intervertebral discs, restraints of the rib cage and sternum, and anterior-posterior orientation of the apophys+al joints 10,20, 21.22,26. More recently, modern imaging techniques, particularly MRI, have demonstrated a greater prevalence of thoracic disc herniation than previously suspected 6, 3s Symptomatic disc herniation has been reported at every level of the thoracic spine. Herniations at the lower four thoracic interspaces account for one-half to two-thirds of the cases. The middle third of the thoracic spine ranks second; least common are herniations in
the upper thoracic spine. The predominance of herniation at the lower four interspaces has been attributed to the relatively greater mobility of this region 8, 31, 32 The diagnosis of a thoracic disc herniation is suggested by a history of spinal trauma, midthoracic or upper lumbar back pain, numbness or pain distributed in a radicular pattern, paresthesias of the lower extremities and an unsteady spastic gait 2, 4. 5, 18. MRI is currently the most effective screening test in the diagnosis of this disease 6, 31, 35. Its advantages include both sagittal and horizontal imaging, its noninvasive character, the absence of radiation, excellent patient tolerance, and the ability to perform the test in an outpatient setting. In our experience, MRI has a greater than 95% diagnostic accuracy. Myelography followed by post-myelography computed tomography (CT) have comparable accuracy as the sole imaging modality and may also be used to confirm MRI findings 6, 31, 35 Decompressive laminectomy, especially in association with disc removal, has long been discredited as a surgical therapy for thoracic disc herniation because of an unacceptably high incidence of spinal cord damage 1, 3, 7, 13, 15, 16, 23-25, 31. This is due to the narrowness of the subarachnoid space around the thoracic spinal cord and of the thoracic canal 2o. When surgery is attempted in this situation, the slightest manipulation of the cord in order to achieve a transdural or extradural disc excision can be hazardous 1, 7 This dismal prognosis associated with a direct posterior approach has led neurosurgeons and orthopedic surgeons to search for more lateral and anterior approaches to avoid manipulation of the spinal cord 1, 18, 31. In 1960, Hulme advocated a posterolateral-extrapleural approach (costotransversectomy) for thoracic disc herniations. He used this approach in six patients,
38
64
55
66
18
37
44
4
5
6
7
8
9
10
F
M
M
F
F
F
F
F
transthoracic-transpleural hyperreflexia, mild spastic weakness
back pain and bilateral radicular pain, paresthesia both legs
T7-T8 (central calcitied)
transfacetal-transpcdicular
sensory level, hyperreflexia and upgoing toes
back pain unilaterally radiating around abdomen, staggering gait, l'hermitte phenomenon
transthoracic-transpleural
posterolateral-extrapleural
bilateral transfacetal-transpedicular transdural excision of penetrating hard disc
transfacetal-transpedicular !
transfacetal-transpedicular
transfacetal-transpedicular
T7-T8 (lateral)
progressive spastic gait, hyperreflexia and sensory level, Brown Sequard syndrome
localized spinal tenderness
mild paraparesis and hyporeflexia
paraparesis and decreased vibration sensation
paraparesis and sensory level
flaccid monoparcsis and Brown Sequard syndrome, Sensory level L1
posterolateral-extrapleural
paresthesia both legs, l'hermitte phenomenon, Scheuermann's disease
back pain, intercostal neuralgia
back pain and bilateral radicular pain, motor weakness, urinary and fecal incontinene
back pain and motor weakness, tingling and numbness both legs, urinary retention
back pain, bilateral radicular pain, numbness and motor weakness
back pain, paresthesia, motor weakness and urinary urgency
spasticity and hyperreflexia in both legs
T5 T6 T6-T7 (central)
T7-T8 (laterocentral)
T10-TI1 (centrolateral)
T12-L1 (centrolateral)
T1 l-T12 (laterocentral)
T10 Tll (laterocemral)
motor weakness, urinary urgency
~i 9
~-
E
~ >
"~
35
T11 T12 (centrolateral)
transfacetal-transpedicular
3
F
hypoalgesia, C7, Tt, motor weakness of the right hand
32
neck pain, right arm and axillary pain, numbness and tingling
2
M
C6-C7 C7-T1 T 1-T2 (lateral)
54
Approach
1
Signs
~
Symptoms
Location
Age
Case
Sex
:~
Table t. Clinical Findings in 21 Patients with Thoracic Disc Herniation
Age
38
51
32
51
70
68
38
45
43
42
43
Case
11
12
13
I4
15
16
17
18
19
20
21
Table 1 (continued)
F
F
F
F
M
M
F
F
M
F
M
Sex
T1 l-'1"12 (centrolateral calcified)
TI0-T11 (central)
TI I-'1712 (centrolateral)
T8-T9 (centrolateral calcified)
T8-T9 (centrolateral)
T7-T8
Tg-T10 (centrolateral)
T7-T8 (central)
T1 l-T12 (central)
T1 l-T12 (laterocentral)
T6-T7 (central calcified)
T6-T7 (laterocentral)
Location
transthoracic-transpleural posterolateral-extrapleural
progressive spastic paraparesis, sensory level at L1 mild paraparesis and sensory level at L1
back pain, paresthesia and motor weakness back pain, bilateral radicular pain in flanks, lower abdomen and both thighs
posterolateral-ext rapleural
spastic weakness and sensory level at T9
paresthesia both legs, motor weakness, urinary precipitancy
transthoracic-transpleural
transthoracic-transpleural
sensory level at T12, hyperreflexia
back pain, unilateral radicular pain, numbness both legs
mild hyperreflexia, upgoing toes
transthoracic-transpleural
hyperreflexia and spasticity
back pain, bilateral radicular thoracic pain
back pain radiating into right thigh, motor weakness
transthoracic-transpleural
spastic paraparesis, hyperreflexia and sensory level
back pain, weakness and paresthesia
posterolateral-extrapleural
trans facetal-transpedicular
spasticity and hyperreflexia
testicular pain, clumsiness of both legs
spastic weakness and hyperreflexia
transthoracic-transpleural
hyperreflexia and spasticity
paresthesia both legs, occasional radicular pain, motor weakness
back pain, unilateral radiating pain
transfacetal-transpedicular
spasticity and hyperreflexia
back pain and unilateral radicular pain, motor weakness
Approach
Signs
Symptoms
o
:n
P~
o
m"
o
>
.~ r~
7"
.~
M. E1-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations f o u r o f w h o m s h o w e d i m p r o v e m e n t 15. I n 1958, C r a f o o r d a n d c o - w o r k e r s r e p o r t e d the first successful t h o racic disc r e m o v a l u s i n g t h e t r a n s t h o r a c i c - t r a n s p l e u r a l a p p r o a c h 10. P e r o t , M u n r o , R a n s o h o f f a n d c o - w o r k e r s in 1969 also r e p o r t e d the t r a n s t h o r a c i c r e m o v a l o f hern i a t e d discs w i t h e n c o u r a g i n g results 28. I n 1978, P a t terson and Arbit described their transpedicular-transf a c e t a l a p p r o a c h t h a t a l l o w e d t h e s u r g e o n to e n t e r the
25 pain in eight. Twelve patients had a sensory deficit in the form o f decreased sensation to pin-prick, decreased vibratory sense in one or both lower limbs, and a definite thoracic sensory level. Weakness was present in ten patients with the degree of weakness ranging from mild monoparesis to complete paraplegia. There was increased tone associated with hyperreflexia in 12 patients and flaccid weakness with hyporeflexia in two patients. One patient experienced weakness in one lower limb. A Brown-Sequard syndrome was found in four patients and was associated with lateral or centrolateral herniations.
disc s p a c e m o r e l a t e r a l to t h e spinal c o r d in o r d e r to p e r f o r m a d i s c e c t o m y 27. W e p r e s e n t o u r e x p e r i e n c e in the s u r g i c a l m a n a g e m e n t o f 21 p a t i e n t s w i t h t h o r a c i c disc h e r n i a t i o n . T h e clinical r a d i o l o g i c f i n d i n g s , results are d i s c u s s e d as are the t e c h n i q u e s o f s u r g i c a l m a n a g e m e n t
a n d t h e i r in-
dications.
Clinical Material and Methods Clinical Findings
Twenty-one patients (7 men and 14 women) were surgically managed during the period between July 1985 and January 1990. The youngest patient was an eighteen-year-old male who had Scheuermann's disease (kyphotic deformity with multiple disc herniations at the apex of the kyphos) 12.33, 36; the oldest patient was a seventyyear-old female. The mean age was 47 years and there was a female predilection in our patients. Patient data are summarized in Table 1. A history of spinal trauma was obtained in 13 patients. There was mild trauma in 12 patients from torsional injury or from lifting heavy objects. Trauma was severe in one patient previously involved in an automobile accident. The duration between the trauma and the onset of a symptom ranged between one and six years. Lower thoracic or upper lumbar back pain were the initial presenting symptoms in 15 patients. The back pain was associated with a radicular component in 13 patients. The nature of the radicular pain depended on the level of involvement. In three patients with mid-thoracic herniation, the pain was likened to unilateral intercostal neuralgia 19,22, 34 One patient had unilateral testicular pain and another had unilateral anterior thigh pain. One patient with multiple cervicothoracic disc herniations (C6-C7, C7-T1, T1-T2) had right arm and axillary pain. Another two patients had unilateral radiating abdominal pain. In five patients, the radicular pain was bilateral; it radiated into the lower abdomen in three and radiated around the chest in another two patients. This type of presentation was usualiy associated with myelopathy 19,32 Eight patients complained of numbness and tingling in one Ieg. Paresthesia involving both lower limbs and ascending upwards to the lower or mid-abdomen were found in three patients. Eleven patients complained of weakness in one or both legs. Six patients had urinary urgency associated in one patient with bowel dysfunction. In two patients, L'hermitte's phenomenon was described in which an "electric-like" sensation of the lower half of the body was produced upon sudden flexion of the spine or upon straining ~' 5, 12, i9 On examination, significant mid-thoracic and upper lumbar tenderness was found in 13 patients with reproduction of the radicular
Fig. 1. Axial post-myelography CT scan (A) and a Tl-weighted MRI (B) of the thoracic spine of a 32 year-old woman (Case 2) showed a laterocentrai TI I-T~2 herniated disc causing moderate spinal cord compression
26
M. Ei-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations
Radiologic Findings
Management and Surgical Techniques
MRI was the initial tool used for establishing the diagnosis in 19 of the patients. Myelography and post-myelography CT were used for diagnosis in two patients and were confirmatory in six other patients. Disc herniation was single in 16 patients and multiple in five. One patient with Scheuermann's disease had contiguous disc herniations at T5-T6 and T6-T7. X-ray of the thoracic spine showed anterior wedging at multiple thoracic levels from T 6 T 8 with ten degree kyphotic angulation. Another patient had three contiguous lateral disc herniations at C6-C7, C7-TI and T1-T2. The most common appearance of the herniated thoracic discs in Tl-weighted MRI images was of an intermediate signal-intensity mass (dense soft tissue material) protruding posteriorly at the level of the disc space (Figs. 1 and 3). This intermediate-intensity mass appeared to be limited by a narrow low-intensity band, isodense with cerebrospinal fluids (CSF). This appearance may be explained by the central intermediate-intensity material representing the herniated nucleus itself and the surrounding low signal representing the intact posterior longitudinal ligament 35 In two patients the herniated material was of low signal intensity, similar to CSF. This indicated calcification of the disc material. Two other calcified discs were shown by postmyelography CT scan. A T2 weighted sagittal image with resulting inversions of the CSF signal allowed an accurate assessment of the intervertebral disc-CSF interface and the degree of spinal cord compression (Fig. 5). Sagittal and horizontal MRI views defined the strategic location of the herniation (whether central, centrolateral, or lateral), and also showed any migration away from the level of the disc space.
Surgical decompression and excision of a herniated thoracic disc were performed in our patients because of significant root and/or cord compression as indicated by clinical history, neurologic examination and radiologic studies.
Transpedicular-transfacetal Approach ~,27, 31. This surgical approach was used in eight patients and was associated with hemilaminectomy in two patients. Opening the dura and removal of an intradural disc herniation was needed in one patient. The approach was bilateral in one patient due to the difficulty of achieving the discectomy through a unilateral approach. Five of the patients had disc herniations below the level of T10 and two patients had mid-thoracic herniations at T7-T8 and T8-T9. The eighth patient required a transpedicular approach for T1-T2 and C7-T1 disc herniations. All of these patients had lateral disc herniations with or without a central component (Fig. 1). The lateral decubitus position was used. After x-ray localization, the facets posterior to the appropriate disc space and the superior half of the pedicle inferior to the disc space were drilled off. The disc space was entered lateral to the spinal cord and discectomy was performed. After creating a central cavity, posterior disc material was pushed away from the root and spinal cord (Fig. 2).
Posterolateral-extrapleural Approach (Costotransverseetomy)7, 16,23, 3o, 3~. This approach was used in five patients with centrolateral herniations. The herniations had not migrated upwards or downwards under the posterior surface of the vertebral body (Fig. 3). The herniations were between T7 and T9 in four patients and in T11-T12
Fig. 2. Transpedicular-transfacetal approach: (A) Lateral decubitus position is used with affected side up. Midline or paramedian skin incision is done. (B) The facets posterior to the appropriate disc space and the superior half of the pedicle inferior to the disc space are drilled off. (C) In case of intradural penetration of disc fragment, hemilaminectomy can be done followed by opening the dura and retrieval of the intradural fragment
M. EI-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations
27
Fig. 3. A sagittal T~-weighted MRI (A) showed mixed signal intensity of the disc herniation with severe cord compression. (B) Axial TIweighted MRI showed centrolateral disc herniation in the same patient
A
B
C
D
Fig. 4. Posterolateral-extrapleural approach (costotransversectomy). (A) A prone position is now preferred in order to obtain a straight lateral x-ray for localization. A long curved paramedian incision is done with outward convexity. The apex of maximum convexity shouId be 20 cm from midline. (B)-The rib leading to the disc space (15 cm) and the rib above are removed. (C) The proximal 3 cm of the rib leading to the involved disc space is disarticulated from the facets (T 8 in case of TT-T8 herniated disc). (D) The transverse process is removed and the pedicle below the level of the herniated disc are drilled off. The posterior surface of the superior and inferior vertebral bodies are drilled off and discetomy is done. The herniated fragment is then pushed into the emptied disc space
28 space in one other; two of the herniations were calcified. The rightsided approach was used in all of the patients. The approach was made from the side with more deficits found on neurologic examination. In cases where the herniation was central
M. E1-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations in location and in the absence of lateralizing findings or root pain, the right-sided approach was used to avoid the risk of injuring the artery of Adamkiewicz, which usually originates from the left lower intercostal vessels from T8 to L211, tT. 20 The prone position was used in the last three patients for whom this approach was employed (Fig. 4). This position was preferred over the three-quarter prone position in order to obtain a straight lateral or anteroposterior intraoperative x-ray. This proved important because counting the correct rib is crucial to the success of the procedure. If it became necessary to approach the T7-T8 intervertcbral disc, the top of the eighth rib was followed to the demifacets of T7 and T8 vertebral bodies and to the intervertebral disc. If the neurovascular bundle of the eighth rib is followed instead, the wrong level (T8-T9) is reached. It was preferable to expose the rib above as well as the rib leading to the disc space in order to increase the available space to perform discectomy and decompression. Sometimes the rib below was also exposed in order to gain even more exposure. After exposure, the transverse process was removed as well as 2 to 3 cm of the exposed proximal rib which was disarticulated from the demifacets. The pedicle below the level of the herniated disc was drilled off and the lateral aspect of dural sac identified. The disc was incised and discectomy was performed with a curette and a pituitary rongeur. The posterior surface of the superior and inferior vertebral bodies were drilled off and the herniated disc was separated and pushed into the emptied disc space for later removal. Calcified discs were carefully removed using an air drill.
Transthoracie-transpleuralApproach29,3~.This procedure was chosen
Fig. 5. Axial plain CT scan of the thoracic spine (A) of 44 year-old woman showing a T v - T 8 central calcified herniated disc. A sagittal T2-weighted MRI (B) of the same patient showing hypointense signal of the calcified herniated disc with moderate spinal cord compression
for patients with central and centrolateral herniations, particularly those with calcified discs (Fig. 5). It was used in eight patients, most of whom had large central disc herniations. In two patients, the disc was calcified. Some of these herniations had also migrated upwards or downwards, and the main disc fragment was often obscured by the posterior surface of the vertebral body. The approach was also used in a patient with multiple adjacent disc herniations associated with kyphos deformity (Scheuermann's disease). The approach allowed resection of the kyphotic vertebrae and full thoracic cord decompression. The left lateral decubitus position was used (Fig. 6). In order to obtain adequate exposure of the anterolateral surface of the involved disc space, the rib on the level of the affected disc space was removed. For example, the eighth rib was removed to expose the T7-T8 disc space. The approach can be done through the intercostal space one level above the involved disc space without any rib resection, but the exposure is likely to be limited. After exposure of the anterolateral surface of vertebral column, the head of the rib (8th rib) was removed from its articulations with the transverse process and demifacets of the vertebrae. The pedicle was then drilled off to expose more of the lateral surface of the spinal cord. Resection of the posterior surfaces of the inferior and superior vertebral bodies was done to create a cavity through which the herniated disc fragment could be retrieved. The disc was then removed with a high speed drill and curettes after having been pushed away from the spinal cord. The spine is usually stable because two-thirds of the vertebrae are still intact, together with facets and posterior structures. Therefore, no fusion is required. Postoperativ~ morbidity was often significant after this approach because part of the lung must be collapsed and the pleura opened. However, postoperative morbidity resolved in most cases.
M. EI-Kalliny et al.: Surgical Approaches to Thoracic Disc Herniations
29
Results
Immediately after surgery, eleven patients showed significant improvement of their back and radicular pain. Eleven patients had disappearance of their paresthesia and nine patients showed improvement of their weakness. After a follow-up period of three months to four years with a mean of one year, eight patients (38%) were made asymptomatic and showed marked improvement of their neurologic deficit (cured). Another nine patients (43%) showed significant improvement of their symptoms and neurologic deficits. The total improvement rate was 81%. Three patients were unchanged (14%) after surgery. One of the three showed no change of his motor functions (spastic paraparesis) after a transthoracic approach. This same patient developed a postoperative stroke. Another patient experienced no change of her intercostal neuralgia after a posterolateral-extrapleural approach. The third unchanged patient continued to have low backache and paresthesia of the lower limbs after a transpedicular-transfacetal approach. One patient (5%) became worse and remained so after a transthoracic approach for a centrally herniated disc. This deterioration was attributed to manipulation of an already compromised cord. Our results are summarized in Table 2. Persistent pleural effusion occurred in two patients after the transthoracic-transpleural approach. It was treated conservatively in one patient and required reexploration and sealing of a dural tear with fibrin glue in the second.
JZ
Fig. 6. Transthoracic-transpleural approach. (A) Left lateral decubitus position is used. Transverse skin is done over the rib to be removed. (B) The rib on the affected disc space is removed (8th rib in TT-T8 herniated disc). The head of the rib is then disarticulated from the demifacets and the transverse process. (C) The pedicle inferior the disc space is drilled off to expose the lateral surface of the spinal cord. The posterior surface of the superior and inferior vertebral bodies are drilled off and disc is removed. The herniated disc then can be pushed into this cavity to be removed
Discussion
Thoracic disc herniations are now recognized during the early stage of nerve root irritation or mild cord compression. We believe that in the presence of a history of trauma, numbness and painful paresthesia, midthoracic or upper lumbar back pain, and an unsteady
Table 2. Postoperative Results. Follow-Up P e r i o d - 3 Months-4 Years, Mean = 1 Year Cured
Improved
Unchanged Worse
Transpedicular-transfacetal Transthoracic-transpleural Postcrolateral-extrapleural
4 3 1
3 3 3
i 1 t
0 1 0
Total
8 (38%)
9 (43%)
3 (14%)
1 (5%)
Cured: Have no symptoms or deficits. Improved: Have some residual deficit with no symptoms.
Total 8 (38%) 8 (38%) 5 (24%) 21
30
M. E1-Kallinyet al.: SurgicalApproachesto ThoracicDisc Herniations
spastic gait, the correct clinical diagnosis should be made in the majority of patients. This underscores the importance of choosing the optimal surgical approach that minimizes root and cord manipulation and maximizes favorable results. Choosing the optimal approach in thoracic disc herniation depends to a large extent upon the training and experience of the individual neurosurgeon, as well as the general medical condition of the patient. Patients in poor general condition should not undergo a lengthy and formidable operation. The patient in our series who developed a postoperative stroke probably did not tolerate a period of hypotension during a transthoracic approach. A number of other factors, however, must also be considered when determining which of the three operative techniques to employ 3l. These factors are summarized in Table 3. The location and size of the herniated portion of the thoracic disc as determined by MRI or postmyelography CT are of utmost importance. Lateral herniations are best managed using the transpediculartransfacetal approach. The transthoracic-transpleural approach, however, is most effective for central herniations. Centrolateral herniations can be repaired using the posterolateral-extrapleural approach. In addition, the level of the herniation should be a major consideration. At the extremes of the thoracic spine from T2-T4 and from T10-T12, a thoracic disc can only be reached with great difficulty using the transthoracic approach. Moreover, the scapular girdle blocks lateral access from T2-T4 making the costotransversectomy also very difficult in this region. Consequently, we recommend the transpedicular approach from T2-T4. In fact, we used this approach in one case in our series of multiple high thoracic disc herniations.
Table 3. Important Factors in Choosing a Surgical Approach 1. Trainingand experienceof surgeon 2. Generalmedicalconditionof patient 3, Locationof disc (central, lateral, or centrolateral) 4. Sizeof disc herniation 5. Levelof disc herniation 6. Multiplicityof disc herniation 7. Migrationof disc fragment(upwards or downwards) 8. Associatedspinaldiseases(thoracicstenosis,Scheuermann'sdisease) 9. Consistencyof disc (hard, soft, or calcified) 10. Locationof artery of Adamkiewicz 11. Intraduralrupture of disc
The posterolateral and transpedicular approaches are good options from T10-L1 which is the region most commonly affected by thoracic disc herniation. C7-T1 herniations can be regarded as lower cervical disease and can be managed using the standard anterior cervical discectomy. Between T4 and T10, the level of herniation is not as important a factor, and the location and size of the herniation should be given greater weight. Migration of a disc fragment upwards or downwards necessitates a more anterior approach in which part of the vertebral body must be removed in order to retrieve the free fragment. The anterior approach is also indicated in patients with Scheuermann's disease to correct both the kyphotic deformity and the disc herniation. We used this strategy in our series in a patient with Scheuermann's disease 35, 36. Because a corpectomy is performed with this procedure, a fusion is needed followed by an extended period of bracing and bed rest. Fusion is not necessary following the standard transthoracic and other two approaches because the limited amount of bone resection does not affect the stability of the spine. Calcified central discs should also be managed using the transthoracic-transpleural approach. An anterior approach should be used under ,these circumstances because access to the anterior and anterolateral regions of the spinal canal is more direct than with a posterolateral approach. We used an anterior approach in two patients with calcified central herniations. When the calcified herniations were more centrolateral in location, costotransversectomy can be performed, as we did in two patients in our series. These calcified discs should be drilled until a very thin shell remains before being delivered out. The transthoracic approach should be done from the right side to avoid injury of the artery of Adamkiewicz. Also, the right-sided approach allows a more adequate exposure. Moreover, extreme care should be exercised when working near the intervertebral foramina at these levels, especially on the left, when a transpedicular or posterolateral approach is employed. We found that intradural penetration of a disc fragment necessitates the use of a transpedicular approach followed by a laminectomy. In such a case, the herniated disc is first removed extradurally. Following this, the dura is opened posteriorly and residual penetrated fragment is excised 31. Finally, if any canal stenosis is present in addition to the disc herniation, the posterior approach offers the most advantage overall. Through a laminectomy,
M. E1-Kallinyet al.: Surgical Approaches to Thoracic Disc Herniations combined with drilling unilaterally the facetal joint with the pedicle, the disc can be removed and the spinal cord decompressed during the same operation 3. Conservative treatment still has a place in the management of patients with mild cord compression. It is now recognized, largely because of the use of M R I , that a minimal amount of compression is often welltolerated and that immediate surgical therapy is not indicated. In addition, M R I can be used in conjunction with conservative therapy to monitor any changes in the amount of compression over time and to determine when surgery is advisable. There has been marked improvement in the results of surgery of thoracic disc herniations after abandonment of decompressive laminectomy with intradural and/or extradural removal of disc herniation. O f 119 cases involving laminectomy reviewed by Arce et al., 28% were made worse and 11% remained unchanged. By contrast, less than 5% of our patients were made worse after surgery while 14% were unchanged. This lack of improvement in our series is best explained by a relatively long period of spinal cord compression prior to surgery. Moreover, our overall improvement rate of 81% was similar to a series reported by Sekhar et al., in which 10 out of 12 patients (83%) were cured or improved after using more anterior approaches for cord or root compression. Our improvement rate of 87.5% (7 out of 8 patients) using the transpedicular approach again is similar to the results of a series reported by Arce et al., in which 82% of patients that were reviewed, twenty-seven patients were improved or made asymptomatic. In this same series, 11% remained unchanged and 7% were made worse. No patient in our series undergoing a transpedicular approach was made worse, and 12.5% remained unchanged. O f five cases operated on using the costotransversectomy approach, four (80%) were cured or improved and one patient (20%) was unchanged. This is similar to the series of 43 cases collected from the literature by Arce et al., in which 88% were improved or made asymptomatic and 12% remained unchanged 1, 31 All 12 cases collected from the literature in which the transthoracic approach was used were improved or made asymptomatic. N o patient was unchanged or worse after this approach. In our series six patients were improved or cured. One patient was unchanged and one patient was made worse due to manipulating compressed spinal cord. The changes of successful treatment in thoracic disc
31 herniations depend on the preoperative neurologic status. With the use of M R I in diagnosis, we will be better able to operate on patients with mild preoperative neurologic deficits. In addition, further refinement of microsurgical technique will help to achieve favorable results. I n s u m m a r y , it is now possible to diagnose thoracic disc herniations during the early stages of nerve root irritation and mild spinal cord compression. While nonsurgical therapy can still be used in the initial treatment of the disease, m a n y patients will eventually require surgery. Determining which of the surgical approaches is most appropriate entails considering the a n a t o m y of the herniation as seen by M R I and/or CT, the ability of the patient to undergo a major operation, the presence or absence of coexisting spinal diseases such as thoracic stenosis or Scheuermann's disease, and the surgeon's level of expertise. By taking such a comprehensive approach, one can expect gratifying surgical results with a minimum of postoperative complications.
Acknowledgement The authors wish to thank Janet C. Witzleben for editorial support and Glorya Lang O'Conner for administrative support.
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