Original Paper
Pcdiatr Neurosurg 1992:18:272 281
Arnold //. Menezes Division of Neurosurgery, University of Iowa Hospitals. Iowa City. Iowa, USA
The Anterior Midline Approach to the Craniocervical Region in Children
Arnold H. Mcnc/cs. MD Division of Neurosurgery University of Iowa Hospitals Iowa City. IA 52242 (USA)
* 1992 S. Karger AG, Basel 1016 2291/92/0186 0272 S2.75/0
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The first anatomical descriptions of craniocervical junc limits of the lesion must be available to the surgeon prior tion abnormalities were reported in the early part of the to embarking on treatment [23], Thus the factors influenc 19th century. These autopsy examinations stimulated clin ing specific treatment would be determined by plain radio ical interest, but confirmation of the diagnosis was lacking graphs. pleuridirectional tomography of the craniocervical until postmortem examination. With the advent of radio- area to include cerebral spinal fluid enhancement with graphic studies in the earlier part of the 20th century, iohexol and magnetic resonance imaging (MRI) [32], The craniocervical region abnormalities, as well as trauma to effects of traction would then also have to be documented this region, took new meaning. The postmortem reports both with MRI and pleuridirectional tomography. Each of were replaced by clinical and radiographic studies of ab these techniques has important features and provides com normalities. Advances in neurodiagnostic imaging and plimentary information about the craniocervical region microsurgical instrumentation have so increased our neu and the presence of any incidental and pathological rosurgical armamentarium that whole new vistas are now changes in the normal and abnormal relationships [27]. In within our reach. The skull base and craniocervical junc selected cases. CT myelography is essential to identify and tion is one such area. Until the early 1970s, lesions that locate the abnormality in relationship to the subarachnoid were placed anterior to the craniocervical region were space, and its proximity to the vertebral basilar vascular approached via a posterior decompression or a posterolat system. This may especially be important in children eral route. At times a fusion was performed in association whose symptomatology exacerbates with head motion. with this. The mortality and morbidity for such ventrally situated lesions were inordinately high. However, in the Approaches to the Anterior Craniocervical Junction past 15-18 years, several approaches to the anterior cran iocervical junction have been utilized with good results. The anterior approaches to the craniocervical junction Perhaps the most interesting feature of the pathology in the region of the craniocervical junction is its diverse are divided into the median, the anterolateral, and the presentation. Compromise of the cervicomedullary junc lateral approaches. Table 1 enumerates the various ante tion results in a multiplicity of symptoms and signs that rior approaches to the craniocervical region. may be indicated by brain stem and cervical myelopathy, The Median Approaches cranial nerve and cervical root dysfunction, and by alter The transphenoidal and transethmoidal approaches are ations of the vascular supply to these structures [25], Pathology in children is more often than not congenital limited to the anterior midline at the sella turcica and the and developmental in origin. However, tumors of the high upper clivus [27]. However, a transethmoidal approach nasopharynx, chordomas, rhabdomyosarcomas and bony has a larger field of vision allowing the surgeon to expose tumors also join the histopathology in this region in the 1.5-2 cm to either side of the midline below the region of pediatric age group. A precise definition of the pathologi the sella turcica. This is not feasible in poorly pneumatized cal anatomy, biomechanics of the bony lesions, and the sphenoid sinuses or with narrowed nasal passages [6],
The Transoral-Transpalatal-Pharyngeal Approach The transoral-transpalatal-pharyngeal approach to the craniocervical junction provides a safe, effective, and rapid exposure of the median 4 cm of the craniocervical junction from the midclivus to the C2-C3 interspace (fig. I) [24], Further inferior access may be gained by median labial mandibular glossotomy. The rostral extent of this expo sure is enhanced by resection of the hard palate, and at times palatal flaps with lateral dissection of the soft palate, thus allowing resection of the nasal septum and the vomer [26, 27], The author has found this technique useful in obtaining resection up to the posterior aspect of the
Fig. 1. Illustration of the extent of exposure via the transpalalopharyngeal approach.
Table 1. Anterior approaches to the craniocervical junction
I.
Median a ) Transoral-transpalato-pharyngeal b) Median mandibular split with midline or lateral glossotomy c) Le Fort I maxillary 'Down-fracture' osteotomy d) Lateral rhinotomy (a is frequently combined with b. c. and d) e) Transphenoidal f) Transethmoidal II. Anterolateral Transcervical extrapharyngeal III. Infratemporal fossa iranszygomalie Pre- or postauricular
sphenoid sinus and the dorsum sellae. An option is a lateral rhinotomy combined with a transoral, transpharyngeal approach. The main indication for the transoral-transpalatal-pharyngeal operation is irreducible ventral pathology com pressing the ccrvicomeduilary junction. This may be osseous, neoplastic, or inflammatory [26], This approach has been used for removal of chordomas and other bony tumors. However, we feel that the best approach for intradural pathology, such as meningiomas and schwan nomas. is via a posterolateral route since these lesions reside within the subarachnoid space. Should this not be possible, a ventral operative approach may be essential. Midline vertebral basilar artery aneurysms have been
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Similarly, a lateral rhinotomy is not favored in children because of the narrow tunnelled field of vision and its restriction in tackling lesions below the foramen magnum [21.27.30]. Thus the mainstay of most anterior ap proaches is the transoral approach through the soft plate, if needed, and through the pharynx [1,3. 5. 8. 12. 15,20. 23. 29]. Lesions that are situated high up in the pharynx and in the sphenoid region can be approached strictly via a transpalatine approach through the hard palate retract ing the soft palate further caudally [26]. A mandibular split allows for a greater field of exposure in the rostralcaudal dimension and is usually not necessary in children [1. 6. 28]. Transoral-transpalatal-pharyngeal approach can be combined with the median labiomandibular split or a Le Fort I maxillary down fracture to provide the exposure necessary [2. 13, 17,34]. In the author’s hands, this has been the mainstay of the anterior approach to the cranio cervical junction and will be described in further detail below. The anterolateral-transcervical extrapharyngeal ap proach to the upper cervical spine has been described by several authors [4. 11, 18, 19.22, 33,35], This approach provides anterior access to the neural elements from the clivus to the lower cervical vertebrae without entering into the oral cavity and allows for a ventral fusion procedure. The disadvantages are the high risk of injury to the hypoglossal and glossopharyngeal nerves, and the inability to properly visualize the ipsilateral clivus and craniocervi cal border. The lateral infratemporal fossa-transzygomatic ap proach may be made in the preauricular or retroauricular fashion [9 II, 27, 31]. The facial nerve may have to be re routed here and again the procedure should only be called for in tumors such as angiofibromas, rhabdomyosarcomas and malignant neurofibromas encountered in the pediatric population.
Preoperative Assessment
The nutritional status of symptomatic patients must be evaluated. The achievement of a high caloric intake can only be feasible in some individuals via nasogastric feeding or supplemental intravenous hyperalimentation. This is especially important since no oral intake is permitted during the first week after operation. In some children, the ability to sufficiently open the mouth is extremely limited. A working distance of 2.5 3 cm between the upper and lower incisor teeth is neces sary. If this is not possible, an alternative route must be utilized. Preoperative oral pharyngeal cultures are obtained 2-3 days prior to the surgical procedure. If no pathological flora are identified, no antibiotics are utilized. The pulmonary status must be assessed prior to transo ral operative procedure since respiratory dysfunction is one of the main symptoms caused by pathology in this area. Should the lower cranial nerves be comprised, it is imperative that the swallowing mechanism be properly assessed. In the event that this is compromised, a tra cheostomy will be essential at the time of transoral opera tion. Operative Procedure A mild sedation is essential in children prior to being brought to the operating theater. The MRI-compatible halo should have already been placed with 5-7 lb of skeletal traction applied. An awake fiberoptic oral endo tracheal intubation is made after which the patient is repositioned and examined awake to make sure there is no change in neurological status from positioning. This may not be feasible in young children and the operative proce dure must be carried out without awakening the child. Somatosensory-evoked responses using the median nerve may be of assistance during this time if the child is not to be woken up. A nasotracheal intubation is to be avoided as this will disrupt the integrity of the high oral pharyn geal mucosa since this is the avenue of approach to the craniocervical junction lesions. More importantly, trauma to the adenoid tissue will result in troublesome bleeding which will require resection and denude the mucosa from in front of the clivus. This should be avoided.
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The child is then positioned supine on the operating table with the head resting on a padded Mayfield horse shoe head holder. Traction is maintained during the oper ation with mild extension of the neck. Once it is established that no neurological deficit has occurred, gen eral endotracheal and intravenous anesthesia ensues. A tracheostomy is performed only when the operation involves the high nasopharynx and the craniocervical junc tion. In those instances when the procedure is carried out in the upper cervical spine, a tracheostomy is not neces sary. In this latter situation, the soft palate is elevated using sutures attached to rubber tubing and pulled up through the nostrils. Following the intubation or tra cheostomy, a pharyngeal throat pack is placed to occlude the laryngopharynx and to prevent secretions and blood from draining into the stomach. Custom-built dental guards are now placed over the upper and lower dentition. This is especially important in the pediatric population so as to avoid injury to the alveolar ridges. The oral cavity is then cleansed with 10% povidone-iodine and subse quently hydrogen peroxide and rinsed with saline. A midline incision is made in the soft palate extending from the hard palate to the base of the uvula and deviat ing to one side. The operating microscope provides for magnification and an illuminated light source. Stay sutures are applied to the soft palate, retracting the palatal flaps to either side, exposing the high posterior nasopharynx down to the C2-C3 interspace. In young children, this exposure may be compromised by enlarged tonsils. A tonsillectomy may be necessary prior to this operative procedure. The posterior pharyngeal wall is anesthetized with topical 2.5% cocaine and the median raphe infiltrated with 0.5% xylocaine solution with 1/200,000 epinephrine. A median inci sion is next made into the posterior pharyngeal median raphe with an upward extension of this incision providing exposure from the midhalf of the clivus down to the lower border of the C2 vertebra. The prevertebral fascia and longus colli muscles are dissected from their osseous-liga mentous attachment to expose the axis vertebra, the atlas and the clivus (fig. 2a). The anterior longitudinal ligament and the occipital ligaments are dissected olf the anterior tubercle of the anterior arch of the atlas, the clivus, and the anterior surface of the axis. This exposure allows a width of about 3.5 cm in the older child. However, below the age of 8 years, this exposure is limited to about 2.5 cm. Further lateral exposure is inadvisable because of risks of destroying the eustachian tube orifices, injuring the hy poglossal nerve, and entering the vertebral canal and damaging the vertebral artery.
The Anterior Midline Approach to the Craniocervical Region in Children
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clipped via this route with exposure through the clivus when no other avenue was feasible [7, 14]. Even though there appears to be host immunity to the oral pharyngeal flora, the strongest indication for an anterior transoral midline procedure is an extradural lesion.
a
Fig. 2. a Operative exposure viewed through the microscope. The divided soft palate is held apart by stay sutures. The clivus (Cl), anterior atlas arch (C,) and axis body (C ,) are seen, b The posterior shell of odontoid process is separated from the periosteum with an angled curette, c The odontoid process and pannus have been removed. The tectorial membrane (white arrow) is vertically divided and bulging dura (x) seen. Note the component of the curicate ligament (cr).
a pulsatile dura protruding into the decompression site. The transverse ligament of the cruciate complex does not need to be resected unless tumor is encountered or the cruciate ligament has been destroyed by pathology. In circumstances where the occipital condyle is free or the lateral atlantal mass causes paramedian invagination, the resection must be carried laterally and can proceed to beyond the equator of foramen magnum. In such situa tions. a complete knowledge of the abnormal location of the vertebral artery is essential from the preoperative studies. Abnormal bony protrusions from the clivus, such as remnants of proatlas or a third occipital condyle, require careful and tedious dissection of the clival dura away from the osseous pathology. Median nerve sensory-evoked responses are utilized during the operation to record the brain stem latencies [36. 37], This becomes superfluous in patients with severe cervicomedullary compression because the brain stem la
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It is natural that exposure of the odontoid region can only be obtained by removal of the anterior arch of the atlas. Unfortunately some authors feel that this is not necessary and proceed with a blind removal [3, 12]. The anterior arch of the atlas is removed with the high speed drill, as is the caudal clivus. The soft tissues anterior to the odontoid process are removed. More often than not, this represents granulation tissue with chronic instability. The odontoid process is resected in a rostral-caudal di mension. This is facilitated using a diamond burr attach ment and fine Kerrison rongeurs and curettes (fig. 2b). The pannus now encountered must be resected. Divi sion of the odontoid process and downward traction ad vocated by some in fraught with difficulty and endangers the patient [3. 12]. This is especially so if the pannus is tough and the odontoid has achieved a subarachnoid location. After removal of the tectorial membrane, the surgeon is assured of adequate bony decompression with
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The Anterior Midline Approach to the Craniocervical Region in Children
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tencies are usually not elicitable. In less compressive cir permitted only after 7 days, at which point a clear liquid cumstances, this parameter may assist the surgeon in intake is allowed and a full liquid diet is permitted at the judicious handling of tissues and minimizing compression end of a fortnight. A soft pureed diet may be started at the of neural structures, should the latencies change during the end of 3 weeks. In the event that the dura was opened, intravenous operative procedure. In situations where an intradural lesion is encountered, antibiotics (cefotaxime, flagyl, and methicillin) and spinal a midline incision of the ventral dura must be made drainage is maintained for 10 days after the operation. starting interiorly and proceeding in a rostral direction. The tracheostomy is discontinued only if a stabilization The dura is opened with a cruciate incision converting the procedure is not required. Should a tracheostomy not vertical incision to a cruciform one below the foramen have been made, the endotracheal tube is removed at the magnum, thus avoiding the circular sinus. Resection of an end of 48 h or when the lingual swelling has receded. intradural lesion requires relieving the CSF turgidity by having previously placed a lumbar subarachnoid drain. The Evaluation of Postoperative Stability Once the intradural operation is completed, it is essential to bring the dural leaves together in as watertight a closure as possible. In a situation where the dura has been vio Pleuridirectional tomography of the craniocervical lated. it is important to harvest external oblique aponeuro junction is obtained I week after the transoral operation, sis for fascia to be layed against the dural closure. This to determine the craniocervical junction stability. This is should be reinforced with a fat pad and held in position by done in the flexed and extended positions to determine and anteroposterior stability, as well as with and without plasma glue. The longus colli muscles, as well as the constrictor traction, assessing the vertical stability. An offset at the muscles of the pharynx and the posterior pharyngeal lateral occipitoatlanto-axial articulation, during the flexed mucosa are closed in individual layers using interrupted and extended studies, or excessive vertical displacement of sutures of polyglycolic. In the event that the opening in the craniospinal axis is indicative of instability. MRI is the clivus is large, a pharyngeal pack may be utilized for likewise performed at this time to assess the extent of compression of the high nasopharynx with traction tubes decompression. Should instability be present, an occipito brought out through the nostrils. At this juncture, a soft cervical fixation is mandatory and this should be done feeding tube is passed via the nostrils into the nasophar from a dorsal approach. Of the 188 patients who underwent transoral operation ynx and guided, under direct vision, into the esophagus and placed into the stomach. This is done after the throat in the author’s experience, 74 were children (table 2). One pack is removed. The position of the feeding tube in the hundred and fifty-eight individuals demonstrated postop stomach is confirmed by installation of air into the tube erative instability at the craniocervical junction (66 chil and confirmation by the anesthesiologist auscultating over dren) and these required a posterior occipitocervical the abdomen. This tube must be anchored to the skin at fixation. Children who have undergone a dorsal fixation the base of the nasal septum. The nasal mucosa of the soft are ambulated in a halo vest. This usually necessitates 4 -6 palate is approximated with simple interrupted sutures as months of craniocervical immobilization. is the muscular layer. It is advisable to use vertical mat Dorsal fixation is usually necessary after transoral tress sutures to bring the oral mucosa together, incorpo clivus odontoid complex resections in congenital and de rating the muscular layer also. This prevents dehiscence. velopmental abnormalities associated with atlas assimila In situations where surgery is necessary through the tion and/or segmentation failures of the second and third clivus, or in patients with a foreshortened clivus and cervical vertebrae. It was also dictated in the child with platybasia, the hard palate is exposed and the posterior Down’s syndrome. 1 cm is resected. This allows a high nasopharyngeal expo sure without splitting the mandible or doing a median glossotomy. In such instances the nasal septum and vomer Results may be resected. The patient is maintained in 5-7 lb of skeletal traction Neurological improvement was seen in all patients. after operation, especially in unstable situations. Nasogas Four children who were ventilator dependent prior to the tric feeding is instituted at the end of 24 h. Oral intake is operation, following previous primary posterior fossa de-
Table 2. Summary of surgical treatment at the craniocervical junction in 558 patients (1977-1990)
Stability
Compression
Approach
Postoperative Stability
Immobilization 36 (30)
A. Reducible 268 (89)
Posterior Fusion 232 (59)
Stable 30 (8) "Ventral 188 (74)
Anterior
1
.Unstable 158 (66)
B. Irreducible 290 ( 122)
Stable 36 ( 16) Dorsal L102 (48)
Posterior
1
.Unstable 66 (32)
158 (66)
36 (16)
66 ( 32)
Number of children in parentheses.
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Table 3. Pathology encountered at the ventral craniocervical compressions or trauma, had resolution of their neurolog ical symptoms and signs. Downbeat nystagmus, brain junction in 74 children using the transoral-transpalato-pharyngcal stem dysfunction with cranial nerve palsies and sleep approach apnea were prominent in children with basilar invagina Basilar invagination tion with an associated Chiari malformation. These signs Primary anterior 30 Anterior + paramedian 23 regressed following the ventral procedure. An intradural pathology was present in 24 individuals (Chiara malformation 22/63) Dystopic os odontoideum. with invaginating axis 7 of the 188 adults and children who underwent this opera 2 Osteoblastoma Cl tion. There was no episode of meningitis and in no in Down's syndrome, with fixed cranial settling 1 stance was a septomucoperiosteal flap or pharyngeal flap Clivus chordoma 1 needed for closure of the posterior pharyngeal wall or the 74 dura. Lumboperitoneal CSF shunting was never rquired. Total as in some other series. In regards to the children alone, a pharyngeal wound dehiscence occurred in 2 individuals. In the first, a Two adults died within the first month after operation. Yankauer suction was inappropriately handled by the patient reopening the pharyngeal wound at the end of 10 An elderly male with rheumatoid arthritis and cranial days. In another individual, a retropharyngeal infection settling succumbed to a myocardial infarction 4 weeks was present caused by bacteroides. This was treated with after his dorsal fixation operation. Another 52-year-old intravenous antibiotics and allowing drainage into the woman, admitted quadriplegic after a motor vehicle acci pharynx. Intravenous hyperalimentation was necessary for dent on a ventilator, was transferred to our institution with severe pontomedullary dysfunction. She underwent 2 weeks after which the dorsal fixation was then made. Three children were subsequently evaluated for velo- emergent transoral decompression of the severe basilar palatine incompetence. This particular problem is seen in invagination and paramedian compression of the medulla. young individuals and usually 3 -6 months after transoral She achieved normal respiratary function within a week operation where the palate may have been split. It is felt and was off the ventilator. She succumbed to sepsis of that this is secondary to fibrosis that takes place in the soft urinary tract origin which existed at the time of her palate or the pharyngeal wall. Endoscopy identified the admission. The pathology encountered in 74 children is repre cause. Pharyngeal retraining in 2 individuals and an obtu sented in table 3. rator in the third individual circumvented the problem.
Fig. 3. a Midsagittal Tl-weighted VIRI of head and neck of case VI.H. made 3 months alter posterior fossa craniectomy and Cl decompressive laminectomy. Note the abnormal clivus-odontoid angle with severe ventral medulla compression and the hind brain herniation into the cervical canal, b Axial Tl-weighted MRI at the Cl level (case M.B.). The medulla oblongata (m) is ventrally compressed by the pannus and odontoid (white arrow). Note the medially approximated cerebellar tonsils, c Composite of preoperative CCJ tomograms in case MB. The inferior clivus articulates with the anterior atlas arch and the odontoid. The lateral atlantal masses are assimilated to the occiput (frontal tomogram), d Midsagittal Tl-weighted MRI of CCJ made after ventral transoral decompression. The bony compression of C’l-odontoid has been removed and good medullary decompression achieved, e Composite of postoperative CCJ tomograms made after the transoral resection in case M B. Note the resected anterior arch of atlas and the odontoid process. There is lateral Cl-C'2 instability seen on the frontal tomogram.
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Chiari malformation with basilar invagination. He underwent poste rior fossa and upper cervical spine decompression. Shortly after this operative procedure, his headaches worsened and paresthesias in the left arm set in. At the time of our evaluation at the University of Iowa Hospitals and Clinics, the main abnormalities were bilateral internuclear oph thalmoplegia. mild spastic quadriparesis with weakness in the arms more than the legs, and a spastic ataxic gait.
The Anterior Midlinc Approach to the Craniocervical Region in Children
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Case Studies (1) M.B.: This 16-year-old male presented with severe occipital and vertex headaches, ataxic gait and left arm paresthesias. At the age of 13 years, he had horizontal diplopia and subsequently under went surgery on his right eye for strabismus. This worsened his visual difficulties. He then had a similar operative procedure for strabismus on his left eye. At age 16 years his headaches worsened and the diplopia progressed. He was evaluated with MRI. This revealed a
Fig. 4. a C ase A .M Composite of midsagittal T lweighted MR1 of the CCJ in the flexed (L) and extended ( R) positions. There is assimilation of the atlas, herniation of cerebellar tonsils into the spinal canal and syringohydromyelia. Ventral cervicomedullary compression is only partially reducible in the extended position, b Axial TI-weighted MR I of case A.M. at the foramen magnum. The medulla (m) is indented ventrally by the bony mass (arrow) and dorsally compressed by the herniated cerebellar tonsils.
procedure. He recovered neurological function. MRI done just after the ventral decompression revealed resolution of the syringohy dromyelia. as well as the bony compression.
Discussion
The transoral approach to the posterior pharyngeal wall has been an operation used for drainage of retropha ryngeal abscesses for many years. Although this route provides direct access to the craniovertebral junction, it has not gained its well-deserved place in the neurosurgical armamentarium. The reasons for this have been attributed to initial reports of infection, limited exposure, unaccept able patient morbidity and mortality and cerebral spinal fluid leakage. We feel that this series has shown that the ventral transoral-transpharyngeal approach to the lower clivus and upper cervical spine is safe, rapid, and effective. It is important in relieving ventral irreducible pathology of the craniovertebral junction.
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MRI revealed basilar invagination by an abnormal clivus-odon toid Cl complex (fig. 3a. b). There was atlas assimilation present (fig. 3c). The medulla was markedly indented by the ventral bony abnor mality. The cerebellum appeared to be slumped into the posterior fossa defect and also into the upper cervical canal. Marked compres sion of the medulla oblongata was evident, caused by chronic granu lation tissue and the osseous pathology. Transoral procedure was performed for ventral decompression of the medulla. Postoperative MRI showed marked improvement in the ventral bony angulation with relief of medullary compression (fig. 3d). An offset in the anterior relationships of the assimilated atlas and the lateral C2 masses was evident on the subsequent tomograms ( fig. 3e). He required an occipitocervical fixation and is now asymptomatic. (2) A.M.: This is a 9-year-old male who became symptomatic when struck on the football field. He experienced neck pain and subsequently noticed drooping of his right eyelid, clumsiness with his right arm and right leg. and was noted to have a Horner's pupil. MRI revealed a partially reducible basilar invagination with atlas assimilation (fig. 4a). A Chiari I malformation was evident with syringohydromyelia. Severe ventral bony compression of the medulla was visualized on the axial Tl images (fig. 4b). A transoral decom pression was performed followed by a dorsal occipitocervical fixa tion. A duraplasty was made at the time of the dorsal occipitocervical
The advantages of the transoral-transpalatine approaeh to the craniocervical region, compared to other operative approaches in irreducible pathology include: (1) the im pinging bony and granulation pathology that accompanies chronic instability is accessible via the ventral route. (2) The child is placed in the extended position as opposed to the flexed position, thus decreasing the angulation of the brain stem during surgery. (3) Surgery is performed through the avascular median raphe and through the clivus. The indications for the transoral operation at the ante rior craniocervical border must be exact. A precise defini tion of pathology usually requires more than one radiological procedure. Mere identification of ventral pathology without attempts at reduction are no grounds for the operative procedure. The primary approach to intra-arachnoid lesions at foramen magnum should not be by the transoral route unless other approaches prove ineffective. The extent of surgical exposure of the anterior cranio cervical junction in the transoral approach is limited by the emergence of the hypoglossal nerves 2 cm lateral to the middle of the clivus, by the vertebral arteries and by the eustachian tubes lying just below the base of the skull. However, these structures allow at least 3.5 cm of expo sure which is certainly sufficient for removal of pathology from the lower half of the clivus down to the C2-C3 interspace.
A Chiari malformation was identified in 48 patients who underwent a transoral operation. Several of these individu als had undergone a primary operation consisting of a posterior fossa and upper cervical canal decompression. Rapid deterioration ensued in these patients, or an initial improvement was followed by progressive deterioration in neurological function. In each of these instances the MRI showed an increase in the ventral cervicomedullary junction compression and angulation secondary to the ‘peg-like' basilar invagination. More importantly, a slump of the cerebellum into the newly created posterior decompression worsened the situation and caused further impaction. One wonders whether this was the cause of the syringohydromyelia occurring as a result of the changes in the craniospinal dynamics. The improvement after ventral de compression can be attributed to relief of brain stem angulation, improved blood supply, or changes in the cerebral spinal fluid pressure dynamics. The basic transoral approach has been used for clipping of midline aneurysms of the vertebral basilar system. Disadvantages of this operation include accommodating the length of the aneursym clips in the exposure and the difficulty in obtaining dural approximation over the ven tral aspect of the brain stem. The anterior midline approach to the craniocervical region in children is best served via the transoral route which is safe, rapid, and efficacious in providing decom pression of the cervicomedullary region.
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The Anterior Midline Approach to the Craniocervical Region in Children
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1 Arbil E. Patterson RH: Combined transoral and median labiomandibular glossotomy ap proach to the upper cervical spine. Neuro surgery 1981:8:672 674. 2 Archer DJ. Young S. Utlley D: Basilar aneu rysms: A new transclivai approach via maxillotomy. .1 Ncurosurg 1987:67:54 58. 3 Corckard HA. Pozo JL. Ransford AO. Stevens JM. Kendall BE. Essigman WK: Transoral decompression and posterior fusion for rheumatoid atlanto-axial subluxation. J Bone Joint Surg (Br) 1986;68:350-356. 4 DcAndradeJR. MacNab I: Anterior occipito cervical fusion using an extrapharyngcal expo sure. J Bone Joint Surg (Am) 1969:51:1621 1626. 5 Delgado TE. Buckhert WA: Surgical manage ment of tumors in and around the clivus via the transoral approach. Conlemp Ncurosurg 1983:4:1 6.
24 Mcnezcs AH. VanGilder JC: Transoral transpharyngeal approach to the anterior craniocervical junction. 10-year experience with 72 patients. J Ncurosurg 1988:69:895903. 25 Mcnezcs AH. VanGilder JC: Abnormalities of the craniovertebral junction: in Youmans J (ed): Neurological Surgery, ed 3. Philadelphia. Saunders. 1990: pp 1359 1420. 26 Mcnezcs AH: Transoral approach to the clivus and upper cervical spine: in Wilkins R. and Rengachary S (eds): Neurosurgery Update. New York. McGraw-Hill. 1990. chapt 32. pp 306 313. 27 Mcnezcs AH: Anterior approaches to the craniocervical junction: in Clinical Neuro surgery. Proceedings of the Congress of Neu rological Surgeons. New York. Williams & Wilkins. 1991, vol 37. pp 756 769. 28 Moore LJ. Schwartz HC: Median labiomandibular glossotomy for access to the cervi cal spine. J Oral Maxillofac Surg 1985:43:909 912. 29 Pastzor E. Vajada J. PilTko P. ct al: Transoral surgery for craniocervical space-occupying processes. J Ncurosurg 1984;60:276 -281. 30 Robin PE. Powell DJ: Treatment of carcinoma of the nasal cavity and paranasal sinuses. Clin Otolaryngol 1981:6:401 414.
31 Sekhar l.N. Schramm VL Jr. Jones NF: Sub temporal prcauricular infratemporal fossa ap proach to large lateral and posterior cranial base neoplasms. J Ncurosurg 1987:67:488 499. 32 Smoker WRK. Keyes WK. Dunn VD. Mcnezcs All: MRI versus conventional radi ology examinations in the evaluation of the craniovertebral and cervicomedullary junction. Radiographics 1986:6:954 994. 33 Stevenson GC. Stoney RJ. Perkins RK. Adams JE: A transccrvical transclival ap proach to the ventral surface of the brain stem for removal of a clivus chordoma. J Ncurosurg 1966:25:544 551. 34 Utlley D, Moore A. Archer DJ: Surgical man agement of midline skull base tumors: A new approach. J Ncurosurg 1989:71:705-710. 35 Whitesides TE Jr: Lateral retropharyngeal ap proach to the upper cervical spine: in The Cervical Spine. The Cervical Spine Research Society. Philadelphia. Lippincott. 1983. pp 517-527. 36 Yaniada T. Ishida T. Kudo Y. ct al: Clinical correlates of abnormal PI4 in median SEPs. Neurology 1986:36:765 771. 37 Yamaura A. Makino H. Isobe K, Takashima T. Nakamura T. Takcmiya S: Repair of cere brospinal fluid fistula following transoral tran sclival approach to a basilar aneurysm. Technical note. J Ncurosurg 1979:50:834 - 836.
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17 Krcspi YP: Transmandibular exposure of ihe skull base. Abslr Ini Symp on Cranial Base Surgery. Pittsburgh. Sept 1988. 18 Lesoin F, Jomin M. Pcllcrin P. Privo JP. Carini S, Servato R: Transclivai transcervical approach to the upper cervical spine and clivus. Acta Ncuroehir (Wien) 1986:80:100 104. 19 Lesoin F. Peilerin P. Thomas C. et al: Acrylic reconstruction of an arthritic cervical spine using the Iransccrvical-lransclival approach. Surg Neurol. 1989;22:329-334. 20 Litvak J. Sumners TC. Barron JL. Fisher LS: A successful approach to vertebrobasilar aneu rysms. Technical note. J Ncurosurg 1981:55: 491 -494. 21 Malis LI: Surgical resection of tumors of the skull base: in Wilkins RH. Rengachary SS (eds): Neurosurgery. New York. McGrawHill. 1985. pp 1010- 1021. 22 McAfee PC. Bohlman HH. Riley LH. Robinson RA. Southwick WO. Nachlas NF.: The anterior retropharyngeal approach to the upper part of the cervical spine. J Bone Joint Surg (Am) 1969:51: 1621 1626. 23 Mcnezcs AH. VanGilder JC. G raf CJ. Mc Donnell DE: Craniocervical abnormalities: A comprehensive surgical approach. J Ncurosurg 1980;53:444-455.
Pcdiatr Neurosurg 1992:18:272 281
Arnold //. Menezes Division of Neurosurgery, University of Iowa Hospitals. Iowa City. Iowa, USA
The Anterior Midline Approach to the Craniocervical Region in Children
Arnold H. Mcnc/cs. MD Division of Neurosurgery University of Iowa Hospitals Iowa City. IA 52242 (USA)
* 1992 S. Karger AG, Basel 1016 2291/92/0186 0272 S2.75/0
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The first anatomical descriptions of craniocervical junc limits of the lesion must be available to the surgeon prior tion abnormalities were reported in the early part of the to embarking on treatment [23], Thus the factors influenc 19th century. These autopsy examinations stimulated clin ing specific treatment would be determined by plain radio ical interest, but confirmation of the diagnosis was lacking graphs. pleuridirectional tomography of the craniocervical until postmortem examination. With the advent of radio- area to include cerebral spinal fluid enhancement with graphic studies in the earlier part of the 20th century, iohexol and magnetic resonance imaging (MRI) [32], The craniocervical region abnormalities, as well as trauma to effects of traction would then also have to be documented this region, took new meaning. The postmortem reports both with MRI and pleuridirectional tomography. Each of were replaced by clinical and radiographic studies of ab these techniques has important features and provides com normalities. Advances in neurodiagnostic imaging and plimentary information about the craniocervical region microsurgical instrumentation have so increased our neu and the presence of any incidental and pathological rosurgical armamentarium that whole new vistas are now changes in the normal and abnormal relationships [27]. In within our reach. The skull base and craniocervical junc selected cases. CT myelography is essential to identify and tion is one such area. Until the early 1970s, lesions that locate the abnormality in relationship to the subarachnoid were placed anterior to the craniocervical region were space, and its proximity to the vertebral basilar vascular approached via a posterior decompression or a posterolat system. This may especially be important in children eral route. At times a fusion was performed in association whose symptomatology exacerbates with head motion. with this. The mortality and morbidity for such ventrally situated lesions were inordinately high. However, in the Approaches to the Anterior Craniocervical Junction past 15-18 years, several approaches to the anterior cran iocervical junction have been utilized with good results. The anterior approaches to the craniocervical junction Perhaps the most interesting feature of the pathology in the region of the craniocervical junction is its diverse are divided into the median, the anterolateral, and the presentation. Compromise of the cervicomedullary junc lateral approaches. Table 1 enumerates the various ante tion results in a multiplicity of symptoms and signs that rior approaches to the craniocervical region. may be indicated by brain stem and cervical myelopathy, The Median Approaches cranial nerve and cervical root dysfunction, and by alter The transphenoidal and transethmoidal approaches are ations of the vascular supply to these structures [25], Pathology in children is more often than not congenital limited to the anterior midline at the sella turcica and the and developmental in origin. However, tumors of the high upper clivus [27]. However, a transethmoidal approach nasopharynx, chordomas, rhabdomyosarcomas and bony has a larger field of vision allowing the surgeon to expose tumors also join the histopathology in this region in the 1.5-2 cm to either side of the midline below the region of pediatric age group. A precise definition of the pathologi the sella turcica. This is not feasible in poorly pneumatized cal anatomy, biomechanics of the bony lesions, and the sphenoid sinuses or with narrowed nasal passages [6],
The Transoral-Transpalatal-Pharyngeal Approach The transoral-transpalatal-pharyngeal approach to the craniocervical junction provides a safe, effective, and rapid exposure of the median 4 cm of the craniocervical junction from the midclivus to the C2-C3 interspace (fig. I) [24], Further inferior access may be gained by median labial mandibular glossotomy. The rostral extent of this expo sure is enhanced by resection of the hard palate, and at times palatal flaps with lateral dissection of the soft palate, thus allowing resection of the nasal septum and the vomer [26, 27], The author has found this technique useful in obtaining resection up to the posterior aspect of the
Fig. 1. Illustration of the extent of exposure via the transpalalopharyngeal approach.
Table 1. Anterior approaches to the craniocervical junction
I.
Median a ) Transoral-transpalato-pharyngeal b) Median mandibular split with midline or lateral glossotomy c) Le Fort I maxillary 'Down-fracture' osteotomy d) Lateral rhinotomy (a is frequently combined with b. c. and d) e) Transphenoidal f) Transethmoidal II. Anterolateral Transcervical extrapharyngeal III. Infratemporal fossa iranszygomalie Pre- or postauricular
sphenoid sinus and the dorsum sellae. An option is a lateral rhinotomy combined with a transoral, transpharyngeal approach. The main indication for the transoral-transpalatal-pharyngeal operation is irreducible ventral pathology com pressing the ccrvicomeduilary junction. This may be osseous, neoplastic, or inflammatory [26], This approach has been used for removal of chordomas and other bony tumors. However, we feel that the best approach for intradural pathology, such as meningiomas and schwan nomas. is via a posterolateral route since these lesions reside within the subarachnoid space. Should this not be possible, a ventral operative approach may be essential. Midline vertebral basilar artery aneurysms have been
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Similarly, a lateral rhinotomy is not favored in children because of the narrow tunnelled field of vision and its restriction in tackling lesions below the foramen magnum [21.27.30]. Thus the mainstay of most anterior ap proaches is the transoral approach through the soft plate, if needed, and through the pharynx [1,3. 5. 8. 12. 15,20. 23. 29]. Lesions that are situated high up in the pharynx and in the sphenoid region can be approached strictly via a transpalatine approach through the hard palate retract ing the soft palate further caudally [26]. A mandibular split allows for a greater field of exposure in the rostralcaudal dimension and is usually not necessary in children [1. 6. 28]. Transoral-transpalatal-pharyngeal approach can be combined with the median labiomandibular split or a Le Fort I maxillary down fracture to provide the exposure necessary [2. 13, 17,34]. In the author’s hands, this has been the mainstay of the anterior approach to the cranio cervical junction and will be described in further detail below. The anterolateral-transcervical extrapharyngeal ap proach to the upper cervical spine has been described by several authors [4. 11, 18, 19.22, 33,35], This approach provides anterior access to the neural elements from the clivus to the lower cervical vertebrae without entering into the oral cavity and allows for a ventral fusion procedure. The disadvantages are the high risk of injury to the hypoglossal and glossopharyngeal nerves, and the inability to properly visualize the ipsilateral clivus and craniocervi cal border. The lateral infratemporal fossa-transzygomatic ap proach may be made in the preauricular or retroauricular fashion [9 II, 27, 31]. The facial nerve may have to be re routed here and again the procedure should only be called for in tumors such as angiofibromas, rhabdomyosarcomas and malignant neurofibromas encountered in the pediatric population.
Preoperative Assessment
The nutritional status of symptomatic patients must be evaluated. The achievement of a high caloric intake can only be feasible in some individuals via nasogastric feeding or supplemental intravenous hyperalimentation. This is especially important since no oral intake is permitted during the first week after operation. In some children, the ability to sufficiently open the mouth is extremely limited. A working distance of 2.5 3 cm between the upper and lower incisor teeth is neces sary. If this is not possible, an alternative route must be utilized. Preoperative oral pharyngeal cultures are obtained 2-3 days prior to the surgical procedure. If no pathological flora are identified, no antibiotics are utilized. The pulmonary status must be assessed prior to transo ral operative procedure since respiratory dysfunction is one of the main symptoms caused by pathology in this area. Should the lower cranial nerves be comprised, it is imperative that the swallowing mechanism be properly assessed. In the event that this is compromised, a tra cheostomy will be essential at the time of transoral opera tion. Operative Procedure A mild sedation is essential in children prior to being brought to the operating theater. The MRI-compatible halo should have already been placed with 5-7 lb of skeletal traction applied. An awake fiberoptic oral endo tracheal intubation is made after which the patient is repositioned and examined awake to make sure there is no change in neurological status from positioning. This may not be feasible in young children and the operative proce dure must be carried out without awakening the child. Somatosensory-evoked responses using the median nerve may be of assistance during this time if the child is not to be woken up. A nasotracheal intubation is to be avoided as this will disrupt the integrity of the high oral pharyn geal mucosa since this is the avenue of approach to the craniocervical junction lesions. More importantly, trauma to the adenoid tissue will result in troublesome bleeding which will require resection and denude the mucosa from in front of the clivus. This should be avoided.
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The child is then positioned supine on the operating table with the head resting on a padded Mayfield horse shoe head holder. Traction is maintained during the oper ation with mild extension of the neck. Once it is established that no neurological deficit has occurred, gen eral endotracheal and intravenous anesthesia ensues. A tracheostomy is performed only when the operation involves the high nasopharynx and the craniocervical junc tion. In those instances when the procedure is carried out in the upper cervical spine, a tracheostomy is not neces sary. In this latter situation, the soft palate is elevated using sutures attached to rubber tubing and pulled up through the nostrils. Following the intubation or tra cheostomy, a pharyngeal throat pack is placed to occlude the laryngopharynx and to prevent secretions and blood from draining into the stomach. Custom-built dental guards are now placed over the upper and lower dentition. This is especially important in the pediatric population so as to avoid injury to the alveolar ridges. The oral cavity is then cleansed with 10% povidone-iodine and subse quently hydrogen peroxide and rinsed with saline. A midline incision is made in the soft palate extending from the hard palate to the base of the uvula and deviat ing to one side. The operating microscope provides for magnification and an illuminated light source. Stay sutures are applied to the soft palate, retracting the palatal flaps to either side, exposing the high posterior nasopharynx down to the C2-C3 interspace. In young children, this exposure may be compromised by enlarged tonsils. A tonsillectomy may be necessary prior to this operative procedure. The posterior pharyngeal wall is anesthetized with topical 2.5% cocaine and the median raphe infiltrated with 0.5% xylocaine solution with 1/200,000 epinephrine. A median inci sion is next made into the posterior pharyngeal median raphe with an upward extension of this incision providing exposure from the midhalf of the clivus down to the lower border of the C2 vertebra. The prevertebral fascia and longus colli muscles are dissected from their osseous-liga mentous attachment to expose the axis vertebra, the atlas and the clivus (fig. 2a). The anterior longitudinal ligament and the occipital ligaments are dissected olf the anterior tubercle of the anterior arch of the atlas, the clivus, and the anterior surface of the axis. This exposure allows a width of about 3.5 cm in the older child. However, below the age of 8 years, this exposure is limited to about 2.5 cm. Further lateral exposure is inadvisable because of risks of destroying the eustachian tube orifices, injuring the hy poglossal nerve, and entering the vertebral canal and damaging the vertebral artery.
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clipped via this route with exposure through the clivus when no other avenue was feasible [7, 14]. Even though there appears to be host immunity to the oral pharyngeal flora, the strongest indication for an anterior transoral midline procedure is an extradural lesion.
a
Fig. 2. a Operative exposure viewed through the microscope. The divided soft palate is held apart by stay sutures. The clivus (Cl), anterior atlas arch (C,) and axis body (C ,) are seen, b The posterior shell of odontoid process is separated from the periosteum with an angled curette, c The odontoid process and pannus have been removed. The tectorial membrane (white arrow) is vertically divided and bulging dura (x) seen. Note the component of the curicate ligament (cr).
a pulsatile dura protruding into the decompression site. The transverse ligament of the cruciate complex does not need to be resected unless tumor is encountered or the cruciate ligament has been destroyed by pathology. In circumstances where the occipital condyle is free or the lateral atlantal mass causes paramedian invagination, the resection must be carried laterally and can proceed to beyond the equator of foramen magnum. In such situa tions. a complete knowledge of the abnormal location of the vertebral artery is essential from the preoperative studies. Abnormal bony protrusions from the clivus, such as remnants of proatlas or a third occipital condyle, require careful and tedious dissection of the clival dura away from the osseous pathology. Median nerve sensory-evoked responses are utilized during the operation to record the brain stem latencies [36. 37], This becomes superfluous in patients with severe cervicomedullary compression because the brain stem la
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It is natural that exposure of the odontoid region can only be obtained by removal of the anterior arch of the atlas. Unfortunately some authors feel that this is not necessary and proceed with a blind removal [3, 12]. The anterior arch of the atlas is removed with the high speed drill, as is the caudal clivus. The soft tissues anterior to the odontoid process are removed. More often than not, this represents granulation tissue with chronic instability. The odontoid process is resected in a rostral-caudal di mension. This is facilitated using a diamond burr attach ment and fine Kerrison rongeurs and curettes (fig. 2b). The pannus now encountered must be resected. Divi sion of the odontoid process and downward traction ad vocated by some in fraught with difficulty and endangers the patient [3. 12]. This is especially so if the pannus is tough and the odontoid has achieved a subarachnoid location. After removal of the tectorial membrane, the surgeon is assured of adequate bony decompression with
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tencies are usually not elicitable. In less compressive cir permitted only after 7 days, at which point a clear liquid cumstances, this parameter may assist the surgeon in intake is allowed and a full liquid diet is permitted at the judicious handling of tissues and minimizing compression end of a fortnight. A soft pureed diet may be started at the of neural structures, should the latencies change during the end of 3 weeks. In the event that the dura was opened, intravenous operative procedure. In situations where an intradural lesion is encountered, antibiotics (cefotaxime, flagyl, and methicillin) and spinal a midline incision of the ventral dura must be made drainage is maintained for 10 days after the operation. starting interiorly and proceeding in a rostral direction. The tracheostomy is discontinued only if a stabilization The dura is opened with a cruciate incision converting the procedure is not required. Should a tracheostomy not vertical incision to a cruciform one below the foramen have been made, the endotracheal tube is removed at the magnum, thus avoiding the circular sinus. Resection of an end of 48 h or when the lingual swelling has receded. intradural lesion requires relieving the CSF turgidity by having previously placed a lumbar subarachnoid drain. The Evaluation of Postoperative Stability Once the intradural operation is completed, it is essential to bring the dural leaves together in as watertight a closure as possible. In a situation where the dura has been vio Pleuridirectional tomography of the craniocervical lated. it is important to harvest external oblique aponeuro junction is obtained I week after the transoral operation, sis for fascia to be layed against the dural closure. This to determine the craniocervical junction stability. This is should be reinforced with a fat pad and held in position by done in the flexed and extended positions to determine and anteroposterior stability, as well as with and without plasma glue. The longus colli muscles, as well as the constrictor traction, assessing the vertical stability. An offset at the muscles of the pharynx and the posterior pharyngeal lateral occipitoatlanto-axial articulation, during the flexed mucosa are closed in individual layers using interrupted and extended studies, or excessive vertical displacement of sutures of polyglycolic. In the event that the opening in the craniospinal axis is indicative of instability. MRI is the clivus is large, a pharyngeal pack may be utilized for likewise performed at this time to assess the extent of compression of the high nasopharynx with traction tubes decompression. Should instability be present, an occipito brought out through the nostrils. At this juncture, a soft cervical fixation is mandatory and this should be done feeding tube is passed via the nostrils into the nasophar from a dorsal approach. Of the 188 patients who underwent transoral operation ynx and guided, under direct vision, into the esophagus and placed into the stomach. This is done after the throat in the author’s experience, 74 were children (table 2). One pack is removed. The position of the feeding tube in the hundred and fifty-eight individuals demonstrated postop stomach is confirmed by installation of air into the tube erative instability at the craniocervical junction (66 chil and confirmation by the anesthesiologist auscultating over dren) and these required a posterior occipitocervical the abdomen. This tube must be anchored to the skin at fixation. Children who have undergone a dorsal fixation the base of the nasal septum. The nasal mucosa of the soft are ambulated in a halo vest. This usually necessitates 4 -6 palate is approximated with simple interrupted sutures as months of craniocervical immobilization. is the muscular layer. It is advisable to use vertical mat Dorsal fixation is usually necessary after transoral tress sutures to bring the oral mucosa together, incorpo clivus odontoid complex resections in congenital and de rating the muscular layer also. This prevents dehiscence. velopmental abnormalities associated with atlas assimila In situations where surgery is necessary through the tion and/or segmentation failures of the second and third clivus, or in patients with a foreshortened clivus and cervical vertebrae. It was also dictated in the child with platybasia, the hard palate is exposed and the posterior Down’s syndrome. 1 cm is resected. This allows a high nasopharyngeal expo sure without splitting the mandible or doing a median glossotomy. In such instances the nasal septum and vomer Results may be resected. The patient is maintained in 5-7 lb of skeletal traction Neurological improvement was seen in all patients. after operation, especially in unstable situations. Nasogas Four children who were ventilator dependent prior to the tric feeding is instituted at the end of 24 h. Oral intake is operation, following previous primary posterior fossa de-
Table 2. Summary of surgical treatment at the craniocervical junction in 558 patients (1977-1990)
Stability
Compression
Approach
Postoperative Stability
Immobilization 36 (30)
A. Reducible 268 (89)
Posterior Fusion 232 (59)
Stable 30 (8) "Ventral 188 (74)
Anterior
1
.Unstable 158 (66)
B. Irreducible 290 ( 122)
Stable 36 ( 16) Dorsal L102 (48)
Posterior
1
.Unstable 66 (32)
158 (66)
36 (16)
66 ( 32)
Number of children in parentheses.
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Table 3. Pathology encountered at the ventral craniocervical compressions or trauma, had resolution of their neurolog ical symptoms and signs. Downbeat nystagmus, brain junction in 74 children using the transoral-transpalato-pharyngcal stem dysfunction with cranial nerve palsies and sleep approach apnea were prominent in children with basilar invagina Basilar invagination tion with an associated Chiari malformation. These signs Primary anterior 30 Anterior + paramedian 23 regressed following the ventral procedure. An intradural pathology was present in 24 individuals (Chiara malformation 22/63) Dystopic os odontoideum. with invaginating axis 7 of the 188 adults and children who underwent this opera 2 Osteoblastoma Cl tion. There was no episode of meningitis and in no in Down's syndrome, with fixed cranial settling 1 stance was a septomucoperiosteal flap or pharyngeal flap Clivus chordoma 1 needed for closure of the posterior pharyngeal wall or the 74 dura. Lumboperitoneal CSF shunting was never rquired. Total as in some other series. In regards to the children alone, a pharyngeal wound dehiscence occurred in 2 individuals. In the first, a Two adults died within the first month after operation. Yankauer suction was inappropriately handled by the patient reopening the pharyngeal wound at the end of 10 An elderly male with rheumatoid arthritis and cranial days. In another individual, a retropharyngeal infection settling succumbed to a myocardial infarction 4 weeks was present caused by bacteroides. This was treated with after his dorsal fixation operation. Another 52-year-old intravenous antibiotics and allowing drainage into the woman, admitted quadriplegic after a motor vehicle acci pharynx. Intravenous hyperalimentation was necessary for dent on a ventilator, was transferred to our institution with severe pontomedullary dysfunction. She underwent 2 weeks after which the dorsal fixation was then made. Three children were subsequently evaluated for velo- emergent transoral decompression of the severe basilar palatine incompetence. This particular problem is seen in invagination and paramedian compression of the medulla. young individuals and usually 3 -6 months after transoral She achieved normal respiratary function within a week operation where the palate may have been split. It is felt and was off the ventilator. She succumbed to sepsis of that this is secondary to fibrosis that takes place in the soft urinary tract origin which existed at the time of her palate or the pharyngeal wall. Endoscopy identified the admission. The pathology encountered in 74 children is repre cause. Pharyngeal retraining in 2 individuals and an obtu sented in table 3. rator in the third individual circumvented the problem.
Fig. 3. a Midsagittal Tl-weighted VIRI of head and neck of case VI.H. made 3 months alter posterior fossa craniectomy and Cl decompressive laminectomy. Note the abnormal clivus-odontoid angle with severe ventral medulla compression and the hind brain herniation into the cervical canal, b Axial Tl-weighted MRI at the Cl level (case M.B.). The medulla oblongata (m) is ventrally compressed by the pannus and odontoid (white arrow). Note the medially approximated cerebellar tonsils, c Composite of preoperative CCJ tomograms in case MB. The inferior clivus articulates with the anterior atlas arch and the odontoid. The lateral atlantal masses are assimilated to the occiput (frontal tomogram), d Midsagittal Tl-weighted MRI of CCJ made after ventral transoral decompression. The bony compression of C’l-odontoid has been removed and good medullary decompression achieved, e Composite of postoperative CCJ tomograms made after the transoral resection in case M B. Note the resected anterior arch of atlas and the odontoid process. There is lateral Cl-C'2 instability seen on the frontal tomogram.
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Chiari malformation with basilar invagination. He underwent poste rior fossa and upper cervical spine decompression. Shortly after this operative procedure, his headaches worsened and paresthesias in the left arm set in. At the time of our evaluation at the University of Iowa Hospitals and Clinics, the main abnormalities were bilateral internuclear oph thalmoplegia. mild spastic quadriparesis with weakness in the arms more than the legs, and a spastic ataxic gait.
The Anterior Midlinc Approach to the Craniocervical Region in Children
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Case Studies (1) M.B.: This 16-year-old male presented with severe occipital and vertex headaches, ataxic gait and left arm paresthesias. At the age of 13 years, he had horizontal diplopia and subsequently under went surgery on his right eye for strabismus. This worsened his visual difficulties. He then had a similar operative procedure for strabismus on his left eye. At age 16 years his headaches worsened and the diplopia progressed. He was evaluated with MRI. This revealed a
Fig. 4. a C ase A .M Composite of midsagittal T lweighted MR1 of the CCJ in the flexed (L) and extended ( R) positions. There is assimilation of the atlas, herniation of cerebellar tonsils into the spinal canal and syringohydromyelia. Ventral cervicomedullary compression is only partially reducible in the extended position, b Axial TI-weighted MR I of case A.M. at the foramen magnum. The medulla (m) is indented ventrally by the bony mass (arrow) and dorsally compressed by the herniated cerebellar tonsils.
procedure. He recovered neurological function. MRI done just after the ventral decompression revealed resolution of the syringohy dromyelia. as well as the bony compression.
Discussion
The transoral approach to the posterior pharyngeal wall has been an operation used for drainage of retropha ryngeal abscesses for many years. Although this route provides direct access to the craniovertebral junction, it has not gained its well-deserved place in the neurosurgical armamentarium. The reasons for this have been attributed to initial reports of infection, limited exposure, unaccept able patient morbidity and mortality and cerebral spinal fluid leakage. We feel that this series has shown that the ventral transoral-transpharyngeal approach to the lower clivus and upper cervical spine is safe, rapid, and effective. It is important in relieving ventral irreducible pathology of the craniovertebral junction.
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MRI revealed basilar invagination by an abnormal clivus-odon toid Cl complex (fig. 3a. b). There was atlas assimilation present (fig. 3c). The medulla was markedly indented by the ventral bony abnor mality. The cerebellum appeared to be slumped into the posterior fossa defect and also into the upper cervical canal. Marked compres sion of the medulla oblongata was evident, caused by chronic granu lation tissue and the osseous pathology. Transoral procedure was performed for ventral decompression of the medulla. Postoperative MRI showed marked improvement in the ventral bony angulation with relief of medullary compression (fig. 3d). An offset in the anterior relationships of the assimilated atlas and the lateral C2 masses was evident on the subsequent tomograms ( fig. 3e). He required an occipitocervical fixation and is now asymptomatic. (2) A.M.: This is a 9-year-old male who became symptomatic when struck on the football field. He experienced neck pain and subsequently noticed drooping of his right eyelid, clumsiness with his right arm and right leg. and was noted to have a Horner's pupil. MRI revealed a partially reducible basilar invagination with atlas assimilation (fig. 4a). A Chiari I malformation was evident with syringohydromyelia. Severe ventral bony compression of the medulla was visualized on the axial Tl images (fig. 4b). A transoral decom pression was performed followed by a dorsal occipitocervical fixa tion. A duraplasty was made at the time of the dorsal occipitocervical
The advantages of the transoral-transpalatine approaeh to the craniocervical region, compared to other operative approaches in irreducible pathology include: (1) the im pinging bony and granulation pathology that accompanies chronic instability is accessible via the ventral route. (2) The child is placed in the extended position as opposed to the flexed position, thus decreasing the angulation of the brain stem during surgery. (3) Surgery is performed through the avascular median raphe and through the clivus. The indications for the transoral operation at the ante rior craniocervical border must be exact. A precise defini tion of pathology usually requires more than one radiological procedure. Mere identification of ventral pathology without attempts at reduction are no grounds for the operative procedure. The primary approach to intra-arachnoid lesions at foramen magnum should not be by the transoral route unless other approaches prove ineffective. The extent of surgical exposure of the anterior cranio cervical junction in the transoral approach is limited by the emergence of the hypoglossal nerves 2 cm lateral to the middle of the clivus, by the vertebral arteries and by the eustachian tubes lying just below the base of the skull. However, these structures allow at least 3.5 cm of expo sure which is certainly sufficient for removal of pathology from the lower half of the clivus down to the C2-C3 interspace.
A Chiari malformation was identified in 48 patients who underwent a transoral operation. Several of these individu als had undergone a primary operation consisting of a posterior fossa and upper cervical canal decompression. Rapid deterioration ensued in these patients, or an initial improvement was followed by progressive deterioration in neurological function. In each of these instances the MRI showed an increase in the ventral cervicomedullary junction compression and angulation secondary to the ‘peg-like' basilar invagination. More importantly, a slump of the cerebellum into the newly created posterior decompression worsened the situation and caused further impaction. One wonders whether this was the cause of the syringohydromyelia occurring as a result of the changes in the craniospinal dynamics. The improvement after ventral de compression can be attributed to relief of brain stem angulation, improved blood supply, or changes in the cerebral spinal fluid pressure dynamics. The basic transoral approach has been used for clipping of midline aneurysms of the vertebral basilar system. Disadvantages of this operation include accommodating the length of the aneursym clips in the exposure and the difficulty in obtaining dural approximation over the ven tral aspect of the brain stem. The anterior midline approach to the craniocervical region in children is best served via the transoral route which is safe, rapid, and efficacious in providing decom pression of the cervicomedullary region.
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The Anterior Midline Approach to the Craniocervical Region in Children
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