Accepted Manuscript Cerebrospinal Fluid Leaks And Encephaloceles of Temporal Bone Origin: Nuances To Diagnosis And Management Dhruve S. Jeevan , B.M. B.Ch., D., Ryan Ormond , M.D., Ana H. Kim , M.D., Lawrence Z. Meiteles , M.D., Katrina R. Stidham , M.D., Christopher Linstrom , M.D., Raj Murali , M.D. PII:
S1878-8750(14)01382-5
DOI:
10.1016/j.wneu.2014.12.011
Reference:
WNEU 2620
To appear in:
World Neurosurgery
Received Date: 31 March 2014 Revised Date:
22 July 2014
Accepted Date: 9 December 2014
Please cite this article as: Jeevan DS, Ormond R, Kim AH, Meiteles LZ, Stidham KR, Linstrom C, Murali R, Cerebrospinal Fluid Leaks And Encephaloceles of Temporal Bone Origin: Nuances To Diagnosis And Management, World Neurosurgery (2015), doi: 10.1016/j.wneu.2014.12.011. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
CEREBROSPINAL FLUID LEAKS AND ENCEPHALOCELES
OF
TEMPORAL BONE
RI PT
ORIGIN: NUANCES TO DIAGNOSIS AND MANAGEMENT
DHRUVE S. JEEVAN1, B.M. B.CH., D. RYAN ORMOND1, M.D., ANA H. KIM2, M.D., LAWRENCE Z. MEITELES2, M.D., KATRINA R. STIDHAM2, M.D., CHRISTOPHER LINSTROM2, M.D., RAJ MURALI1, M.D.
2Department
of Neurosurgery, New York Medical College, Valhalla, NY of Otolaryntology, New York Medical College, Valhalla, NY
SC
1Department
Corresponding author:
TE D
Dhruve Jeevan BMBCh MA Munger Pavillion - Rm 329 Valhalla NY 10595 USA Email: [email protected] Tel: (914) 493-8392 Fax: (914) 345-3112
M AN U
No authors received any funding, or financial support, or have any industrial affiliations in relation to the work involved in this article.
EP
KEY WORDS: CEREBROSPINAL FLUID LEAK, CRANIAL FOSSA, ENCEPHALOCELES, HEARING, SURGERY, MIDDLE-CRANIAL FOSSA, TEMPORAL BONE, TRANS-MASTOID RUNNING TITLE: NUANCES TO MANAGEMENT OF TEMPORAL ENCEPHALOCELES No external source of funding was received in the completion of this review.
AC C
Portions of this work were presented in abstract form/in poster form at the Fifteenth WFNS world congress of neurological surgery, Seoul, Korea, Sep 2013.
ACCEPTED MANUSCRIPT 2 ABSTRACT
Background: Temporal bone encephalocele has become less common as the incidence of chronic
RI PT
mastoid infection and surgery for this condition has decreased. As a result the diagnosis is often delayed and often an incidental finding. This can have serious neurological complications with patients presenting with CSF leak and meningitis.
SC
Objective: To review the occurrence, characteristics of, and repair experience with temporal encephaloceles from 2000-2012.
M AN U
Methods: The authors conducted a retrospective review of 32 patients undergoing combined mastoidectomy and middle cranial fossa craniotomy for the treatment of temporal encephalocele. Results: The diagnosis of temporal encephalocele was made on all patients through highresolution temporal bone computed tomography (CT) and magnetic resonance imaging (MRI).
TE D
Twelve patients had confirmed CSF leak at the time of diagnosis, and other common presenting symptoms included hearing loss and ear fullness. The most common cause of tegmen defect was secondary to chronic otitis media (n=14). Eight of these patients had undergone prior
EP
mastoidectomy, suggesting an iatrogenic cause. Other etiologies included radiation exposure, congenital, and spontaneous defects. Additionally, two patients presented with meningitis, one of
AC C
whom had serious neurological deficits resulting from venous infarction. Conclusion: The risk of severe neurological complications following the herniation of intracranial contents through a tegmen defect necessitates prompt recognition and appropriate management. CT and MR imaging allows for definitive diagnosis. A combined mastoid/middle fossa approach allows for sustainable repair with adequate exposure of defects and support of intracranial contents.
ACCEPTED MANUSCRIPT 3
KEY WORDS: CEREBROSPINAL
FLUID LEAK,
CRANIAL
FOSSA,
ENCEPHALOCELES, HEARING,
AC C
EP
TE D
M AN U
SC
SHORT TITLE: TEMPORAL ENCEPHALOCELES
RI PT
SURGERY, MIDDLE-CRANIAL FOSSA, TEMPORAL BONE, TRANS-MASTOID
ACCEPTED MANUSCRIPT 4 INTRODUCTION
The herniation of dura (meningocele) or brain tissue (encephalocele) into the mastoid or middle
RI PT
ear has become a rare condition. The potential devastating complications, such as meningitis, intracranial abscess, hemorrhage, venous infarction, or seizures, necessitate a high degree of clinical suspicion and prompt surgical evaluation. Before the widespread use of antibiotics
SC
temporal encephaloceles occurred in association with chronic otogenic abscess and sinus thrombophlebitis, as well as after surgery for these infections. Antibiotic therapy has greatly
M AN U
reduced its incidence, and a large series has not been reported in the recent literature.
Meningoceles and meningoencephaloceles of the temporal bone still do occur. They may also be seen in congenital defects of the tegmen, following surgery to the skull base, traumatic fractures,
TE D
erosion from intracranial tumors, or following radiation therapy(15). Despite improvements in radiological imaging of the temporal bone, delayed diagnosis of temporal encephalocele continues to occur. This is often due to the nonspecificity of clinical signs and symptoms. The
EP
most common presenting symptoms are a conductive or mixed hearing loss with a draining ear or serous otitis media. Occasionally a retrotympanic pulsating mass can even be found on
AC C
otological examination, or during surgical drainage of the mastoid. Various surgical techniques have been proposed for the closure of this defect. Herein we review 32 cases of temporal encephalocele presenting at our institution between 2003-2012, and discuss some of the nuances of its presentation and management.
ACCEPTED MANUSCRIPT 5
METHODS
RI PT
A retrospective chart review examined 32 patients treated from the year 2000 until 2012 by a single neurosurgeon. All patients identified had been treated for encephalocele of the temporal bone. 12 patients had spontaneous CSF leaks, and 3 had intraoperative finding of encephalocele
M AN U
neuroma surgery were excluded from the study.
SC
during mastoid surgery. Patients who developed temporal bone CSF leaks following acoustic
Data was collected from office and hospital charts regarding patient demographics, including age, gender, and co-morbid conditions. Information was also collected regarding preoperative diagnostic tests, including laboratory tests, preoperative audiograms and imaging. All patients
TE D
underwent combined mastoid/middle fossa repair with autologous bone graft. Intraoperative findings and the use of lumbar drainage of CSF were also noted on review. Length of
AC C
RESULTS
EP
postoperative follow-up, post-operative complications and audiology were also noted.
Patient Demographics
32 patients underwent 34 operations for temporal encephalocele. Fifteen of the patients were male. The median age at diagnosis was 51 with an age range between 5 and 74 years. Two
ACCEPTED MANUSCRIPT 6 patients had undergone prior repair. One patient via a transmastoid repair alone, one with use of only fascia for skull base repair.
RI PT
Clinical Presentation
Of the twelve patients with spontaneous CSF leaks, two had a history of meningitis or presented
SC
with meningitis confirmed by lumbar puncture. Otorrhea was a symptom in 10 patients, 3 occurring following tympanostomy tube placement, and others occurring in the presence of a
M AN U
concurrent tympanic membrane perforation. β-2 transferrin testing confirmed the presence of leak in two patients. The average duration of symptoms potentially attributable to CSF leak was 5 years. Three patients had a diagnosis of cholesteatoma, and 14 patients had a history of chronic otitis media, eight having undergone prior mastoidectomy. 3 patients were found to have
TE D
encephaloceles incidentally on surgical mastoid exploration for presumed chronic infection. One patient (age 5) was found to have bilateral congential encephaloceles, while one patient (aged 47) had received radiation therapy for leukemia at a young age and now presented with
EP
meningitis, CSF leak, and bilateral temporal encephaloceles. Two patients in our series had erosion of their tegmen from intracranial tumors: one with an epidermoid tumor, and a second
AC C
with a middle cranial fossa meningioma treated with two prior resections and radiation therapy. The excision of the tumor and repair of the bony defect was identical to brain herniation and CSF leak would have resulted without adequate repair. One patient had an acquired encephalocele following trauma, resulting from a gunshot wound associated with extensive skull base fracturing. Presenting symptoms and physical findings are summarized in Table 1.
ACCEPTED MANUSCRIPT 7 Preoperative high-resolution temporal bone computed tomography (CT) was attained in all patients with coronal reconstructions using 1mm contiguous sections. MR imaging with and
on imaging, with MR imaging confirming encephalocele.
SC
Surgical Technique
RI PT
without contrast was also attained in all patients. All patients were found to have tegmen defects
All procedures were completed under general anesthesia. After induction, some patients (n=7)
M AN U
underwent placement of lumbar drainage at the discretion of the operating surgeon. This decision was made on the presence of CSF leak at presentation, size of defect, and brain volume status on imaging. In those patients who had a lumbar drain placed it was maintained for 48-72 hours postoperatively. Patients were positioned supine with the head turned to the contralateral side.
TE D
Lateral positioning is used for very obese patients. A Mayfield 3-pin head holder is used for those patients with poor cervical rotation; otherwise a donut pillow was used with surgical taping. Facial nerve monitoring was used routinely. A reverse “S”-shaped retroauricular incision
EP
was marked (Figure 1a) starting at (or below) the mastoid tip, extending superiorly over the ear, to the temporal line. The temporalis fascia was harvested at this time for later dural repair. The
AC C
temporalis was then divided and retracted using a self-retaining retractor. A mastoidectomy was then performed (Figure 1b).
Aided by CSF drainage from the lumbar drain if used, a temporal craniotomy was then performed. The craniotomy, which rarely needs to measure more than 3 cm × 2 cm, was started just posterior to the root of the zygomatic arch (Figure 1c). Surgery was kept extradural as much
ACCEPTED MANUSCRIPT 8 as possible. During the craniotomy, care was taken to preserve the lateral edge of the bone to support the bone plate that was inserted to fill the bony defect. An extradural exploration was performed along the tegmen mastoideum and tegmen tympani, exposing the cranial base defect
RI PT
and any encephalocele encountered (Figure 1d). Dura was stripped far enough medially and anteriorly to ensure that a second defect in the bone was not missed. Careful review of preoperative CT of the temporal bone also helped in detecting additional defects in the bone. At
SC
this point, the encephalocele was excised from below. The small opening in the dura was repaired with sutures, if possible, or covered with temporalis fascia and fibrin glue. In rare
M AN U
instances, the dural defect could not be fully delineated extradurally, or the encephalocele could not be seen to allow excision, and intradural exploration was performed. In these cases a dural substitute was used for repair. The bony defect was then dissected circumferentially, and when involved, the middle ear ossicles were identified. A portion of the temporal craniotomy bone
TE D
flap was cut and appropriately shaped for concave repair of the cranial base with coverage of the entire defect. A sheet of temporalis fascia was placed over the repair and covered with a small amount of fibrin glue. Attention was paid to avoid dripping of fibrin glue onto the ossicular
EP
chain. The temporal craniotomy defect was covered with heavy weight titanium mesh.
AC C
The mastoid cavity was packed with fat. The temporalis fascia and galea were closed in separate layers with interrupted sutures, and the skin closed with running nylon suture. A sterile mastoid dressing was then applied. The lumbar drain, if placed, was used to drain 5-10 mL/hour postoperatively and usually removed on postoperative day 3 after a 24-hour period of clamping.
Hearing Status
ACCEPTED MANUSCRIPT 9
Pre- and Postoperative audiometric data was available for 25 patients (Table 1). Seven patients did not undergo preoperative testing. A mixed hearing loss was most commonly reported. No
RI PT
patients lost hearing following the repair. One patient sustained additional sensorineural hearing loss due to total petrosectomy. 5 patients had improved hearing postoperatively.
SC
Postoperative Course
M AN U
Average follow-up was 4.9 years. One patient had a postoperative infection requiring reexploration and removal of synthetic graft used for the repair of the skull base. On re-exploration autologous bone graft was used for repair. No patients in our series had recurrence of encephalocele or CSF leakage following repair. On one occasion upon opening the retroauricular
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incision frank pus was seen in the mastoid bowl. At this point the procedure was abandoned following surgical drainage and washout and a delayed repair was performed in 3 months
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CASE EXAMPLES
EP
following antibiotic therapy.
The following cases highlight specific issues:
Case 1
A 50-year-old woman with a history of chronic ear infections presented with worsening unilateral hearingloss. Tympanic examination noted a middle ear effusion, and audiometry
ACCEPTED MANUSCRIPT 10
confirmed worsening conductive hearing loss. The patient stated a frequency of ear infections of 5-10 times per annum, and as a result was planned for masotidectomy. During the procedure a pulsatile mass was encountered arising from the tegmen filling the mastoid bowl with CSF. The
RI PT
wound was subsequently closed and post-operatively CSF continued to leak from the incision. A lumbar drain was placed.
SC
A CT temporal bone confirmed a left partial mastoidectomy with extensive opacification of the mastoid cavity, and a discontinuity of the left tegmen tympani (Figure 2a). An encephalocele was
M AN U
seen on MRI imaging (Figure 2b). The patient underwent a combined mastoid/middle cranial fossa repair of encephalocele. A large defect was found in the tegmen, which was closed in layered fashion with autologous bone graft attained from the temporal craniotomy and temporal fascia with fibrin glue. The lumbar drain remained in place for 48 hours and removed after 24
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hours of clamping when no CSF was seen leaking from the incision.
This case represents not an atypical presentation of temporal encephalocele with CSF leak. A
AC C
EP
high degree of suspicion needs to be maintained and imaging is key to diagnosis.
Case 2
A 65- year-old man with a history of chronic middle ear infections and prior mastoiditis (mastoidectomy 9 years ago), presented to an outside hospital with three days of worsening headache, confusion, neck stiffness, photophobia, and a fever of 102°F. He also reported a 3week history of salty taste at the back of his throat, and right facial weakness. A lumbar puncture
ACCEPTED MANUSCRIPT 11
was performed revealing a white blood cell count of 2951/cm3 with 444/cm3 red blood cells, glucose of 36 mg/dL, and protein count of 138 mg/dL. The initial Gram stain was negative. The patient underwent noncontrast temporal bone CT showing a bony defect of the tegmen
RI PT
mastoideum (Figure 3a), and an MRI with contrast highlighted a moderately large region of restricted diffusion in the right cerebellum, brachium pontis, and pons compatible with cytotoxic edema due to venous infarction or possibly cerebritis change (Figure 3c). Slow flow with partial
SC
occlusion of the left sigmoid sinus was also noted. A classic teardrop sign of temporal encephalocele was also seen (Figure 3b). The patient underwent surgical repair via a combined
M AN U
mastoid-middle fossa approach with use of autologous bone graft to reconstruct the skull base (Figure 3d).
The patient is now 3 years post surgery with no evidence of recurrent encephalocele or CSF leak.
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He still has residual right facial weakness, and his gait remains affected from encephalomalacic changes in his brachium pontis resulting from venous infarction. This case illustrates the
AC C
DISCUSSION
EP
devastating complications that can result from an occult CSF leak.
Though a bony defect is necessary to allow meningeal and/or brain tissue to protrude into the temporal bone(24), the dura overlying the middle cranial fossa is capable of supporting the intracranial contents over a large defect, making the herniation of brain tissue into the middle ear cavity a rare entity. Anatomical studies have shown that 20-33% of adult temporal bones have one or multiple defects along the middle cranial floor, yet the incidence of encephaloceles is
ACCEPTED MANUSCRIPT 12
much less(10). Hence, an isolated temporal bone defect is insufficient to cause encephalocele formation(16). Following dural compromise the arachnoid is able to herniate freely, with
RI PT
resultant CSF leakage.
Bony erosion and dural injury can result from the inflammatory process of chronic otitis media(6, 18), or can also occur iatrogenically as a complication of mastoid surgery(21). The use
SC
of a burr near the bony tegmen, and of monoplar electrocautery on the surface of the dura, and the absence of preoperative CT scans to visualize a thinned temporal bone, may result in injury
M AN U
leading to brain herniation. In our own series 8 patients had a long history of chronic otitis media, and had undergone prior mastoid surgery. Often presenting with recurrence of symptoms or CSF leak, these patients were subsequently found to have encephaloceles. The direct correlation is hard to delineate though, as two cases in our own series saw the discovery of an
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encephalocele incidentally on primary mastoid surgery.
Spontaneous CSF leakage and the formation of encephalocele are thought to be related to the
EP
presence of aberrant arachnoid granulations found on the dural surface of the temporal bone(8). With repeated CSF pulsation, a natural progressive enlargement of these spaces occurs with age,
AC C
hence the average presentation at age 53. There is also a slight predominance to encephalocele formation among obese patients with pseudotumor cerebri, likely due to the elevated intracranial pressure(25). In chronic otitis media, these arachnoid granulations could predispose to the intracranial extension of the inflammatory disease(2). Temporal encephaloceles have also been seen following traumatic fractures(4), along with radiation(15), and congenital tegmen abnormalities(19). The formation of encephaloceles relating to cholesteotoma is theorized to be
ACCEPTED MANUSCRIPT 13
the result of local bone resorption from direct pressure ischemia of the enlarging cholesteotoma, or the result of enzymatic degradation(22).
RI PT
The presentation of temporal encephaloceles is often masked by the symptoms related to the primary pathology(28). As a result they are not infrequently encountered intraoperatively. On occasion presumed otitis media with effusion can be treated with tympanic ventilation, resulting
SC
in large volume discharge of CSF. CSF otorrhea and rhinorrhea are common presenting symptoms. Testing of β-2 transferrin is highly sensitive and specific for identifying CSF, though
M AN U
collecting a sufficient aliquot remains problematic. The typical otoscopic findings of a pulsatile mass or a middle ear effusion are nonspecific, especially in operated ears. Audiological testing often demonstrates a conductive hearing loss, though a combined conductive and sensorineural hearing can be seen as a result of underlying disease. Neurologic presentations of epilepsy,
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meningitis, brain or epidural abscess, aphasia, and facial neuropathy are rare and tend to be found in spontaneous encephaloceles(7, 16, 17, 20).
EP
As the presentation of temporal encephaloceles can be nonspecific, imaging is crucial to avoid incidental discovery during surgery. Tegmen defects are clearly identified and delineated on CT
AC C
imaging, and high-resolution temporal bone CT is the initial diagnostic modality of choice. Nevertheless, brain herniation cannot be differentiated from cholesteotoma, granulation tissue, or cholesterol granuloma on CT scanning(11). MR imaging in coronal planes should be performed to depict herniated tissue, and can be seen in all sequences in continuity with the cerebral tissue, with an interruption of the dural line, so called teardrop sign. Cholesteotoma in contrast, appears hyperintense on T2-weighted imaging, and a cholesterol granuloma appears hyperintense on both
ACCEPTED MANUSCRIPT 14
T1 and T2-weighted images. With the administration of contrast, only granulation tissue enhances(3). In addition, MR imaging allows for the detection of intracranial complications of
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brain herniation, such as abscess formation and venous thrombosis.
Various surgical repair techniques of these defects have been described in the literature. The principles of surgery remain the same across these different techniques, namely: (1) management
SC
of the herniated brain, (2) restoration of dural integrity with adequate support of intracranial contents, and (3) exenteration of mastoid infection and cholesteotoma. To accomplish the goals
M AN U
of surgery, three major surgical approaches exist: transmasotid repair from below(25), middle fossa approach from above, or a combined approach. The authors prefer the latter as it often allows complete exploration of the tegmen with resurfacing of the bony defects and a more stable repair, as well as simultaneous complete debridement of the mastoid bowl. The
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transmastoid approach is best for small defects (
S1878-8750(14)01382-5
DOI:
10.1016/j.wneu.2014.12.011
Reference:
WNEU 2620
To appear in:
World Neurosurgery
Received Date: 31 March 2014 Revised Date:
22 July 2014
Accepted Date: 9 December 2014
Please cite this article as: Jeevan DS, Ormond R, Kim AH, Meiteles LZ, Stidham KR, Linstrom C, Murali R, Cerebrospinal Fluid Leaks And Encephaloceles of Temporal Bone Origin: Nuances To Diagnosis And Management, World Neurosurgery (2015), doi: 10.1016/j.wneu.2014.12.011. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
CEREBROSPINAL FLUID LEAKS AND ENCEPHALOCELES
OF
TEMPORAL BONE
RI PT
ORIGIN: NUANCES TO DIAGNOSIS AND MANAGEMENT
DHRUVE S. JEEVAN1, B.M. B.CH., D. RYAN ORMOND1, M.D., ANA H. KIM2, M.D., LAWRENCE Z. MEITELES2, M.D., KATRINA R. STIDHAM2, M.D., CHRISTOPHER LINSTROM2, M.D., RAJ MURALI1, M.D.
2Department
of Neurosurgery, New York Medical College, Valhalla, NY of Otolaryntology, New York Medical College, Valhalla, NY
SC
1Department
Corresponding author:
TE D
Dhruve Jeevan BMBCh MA Munger Pavillion - Rm 329 Valhalla NY 10595 USA Email: [email protected] Tel: (914) 493-8392 Fax: (914) 345-3112
M AN U
No authors received any funding, or financial support, or have any industrial affiliations in relation to the work involved in this article.
EP
KEY WORDS: CEREBROSPINAL FLUID LEAK, CRANIAL FOSSA, ENCEPHALOCELES, HEARING, SURGERY, MIDDLE-CRANIAL FOSSA, TEMPORAL BONE, TRANS-MASTOID RUNNING TITLE: NUANCES TO MANAGEMENT OF TEMPORAL ENCEPHALOCELES No external source of funding was received in the completion of this review.
AC C
Portions of this work were presented in abstract form/in poster form at the Fifteenth WFNS world congress of neurological surgery, Seoul, Korea, Sep 2013.
ACCEPTED MANUSCRIPT 2 ABSTRACT
Background: Temporal bone encephalocele has become less common as the incidence of chronic
RI PT
mastoid infection and surgery for this condition has decreased. As a result the diagnosis is often delayed and often an incidental finding. This can have serious neurological complications with patients presenting with CSF leak and meningitis.
SC
Objective: To review the occurrence, characteristics of, and repair experience with temporal encephaloceles from 2000-2012.
M AN U
Methods: The authors conducted a retrospective review of 32 patients undergoing combined mastoidectomy and middle cranial fossa craniotomy for the treatment of temporal encephalocele. Results: The diagnosis of temporal encephalocele was made on all patients through highresolution temporal bone computed tomography (CT) and magnetic resonance imaging (MRI).
TE D
Twelve patients had confirmed CSF leak at the time of diagnosis, and other common presenting symptoms included hearing loss and ear fullness. The most common cause of tegmen defect was secondary to chronic otitis media (n=14). Eight of these patients had undergone prior
EP
mastoidectomy, suggesting an iatrogenic cause. Other etiologies included radiation exposure, congenital, and spontaneous defects. Additionally, two patients presented with meningitis, one of
AC C
whom had serious neurological deficits resulting from venous infarction. Conclusion: The risk of severe neurological complications following the herniation of intracranial contents through a tegmen defect necessitates prompt recognition and appropriate management. CT and MR imaging allows for definitive diagnosis. A combined mastoid/middle fossa approach allows for sustainable repair with adequate exposure of defects and support of intracranial contents.
ACCEPTED MANUSCRIPT 3
KEY WORDS: CEREBROSPINAL
FLUID LEAK,
CRANIAL
FOSSA,
ENCEPHALOCELES, HEARING,
AC C
EP
TE D
M AN U
SC
SHORT TITLE: TEMPORAL ENCEPHALOCELES
RI PT
SURGERY, MIDDLE-CRANIAL FOSSA, TEMPORAL BONE, TRANS-MASTOID
ACCEPTED MANUSCRIPT 4 INTRODUCTION
The herniation of dura (meningocele) or brain tissue (encephalocele) into the mastoid or middle
RI PT
ear has become a rare condition. The potential devastating complications, such as meningitis, intracranial abscess, hemorrhage, venous infarction, or seizures, necessitate a high degree of clinical suspicion and prompt surgical evaluation. Before the widespread use of antibiotics
SC
temporal encephaloceles occurred in association with chronic otogenic abscess and sinus thrombophlebitis, as well as after surgery for these infections. Antibiotic therapy has greatly
M AN U
reduced its incidence, and a large series has not been reported in the recent literature.
Meningoceles and meningoencephaloceles of the temporal bone still do occur. They may also be seen in congenital defects of the tegmen, following surgery to the skull base, traumatic fractures,
TE D
erosion from intracranial tumors, or following radiation therapy(15). Despite improvements in radiological imaging of the temporal bone, delayed diagnosis of temporal encephalocele continues to occur. This is often due to the nonspecificity of clinical signs and symptoms. The
EP
most common presenting symptoms are a conductive or mixed hearing loss with a draining ear or serous otitis media. Occasionally a retrotympanic pulsating mass can even be found on
AC C
otological examination, or during surgical drainage of the mastoid. Various surgical techniques have been proposed for the closure of this defect. Herein we review 32 cases of temporal encephalocele presenting at our institution between 2003-2012, and discuss some of the nuances of its presentation and management.
ACCEPTED MANUSCRIPT 5
METHODS
RI PT
A retrospective chart review examined 32 patients treated from the year 2000 until 2012 by a single neurosurgeon. All patients identified had been treated for encephalocele of the temporal bone. 12 patients had spontaneous CSF leaks, and 3 had intraoperative finding of encephalocele
M AN U
neuroma surgery were excluded from the study.
SC
during mastoid surgery. Patients who developed temporal bone CSF leaks following acoustic
Data was collected from office and hospital charts regarding patient demographics, including age, gender, and co-morbid conditions. Information was also collected regarding preoperative diagnostic tests, including laboratory tests, preoperative audiograms and imaging. All patients
TE D
underwent combined mastoid/middle fossa repair with autologous bone graft. Intraoperative findings and the use of lumbar drainage of CSF were also noted on review. Length of
AC C
RESULTS
EP
postoperative follow-up, post-operative complications and audiology were also noted.
Patient Demographics
32 patients underwent 34 operations for temporal encephalocele. Fifteen of the patients were male. The median age at diagnosis was 51 with an age range between 5 and 74 years. Two
ACCEPTED MANUSCRIPT 6 patients had undergone prior repair. One patient via a transmastoid repair alone, one with use of only fascia for skull base repair.
RI PT
Clinical Presentation
Of the twelve patients with spontaneous CSF leaks, two had a history of meningitis or presented
SC
with meningitis confirmed by lumbar puncture. Otorrhea was a symptom in 10 patients, 3 occurring following tympanostomy tube placement, and others occurring in the presence of a
M AN U
concurrent tympanic membrane perforation. β-2 transferrin testing confirmed the presence of leak in two patients. The average duration of symptoms potentially attributable to CSF leak was 5 years. Three patients had a diagnosis of cholesteatoma, and 14 patients had a history of chronic otitis media, eight having undergone prior mastoidectomy. 3 patients were found to have
TE D
encephaloceles incidentally on surgical mastoid exploration for presumed chronic infection. One patient (age 5) was found to have bilateral congential encephaloceles, while one patient (aged 47) had received radiation therapy for leukemia at a young age and now presented with
EP
meningitis, CSF leak, and bilateral temporal encephaloceles. Two patients in our series had erosion of their tegmen from intracranial tumors: one with an epidermoid tumor, and a second
AC C
with a middle cranial fossa meningioma treated with two prior resections and radiation therapy. The excision of the tumor and repair of the bony defect was identical to brain herniation and CSF leak would have resulted without adequate repair. One patient had an acquired encephalocele following trauma, resulting from a gunshot wound associated with extensive skull base fracturing. Presenting symptoms and physical findings are summarized in Table 1.
ACCEPTED MANUSCRIPT 7 Preoperative high-resolution temporal bone computed tomography (CT) was attained in all patients with coronal reconstructions using 1mm contiguous sections. MR imaging with and
on imaging, with MR imaging confirming encephalocele.
SC
Surgical Technique
RI PT
without contrast was also attained in all patients. All patients were found to have tegmen defects
All procedures were completed under general anesthesia. After induction, some patients (n=7)
M AN U
underwent placement of lumbar drainage at the discretion of the operating surgeon. This decision was made on the presence of CSF leak at presentation, size of defect, and brain volume status on imaging. In those patients who had a lumbar drain placed it was maintained for 48-72 hours postoperatively. Patients were positioned supine with the head turned to the contralateral side.
TE D
Lateral positioning is used for very obese patients. A Mayfield 3-pin head holder is used for those patients with poor cervical rotation; otherwise a donut pillow was used with surgical taping. Facial nerve monitoring was used routinely. A reverse “S”-shaped retroauricular incision
EP
was marked (Figure 1a) starting at (or below) the mastoid tip, extending superiorly over the ear, to the temporal line. The temporalis fascia was harvested at this time for later dural repair. The
AC C
temporalis was then divided and retracted using a self-retaining retractor. A mastoidectomy was then performed (Figure 1b).
Aided by CSF drainage from the lumbar drain if used, a temporal craniotomy was then performed. The craniotomy, which rarely needs to measure more than 3 cm × 2 cm, was started just posterior to the root of the zygomatic arch (Figure 1c). Surgery was kept extradural as much
ACCEPTED MANUSCRIPT 8 as possible. During the craniotomy, care was taken to preserve the lateral edge of the bone to support the bone plate that was inserted to fill the bony defect. An extradural exploration was performed along the tegmen mastoideum and tegmen tympani, exposing the cranial base defect
RI PT
and any encephalocele encountered (Figure 1d). Dura was stripped far enough medially and anteriorly to ensure that a second defect in the bone was not missed. Careful review of preoperative CT of the temporal bone also helped in detecting additional defects in the bone. At
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this point, the encephalocele was excised from below. The small opening in the dura was repaired with sutures, if possible, or covered with temporalis fascia and fibrin glue. In rare
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instances, the dural defect could not be fully delineated extradurally, or the encephalocele could not be seen to allow excision, and intradural exploration was performed. In these cases a dural substitute was used for repair. The bony defect was then dissected circumferentially, and when involved, the middle ear ossicles were identified. A portion of the temporal craniotomy bone
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flap was cut and appropriately shaped for concave repair of the cranial base with coverage of the entire defect. A sheet of temporalis fascia was placed over the repair and covered with a small amount of fibrin glue. Attention was paid to avoid dripping of fibrin glue onto the ossicular
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chain. The temporal craniotomy defect was covered with heavy weight titanium mesh.
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The mastoid cavity was packed with fat. The temporalis fascia and galea were closed in separate layers with interrupted sutures, and the skin closed with running nylon suture. A sterile mastoid dressing was then applied. The lumbar drain, if placed, was used to drain 5-10 mL/hour postoperatively and usually removed on postoperative day 3 after a 24-hour period of clamping.
Hearing Status
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Pre- and Postoperative audiometric data was available for 25 patients (Table 1). Seven patients did not undergo preoperative testing. A mixed hearing loss was most commonly reported. No
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patients lost hearing following the repair. One patient sustained additional sensorineural hearing loss due to total petrosectomy. 5 patients had improved hearing postoperatively.
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Postoperative Course
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Average follow-up was 4.9 years. One patient had a postoperative infection requiring reexploration and removal of synthetic graft used for the repair of the skull base. On re-exploration autologous bone graft was used for repair. No patients in our series had recurrence of encephalocele or CSF leakage following repair. On one occasion upon opening the retroauricular
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incision frank pus was seen in the mastoid bowl. At this point the procedure was abandoned following surgical drainage and washout and a delayed repair was performed in 3 months
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CASE EXAMPLES
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following antibiotic therapy.
The following cases highlight specific issues:
Case 1
A 50-year-old woman with a history of chronic ear infections presented with worsening unilateral hearingloss. Tympanic examination noted a middle ear effusion, and audiometry
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confirmed worsening conductive hearing loss. The patient stated a frequency of ear infections of 5-10 times per annum, and as a result was planned for masotidectomy. During the procedure a pulsatile mass was encountered arising from the tegmen filling the mastoid bowl with CSF. The
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wound was subsequently closed and post-operatively CSF continued to leak from the incision. A lumbar drain was placed.
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A CT temporal bone confirmed a left partial mastoidectomy with extensive opacification of the mastoid cavity, and a discontinuity of the left tegmen tympani (Figure 2a). An encephalocele was
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seen on MRI imaging (Figure 2b). The patient underwent a combined mastoid/middle cranial fossa repair of encephalocele. A large defect was found in the tegmen, which was closed in layered fashion with autologous bone graft attained from the temporal craniotomy and temporal fascia with fibrin glue. The lumbar drain remained in place for 48 hours and removed after 24
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hours of clamping when no CSF was seen leaking from the incision.
This case represents not an atypical presentation of temporal encephalocele with CSF leak. A
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high degree of suspicion needs to be maintained and imaging is key to diagnosis.
Case 2
A 65- year-old man with a history of chronic middle ear infections and prior mastoiditis (mastoidectomy 9 years ago), presented to an outside hospital with three days of worsening headache, confusion, neck stiffness, photophobia, and a fever of 102°F. He also reported a 3week history of salty taste at the back of his throat, and right facial weakness. A lumbar puncture
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was performed revealing a white blood cell count of 2951/cm3 with 444/cm3 red blood cells, glucose of 36 mg/dL, and protein count of 138 mg/dL. The initial Gram stain was negative. The patient underwent noncontrast temporal bone CT showing a bony defect of the tegmen
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mastoideum (Figure 3a), and an MRI with contrast highlighted a moderately large region of restricted diffusion in the right cerebellum, brachium pontis, and pons compatible with cytotoxic edema due to venous infarction or possibly cerebritis change (Figure 3c). Slow flow with partial
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occlusion of the left sigmoid sinus was also noted. A classic teardrop sign of temporal encephalocele was also seen (Figure 3b). The patient underwent surgical repair via a combined
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mastoid-middle fossa approach with use of autologous bone graft to reconstruct the skull base (Figure 3d).
The patient is now 3 years post surgery with no evidence of recurrent encephalocele or CSF leak.
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He still has residual right facial weakness, and his gait remains affected from encephalomalacic changes in his brachium pontis resulting from venous infarction. This case illustrates the
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DISCUSSION
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devastating complications that can result from an occult CSF leak.
Though a bony defect is necessary to allow meningeal and/or brain tissue to protrude into the temporal bone(24), the dura overlying the middle cranial fossa is capable of supporting the intracranial contents over a large defect, making the herniation of brain tissue into the middle ear cavity a rare entity. Anatomical studies have shown that 20-33% of adult temporal bones have one or multiple defects along the middle cranial floor, yet the incidence of encephaloceles is
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much less(10). Hence, an isolated temporal bone defect is insufficient to cause encephalocele formation(16). Following dural compromise the arachnoid is able to herniate freely, with
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resultant CSF leakage.
Bony erosion and dural injury can result from the inflammatory process of chronic otitis media(6, 18), or can also occur iatrogenically as a complication of mastoid surgery(21). The use
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of a burr near the bony tegmen, and of monoplar electrocautery on the surface of the dura, and the absence of preoperative CT scans to visualize a thinned temporal bone, may result in injury
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leading to brain herniation. In our own series 8 patients had a long history of chronic otitis media, and had undergone prior mastoid surgery. Often presenting with recurrence of symptoms or CSF leak, these patients were subsequently found to have encephaloceles. The direct correlation is hard to delineate though, as two cases in our own series saw the discovery of an
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encephalocele incidentally on primary mastoid surgery.
Spontaneous CSF leakage and the formation of encephalocele are thought to be related to the
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presence of aberrant arachnoid granulations found on the dural surface of the temporal bone(8). With repeated CSF pulsation, a natural progressive enlargement of these spaces occurs with age,
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hence the average presentation at age 53. There is also a slight predominance to encephalocele formation among obese patients with pseudotumor cerebri, likely due to the elevated intracranial pressure(25). In chronic otitis media, these arachnoid granulations could predispose to the intracranial extension of the inflammatory disease(2). Temporal encephaloceles have also been seen following traumatic fractures(4), along with radiation(15), and congenital tegmen abnormalities(19). The formation of encephaloceles relating to cholesteotoma is theorized to be
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the result of local bone resorption from direct pressure ischemia of the enlarging cholesteotoma, or the result of enzymatic degradation(22).
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The presentation of temporal encephaloceles is often masked by the symptoms related to the primary pathology(28). As a result they are not infrequently encountered intraoperatively. On occasion presumed otitis media with effusion can be treated with tympanic ventilation, resulting
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in large volume discharge of CSF. CSF otorrhea and rhinorrhea are common presenting symptoms. Testing of β-2 transferrin is highly sensitive and specific for identifying CSF, though
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collecting a sufficient aliquot remains problematic. The typical otoscopic findings of a pulsatile mass or a middle ear effusion are nonspecific, especially in operated ears. Audiological testing often demonstrates a conductive hearing loss, though a combined conductive and sensorineural hearing can be seen as a result of underlying disease. Neurologic presentations of epilepsy,
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meningitis, brain or epidural abscess, aphasia, and facial neuropathy are rare and tend to be found in spontaneous encephaloceles(7, 16, 17, 20).
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As the presentation of temporal encephaloceles can be nonspecific, imaging is crucial to avoid incidental discovery during surgery. Tegmen defects are clearly identified and delineated on CT
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imaging, and high-resolution temporal bone CT is the initial diagnostic modality of choice. Nevertheless, brain herniation cannot be differentiated from cholesteotoma, granulation tissue, or cholesterol granuloma on CT scanning(11). MR imaging in coronal planes should be performed to depict herniated tissue, and can be seen in all sequences in continuity with the cerebral tissue, with an interruption of the dural line, so called teardrop sign. Cholesteotoma in contrast, appears hyperintense on T2-weighted imaging, and a cholesterol granuloma appears hyperintense on both
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T1 and T2-weighted images. With the administration of contrast, only granulation tissue enhances(3). In addition, MR imaging allows for the detection of intracranial complications of
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brain herniation, such as abscess formation and venous thrombosis.
Various surgical repair techniques of these defects have been described in the literature. The principles of surgery remain the same across these different techniques, namely: (1) management
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of the herniated brain, (2) restoration of dural integrity with adequate support of intracranial contents, and (3) exenteration of mastoid infection and cholesteotoma. To accomplish the goals
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of surgery, three major surgical approaches exist: transmasotid repair from below(25), middle fossa approach from above, or a combined approach. The authors prefer the latter as it often allows complete exploration of the tegmen with resurfacing of the bony defects and a more stable repair, as well as simultaneous complete debridement of the mastoid bowl. The
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transmastoid approach is best for small defects (
