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C 2011 The American Laryngological,
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Rhinological and Otological Society, Inc.
Transmastoid Extradural–Intracranial Approach for Repair
of Transtemporal Meningoencephalocele: A Review of
31 Consecutive Cases
Maroun T. Semaan, MD; David A. Gilpin, MD; Daniel P. Hsu, MD;
Jay K. Wasman, MD; Cliff A. Megerian, MD, FACS
Objective: To review the clinical presentation, surgical techniques, and outcomes of the transmastoid extradural–
intracranial (TMEDIC) approach for the treatment of transtemporal meningoencephalocele.
Hypothesis: The TMEDIC is a safe and effective approach to repair meningoencephalocele originating from the middle
or posterior cranial fossa.
Study Design: Retrospective chart review.
Setting: Academic neurotologic tertiary referral center.
Patients: Thirty-one consecutive patients diagnosed with transpetrous meningo(encephalo)cele, with or without cerebrospinal fluid leak, between January of 2003 and October of 2010.
Intervention: TMEDIC approach for repairing herniated neural tissue through the tegmen or posterior fossa plate using
the combination of autologous cartilage, fascia, and tissue sealant.
Main Outcome Measures: Anatomic location, size, and number of defects, presence of herniated brain tissue, pre- and
postoperative hearing thresholds, and failure rate.
Results: Mean age was 62 6 26 years. The etiology was spontaneous in 25/31 (80%), congenital in 3/31 (10%),
chronic otitis media in 2/31 (6%), and posttraumatic in 1/31 (4%). Posttympanostomy tube clear otorrhea was the presenting sign in 21/31 (68%) of patients. The mean duration of symptoms was 26 months (range: 1–240). The defect involved the
middle fossa (MF) floor in 25/31 (90%). Both the tegmen tympani and mastoideum were involved in 12/31 (39%) of
patients and multiple dehiscences were seen in 7/31 (22%). In 17/31 (55%) of cases the size exceeded 1 cm. No recurrences
were seen.
Conclusion: The TMEDIC is a safe and effective method to repair transtemporal meningoencephalocele obviating the
need for a middle fossa craniotomy in certain cases.
Key Words: Temporal lobe encephalocele, meningoencephalocele, cerebrospinal fluid leakage, transmastoid extradural
intracranial repair.
Level of Evidence: 2b.
Laryngoscope, 121:1765–1772, 2011
INTRODUCTION
An encephalocele is defined by the presence of cranial contents beyond the normal confines of the skull.1
The nomenclature depends on the content of the
herniated tissue. Meningocele denotes herniation of
meningeal tissue, whereas meningoencephalocele or
encephalocele includes the herniation of parenchymal
From the Department of Otolaryngology—Head and Neck Surgery
(M.T.S., D.A.G., C.A.M.), University Hospitals Case Medical Center, Cleveland,
Ohio, U.S.A.; Department of Neuroradiology & Diagnostic Radiology
(D.P.H.), University Hospitals Case Medical Center, Cleveland, Ohio, U.S.A,
Department of Pathology (J.K.W.), University Hospitals Case Medical
Center, Cleveland, Ohio, U.S.A.
Editor’s Note: This Manuscript was accepted for publication March
15, 2011.
This manuscript was presented as an oral presentation at the
2011 Combined Sections meeting in Scottsdale, Arizona.
The authors have no financial disclosures for this article.
The authors have no conflicts of interest to declare.
Send correspondence to Dr. Maroun T. Semaan, Department of Otolaryngology—Head and Neck Surgery, University Hospitals Case Medical
Center, Cleveland, OH. 44106. E-mail: [email protected]
DOI: 10.1002/lary.21887
Laryngoscope 121: August 2011
brain tissue. To facilitate our discussion, all will be
referred to as encephalocele. The incidence varies
between 1/3,000 to 1/10,000.1,2 Two types of encephaloceles have been described: cranial and basal. Cranial
encephalocele are the most common type and represent
approximately 90% of all encephalocele. The basal type
is further subdivided into midline and lateral encephalocele. Temporal lobe (TL) or middle cranial fossa
encephalocele are basal-lateral and represent the most
common type of basal encephalocele. These anomalies
can be congenital or acquired. Several acquired etiologies exist;3,4 most commonly TL encephalocele are
secondary to chronic otitis media or mastoid surgery.
The osteolytic process seen in chronic cholesteatomatous
or noncholesteatomatous otitis media results in erosion
of the tegmental separation between the epitympanic
and mastoid space, and the intracranial cavity. This
predisposes the affected individual to herniation of intracranial content into the temporal bone. Spontaneous
encephalocele can be congenital or idiopathic. Congenital
encephalocele results from disturbance in the normal
Semaan et al.: TMEDIC Approach for Repair of Transtemporal Meningoencephalocele
1765
MATERIALS AND METHODS
Subjects
Fig. 1. A bipolar is used to cauterize the stalk of the encephalocele (black arrow) that is originating from the junction of the tegmen tympani and tegmen mastoideum.
ossification of the temporal bone, mainly at the junction
between the petro-squamous junction.5,6 Fusion of the
petrosquamous suture is usually complete by 1 year of
age. Persistence or delay in fusion can be due to growth
abnormalities, chemotherapy, or radiotherapy.7 The
resulting defect serves as a route for transmission of the
encephalocele. Idiopathic encephaloceles often occur in
the setting of chronic intracranial hypertension (ICH).8–10
Dural pulsations resulting from chronically elevated intracranial pressure lead to thinning and dehiscence of
the basal bony plate of the anterior or middle cranial
fossa. Certain areas appear more vulnerable such as
areas with aberrant granulation tissue, excessive pneumatization, or congenital weakness.
Current treatment strategies utilize a transmastoid approach, a middle cranial fossa craniotomy, or a
combination of both approaches to gain access to the
defect ensuring adequate repair. Several autologous or
alloplastic materials have been used to repair the
defect with various success.4,11,12 For small laterally
based defects, a transmastoid repair is chosen by many
otologic surgeons.13,14 In large and more medially based
cranial defects, additional access is obtained by a limited middle fossa craniotomy that can be combined
with a transmastoid approach. Traditionally, transmastoid, extracranial repair of large defects has a high rate
of failure.4,11,12 A subtemporal craniotomy provides a
wider exposure and a more stable repair as it allows
for resurfacing of the bone defect from above. In this
manuscript, we review our experience with 31 consecutive cases of encephalocele that underwent a
transmastoid extradural, intracranial (TMEDIC) repair
with tissue grafting (cartilage block) secured above the
bony defect.
Our hypothesis is that the TMEDIC is a safe and
effective approach to repair defect of the lateral cranial
base. A discussion of the clinical presentation, surgical
technique and outcome will be provided in this
manuscript.
Laryngoscope 121: August 2011
1766
Following departmental and institutional review board approval (IRB #09-10-02), retrospective chart review was
conducted on all cases of cerebrospinal fluid leakage, temporal
lobe encephalocele, and/or meningoencephalocele that underwent surgical repair between January 2003 and October 2010.
The search included ICD-9 codes 349.81 (CSF rhinorrhea),
388.61(CSF otorrhea), and 742.0 (Encephalocele). Patients with
iatrogenic cerebrospinal fluid leakage following a lateral skull
base surgery (retrosigmoid or translabyrinthine craniotomy)
were excluded from the study. Patients that underwent a repair
at an outside hospital and followed at our institution were also
excluded from the study.
Data collected included demographic characteristics, clinical and audiometric data (when available), radiographic, and
operative reports. Thirty-one patients were included; 17 (56%)
females and 14 (44%) males. The defect was right sided in 16/31
(52%). The mean age at presentation was 62 6 26 years. The
average duration of symptoms was 26 months (range: 1–240),
whereas the mean duration of follow-up was 30 months (range:
1–91).
A total of 29/31 patients had their surgery performed by
the senior author (C.A.M.) and the other two by M.T.S.
Surgical Technique (Figs. 1–7)
A wide mastoidectomy is performed. The tegmen mastoideum and sigmoid sinus are skeletonized. The site of herniation
is usually suggested by radiographic imaging. Granulation
tissue and reactive bone is gradually removed around the encephalocele. In cases where glial tissue herniation is not
present (i.e., cerebrospinal fluid leak without meningoencephalocele), the site of leakage and associated meningeal herniation
are identified. Surrounding bone is removed using a diamond
burr. The stalk of the herniated brain is usually identified in
cases of meningoencephalocele. With a bipolar cautery, the stalk
is cauterized and the encephalocele is sectioned at its base and
amputated. If the base is sessile, the bipolar cautery is used to
coagulate its base allowing it to shrink and subsequently
sharply amputated. This is usually nonfunctional neural tissue
Fig. 2. A blunt instrument (a rosen knife or small dural elevator) is
being used to elevate create an epidural space around the encephalocele (black arrow). This dissection is essentially intracranial
and extradural.
Semaan et al.: TMEDIC Approach for Repair of Transtemporal Meningoencephalocele
Fig. 3. An epidural pocket is elevated off the middle fossa floor
large enough to fit the cartilage graft.
and postoperative deficits are rare. Intraoperative frozen section
analysis is carried out to confirm the diagnosis (Fig. 8). Next,
the dura is elevated off the floor of the middle cranial fossa via
the bone defect with a small elevator at least one half centimeter circumferentially around the tegmental defect allowing
room for an intracranial conchal cartilage graft to be locked in
place. This elevation is essentially extradural and intracranial
limited to the epidural space. In defects involving the tegmen
tympani, the lateral epitympanum is exposed and if necessary
disarticulation of the incus followed by ossicular chain reconstruction using autologous incus or a partial ossicular
replacement prosthesis is employed. In these cases a posterior
tympanotomy is performed in order to gain access to the mesotympanum without elevating a tympanomeatal flap and to
adequately visualize the position of the prosthesis. The repair of
the defect in these cases is similarly done using conchal cartilage and temporalis fascia grafting medial to the cartilage
repair. The cartilage is adequately shaped and inserted through
the tegmental defect into the epidural space and allowed to lock
into place. This locking maneuver stabilizes the graft. Its relative surface area is greater then that of the bony defect
allowing for stable secure coverage. The weight of the overlying
temporal lobe adds to its stability. Following this, a piece of
temporalis fascia underlies the defect and the mastoid cavity is
Fig. 4. Cartilage graft being inserted into the pocket.
Laryngoscope 121: August 2011
Fig. 5. Cartilage graft locked in place in the epidural pocket covering the defect from its intracranial side and a fascia graft is laid on
the tegmental defect to cover its extracranial side.
filled with a tissue sealant. A free muscle graft is placed in the
antrum to minimize diffusion of the sealant into the epitympanum and/or middle ear space in cases limited to the tegmen
mastoideum. Closure is completed in a multilayered fashion.
Most patients are managed in the outpatient setting with
either same evening discharge or overnight admission with
observation.
RESULTS
Clinical Presentation (Tables I and II)
The etiology was spontaneous in 25/31 (80%), congenital in 3/31 (10%), chronic otitis media in 2/31 (6%),
and posttraumatic in 1/31 (4%). At presentation, 21/31
(68%) had persistent clear otorrhea post prior to tympanostomy tube insertion, whereas 23/31 (74%) had a
middle ear effusion described during the course of their
illness. Subjective hearing loss was reported in 25/31
Fig. 6. A temporalis fascia graft is seen overlying the tegmental
defect (black arrows).
Semaan et al.: TMEDIC Approach for Repair of Transtemporal Meningoencephalocele
1767
TABLE I.
Demographic and Clinical Data.
Parameters
Results (% or Range)
Sex
Female: 17/31 (56)
Mean age
Male: 14/31 (44)
62 6 26 years
Mean duration of symptoms
26 months (1–240)
Mean duration of follow-up
Side of encephalocele
30 months (1–91)
Right: 16/31
Left: 15/31
Etiology
Spontaneous: 25/31 (80)
Congenital: 3/31 (10)
Chronic otitis media: 2/31 (6)
Posttraumatic: 1/31 (4)
Fig. 7. Tissue sealant is allowed to fill the mastoid cavity. A free
muscle graft was placed in the antrum (not seen) to minimize filling of the middle ear.
(80%). One patient with posttraumatic TL encephalocele
had a dead ear on presentation. At the initial evaluation
5/31 (16%) described clear rhinorrhea and 4/31(12%) had
pulsatile tinnitus as a presenting symptom. The mean
duration of symptoms prior to diagnosis was 26 months
(range: 1–240). Six patients had a history of meningitis,
of which two developed brain abscesses that required
craniotomy and drainage prior to repair of the encephalocele. A total of 7/31(22%) patients had clinical and
radiographic features suggestive of pseudotumor cerebri
or idiopathic intracranial hypertension. In 2/7, a confirmative lumbar puncture was not performed. A total of
7/31(22%) patients had chronic headache. A total of 5/
7 (71%) patients with chronic headache had features
suggestive of benign intracranial hypertension and were
concomitantly managed for this process.
Audiometric Testing
Preoperative audiograms were available in 22/31
(71%) patients. Postoperative audiograms were unavailable in 10/31 patients (32%). For this study, preoperative
audiograms were chosen as the most recent available
audiogram prior to surgery. Postoperatively, the last
available audiogram was used. Audiometric data,
included air- and bone-conduction thresholds in dB HL.
Pure-tone average (PTA) threshold was calculated
according to the American Academy of Otolaryngology
Head and Neck Surgery guidelines15 by averaging the
frequencies 0.5, 1, 2, and 3 kHz; if 3 kHz was not measured, 4 kHz was substituted. Air–bone gap (ABG) was
TABLE II.
Clinical Presentation.
Symptom
Fig. 8. (a) A low-powered (100) photomicrograph of an hematoxyline & eosine (H&E)-stained meningoencephalocele. The black
arrow shows the meningeal lining and the arrowhead demonstrates the neural tissue. (b) A high-powered (200) photomicrograph of the same tissue.
Laryngoscope 121: August 2011
1768
N (%)
Otorrhea post-TT
Middle ear effusion
21/31 (68)
23/31 (74)
Subjective hearing loss
25/31 (80)
Clear rhinorrhea
Pulsatile tinnitus
5/31 (16)
4/31 (12)
TT ¼ tympanostomy tube.
Semaan et al.: TMEDIC Approach for Repair of Transtemporal Meningoencephalocele
Fig. 9. (a) Axial and coronal high-resolution temporal bone computed tomography (CT) scan showing a small tegmen
defect on the left with a soft tissue
mass (white arrow) consistent with a
small temporal lobe encephalocele. (b)
Axial and coronal high-resolution temporal bone CT showing a large tegmental defect with herniation of temporal
lobe content into the mastoid cavity
(white arrow). This was an iatrogenic
defect secondary to mastoid surgery.
calculated from air- and bone-conduction thresholds
obtained at the same test interval. The ABG was computed by subtracting bone PTA from air PTA. The mean
preoperative air-conduction (AC) pure tone average
(PTA) was 39 6 18 dB and mean preoperative boneconduction (BC) PTA was 24 6 13 dB. The mean postoperative AC and BC PTA are 36 6 18 and 24 6 15 dB,
respectively. The mean preoperative ABG is 17 6 13 dB.
The mean postoperative ABG is 12 6 11 dB.
Intervention and Operative Findings (Table III)
All 31 patients underwent a repair via a transmastoid approach. The surgical procedure is detailed in the
Methods section. Conchal cartilage, temporalis fascia
graft, and tissue sealant was utilized in all cases. The
encephalocele originated from a defect in the middle
TABLE III.
Surgical Findings.
N (%)
Radiographic Data
Origin of encephalocele
A total of 24 patients had a temporal bone computed tomography scan (CT scan) and 14 patients had a
magnetic resonance imaging (MRI) alone or combined
with a CT scan. The diagnosis was suggested preoperatively in all patients by the presence of a tegmental
defect with middle and/or mastoid opacification on CT
and/or intratemporal parenchymal herniation on MRI
(Figure 9a and b). The most common radiographic finding seen on MRI was the presence of a fluid signal on T2
weighted images. In light of a highly suggestive history
and physical, and radiographic data a beta 2 transferrin
was not performed in our series.
Laryngoscope 121: August 2011
MF: 28/31 (90)
PF: 3/31 (10)
Site of defect when MF
TT: 16/28 (57)
TTþTM: 12/28 (43)
Number of defects
Single: 21/28 (75)
Size in centimeters
Multiple: 7/28 (25)
Less than 1: 14/31 (45)
Between 1 and 2: 10/31 (32)
Brain hernia (true encephalocele)
Greater than 2: 7/31 (23)
27/31 (87)
MF ¼ middle fossa floor; PF ¼ posterior fossa; TT ¼ tegmen tympani; TM ¼ tegmen mastoideum.
Semaan et al.: TMEDIC Approach for Repair of Transtemporal Meningoencephalocele
1769
fossa floor in all but three cases. In those cases, the
defect was located along the posterior fossa plate.
The sinodural angle was the most common location. One
patient had an encephalocele extending into the retrofacial air cells. In the group with defects confined to the
middle fossa floor, 12/28 (43%) patients had a defect
involving both the tegmen tympani and mastoideum. In
7/28 (25%) patients the defects were multiple. Six had
two tegmental defects and one had three areas of herniation. The size of the defect was less then 1 cm in 14/31
(45%), between 1 and 2 cm in 10/31 (32%), and greater
then 2 cm 7/31 (23%). A total of 27/31 (87%) patients
had true encephalocele defined by herniation of brain
parenchyma outside the confines of the skull. All 27
cases had neural and glial tissue confirmed histologically. In all patients that had a tympanostomy tube at
the time of surgery, a fat myringoplasty was performed.
Outcome
All patients had resolution of their cerebrospinal
fluid leakage and middle ear effusion. No clinical recurrences were seen. In 26/31 patients the duration of
follow-up exceeded 4 months. Three patients with pseudotumor cerebri had a contralateral recurrence
requiring a sequential craniotomy with resolution of the
leakage. One of these two patients had the initial procedure performed at a different institution via a middle
fossa craniotomy. That procedure was excluded from the
study. Another patient had the contralateral site
repaired following closure of the study enrollment.
All myringoplasties were successful, and no patient
had a residual perforation.
In the early years, most procedures were done on
an outpatient basis. During the last few years, patients
have been observed overnight.
DISCUSSION
Basal encephalocele involving the temporal bone
can be congenital or acquired.
Congenital encephaloceles are rare developmental
anomalies that may present in childhood or during
adulthood.3,6 A delay or failure of fusion of the petrosquamous suture line results in a tegmental defect that
serves as a route for transmission of a TL encephalocele.5,16 Such delay or absence of fusion can be caused
by growth abnormalities, cytotoxic medications such as
chemotherapeutic agents, and radiotherapy given at an
earlier age. In our series, 3/31 patients were felt to have
a congenital tegmental defect and subsequently developed an encephalocele. Acquired encephalocele typically
presents during adulthood and are idiopathic or secondary to infection, trauma, or neoplasms.1,4,14,17 Idiopathic
temporal bone encephalocele occur without a clearly
identifiable cause. Anatomical studies show that 20 to
33% of adult temporal bones have one or mutiple defects
along the middle cranial floor.18 Despite the relative
high incidence of tegmental defects, temporal bone encephaloceles are rare. It is postulated that chronically
elevated intracranial pressure and pulsations lead
to thinning and dehiscence along the floor.8,19 This
Laryngoscope 121: August 2011
1770
predispose to neural tissue herniation outside the boundaries of the cranium into the temporal bone cavity. The
diagnosis of idiopathic intracranial hypertension or
pseudotumor cerebri is made after exclusion of other
causes of increased intracranial pressure. The clinical
picture is suggestive. These patients tend to be young
obese female with history of chronic headache. The presence of papilledema is not a prerequisite for diagnosis.20
A lumbar puncture showing elevated opening pressure
(>200 mmHg) usually is confirmatory. In our series, 80%
had spontaneous encephalocele. Seven patients had
features suggestive of pseudotumor cerebri. This association is often suggested clinically and radiographically. It
is important to identify this subset of patients. They
tend to have a higher recurrence rate and are at risk of
blindness secondary to chronic papilledema. A total of 3/
7 patients developed contralateral encephalocele that
required subsequent repair. The management of pseudotumor-related cases require a multidisciplinary approach
involving a neurologist and an ophthalmologist. Weight
reduction and diuretics such as acetazolamide might
reduce the incidence of recurrence.
Some authors proposed that aberrant arachnoid
granulations might be another possible etiologic factor.21,22 Normally arachnoid granulations protrude into
the lumen of venous sinuses and are involved in cerebrospinal fluid resorption. They can be aberrantly located
within the periosteal bony plate. With time, they may
enlarge and cause bony erosion. This eventually results
in a communication between the intracranial cavity and
the air spaces of the temporal bone. Middle cranial fossa
aberrant arachnoid granulations are more common than
those arising from the posterior cranial fossa. Intermediate and large size arachnoid granulation can be
associated with bony erosion and communication with
the mastoid air cell system resulting in cerebrospinal
fluid leakage. In our series it is possible that patients
with posterior fossa defects might have had an arachnoid granulation as the origin of the leak.
Iatrogenic encephalocele of the temporal bone are
common.23 Dural exposure during mastoid surgery alone
is insufficient in causing the encephalocele. Dural tear
appears to be a prerequisite for its development.24 Such
a tear may not be recognized at the time of surgery and
delayed encephalocele may occur. Chronic cholesteatomatous or noncholesteatomatous otitis media may cause
bony erosion through inflammation and bony erosion.
The ongoing inflammatory process further weakens the
exposed dura and leads to encephalocele formation. In
two of our patients, chronic otitis media was the presumed cause. In addition to the repair described above,
the management of iatrogenic meningoencephalocele is
dictated by the presence of active disease during
surgery.
Temporal bone encephaloceles commonly present
with cerebrospinal fluid rhinorrhea, intermittent or continuous clear otorrhea posttympanostomy tube or
conductive hearing loss secondary to impingement of the
ossicular chain or middle ear effusion.11,12 Less commonly, they may present with meningitis, retro or
pretympanic mass, partial seizures, or expressive
Semaan et al.: TMEDIC Approach for Repair of Transtemporal Meningoencephalocele
aphasia.16 In the majority of our patients (68%), the diagnosis became evident retrospectively after insertion of
a tympanostomy tube elsewhere revealed clear pulsatile
fluid or continous profuse otorrhea despite multiple
courses of topical treatment. A middle ear effusion was
reported in 74% at some point during the clinical course.
A subjective hearing loss was a common complaint
(80%). Delayed diagnosis was common and the mean duration of symptoms was 26 months (range: 1–240). The
presence of profuse pulsatile otorrhea after tube insertion that persists despite adequate topical treatment
should raise the suspicion of cerebrospinal fluid leak. In
patients who had an available audiogram preoperative,
various degrees of hearing loss were documented in 17
patients. The mean ABG was 17 6 13 dB. Twelve
patients had patent tympanostomy tubes with a residual
conductive loss. The hearing loss was secondary to middle effusion or abutment of the encephalocele against
the ossicles. The dissection of the herniated brain tissue
from the ossicular chain and in three cases, the disarticulation and reconstruction of the chain with autologous
incus or prosthetic material, resulted in some hearing
improvement in the one patient with available postoperative audiogram. This patient had an encephalocele in
the context of chronic otitis. The malleus, incus, and stapes superstructure were missing. A total ossicular
replacement prosthesis (TORP) was used to reconstruct
the ossicular chain. The preoperative AC PTA improved
from 78 to 50 dB postoperatively. The first patient had
an incus interposition The mean postoperative ABG was
12 6 11 dB. In one patient with dead ear secondary to a
remote otic capsule violating temporal bone fracture the
repair was followed by middle and mastoid obliteration.
The Eustachian tube was obliterated as well.
Diagnosis is often suggested clinically and confirmed radiographically. In equivocal cases, detection of
beta 2 transferrin can confirm the diagnosis of cerebrospinal fluid leak. Radiographic studies are helpful in
confirmation and localization of the tegmental defect,
estimation of the size and number, and evaluation of the
proximity of the herniated material to the ossicles. Highresolution CT scan (HRCT) of the temporal bone is helpful in visualization of the fine bony anatomy of the skull
base. In addition, it provides a good anatomic guidance
to the transpetrous approach with its ability to show the
degree of mastoid pneumatization and the position of
the tegmen. MRI is superior in delineating the nature of
the soft tissue. Although fluid signal is seen on T2
weighted images, the presence of herniated brain tissue
with distortion of gyri ‘‘tear-drop sign’’ is highly suggestive.4,25 In obese patients with bilateral or recurrent
encephaloceles, MRI aids in the radiographic diagnosis
of pseudotumor cerebri or benign intracranial hypertension (BIH). An empty sella, flattened optic discs,
prominent cerebrospinal fluid signal along the optic
sheaths, and flattening of the transverse sinuses are
suggestive of BIH.26 In our experience, localizing studies
such as CT or MR cisternography are rarely needed as
combining clinical and routine CT or MR images often
confirms or strongly suggests the diagnosis. In the absence of middle cranial fossa anomalies, a posterior
Laryngoscope 121: August 2011
cranial fossa leak or aberrant granulation tissue should
be sought.
Electroencephalography (EEG) has not been done
routinely in our series in the pre- or postoperative setting. There were no postoperative seizures reported in
our series.
The increased risk of serious infectious complications such as meningitis or meningocephalitis mandates
effective therapy of temporal bone encephalocele.
Numerous authors have published their results in the
surgical
treatment
of
transpetrous
encephalocele.3,4,8,11,23,27 For small defects limited to the tegmen
mastoideum, a transmastoid approach with extracranial
repair using autologous tissue (fascia, cartilage, etc.)
with or without a tissue sealant has been used. Larger
defect and anteromedially located tegmental dehiscences
(i.e., involving the tegmen tympani) have been repaired
with a subtemporal or middle cranial fossa craniotomy
or a combined transmastoid–subtemporal (middle cranial
fossa). Proponents of this approach described a better exposure of floor of the middle cranial fossa including
access to the roof of the tegmen tympani, a more controlled (less traumatic) dissection of the herniated
cerebral tissue from the ossicles without the need to disarticulate the chain and a more stable repair by
interposing an autologous osseous or cartilaginous graft
or alloplastic material between the dura and the floor
creating a stable or locked repair. The classic transmastoid approach had a limited success in repairing larger
defects due to the unstable nature of the extracranial
scaffolding. With continuous intracranial pressure, the
repair is destabilized and the leakage may reoccur. Its
advantages are a relatively safe and outpatient procedure mitigating the need for a craniotomy and the
possibility to diagnose and treat posterior fossa encephalocele that are missed during a middle fossa repair.
Although it provides a panoramic view of the middle cranial fossa floor, the subtemporal approach has
been traditionally a more morbid approach. Despite
being clinically insignificant, several reports suggested a
higher incidence of postoperative electrophysiological
and radiographical abnormalities.28,29 from such a middle fossa craniotomy in addition for the need for
neurosurgical intentive care monitoring postoperatively.
In our review, we describe a transmastoid approach
with a repair utilizing autologous conchal cartilage that
is introduced intracranially–extradurally and interlocked
between the dural and bony floor to create a stable
scaffold.
Although in our series we extended the application
of the transmastoid route for encephalocele repair, the
authors acknowledge the role of the subtemporal
approach in selective cases when feasibility of the TMEDIC is not possible. For very large defects (>4 cm) a
middle fossa approach may offer a better exposure of the
middle cranial fossa allowing a more secured repair. In
addition, a limitation of this study is the small number
of patients reviewed that required disarticulation and
reconstruction of the ossicular chain. Although technically feasible, a larger number is required in this subset
of patients to validate and analyze postoperative hearing
Semaan et al.: TMEDIC Approach for Repair of Transtemporal Meningoencephalocele
1771
restoration using that approach. A well-trained and
equipped neurotologist should be well familiar with both
techniques in order to handle expected or a times unexpected surgical challenges.
CONCLUSION
The transmastoid extradural intracranial approach
is a safe and effective approach to repair defects of the
lateral cranial base. A high incidence of suspicion is necessary to diagnosis. Chronically increased intracranial
hypertension as seen in pseudotumor cerebri or BIH is a
predisposing factor for encephalocele development, and
ipsi- or contralateral recurrence. An appropriate diagnostic workup includes appropriate imaging and
presurgical analysis. An effective treatment strategy
tackles the anatomic defect and recognizes the importance of managing risk factors (when present) in order
to optimize the final outcome.
BIBLIOGRAPHY
1. Kaufman B, Yonas H, White RJ, Miller CF 2nd. Acquired middle cranial
fossa fistulas: normal pressure and nontraumatic in origin. Neurosurgery 1979;5:466–472.
2. Golding-Wood DG, Williams HO, Brookes GB. Tegmental dehiscence and
brain herniation into the middle ear cleft. J Laryngol Otol 1991;105:
477–480.
3. Glasscock ME 3rd, Dickins JR, Jackson CG, Wiet RJ, Feenstra L. Surgical
management of brain tissue herniation into the middle ear and mastoid.
Laryngoscope 1979;89:1743–1754.
4. Jackson CG, Pappas DG Jr, Manolidis S, et al. Brain herniation into the
middle ear and mastoid: concepts in diagnosis and surgical management. Am J Otol 1997;18:198–205; discussion 205–196.
5. Proctor B, Nielsen E, Proctor C. Petrosquamosal suture and lamina.
Otolaryngol Head Neck Surg 1981;89:482–495.
6. Mulcahy MM, McMenomey SO, Talbot JM, Delashaw JB Jr. Congenital
encephalocele of the medial skull base. Laryngoscope 1997;107:910–914.
7. Lalwani AK, Jackler RK, Harsh GR IV, Butt FY. Bilateral temporal bone
encephaloceles after cranial irradiation. Case report. J Neurosurg 1993;
79:596–599.
8. Goddard JC, Meyer T, Nguyen S, Lambert PR. New considerations in the
cause of spontaneous cerebrospinal fluid otorrhea. Otol Neurotol;31:
940–945.
Laryngoscope 121: August 2011
1772
9. Ferguson BJ, Wilkins RH, Hudson W, Farmer J Jr. Spontaneous CSF otorrhea from tegmen and posterior fossa defects. Laryngoscope 1986;96:
635–644.
10. Kemink JL, Graham MD, Kartush JM. Spontaneous encephalocele of the
temporal bone. Arch Otolaryngol Head Neck Surg 1986;112:558–561.
11. Lundy LB, Graham MD, Kartush JM, LaRouere MJ. Temporal bone
encephalocele and cerebrospinal fluid leaks. Am J Otol 1996;17:
461–469.
12. Gubbels SP, Selden NR, Delashaw JB Jr, McMenomey SO. Spontaneous
middle fossa encephalocele and cerebrospinal fluid leakage: diagnosis
and management. Otol Neurotol 2007;28:1131–1139.
13. Sdano MT, Pensak ML. Temporal bone encephaloceles. Curr Opin Otolaryngol Head Neck Surg 2005;13:287–289.
14. Montgomery WW. Dural defects of the temporal bone. Am J Otol 1993;14:
548–551.
15. Committee on Hearing and Equilibrium guidelines for the evaluation of
results of treatment of conductive hearing loss. AmericanAcademy of
Otolaryngology—Head and Neck Surgery Ffoundation, Inc. Otolaryngol
Head Neck Surg 1995;113:186–187.
16. Leblanc R, Tampieri D, Robitaille Y, Olivier A, Andermann F, Sherwin A.
Developmental anterobasal temporal encephalocele and temporal lobe
epilepsy. J Neurosurg 1991;74:933–939.
17. Byrne JV, Britten JA, Kaar G. Chronic post-traumatic erosion of the skull
base. Neuroradiology 1992;34:528–531.
18. Kapur TR, Bangash W. Tegmental and petromastoid defects in the temporal bone. J Laryngol Otol 1986;100:1129–1132.
19. Wessel K, Thron A, Linden D, Petersen D, Dichgans J. Pseudotumor cerebri: clinical and neuroradiological findings. Eur Arch Psychiatry Neurol
Sci 1987;237:54–60.
20. Marcelis J, Silberstein SD. Idiopathic intracranial hypertension without
papilledema. Arch Neurol 1991;48:392–399.
21. Gacek RR. Arachnoid granulation cerebrospinal fluid otorrhea. Ann Otol
Rhinol Laryngol 1990;99:854–862.
22. Gacek RR. Evaluation and management of temporal bone arachnoid granulations. Arch Otolaryngol Head Neck Surg 1992;118:327–332.
23. Neely JG, Kuhn JR. Diagnosis and treatment of iatrogenic cerebrospinal
fluid leak and brain herniation during or following mastoidectomy.
Laryngoscope 1985;95:1299–1300.
24. Ramsden RT, Latif A, Lye RH, Dutton JE. Endaural cerebral hernia.
J Laryngol Otol 1985;99:643–651.
25. de Carpentier J, Axon PR, Hargreaves SP, Gillespie JE, Ramsden RT.
Imaging of temporal bone brain hernias: atypical appearances on
magnetic resonance imaging. Clin Otolaryngol Allied Sci 1999;24:
328–334.
26. Brodsky MC, Vaphiades M. Magnetic resonance imaging in pseudotumor
cerebri. Ophthalmology 1998;105:1686–1693.
27. Linstrom CJ, Krajewski MJ, Shapiro AL, Caruana S. Outer table graft in
middle fossa surgery. Otolaryngol Head Neck Surg 1994;111:70–75.
28. Schick B, Greess H, Gill S, Pauli E, Iro H. Magnetic resonance imaging
and neuropsychological testing after middle fossa vestibular schwannoma surgery. Otol Neurotol 2008;29:39–45.
29. Thomsen J, Stougaard M, Becker B, Tos M, Jennum P. Middle fossa
approach in vestibular schwannoma surgery. Postoperative hearing
preservation and EEG changes. Acta Otolaryngol 2000;120:517–522.
Semaan et al.: TMEDIC Approach for Repair of Transtemporal Meningoencephalocele