Otology & Neurotology 36:932Y935 Ó 2015, Otology & Neurotology, Inc.
Dilemmas in the Treatment of Concurrent Bilateral Meningoencephalocele and Superior Semicircular Canal Dehiscence *Garrett Locketz, *†Nevo Margalit, *†Lior Gonen, *‡Dan M. Fliss, and *‡Ophir Handzel *Sackler School of Medicine, Tel Aviv University; ÞDepartments of Neurosurgery, and þOtolaryngology, Head, Neck and Maxillofacial Surgery, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
auditory canal, plugging of the eustachian tube orifice, and obliteration of the residual space with an abdominal fat graft. The herniated brain and meninges were amputated, and the tissue present in the attic was not disrupted. Hearing was reconstructed with a two-staged Bone-anchored Hearing Aid procedure to avoid the risk of cerebrospinal fluid leaking through the skin defect of the Bone-anchored Hearing Aid abutment. Conclusion: Temporal bone ME can be associated with asymptomatic SSCD. We illustrate an example of how patients with bilateral pathologies can be managed effectively with good vestibular, auditory, and cosmetic results. Key Words: BilateralVCerebrospinal fluid leakVConcomitantVSemicircular canal dehiscenceVMeningoencephalocele.
Objective: To report on a patient with bilateral meningoencephalocele complicated by bilateral asymptomatic superior semicircular canal dehiscence and discuss dilemmas associated with his successful surgical treatment. Study Design: Case capsule report. Setting: Tertiary academic medical center. Patient: A 56-year-old man with 6 years of progressive conductive hearing loss and recent spontaneous cerebrospinal fluid leak from the right ear diagnosed as having bilateral large temporal bone meningoencephalocele (ME) and concomitant bilateral asymptomatic superior semicircular canal dehiscence (SSCD). Results: The right ME was repaired through the middle fossa approach, and the right SSCD was plugged. To avoid the risk associated with bilaterally plugging the SSCDs, the left ME was sealed by subtotal petrosectomy, blind sac closure of the external
Otol Neurotol 36:932Y935, 2015.
Structural defects in the middle fossa tegmen have been associated with the development of both meningoencephalocele (ME) (1Y4) and superior semicircular canal dehiscence (SSCD) (5Y7). ME may manifest with headache, aural fullness, and conductive hearing loss (3,8). A history of ME with otogenic meningitis or active cerebrospinal fluid (CSF) leak is a strong indication for surgical correction to prevent future bacterial meningitis (9). SSCD is an absence of bone overlying the SSC that exposes the membranous labyrinth to pathologic shunting of pressure and sound (10). The clinical presentation of SSCD syndrome varies considerably, with patients experiencing vestibular symptoms (imbalance, soundand/or pressure-induced nystagmus, vertigo, oscillopsia,
and/or disequilibrium), auditory symptoms (hyperacusis, autophony, aural fullness, conductive hearing loss), or a combination of both (11). Typically, history and physical examination reveal a combination of auditory and/or vestibular symptoms, low-frequency air-bone gap (ABG) with intact acoustic reflexes, and lowered vestibularevoked myogenic potential (VEMP) thresholds. SSCD syndrome is postulated to be caused by decreased impedance within the inner ear because of a ‘‘third mobile window’’ mechanism created by the bony defect (12,13). Nevertheless, positive findings on CT do not always correlate with the presence and severity of SSCD syndrome (14), and it is currently unknown why some SSCDs remain asymptomatic. Recently, a multitude of studies have indicated that SSCD and ME may share a common etiology and that both pathologies have a propensity to occur bilaterally and/or concomitantly (5,6,11,14Y21). Thus, diagnosing one of these pathologies must raise the suspicion for the presence of the other because coexistence may have implications
Address correspondence and reprint requests to Ophir Handzel, M.D., Director of Cochlear Implant Center, Department of Otolaryngology, Head, Neck and Maxillofacial Surgery, Tel-Aviv Sourasky Medical Center, 6 Weitzman St, Tel Aviv, Israel 64239; E-mail: [email protected] The authors disclose no conflicts of interest.
932
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
CONCURRENT BILATERAL ME-SSCD TREATMENT DILEMMAS when surgical treatment is required. Nevertheless, a paucity of literature exists discussing the treatment of bilateral SSCD, and even less has been published regarding management of concurrent unilateral ME and SSCD (22,23). To date, only one case report exists on the repair of bilateral ME complicated by symptomatic SSCD (24). Herein, we present the first report on a patient with bilateral ME and concomitant bilateral asymptomatic SSCD and discuss dilemmas associated with his treatment. CASE PRESENTATION A 56-year-old man presented to another institution after 6 years of progressive bilateral hearing loss with recent rhinorrhea. Mild improvement with hearing aids had been achieved during the previous 2 years without any vestibular symptoms. On otoscopy, the left ear had pinklooking tissue protruding through the tympanic membrane (TM), filling the external auditory canal. This mass was biopsied and confirmed as brain tissue. The right ear had clear fluid in the middle ear visible through an intact TM. Nasal discharge was positive for Beta2-transferrin, and rightsided spontaneous CSF leak was confirmed. Pure-tone audiogram showed bilateral mixed hearing loss. He was referred to our center, where a computed tomography (CT) scan revealed a very large left-sided ME herniating through a dehiscent tegmen tympani and tegmen mastoideum, as well as a right-sided ME (R-ME) herniating through the tegmen tympani into the middle ear, loading and tethering the ossicular chain. CT further revealed large bilateral SSCDs (Fig. 1). Both tegmental defects were not completely approachable through a transmastoid approach. First Dilemma CSF leak is an absolute indication for ME repair to avoid the risk for secondary infection. Unfortunately,
933
our patient initially declined surgical correction and returned with fulminant bacterial meningitis 1 week later. After treatment with full resolution, the patient agreed to surgery, which presented the first dilemmaV how to manage the patient’s asymptomatic right-sided SSCD during the middle fossa approach to correct the right-sided ME. Asymptomatic SSCDs do not require surgical correction, and it is yet unknown what makes some SSCDs symptomatic and others silent. Some have postulated that radiologically diagnosed but asymptomatic SSCDs may actually be functionally ‘‘inactive’’ if the dura overlying the dehiscence patches the defect. It has also been noted that nearly 1.5% of temporal bone specimens have a very thin (G0.1mm) osseous covering over the SSC, which may be misinterpreted as a dehiscence on CT (5). Nevertheless, because of the proximity of the ME to the SSCD, elevating the dura in that area would likely cause a previously inactive SSCD to become symptomatic via either opening a patched third window or disrupting a thin osseous cover that may overlay the SSC. Furthermore, if a previously asymptomatic SSCD is made symptomatic postoperatively, a revision surgery carries a higher risk of permanent sensorineural hearing loss via disruption of the membranous labyrinth. Thus, the right-sided SSCD was plugged during repair of the right-sided ME. A temporal craniotomy was used to access the middle fossa, and the rightsided ME was roofed with a split calvarial bone graft wrapped in temporalis fascia and augmented with a pedicled partial temporalis muscle flap. A large right-sided SSCD was identified and plugged during the same operation (Figs. 2, 3). Postoperatively, his CSF leak resolved and audiograms demonstrated no residual conductive or additional sensorineural hearing loss. Vestibular physiotherapy aided in rehabilitation of the vestibular loss associated with the plugged canal.
FIG. 1. CT images showing right and left superior semicircular canal dehiscences (arrowheads) and right meningoencephalocele herniating into the external ear canal and left meningoencephalocele protruding into the mastoid air space (stars). Otology & Neurotology, Vol. 36, No. 5, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
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G. LOCKETZ ET AL. One year after, bone conduction hearing thresholds had remained unchanged as compared with preoperative testing, indicating that a maximal ABG had been created as a result of the procedure, although this was well rehabilitated by the implanted BAHA.
DISCUSSION
FIG. 2. Intraoperative image of right-sided meningoencephalocele (circled) and superior semicircular canal dehiscence (arrow) via middle fossa approach.
Second Dilemma After the patient’s right-sided procedure, the question of how to address the left-sided ME and SSCD remained. Save for left-sided mixed conductive and sensorineural hearing loss requiring amplification, the patient was asymptomatic without active CSF leak. As the ME completely occluded the external auditory canal, conventional hearing aids were not applicable. Nevertheless, direct exposure of the brain and meninges to the external auditory canal and respiratory system through the eustachian tube and middle ear is associated with an increased risk for otogenic meningitis, indicating the need for surgical correction. Third Dilemma Once the decision was made to repair the left-sided ME, the third dilemma was how to manage the second asymptomatic SSCD. Several studies have shown that plugging bilateral symptomatic SSCDs is associated with prolonged recovery time (18) and up to 50% of patients have ongoing oscillopsia postoperatively (15). Thus, to avoid the risk of bilaterally plugging the SSCDs, we elected to seal the ME through a transmastoid approach. Surgery included subtotal petrosectomy, blind sac closure of the external auditory canal, plugging of the eustachian tube orifice, and obliteration of the residual space with an abdominal fat graft. The herniated brain and meninges were amputated at the level of the tympanic segment of the facial nerve, and the tissue present in the attic was not disrupted. Hearing was reconstructed with a two-stage Bone-anchored Hearing Aid (BAHA) procedure to avoid the risk of CSF leaking through the skin defect of the BAHA abutment. The patient remained without vestibular symptoms postoperatively with good cosmetic results. No nystagmus or eye deviation was noted in response to Valsalva maneuver or positive/negative pressure in the right ear. Bone conduction cervical VEMP thresholds were 15 dB lower on the left than on the right.
Etiology The precise etiologies of SSCD and tegmen dehiscence resulting in ME are open to debate. Many authors have proposed the origin of SSCD to be the effect of postnatal bone development failure (16) because patients generally have a decreased osseous thickness of the squamousal portion of the temporal bone (21), a greater association with tegmen dehiscence (5,6), and a propensity for bilateral dehiscences or thinning of the contralateral tegmen (16). Others have reported that incidence increases with age, suggesting an acquired etiology via microtrauma, increased intracranial pressure, or demineralization (25). Regardless of origin, it is well established that both SSCD and ME commonly occur bilaterally and concomitantly (5,6,11,14Y21). Symptomatology The clinical features SSCD syndrome vary widely, and although false-positive radiographic diagnosis is prevalent, it is still unknown why only some SSCDs are symptomatic. Recently, attempts have been made to associate radiographic and pathologic features of SSCDs to clinical symptoms, although the literature on this topic is somewhat conflicting. The largest and most recent of such studies indicated that larger dehiscences located closer to the ampulla were associated with both auditory symptoms and lower cervical VEMPs, and that larger dehiscences were associated with larger ABGs (11). Although our patient had a rather large SSCD, it is likely that his bilateral conductive hearing loss was caused
FIG. 3. Intraoperative image of right-sided meningoencephalocele (circled) and plugging of right SSCD (arrow).
Otology & Neurotology, Vol. 36, No. 5, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
CONCURRENT BILATERAL ME-SSCD TREATMENT DILEMMAS by the fluid and prolapsed tissue in the right and left ears, respectively. Treatment The goal of treatment in SSCD is to seal the third mobile window created by the bony defect in the tegmen. Historically, this has been accomplished via plugging the defect, resurfacing with a bone graft or cement, or capping with hydroxyapatite cement. A recent meta-analysis of 64 surgical SCCD corrections indicated capping and plugging had significantly higher success rates versus resurfacing and were technically easier to perform (26). This study did not investigate cases of bilateral disease or concomitant ipsilateral ME, and the most successful choice of correction in these cases remains to be determined. Unanswered Questions Because of the limited number of cases, the appropriate management of an asymptomatic SSCD during correction of an ipsilateral ME has yet to be formally investigated. During such a procedure, how does the risk of plugging the asymptomatic SSCD compare with the risk associated with a revision procedure if the SSCD is made symptomatic postoperatively? Is there a critical proximity between an SSCD and a concomitant ME whereby lifting the dura to repair the ME would ultimately make symptomatic an otherwise silent SSCD? Indeed, more data are needed on the symptomatology of bilaterally plugged SSCDs. CONCLUSION This case illustrates the first example in the literature of surgical correction of bilateral ME complicated by bilateral asymptomatic SSCD. Our experience provides an example of how similar patients can be managed effectively with good vestibular, auditory, and cosmetic results. REFERENCES 1. Kutz JW, Husain IA, Isaacson B, Roland PS. Management of spontaneous cerebrospinal fluid otorrhea. Laryngoscope 2008;118: 2195Y9. 2. Leonetti JP, Marzo S, Anderson D, Origitano T, Vukas DD. Spontaneous transtemporal CSF leakage: a study of 51 cases. Ear Nose Throat J 2005;84:702Y4. 3. Nahas Z, Tatlipinar A, Limb CJ, Francis HW. Spontaneous meningoencephalocele of the temporal bone: clinical spectrum and presentation. Arch Otolaryngol Head Neck Surg 2008;134:509Y18. 4. Kaufman B, Yonas H, White RJ, Miller CF 2nd. Acquired middle cranial fossa fistulas: normal pressure and nontraumatic in origin. Neurosurgery 1979;5:466Y72. 5. Crovetto M, Whyte J, Rodriguez OM, Lecumberri I, Martinez C, Elexpuru J. Anatomo-radiological study of the superior semicircular canal dehiscence radiological considerations of superior and posterior semicircular canals. Eur J Radiol 2010;76:167Y72. 6. Nadaraja GS, Gurgel RK, Fischbein NJ, et al. Radiographic evaluation of the tegmen in patients with superior semicircular canal dehiscence. Otol Neurotol 2012;33:1245Y50.
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7. Suryanarayanan R, Lesser TH. ‘‘Honeycomb’’ tegmen: multiple tegmen defects associated with superior semicircular canal dehiscence. J Laryngol Otol 2010;124:560Y3. 8. Semaan MT, Gilpin DA, Hsu DP, Wasman JK, Megerian CA. Transmastoid extradural-intracranial approach for repair of transtemporal meningoencephalocele: a review of 31 consecutive cases. Laryngoscope 2011;121:1765Y72. 9. Gubbels SP, Selden NR, Delashaw JB Jr, McMenomey SO. Spontaneous middle fossa encephalocele and cerebrospinal fluid leakage: diagnosis and management. Otol Neurotol 2007;28: 1131Y9. 10. Minor LB, Solomon D, Zinreich JS, Zee DS. Sound- and/or pressure-induced vertigo due to bone dehiscence of the superior semicircular canal. Arch Otolaryngol Head Neck Surg 1998;124: 249Y58. 11. Niesten ME, Hamberg LM, Silverman JB, et al. Superior canal dehiscence length and location influences clinical presentation and audiometric and cervical vestibular-evoked myogenic potential testing. Audiol Neurootol 2014;19:97Y105. 12. Mikulec AA, McKenna MJ, Ramsey MJ, et al. Superior semicircular canal dehiscence presenting as conductive hearing loss without vertigo. Otol Neurotol 2004;25:121Y9. 13. Minor LB, Carey JP, Cremer PD, Lustig LR, Streubel SO, Ruckenstein MJ. Dehiscence of bone overlying the superior canal as a cause of apparent conductive hearing loss. Otol Neurotol 2003;24: 270Y8. 14. Williamson RA, Vrabec JT, Coker NJ, Sandlin M. Coronal computed tomography prevalence of superior semicircular canal dehiscence. Otolaryngol Head Neck Surg 2003;129:481Y9. 15. Agrawal Y, Minor LB, Schubert MC, Janky KL, Davalos-Bichara M, Carey JP. Second-side surgery in superior canal dehiscence syndrome. Otol Neurotol 2012;33:72Y7. 16. Carey JP, Minor LB, Nager GT. Dehiscence or thinning of bone overlying the superior semicircular canal in a temporal bone survey. Arch Otolaryngol Head Neck Surg 2000;126:137Y47. 17. Cloutier J-F, Belair M, Saliba I. Superior semicircular canal dehiscence: positive predictive value of high-resolution CT scanning. Eur Arch Otorhinolaryngol 2008;265:1455Y60. 18. Niesten ME, McKenna MJ, Grolman W, Lee DJ. Clinical factors associated with prolonged recovery after superior canal dehiscence surgery. Otol Neurotol 2012;33:824Y31. 19. Stimmer H, Hamann KF, Zeiter S, Naumann A, Rummeny EJ. Semicircular canal dehiscence in HR multislice computed tomography: distribution, frequency, and clinical relevance. Eur Arch Otorhinolaryngol 2012;269:475Y80. 20. Zipser BD, Sepahdari AR. Semicircular canal dehiscence. Oper Tech Otolaryngol Head Neck Surg 2014;25:118Y24. 21. Friedland DR, Michel MA. Cranial thickness in superior canal dehiscence syndrome: implications for canal resurfacing surgery. Otol Neurotol 2006;27:346Y54. 22. Lim ZM, Friedland PL, Boeddinghaus R, Thompson A, Rodrigues SJ, Atlas M. Otitic meningitis, superior semicircular canal dehiscence, and encephalocele: a case series. Otol Neurotol 2012;33: 610Y2. 23. Smullen JL, Andrist EC, Gianoli GJ. Superior semicircular canal dehiscence: a new cause of vertigo. J La State Med Soc 1999;151: 397Y400. 24. Mikulec AA, Khan AM, Barker FG, McKenna MJ. Bilateral meningoencephalocele repair complicated by superior semicircular canal dehiscence: case report. Skull Base 2008;18:423Y8. 25. Nadgir RN, Ozonoff A, Devaiah AK, et al. Superior semicircular canal dehiscence: congenital or acquired condition? Am J Neuroradiol 2011;32:947Y9. 26. Vlastarakos PV, Proikas K, Tavoulari E, Kikidis D, Maragoudakis P, Nikolopoulos TP. Efficacy assessment and complications of surgical management for superior semicircular canal dehiscence: a metaanalysis of published interventional studies. Eur Arch Otorhinolaryngol 2009;266:177Y86.
Otology & Neurotology, Vol. 36, No. 5, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
Dilemmas in the Treatment of Concurrent Bilateral Meningoencephalocele and Superior Semicircular Canal Dehiscence *Garrett Locketz, *†Nevo Margalit, *†Lior Gonen, *‡Dan M. Fliss, and *‡Ophir Handzel *Sackler School of Medicine, Tel Aviv University; ÞDepartments of Neurosurgery, and þOtolaryngology, Head, Neck and Maxillofacial Surgery, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
auditory canal, plugging of the eustachian tube orifice, and obliteration of the residual space with an abdominal fat graft. The herniated brain and meninges were amputated, and the tissue present in the attic was not disrupted. Hearing was reconstructed with a two-staged Bone-anchored Hearing Aid procedure to avoid the risk of cerebrospinal fluid leaking through the skin defect of the Bone-anchored Hearing Aid abutment. Conclusion: Temporal bone ME can be associated with asymptomatic SSCD. We illustrate an example of how patients with bilateral pathologies can be managed effectively with good vestibular, auditory, and cosmetic results. Key Words: BilateralVCerebrospinal fluid leakVConcomitantVSemicircular canal dehiscenceVMeningoencephalocele.
Objective: To report on a patient with bilateral meningoencephalocele complicated by bilateral asymptomatic superior semicircular canal dehiscence and discuss dilemmas associated with his successful surgical treatment. Study Design: Case capsule report. Setting: Tertiary academic medical center. Patient: A 56-year-old man with 6 years of progressive conductive hearing loss and recent spontaneous cerebrospinal fluid leak from the right ear diagnosed as having bilateral large temporal bone meningoencephalocele (ME) and concomitant bilateral asymptomatic superior semicircular canal dehiscence (SSCD). Results: The right ME was repaired through the middle fossa approach, and the right SSCD was plugged. To avoid the risk associated with bilaterally plugging the SSCDs, the left ME was sealed by subtotal petrosectomy, blind sac closure of the external
Otol Neurotol 36:932Y935, 2015.
Structural defects in the middle fossa tegmen have been associated with the development of both meningoencephalocele (ME) (1Y4) and superior semicircular canal dehiscence (SSCD) (5Y7). ME may manifest with headache, aural fullness, and conductive hearing loss (3,8). A history of ME with otogenic meningitis or active cerebrospinal fluid (CSF) leak is a strong indication for surgical correction to prevent future bacterial meningitis (9). SSCD is an absence of bone overlying the SSC that exposes the membranous labyrinth to pathologic shunting of pressure and sound (10). The clinical presentation of SSCD syndrome varies considerably, with patients experiencing vestibular symptoms (imbalance, soundand/or pressure-induced nystagmus, vertigo, oscillopsia,
and/or disequilibrium), auditory symptoms (hyperacusis, autophony, aural fullness, conductive hearing loss), or a combination of both (11). Typically, history and physical examination reveal a combination of auditory and/or vestibular symptoms, low-frequency air-bone gap (ABG) with intact acoustic reflexes, and lowered vestibularevoked myogenic potential (VEMP) thresholds. SSCD syndrome is postulated to be caused by decreased impedance within the inner ear because of a ‘‘third mobile window’’ mechanism created by the bony defect (12,13). Nevertheless, positive findings on CT do not always correlate with the presence and severity of SSCD syndrome (14), and it is currently unknown why some SSCDs remain asymptomatic. Recently, a multitude of studies have indicated that SSCD and ME may share a common etiology and that both pathologies have a propensity to occur bilaterally and/or concomitantly (5,6,11,14Y21). Thus, diagnosing one of these pathologies must raise the suspicion for the presence of the other because coexistence may have implications
Address correspondence and reprint requests to Ophir Handzel, M.D., Director of Cochlear Implant Center, Department of Otolaryngology, Head, Neck and Maxillofacial Surgery, Tel-Aviv Sourasky Medical Center, 6 Weitzman St, Tel Aviv, Israel 64239; E-mail: [email protected] The authors disclose no conflicts of interest.
932
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
CONCURRENT BILATERAL ME-SSCD TREATMENT DILEMMAS when surgical treatment is required. Nevertheless, a paucity of literature exists discussing the treatment of bilateral SSCD, and even less has been published regarding management of concurrent unilateral ME and SSCD (22,23). To date, only one case report exists on the repair of bilateral ME complicated by symptomatic SSCD (24). Herein, we present the first report on a patient with bilateral ME and concomitant bilateral asymptomatic SSCD and discuss dilemmas associated with his treatment. CASE PRESENTATION A 56-year-old man presented to another institution after 6 years of progressive bilateral hearing loss with recent rhinorrhea. Mild improvement with hearing aids had been achieved during the previous 2 years without any vestibular symptoms. On otoscopy, the left ear had pinklooking tissue protruding through the tympanic membrane (TM), filling the external auditory canal. This mass was biopsied and confirmed as brain tissue. The right ear had clear fluid in the middle ear visible through an intact TM. Nasal discharge was positive for Beta2-transferrin, and rightsided spontaneous CSF leak was confirmed. Pure-tone audiogram showed bilateral mixed hearing loss. He was referred to our center, where a computed tomography (CT) scan revealed a very large left-sided ME herniating through a dehiscent tegmen tympani and tegmen mastoideum, as well as a right-sided ME (R-ME) herniating through the tegmen tympani into the middle ear, loading and tethering the ossicular chain. CT further revealed large bilateral SSCDs (Fig. 1). Both tegmental defects were not completely approachable through a transmastoid approach. First Dilemma CSF leak is an absolute indication for ME repair to avoid the risk for secondary infection. Unfortunately,
933
our patient initially declined surgical correction and returned with fulminant bacterial meningitis 1 week later. After treatment with full resolution, the patient agreed to surgery, which presented the first dilemmaV how to manage the patient’s asymptomatic right-sided SSCD during the middle fossa approach to correct the right-sided ME. Asymptomatic SSCDs do not require surgical correction, and it is yet unknown what makes some SSCDs symptomatic and others silent. Some have postulated that radiologically diagnosed but asymptomatic SSCDs may actually be functionally ‘‘inactive’’ if the dura overlying the dehiscence patches the defect. It has also been noted that nearly 1.5% of temporal bone specimens have a very thin (G0.1mm) osseous covering over the SSC, which may be misinterpreted as a dehiscence on CT (5). Nevertheless, because of the proximity of the ME to the SSCD, elevating the dura in that area would likely cause a previously inactive SSCD to become symptomatic via either opening a patched third window or disrupting a thin osseous cover that may overlay the SSC. Furthermore, if a previously asymptomatic SSCD is made symptomatic postoperatively, a revision surgery carries a higher risk of permanent sensorineural hearing loss via disruption of the membranous labyrinth. Thus, the right-sided SSCD was plugged during repair of the right-sided ME. A temporal craniotomy was used to access the middle fossa, and the rightsided ME was roofed with a split calvarial bone graft wrapped in temporalis fascia and augmented with a pedicled partial temporalis muscle flap. A large right-sided SSCD was identified and plugged during the same operation (Figs. 2, 3). Postoperatively, his CSF leak resolved and audiograms demonstrated no residual conductive or additional sensorineural hearing loss. Vestibular physiotherapy aided in rehabilitation of the vestibular loss associated with the plugged canal.
FIG. 1. CT images showing right and left superior semicircular canal dehiscences (arrowheads) and right meningoencephalocele herniating into the external ear canal and left meningoencephalocele protruding into the mastoid air space (stars). Otology & Neurotology, Vol. 36, No. 5, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
934
G. LOCKETZ ET AL. One year after, bone conduction hearing thresholds had remained unchanged as compared with preoperative testing, indicating that a maximal ABG had been created as a result of the procedure, although this was well rehabilitated by the implanted BAHA.
DISCUSSION
FIG. 2. Intraoperative image of right-sided meningoencephalocele (circled) and superior semicircular canal dehiscence (arrow) via middle fossa approach.
Second Dilemma After the patient’s right-sided procedure, the question of how to address the left-sided ME and SSCD remained. Save for left-sided mixed conductive and sensorineural hearing loss requiring amplification, the patient was asymptomatic without active CSF leak. As the ME completely occluded the external auditory canal, conventional hearing aids were not applicable. Nevertheless, direct exposure of the brain and meninges to the external auditory canal and respiratory system through the eustachian tube and middle ear is associated with an increased risk for otogenic meningitis, indicating the need for surgical correction. Third Dilemma Once the decision was made to repair the left-sided ME, the third dilemma was how to manage the second asymptomatic SSCD. Several studies have shown that plugging bilateral symptomatic SSCDs is associated with prolonged recovery time (18) and up to 50% of patients have ongoing oscillopsia postoperatively (15). Thus, to avoid the risk of bilaterally plugging the SSCDs, we elected to seal the ME through a transmastoid approach. Surgery included subtotal petrosectomy, blind sac closure of the external auditory canal, plugging of the eustachian tube orifice, and obliteration of the residual space with an abdominal fat graft. The herniated brain and meninges were amputated at the level of the tympanic segment of the facial nerve, and the tissue present in the attic was not disrupted. Hearing was reconstructed with a two-stage Bone-anchored Hearing Aid (BAHA) procedure to avoid the risk of CSF leaking through the skin defect of the BAHA abutment. The patient remained without vestibular symptoms postoperatively with good cosmetic results. No nystagmus or eye deviation was noted in response to Valsalva maneuver or positive/negative pressure in the right ear. Bone conduction cervical VEMP thresholds were 15 dB lower on the left than on the right.
Etiology The precise etiologies of SSCD and tegmen dehiscence resulting in ME are open to debate. Many authors have proposed the origin of SSCD to be the effect of postnatal bone development failure (16) because patients generally have a decreased osseous thickness of the squamousal portion of the temporal bone (21), a greater association with tegmen dehiscence (5,6), and a propensity for bilateral dehiscences or thinning of the contralateral tegmen (16). Others have reported that incidence increases with age, suggesting an acquired etiology via microtrauma, increased intracranial pressure, or demineralization (25). Regardless of origin, it is well established that both SSCD and ME commonly occur bilaterally and concomitantly (5,6,11,14Y21). Symptomatology The clinical features SSCD syndrome vary widely, and although false-positive radiographic diagnosis is prevalent, it is still unknown why only some SSCDs are symptomatic. Recently, attempts have been made to associate radiographic and pathologic features of SSCDs to clinical symptoms, although the literature on this topic is somewhat conflicting. The largest and most recent of such studies indicated that larger dehiscences located closer to the ampulla were associated with both auditory symptoms and lower cervical VEMPs, and that larger dehiscences were associated with larger ABGs (11). Although our patient had a rather large SSCD, it is likely that his bilateral conductive hearing loss was caused
FIG. 3. Intraoperative image of right-sided meningoencephalocele (circled) and plugging of right SSCD (arrow).
Otology & Neurotology, Vol. 36, No. 5, 2015
Copyright © 2015 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
CONCURRENT BILATERAL ME-SSCD TREATMENT DILEMMAS by the fluid and prolapsed tissue in the right and left ears, respectively. Treatment The goal of treatment in SSCD is to seal the third mobile window created by the bony defect in the tegmen. Historically, this has been accomplished via plugging the defect, resurfacing with a bone graft or cement, or capping with hydroxyapatite cement. A recent meta-analysis of 64 surgical SCCD corrections indicated capping and plugging had significantly higher success rates versus resurfacing and were technically easier to perform (26). This study did not investigate cases of bilateral disease or concomitant ipsilateral ME, and the most successful choice of correction in these cases remains to be determined. Unanswered Questions Because of the limited number of cases, the appropriate management of an asymptomatic SSCD during correction of an ipsilateral ME has yet to be formally investigated. During such a procedure, how does the risk of plugging the asymptomatic SSCD compare with the risk associated with a revision procedure if the SSCD is made symptomatic postoperatively? Is there a critical proximity between an SSCD and a concomitant ME whereby lifting the dura to repair the ME would ultimately make symptomatic an otherwise silent SSCD? Indeed, more data are needed on the symptomatology of bilaterally plugged SSCDs. CONCLUSION This case illustrates the first example in the literature of surgical correction of bilateral ME complicated by bilateral asymptomatic SSCD. Our experience provides an example of how similar patients can be managed effectively with good vestibular, auditory, and cosmetic results. REFERENCES 1. Kutz JW, Husain IA, Isaacson B, Roland PS. Management of spontaneous cerebrospinal fluid otorrhea. Laryngoscope 2008;118: 2195Y9. 2. Leonetti JP, Marzo S, Anderson D, Origitano T, Vukas DD. Spontaneous transtemporal CSF leakage: a study of 51 cases. Ear Nose Throat J 2005;84:702Y4. 3. Nahas Z, Tatlipinar A, Limb CJ, Francis HW. Spontaneous meningoencephalocele of the temporal bone: clinical spectrum and presentation. Arch Otolaryngol Head Neck Surg 2008;134:509Y18. 4. Kaufman B, Yonas H, White RJ, Miller CF 2nd. Acquired middle cranial fossa fistulas: normal pressure and nontraumatic in origin. Neurosurgery 1979;5:466Y72. 5. Crovetto M, Whyte J, Rodriguez OM, Lecumberri I, Martinez C, Elexpuru J. Anatomo-radiological study of the superior semicircular canal dehiscence radiological considerations of superior and posterior semicircular canals. Eur J Radiol 2010;76:167Y72. 6. Nadaraja GS, Gurgel RK, Fischbein NJ, et al. Radiographic evaluation of the tegmen in patients with superior semicircular canal dehiscence. Otol Neurotol 2012;33:1245Y50.
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Otology & Neurotology, Vol. 36, No. 5, 2015
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