- Email: [email protected]
Bilateral Superior Semicircular Canal Dehiscence Associated with Ehlers-Danlos Syndrome: A Report of 2 Cases
Case Report
Bilateral Superior Semicircular Canal Dehiscence Associated with Ehlers-Danlos Syndrome: A Report of 2 Cases Komal Preet1, Methma Udawatta1, Courtney Duong1, Quinton Gopen2, Isaac Yang1-7
Key words Case report - Ehlers-Danlos syndrome - Hypermobility - Middle fossa craniotomy - Superior semicircular canal dehiscence -
Abbreviations and Acronyms CT: Computed tomography EDS: Ehlers-Danlos syndrome HT: Hypermobility type SSCD: Superior semicircular canal dehiscence VEMP: Vestibular evoked myogenic potential From the Departments of 1Neurosurgery, 2Head and Neck Surgery, and 3Radiation Oncology, 4Office of the Patient Experience, and 5UCLA Jonsson Comprehensive Cancer Center, Ronald Reagan UCLA Medical Center, Los Angeles, California; and 6Department of Neurosurgery and 7Los Angeles Biomedical Research Institute (LA BioMed), HarborUCLA Medical Center, Torrance, California, USA To whom correspondence should be addressed: Isaac Yang, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2019) 122:161-164. https://doi.org/10.1016/j.wneu.2018.10.126 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
INTRODUCTION Superior semicircular canal dehiscence (SSCD) is the development of a pathologic third window between the brain and inner ear due to the absence or thinning of the tegmen tympani.1-4 Patients with SSCD typically present in the fourth or fifth decade with varying degrees of visual, auditory, and vestibular symptoms.2,5,6 The prevalence of this dehiscence has been reported to range from 0.5% to 12.4%.6-11 Vestibular evoked myogenic potentials (VEMPs) are used during initial diagnosis because patients are typically more sensitive to lower intensity thresholds.4,12 Although audiometric testing aids in SSCD diagnosis, confirmation of dehiscence is best visualized via a highresolution temporal computed tomography (CT) scan.2-4 One method to treat SSCD is to use the middle cranial fossa
- BACKGROUND:
Superior semicircular canal dehiscence (SSCD) is a rare bony defect in the petrosal temporal bone, creating a new opening between the inner ear and middle cranial fossa. Ehlers-Danlos syndrome (EDS) is an inherited connective tissue disorder characterized by a defect in collagen synthesis. Patients with EDS are more likely to have bony abnormalities, which may predispose them to developing SSCD.
- CASE
DESCRIPTION: We report the cases of 2 women with history of EDS hypermobility type (HT). Both patients presented with bilateral auditory and vestibular symptoms, and computed tomography scan confirmed the presence of bilateral dehiscence in their superior semicircular canals. They underwent elective surgical repair via middle fossa craniotomy and report improvement in their symptoms.
- CONCLUSIONS:
Because of the rarity of both diseases and their pathophysiology, a history of EDS may predispose an individual to developing SSCD. Although further research is necessary, this report aims to improve clinical screening of patients with EDS HT by suggesting an auditory and vestibular evaluation and assessment of pertinent bony abnormalities.
technique, which allows greater visualization of the dehiscence than the transmastoid approach.13-15 Ehlers-Danlos syndrome (EDS) is a genetic disorder affecting 1 in 5000 people and results from a defect in collagen synthesis, leading to generalized tissue fragility.16-18 The International EDS Consortium recently proposed 13 subtypes of EDS. The most common is EDS hypermobility type (HT), which is characterized by joint hypermobility and smooth appearance of skin.19-23 EDS is often underdiagnosed and inadequately managed, which can lead to severe disability if untreated.19,22-26 Dolan et al.27 found that patients with EDS were more likely to have abnormal bony formations and lower bone mass when compared with agematched controls. Therefore, it is possible that patients with EDS wear out their arcuate eminence, creating an SSCD. Our laboratory previously reported on a woman with bilateral SSCD and EDS HT, who will be referred to as patient 1.16 The current study presents a comparison of patient 1 and patient 2, who was also
WORLD NEUROSURGERY 122: 161-164, FEBRUARY 2019
diagnosed with bilateral SSCD and EDS HT. They were seen by the same neurosurgeon and otolaryngologist at a single academic institution. Both patients provided consent to publish this report, and institutional review board approval was obtained.
CASE PRESENTATION 1 History and Examination Patient 1 is a 52-year-old woman with chronic migraines and dysautonomia. She presented with over a 15-year history of tinnitus, bilateral hyperacusis, dizziness, and internal amplification of chewing. Episodes of vertigo were triggered by loud sounds and quick head movements, which further aggravated her migraines. Pure tone air conduction and bone conduction showed a 20-dB air-bone gap in the left ear at 250 Hz. She had bilateral symptoms that were worse on her right side and had undergone surgical repair of her right SSCD with a bone wax plug. On follow-up, she reported some improvement in her
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TWO CASES OF SSCD ASSOCIATED WITH EDS
recognition threshold was determined to be 5 dB bilaterally via audiometric testing, with a speech discrimination score of 100% at 30 dB. Vestibular testing indicated symmetrical cervical VEMP responses on both sides at expected latencies, with a slightly reduced threshold down to 85 dB. High-resolution temporal CT scan indicated significantly thinned covering of the left semicircular canal (Figure 1).
Figure 1. Patient 2 is a 36-year-old woman presenting with multiple auditory and vestibular symptoms, including hyperacusis, tinnitus, and vertigo. High-resolution computed tomography scan of her left temporal bone shows her left superior semicircular canal. The white arrow indicates thinning of arcuate eminence. L, left.
episodes of dizziness, with no significant changes in hearing. Her speech recognition threshold was measured to be 15 dB bilaterally, with a word recognition score of 100% on both sides at 50 dB. Cervical VEMP results were in the normal range, with a slightly reduced threshold down to 95 dB. A high-resolution temporal CT scan revealed the dehiscent segment spanning 4 mm along the left superior-most aspect of her semicircular canal and grossly stable bone graft over her right SSCD postrepair. Surgery and Follow-Up The patient was placed in a supine position with her head turned approximately 35 to expose the left side. A minimally invasive keyhole preauricular infratemporal approach was used for middle fossa craniotomy. A preoperative CT scan was performed using a stereotactic frame. Images were reconstructed to identify coordinates for BrainLab neuronavigation (Munich, Germany) during surgery. Microdissection of the middle cranial fossa floor revealed the arcuate eminence and the location of her left SSCD. A moist micro-cottonoid was used to secure warm bone wax medially to the defect, and then directly onto the SSCD. Harvested bone from the initial craniectomy was thinned and shaped to an appropriate size and placed within the bone wax. After this, a
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heliostat matrix, followed by fibrin sealant, was placed over the entire area to support the repair. The craniotomy was closed in a standard fashion. Patient 1 tolerated the operation well without complications. She was seen 6 days postsurgery and reported nausea and bruising to her stomach and left arm. During both her 1- and 3-month follow-up visits, she noted improvements in her dizziness, but she does experience vertigo with car rides. She also reports fatigue, migraines, and recurring night sweats, and cites concern about her dysautonomia.
CASE PRESENTATION 2 History and Examination Patient 2 is a 36-year-old woman who presented with complaints of bilateral hyperacusis and daily episodes of dizziness for almost a year. She also noted tinnitus, disequilibrium, and internal amplification of sounds made by eye movements. Her symptoms were worse on her left side. She underwent vestibular therapy for 6 weeks, after which she noted that her balance improved, but her other symptoms persisted. Air and bone conductive audiometry revealed no significant air-bone gap. Pure tone thresholds indicated normal hearing sensitivity in both ears. Her speech
Surgery and Follow-Up Patient 2 underwent a left-sided middle fossa craniotomy, as previously described in patient 1, via a keyhole preauricular infratemporal approach. Stereotactic CT images were uploaded into BrainLab, and a similar approach was used to definitively repair her SSCD, via warm bone wax, harvested bone, heliostat matrix, and a fibrin sealant. She tolerated the operation without complications and was discharged in stable condition. At her follow-up visit 6 days postsurgery, she reported vision problems, but noted improvement in her left-sided hyperacusis and autophony. Three months postsurgery, her dizziness had decreased significantly. She still reports right-sided symptoms, including pulsatile tinnitus and hyperacusis, and has been scheduled for a right SSCD repair. DISCUSSION EDS is a collection of genetically and clinically diverse connective tissue disorders.21 Although specific mutations have been isolated for most subtypes, the genetic basis for HT is still to be identified.21 Mutations in the Tenascin-X (TN-X) gene have been noted in a small number of patients with EDS HT. These reduced levels of functional tenascin-x affect the organization of collagen and elastic fibers that support connective tissue.20,28 Patients, however, regardless of EDS subtype, share similar physical characteristics, namely skin extensibility, joint hypermobility, and tissue fragility. Like patients with SSCD, they may report headache and dizziness, but vestibular and auditory symptoms are rare in EDS HT.29 SSCD syndrome has gained increasing recognition as a possible cause of auditory and vestibular symptoms. Although its etiology remains unclear, the development
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.10.126
CASE REPORT KOMAL PREET ET AL.
of a pathologic third window results in endolymphatic shunting toward the bony defect. This can lead to various symptoms, including conductive hearing loss, pulsatile tinnitus, and vertigo. Both patients presented with bilateral symptoms that began in adulthood. There were differences in laterality: the symptoms of patient 1 were worse on the right side, whereas the symptoms of patient 2 were worse on the left side. On initial presentation, audiometry revealed an air-bone gap in patient 1, but not in patient 2. Both patients elected to have surgical intervention, which resulted in decreased dizziness and overall symptom improvement. Numerous hypotheses have been suggested for the development of acquired SSCD, including trauma, osteopenia, and elevated intracranial pressure.30 However, the prevalence of SSCD in children suggests a congenital etiology, resulting in thinning of the tegmen tympani.31,32 This can predispose individuals to developing a dehiscence via the 2-hit phenomenon, such as through subsequent trauma.30 Furthermore, because collagen is a major component of bony matrix proteins, it is possible that patients with EDS may have more fragile bones. This is further supported by the correlation between hypermobility and reduced bone density.27,33 However, further research is necessary to understand EDS HT pathophysiology and its potential correlation with SSCD.
CONCLUSIONS In this report, we present 2 patients with bilateral SSCD and EDS HT. Because of their rarity and proposed pathologic mechanisms, we hypothesize that a history of EDS may predispose individuals to developing SSCD. As such, patients with EDS should be evaluated for pertinent bony abnormalities and auditory and vestibular symptoms. However, further research is required on their potential relationship. REFERENCES 1. Thomson S, Madani G. The windows of the inner ear. Clin Radiol. 2014;69:e146-e152. 2. Zhou G, Gopen Q, Poe DS. Clinical and diagnostic characterization of canal dehiscence
TWO CASES OF SSCD ASSOCIATED WITH EDS
syndrome: a great otologic mimicker. Otol Neurotol. 2007;28:920-926. 3. Russo JE, Crowson MG, DeAngelo EJ, Belden CJ, Saunders JE. Posterior semicircular canal dehiscence: CT prevalence and clinical symptoms. Otol Neurotol. 2014;35:310-314. 4. Brandolini C, Modugno GC, Pirodda A. Dehiscence of the superior semicircular canal: a review of the literature on its possible pathogenic explanations. Eur Arch Otorhinolaryngol. 2014;271: 435-437. 5. Yew A, Zarinkhou G, Spasic M, Trang A, Gopen Q, Yang I. Characteristics and management of superior semicircular canal dehiscence. J Neurol Surg B Skull Base. 2012;73:365-370. 6. McEvoy TP, Mikulec AA, Armbrecht ES, Lowe ME. Quantification of hearing loss associated with superior semi-circular canal dehiscence. Am J Otolaryngol. 2013;34:345-349. 7. Lee YH, Rivas-Rodriguez F, Song JJ, Yang KS, Mukherji SK. The prevalence of superior semicircular canal dehiscence in conductive and mixed hearing loss in the absence of other pathology using submillimetric temporal bone computed tomography. J Comput Assist Tomogr. 2014;38: 190-195. 8. Williamson RA, Vrabec JT, Coker NJ, Sandlin M. Coronal computed tomography prevalence of superior semicircular canal dehiscence. Otolaryngol Head Neck Surg. 2003;129:481-489. 9. Ceylan N, Bayraktaroglu S, Alper H, Savas¸ R, Bilgen C, Kirazli T, et al. CT imaging of superior semicircular canal dehiscence: added value of reformatted images. Acta Otolaryngol. 2010;130: 996-1001. 10. 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;269:475-480. 11. 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;126:137-147. 12. Milojcic R, Guinan JJ Jr, Rauch SD, Herrmann BS. Vestibular evoked myogenic potentials in patients with superior semicircular canal dehiscence. Otol Neurotol. 2013;34:360-367. 13. Nguyen T, Lagman C, Sheppard JP, Romiyo P, Duong C, Prashant GN, et al. Middle cranial fossa approach for the repair of superior semicircular canal dehiscence is associated with greater symptom resolution compared to transmastoid approach. Acta Neurochir (Wien). 2018;160: 1219-1224. 14. 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 meta-analysis of published interventional studies. Eur Arch Otorhinolaryngol. 2009; 266:177-186.
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15. Fiorino F, Barbieri F, Pizzini FB, Beltramello A. A dehiscent superior semicircular canal may be plugged and resurfaced via the transmastoid route. Otol Neurotol. 2010;31:136-139. 16. Chung LK, Lagman C, Nagasawa DT, Gopen Q, Yang I. Superior semicircular canal dehiscence in a patient with Ehlers-Danlos syndrome: a case report. Cureus. 2017;9:e1141. 17. Ehlers-Danlos Syndrome. Genetics Home Reference. Available at: https://ghr.nlm.nih.gov/condition/ehlersdanlos-syndrome. 2017. Accessed June 15, 2018. 18. Parapia LA, Jackson C. Ehlers-Danlos syndrome–a historical review. Br J Haematol. 2008; 141:32-35. 19. Brady AF, Demirdas S, Fournel-Gigleux S, Ghali N, Giunta C, Kapferer-Seebacher I, et al. The Ehlers-Danlos syndromes, rare types. Am J Med Genet C Semin Med Genet. 2017;175:70-115. 20. De Paepe A, Malfait F. The Ehlers-Danlos syndrome, a disorder with many faces. Clin Genet. 2012;82:1-11. 21. Malfait F, Francomano C, Byers P, Belmont J, Berglund B, Black J, et al. The 2017 international classification of the Ehlers-Danlos syndromes. Am J Med Genet C Semin Med Genet. 2017; 175:8-26. 22. Beighton P, De Paepe A, Steinmann B, Tsipouras P, Wenstrup RJ. Ehlers-Danlos syndromes: revised nosology, Villefranche, 1997. Ehlers-Danlos National Foundation (USA) and Ehlers-Danlos Support Group (UK). Am J Med Genet. 1998;77:31-37. 23. Sobey G. Ehlers-Danlos syndrome: how to diagnose and when to perform genetic tests. Arch Dis Child. 2015;100:57-61. 24. Eagleton MJ. Arterial complications of vascular Ehlers-Danlos syndrome. J Vasc Surg. 2016;64: 1869-1880. 25. Gazit Y, Jacob G, Grahame R. Ehlers-Danlos syndrome-hypermobility type: a much neglected multisystemic disorder. Rambam Maimonides Med J. 2016;7. 26. Shirley ED, Demaio M, Bodurtha J. Ehlers-Danlos syndrome in orthopaedics: etiology, diagnosis, and treatment implications. Sports Health. 2012;4: 394-403. 27. Dolan AL, Arden NK, Grahame R, Spector TD. Assessment of bone in Ehlers Danlos syndrome by ultrasound and densitometry. Ann Rheum Dis. 1998; 57:630-633. 28. Kaufman CS, Butler MG. Mutation in TNXB gene causes moderate to severe Ehlers-Danlos syndrome. World J Med Genet. 2016;6:17-21. 29. Savasta S, Merli P, Ruggieri M, Bianchi L, Sparta MV. Ehlers-Danlos syndrome and neurological features: a review. Childs Nerv Syst. 2011;27: 365-371. 30. Bi WL, Brewster R, Poe D, Vernick D, Lee DJ, Eduardo Corrales C, et al. Superior semicircular
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canal dehiscence syndrome. J Neurosurg. 2017;127: 1268-1276. 31. Sugihara EM, Babu SC, Kitsko DJ, Haupert MS, Thottam PJ. Incidence of pediatric superior semicircular canal dehiscence and inner ear anomalies: a large multicenter review. Otol Neurotol. 2016;37: 1370-1375. 32. Sood D, Rana L, Chauhan R, Shukla R, Nandolia K. Superior semicircular canal dehiscence: a new perspective. Eur J Radiol Open. 2017;4:144-146. 33. Eller-Vainicher C, Bassotti A, Imeraj A, Cairoli E, Ulivieri FM, Cortini F, et al. Bone
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TWO CASES OF SSCD ASSOCIATED WITH EDS
involvement in adult patients affected with Ehlers-Danlos syndrome. Osteoporos Int. 2016;27: 2525-2531.
The sponsors had no role in the design or conduct of this research. Received 15 July 2018; accepted 19 October 2018 Citation: World Neurosurg. (2019) 122:161-164. https://doi.org/10.1016/j.wneu.2018.10.126
Conflict of interest statement: M. Udawatta is supported by a David Geffen Medical Scholarship. I. Yang is supported by the UCLA Visionary Ball Fund Grant, UCLA Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research Scholars in Translational Medicine Program Award, Jason Dessel Memorial Seed Grant, UCLA Honberger Endowment Brain Tumor Research Seed Grant, and Stop Cancer (US) Research Career Development Award.
Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.10.126
Bilateral Superior Semicircular Canal Dehiscence Associated with Ehlers-Danlos Syndrome: A Report of 2 Cases Komal Preet1, Methma Udawatta1, Courtney Duong1, Quinton Gopen2, Isaac Yang1-7
Key words Case report - Ehlers-Danlos syndrome - Hypermobility - Middle fossa craniotomy - Superior semicircular canal dehiscence -
Abbreviations and Acronyms CT: Computed tomography EDS: Ehlers-Danlos syndrome HT: Hypermobility type SSCD: Superior semicircular canal dehiscence VEMP: Vestibular evoked myogenic potential From the Departments of 1Neurosurgery, 2Head and Neck Surgery, and 3Radiation Oncology, 4Office of the Patient Experience, and 5UCLA Jonsson Comprehensive Cancer Center, Ronald Reagan UCLA Medical Center, Los Angeles, California; and 6Department of Neurosurgery and 7Los Angeles Biomedical Research Institute (LA BioMed), HarborUCLA Medical Center, Torrance, California, USA To whom correspondence should be addressed: Isaac Yang, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2019) 122:161-164. https://doi.org/10.1016/j.wneu.2018.10.126 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2018 Elsevier Inc. All rights reserved.
INTRODUCTION Superior semicircular canal dehiscence (SSCD) is the development of a pathologic third window between the brain and inner ear due to the absence or thinning of the tegmen tympani.1-4 Patients with SSCD typically present in the fourth or fifth decade with varying degrees of visual, auditory, and vestibular symptoms.2,5,6 The prevalence of this dehiscence has been reported to range from 0.5% to 12.4%.6-11 Vestibular evoked myogenic potentials (VEMPs) are used during initial diagnosis because patients are typically more sensitive to lower intensity thresholds.4,12 Although audiometric testing aids in SSCD diagnosis, confirmation of dehiscence is best visualized via a highresolution temporal computed tomography (CT) scan.2-4 One method to treat SSCD is to use the middle cranial fossa
- BACKGROUND:
Superior semicircular canal dehiscence (SSCD) is a rare bony defect in the petrosal temporal bone, creating a new opening between the inner ear and middle cranial fossa. Ehlers-Danlos syndrome (EDS) is an inherited connective tissue disorder characterized by a defect in collagen synthesis. Patients with EDS are more likely to have bony abnormalities, which may predispose them to developing SSCD.
- CASE
DESCRIPTION: We report the cases of 2 women with history of EDS hypermobility type (HT). Both patients presented with bilateral auditory and vestibular symptoms, and computed tomography scan confirmed the presence of bilateral dehiscence in their superior semicircular canals. They underwent elective surgical repair via middle fossa craniotomy and report improvement in their symptoms.
- CONCLUSIONS:
Because of the rarity of both diseases and their pathophysiology, a history of EDS may predispose an individual to developing SSCD. Although further research is necessary, this report aims to improve clinical screening of patients with EDS HT by suggesting an auditory and vestibular evaluation and assessment of pertinent bony abnormalities.
technique, which allows greater visualization of the dehiscence than the transmastoid approach.13-15 Ehlers-Danlos syndrome (EDS) is a genetic disorder affecting 1 in 5000 people and results from a defect in collagen synthesis, leading to generalized tissue fragility.16-18 The International EDS Consortium recently proposed 13 subtypes of EDS. The most common is EDS hypermobility type (HT), which is characterized by joint hypermobility and smooth appearance of skin.19-23 EDS is often underdiagnosed and inadequately managed, which can lead to severe disability if untreated.19,22-26 Dolan et al.27 found that patients with EDS were more likely to have abnormal bony formations and lower bone mass when compared with agematched controls. Therefore, it is possible that patients with EDS wear out their arcuate eminence, creating an SSCD. Our laboratory previously reported on a woman with bilateral SSCD and EDS HT, who will be referred to as patient 1.16 The current study presents a comparison of patient 1 and patient 2, who was also
WORLD NEUROSURGERY 122: 161-164, FEBRUARY 2019
diagnosed with bilateral SSCD and EDS HT. They were seen by the same neurosurgeon and otolaryngologist at a single academic institution. Both patients provided consent to publish this report, and institutional review board approval was obtained.
CASE PRESENTATION 1 History and Examination Patient 1 is a 52-year-old woman with chronic migraines and dysautonomia. She presented with over a 15-year history of tinnitus, bilateral hyperacusis, dizziness, and internal amplification of chewing. Episodes of vertigo were triggered by loud sounds and quick head movements, which further aggravated her migraines. Pure tone air conduction and bone conduction showed a 20-dB air-bone gap in the left ear at 250 Hz. She had bilateral symptoms that were worse on her right side and had undergone surgical repair of her right SSCD with a bone wax plug. On follow-up, she reported some improvement in her
www.WORLDNEUROSURGERY.org
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TWO CASES OF SSCD ASSOCIATED WITH EDS
recognition threshold was determined to be 5 dB bilaterally via audiometric testing, with a speech discrimination score of 100% at 30 dB. Vestibular testing indicated symmetrical cervical VEMP responses on both sides at expected latencies, with a slightly reduced threshold down to 85 dB. High-resolution temporal CT scan indicated significantly thinned covering of the left semicircular canal (Figure 1).
Figure 1. Patient 2 is a 36-year-old woman presenting with multiple auditory and vestibular symptoms, including hyperacusis, tinnitus, and vertigo. High-resolution computed tomography scan of her left temporal bone shows her left superior semicircular canal. The white arrow indicates thinning of arcuate eminence. L, left.
episodes of dizziness, with no significant changes in hearing. Her speech recognition threshold was measured to be 15 dB bilaterally, with a word recognition score of 100% on both sides at 50 dB. Cervical VEMP results were in the normal range, with a slightly reduced threshold down to 95 dB. A high-resolution temporal CT scan revealed the dehiscent segment spanning 4 mm along the left superior-most aspect of her semicircular canal and grossly stable bone graft over her right SSCD postrepair. Surgery and Follow-Up The patient was placed in a supine position with her head turned approximately 35 to expose the left side. A minimally invasive keyhole preauricular infratemporal approach was used for middle fossa craniotomy. A preoperative CT scan was performed using a stereotactic frame. Images were reconstructed to identify coordinates for BrainLab neuronavigation (Munich, Germany) during surgery. Microdissection of the middle cranial fossa floor revealed the arcuate eminence and the location of her left SSCD. A moist micro-cottonoid was used to secure warm bone wax medially to the defect, and then directly onto the SSCD. Harvested bone from the initial craniectomy was thinned and shaped to an appropriate size and placed within the bone wax. After this, a
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heliostat matrix, followed by fibrin sealant, was placed over the entire area to support the repair. The craniotomy was closed in a standard fashion. Patient 1 tolerated the operation well without complications. She was seen 6 days postsurgery and reported nausea and bruising to her stomach and left arm. During both her 1- and 3-month follow-up visits, she noted improvements in her dizziness, but she does experience vertigo with car rides. She also reports fatigue, migraines, and recurring night sweats, and cites concern about her dysautonomia.
CASE PRESENTATION 2 History and Examination Patient 2 is a 36-year-old woman who presented with complaints of bilateral hyperacusis and daily episodes of dizziness for almost a year. She also noted tinnitus, disequilibrium, and internal amplification of sounds made by eye movements. Her symptoms were worse on her left side. She underwent vestibular therapy for 6 weeks, after which she noted that her balance improved, but her other symptoms persisted. Air and bone conductive audiometry revealed no significant air-bone gap. Pure tone thresholds indicated normal hearing sensitivity in both ears. Her speech
Surgery and Follow-Up Patient 2 underwent a left-sided middle fossa craniotomy, as previously described in patient 1, via a keyhole preauricular infratemporal approach. Stereotactic CT images were uploaded into BrainLab, and a similar approach was used to definitively repair her SSCD, via warm bone wax, harvested bone, heliostat matrix, and a fibrin sealant. She tolerated the operation without complications and was discharged in stable condition. At her follow-up visit 6 days postsurgery, she reported vision problems, but noted improvement in her left-sided hyperacusis and autophony. Three months postsurgery, her dizziness had decreased significantly. She still reports right-sided symptoms, including pulsatile tinnitus and hyperacusis, and has been scheduled for a right SSCD repair. DISCUSSION EDS is a collection of genetically and clinically diverse connective tissue disorders.21 Although specific mutations have been isolated for most subtypes, the genetic basis for HT is still to be identified.21 Mutations in the Tenascin-X (TN-X) gene have been noted in a small number of patients with EDS HT. These reduced levels of functional tenascin-x affect the organization of collagen and elastic fibers that support connective tissue.20,28 Patients, however, regardless of EDS subtype, share similar physical characteristics, namely skin extensibility, joint hypermobility, and tissue fragility. Like patients with SSCD, they may report headache and dizziness, but vestibular and auditory symptoms are rare in EDS HT.29 SSCD syndrome has gained increasing recognition as a possible cause of auditory and vestibular symptoms. Although its etiology remains unclear, the development
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.10.126
CASE REPORT KOMAL PREET ET AL.
of a pathologic third window results in endolymphatic shunting toward the bony defect. This can lead to various symptoms, including conductive hearing loss, pulsatile tinnitus, and vertigo. Both patients presented with bilateral symptoms that began in adulthood. There were differences in laterality: the symptoms of patient 1 were worse on the right side, whereas the symptoms of patient 2 were worse on the left side. On initial presentation, audiometry revealed an air-bone gap in patient 1, but not in patient 2. Both patients elected to have surgical intervention, which resulted in decreased dizziness and overall symptom improvement. Numerous hypotheses have been suggested for the development of acquired SSCD, including trauma, osteopenia, and elevated intracranial pressure.30 However, the prevalence of SSCD in children suggests a congenital etiology, resulting in thinning of the tegmen tympani.31,32 This can predispose individuals to developing a dehiscence via the 2-hit phenomenon, such as through subsequent trauma.30 Furthermore, because collagen is a major component of bony matrix proteins, it is possible that patients with EDS may have more fragile bones. This is further supported by the correlation between hypermobility and reduced bone density.27,33 However, further research is necessary to understand EDS HT pathophysiology and its potential correlation with SSCD.
CONCLUSIONS In this report, we present 2 patients with bilateral SSCD and EDS HT. Because of their rarity and proposed pathologic mechanisms, we hypothesize that a history of EDS may predispose individuals to developing SSCD. As such, patients with EDS should be evaluated for pertinent bony abnormalities and auditory and vestibular symptoms. However, further research is required on their potential relationship. REFERENCES 1. Thomson S, Madani G. The windows of the inner ear. Clin Radiol. 2014;69:e146-e152. 2. Zhou G, Gopen Q, Poe DS. Clinical and diagnostic characterization of canal dehiscence
TWO CASES OF SSCD ASSOCIATED WITH EDS
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The sponsors had no role in the design or conduct of this research. Received 15 July 2018; accepted 19 October 2018 Citation: World Neurosurg. (2019) 122:161-164. https://doi.org/10.1016/j.wneu.2018.10.126
Conflict of interest statement: M. Udawatta is supported by a David Geffen Medical Scholarship. I. Yang is supported by the UCLA Visionary Ball Fund Grant, UCLA Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research Scholars in Translational Medicine Program Award, Jason Dessel Memorial Seed Grant, UCLA Honberger Endowment Brain Tumor Research Seed Grant, and Stop Cancer (US) Research Career Development Award.
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