Cochlear-Facial Dehiscence A Newly Described Entity

Transcription

1 The Laryngoscope VC 2013 The American Laryngological, Rhinological and Otological Society, Inc. Case Report Cochlear-Facial Dehiscence A Newly Described Entity Danielle M. Blake, BA; Senja Tomovic, MD; Alejandro Vazquez, MD; Huey-Jen Lee, MD; Robert W. Jyung, MD Dehiscence of the cochlear otic capsule has recently been described as a pathologic entity. We describe two cases of cochlear-facial dehiscence, which are the first : a 69-year-old male who complained of hearing loss, autophony, and pulsatile tinnitus and a 41-year-old female who complained of left-sided hearing loss, pulsatile tinnitus, and vertigo. In both, computed tomography (CT) showed bony dehiscence between the facial nerve and cochlea. Cochlear-facial dehiscence is another example of otic capsule dehiscence that produces symptoms of third-window lesions. When patients present with symptoms of third-window lesions and CT does not show superior canal dehiscence, cochlear-facial dehiscence should be considered. Key Words: Dehiscence, otic capsule, cochlea, facial nerve, hearing loss, pulsatile tinnitus, autophony. Laryngoscope, 124: , 2014 INTRODUCTION Primary otic capsule dehiscence, in the absence of tumor, cholesteatoma, or chronic otitis media, has become an increasingly recognized pathologic entity, especially with the advent of newer fine-resolution imaging modalities. Superior semicircular canal dehiscence (SSCD), first described by Minor et al., 1 has been increasingly recognized by clinicians as a cause of auditory and vestibular symptoms. It is hypothesized that the symptoms associated with SSCD are explained by the presence of a pathologic third mobile window. 1 The primary symptoms of SSCD include vertigo and nystagmus provoked by pressure or sound (Tullio phenomenon), 1 autophony for internally conducted sounds, 2 and conductive hearing loss. 1 Otic capsule dehiscence restricted to the cochlea has also been recognized as a pathologic entity. For example, cochlear-carotid dehiscence has been described, with manifestations ranging from pulsatile tinnitus and hearing loss to pressure-induced vertigo. 3 6 Similarly, two instances of bony dehiscence between the internal auditory canal and cochlea have been. 7,8 Here we describe two cases of cochlear-facial dehiscence (CFD), which we believe to be the first in the English literature. We From the Department of Otolaryngology Head and Neck Surgery (D.M.B., S.T., A.V., R.W.J.), and Department of Radiology (H.-J.L.), Rutgers New Jersey Medical School, Newark, New Jersey Editor s e: This Manuscript was accepted for publication May 30, The authors have no funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Robert W. Jyung, MD, Assistant Professor, Director of Otology and Neurotology, Department of Otolaryngology Head and Neck Surgery, Rutgers New Jersey Medical School, 90 Bergen Street, Suite 8100, Newark, NJ jyungrw@umdnj.edu DOI: /lary describe the clinical presentation, physiologic findings, and radiologic findings in these two cases. CASE REPORTS Case 1 A 69-year-old male with a history of coronary artery disease and low blood pressure was referred for bilateral hearing loss, pulsatile tinnitus (often synchronous with his heartbeat), and autophony (his own voice perceived as a vibration in both ears). He denied otalgia, otorrhea, vertigo, or imbalance. Otoscopic examination was normal bilaterally. His facial nerve function was normal bilaterally. The Weber test lateralized slightly to the right; the Rinne test was positive bilaterally. He perceived a 128-Hz tuning fork placed on the knees and medial malleoli as a vibration in both ears (more so on the right). Audiometry showed a symmetric, progressively downsloping mild- to moderately severe mixed (but predominantly sensorineural) hearing loss, with slight airbone gaps in the low and mid frequencies. There was a distinctive symmetric notch in the air conduction s at 1 khz, which was striking (Fig. 1A). Discrimination scores were 80% on the right and 72% on the left. Temporal bone computed tomography (CT) was performed on a GE Lightspeed Pro 16 (GE Healthcare, Milwaukee, WI) with 1.25-mm cuts with mm retrograde reformats. Coronal cuts were suspicious for dehiscence of the right superior semicircular canal, but on Stenvers view there appeared to be a thin, intact bony septum. However, analysis of the axial (Fig. 2A and 2B), coronal (Fig. 3A and 3B), Stenvers (Fig. 4A and 4B), and Poschl views revealed no bony margin at the superior portion of the basal turn of the cochlea bilaterally, at the crossing point of the labyrinthine segment of 283

2 Fig. 1. (A) Case 1 audiogram showing symmetric, progressively downsloping mild to moderately severe mixed but predominantly sensorineural hearing loss. (B) Case 2 audiogram showing left-sided mixed hearing loss and mild right-sided sensorineural hearing loss at 3 khz. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] the facial nerve. The maximum lengths of the dehiscences were found to be 2.1 mm on the right in the coronal view and 2.8 mm on the left in the coronal view. Vestibular evoked myogenic potential (VEMP) testing revealed robust responses bilaterally at 110 db, but no responses were elicited at 75 db on either side (Fig. 5A and 5B). The patient was satisfied with his diagnosis and requested no further treatment. Case 2 A 41-year-old female with a history of hypertension, HIV (CD4 count 680), two prior episodes of HIV-related meningitis, and one recent episode of herpetic meningitis was referred for evaluation of a left-sided tympanic membrane (TM) perforation. The patient complained of left-sided hearing loss and pulsatile, left-sided tinnitus with a buzzing or ocean-like quality. In addition, she Fig. 2. Axial computed tomography temporal bone showing a double shadow sign where the fallopian canal is superimposed on the basal turn of the cochlea (arrows). (A) Case 1 right side. (B) Case 1 left side. (C) Case 2 right side. (D) Case 2 left side. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] 284

3 Fig. 3. Coronal computed tomography temporal bone showing the lack of bony margin and merging of the overlying facial canal and cochlea (arrowheads). (A) Case 1 right side. (B) Case 1 left side. (C) Case 2 right side. (D) Case 2 left side. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] episodes of vertigo, each lasting 10 to 20 seconds. The vertigo was not sound induced and was not associated with nausea or vomiting. She denied other otologic symptoms. Examination of the left ear showed a dry posteroinferior TM perforation, without evidence of cholesteatoma. The right ear was normal. Her facial nerve function was normal bilaterally. The Weber test lateralized to the right; the Rinne test was positive bilaterally. Audiometry showed a left-sided mixed hearing loss, with a distinct notch at 2 khz (Fig. 1B). The right ear displayed an air conduction notch at 3 khz and was otherwise normal. A temporal bone CT was performed on a GE Lightspeed Pro 16 with 1.25-mm cuts with mm retrograde reformats. On review of the CT, there was no separation between the facial nerve and the basal turn of the cochlea bilaterally (Fig. 2C, 2D, 3C, 3D, 4C and 4D). The maximum lengths of the dehiscences were found to be 1.4 mm on the right in the Stenvers view and 1.8 mm on the left in the coronal view. VEMP testing showed absent waveforms on the left at 110 db and 75 db and normal waveforms at 110 db but absent waveforms at 75 db on the right (Fig. 5C and 5D). The patient underwent left transmeatal myringoplasty with gelatin foam packing. Postoperatively, the patient some relief of her autophony and increased hearing. DISCUSSION These are the first two cases in the English literature of CFD. There have been several other reports of dehiscence between the cochlea and its adjacent structures (Fig. 6). These include four reports of carotid artery cochlear dehiscence 3 6 and two reports of internal auditory canal and cochlea dehiscence. 7,8 Fig. 4. Stenvers computed tomography temporal bone with no identifiable bony septum between the overlying facial nerve and cochlea below (arrowheads). (A) Case 1 right side. (B) Case 1 left side. (C) Case 2 right side. (D) Case 2 left side. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] 285

4 Fig. 5. Vestibular evoked myogenic potential recordings. (A) Case 1 right side. (B) Case 1 left side. (C) Case 2 right side. (D) Case 2 left side. However, none of these cases was associated with a dehiscence between the facial nerve and the cochlea. A comparison of our cases with the other cochlear dehiscence cases is presented in Table I. Our workup included an audiogram and CT imaging, followed by VEMP testing once the dehiscences were seen. Close inspection of the CT scan revealed the cochlear-facial dehiscences, but in retrospect the Fig. 6. Summary of cases involving dehiscence into the cochlea. (A) Cochlear-carotid dehiscence (Modugno et al., 3 Kim and Wilson, 4 Neyt et al., 5 Lund and Palacios 6 ). (B) Cochlear-internal auditory canal dehiscence (Karlberg et al., 7 Manzari and Scagnelli 8 ). (C) Cochlear-facial dehiscence ( in this study). (D) Cochlear-jugular dehiscence (not yet described). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] 286

5 TABLE I. Cases of Cochlear Dehiscence Author Presentation Otoscopy Audiogram CT VEMP Treatment Modugno et al. 3 (2004) Kim and Wilson 4 (2005) Karlberg et al. 7 (2006) Neyt et al. 5 (2011) Lund and Palacios 6 (2011) Continuous nonpulsatile tinnitus b/l (R > L) Progressive right-sided HL Stapedectomy for presumed otosclerosis, returned with: pressure-induced vertigo, right pulsatile tinnitus synchronous with heart rate, some hearing improvement Syncopal episodes Dizziness ( unsteadiness ) Headache Vertigo Left-sided HL Progressive b/l HL Left pulsatile tinnitus Stapedectomy for presumed left-sided otosclerosis, postop: no hearing improvement, continued tinnitus Right pulsatile tinnitus Right-sided carotid pressure lessened severity of tinnitus Left: normal Right: large TM perforation Mild SNHL b/l between 4 8 khz Initial: right CHL with a Carhart s notch Poststapedectomypersistent ABG between 500 2,000 Hz Left: mixed HL, 40 db ABG at 250 Hz Right: 20 db ABG at 250 Hz Initial: b/l mixed HL, b/l Cahart s notches Poststapedectomypersistent ABG Mild asymmetric high-frequency SNHL No ABG B/l dehiscence of Left: 70 db bony septum ; separating right: 65 db basal turn of cochlea from contiguous carotid canal, greater extension on right Stapes prosthesis in good position Dehiscence of carotid canal at apical turn of cochlea Dysplasia of left cochlea with a shortened cochlea and deficient modiolus B/l dehiscence between apex of cochlea and ICA Dehiscence along vertical segment of right petrous ICA into basilar turn of cochlea Left: 85 db Right: 95 db No surgery BAHA Manzari and Scagnelli 8 (2013) Case 1 Right-sided HL Right-sided tinnitus Sound-induced dizziness Exertion-induced oscillopsia B/l HL B/l aural fullness B/l pulsatile tinnitus synchronous with heart rate Autophony Dehiscence between lateral end of internal auditory meatus and cochlea Symmetric downsloping mild-moderate mixed, but predominantly SNHL Mild ABG in low and mid frequencies B/l SSCD Right: SSCD, cochlear-facial dehiscence crosses Left: cochlear-facial dehiscence Left: 70 db Right: 65 db Waveforms present at 110 db but absent at 75 db b/l No surgery No surgery AC notch at 1 khz Case 2 Left-sided HL Left pulsatile tinnitus Vertigo Disequilibrium Left: dry perforation Right: normal Left: mixed HL with notch at 2 khz Right: AC notch at 3 khz B/l cochlearfacial dehiscence Left: absent waveforms at 110 db and 75 db Right: waveforms present at 110 db but absent at 75 db Left-sided T-plasty for perforated TM ABG 5 air-bone gap; AC 5 air conduction; BAHA 5 bone-anchored hearing aid; BC 5 bone conduction; b/l 5 bilateral; CHL 5 conductive hearing loss; CT 5computed tomography; HL 5 hearing loss; ICA 5 internal carotid artery; L 5 left; postop 5 postoperative; R 5 right; SNHL 5 sensorineural hearing loss; SSCD 5 superior semicircular canal dehiscence; TM 5 tympanic membrane; T-plasty 5 tympanoplasty; VEMP 5 vestibular evoked myogenic potential. 287

6 audiograms also provided subtle clues. We concluded that the dehiscences were real based on the absence of a bony septum in several planes and the apparent fusion of the fallopian canal and the cochlear basal turn. In the axial plane, the enhanced radiolucency caused by the overlap of the fallopian canal and the basal turn was particularly striking (Fig. 2). Given the reliance on CT imaging to make this diagnosis, the accuracy of CT in resolving otic capsule dehiscence is important. In a meta-analysis conducted to test the accuracy of 0.55-mm collimated CT in diagnosing SSCD, Cloutier et al. 9 found that CT had 100% sensitivity and 97% specificity. However, Belden et al. 10 a sensitivity of 100% and specificity of 77% for 1.0-mm collimated CT in diagnosing SSCD. In our cases and the other cochlear dehiscence cases, surgical confirmation was not undertaken owing to the risks heavily outweighing any potential benefit of surgical repair. As such, the possibility that a volume-averaging effect led to false-positive results cannot be definitively excluded. However, the studies were performed using a spiral CT scanner with axial images obtained at mm slice thickness with 0.562:1 pitch, with Stenvers and coronal reconstructions at mm pixel spacing; therefore, we are confident that we were able to detect dehiscences as small as 1.4 mm. Although even higher resolution CT scanners do exist, we have not yet pursued this option because of insurance obstacles and the problem of more radiation exposure. Therefore, we relied on a combination of suggestive history, physical exam, and high-resolution CT results to make the diagnosis of CFD. The audiograms of both patients showed unusual air conduction notches bilaterally. In case 1, the air conduction notches were symmetric at 1 khz. In case 2, a notch in the air conduction s was noted at 3 khz for the right ear. The notch at 2 khz in the left ear was present in both air- and bone-conducted s. Similar air conduction notches were also noted in audiograms presented in other case reports describing cochlear dehiscences. 3,7 We hypothesize that the focal hearing loss is related to the decreased efficiency in sound conduction within the cochlea due to the dissipation of energy through the mobile third window, corresponding to the frequency of the cochlear turn adjacent to the labyrinthine segment of the facial nerve. However, to confirm this, a more extensive analysis using Ketten s method for correlating the length along the cochlea with pitch frequency would be required. 11 Both patients showed absent waveforms at lower s on VEMP testing. This raises the question as to whether VEMP testing is a reliable tool in diagnosing all third-window lesions. It is well established that VEMP testing is highly sensitive and specific for SSCD, 12 but it is unclear whether the same results should be expected for cochlear capsule dehiscences. The pattern of energy dissipation may differ, such that the VEMP may not be altered in the same manner as for an SSCD. Alternatively, the method of VEMP testing used for our patients may not have allowed for optimal detection of lowered s. The patients were tested at 110 db and then at 75 db. Both showed absent 288 waveforms at 75 db. It is possible that waveforms would have been present if intermediate levels were tested. Karlberg et al. 7 decreased s at 85 db (left ear) and 95 db (right ear) in a patient with a thirdwindow lesion. Had our patients been tested at these intermediate levels, decreased s may have been discovered. However, owing to insurance limitations, the patients could not be retested at intermediate levels. It is also possible that these unexpected negative findings are due to the small size of the dehiscence, perhaps producing a physiologic change that is undetectable by VEMP testing. Pfammatter et al. 13 showed that in patients with SSCD, dehiscences greater than 2.5 mm were associated with lowered VEMP s significantly more often than were dehiscences of less than 2.5 mm. Furthermore, of the patients with smaller dehiscences, the number who failed to show decreased s was greater than the number who did. The dehiscence sizes measured in our two cases are all less than 2.5 mm except for the left side of case 2, which was only slightly greater at 2.8 mm. We suspect that these dehiscences directly contributed to our patients symptoms. Our hypothesis is that CFD creates a mobile third window, which causes pseudoconductive hearing loss, by dissipating the acoustic energy at the frequency of the cochlear turn adjacent to the dehiscence. The etiology of CFD is unclear, but we suspect a genetic or systemic predisposition to this pathology, as both cases show bilateral involvement, and one was also associated with thinning of bone over the superior semicircular canal. In addition, we believe that widening of the labyrinthine segment of the fallopian canal predisposes patients to this condition, as this finding was present bilaterally in both cases. It must also be noted that in case 2, some of the patient s symptoms resolved after myringoplasty. The degree to which her complaints persist or recur long-term will clarify how much her CFD was contributing to her symptoms. CONCLUSION We present two cases of a previously undescribed entity, cochlear-facial dehiscence. With presenting symptoms similar to those of SSCD, CFD may easily be misdiagnosed. It is important to carefully examine a temporal bone CT for alternative dehiscence patterns, including cochlear-carotid, cochlear-internal auditory canal, and cochlear-facial dehiscences, to accurately diagnose these patients. BIBLIOGRAPHY 1. Minor LB, Solomon D, Zinreich JS, Zee DS. Sound- and/or pressureinduced vertigo due to bone dehiscence of the superior semicircular canal. Arch Otolaryngol Head Neck Surg 1998;124: Watson SR, Halmagyi GM, Colebatch JG. Vestibular hypersensitivity to sound (Tullio phenomenon): structural and functional assessment. Neurology 2000;54: Modugno GC, Brandolini C, Cappello I, Pirodda A. Bilateral dehiscence of the bony cochlear basal turn. Arch Otolaryngol Head Neck Surg 2004;130: Kim HH, Wilson DF. A third mobile window at the cochlear apex. Otolaryngol Head Neck Surg 2006;135: Neyt P, Govaere F, Forton GE. Simultaneous true stapes fixation and bilateral bony dehiscence between the internal carotid artery and the

7 apex of the cochlea: the ultimate pitfall. Otol Neurotol 2011;32: Lund AD, Palacios SD. Carotid artery-cochlear dehiscence: a review. Laryngoscope 2011;121: Karlberg M, Annertz M, Magnusson M. Mondini-like malformation mimicking otosclerosis and superior semicircular canal dehiscence. J Laryngol Otol 2006;120: Manzari L, Scagnelli P. Large bilateral internal auditory meatus associated with bilateral superior semicircular canal dehiscence. Ear Nose Throat J 2013;92: Cloutier JF, Belair M, Saliba I. Superior semicircular canal dehiscence: positive predictive value of high-resolution CT scanning. Eur Arch Otorhinolaryngol 2008;265: Belden CJ, Weg N, Minor LB, Zinreich SJ. CT evaluation of bone dehiscence of the superior semicircular canal as a cause of sound- and/or pressure-induced vertigo. Radiology 2003;226: Ketten DR, Skinner MW, Wang G, Vannier MW, Gates GA, Neely JG. In vivo measures of cochlear length and insertion depth of nucleus cochlear implant electrode arrays. Ann Otol Rhinol Laryngol Suppl 1998;175: Zhou G, Gopen Q, Poe DS. Clinical and diagnostic characterization of canal dehiscence syndrome: a great otologic mimicker. Otol Neurotol 2007;28: Pfammatter A, Darrouzet V, Gartner M, et al. A superior semicircular canal dehiscence syndrome multicenter study: is there an association between size and symptoms? Otol Neurotol 2010;31: