Investigation of endolymphatic hydrops by electrocochleography in patients with Cogan's syndrome.

Abstract

We compared auditory and vestibular function between a patient with typical Cogan's syndrome and a patient with atypical Cogan's syndrome. Repeat audio grams demonstrated fluctuating sensorineural hearing loss in the affected ear. Brainstem auditory evoked response testing revealed no abnormalities. Hallpike caloric testing showed a decreased response in the affected ear in the typical case and responses within normal limits in the atypical case. Sinusoidal harmonic acceleration was normal in the typical case, and there was an abnormal phase at 0.01 Hz in the atypical case.

Endolymphatic hydrops was investigated by electrocochleography. In both patients, there was an enhancement of the summating potential, with an increased ratio of summating potential to action potential amplitude. This finding is consistent with endolymphatic hydrops.

Introduction

In 1945, Cogan described a syndrome of nonsyphilitic interstitial keratitis combined with a Meniere's-like complex of symptoms. [1] This clinical entity is known as typical Cogan's syndrome. When another inflammatory lesion is present, in addition to or instead of interstitial keratitis, the condition is termed atypical Cogan's syndrome. [2,3] Atypical cases are more often associated with multisystem involvement.

Audiograms of patients with Cogan's syndrome have shown both unilateral and bilateral sensorineural hearing loss with fluctuations. Caloric responses have been severely depressed or absent. [3,4]

In the course of conducting otoneurologic examinations of patients with vestibuloauditory dysfunction, we diagnosed three cases of Cogan's syndrome. Two of these cases were of the atypical type, and the other was typical. Electronystagmography (ENG) showed that one of the patients with atypical Cogan's syndrome had direction-changing positional nystagmus, with a failure of optic suppression. Brainstem auditory evoked response (BAER) testing showed a severe bilateral distortion of morphology after potential I and a prolonged interwave I-III. These findings are consistent with central vestibulo-auditory dysfunction in Cogan's syndrome, and they have been reported in detail elsewhere. [5]

This paper presents an analysis of vestibulo-auditory function and electrocochleographic findings in one case of typical and one case of atypical Cogan's syndrome.

Materials and methods

Auditory function was assessed by conventional audiometry, stapedius reflex measurements, and BAER. Vestibular function was evaluated by ENG and sinusoidal harmonic acceleration (SHA) testing. Seven harmonic frequencies from 0.01 to 0.64 Hz were obtained. Optic fixation on angular acceleration was studied at 0.32 Hz.

Auditory evoked electrocochleography (ECoG) was performed with a Nicolet CA-1000 clinical signal averager, using forehead-to-tympanic membrane [6] and ipsilateral earlobe electrobe placement with inserted earphones. The following parameters were used: stimulus click of 100 [micro]sec duration; alternating polarity; rate of 11.1/sec; intersity of 95 dBnHL; and time analysis of 5 msec with 256 data points. A total of 100 clicks were averaged. Responses we filtered with a bandpass of 10 to 1,500 Hz. Two trials were obtained for each averaged response and recorded on a Hewlett-Packward X-Y plotter.

Measurement of amplitude and latency of the summating (SP) and action potentials (AP) were obtained. The criterion for abnormality was based the SP/AP ratio system introduced by Eggermont, [7] Coats, [8] and Gibson et al. [9]

Case reports

Case 1: Typical Cogan's syndrome. A 26-year-old white man complained that for approximately 1 year he had been experiencing intermittent sensations of burning eyes, which were more severe in his right eye. These sensations were accompanied by blurriness, photophobia, and pain. He also experienced episodic vertigo and fluctuating right-sided hearing loss with tinnitus. His medical history was significant for acoustic trauma: when he was 11 years old, a firecracker had exploded near his left ear. The family history was noncontributory.

On physical examination, no ear, nose, or throat abnormalities were noted. Ophthalmologic evaluation was consistent with bilateral interstitial keratitis, which was greater in the right eye than in the left. The results of a lymphocyte transformation test were reported as not significant. Venereal Disease Research Laboratory (VDRL) and fluorescent treponemal antibody (FTA) tests were negative. Computed tomography (CT) of the temporal bones was negative.

Audiometry of the left ear showed a high-frequency sensorineural hearing loss that was consistent with acoustic trauma (figure 1A). In the right ear, there was evidence of a fluctuating sensorineural hearing loss (figure 1B). A stapedius reflex was evident bilaterally, with no decay. BAER tracings showed no disturbance in electrical activity on either side of the brainstem. ENG showed a spontaneous nystagmus to the right (eyes closed) of 8[degrees]/sec and nystagmus to the right in the right-ear-undermost position of the same velocity. The velocity increased to 10[degrees]/sec when the patient sat up. Hallpike caloric testing disclosed a reduced vestibular response in the right ear (35%). Postcaloric fixation was normal. SHA testing revealed that phase, gain, and asymmetry values were within normal limits. Optic fixation on angular acceleration was normal. ECoG recordings in the right ear showed an enhancement of the summating potential, with an increased SP/AP ratio of 67% (figure 1C).

Case 2: Atypical Cogan's syndrome. A 36-year-old white woman reported that for 2 weeks she had been experiencing episodic vertigo, disequilibrium (falling to the right), and fluctuating right-sided hearing loss with tinnitus. She said that she had been diagnosed with Meniere's s disease 10 years earlier, and that 2 years later she had received an endolymphatic shunt in her right ear. The following year, she developed an inflammatory condition in her eyes, which was diagnosed as bilateral iritis (greater in the right). For the previous 2 years, she had had bilateral macular edema.

Her medical history was significant for ankylosing spondylitis of 14 years' duration and Crohn's disease for 12 years. Her family history disclosed that one sister had bilateral iritis, Crohn's disease, and fluctuating hearing. The patient's mother also had bilateral iritis.

On physical examination, there was no nystagmus. No ear, nose, or throat abnormalities were noted. Her gait was normal, and her Romberg test was negative. A lymphocyte transformation test was not performed. VDRL and FTA tests were negative. CT of the temporal bones was negative.

Audiometry of the left ear showed that her hearing was within normal limits (figure 2A). There was a mixed hearing loss for the right ear (figure 2B). A tympanogram indicated normal bilateral middle ear function. There was stapedius reflex decay in the right ear (1 kHz). Repeat audiography demonstrated a fluctuating hearing in the right ear (figure 2B). BAER tracings showed no disturbance in electrical activity on either side of the brainstem. ENG showed no spontaneous nystagmus. There was nystagmus to the right with the posthead-shake maneuver (eyes closed) of 9[degrees]/sec. There was also nystagmus to the right with the left-ear-undermost position of 120[degrees]/sec, with no associated vertigo. Hallpike caloric testing was within normal limits, and postcaloric optic fixation was normal. SHA showed an abnormal phase at 0.01 Hz; gain was slightly abnormal at 0.32 Hz, and the asymmetry value was normal. Optic fixation on angular acceleration was normal. These findings are consistent with nonlocalizing vesti bular dysfunction. ECoG recordings in the right ear demonstrated an enhancement of the summating potential with an increased SP/AP ratio of 56% (figure 2C).

Discussion

Cogan' s syndrome is a rare disease that predominantly affects young adults--whites more than others, women more than men. It is interesting to note that one of the patients reported by Prosper Meniere in his fourth paper on June 15, 1851, had ocular symptoms. As reported by Atkinson, Meniere wrote, "A coachman aged 38 years, habitually healthy, experienced on the 27th day of February last some disturbance of vision. It seemed to him that objects were covered with a white mist and oscillated as if the carriage was in motion. He went to bed and soon experienced vertigo. The next day the vertigo increased with disequilibrium. Vertigo episodes continued for two months. From the beginning of the illness, he had noises in the left ear and from the fifteenth day of his strange condition, he could no longer hear the ticking of his watch in this ear, while the right ear preserved its usual acuity. He lost his sense of balance specially on the left. He does not feel so free in his movements, and mistrusts his eyesight ."[10] This description strongly suggests that this patient had Cogan's syndrome.

The etiology of Cogan's syndrome remained obscure for many years. In 1979, McCabe presented evidence of a distinct clinical entity called autoimmune sensorineural hearing loss.[11] He subsequently reported that at least one of his patients later developed Cogan's syndrome.[12] In 1983, Hughes et al concluded, on the basis of positive cellular immune responses to inner ear antigen stimulation (lymphocyte migration inhibition and transformation tests) in patients with Cogan's syndrome, that 1) the vestibuloauditory component is autoimmune in origin, 2) the autoimmune process is mediated through cellular (not humoral) pathways, 3) systemic steroids might suppress positive test results, and 4) test results are more likely to be positive when symptoms are acute.[13]

Studies with experimentally induced endolymphatic hydrops in animals by Aran et al showed a close correlation of an increased ratio of SP/AP amplitude with histologically demonstrated hydrops.[14] Studies in man by Coats,[8] Gibson, [15] and Arenberg et al[16] disclosed that the SP/AP amplitude ratio is a sensitive indicator of endolymphatic hydrops. In the two Cogan's syndrome patients that we examined, an enhancement of the SP with an increased SP/AP ratio was demonstrated at the time of the acute symptoms; therefore, we conclude that the Meniere's like complex of symptoms they experienced were the result of endolymphatic hydrops. This conclusion is in agreement with the finding of hydrops in the temporal bones of Cogan's syndrome patients studied by Fisher and Hellstrom,[17] Wolff et al,[18] and Rarey et al.[19] These authors all reported similar pathologies: deposition of various amounts of fibrous tissue and new bone in the inner ear spaces and degeneration of the Organ of Corti and vestibular sense orga ns.

Acknowledgment

We are indebted to Araxie Choukourian and Victoria DiPerri for their technical assistance.

From Ear Consultants of Michigan, Royal Oak, Mich. (Dr. Benitez and Dr. Bojrab); the Department of Audiology, William Beaumont Hospital, Royal Oak (Dr. Lubbers); and the Department of Communication Disorders, Audiology Clinic, Central Michigan University, Mt. Pleasant, Mich. (Mr. Arsenault).

Reprint requests: Jaime T. Benitez, MD, 34135 Hunters Row, Farmington Hills, MI 48331. Phone: [phone]; fax [phone]; e-mail:[e-mail]

References

(1.) CoganDG. Syndrome of nonsyphilitic Keratitis and Vestibuloauditory symptoms. Arch Ophthalmol 1945;33:144-9.

(2.) Cody DT, Williams HL. Cogan's syndrome. Laryngoscope 1960;70:447-78.

(3.) Haynes BF, Kaiser-Kupfer MI, Mason P, Fauci AS. Cogan syndrome: Studies in thirteen patients, long-term follow-up, and a review of the literature, Medicine (Baltimore) 1980;59:426-41.

(4.) Vollertsen RS, McDonald TJ, Younge BR, et al. Cogan's syndrome: 18 cases and a review of the literature. Mayo Clin Proc 1986;61:344-61.

(5.) Benitez JT, Arsenault MD, Licht JM, et al. Evidence of central vestibulo-auditory dysfunction in atypical Cogan's syndrome: A case report. Am J Otol 1990;11:131-4.

(6.) Arsenault MD, Benitez JT. Electrocochleography: A method for making the Stypulkowski-Staller electrode and testing technique. Ear Hear 1991;12:358-60.

(7.) Eggermont JJ. Summating potentials in electrocochleography: Relation to hearing disorders. In: Ruben RJ, Elberling C, Salomon G, eds. Electrocochleography. Baltimore: University Park Press 1976:67-87.

(8.) Coats AC. The summating potential and Meniere's disease. I. Summating potential amplitude in Meniere and non-Meniere ears. Arch Otolaryngol 1981;107:199-208.

(9.) Gibson WP, Prasher DK, Kilkenny GP. Diagnostic significance of transtympanic electrocochleography in Meniere's disease. Ann Otol Rhinol Laryngol 1983;92:155-9.

(10.) Atkinson M. Meniere's original papers. Acta Otolaryngol Suppl (Stockh) 1961;162:1-78.

(11.) McCabe BF. Autoimmune sensorineural hearing loss. Ann Otol Rhinol Laryngol 1979;88:585-9.

(12.) McCabe BF. Autoimmune inner ear disease. Presented at the University of Minnesota's Third International Symposium on Clinical Otology, 1981, Minneapolis.

(13.) Hughes GB, Kinney SE, Barna BP, et al. Autoimmune reactivity in Cogan' s syndrome: A preliminary report. Otolaryngol Head Neck Surg 1983;91:24-32.

(14.) Aran JM, Rarey KE, Hawkins JE Jr. Functional and morphological changes in experimental endolymphatic hydrops. Acta Otolaryngol (Stockh) 1984;97:547-57.

(15.) Gibson WP. The use of electrocochleography in the diagnosis of Meniere's disease. Acta Otolaryngol Suppl (Stockh) 1991;485:46-52.

(16.) Arenberg IK, Obert AD, Gibson WP. Intraoperative electrocochleographic monitoring of inner ear surgery for endolymphatic hydrops: A review of cases. Acta Otolaryngol Suppl (Stockh) 1991;485:53-64.

(17.) Fisher ER, Hellstrom HR. Cogan's syndrome and systemic vascular disease: Analysis of pathologic features with reference to its relationship to thromboangiitis obliterans (Buerger). Arch Pathol 1961;72:572-92.

(18.) Wolff D, Bernhard WG, Tsutsumi S, et al. The pathology of Cogan's syndrome causing profound deafness. Trans Am Otol Soc 1965;53:94-109.

(19.) Rarey KE, Bicknell JM, Davis LE. Intralabyrinthine osteo-genesis in Cogan's syndrome. Am J Otolaryngol 1986;7:387-90.