A case of Susac syndrome.

Susac syndrome is a readily recognized but often misdiagnosed disorder almost exclusively affecting women in the 20- to 40-year age range. Characterized by the clinical triad of encephalopathy, branch retinal artery occlusions, and sensorineural hearing loss, patients with Susac syndrome are often misdiagnosed with multiple sclerosis (MS). Unlike MS, however, the disease process extends over a 1- to 2-year period and then goes into remission. This presentation describes the progression of symptoms of a patient eventually diagnosed with Susac syndrome.

Otoacoustic emissions in normal-cycling females.

The purpose of this study was to determine if the menstrual cycle influences the amplitude of transient (TEOAEs) and distortion-product (DPOAEs) otoacoustic emissions. Thirteen normal-hearing, normal-cycling females were monitored weekly for 12 weeks. TEOAE and DPOAE amplitudes were analyzed to determine if amplitude changes could be detected and correlated to phases of the menstrual cycle. No systematic amplitude changes were observed, demonstrating that evoked OAEs are unaffected by physiologic changes associated with the menstrual cycle.

Simultaneous comparison between transtympanic and extratympanic electrocochleography.

Electrocochleography (ECoG) has become a mainstay in the diagnostic armamentarium used by otolaryngologists and audiologists in the evaluation of patients suffering auditory and vestibular symptoms. Controversy exists, however, regarding the relative accuracy of ECoG when recorded with a non-invasive external auditory canal (EAC) electrode as compared to that recorded using a transtympanic electrode. In an effort to resolve this controversy, 19 healthy volunteers (37 ears) with no history of otologic disease or symptoms and a normal screening pure-tone audiogram were studied. For each volunteer, a transtympanic electrode was placed on the cochlear promontory bilaterally under iontophoretic anesthesia followed by the immediate placement of an EAC TIPtrode (Etymotic Research Laboratory, Elk Grove Village, Illinois). Signals from both the transtympanic electrode and the TIPtrode were recorded simultaneously following click stimulus using the Nicolet CA 1,000. Preliminary analysis of these recordings identify no significant difference in summating potential/action potential ratios between EAC and transtympanic electrodes in this normal subject population.

Dehydration testing and the diagnosis of Menière's disease: case report.

A 34-year-old female presented to our clinic with complaints of hearing loss, tinnitus, and severe rotational vertigo. A test battery including complete audiometric testing, auditory brainstem response (ABR) audiometry, electronystagmography (ENG), electrocochleography (ECoG), and dehydration testing was performed. Monitoring of hearing sensitivity, speech understanding, and ECoG responses following administration of a dehydrating agent were sensitive measures of cochlear function and confirmed the diagnosis of Meniere's disease. The induced changes also contributed to the therapeutic measures recommended.

A comparison of electrocochleography recording techniques.

Dual channel electrocochleography recordings were obtained in 50 ears (25 patients). The summating potential/action potential amplitude ratios from horizontal and vertical recording montages were compared. Our findings show good summating potential/action potential ratio agreement between the two recording montages when an established normal criterion is used. Further statistical analysis may allow us to use the horizontal and vertical montages interchangeably to aid in the identification of summating and action potentials.

Summating potential/action potential ratio in perilymph fistula.

A prospective study of electrocochleography in patients with clinically suspected perilymph fistula was undertaken to determine its predictive value in that disorder. One hundred forty-four patients suspected of having perilymph fistula had electrocochleography performed--34 of these (39 ears) had exploratory tympanotomy. Of the 19 ears with normal preoperative summating potential/action potential (SP/AP) ratio, ten had perilymph fistula identified at the time of surgery. Of the 20 ears with abnormal SP/AP ratio, 16 had perilymph fistula confirmed at exploration, 18 had resolution of symptoms after oval window and round membrane grafting, and only one ear had postoperative persistence of the abnormal SP/AP ratio. This study suggests that an abnormal SP/AP ratio is not only predictive of endolymphatic hydrops, but also of perilymph fistula (both problems of inner ear fluid imbalance). This study also suggests that, while abnormal SP/AP ratio is fairly specific for inner ear fluid imbalance, it is not sensitive.

Norms for disproportionate loss in speech intelligibility.

The audiometric records of 324 subjects with sensorineural hearing loss, presumed to be cochlear, were analyzed in order to develop norms for "disproportionate loss" in speech intelligibility. From the scatterplot relating PBmax to PTA2 (average of HTLs at 1,000, 2,000, and 4,000 Hz), and the scatterplot relating SSImax to PTA1 (average of HTLs at 500, 1,000, and 2,000 Hz), linear boundaries were constructed encompassing approximately 98% of observed values. A speech intelligibility score (PB or SSI) may be considered "disproportionately poor" if it falls below this empirically derived boundary.