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Electrocochleography Superior to Vestibular Evoked Myogenic Potential for Diagnosing Meniere's Disease: Presented at AAO-HNS

By Jacquelyn Beals

WASHINGTON, DC -- September 20, 2007 -- Electrocochleography (ECoG) is more useful than vestibular evoked myogenic potentials (VEMP) for the evaluation of Meniere's disease, a group of investigators reported here at the Annual Meeting of the American Academy of Otolaryngology - Head and Neck Surgery (AAO-HNS) Foundation.

VEMPs are potentiated by the sacculocollic reflex, and are transmitted via a pathway between the vestibular nerve and the sternocleidomastoid (SCM) muscle. Contraction of the SCM produces a large amplitude potential, indicating that the pathway is intact. ECoG assesses inner-ear function by comparing the summation potential (SP) generated by the outer hair cells to the action potential (AP) generated by the cochlear nerve.

In this prospective study, the 90 ears (in 71 patients) were divided into two groups: 62 ears with classic Meniere's disease and 28 with cochlear hydrops. Unilateral disease was present in 54 patients, and bilateral disease in 17 patients. Approximately 78% of the patients in each group had unilateral disease and 22% had bilateral disease. The investigators used an extra-tympanic ECoG technique in this study.

"We considered it abnormal if the SP/AP ratio was greater than.35," said co-author Terrence P. Murphy, MD, Staff Otolaryngologist, Northside Hospital, Atlanta, Georgia. VEMP used a tone burst of 750 Hz at 120 dB, which was "abnormal if there was a 45% asymmetry."

Other than vertigo, symptoms were similar in both cochlear hydrops and classic Meniere's disease patients.

Regarding hearing loss, 48% of the patients with classic Meniere's had a speech reception threshold (SRT) of less than 25 dB, while 61% of the patients with cochlear hydrops had an SRT of less than 25 dB.

Additionally, patients with classic Meniere's disease and patients with hydrops both reported hearing loss (71% and 83%, respectively), aural fullness (71% and 74%, respectively), and tinnitus (78% and 91%, respectively).

All hydrops patients (28 of 28) had abnormal ECoG, while 90% (56 of 62) of classic Meniere's patients had abnormal ECoG. Overall, ECoGs were abnormal in 93% of the patients.

VEMP was abnormal in 50% (14 of 28) of hydrops patients and 42% (26 of 62) of classic Meniere's patients. Overall, VEMPs were abnormal in 44% of the patients.

"I know a lot of people don't value ECoG, but in our patients it seemed to work fine," Dr. Murphy observed. "Symptoms don't tell you whether the VEMP is going to be normal or abnormal."

VEMP has other limitations, the team noted, including unreliability in elderly patients unable to flex their neck enough to produce muscle tension. Investigators concluded that both ECoG and VEMP were useful in the evaluation of cochlear hydrops and Meniere's disease, but ECoG testing was considered more reliable.

[Presentation title: ECOG and VEMP in the Evaluation of Meniere's Disease.]

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