Middle ear myoclonus: two informative cases and a systematic discussion of myogenic tinnitus.

Abstract

The term middle ear myoclonus (mem) has been invoked to explain symptoms of tinnitus presumably caused by the dysfunctional movement of either of the two muscles that insert in the middle ear: tensor tympani and stapedius. MEM has been characterized through heterogeneous case reports in the otolaryngology literature, where clinical presentation is variable, phenomenology is scarcely described, the pathogenic muscle is usually not specified, natural history is unknown, and the presumptive definitive treatment, tensor tympani or stapedius tendon lysis, is inconsistently effective. It is not surprising that no unique acoustogenic mechanism or pathophysiologic process has been identified to explain MEM, one of several descriptive diagnoses associated with the complicated disorders of myogenic tinnitus. Here, we explore MEM from the neurologist's perspective. Following the detailed descriptions of two informative cases from our clinic, we systematically evaluate the different mechanisms and movement disorder phenomena that could lead to a diagnosis of MEM. From a functional neuroanatomic perspective, we explain how tensor tympani MEM is best explained as a form of peritubal myogenic tinnitus, similar to the related disorder of essential palatal tremor. From a pathogenic perspective, we discuss how MEM symptomatology may reflect different mechanical and neurologic processes. We emphasize the diagnostic imperative to recognize when myogenic tinnitus is consistent with a psychogenic origin. Both individual patient care and further elucidation of MEM will rely on more detailed clinical characterization as well as multidisciplinary input from neurology, otolaryngology, and dentistry.