[Electroencephalogram with Pharyngeal Electrodes to Identify the Origin of Diffuse Spike-Wave-Like Discharges in a Case of Palatal Tremor].

Electromyographic artifacts are sometimes misinterpreted as epileptic discharges in scalp electroencephalograms (EEGs). In addition, the distribution of the epileptic discharges near the earlobe is often distorted by earlobe activation; therefore, these epileptic discharges may not be correctly diagnosed. Here, we report a case of palatal tremor in which diffuse spike-wave-like discharges were apparent on EEG. A 51-year-old woman was referred to our hospital because of transient loss of consciousness while driving. She had a past history of cerebral infarction, cerebellar hemorrhages, and symptomatic epilepsy. Magnetic resonance imaging findings showed T2 hyperintensity in the right inferior olivary nucleus. Single-photon emission computerized tomographic images demonstrated hypoperfusion of the left basal ganglion, bilateral thalamus, and bilateral anteroparietal lobes. Monopolar EEG recording showed diffuse spike-wave-like discharges with a frequency of 3-4 Hz cycle. To clarify the origin of these discharges, pharyngeal EEG recording simultaneously with conventional scalp electrodes was performed, which revealed that the discharges originated from the left pharynx. Rhythmic muscle contraction could be identified at the posterior pharynx and soft palate on close pharyngeal inspection. The electromyographic activities of the palatal tremor spread to the earlobe, and the activated earlobe electrodes apparently induced diffuse spike-wave-like discharges observed on monopolar EEG recording.