A case of involuntary rhythmic and characteristic tapping sounds during sleep

Abstract

Abstract Involuntary motor disorders during sleep, such as sleep bruxism (SB) or facio-mandibular myoclonus (FMM), are observed in the oromandibuar area. This feature is repetitive and rhythmic movement produced by short muscle contraction. We report here a case of involuntary repetitive and unusual tapping sounds. The repetitive periodic jaw movement was observed every night but was absent during waking hours. The unusual sounds were confirmed both by audio recorder and the patient's bed partner. Video PSG showed spontaneous myoclonic EMG activity associated with lip movements and characteristic sounds from the patient's mouth. The movements existed in clusters throughout sleep. There are similarities and differences between this case and SB and FMM. The sleep stage and EMG activity in this case were similar to SB and FMM. The EMG burst duration was short as in FMM rather than the longer duration in SB. However, neither the characteristic sounds of grinding or clenching typical of SB nor the clicking sounds typical of FMM were observed. In addition, there was no history of tongue biting, which frequently occurs in SB and FMM. The authors were unable to find any reports regarding treatment for tapping sound, and unfortunately our attempted treatment was ineffective. In this case there was no response to either levetiracetam or clonazepam. Only triazolam reduced the number of episodes but did not result in a complete cure. This is the first reported case of video PSG documented rhythmic tapping sounds might be occurred from patient's oral cavity. We suggest that this case should be viewed as distinct from SB or FMM.