To report a case of a comatose patient with anoxic brain injury who exhibited periodic oral automatisms (chewing) without any physical or noxious stimulation, and to discuss its prognostic value.

A 43-year-old female with stage IV adenocarcinoma of the lung, with metastases to the brain and bone, presented with an out-of-hospital pulseless electrical activity cardiac arrest, requiring multiple rounds of resuscitation. Video-EEG conducted within 24 hours showed a generalized background suppression pattern (Figure A). Additionally, the patient was noted to have spontaneous, periodic episodes of chewing or oral automatisms lasting 3-4 seconds without any physical or noxious stimulation (Figure B). Some of these episodes were preceded by left arm myoclonus and spontaneous eyelid openings. Brainstem reflexes were intact. MRI brain showed diffuse cortical and subcortical anoxic injury (Figure C).

Periodic oral automatisms are episodes of chewing movements that occur at regular intervals. Zettler et al. studied oral automatisms in patients with acute coma of different etiologies, finding a prevalence rate of 18.4%. (1) The underlying mechanism of this phenomenon is still unknown, but it could be a subcortical phenomenon, as there was no corresponding activity on the EEG. This clinical sign could be associated with poor prognosis, as our patient was declared brain dead on day 6; however, the data are limited. (1) Our case adds to the existing sparse literature of oral automatisms in comatose patients.