We aim to report scalp-EEG and surface-EMG findings in a patient with frequent seizures due to supplementary sensorimotor area (SSMA) epilepsy mimicking alcohol withdrawal tremors.

Seizures associated with SSMA epilepsy are usually associated with brief bilateral tonic movements with retained consciousness. EEG correlate may be absent. These could be easily misclassified as non-epileptic movements like tremors or even psychogenic episodes.

The patient underwent continuous video-EEG monitoring using the standard international 10–20 system with surface-EMG electrodes applied according to institutional protocol to the muscle groups involved with a sampling rate of 200Hz.

A 30-year-old male with chronic alcohol use presented with intermittent “tremors” affecting his legs (right>left), concerning for alcohol withdrawal. His interictal EEG showed quasi-periodic bifrontal slow waves (FP1~FP2). During the seizures, he mainly had repetitive proximal right leg tonic contraction (~1 every second) with some involvement of right arm as well. Ictal EEG-sEMG recording demonstrated periodic slow waves maximum at Pz~Cz>P3~C3, time-locked to tonic synchronous sEMG bursts of right thigh agonists (quadriceps) and antagonists (hamstrings) and right deltoid muscle as well. His CT-Head revealed encephalomalacia in the left SSMA secondary to prior traumatic brain injury.

Typical seizure semiology associated with SSMA epilepsy is the bilateral asymmetric tonic seizure with retained consciousness. These seizures are usually difficult to lateralize and the EEG correlate may be absent or obscured. Our report shows a case of frequent bilateral leg tonic seizures (right>>left) arising from left SSMA, related to post-traumatic encephalomalacia. These movements were initially misclassified as tremors related to alcohol withdrawal. This case demonstrates that the interictal and ictal EEG findings in SSMA epilepsy may only consist of slow waves rather than sharp waves or spikes. However, the ictal recording of sEMG tonic bursts time-locked to the periodic slow waves confirms the epileptic nature of these discharges.