Gross total resection of a rare epidermoid cyst in the supplementary motor area without postoperative SMA syndrome: A case report and literature review

Abstract

Epidermoid cysts rarely occur in the supplementary motor area (SMA), where resection carries a particular risk of postoperative SMA syndrome. We present the case of a 25-year-old woman who developed persistent headache and intermittent dizziness. Preoperative MRI revealed a right medial frontal lesion with low T1, high T2, and restricted diffusion, consistent with an epidermoid cyst.
Microsurgical resection was performed via a right interhemispheric approach under neuronavigation. Internal decompression was followed by capsule dissection along the tumor–brain interface. Particular care was taken to preserve bridging veins, avoid fixed retractors, and minimise traction on the SMA cortex. A superficial cortical vein with focal wall irregularity was reinforced with hemostatic material instead of being sacrificed. Gross total removal was achieved with minimal blood loss.

The patient recovered without neurological deficits, was mobilised on the third postoperative day, and was discharged home. Histopathology confirmed the diagnosis. Follow-up MRI at six months showed no recurrence, and her modified Rankin Scale score was 0.

This case highlights that, although SMA epidermoid cysts are exceedingly rare, complete resection with full functional preservation is achievable. Careful surgical planning, venous preservation, and low-traction microsurgical techniques are crucial to avoid SMA syndrome in this eloquent cortical region.