SMA is involved in various aspects of movement planning and initiation.  In the dominant hemisphere, it has connections with Brodmann Area 6 where speech production occurs.  SMA syndrome can occur after surgery involving or adjacent to this region. Unilateral SMA syndrome classically presents with contralateral hemiparesis or motor apraxia, aphasia (dominant hemisphere), with normal tone and reflexes.  It may present immediately or progress over 24-48 hours post-operatively. Recovery is variable most within 1-2 weeks.  Bilateral SMA syndrome occurs much less frequently and has been rarely described in the literature. 

Case Report:

A 64-year-old woman presented for resection of a parafalcine meningioma with invasion of superior sagittal sinus (SSS).  Operative procedure was uneventful with a planned ligation of the SSS, and intraoperative somatosensory and motor evoked potentials were normal.  She remained intubated due to depressed level of consciousness though was arousable to voice. She was unable to follow commands, had absent motor responses except weak withdrawal in the LUE, and intact 2/4 deep tendon reflexes. Imaging did not demonstrate new stroke or hemorrhage. Electroencephalogram revealed bifrontal delta slowing without epileptiform discharges. On post-operative day 3 (POD3), the patient was awake and alert, however, her motor strength was limited to following commands to wiggle thumbs only, with all other proximal muscle groups 0/5.  Patient was extubated on POD3. By POD14, she was 4+/5 in BUE, LLE wiggling toes, RLE no movement, delayed but fluent speech. At 12-week clinic follow up she was 5/5 in BUE, LLE 4+/5, RLE 4/5, ambulating with assistance.

SMA syndrome is an important differential consideration for immediate post-operative contralateral weakness, apraxia or akinetic mutism. Bilateral SMA is rare and may present with complex neurocritical care challenges and prolonged recovery.