Moyamoya-related intracerebral hemorrhage associated with hyperemesis gravidarum.

A 32-year-old woman in her first pregnancy, presented with acute-onset hemidystonia and hemianesthesia which occurred while vomiting, on a background of hyperemesis gravidarum. Magnetic resonance imaging of the brain demonstrated right basal ganglia, thalamic, and capsular intracerebral hemorrhage, and time-of-flight magnetic resonance angiography demonstrated an occluded right middle cerebral artery with associated lenticulostriate collateral vessels, consistent with Moyamoya phenomenon. This case highlights the importance of managing hyperemesis gravidarum in patients with Moyamoya phenomenon to avoid Valsalva forces which are associated with intracerebral hemorrhage.