Alternating hemiplegia syndrome: electroencephalogram, brain mapping, and brain perfusion SPECT scan study in a...

A 3-year-old Chinese girl with alternating hemiplegia syndrome failed to respond to anticonvulsants, antimigrainous drugs, and calcium channel blockers. She made a complete remission with a 4-week course of steroid, and relapsed after steroid withdrawal. Electroencephalogram and brain mapping during the hemiplegic attack showed unilateral high-voltage sharp slow-wave discharges in the temporo-occipital region contralateral to the hemiplegic side and diffuse high-voltage slowing during attacks of quadriplegia or other clinical manifestation such as dullness, lethargy, or yawning. Brain perfusion single photon emission computed tomographic (SPECT) scan study during the attack showed decreased uptake in the temporoparietal region contralateral to the hemiplegic side and in the ipsilateral basal ganglia, whereas the perfusion was normal between attacks. Electroencephalogram background activity was improved while the child was in clinical remission with steroid treatment. Computed tomographic and magnetic resonance imaging scans of the brain were normal. Carotid angiogram failed to show any structural or dynamic changes of the carotid arteries. The possible mechanism underlying alternating hemiplegia syndrome might be transient and reversible cerebral ischemia with high-voltage slow-wave discharges shown in the electroencephalogram and decreased perfusion in SPECT scan.