Skin and/or muscle biopsies in 4 patients, ages 18 months, 8, 9, and 16 years, with alternating hemiplegia of childhood (AHC) were examined by electron microscopy and compared with healthy controls in a study at University Hospital, Lille, France. Vascular abnormalities present in both skin and muscle small vessels included endothelial vacuoles, intracytoplasmic vacuoles in vascular smooth muscle cells (VSMCs) in the tunica media, apoptotic nuclei, and isolation of VSMCs from neighboring cells. A primary or secondary vascular pathophysiology is suggested for AHC. 
COMMENT. AHC is characterized by 3 phases; 1) abnormal eye movements and dystonic episodes; 2) episodic hemiplegia and developmental delay; and 3) persistent neurologic deficits. Onset is before 18 months of age, and symptoms resolve during sleep. Formerly ascribed to a migraine equivalent, an epilepsy, or movement disorder, the present evidence suggests a neurovascular mechanism, similar to the cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).