Hemifacial spasm in a child.

Hemifacial spasm in a 10-year-old child is herein reported. Computed tomography and angiography were normal. Magnetic resonance imaging showed an anomalous vascular structure, probably a redundant loop arising from AICA or PICA, which was identified at surgery. The spasm, presumably due to vascular compression at the root entry zone of the right facial nerve, promptly and completely remitted after surgical decompression, without functional deficits. Atypical clinical features, as well as pre- and postoperative neurophysiological findings supporting the microvascular compression theory, are discussed.