Occurrence of Andermann syndrome out of French Canada--agenesis of the corpus callosum with neuronopathy.

We report on two siblings, a boy and a girl, with agenesis of corpus callosum and neuronopathy. The children show diffuse hypotonia, delayed motor and mental development. Neurophysiological examinations revealed reduction of the motor nerve conduction velocity, absence of sensory nerve action potentials, abnormal somatosensory and visual evoked potentials. Nerve biopsies showed reduced density of myelinated and unmyelinated fibres in both children. We also found signs of hypomyelination and suggest this is secondary to degeneration of peripheral sensory and motor neurons. Our findings are consistent with the diagnosis of Andermann syndrome. This is the first report of the occurrence of Andermann syndrome out of French Canada.