Reversible opisthotonus following intracranial pressure changes in Chiari malformation.

A shunted myelodysplastic child with Chiari II malformation presented with shunt malfunction and opisthotonus. Correction of a distal obstruction lead to an initial improvement followed by overdrainage of cerebrospinal fluid and repetition of an opisthotonic posture. The possible mechanisms which unmask lower brainstem dysfunction in Chiari malformation when intracranial hyper- or hypotension exist, are discussed.