Side-effects of risperidone therapy mimicking cerebrospinal fluid shunt malfunction: implications for clinical monitoring and management.

Risperidone is an atypical antipsychotic used in the treatment of several psychiatric disorders in both children and adults. We present two patients with hydrocephalus and learning difficulties who were admitted to the neurosurgical unit with a suspected cerebrospinal fluid shunt malfunction and raised intracranial pressure. They had both been commenced on risperidone for the treatment of aggressive outbursts. Twelve days after commencing risperidone, the first patient developed symptoms of headache, nausea, vomiting, drowsiness, lethargy and two episodes of collapse. The second patient presented with similar symptoms 4 days after his risperidone dose was increased. An unnecessary shunt exploration was averted in both cases when it was noted that the side-effect profile of risperidone mimicked exactly those of shunt malfunction. Discontinuation of the drug resulted in complete resolution of all symptoms within 72 h. Many patients with shunted hydrocephalus have associated developmental disorders that may warrant treatment with risperidone. Clinicians should be aware of the potential symptom overlap between shunt malfunction and risperidone side-effects in these patients.