Neuroleptic Malignant Syndrome due to Tetrabenazine in a Boy with a Subacute Extrapyramidal Disorder

A 7-year-old boy with a known extrapyramidal disorder was admitted with fever, sporadic vomiting, respiratory distress and worsening dystonia for one day. An intrathecal baclofen (ITB) pump had been placed 12 months before for severe dystonia insufficiently controlled by oral baclofen and tetrabenazine. Reduction of tetrabenazine had been unsuccessful after placement of the ITB pump because of rebound dystonia and irritability. On admission, the patient presented in a reduced general condition, dehydrated, febrile and with clinical signs of obstructive bronchitis. CSF and urine analysis were normal, radiological exam revealed a pulmonary infiltrate. Suspected pneumonia was treated with intravenous rehydration and antibiotics. Additional severe hypernatremia, mild metabolic acidosis and renal failure were ascribed to dehydration. Because of persisting somnolence, dystonia, hyperthermia, hypernatremia and metabolic acidosis despite adequate treatment, laboratory evaluation was extended. Severe rhabdomyolysis was noted. Oral baclofen was added until dysfunction and disconnection of the ITB pump was excluded and acute baclofen withdrawal was ruled out. Neuroleptic malignant syndrome (NMS) was diagnosed. Tetrabenazine was stopped, and replaced by diazepam. The patient recovered within 11 days under supportive therapy. NMS is a potentially life threatening disorder characterized by hyperthermia, autonomic instability, mental status change and rigidity as well as multiple additional findings such as elevated CK levels, electrolyte abnormalities and leukocytosis. Important differential diagnoses include acute systemic or central nervous infection, acute baclofen withdrawal, serotonin syndrome and malignant hyperthermia. Treatment of NMS consists in removing the causative agent and aggressive supportive care. Acute baclofen withdrawal has to be considered in patients with an ITB pump and NMS in patients on neuroleptic agents presenting with an unclear clinical picture, as prompt recognition has important therapeutic consequences.