Lethal catatonia and neuroleptic malignant syndrome (NMS) have been suggested to have a common neurochemical cause. We hypothesise that both conditions may be due to a sudden and massive blockade of dopamine neurotransmitters.
NMS was diagnosed in psychotic in-patients treated with neuroleptics if four features were present: diffuse severe rigidity, altered level of consciousness, hyperpyrexia and autonomic instability.
Over three years, five NMS cases were diagnosed. Two presented with catatonic features and were diagnosed as acute reactive psychosis. Their neuroleptic doses were small, arguing for a particular sensitivity in these two cases.
The sensitivity of two patients with catatonic features who developed NMS with small doses of neuroleptics supports a common neurochemical basis for the two conditions.