Neuroleptic malignant syndrome caused rigidity

Antipsychotic drugs include the older phenothiazines and butyrophenones, as well as newer atypical drugs. All of these can cause CNS depression, seizures, and hypotension. Some can cause QT prolongation. The potent dopamine D2 blockers are also associated with parkinsonian-like movement disorders (dystonic reactions) and in rare cases with the neuroleptic malignant syndrome, characterized by "lead-pipe" rigidity, hyperthermia, and autonomic instability (see Chapter 29 Antipsychotic Agents Lithium). 

Rigidity may also be seen with a number of toxins and may be caused by CNS effects or spinal cord stimulation. Neuroleptic malignant syndrome and serotonin syndrome (see p 22) are characterized by rigidity, hyperthermia, metabolic acidosis, and an tered mental status. Rigidity seen with malignant hyperthermia (see p 22) is caused by a defect at the muscle cell level and may not reverse with neuromuscular blockade. 

Dantrolene is not likely to be effective for hyperthennia caused by conditions other than muscular hyperactivity, such as increased metabolic rate (eg, salicylate or dinitrophenol poisoning), neuroleptic malignant syndrome (NMS), impaired heat dissipation (eg, anticholinergic syndrome), or environment exposure (heat stroke). However, there is anecdotal evidence (case reports or case-control studies) of benefit for the management of NMS, MAO inhibitor (phenelzine poisoning)-induced hyperthermia, muscle rigidity from baclofen withdrawal, hypertonicity from carbon monoxide poisoning, tetanus, and black widow spider envenomation. 

Among the complications of neuroleptic chemotherapy, the most serious and potentially fatal complication is malignant syndrome, which is characterized by extreme hyperthermia lead pipe skeletal muscle rigidity that causes dyspnea, dysphagia, and rhabdomyolysis autonomic instability fluctuating consciousness leukeocytosis and elevated creatine phosphokinase levels. 

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