What are the symptoms of Neuroleptic Malignant Syndrome (NMS), specifically muscle rigidity and extrapyramidal (involuntary movement) signs?

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Last updated: March 16, 2025View editorial policy

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From the Guidelines

Neuroleptic Malignant Syndrome (NMS) is characterized by severe muscle rigidity, typically lead-pipe rigidity, and extrapyramidal signs, including tremor, dystonia, akinesia, and bradykinesia, which are life-threatening and require immediate medical attention. The symptoms of NMS, as described in the study by 1, include hyperthermia, altered mental status, muscle rigidity, and autonomic instability, with manifestations such as fever, tachycardia, blood pressure instability, diaphoresis, and dysphagia. The most common neurologic finding is lead pipe rigidity, although akinesia, dyskinesia, or waxy flexibility may be present.

Some key points to consider when evaluating a patient with suspected NMS include:

  • Muscle rigidity, which can range from lead-pipe rigidity to akinesia or dyskinesia
  • Extrapyramidal signs, such as tremor, dystonia, and bradykinesia
  • Hyperthermia, with fever up to 41°C or higher
  • Altered mental status, which can vary from alert mutism to agitation to stupor to coma
  • Autonomic instability, with symptoms such as tachycardia, blood pressure fluctuations, and diaphoresis

According to the study by 1, management of NMS involves primarily supportive care and removal of the initiating agent, with consideration of medications like benzodiazepines for agitation and external cooling measures for fever. Immediate discontinuation of the offending antipsychotic and supportive care are crucial in managing NMS, with a focus on reducing mortality and improving quality of life. It is essential to recognize the symptoms of NMS promptly and initiate treatment to prevent serious complications and improve outcomes.

From the Research

Symptoms of Neuroleptic Malignant Syndrome (NMS)

The symptoms of NMS include:

  • Hyperthermia
  • Muscle rigidity
  • Extrapyramidal disturbances (involuntary movement disorders)
  • Autonomic instability
  • Mental status changes
  • Elevated serum creatine kinase levels 2 Specifically, muscle rigidity and extrapyramidal signs are key features of NMS, often accompanied by hyperthermia, autonomic disturbances, and altered consciousness 3, 4, 5, 6

Extrapyramidal Signs

Extrapyramidal signs in NMS can include:

  • Restlessness
  • Tremor
  • Extrapyramidal motion disorder
  • Involuntary movements 4, 5

Muscle Rigidity

Muscle rigidity in NMS can lead to serious complications, such as:

  • Rhabdomyolysis (damage to muscle cells)
  • Myoglobinaemia (elevation of myoglobin in the blood)
  • Myoglobinuria (elevation of myoglobin in the urine)
  • Elevated serum creatine phosphokinase levels 4, 5

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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