What is the Difference Between Malignant Hyperthermia and Neuroleptic Malignant Syndrome?
🆚 Go to Comparative Table 🆚Malignant Hyperthermia (MH) and Neuroleptic Malignant Syndrome (NMS) are two distinct clinical syndromes that can present with similar symptoms, such as fever, muscle rigidity, and autonomic instability. Here are the main differences between the two:
- Causes: MH is an acute life-threatening hypermetabolic syndrome that occurs predominantly among people who have inherited a mutation of the Ryanodine receptor 1 gene. It is often triggered by exposure to depolarizing muscle relaxants or inhaled anesthetic agents. NMS, on the other hand, is a life-threatening neurologic emergency associated with the use of antipsychotic (neuroleptic) medications.
- Muscle Rigidity: The rigidity in NMS is often severe and "lead pipe," while the rigidity in MH is more variable.
- Reflexes: Patients with NMS typically exhibit hyporeflexia, whereas those with MH have normal or increased reflexes.
- Neuromuscular Hyperactivity: NMS patients may present with neuromuscular hyperactivity, such as clonus (involuntary muscle twitches), ataxia, and tremors, which differentiates it from MH.
- Diagnostic Criteria: The history of exposure to depolarizing muscle relaxants or inhaled anesthetic agents in MH makes the distinction clear in most cases.
While both syndromes share similar clinical features, their causes, muscle rigidity, reflexes, and neuromuscular hyperactivity can help differentiate between them.
Comparative Table: Malignant Hyperthermia vs Neuroleptic Malignant Syndrome
Malignant Hyperthermia (MH) and Neuroleptic Malignant Syndrome (NMS) are both life-threatening conditions that can present with hyperthermia, muscle rigidity, and autonomic dysfunction. Here is a table highlighting the differences between the two syndromes:
| Feature | Malignant Hyperthermia | Neuroleptic Malignant Syndrome |
|---|---|---|
| Cause | Genetic predisposition due to mutations in the skeletal muscle Ryanodine receptor 1 (RYR1) gene | Life-threatening idiosyncratic reaction to antipsychotic drugs |
| Triggers | Inhaled anesthetics given during surgery, such as halothane and isoflurane | Antipsychotic drugs, including newer atypical antipsychotics, and other medications that affect central dopamine receptors |
| Patient Population | Patients with genetic predisposition | Patients taking neuroleptic drugs, with an estimated incidence of 0.02 to 3% |
| Hyperreflexia | Absent | Present in NMS |
| Muscle Rigidity | Rigidity may be less severe than in NMS | Rigidity is often severe and "lead pipe" |
| Autonomic Instability | Fever, tachycardia, hypertension, and diaphoresis | Similar features, but NMS also includes altered mental status |
For MH, suspect the condition in a post-surgical patient who develops the acute onset of autonomic instability. In contrast, NMS is characterized by altered mental status, muscle rigidity, hyperthermia, and autonomic hyperactivity that occur when certain neuroleptic drugs are used. Diagnosing and treating these disorders promptly is crucial for reducing mortality rates and improving patient outcomes.
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