Neuroleptic Malignant Syndrome

Introduction

Neuroleptic malignant syndrome is a life-threatening but rare complication of antipsychotic drugs. Often people mix it up with serotonin syndrome because they share some clinical features but they’re actually really different.

Antipsychotics are dopamine antagonists, so we really need to know what dopamine does in the first place to understand the pathophysiology of NMS. We all learn that there are four classic dopamine pathways.

The nigrostriatal, which helps controls motor function
The tuberoinfundibular, which contributes to a feedback system for prolactin in our anterior pituitary.
The mesolimbic, which controls our brain’s reward system and implicated in positive features of psychosis like hallucinations.
Finally, the mesocortical which controls executive functions and implicated in negative features of schizophrenia like avolition and social withdrawal.

However, its super important to remember that dopamine is used in lots of places and serious dysfunction can cause more general effects. For example, the hypothalamus relies on dopamine for thermoregulation and coordinating other autonomic functions.

Excessive dopamine antagonism causes the classic tetra of clinical features that come with Neuroleptic Malignant Syndrome.

Remember Dopamine is your MATE and without it you get a dysfunctional mental state, autonomic regulation, thermoregulation, and Extrapyramidal movement issues.

This comes in the form of an altered level of consciousness and drowsiness, Tachycardia and hypertension, hyperthermia with a temperature of more than 39ºC and parkinsonian features like bradykinesia, ‘lead-pipe’ rigidity, and tremor

Although neuroleptic malignant syndrome can occur any time during treatment with antipsychotic drugs, it usually occurs within 2 weeks of starting them or increasing the dose and develops over days. This is an important distinguishing feature from serotonin syndrome, which has a more rapid onset. Remember NMS causes rigidity and tremor. It looks like Parkinson’s. While serotonin syndrome causes hyperreflexia and clonus.

As I mentioned before, the way I remember the differentiating features of NMS and its manage is with “Scomo Bromo and Dantro”.

For those that don’t know, Scott Morrison also known as SCOMO was Australia’s prime minister between 2018 and 2022. Many thought he was slightly psychotic because he secretly appointed himself to five additional ministries during his time in office.

Other than helping me remember NMS is causes by antipsychotics, SCOMO is an acronym which highlights 5 differentiating features compared to Serotonin syndrome.

It tells me NMS has a slower onset, presents with a high creatinine kinase and is characterised by parkinsonian features like an oscillating resting tremor, bradykinesia or moving slowly, and really ossified and rigid hypertonia.

Bromo or Bromocriptine is the treatment and you can consider dantro or dantrolene afterwards too.