A 42-year-old male presents to A&E feeling unwell for the past 48 hours. He feels feverish and is concerned as he has developed a tremor. He was recently diagnosed with schizophrenia and commenced on medication last week, but he cannot remember the name or the dose. On examination, there is evidence of muscle rigidity. His AMTS is 4/10. His vital signs are: HR 103bpm, RR 21 breaths per min, O2 saturations on air 98%, BP 138/82mmHg, temperature of 38.5.

Which of the following investigations is likely to aid the diagnosis?

Options:
explanation: This is incorrect because lithium levels are taken if there are concerns regarding a lithium overdose. Lithium is a mood stabiliser indicated for the long-term treatment of bipolar disorder. This question stem states that this patient has Schizophrenia. It is important to note that therapeutic levels of lithium is associated with a fine tremor whereas a coarse tremor is associated with lithium toxicity. Other features of lithium toxicity include ataxia and seizures.
name: Lithium levels
label: b
answer: no
explanation: This is incorrect because imaging is not routinely used to diagnose neuroleptic malignant syndrome. It can be used to exclude other conditions such as structural lesions within the brain, intracranial haemorrhage, or trauma. These are examples of differential diagnoses for NMS which can cause a change in mental state and extra-pyramidal symptoms. However, NMS should be the primary differential in this case given evidence of recent treatment with neuroleptics, hyperthermia, and muscle rigidity.
name: CT Head
label: e
answer: no
explanation: This is incorrect because blood tests are useful to show complications of NMS including acute renal failure secondary to rhabdomyolysis but they are not specific to the diagnosis.
name: Urea and electrolytes
label: d
answer: no
explanation: This is incorrect because an ECG is not likely to aid the diagnosis of neuroleptic malignant syndrome. It can show evidence of tachycardia because NMS can cause autonomic instability, but this is not specific.
name: Electrocardiogram
label: c
answer: no
explanation: This patient has neuroleptic malignant syndrome (NMS). Neuroleptic malignant syndrome is a life-threatening complication of taking dopamine antagonist medication. Most cases start within 4-14 days of commencing the medication, but some cases may occur many years after taking the same drug, at the same dose. It is likely this patient has been started on an antipsychotic medication, which has triggered his NMS. Clinical signs and symptoms include fever, muscle rigidity, confusion, rhabdomyolysis (hence the raised creatine kinase and subsequent electrolyte derangements such as hyperkalaemia and hypocalcaemia), metabolic acidosis, autonomic lability, and a raised white cell count. It takes up to 2 weeks to recover after stopping the medication. Treatment is with supportive measures (fluids, keeping the patient cool), dopamine agonists such as bromocriptine, or dantrolene.

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name: Creatine kinase
label: a
answer: yes

Correct answer: a


Learning point: Neuroleptic malignant syndrome is a life-threatening reaction to antipsychotic medications characterized by hyperthermia, muscle rigidity, altered mental status, and autonomic dysfunction, often with a significant elevation in creatine kinase levels due to muscle breakdown.