Investigations

The extent of investigation should depend on the degree and duration of illness, the most likely causes and the clinical findings. In a patient who has an obvious cause for their catatonia or an established history of catatonia, minimal investigation beyond the basics might be appropriate.

Bedside investigations

Physical observations (pulse, blood pressure, respiratory rate, temperature, oxygen saturation). Repeat at least 3 times daily.
Food and fluid chart

Lorazepam challenge

If the diagnosis of catatonia is uncertain, the lorazepam challenge can help distinguish.

Assess for features of catatonia at baseline, ideally using a scoring system such as the Bush-Francis Catatonia Rating Scale.
Administer 1-2mg lorazepam by the intravenous, intramuscular or oral route.
Re-assess after 5 minutes (intravenous), 15 minutes (intramuscular) or 30 minutes (oral). A 50% improvement suggests that catatonia is likely and that there is likely to be a good response to further treatment with benzodiazepines.
If there is limited response, repeat the test with one further dose of lorazepam.

Blood tests

Full blood count
Electrolytes
Renal function
Bone profile
Liver function
Glucose
Thyroid function
Vitamin B12/folate
Creatine kinase
Iron
Copper and caeruloplasmin
HIV and syphilis serology
Antinuclear antibodies
Anti-NMDA receptor antibodies

Other

Urinalysis for ketones
Urine drug screen
Electrocardiogram
Neuroimaging (MRI preferred to CT)
Electroencephalograph (EEG)
Lumbar puncture