Delirium other diagnostic studies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vishal Khurana, M.B.B.S., M.D. [2]; Pratik Bahekar, MBBS [3]

Investigations

To identify underlying etiology following investigations are recommended:

• Complete blood count

• Serum Calcium

• Kidney function tests

• Electrolytes

• Liver function tests
• Blood sugar level
• Thyroid function tests
• Chest X‑ray
• ECG
• Blood cultures

• Urinalysis

If indicated:

• EEG

• CT head

• B12 and folate levels

• Arterial blood gases

• Specific cultures eg urine, sputum

• Lumbar puncture

EEG

EEG shows diffuse slowing. EEG is useful to differentiate delirium from following condtions:

• dementia

• non‑convulsive status epilepticus and temporal lobe epilepsy

• focal intracranial lesion, or it's a global abnormality.

As exact EEG changes in delirium are not yet identified, EEG is not used to diagnose delirium. Identification of the most informative electrode, and use of fewer electrodes will increase the usefulness of EEG in delirium. Continuous EEG monitoring has proven to be a feasible approach in the management of Epilepsy, therefore EEG beholds a great potential to improve detection rates of delirium. EEG changes in delirium are most prominent in the posterior regions. Delirium shows slowing of background activity, however, slowing of background activity is also observed in deep sleep and dementia. EEG recording of sleep shows K complexes and sleep-spindles whereas EEG recorded with eyes open (active EEG) in delirium have the relative power in the delta and the upper half of the alpha frequency band significantly different from dementia. These differences can be exploited to differentiate delirium from sleep and dementia.

There are many practical limitations of EEG studies in delirium. The exact effects of drugs like haloperidol on EEG are unknown, this poses a problem to study EEG characteristics of delirium, as haloperidol is the most widely used medicine in the management of delirium. Also, because of the very fluctuating nature of delirium, many studies suffer from time gap between diagnosis of delirium and EEG recordings.

the relative power of the theta frequency band was most frequently studied, and, without exception, different between delirium and non-delirium subjects.A future study should determine whether the relative power of the theta frequency band is indeed the most affected EEG characteristic.

Lumbar puncture

Routine LP does not provide any benefit in management of delirium. However,it's helpful in suspected meningitis, ie delirium with

• Meningism
• Headache and fever