Delirium other diagnostic studies

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

Overview

EEG and Lumbar puncture can be utilized in the management of delirium, however they are not always indicated.

Other Diagnostic Studies

1. EEG
2. Lumbar Puncture

EEG

• EEG shows diffuse slowing which is an indicator of delirium severity.
• EEG is useful to differentiate delirium from following conditions:

• Dementia
• Non‑convulsive status epilepticus and temporal lobe epilepsy

• Conditions that can be identified on EEG include:

• metabolic encephalopathy or infectious encephalitis
• Focal intracranial lesion, or it's a global abnormality.

• As exact EEG changes in delirium are yet to be 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 medicines in the management of delirium.
• One study observed an increase in the relative power of the theta and a decline in the relative power of the alpha frequency band, but this phenomenon seen to be absent when Parkinson is a co-morbid condition to delirium.
• More work needs to be done on the theta, alpha, and delta waves as many studies have disputed given findings.
• Delirium can also be identified from non delirium states by the following characteristics:

• Increase in the relative power of the delta frequency band
• Decrease in the peak frequency and significantly decreased bispectral index (BIS).

Neurophysiology

• Electroencephalography (EEG) is an attractive mode of study in delirium as it has the ability to capture measures of global brain function.
• There are also opportunities to summarise temporal fluctuations as continuous recordings, compressed into power spectra (quantitative EEG, qEEG).
• Delirium has been known to be associated with a generalised slowing of background activity.
• For most studies, the outcome of interest was the relative power measures, in order: alpha, theta, delta frequencies.
• The relative power of the theta frequency was consistently different between delirium and non-delirium patients.
• Similar findings were reported for alpha frequencies. In two studies, the relative power of all these bands was different within patients before and after delirium.

Lumbar puncture

• Routine LP does not provide any benefit in management of delirium. However,it maybe helpful in suspected meningitis when delirium is accompanied with:
• Meningism
• Headache and fever