Delirium other diagnostic studies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Zand, M.D.[2] Pratik Bahekar, MBBS [3]; Vishal Khurana, M.B.B.S., M.D. [4]

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.

• EEG findings associated with delirium include:

• Periodic discharges
• Triphasic waves
• lateralized rhythmic delta
• Low voltage/generalized attenuation
• Theta or delta generalized slowing

• The presence of either theta or delta generalized slowing correlated strongly with delirium severity regardless of arousal state (hyper- or hypoactive) and comorbidities.
• 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.
• 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.
• 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