EEG maybe helpful for the diagnosis of delirium. 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.

1. EEG
2. Lumbar Puncture

• EEG shows diffuse slowing which is an indicator of delirium severity.^[1]
• EEG is useful to differentiate delirium from following conditions:

• Dementia^[2]
• 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:^[1]

• 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.
• Typical and atypical antipsychotic may cause EEG abnormality.^[3]

• 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.^[4]
• 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).^[5]

• Delirium has been known to be associated with a generalised slowing of background activity.^[6][7]
• The relative power of the theta frequency and alpha frequencies was consistently different between delirium and non-delirium patients.

• Routine LP does not provide any benefit in management of delirium. However,it maybe helpful in suspected meningitis when confusion is accompanied with:^[8]

• Meningism
• Headache and fever