Which ancillary tests are available for diagnosis of brainstem death?

Measures of brain Electrical Activity

EEG

Most popular and validated test worldwide, though there has been a recent move away
Isoelectric EEG may be mimicked by conditions such as hypothermia, barbiturates, or other central nervous system (CNS) depressants - hence it is of little value when these are suspected

Somatosensory or Auditory Evoked Potential (SSEP)

A peripheral stimulus given (i.e. median nerve} and a response is measured at the contralateral primary sensory cortex
Absence of transmission measured 20 ms (N20 response) after stimulation suggests brainstem dysfunction
May be useful where coma of toxic aetiology is suspected - short-latency responses that are absent in brain death but preserved in toxic and metabolic disorders

Measures of Blood Flow

Cerebral Angiography
(4 vessel)

Contrast medium is injected in the aortic arch under high pressure to reach both anterior and posterior circulations
Confirmatory testing demonstrates absence of intracerebral filling beyond the carotid or vertebral arteries' entry to the skull

Transcranial Doppler

Useful only if a reliable waveform is found
Complete absence of flow may not be reliable if inadequate windows exist
Confirmatory testing should demonstrate either reverberating flow or small systolic peaks in early systole

Cerebral Scintigraphy

Non-invasive and safe measure of cerebral blood flow
No patient transport required if a portable gamma camera is available
Technetium 99 m is given by intravenous bolus with images obtained by a gamma camera every 3 seconds for a total of 60 seconds
External carotid flow is either digitally subtracted or excluded by forehead tourniquet
Confirmatory testing demonstrates no radionuclide localization in the middle cerebral artery, anterior cerebral artery, or basilar artery territories of the cerebral hemispheres

Spiral CT or MRI angiography

Increasingly available and investigated as ancillary tests
Confirmatory testing demonstrates absence of intracerebral filling beyond the carotid or vertebral arteries' entry to the skull