|Print Date:||May 24, 2013, 12:35 am|
|Text||Brain death is defined as the complete and irreversible cessation of brain function. The term is primarily a clinical diagnosis and includes:
1. Total absence of brainstem reflexes or spontaneous respirations
2. Potentially reversible causes must be excluded
3. Cause of brainstem dysfunction must be diagnosed
4. Findings of BD must be present for a defined period of observation (6-24 hours)
However, ancillary studies may be used, including the neurologic exam, electroencephalography, cerebral angiography, and cerebral scintigraphy. Cerebral scintigrahy is especially helpful as it is relatively non-invasive and is not affected by drug intoxication or hypothermia. The preferred radiopharmaceuticals are Tc99m HMPAO and Tc99m ECD. Diagnostic findings are the lack of intracranial arterial flow, no visualization of major venous sinuses, and no visualization of the brain parenchyma. The pathophysiology behind this study is based on the intracranial pressure exceeding cerebral perfusion pressure. A marker of increased intracranial pressure is demonstrated by the "hot nose" sign where the elevated intracranial pressure diverts intracranial blood flow into the external carotid artery and results in increased flow to the face and nose. This finding supports brain death.
|References:||Mettler, F. Essentials of Nuclear Medicine. 5th Edition.Saunders, 2006.
Ziessman, H. Nuclear Medicine: Requisites. 3rd Edition. Mosby, 2006.
|Contributor||Jenny Ryan (National Capital Consortium)|
|Peer Reviewer||James G. Smirniotopoulos, M.D. (Uniformed Services University)|
|Record Number||: 9313|
|Category:||Clinical Exam Finding or Sign|
|Location:||Brain and Neuro|
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