Confirmatory tests in the diagnosis of brain death: comparison between SPECT and contrast angiography

OBJECTIVE. Cerebral blood flow tests have increasingly been advocated for the confirmation of brain death (BD). The four-vessel angiography has been considered as the most reliable investigation in the diagnosis of BD for over thirty years, but is invasive. 99mTc-HMPAO SPECT provides a non-invasive, multiplanar imaging of brain tissue perfusion. The aim of this study is to check the reliability of SPECT comparing it to contrast angiography. DESIGN. Prospective, blind study. SETTING. Neurointensive Care Unit of a University hospital PATIENTS. Consecutive clinically brain dead patients with flat EEG. INTERVENTIONS. The diagnosis of brain death was performed according to the Italian law. 99mTc-HMPAO SPECT and four-vessel angiography were performed in the same session; the rater of each investigation ignored the results of the other. Blood pressure, SpO2 and PeCO2 were monitored throughout the study: any episode of hypoxia or hypotension caused the exclusion of the patient from the study. MEASUREMENTS AND MAIN RESULTS. 20 brain dead patients were enrolled. The cause of brain death was head injury in 7 cases (35%), subarachnoid haemorrhage in 6 (30%), spontaneous haemorrhage in 2 (10%), in brain tumors in 2 (10%), stroke in 2 (10%) and thrombosis of sagittal sinus in 1 (5%). Both angiography and SPECT confirmed BD in 19 out of 20 patients: angiography showed the absence of filling of intracranial arteries, while SPECT showed a picture of “empty skull”. In the remaining patient, angiography showed a slight and late filling of left vertebral, basilar and posterior cerebral arteries, while SPECT showed faint traces of uptake in the posterior fossa, on the right side and on the mid-line. In this patient, the tests were repeated 48 hs later and both showed the arrest of intracranial circulation, thus confirming BD. CONCLUSIONS. Our results confirm the reliability of SPECT in the diagnosis of brain death. Being non invasive, SPECT is a good candidate to become the gold standard of diagnosis.