Abstract

Brain death, defined as the irreversible cessation of all brain function, is a critical and often urgent diagnosis with significant implications for patient care, organ transplantation, and ethical decision-making. While Digital Subtraction Angiography (DSA) of the four cerebral vessels is considered the gold standard due to its near-perfect sensitivity and specificity, its use is limited by the need for specialized equipment, skilled personnel, and time-intensive protocols. Nuclear medicine scintigraphy has emerged as a valuable ancillary modality, offering a more accessible and objective approach. Utilizing the radiopharmaceutical Technetium-99m hexamethylpropyleneamine oxime (Tc-99m HMPAO), scintigraphy assesses cerebral perfusion by detecting gamma radiation from tracer uptake in viable brain tissue. In the setting of brain death, uptake is absent in intracranial regions, resulting in the characteristic “empty light bulb sign,” often accompanied by increased uptake in the external carotid arteries. This pattern highlights the redirection of flow from the internal carotid system due to intracranial circulatory arrest. The primary advantage of scintigraphy lies in its objectivity, especially in cases where clinical examination is unreliable—such as in the presence of sedatives, paralytics, or confounding metabolic factors. As a result, nuclear medicine scintigraphy serves as a practical, efficient, and non-invasive confirmatory tool, particularly in complex or ambiguous cases of suspected brain death.