Brain Death Perfusion Imaging⁹⁹ᵐTc-HMPAO / ECD (lipophilic) or ⁹⁹ᵐTc-DTPA (flow)
Confirming absent intracranial perfusion as an ancillary test
Quick Answer
Brain-death (brain circulatory arrest) scintigraphy is an ancillary confirmatory test used when clinical/apnea testing is inconclusive or confounded. Absence of intracranial perfusion supports the diagnosis. With a lipophilic tracer (Tc-99m-HMPAO/ECD), brain death shows no intracranial uptake — the classic "hollow skull" / "empty light bulb" sign — often with the "hot nose" sign (external carotid flow diverted to the face) and preserved scalp/superior sagittal sinus activity.
Principle
Lipophilic perfusion tracers cross the intact blood–brain barrier and fix in viable brain proportional to perfusion. In brain circulatory arrest there is no delivery to brain tissue, so the cranial vault is photopenic while extracranial (facial/scalp) structures still perfuse.
Findings supporting brain death
- No intracranial parenchymal uptake (hollow skull / empty light bulb).
- Hot nose sign — increased nasal/facial activity from external-carotid shunting.
- Absent flow to cerebral hemispheres, brainstem, and cerebellum.
An ancillary test with a clear positive finding
Brain-death scintigraphy is an ancillary confirmatory test — the diagnosis remains primarily clinical — used when clinical/apnea testing is inconclusive or confounded. With a lipophilic tracer (HMPAO/ECD), brain death shows no intracranial parenchymal uptake (the "hollow skull / empty light bulb" sign), often with the "hot nose" sign (external-carotid flow diverted to the face) and preserved scalp/venous activity.
Prove the tracer was delivered
Confirm scalp/superior-sagittal-sinus activity to prove the injection and bolus were valid — a failed injection or poor bolus can mimic absent perfusion. Lipophilic-tracer (parenchymal) methods are less confounded than pure flow studies, and SPECT increases confidence for the posterior fossa; rely on delayed parenchymal imaging in equivocal cases rather than flow images alone.
High-Yield Pearls
- It is an ancillary test — the diagnosis of brain death remains primarily clinical.
- Lipophilic-tracer methods assess parenchymal perfusion and are less confounded than pure flow studies; SPECT increases confidence for posterior fossa.
- Confirm scalp/venous activity to prove the tracer was delivered (a technically valid study).
Common Pitfalls
- A failed injection or poor bolus mimicking absent perfusion — verify extracranial delivery.
- Relying on flow-only (DTPA) images without delayed parenchymal imaging in equivocal cases.
Related Pages
- Related: brain perfusion SPECT (HMPAO/ECD); pitfalls: Pearls, pitfalls & normal variants.
Self-Check
Q1. Is brain-death scintigraphy the primary diagnosis or an ancillary test?
Answer: An ancillary confirmatory test — the diagnosis of brain death remains primarily clinical; scintigraphy is used when clinical/apnea testing is inconclusive or confounded.
Q2. Name the classic sign of absent intracranial perfusion on a lipophilic-tracer study.
Answer: The "hollow skull" / "empty light bulb" sign — no intracranial parenchymal uptake, often with the "hot nose" sign.
Q3. Why confirm scalp / superior-sagittal-sinus activity?
Answer: To prove the injection and bolus were valid — a failed injection can mimic absent perfusion.
Q4. Why are lipophilic-tracer (parenchymal) methods preferred over flow-only studies?
Answer: They assess parenchymal perfusion, are less confounded, and (with SPECT) give more confidence for the posterior fossa in equivocal cases.
Evidence & sources
https://nuc.med/brain-death-perfusion/ Report an issue