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Neuroradiology Case of the Week

Case 469

January 2010

Benita Tamrazi, MD and Jeevak Almast, MD

Clinical Presentation: Patient is an 78-year-old male with headache status post-head trauma.

Imaging Findings: Anterior interhemispheric fissure hyperdensity with prominence of the extra-axial subarachnoid space seen on non-contrast CT. On contrast enhanced CT, bilateral subdural hematomas are visualized.

Diagnosis: Subdural hematoma that is visualized after contrast

Discussion: Subdural hematomas are a result of tearing of the bridging veins which are located between the cortical veins and the dural sinuses. In the acute phase, subdural hematomas appear as hyperdense, crescent shaped extra-axial collections. In the subacute phase, they become isodense. This is a known limitation for diagnosis using non-contrast CT. For this reason, either contrast enhanced CT or MRI is often recommended for imaging 48-72 hours after head injury. The difficulty in visualizing isodense subdural hematomas is secondary to similar absorption values between the fluid collection and adjacent parenchyma. This typically occurs during the intermediate stage of development between 30-90 days after initial insult. Using contrast however can be helpful in visualizing the isodense subdural hematomas. On contrast enhanced CT scans, cortical veins over the cerebral surface are opacified and help delineate the abnormality. Typically scans obtained after intravenous contrast administration will show enhancement in at least 40% of cases where the fluid collections were not visualized initially on non-contrast CT scans. This is significant in reducing the morbidity and mortality of subdural hematomas that go undetected otherwise.

References:

1. Amendola MA, Ostrum BJ. Diagnosis of isodense subdural hematomas by computed tomography. AJR Am J Roentgenol. 1977 Oct;129(4):693-7. PMID: 409245 [PubMed]
2. Castillo M. The Core Curriculum: Neuroradiology. Lippincott Williams & Wilkins, 2002: 263.
3. Gean AD. Imaging of Head Trauma. Lippincott Williams & Wilkins, 1994.