[CT findings in chronic subdural hematomas (author's transl)].

CT findings of 46 patients with operatively confirmed chronic subdural hematomas are reviewed. The analysis of the EMI scans resulted in three different types of CT findings. Type 1 is characterized by decreased attenuation of the hematoma contents compared to brain tissue. The hematoma is visualized as a lens-shaped low density area between the skull and the surface of the brain. Type 2 apart from low density areas contains zones of increased attenuation due to recent bleeding into a watery chronic subdural hematoma. In many cases sedimentation causes a well-defined horizontal borderline between the thin fluid parts in the anterior portion and the blood debris in the posterior portion of the hematoma sac. Type 3 shows the same average absorption values as normal brain tissue, a direct visualization is not possible. However , the presence of a midline displacement in combination with ventricular compression and absence of a circumscript lesion even after contrast enhancement, allows the diagnosis of a unilateral chronic subdural hematoma in these cases too. Bilateral chronic subdural hematomas may cause considerable diagnostic difficulties if only one or none of the hematomas is visualized. A relatively small midline displacement points to a second bleeding on the opposite side. Most frequent were hematomas of type 1 (37%), type 2 and 3 could be observed in 30,5% resp. 32,5% of cases respectively.