Small hyperdense streak lesions, indicating a small subdural hematoma, on the initial CT scan may thus have falsely been interpreted as the commonly encountered beam hardening artefacts. Such difficulties are present in any patient, and it is likely that small infratentorial subdural hematomas commonly remain unrecognized. In our patient, however, coagulation was - iatrogenically - severely impaired, and the small subdural hematoma that would have been clinically inconsequential under normal circumstances, turned into a life-threatening complication.