Close, but not close enough....
Subdural haemorrhage is caused by bleeding from the veins which bridge between the cortex and venous sinuses. It results in a haematoma (a collection of blood). The signs and symptoms are that of a slowly evolving stroke: physical and intellectual slowing, sleepiness or fluctuating conscious level, unsteadiness, headache, raised intracranial pressure. The CT scan would have picked up the haematoma, whereas in this case nothing showed up. Diagnosing a subdural haemorrhage is important as it is readily treatable, unlike other causes of strokes.
Try again, thinking along the same lines.