There is an isodense subdural haematoma on the right. The margin of the haematoma is not clearly seen but there are several clues:
On the first image there are bilateral subdural haematomas, with mixed attenuation, suggesting some older and some more recent haemorrhage. As the haematomas are bilateral there is no significant midline shift.
On the second scan the haematomas have decreased in size, but the ventricular system is now dilated. There is an intraventicular shunt present.
The patient presented with chronic hydrocephalus, with secondary cerebral atrophy. A shunt was inserted to treat the hydrocephalus. The rapid reduction in the hydrocephalus led to shrinkage of the brain from the cranial vault, resulting in rupture of dural veins and the subdural haematomas (image 1). These cause mass effect and obscure the dilated ventricles, which only become apparent again (image 2) when the haematomas begin to resolve.
This is a recognised complication of treating long standing hydrocephalus.
And that concludes this tutorial. Feedback is always welcome in the Guest Book, or by e-mail, below.
Dr A C Downie
Victoria Infirmary, Glasgow
andrew@radiology.co.uk