Case 1

This is a CT brain study with pre and post-contrast series, showing a left para-falcine crescentic hypodense extra-axial collection in the subdural space, which demonstrates peripheral rim enhancement on the post contrast images. The adjacent superior sagittal sinus appears to opacify normally, ruling out sinus thrombosis. These findings are in keeping with a subdural collection, most likely an empyema / collection of pus. The differential diagnosis includes subdural hygroma / haematoma. I would urgently contact the referring physician and inform them of the findings. I would recommend an urgent brain MRI for further investigation.

This is an MRI brain study with post contrast series, which shows the collection to be hyperintense on T2 and hypointense on T1. It demonstrates restricted diffusion, appearing bright on DWI with corresponding low ADC values. Again, there is peripheral rim enhancement on post-contrast series.

These findings are characteristic of a subdural empyema. I would urgently discuss the case with the referring physician and recommend urgent referral to the neurosurgical service.

There is also an incidental well defined midline lesion in the posterior fossa matching CSF signal intensity on all sequences, characteristic of an arachnoid cyst.