Why are CT scans of the brain still important?
Please do not skip a CT scan and go for an MRI in patients that you suspect have had a stroke and/or haemorrhage.
Sudden headache and altered mentation is one dramatic neurological presentation.
Major possibilities include stroke, bleeding, and meningitis.
You do not need long years of practice in emergency neurology to know that one of the above diagnoses can easily be misdiagnosed for the other. Unless you approach your patient in a standard way you can fall a victim to the same diagnostic tools that are supposed to help you.
I would like to share a couple of clinical neuroimaging tips I feel important to be aware of if you are working with acute neurology.
Do not skip a CT scan step and go for an MRI in your suspected stroke/haemorrhage patients: I used to work in a tertiary centre where access to MRI on Emergency is not an issue. Subarachnoid haemorrhage, as well as small size parenchymal haemorrhage, and subdural haematomas can be potentially missed.
Case 1
Believe it or not: This 90-year-old gentleman has a chronic subdural haematoma over the right hemisphere. Can you see it on T1 (left image) or on FLAIR (right image)? On a CT scan, you can never miss this trick.
Case 2
I used to mix tentorium lesions with subarachnoid haemorrhage:
The tentorium is a dural fold between the hemispheres of the brain and the posterior fossa. A lot of drama takes place around the tentorium, but you need to well orient yourself with its cross-sectional anatomy to recognize various pathologies around it. It is hard to visualize the tentorium in the usual axial CT slices, you need to view it in another anatomical plane, preferably the coronal plane.
Subdural haematomas can occur between the tentorium layers and unless you recognize the tentorium very well, you can misdiagnose it as a subarachnoid haemorrhage.
Axial CT scan shows doubtful subtle hyperdensity in this 80-year-old gentleman with a headache and a history of falling.
Coronal slices can confidently show the asymmetry of the two tentorial leaflets
The following are the same pictures with annotations.
Author: Dr Mohammad Aboulwafa, MD, FEBN, Neurology Clinical Research Fellow, Royal London Hospital.