Case application for CT anatomy (1)

Interpret the following CT brain carefully.

Step-to-step interpretation :

This is very tempting to look directly at the whitish patches on the right cerebral hemisphere. However, always identify the normal anatomical landmarks can help you orientate yourself.

You can see the frontal horn of lateral ventricle ( A ) and also the occipital horn of the lateral ventricle with choroid plexus inside ( B ), however, no body of the lateral ventricle can be seen. Therefore, this image is at the layer of internal capsule where we can normally see the “angry face”.

Normally, the falx cerebri ( C ) should be at the mid-line. However, there is a mid-line shift to the left hemisphere, which is due to the intracranial hematoma ( D ) which is a kind of space-occupying lesion pushing brain parenchyma to the patient’s left side.

It is interesting to note the following minor evidence of increased intra-cranial pressure other than the presence of large hematoma ( D ) :
1. The sulcus e.g. lateral sulcus is hardly seen due to squeezing of brain parenchyma by the hematoma.
2. 2. The “eye” and the “mouth” are completely obliterated at the right cerebral hemisphere as the hematoma is located at that side.

There is a learning point about intracranial hemorrhage. It can be divided into intra-axial and extra-axial ( axial structure meaning the CNS i.e. the brain ). In this case, the blood is originated from the periphery extending to the central region, suggestive of extra-axial bleeding.

Extra-axial bleeding is further sub-divided into :
1. Epidural
2. Subdural
3. Subarachnoid hemorrhage

Subarachnoid hemorrhage is the easiest one to be distinguished as it shows whitish density filled the CSF-filled spaces like the subarachnoid space, ventricles and cisterns.

While epidural and subdural hemorrhage looks alike except epidural hematoma has a lenticular shape, while subdural hemorrhage has a crescentic shape.

Both hematoma will gradually grow in size both along the dura mater and also press against brain parenchyma in a perpendicular direction. The epidural hematoma cannot extend across suture lines as the dura mater is firmly attached to the inner surface of skull bone, so it mainly presses inwards onto the brain paenchyma; While the subdural hematoma can extends laterally across suture lines. The above difference may explain the difference in the shape of the epidural and subdural hematoma. Besides, epidural hematoma cannot extend along dura mater across sutures while subdural hematoma does not have such a restriction. In this case, we can see a large intra-axial hematoma with a crescentic shape that cross the coronal and lambdoid sutures.

Therefore, this is a case of right subdural hematoma complicated by mid-line shift of the cerebrum.