MCQ,Neurology Answer 27

The Correct Answer is D

Raised intracranial pressure could be the result of the following:

1 Increase of the volume of the normal content of the intracranial cavity, as increase in the volume of CSF as in hydrocephalus ,increase in the volume of the brain tissue itself as in brain oedema or increased cerebral blood volume.

2 Extra volume added to the intracranial cavity as in tumours or haematomas.

Where an extra volume is added to the intracranial cavity this has to be at the expense of the normal contents. To start with the cerebrospinal fluid is squeezed out, we find that the ventricles become compressed and displaced. There will be paucity of subarachnoid spaces and the basal cisterns become less discernible. Once a state is reached where no more CSF could be expulsed, a change in the cerebral blood flow occurs. As mentioned cerebral blood perfusion is related to intracranial pressure. With the rise of intracranial pressure there is diminished cerebral blood flow and more space is provided for the extra volume. However a state would be reached where any further decrease in cerebral blood flow would lead to cerebral ischaemia. In this situation the brain itself starts to herniate through the hiatus of the tentorium and foramen magnum. At this stage the patient’s condition is precarious and needs urgent action to reduce the intracranial pressure.

Increase blood volume can occur as a result of a blockage to venous drainage from the cranial cavity or due to vasodilatation. It is very important to appreciate that cerebral blood vessels are very sensitive to changes in blood gases especially carbon dioxide. High pco2 results in vasodilatation and increase in cerebral blood volume.

Category: Neurology MCQs