This is a serious complication of many conditions that affect the brain. The cranial forms a rigid cavity enclosing; the brain,the cerebral blood vessels and cerebrospinal fluid(CSF). An increase in volume of any one of these will lead to raised intracranial pressure(ICP).
Sometimes its affects are more serious than the condition causing it,eg. by disrupting the blood supply or distorting the shape of the brain,especially if the ICP rises rapidly. A slow rise of ICP allows time for compensatory adjustment made,ie, a slight reduction in the volume of circulating blood and of CSF. The slower the rise in ICP,the more effective is the compensation .
Rising ICP is accompanied by bradycardia and hypertension. As it reaches the limit a further small increase in pressure is followed by a sudden and usually serious reduction in the cerebral blood flow as autoregulation fails. The result is hypoxia and a rise in carbon dioxide levels,causing arteriolar dilation,which further increases ICP. This leads to progressive loss of functioning neurones,which exacerbates bradycardia and hypertension.
The causes of increased ICP include:
- Cerebral oedema.
- Hydrocephalus,the accumulation of excess CSF.
- Expanding lesions include the skull,also known as space-occupying lesions.
- Haemorrhage.
- Tumours.
