The infant or child with increasing pressure within the cranial cavity must be identified early and treated promptly in order to prevent serious complications or death. When the pressure elevation is gradual it is frequently well tolerated, and the patient may seem deceptively well. There is a critical point, however, beyond which any further increase in pressure leads to a catastrophic deterioration in the patient's condition.1 When this occurs, the outlook for quality survival is poor despite the best therapy. Unfortunately, this can occur when the underlying process is benign and would have been reversible if recognized and treated promptly. For prompt recognition and treatment, the physician must be familiar with the pathophysiology of raised intracranial pressure.
PATHOPHYSIOLOGY
The intracranial compartment contains blood vessels, cerebrospinal fluid (CSF), brain, and leptomeninges which include the rigid dural membranes forming the falx and tentorium. Whenever there is an increase in the volume of any one of these intracranial components (brain, CSF, blood) there must be a corresponding reduction in the size of the others in order for the intracranial pressure to remain normal. This type of compensation or buffering capacity is particularly important in the early stages of intracranial disease. As the pressure mounts from any type of mass lesion, the CSF is displaced caudally into the spinal subarachnoid space and there is a corresponding increase in the rate of absorption of CSF.2
The thermoregulatory effects of noradrenaline, serotonin and carbachol injected into the rat spinal subarachnoid space
