Raised intracranial pressure

The initial priority in the management of the unconscious child is the maintenance of adequate respiration, circulation, and metabolic homoeostasis. Once this has been done, the possibility of raised intracranial pressure should be considered.

In very young children, before the cranial sutures are closed, considerable intracranial volume expansion may occur if the process is slow. However, if the process is rapid and in children with a fixed volume cranium, increase in volume due to brain swelling, haematoma, or cerebral spinal fluid (CSF) blockage will cause raised intracranial pressure (ICP). Initially cerebrospinal fluid and venous blood within the cranium decrease in volume. Soon, this compensating mechanism fails and as the intracranial

Figure 12.1. Algorithm for the initial management of coma

pressure continues to rise the cerebral perfusion pressure (CPP) falls and arterial blood flow is reduced.

where MAP is mean arterial pressure. Reduced CPP reduces cerebral blood flow (CBF). Normal CBF is over 50ml/l00g brain tissue/min. If the CBF falls below 20ml/l00g brain tissue/min, the brain suffers ischaemia.

Increasing intracranial pressure will push brain tissue against more rigid intracranial structures. Two clinical syndromes are recognisable by the site of localised brain compression.

Central syndrome

The whole brain is pressed down towards the foramen magnum and the cerebellar tonsils herniate through it ("coning"). Neck stiffness may be noted. A slow pulse, raised blood pressure, and irregular respiration leading to apnoea are seen terminally.

Uncal syndrome

The intracranial volume increase is mainly in the supratentorial part of the intracranial space. The uncus, which is part of the hippocampal gyrus, is forced through the tentorial opening and compressed against the fixed free edge of the tentorium. If the pressure is unilateral (for example, from a subdural or extradural haematoma), this

Figure 12.2. Herniations of the brain

leads to third nerve compression and an ipsilateral dilated pupil. Next, an external oculomotor palsy appears, so the eye cannot move laterally. Hemiplegia may then develop on either or both sides of the body, depending on the progression of the herniation.



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