Raised Intracranial Pressure

CLINICAL EFFECTS OF RAISED INTRACRANIAL PRESSURE

A raised ICP will produce symptoms and signs but does not cause neuronal damage provided cerebral blood flow is maintained. Damage does, however, result from brain shift - tentorial or tonsillar herniation. Clinical features due to |ICP:

1. Headache - worse in the mornings, aggravated by stooping and bending.

2. Vomiting - occurs with an acute rise in ICP.

3. Papilledema - occurs in a proportion of patients with flCP. It is related to CSF

obstruction and does not necessarily occur with brain shift alone. Increased CSF pressure in the optic nerve sheath impedes venous drainage and axoplasmic flow in optic neurons. Swelling of the optic disc and retinal and disc haemorrhages result. Vision is only at risk when papilledema is both severe and prolonged.

BRAIN SHIFT - TYPES

TENTORIAL HERNIATION (lateral):

a unilateral expanding mass causes tentorial (uncal) herniation as \ the medial edge of the temporal lobe herniates through the tentorial hiatus. As the intracranial pressure continues to rise, 'central' herniation follows.

SUBFALCINE 'MIDLINE' SHIFT: occurs early with unilateral space-occupying lesions. Seldom produces any clinical effect, although ipsilateral anterior cerebral artery occlusion has been recorded.

TENTORIAL HERNIATION (central): a midline lesion or diffuse swelling of the cerebral hemispheres results in a vertical displacement of the midbrain and diencephalon through either from mechanical distortion or vessels.

TONSILLAR HERNIATION: a subtentorial expanding mass causes herniation of the cerebellar tonsils through the foramen magnum. A degree of upward herniation through the tentorial hiatus may also occur. Clinical effects are difficult to distinguish from effects of direct brainstem/midbrain compression.

the tentorial hiatus. Damage to these structures occurs from ischaemia secondary to stretching of the perforating

Unchecked lateral tentorial herniation leads to central tentorial and tonsillar herniation, associated with progressive brain stem dysfunction from midbrain to medulla.

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