Raised intracranial pressure

Chapter 55 Raised intracranial pressure

General features of raised intracranial pressure

Headache (see Chapter 108)

Headache is the most common symptom of a brain tumor causing RICP by the time of hospital admission, but is a rare presenting symptom. Because headache is such a common symptom it accounts for many referrals because of concerns about the possibility of RICP. Brain tumor headaches may be intermittent, non-specific, and indistinguishable from tension headaches. A number of features are suggestive of RICP:

Brain tumors cause RICP by a variety of mechanisms. They may grow so large, so quickly that they cause stretching of pain-sensitive intracranial structures by a direct mass effect or by an effect on the microvasculature leading to cerebral edema. Tumors may also cause RICP by producing large cysts. Smaller tumors, particularly those in the posterior fossa, may cause headaches by obstructing cerebrospinal fluid circulation and producing hydrocephalus. Headaches with migrainous features are rarely due to an underlying tumor. Occipital tumors may produce occipital seizures, similar in some respects to migraine.

RICP may lead to gradual deterioration in cognition, intermittent drowsiness, and eventually coma. Progressive herniation of the medial temporal lobe across the tentorium causes an ipsilateral third nerve palsy; herniation of the cerebellar tonsils through the foramen magnum leads to coma and death.

Hydrocephalus and shunts

Hydrocephalus is RICP associated with dilated lateral ventricles. This is due to an imbalance between secretion of CSF in the choroid plexus within the lateral ventricles, and reabsorbtion from the arachnoid villi in the subarachnoid space. Causes are classified as:

Hydrocephalus may be congenital or acquired. Congenital hydrocephalus is one of the most frequent congenital abnormalities of the CNS and a common complication of spina bifida and neural tube defects. Other causes include cerebral aqueduct stenosis, Chiari malformation, and Dandy-Walker syndrome. Common causes of acquired hydrocephalus include meningitis and intraventricular hemorrhage in preterm infants.

The features of hydrocephalus depend on the age of the child and whether the RICP is acute in onset. When the cranial sutures have not closed, there is a progressive increase in skull growth with separation of the sutures. The fontanel is tense and scalp veins are dilated due to compression of the cortical veins and sinuses. If the ventricles are greatly enlarged, the skull may transilluminate. There may be failure to thrive and developmental delay. Papilledema is uncommon but the “setting-sun” sign – upper-lid retraction and downwardly deviated eyes due to upgaze paresis – may be seen in infants. In later childhood, papilledema is typically present often accompanied by unilateral or bilateral sixth nerve paresis and upgaze impairment.

Ventriculo-peritoneal shunt insertion is the most commonly performed pediatric neurosurgical procedure. In a series from the United States, 69 000 discharges and 36 000 procedures related to shunts were performed in 1995. The population with hydrocephalus has grown considerably since that study due to improved survival of very premature infants. The morbidity due to complications remains significant. In one UK series, there was a 11% mortality rate during a 10-year follow-up study of 155 children.1

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Jun 4, 2016 | Posted by in OPHTHALMOLOGY | Comments Off on Raised intracranial pressure

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