Idiopathic intracranial hypertension (pseudotumor cerebri) is a cause of increased ICP with normal brain imaging.Patients exhibit a daily debilitating headache associated withdiplopia, abducens palsy, transient visual obscurations, and papilledema. If untreated, permanent visual field loss may develop.The syndrome has been associated with ingestion of medications(tetracycline, vitamin A, oral contraceptive agents) and endocrinedisturbances (thyroid disease, Addison disease). Most commonly,this condition is idiopathic and affects children who are otherwise well except for being overweight, with rapid weight gain being a predisposing factor. Treatment including acetazolamideor other diuretic, topiramate, or corticosteroids, is generally effective. Weight loss and cessation of triggering medications are alsomainstays of treatment. Infrequently, chronic papilledema frompersistent idiopathic intracranial hypertension produces visualimpairment, and more aggressive management is required (opticnerve fenestration) to preserve visual function.
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The symptoms and signs of increased ICP include headache,vomiting, lethargy, irritability, altered consciousness, sixthnerve palsy, strabismus, diplopia, and papilledema. Headaches suggestive of increased ICP are those associated withnocturnal wakening; worse in the morning; with cough, micturition, defecation, or Valsalva maneuver; or progressivelyworsening. Infants who have an open fontanelle usually donot develop papilledema or abducens palsy. Specific signsof increased ICP in infants consist of a bulging fontanelle,suture diastasis, distended scalp veins, a persistent downward deviation of the eyes (sunsetting), and rapid growth ofhead circumference. Specific signs of increased ICP in theinfratentorial compartment (posterior fossa) include stiffneck and head tilt. Focal neurologic deficits reflect the siteof the lesion that is producing the increased ICP and mayinclude hemiparesis from supratentorial lesions, or ataxiaand cranial nerve palsies from infratentorial lesions. Critically increased ICP may result in herniation syndromes, as discussed earlier. In addition, the Cushing triad of elevated blood pressure, bradycardia, and irregular respirations is a late sign of critically elevated ICP.
The clinical manifestations of hydrocephalus are caused byventricular distention and increased ICP. Dilation of the lateral ventricles stretches the corticopontocerebellar and corticospinalpathways, resulting in ataxia and spasticity that initially are mostmarked in the lower extremities because the leg fibers are closestto the ventricles. Distention of the third ventricle may compressthe hypothalamic regions and result in endocrine dysfunction.The optic nerves, chiasm, and tracts also are in proximity to theanterior third ventricle, and visual dysfunction results whenthese structures are compressed. Dilation of the cerebral aqueduct compresses the surrounding periaqueductal vertical gazecenter, causing downward deviation of the eyes. Manifestationsof increased ICP may evolve slowly when obstruction is not complete and there is time for transependymal absorption of CSF intothe veins, or rapidly when obstruction is abrupt and complete(subarachnoid hemorrhage) and compensation cannot occur.