DESCRIPTION

• Idiopathic intracranial hypertension (IIH) is characterized by the presence of elevated intracranial pressure (ICP) in the absence of any other identifiable etiology, such as infection or mass lesion. It is most typically found in women of childbearing age who are overweight, although it can affect other populations as well.
• Clinical evidence of increased ICP includes headaches, vomiting, and vision changes.
• Neurologic exam is normal aside from potential cranial nerve abnormalities associated with increased ICP (e.g., papilledema or abducens palsy).
• Lumbar puncture reveals elevated opening pressure but otherwise normal cerebrospinal fluid (CSF) profile.
• Neuroimaging is normal or may show findings associated with increased ICP (e.g., flattening of the posterior sclera, empty sella, or optic nerve changes).

EPIDEMIOLOGY

• Annual incidence is ~1 to 2 per 100,000/year in the general population.
• Increased annual incidence in obese women ages 15 to 44 years (4 to 21 per 100,000/year)
• More women than men are affected in the adolescent and adult populations; in childhood, boys and girls are equally affected.
• Reported in patients as young as 4 months and as old as 88 years of age

ETIOLOGY

Numerous precipitants of IIH have been reported. In adolescents and adults, it is clearly associated with obesity and weight gain but is not linked to obesity in prepubertal children. Many weaker associations may be due to chance.

RISK FACTORS

PATHOPHYSIOLOGY

The exact pathogenesis is unclear. Various etiologies have been theorized, including decreased CSF absorption (possibly owing to arachnoid villi dysfunction), abnormalities of CSF outflow, abnormalities of cerebral venous outflow, or other causes of elevated intracranial venous pressure. For example, obesity may lead to increased intra-abdominal, intrathoracic, and cardiac filling pressure, leading to elevated intracranial venous pressure. Altered sodium and water retention mechanisms and abnormalities of vitamin A metabolism have also been proposed.

COMMONLY ASSOCIATED CONDITIONS

• IIH has been linked to the use of certain medications including tetracyclines, retinoids, and growth hormone.
• Other medications with possible links to IIH include thyroid replacement therapy, lithium, trimethoprim-sulfamethoxazole, fluoroquinolones, and nitrofurantoin.
• Systemic conditions associated with IIH include obstructive sleep apnea, vitamin A deficiency or intoxication, corticosteroid excess or withdrawal, chronic anemia, coagulation disorders, hypothyroidism, hypoparathyroidism, and uremia.