Idiopathic intracranial hypertension

Did You Know?

• Drug-induced intracranial hypertension (DIIH) is a term suggested by a 2020 systematic review for cases likely caused by certain medications.
• Common causes of secondary intracranial hypertension include obstructive sleep apnea, systemic lupus erythematosus, chronic kidney disease, and Behçet's disease.
• The Monro–Kellie rule states that intracranial pressure is determined by the amounts of brain tissue, cerebrospinal fluid, and blood within the cranial vault.

Signs and symptoms

Severe headache occurs in nearly all cases (92–94%), typically worse in the morning, generalized, and throbbing. It may be accompanied by nausea and vomiting, and is aggravated by coughing or sneezing. Pain can also involve the neck and shoulders. Pulsatile tinnitus—a whooshing sound synchronous with the pulse—is reported in 64–87% of individuals. Less common symptoms include numbness of the extremities, generalized weakness, facial pain or numbness, loss of smell, and loss of coordination. In children, nonspecific signs may appear. Elevated pressure compresses cranial nerves, most often the abducens nerve, causing horizontal double vision that worsens when looking toward the affected side. The oculomotor and trochlear nerves are more rarely involved, affecting eye movements. Facial nerve involvement leads to partial or total weakness of facial muscles on one or both sides. Papilledema, swelling of the optic disc, occurs in nearly all cases. Those affected may experience transient visual obscurations—episodes of difficulty seeing in both eyes. Long-term untreated papilledema causes peripheral vision loss that progresses toward central vision.

Diagnosis

Diagnosis is suspected from history and examination, then confirmed by investigations that exclude other causes. Neuroimaging with CT or MRI typically appears normal in IIH, though signs such as slit-like ventricles, optic nerve sheath dilatation, empty sella sign, and enlargement of Meckel's caves may be seen. MR venography is often performed to rule out venous sinus stenosis or thrombosis. Lumbar puncture measures opening pressure and examines cerebrospinal fluid (CSF); in IIH, opening pressure is elevated, and CSF cell counts, infection markers, antibody levels, glucose, and protein are all normal. Occasionally, pressure may be normal despite suggestive symptoms, possibly due to daily fluctuations; if suspicion remains high, longer-term ICP monitoring via a pressure catheter may be needed. The original diagnostic criteria were described by Dandy in 1937.

Treatment

The primary goal is preventing visual loss and controlling symptoms. Treatment reduces CSF pressure through three main approaches: weight loss, medications, and surgery. Remission occurs in most patients who lose 6–10% of body weight; bariatric surgery is an option if lifestyle changes fail. Initial symptom control often involves CSF drainage via lumbar puncture, which may be done during diagnostic LP. If symptoms recur, repeated punctures may be needed, especially if vision deteriorates rapidly, though they are unpleasant and risk spinal infection. The best-studied medication is acetazolamide, which reduces CSF production by 6–57% but can cause hypokalemia, muscle weakness, and tingling; it is contraindicated in pregnancy due to embryonic abnormalities in animal studies and can cause metabolic acidosis and electrolyte disturbances in newborns. Furosemide is used if acetazolamide is not tolerated, though it often has little effect on ICP. Analgesics such as paracetamol, low-dose amitriptyline, or topiramate may help headache pain. Steroid use is controversial; they may be used in severe papilledema but are otherwise discouraged.

History

The first report of IIH was by German physician Heinrich Quincke in 1893, who called it serous meningitis. The term pseudotumor cerebri was introduced in 1904 by Max Nonne. Many subsequent cases likely had underlying causes; for example, otitic hydrocephalus reported by Sir Charles Symonds may have resulted from venous sinus thrombosis due to middle ear infection. Walter Dandy developed diagnostic criteria in 1937 and introduced subtemporal decompressive surgery. The name benign intracranial hypertension was adopted in 1955 to distinguish it from life-threatening causes, but was revised in 1989 to idiopathic intracranial hypertension because the condition can cause blindness. Shunt surgery began in 1949 with ventriculoperitoneal shunts; lumboperitoneal shunting showed good results in 1971. After negative reports on shunting in the 1980s, optic nerve fenestration became more popular from 1988 to 1993, but shunting is now recommended in most cases.