IIH is diagnosed with a brain scan (to rule out other causes) and a lumbar puncture; lumbar puncture may also provide temporary and sometimes permanent relief from the symptoms. Some respond to medication (with the drug acetazolamide), but others require surgery to relieve the pressure. The condition may occur in all age groups, but is most common in young women, especially those with obesity.[1]
The most common symptom of IIH is headache, which occurs in almost all (92¨C94%) cases. It is characteristically worse in the morning, generalized in character and throbbing in nature. It may be associated with nausea and vomiting. The headache can be made worse by any activity that further increases the intracranial pressure, such as coughing and sneezing. The pain may also be experienced in the neck and shoulders. Many have pulsatile tinnitus, a whooshing sensation in one or both ears (64¨C87%). Various other symptoms, such as numbness of the extremities, generalized weakness, loss of smell, and incoordination, are reported more rarely; none are specific for IIH.[1] In children, numerous nonspecific signs and symptoms may be present.[2]
The increased pressure leads to compression and traction of the cranial nerves, a group of nerves that arise from the brain stem and supply the face and neck. Most commonly, the abducens nerve (sixth nerve) is involved. This nerve supplies the muscles that pull the eye outward. Those with sixth nerve palsy therefore experience horizontal double vision which is worse when looking towards the affected side. More rarely, the oculomotor nerve and trochlear nerve (third and fourth nerve palsy, respectively) are affected; both play a role in eye movements.[2][3] The facial nerve (seventh cranial nerve) is affected occasionally¨Cthe result is weakness of all face muscles on one side of the face.[1]
The increased pressure leads to papilledema, which is swelling of the optic disc, the spot where the optic nerve enters the eyeball. This occurs in practically all cases of IIH, but not everyone experiences symptoms from this. Those who do experience symptoms typically report "transient visual obscurations", episodes of difficulty seeing that occur in both eyes but not necessarily at the same time. Long-term untreated papilledema leads to visual loss, initially in the periphery but progressively towards the center of vision.[1][4]
Physical examination of the nervous system is typically normal apart from the presence of papilledema, which is seen on examination of the eye with a small camera called an ophthalmoscope or in more detail with a fundus camera. If there are cranial nerve abnormalities, these may be noticed on eye examination in the form of a squint (third, fourth and sixth) or as facial nerve palsy. If the papilledema has been longstanding, visual fields may be constricted and visual acuity may be decreased. Visual field testing by automated (Humphrey) perimetry is recommended as other methods of testing may be less accurate. Longstanding papilledema leads to optic atrophy, in which the disc looks pale and visual loss tends to be advanced.[1][4]
"Idiopathic" means "of unknown etiology". Therefore, IIH can only be diagnosed if there is no alternative explanation for the symptoms. Intracranial pressure may be increased due to medications such as high-dose vitamin A derivatives (e.g. for acne), long-term tetracycline antibiotics (for a variety of skin conditions) and hormonal contraceptives. There are numerous other diseases, mostly rare conditions, that may lead to intracranial hypertension. If there is an underlying cause, the condition is termed "secondary intracranial hypertension".[1]
Common secondary causes of intracranial hypertension include obstructive sleep apnea (a sleep-related breathing disorder), systemic lupus erythematosis (SLE), chronic kidney disease and Behçet's disease.
