Idiopathic Intracranial Hypertension (IIH)

WHAT IS IDIDOPATHIC INTRACRANIAL HYPERTENSION?

Idiopathic intracranial hypertension is a condition seen mostly in obese women of child bearing years.  It has gone by many names over the years.  For many years it was called pseudotumor cerebri (meaning that the disorder gave symptoms like a brain tumor, but no tumor was found).  In the 1950s it was known as benign intracranial hypertension, but since it was far from benign for many individuals, other terms were devised like Idiopathic intracranial hypertension.  We speak of pseudotumor cerebri syndrome (which can be primary—or idiopathic intracranial hypertension), or it can be secondary to another cause.

Secondary causes of raised intracranial pressure include venous sinus thrombosis or obstruction, medical disorders like severe anemia, hyperparathyroidism, right heart failure, and certain medications like tetracycline/minocycline type drugs, vitamin A, and others.

The idiopathic form is the most common cause of raised intracranial pressure.  It affects 1/100,00 individuals but 10-20/100,000 obese women—that means that IIH is as common as multiple sclerosis.  While it can occur at any age—and yes children can get it too—about in equal numbers until puberty, when women outnumber men 5-8 to 1.

WHAT ARE THEY SYMPTOMS AND SIGNS OF INTRACRANIAL HYPERTENSION?

Symptoms of IIH include headache as the most frequent, transient visual obscurations or vision darkening, neck and back pain, dizziness, photophobia (light sensitivity), pulsatile tinnitus (whooshing noise in the ears), and diplopia (double vision).

While visual acuity is usually normal in most, the visual field can be abnormal.  The visual field may just show an enlarged blind spot or there may actually be visual field constriction and severe visual loss.  One of the hallmarks on examination is the presence of Papilledema—or an elevated, swollen optic nerve.  This is usually seen by an eye care provider. 

HOW IS IDIOPATHIC INTRACRANIAL HYPERTENSION DIAGNOSED?

In order to diagnose the idiopathic form—and rule out other cause of raised intracranial pressure, imaging, either magnetic resonance imaging (MRI) or computed tomography (CT) of the brain must occur to rule out a brain tumor or venous thrombosis.  In most cases a lumbar puncture is also performed to check the level of the pressure in the head and to be sure that the spinal fluid is normal and not showing infection or other disorder that could increase the intracranial pressure.  An elevated pressure is usually thought to be higher than 250 mm of CSF for adults. 

WHAT CAUSES IDIOPATHIC INTRACRANIAL HYPERTENSION?

The cause is unknown, but there is a genetic contribution suspected.  However, obesity is involved in 90% or more of the cases.  Sleep apnea can be a contributing factor as a result of obesity.

How obesity causes IIH is not entirely known.  Venous hypertension (the venous system drains blood from the brain) is elevated in IIH and some wonder if venous hypertension and venous stenosis contributes to the cause.  Others have suggested that Glymphatics (the lymphatic drainage of the brain and dura) contributes as well. 

HOW IS IDIOPATHIC INTRACRANIAL HYPERTENSION TREATED?

The idiopathic intracranial hypertension treatment trial showed us that weight loss coupled with the use of acetazolamide (also known as diamox) is the best treatment usually in 500 mg twice daily or more.  Even small amounts of weight loss, like 10-20 pounds or 6% of body weight can result in improvement of the condition! 

Vision must be followed carefully with visual acuity, visual field testing.   If visual fields worsen other treatments need to be considered:

  • optic nerve sheath fenestration (that is, surgically making a small whole in the sheath that surrounds the optic nerve in the orbit),
  • lumbar/ventricular peritoneal shunt (that is a tube from the lumbar area or from the ventricle in the brain to the abdomen to drain off fluid)
  • sometimes venous sinus stenting (putting a stent/tube into the venous sinus to lower the pressure. 

Headache treatment can be frustrating since over 40-60% of patients have underlying migraine headache as well and the pressure can worsen migraine.  Even if intracranial pressure is controlled headaches can persist and we have found that headache is the number one driver of the quality of life of individuals with IIH.  We usually treat the migraine portion of the headache with migraine medications like beta blockers, tricyclic antidepressants and even Calcitonin gene related peptide antibodies among others.  We treat the pressure component with acetazolamide or other diuretics like furosemide, neptazane, chlorthalidone. 

WHERE CAN I LEARN MORE?

There are other resources for individuals with IIH.  The Moran Eye Center has an annual IIH update that we post to the MoranCore (see:  https://morancore.utah.edu/idiopathic-intracranial-hypertension-2019/)

The North American Neuro-Ophthalmology Society has patient brochures in many languages hosted on the Neuro-Ophthalmology Virtual Educational Library (see:  https://novel.utah.edu/patient-portal/idiopathic-intracranial-hypertension)