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Idiopathic intracranial hypertension

Key Highlights

  • Idiopathic intracranial hypertension (IIH) is a disorder of increased intracranial pressure in an alert and oriented patient. The most popular hypothesis is that IIH is a syndrome of reduced cerebrospinal fluid absorption.
  • Clinical features include headaches, pulse-synchronous tinnitus, transient visual obscurations, visual loss, neck and back pain, and diplopia.
  • Signs include papilledema, sixth nerve paresis, and disturbances in sensory visual function. Visual field loss is ubiquitous, and the prototype pattern for early loss is enlargement of the blind spot and inferonasal loss. Diagnostic criteria are the modified Dandy criteria.
  • In all patients with IIH, treatment consists of eliminating causal factors, such as drugs and other conditions known to cause increased intracranial pressure, and instituting a low-sodium weight-reduction diet plus acetazolamide when indicated. Therapy can be given to reverse and prevent loss of vision.

Quick Reference

  • History & Exam
    • Key Factors
      • visual field loss
    • Other Factors
      • headache
      • transient visual obscurations
      • pulse-synchronous tinnitus
      • photophobia
      • retrobulbar pain
      • optical disk swelling
      • decreased visual acuity
      • ocular motility disturbances
      • relative afferent pupillary defect
    More information…
  • Diagnostics Tests
    • 1st Tests to Order
      • visual field testing (perimetry)
      • dilated fundoscopy
      • visual acuity
      • MRI of brain with or without contrast
      • lumbar puncture at spinal L3/L4
    • Other Tests to consider
      • magnetic resonance venogram of head
      • optical coherence tomography
    More information…
  • Treatment Options
    • acute
      • all patients
        • all patients
        • persistent headache
        • progressive visual loss
        • with diplopia
        • with neck pain
        • persistent pulse synchronous tinnitus
    More information…

Definition

IIH, also known as pseudotumor cerebri, is a disorder of increased intracranial pressure that occurs mainly in overweight women of childbearing years, often in the setting of weight gain.[1] Its cause is unknown. It is characterized by increased intracranial pressure and its associated signs and symptoms in an alert and oriented patient, but without localizing neurologic findings. There is no evidence of deformity or obstruction of the ventricular system, and neurodiagnostic studies are normal except for increased cerebrospinal fluid pressure and the related neuroimaging signs. Furthermore, no secondary cause of intracranial hypertension is apparent. IIH can either be self-limited or have a life-long chronic course.[1] [2]

Vignette

Common Vignette 1

A 29-year-old woman presents with a 3-month history of worsening headaches and increasing visual loss. She describes occasional episodes of bilateral visual grayouts lasting 20 seconds that may be precipitated by bending forward or standing. Over the last 2 weeks she has often heard a “whooshing” sound in both ears, synchronous with her pulse, that is more noticeable when she is about to go to sleep. Her visual acuity is 20/30 (6/9 meters) in each eye. Fundus examination shows bilateral optic disk swelling, and Humphrey automated perimetry shows enlargement of the blind spot and scattered abnormal test locations. Magnetic resonance imaging shows a partially empty sella, and a magnetic resonance venogram shows no evidence of a thrombosis but does demonstrate bilateral transverse sinus venous stenoses. Lumbar puncture opening pressure is 280 mm H2O. Images

Common Vignette 2

A 42-year-old man presents with a 2-month history of increasing migraine headaches that are worse in the morning and associated with nausea. He has occasional episodes of transient visual loss in both eyes that last 30 seconds before recovering. He has been overweight for many years and admits to gaining weight over the last couple of years. His body mass index at the time of presentation is 34.

Other Presentations

Other common presentations include severe headaches and visual loss in young women. Usually the course is chronic.

Epidemiology

IIH occurs worldwide. In the US, annual national incidence is estimated at 1.15 per 100,000.[3] IIH is most prevalent among obese women of childbearing age; the highest incidence in England is among females age 25 years (15.2 per 100,000).[4] One study of IIH in Libya found an average incidence rate of 2.2 per 100,000 persons; among obese females ages 15 to 44 years, the rate rose to 21.4 per 100,000.[5] In the US there is a higher incidence among black people (2.05 per 100,000) followed by white people (1.04 per 100,000), Hispanics (0.67 per 100,00), and Asian/Pacific Islanders (0.16 per 100,000).[3] The mean age at diagnosis is about 30 years.[6]

The incidence of IIH has increased in recent years.[3] In England, the incidence of IIH rose between 2002 and 2016 from 2.3 to 4.7 per 100,000 persons.[4] Increasing prevalence and incidence of IIH mirrors population increases in obesity and has been associated with social deprivation.[4] [7] Younger children with IIH are less likely to be obese than teenagers or adults.[8] Incidence is the same in pregnant and nonpregnant women.[9]

Etiology

The cause is unknown. IIH in adults is highly associated with female sex and obesity (often associated with recent weight gain).[6] [10] Many etiologies have been suggested, but none proven.

Pathophysiology

Cerebrospinal fluid (CSF) absorption occurs both via the arachnoid granulations and along nerve root sheaths, especially along the olfactory nerve through the cribriform plate.[11] It is thought that there is increased resistance to CSF outflow along one or both of these pathways, but abnormalities of these absorption pathways in patients with IIH remain unproven. With CSF absorption block, intracranial pressure must rise for CSF to be absorbed. Although interstitial and intracellular edema have been reported in brain biopsy specimens, study with current methods of analysis has concluded that the histologic features of the brain parenchyma are normal, and the findings of previous studies are artifacts of slide preparation.[12] [13] In addition, changes in cerebral hemodynamics, including increased cerebral blood volume and decreased cerebral blood flow, have been reported, but their significance is unclear.

The relationship between papilledema and loss of vision is complex and usually due to intraneuronal ischemia related to increased CSF pressure transmitted along the optic nerve sheath.[14] With the loss of axons, papilledema can regress while vision worsens. More often, however, the more severe the papilledema, the worse the loss of vision. This is true for large case series, but occasionally patients have marked papilledema and little loss of vision.[15]

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