Idiopathic Intracranial Hypertension

Umair Hamid 1, Junaid Siddiqui, MD, MRCP 2

1 University of Health and Sciences, PK

2 University of Missouri Columbia, School of Medicine

Introduction

  • Idiopathic intracranial hypertension (IIH) is also referred to as pseudotumor cerebri.
  • Syndrome of intracranial hypertension without structural brain or CSF abnormalities and without identifiable cause, now most appropriately termed IIH, was first described over 100 years ago.
  • Elevated intracranial pressure with unknown pathogenesis.
  • Typical patients are obese women between the ages of 15 and 44 years.
  • Atypical patients include men, slim women, prepubescent children and patients older than 44 years.
  • Annual Incidence for young overweight women is as high as 20 per 100,000 persons
  • Permanent vision loss is the major morbidity associated with IIH.

Pathogenesis

Increased production of CSF

    • Monro-Kellie rule: Anything added to the blood, CSF brain volume or anything impeding CSF or venous egress would be expected to increase ICP.
    • Quincke suggested hypersecretion of CSF accounted for the syndrome, except for rare cases of choroid plexus papilloma.

Increase in cerebral blood volume or brain water content

    • Dandy hypothesized cerebral blood or CSF volume might be increased.
    • Sahs and Joynt provided histological evidence of edema in brain biopsy specimens obtained at the time of subtemporal decompression for treatment of IIH.

Obstruction of CSF or venous outflow

    • Many studies have suggested underlying mechanism involving disturbed CSF absorption secondary to increased sagittal sinus pressure.
    • Owler et al. identified patients with venous sinus obstruction that was treatable with endoluminal stenting.

Clinical Presentation

  • IIH commonly runs a protracted course, signs and symptoms wax and wane usually for several weeks, months and even years.
  • A subset of patients present with fulminant IIH
    • Acute onset of symptoms and signs of intracranial hypertension (less than 4 weeks between onset of initial symptoms and severe visual loss)
    • Rapid worsening of visual loss over a few days
    • Normal brain MRI and MR venography (or CT venogram)
  • Signs and Symptoms
    • Headache
      • Most common
      • 92%-94% incidence
      • Typically generalized, episodic, throbbing and worse in the morning
      • Often aggravated by Valsalva maneuvers
      • Maybe associated with retro-orbital pain
    • Visual symptoms
      • 30%-68% incidence
      • Visual field defects
        • Scotomas
        • Loss of inferonasal portions of the visual field along with constriction of isopters
      • Visual obscurations
      • Blurring
      • Scotomas
      • Diplopia; 20%-38% incidence.
    • Pulsatile tinnitus
      • 64%-87% incidence as recorded in two small series
      • May be seen as initial symptom
      • Cause is thought to be turbulence resulting from higher-to-lower venous pressures around the jugular bulb which can be auscultated in some patients.
    • Neck, shoulder and/or arm pain
      • 44%-48% incidence.
      • Neck pain may be associated with electric shock-like sensations similar to Lhermitte’s sign.
    • Sixth cranial nerve palsy
      • 20% incidence.
      • False localizing sign.
      • Thought to be attributable to traction of the VIth cranial nerve resulting from intracranial hypertension.
    • Incoordination; 14% incidence
    • Decreased smell; 10% incidence
  • Ophthalmoscopic findings
      • Ophthalmoscopic examination is critical in suspected IIH.
      • Characterized by bilateral optic nerve head swelling.
      • Papilledema may be asymmetric or unilateral.
      • Papilledema is virtually seen in all cases of IIH.

Diagnostic criteria

  • Modified Dandy criteria
    • It is the most appropriate criteria for the diagnosis of IHH
      • Signs and symptoms of increased intracranial pressure.
      • No localizing findings on neurological examination (except for false localizing signs such as abducens or facial palsy).
      • Normal CT/MRI findings without evidence of dural sinus thrombosis.
      • Awake and alert.
      • No other cause of increased ICP found.
      • ICP of 250 mm water or 18 mm Hg with normal cerebrospinal fluid cytological and chemical findings.

For CSF opening pressures of 200 to 250 mm water (14-18 mm Hg) additional requirement of at least one of the following:

  • Pulse synchronous tinnitus.
  • Cranial nerve VI palsy.
  • Frisen Grade II papilledema.
  • Echography for drusen negative and no other disc anomalies mimicking disc edema present.
  • MRV (Magnetic Resonance Venography) with lateral sinus collapse/stenosis preferably using ATECO technique.
  • Partially empty sella on coronal or sagittal views and optic nerve sheaths with filled out CSF spaces next to the globe on T2 weighted axial scans.

Figure 1: Diagnostic algorithm

Evaluation

  • Detailed history and examination.
  • Distinguish suspecting IIH from other causes of increased intracranial pressure and other etiologies of papilledema.
  • Neuroimaging
  • Magnetic resonance imaging (MRI) with postcontrast MR venography (MRV) is preferred. Adding contrast increases the sensitivity of test to detect cerebral venous thrombosis.
  • To exclude secondary causes of raised ICP.
  • Lumbar puncture
  • To measure opening pressure and CSF analysis.
  • Opening pressure of >200mmH2O (14 mm Hg) is considered abnormally elevated.
  • CSF is analyzed for cell count and differential, protein and glucose.
  • Cerebrospinal fluid composition (protein, cells, glucose) is normal in patients with IIH.
  • Complete ophthalmic exam

It should include:

  • Visual field examination
    • To assess the severity of optic nerve involvement and monitor response to treatment.
    • Goldmann kinetic perimetry and the computer-assisted static perimetry can be used to assess visual field.
  • Dilated fundus examination.
  • Optic nerve photographs.

Table 1: Risk factors of IIH (All of these risk factors are not associated with IIH in prepubertal age group)

Table 2: Association of IIH with drugs

Table 3: Differential diagnosis of IIH

(Derived from Wall, M. (2010). Idiopathic intracranial hypertension. Neurologic clinics, 28(3), 593-617.)

Treatment

Medical therapy

  • Counsel obese patients to enroll in supervised weight loss programs.
  • The goal of treatment is to alleviate the symptoms and to preserve vision.
  • Acetazolamide is used as the initial treatment as it is believed to reduce the rate of CSF production
  • Starting dose in adult patients is 500 mg twice per day. The dose can be further increased upto 2 to 4 g/day as required and tolerated by the patient.
  • It has not yet been proven to improve long term prognosis but studies have shown its role in managing the symptoms and improving the visual field.
  • Monitoring of electrolytes is suggested during acetazolamide treatment.
  • Acetazolamide is considered to be relatively contraindicated in the first 20 weeks of pregnancy.
  • Should be used with caution in patients with sulfa allergy.
  • Topiramate and other carbonic anhydrase inhibitors are alternatives to acetazolamide.
  • Furosemide or other diuretics may provide an additional benefit in patients who experience continuing symptoms on acetazolamide.
  • Dosage: 20 to 40 mg per day for adults
  • Should be used with caution in patients with sulfa allergy.
  • Short-term use of corticosteroids and serial lumbar punctures can be used as short term temporary measures in patients with rapidly progressive symptoms who are waiting for more definitive surgical therapy.
  • Prolonged corticosteroid treatment and serial lumbar punctures is usually not recommended due to their potential side effects.
  • Drugs that might cause or worsen IIH should be discontinued.
  • Regular followup visits with serial ophthalmic examinations.
  • Gradual improvement and stabilization is seen with treatment but not necessarily complete recovery; many patients have persistent papilledema, elevated ICP and residual visual field deficits.

Surgical Therapy

  • Indications
  • Worsening visual field defect despite medical therapy.
  • Presence of visual acuity loss due to papilledema.
  • Intractable headache.
  • Anticipated hypotension (blood pressure treatment, renal dialysis).
  • Patients unable to follow-up.
  • Optic nerve sheath fenestration
  • Primary goal is to preserve vision
  • Improves vision loss due to papilledema
  • Shunting:
  • Ventriculoperitoneal or lumboperitoneal shunt are the common shunting procedures.
  • It can alleviate headache, diplopia, papilledema and visual loss.
  • Most common complication is shunt failure often requiring multiple revisions.
  • Other complications include shunt infection, shunt malfunction, CSF leak with low pressure and abdominal pain
  • Venous sinus stenting:
  • A new minimally invasive procedure.
  • Many patients with IIH have stenosis of the transverse venous sinus or other cerebral veins.
  • Studies have shown a decrease in opening pressure in patient with IIH after the procedure

Figure 2: Treatment algorithm

Prognosis

  • IIH persists in many patients
    • In a case series, 83% of patients in long-term follow-up who underwent repeated LP’s showed elevated ICP’s ranging from 16 to 50 mm Hg.
  • Recurrent symptoms and papilledema have been reported in 8% to 37% of patients often years after the initial diagnosis ,.

Further Reading

  • Wall, M. (2010). Idiopathic intracranial hypertension. Neurologic clinics, 28(3), 593-617.
  • Binder, D. K., Horton, J. C., Lawton, M. T., & McDermott, M. W. (2004). Idiopathic intracranial hypertension. Neurosurgery, 54(3), 538-552.

Bibliography

  • Friedman, D. I., & Jacobson, D. M. (2004). Idiopathic intracranial hypertension. Journal of Neuro-ophthalmology, 24(2), 138-145.
  • Binder, D. K., Horton, J. C., Lawton, M. T., & McDermott, M. W. (2004). Idiopathic intracranial hypertension. Neurosurgery, 54(3), 538-552.
  • Ball, A. K., & Clarke, C. E. (2006). Idiopathic intracranial hypertension. The Lancet Neurology, 5(5), 433-442.
  • Wall, M. (2010). Idiopathic intracranial hypertension. Neurologic clinics, 28(3), 593-617.
  • Corbett, J. J., Savino, P. J., Thompson, H. S., Kansu, T., Schatz, N. J., Orr, L. S., & Hopson, D. (1982). Visual loss in pseudotumor cerebri: follow-up of 57 patients from five to 41 years and a profile of 14 patients with permanent severe visual loss. Archives of neurology, 39(8), 461-474.
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  • Sahs AL, Joynt RJ: Brain swelling of unknown cause. Neurology 6:791– 803, 1956.
  • Owler BK, Parker G, Halmagyi GM, Dunne VG, Grinnell V, McDowell D, Besser M: Pseudotumor cerebri syndrome: Venous sinus obstruction and its treatment with stent placement. J Neurosurg 98:1045–1055, 2003.