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

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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)

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Table 2: Association of IIH with drugs

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Table 3: Differential diagnosis of IIH

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(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

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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.
  • Lin A., Foroozan R., Danesh-Meyer H., V., et al. Occurrence of cerebral venous sinus thrombosis in patients with presumed idiopathic intracranial hypertension. Ophthalmology 2006; 113:2281.
  • Mokri B: The Monro-Kellie hypothesis: Applications in CSF volume depletion. Neurology 56:1746–1748, 2001.
  • Quincke H: Über Meningitis serosa und verwandte Zustande. Deutsche Z Nervenheilk 25:85–88, 1897.
  • Dandy WE: Intracranial pressure without brain tumor: Diagnosis and treatment. Ann Surg 106:492–513, 1937.
  • 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.
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