Idiopathic Intracranial Hypertension

Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, is a clinical disorder that presents with symptoms due to increased intracranial pressure (ICP; ≥ 20 mm Hg) or CSF pressure (> 250 mm H2O), with no structural changes or other attributable causes. The condition is most commonly observed in obese women and after intake of certain drugs, such as growth hormones, tetracycline antibiotics, and high dosages of vitamin A. Classic manifestations include headache, vision loss or visual-field defects, and papilledema. Diagnosis is made by clinical exam, imaging, and lumbar puncture. Management is aimed at decreasing ICP and includes medication, therapeutic CSF removal, and shunting.

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Overview

Definition

Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, is a clinical disorder that presents with symptoms due to increased intracranial pressure (ICP; ≥ 20 mm Hg) or CSF pressure (> 250 mm H2O), with no structural changes or other attributable cause. 

Epidemiology

  • Highest incidence in middle-aged, obese women
  • 20× more frequent in women than in men
  • Annual incidence: 
    • Approximately 19 per 100,000 in women 15–44 years of age ≥ 20% of their ideal body weight
    • Approximately 3.5 per 100,000 in all women 15 to 44 years of age
    • Approximately 1 per 100,000 in women and men of all ages

Etiology

  • Decreased resorption of CSF
  • Increased production of CSF
  • Risk factors:
    • Obesity (in 94% of individuals with IIH)
    • Hypertension
    • Hypervitaminosis A from excessive intake
    • Possible links to medications:
      • Treatment with human growth hormone (HGH)
      • Minocycline and doxycycline
      • Retinoids
    • Possible links to systemic illnesses:
      • Addison disease
      • Hypoparathyroidism
      • Severe anemia
      • Hypercoagulable syndromes
      • Systemic lupus erythematosus (SLE)

Pathophysiology

The exact pathogenesis of IIH is unknown, although there are several proposed mechanisms. Cerebral edema has not been found in IIH, as hypothesized in the past.

  • Cerebral venous outflow abnormalities → increased ICP
  • Obesity → aldosterone excess → ↑ CSF production by the choroid plexus
  • Obesity → ↑ intraabdominal pressure, pleural pressure, cardiac filling pressure, and central venous pressure → ↑ intracranial venous pressure and IIH

Clinical Presentation

Idiopathic intracranial hypertension should be considered in the differential diagnosis for any individual who presents with headaches and papilledema.

History

  • Most common symptoms of high-pressure headache:
    • Location: frontal
    • Timing: headache on early-morning awakening
    • Initiated by coughing, sneezing, or Valsalva maneuver
  • Associated visual symptoms:
    • Blurred vision
    • Diplopia (if abducens nerve palsy)
    • Peripheral visual field loss
  • Other associated symptoms:
    • Pulsatile tinnitus
    • Nausea and vomiting

Physical examination

  • Funduscopic exam: 
    • Bilateral papilledema
    • Macular exudates and edema
    • Retinal and choroidal folds across the macula
  • Visual-field loss:
    • Gradual but abrupt
    • Can be in nasal or temporal field 
  • Abducens (cranial nerve (CN) VI) nerve palsy: can be unilateral or bilateral
  • Other rare CN deficits:
    • Facial nerve (CN V)
    • Olfactory nerve (CN I)
    • Oculomotor nerve (CN III)
  • Usually no cognitive impairment
Papilledema

Papilledema:
Optic disc swelling as seen with increased ICP

Image: “Papilledema” by Jonathan Trobe, M.D. License: CC BY 3.0

Diagnosis

The diagnosis of IIH is clinical; urgent neuroimaging is required to rule out other causes of increased ICP. 

  • Possible MRI findings:
    • Transverse sinus stenosis
    • Distention of the perioptic subarachnoid space
    • Empty sella
    • Vertical tortuosity of the orbital optic nerve
    • No abnormalities of brain parenchyma
  •  Lumbar puncture (LP) if imaging does not reveal a structural cause:
    • Elevated opening pressure confirms the diagnosis:
      • ≥ 250 mm H2O in adults
      • ≥ 280 mm H2O in children 
    • Send CSF for studies to exclude other conditions.
    • Procedure is also therapeutic.
  • Ophthalmologic evaluation:
    • Document severity of optic nerve involvement
    • Monitor response to treatment
  • Modified Dandy criteria for diagnosis of IIH:
    • Symptoms and signs of increased ICP
    • No other neurologic abnormalities
    • Imaging (MRI or CT) shows no other etiology of increased ICP.
    • Lumbar puncture shows elevated ICP with normal CSF studies.
  • Labs:
    • CBC to exclude anemia
    • CMP
    • CSF analysis 
    • ANA
Narrowing of the transverse sinuses

Narrowing of the transverse sinuses:
MRV (magnetic resonance venography) showing narrowing of the transverse venous sinuses, most likely related to idiopathic intracranial hypertension.

Image: “MRV showing narrowing of the transverse venous sinuses” by Shaw GY, Million SK. License: CC BY 3.0

Management

Increased ICP is a medical emergency. Definitive management depends on the underlying etiology.

Treatment

  • Goals:
    • Improvement of headache 
    • Preservation of vision
  • Medical treatment:
    • Discontinue any medications that may cause or worsen IIH.
    • Recommend weight loss if overweight.
    • Evaluate for sleep apnea if indicated.
    • Low-sodium diet
    • Medications:
      • Diuretics: acetazolamide (carbonic anhydrase inhibitor) or furosemide (loop diuretic); can be tapered off after improvement and stabilization
      • Topiramate: antiseizure medication that inhibits carbonic anhydrase and also helps headaches
      • Glucocorticoids if acute visual loss present
    • Serial lumbar punctures for CSF drainage:
      • Decreases ICP
      • Relieves symptoms
      • Can be a useful temporizing measure until surgery
  • Surgical indications:
    • Resistance to or intolerance of the options above
    • Deteriorating vision or visual-field defects
    • Presence of visual acuity loss due to papilledema
  • Surgical procedures:
    • Optic nerve sheath fenestration:
      • Indicated for individuals with a less severe/shorter duration of visual abnormality
      • Stabilizes visual acuity
      • Improves visual field loss
      • May or may not improve headache
    • CSF shunting:
      • Ventriculoperitoneal shunt or lumboperitoneal shunt
      • Can relieve headache and visual symptoms
      • Relief may last only a couple of years.
      • Complications: shunt failure, infection, low pressure from overdrainage
  • Monitoring: ophthalmologic follow-up for several years

Prognosis

  • Improved outcomes with control of ICP (symptoms slowly worsen if untreated)
  • Risk factors for permanent vision loss (6%–14%):
    • Higher-grade papilledema at time of diagnosis
    • Visual symptoms at time of diagnosis
    • Male sex
    • Systemic hypertension
    • More severe obesity or recent weight gain
    • Noncompliance with medication
  • Recurrence:
    • Seen in 8%–38% of individuals after recovery from an episode of IIH
    • Weight gain is a common cause of recurrence, but not in all individuals.
    • May be several years after recovery

Differential Diagnosis

  • Migraine: primary headache disorder characterized by episodic, moderate to severe headaches associated with photophobia, phonophobia, and nausea and/or vomiting and possibly preceded by an aura. The characteristic headache seen in migraines can be distinguished from that with increased ICP because of ICP’s lack of aura and presence of papilledema. Diagnosis is made clinically and with further testing as needed. Management includes NSAIDs and triptans.
  • Obstructive hydrocephalus: pathologic accumulation of CSF within the ventricles of the brain due to a structural blockage. The clinical presentation is often nonspecific, with headaches, behavioral changes, developmental delays, or nausea and vomiting. If the hydrocephalus is congenital or acquired at a young age, infants often present with macrocephaly. Diagnosis is confirmed with neuroimaging showing ventriculomegaly. Treatment is by the placement of a CSF shunt.
  • Venous sinus thrombosis: thrombosis of the cerebral veins and dural sinuses most commonly presenting with headaches and elevated ICP. Venous sinus thrombosis may also be associated with focal neurologic deficits, seizures, or altered mental status. Diagnosis is made by brain MRI and MR venography. Treatment is with anticoagulation and measures to control increased ICP.
  • Intracranial mass: Tumors within the cranial vault increase the parenchymal content and increase intracranial pressure. Clinical presentation includes progressively worsening headaches and neurologic deficits. Diagnosis is made by neuroimaging of the brain. Management is with steroids to decrease ICP and by treating the specific cause.
  • Rare causes of decreased CSF absorption (arachnoid granulation adhesions after meningitis; subarachnoid hemorrhage) or increased CSF production (e.g., choroid plexus papilloma): These rare causes may also present with headaches and are diagnosed with imaging and lumbar puncture.

References

  1. Mondragon, J., Klovenski, V. (2021). Pseudotumor cerebri. StatPearls. Retrieved September 2, 2021, from http://www.ncbi.nlm.nih.gov/books/NBK536924/ 
  2. Lee, A.G., Wall, M. (2021). Idiopathic intracranial hypertension (pseudotumor cerebri): clinical features and diagnosis. Retrieved August 12, 2021, from https://www.uptodate.com/contents/idiopathic-intracranial-hypertension-pseudotumor-cerebri-clinical-features-and-diagnosis
  3. Smith, E.R., Amin-Hanjani, S. (2019). Evaluation and management of elevated intracranial pressure in adults. Retrieved August 12, 2021, from https://www.uptodate.com/contents/evaluation-and-management-of-elevated-intracranial-pressure-in-adults
  4. Lee, A.G., Wall, M. (2021). Idiopathic intracranial hypertension: prognosis and treatment. Retrieved September 2, 2021, from https://www.uptodate.com/contents/idiopathic-intracranial-hypertension-pseudotumor-cerebri-prognosis-and-treatment
  5. Hoffman, K.R., Chan, S.W., Hughes, A.R., Halcrow, S.J. (2015). Management of cerebellar tonsillar herniation following lumbar puncture in idiopathic intracranial hypertension. Case Reports in Critical Care 2015:895035. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4313522/

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