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Idiopathic Intracranial Hypertension (Pseudotumor Cerebri)

URGENT — Neuro

Symptoms

daily headache (often worst on waking or with valsalva)

transient visual obscurations (seconds of graying-out with posture changes)

pulsatile tinnitus (unilateral/bilateral "whooshing" sound)

horizontal binocular diplopia (from cn vi palsy)

nausea or vomiting accompanying headaches

typically occurs in obese women of reproductive age (bmi >30)

Clinical Findings

Papilledema (bilateral optic disc edema)

  • blurred disc margins and obscuration of vessels crossing the disc
  • peripapillary flame hemorrhages and cotton-wool spots
  • paton lines: retinal or choroidal folds
  • frisén scale (grade 0–5) used for clinical staging

Visual field defects

  • earliest sign: enlarged blind spot
  • inferonasal step or arcuate defects
  • progressive peripheral constriction; generalized depression in advanced disease
  • acuity and color vision loss are late, severe findings

MRI/MRV features

  • empty sella and posterior flattening of the globes
  • distended perioptic subarachnoid space and optic nerve tortuosity
  • transverse venous sinus stenosis

Neurologic status

  • normal neuro exam except for possible unilateral or bilateral cn vi palsy
  • any other focal deficit excludes iih and mandates re-imaging

Etiology

Mechanism

  • increased csf pressure without mass, hydrocephalus, or venous thrombosis
  • likely impaired csf absorption at arachnoid granulations

Triggers & associations

  • strong link to obesity and rapid weight gain
  • medication-induced: tetracyclines (doxycycline/minocycline), vitamin a/retinoids, corticosteroid withdrawal, and lithium

Red Flags

progressive vision loss despite maximal medical therapy

fulminant iih: rapid, aggressive vision decline over days

atypical demographic (male, non-obese, or elderly) suggesting secondary cause

bilateral cn vi palsy with altered consciousness

Investigations

Mandatory imaging

  • mri brain + mrv with contrast: rules out mass, hydrocephalus, and venous sinus thrombosis

Lumbar puncture (post-imaging)

  • opening pressure >25 cm h2o (lateral decubitus, legs extended)
  • normal csf composition (cytology/chemistry)

Ocular monitoring

  • automated perimetry (humphrey 24-2): most sensitive for progression
  • oct rnfl to quantify edema and monitor for atrophy
  • fundus photography for serial disc documentation

Treatment

Medical management

  • weight loss: first-line and potentially curative
  • acetazolamide (titrated up to 4g/day): reduces csf production (iihtt protocol)
  • topiramate: second-line; useful for concurrent weight loss and headache

Surgical (medical failure or threatened vision)

  • optic nerve sheath fenestration (onsf): protects the nerve directly
  • csf diversion (vp or lp shunt): for intractable headache or vision loss
  • venous sinus stenting: if significant pressure gradient across stenosis exists

Pregnancy

  • acetazolamide generally used after 20 weeks; vaginal delivery usually safe

Clinical Pearl

In IIH, the field defect drives treatment, not the headache — losing nerve fibers is irreversible, so escalate (ONSF or shunt) when the field worsens even if the patient feels better.

Differential Diagnosis

  • intracranial mass or tumor
  • cerebral venous sinus thrombosis
  • meningitis (infectious or neoplastic)
  • malignant hypertension
  • optic neuritis

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