Idiopathic Intracranial Hypertension
Definition
Idiopathic Intracranial Hypertension (IIH) is a syndrome of raised intracranial pressure (ICP) with:
- Normal brain parenchyma
- Normal CSF composition
- No identifiable structural cause
👉 Formerly called Pseudotumor cerebri
Epidemiology
- Classical patient:
- Young
- Female
- Obese
- Strong associations:
- Rapid weight gain
- Female sex hormones
Etiology & Risk Factors
Primary (Idiopathic)
- No identifiable cause
Secondary causes
Drugs
- Vitamin A excess (retinoids, isotretinoin)
- Tetracyclines
- Growth hormone
- Steroid withdrawal
- Lithium
Endocrine / Metabolic
- Hypothyroidism
- Cushing’s disease
- Addison’s disease
- PCOS
Systemic / Others
- Chronic kidney disease
- Anemia (especially iron deficiency)
- Sleep apnea
Cerebral Venous Outflow Obstruction
- Must exclude:
- Cerebral venous sinus thrombosis (CVST)
👉 Key exam point:
IIH is a diagnosis of exclusion → ALWAYS rule out CVST
Pathophysiology
Not completely understood, but includes:
- Reduced CSF absorption (arachnoid villi dysfunction)
- Increased venous sinus pressure
- Obesity-related increased intra-abdominal → venous pressure
- Hormonal influence (estrogen, leptin)
👉 Leads to:
➡ Raised ICP
➡ Papilledema
➡ Optic nerve dysfunction
Clinical Features
Symptoms
Headache (MOST COMMON)
- Diffuse, daily, worse in morning
- Worse on coughing/straining
Visual symptoms
- Transient visual obscurations (seconds)
- Blurred vision
- Diplopia (6th nerve palsy)
- Progressive visual loss (late)
Others
- Pulsatile tinnitus (whooshing sound)
- Nausea/vomiting
Signs
Papilledema (CARDINAL SIGN)
- Bilateral optic disc swelling
- Hyperemic disc, blurred margins
Cranial nerve palsy
- VI nerve palsy (abducens) → diplopia
Visual field defect
- Enlarged blind spot (EARLY)
- Peripheral constriction (LATE)
Diagnostic Criteria
Modified Dandy Criteria
All must be present:
- Signs/symptoms of raised ICP
- No focal neurological deficit (except VI nerve palsy)
- Normal neuroimaging
- Elevated CSF opening pressure
- Normal CSF composition
Investigations
1. Neuroimaging (FIRST STEP)
MRI Brain + MR Venography (MANDATORY)
Findings (supportive, NOT diagnostic):
- Empty sella
- Flattening of posterior globe
- Optic nerve sheath dilation
- Transverse sinus stenosis
👉 MUST exclude:
- Tumor
- Hydrocephalus
- CVST
2. Lumbar Puncture
- Opening pressure:
- >25 cm H₂O (adults)
- CSF:
- Normal cells
- Normal protein/glucose
👉 LP may transiently relieve symptoms
3. Ophthalmologic Assessment
- Fundoscopy → papilledema
- Visual fields → automated perimetry
Differential Diagnosis
- Cerebral venous sinus thrombosis
- Brain tumor
- Hydrocephalus
- Chronic meningitis
- Malignant hypertension
Management
1. Weight Loss (FIRST-LINE)
- 5–10% weight reduction improves symptoms
- Bariatric surgery if severe obesity
2. Medical Therapy
First-line
- Acetazolamide
- Reduces CSF production
Alternatives
- Topiramate (also causes weight loss)
- Furosemide (adjunct)
3. Serial Lumbar Punctures
- Temporary relief only
- NOT long-term strategy
4. Surgical Management (VISION THREATENED)
Indications:
- Progressive visual loss
- Failure of medical therapy
Options
Optic nerve sheath fenestration
- Protects vision
CSF diversion procedures
- VP shunt / LP shunt
Venous sinus stenting
- If transverse sinus stenosis
Complications
- Permanent visual loss (MOST IMPORTANT)
- Chronic headache
- Diplopia
Prognosis
- Usually benign but:
- Relapses common
- Vision loss in ~5–10%
PEARLS
- Young obese woman + headache + papilledema → IIH until proven otherwise
- ALWAYS do MRV to exclude CVST
- Opening pressure >25 cm H₂O
- Enlarged blind spot = early sign
- First-line drug = acetazolamide
- Weight loss is disease-modifying
- VI nerve palsy = only allowed focal deficit
- Pulsatile tinnitus = classic clue