What are the features and treatment options for Idiopathic Intracranial Hypertension (IIH)?

Idiopathic Intracranial Hypertension: Clinical Features

Idiopathic intracranial hypertension (IIH) is characterized by papilledema, elevated intracranial pressure (≥25 cm H₂O on lumbar puncture), and normal neuroimaging, typically affecting obese women of childbearing age with BMI >30 kg/m². 1, 2

Core Clinical Features

Papilledema

• Papilledema is the hallmark finding in IIH and must be documented on fundoscopic examination 2
• Papilledema severity correlates with visual prognosis and guides monitoring frequency 3
• A rare subtype exists—IIH without papilledema—which meets all other diagnostic criteria but lacks this key finding, making diagnosis more challenging 2, 4

Visual Symptoms

• Transient visual obscurations (unilateral or bilateral darkening of vision lasting seconds) occur commonly 1, 2
• Visual blurring is a frequent complaint 1, 2
• Visual field defects develop in many patients and require serial monitoring 1
• Progressive visual loss can occur if untreated, representing the most serious morbidity of IIH 1

Headache Characteristics

• Headache is the most common presenting symptom, occurring in 92% of patients 3
• The headache phenotype is highly variable and may mimic other primary headache disorders (migraine, tension-type), making clinical diagnosis challenging 1, 2
• Headaches are typically progressively more severe and frequent 2
• Importantly, headaches persist in 68% of patients at 6 months and 79% at 2 years after CSF diversion procedures, despite normalization of intracranial pressure 3
• Many patients develop superimposed migrainous headaches on top of ICP-related headaches 3

Cranial Nerve Involvement

• Horizontal diplopia from sixth nerve palsy is the typical cranial nerve finding 1, 2
• Sixth nerve palsy may be unilateral or bilateral 1, 5
• If other cranial nerves are involved beyond the sixth nerve, alternative diagnoses should be strongly considered 2
• Complete ophthalmoplegia is an extremely rare presentation 5

Other Symptoms

• Pulsatile tinnitus (whooshing sound synchronous with pulse) 1, 2, 6
• Dizziness 1, 2
• Neck pain 1, 2
• Back pain 1, 2
• Cognitive disturbances 1, 2
• Radicular pain 1, 2
• Hearing loss and balance disturbance (less common otolaryngologic manifestations) 6
• CSF otorrhea or rhinorrhea (rare) 6

None of these symptoms are pathognomonic for IIH, meaning they can occur in other conditions 1, 2

Diagnostic Criteria and Workup

Neuroimaging Requirements

• Urgent MRI brain within 24 hours is the first step; if unavailable, perform urgent CT brain followed by MRI 2, 7
• Imaging must show no hydrocephalus, mass, structural or vascular lesion, and no abnormal meningeal enhancement 2
• CT or MR venography is mandatory within 24 hours to exclude cerebral sinus thrombosis 2, 7

MRI Findings Supporting IIH

• Posterior globe flattening (56% sensitivity, 100% specificity) 2
• Intraocular protrusion of the optic nerve (40% sensitivity, 100% specificity) 2
• Horizontal tortuosity of the optic nerve (68% sensitivity, 83% specificity) 2
• Enlarged optic nerve sheath (mean 4.3 mm in IIH vs 3.2 mm in controls) 2
• Smaller pituitary gland (mean 3.63 mm in IIH vs 5.05 mm in controls) 2

Lumbar Puncture Criteria

• CSF opening pressure must be ≥25 cm H₂O measured in the lateral decubitus position 2, 7
• Proper technique is essential: patient in lateral decubitus position, legs extended, relaxed, breathing normally, with measurement taken after pressure stabilizes 2
• CSF composition must be normal (elevated pressure alone) 7
• If opening pressure is borderline (20-25 cm H₂O), arrange close follow-up with repeat lumbar puncture at 2 weeks, as pressure may fluctuate 2

Laboratory Findings

• Neurological examination should show no cranial nerve involvement except possible sixth nerve palsy 2, 7
• Laboratory investigations are typically normal 7
• Elevated ESR or other inflammatory markers suggest alternative diagnoses such as giant cell arteritis or vasculitis, not IIH 7

Patient Demographics and Risk Factors

Typical IIH Profile

• Female sex, childbearing age, BMI >30 kg/m² 2, 3
• This represents the most common presentation pattern 3

Atypical Presentations

• Patients not fitting the typical demographic profile require more in-depth investigation 2
• Non-obese prepubertal children warrant particular consideration for cerebral venous sinus thrombosis 2

Associated Conditions

• Obstructive sleep apnea 6
• Tetracycline use (known secondary cause or exacerbating factor) 7
• History of head trauma or meningitis 4

Disease Patterns and Prognosis

Clinical Subtypes

• Fulminant IIH: Rapid visual deterioration requiring urgent intervention 3
• Typical IIH: Most common form with gradual progression 3
• Atypical IIH: Does not fit typical demographic profile 3

Prognostic Factors

• Severe papilledema at presentation is a negative prognostic factor 3
• Weight loss of 5-15% of body weight may lead to disease remission 3
• IIH may recur throughout life, particularly with weight regain or hormonal changes including pregnancy 3

Treatment Response

• Medical therapy (acetazolamide, topiramate) shows treatment failure in 34% at 1 year and 45% at 3 years 3
• Weight management is the only disease-modifying therapy for typical IIH 3

Monitoring and Follow-up

Visual Function Monitoring

• Severe papilledema requires monitoring every 1-3 months 3
• More frequent monitoring is needed if visual function is worsening, with immediate assessment required for worsening with severe papilledema 3
• Repeat lumbar puncture should be performed if significant deterioration of visual function occurs to reassess CSF pressure 2

Urgent Intervention Criteria

• When there is evidence of declining visual function with pathologically high CSF pressure, immediate surgical intervention is required to preserve vision 2
• A temporizing lumbar drain can protect vision while planning urgent surgical treatment 2

Treatment Options

Medical Management

• Acetazolamide is first-line pharmacological therapy 5
• Topiramate as alternative or adjunctive therapy 5
• Diuretics may be used 5
• Weight loss is essential and disease-modifying 3

Surgical Interventions for Refractory Cases

• Venous sinus stenting (VSS) provides the best results: improved papilledema in 87.1%, visual fields in 72.7%, and headaches in 72.1%, with only 2.3% severe complication rate and 11.3% failure rate 8
• CSF diversion techniques (ventriculoperitoneal or lumboperitoneal shunt) improve papilledema in 78.9%, visual fields in 66.8%, and headaches in 69.8%, but have 9.4% severe complication rate and 43.4% failure rate 8
• Optic nerve sheath fenestration (ONSF) ameliorates papilledema in 90.5%, visual fields in 65.2%, and headaches in 49.3%, with 2.2% severe complication rate and 9.4% failure rate 8
• Based on superior outcomes and safety profile, VSS should be regarded as first-line surgical modality for medically refractory IIH 8
• Bariatric surgery may be considered in appropriate candidates 8

Common Pitfalls

• Failing to recognize that headache phenotype can mimic primary headache disorders, delaying diagnosis 1, 2
• Improper lumbar puncture technique (patient not in lateral decubitus position, legs not extended, patient not relaxed) leading to inaccurate opening pressure measurements 2
• Assuming normal intracranial pressure on a single measurement when pressure can fluctuate 2
• Overlooking IIH without papilledema in patients with chronic daily headache, obesity, and symptoms of increased ICP 4
• Failing to perform venography to exclude cerebral sinus thrombosis 2, 7
• Not recognizing that headaches often persist despite successful treatment of elevated ICP 3