What is the full workup for idiopathic intracranial hypertension (IIH)?

Full Workup for Idiopathic Intracranial Hypertension

The complete workup for IIH requires urgent neuroimaging (MRI brain within 24 hours), mandatory venography to exclude cerebral sinus thrombosis, blood pressure measurement, comprehensive neuro-ophthalmological examination documenting papilledema, and lumbar puncture with opening pressure measurement after normal imaging is confirmed. 1

Initial Clinical Assessment

Blood Pressure Measurement

• Measure blood pressure immediately to exclude malignant hypertension (diastolic BP >120 mmHg), which can mimic IIH 1

Neurological Examination

• Document cranial nerve examination systematically 1
• In typical IIH, there should be no cranial nerve involvement except sixth nerve palsy/palsies (causing horizontal diplopia) 1, 2
• If other cranial nerves are involved or other pathological findings are present, strongly consider alternative diagnoses 1
• This is a critical pitfall—atypical cranial nerve findings should prompt more extensive investigation 1

Neuro-Ophthalmological Examination

• Document presence and severity of papilledema, which is the hallmark finding 2, 3
• Perform formal visual field testing and visual acuity assessment 1
• If diagnostic uncertainty exists regarding papilledema versus pseudopapilledema, consult an experienced clinician early before proceeding with invasive tests 1

Neuroimaging Protocol

Primary Imaging

• Urgent MRI brain within 24 hours is mandatory 1, 2
• If MRI is unavailable within 24 hours, perform urgent CT brain followed by subsequent MRI when available 1, 2
• MRI is preferred as it better excludes secondary causes of raised intracranial pressure 2

Required Imaging Findings

• Must show no evidence of hydrocephalus, mass lesion, structural or vascular lesion, and no abnormal meningeal enhancement 1, 2

Mandatory Venography

• CT or MR venography is mandatory within 24 hours to exclude cerebral sinus thrombosis 1, 2, 3
• This is non-negotiable as cerebral venous thrombosis can present identically to IIH 1

Supportive Neuroimaging Features

While not pathognomonic, the following findings support IIH diagnosis 3, 4:

• Empty or partially empty sella turcica 3
• Increased optic nerve tortuosity 3
• Enlarged optic nerve sheath with distension of perioptic nerve sheath 3, 4
• Flattening of the posterior globe/sclera 3, 4
• Intraocular protrusion of optic nerve head 3
• Transverse sinus stenosis 3, 4

Recent evidence suggests that ≥3 neuroimaging signs have 59.5% sensitivity and 93.5% specificity for IIH, with moderate suprasellar herniation, perioptic nerve sheath distension, globe flattening, and transverse sinus stenosis being most strongly associated 4

Lumbar Puncture

Timing and Indication

• Following normal imaging, all patients with papilledema must have a lumbar puncture 1
• This checks opening pressure and ensures CSF contents are normal 1

Opening Pressure

• Document the lumbar puncture opening pressure carefully 1
• Elevated opening pressure (≥25 cm CSF) is required for diagnosis 4

CSF Analysis

• CSF composition must be normal (no evidence of infection, malignancy, or inflammation) 1

Patient Stratification

Typical IIH

• Female, childbearing age, BMI ≥30 kg/m² 1, 2, 5
• These patients require standard workup as outlined above 1

Atypical IIH

• Not female, not of childbearing age, or BMI <30 kg/m² 1, 2
• These patients require more in-depth investigation to ensure no other underlying causes 1
• Consider broader differential diagnosis and additional testing as clinically indicated 6

Common Pitfalls to Avoid

• Do not skip venography—cerebral sinus thrombosis is a critical mimic that requires different treatment 1
• Do not perform lumbar puncture before imaging—this could be dangerous if a mass lesion is present 1
• Do not dismiss atypical presentations—unusual cranial nerve findings, absence of papilledema in one case, or atypical demographics warrant expanded investigation 1, 6
• Recognize that headache phenotype is highly variable and may mimic other primary headache disorders, making clinical diagnosis challenging 1, 2
• IIH without papilledema exists but is rare and more difficult to diagnose 2, 3