What are the clinical features and examination findings of idiopathic intracranial hypertension (IIH)?

Clinical Features and Examination Findings of Idiopathic Intracranial Hypertension

IIH presents most characteristically with progressively worsening headache and papilledema in an obese woman of childbearing age, though the symptom profile is highly variable and none of the features are pathognomonic for the condition. 1, 2

Patient Demographics

The typical IIH patient profile includes:

• Female sex 2, 3
• Childbearing age 2, 3
• BMI >30 kg/m² 2, 3
• Recent weight gain of 5-15% in the year preceding diagnosis 3

Patients who do not fit this demographic profile are considered "atypical" and require more in-depth investigation to exclude secondary causes. 2

Primary Clinical Symptoms

Headache (Most Common Presenting Symptom)

• Headache is the most frequent symptom, occurring in approximately 90% of patients 1, 4
• The headache is typically progressively more severe and frequent 2, 5
• The phenotype is highly variable and may mimic other primary headache disorders, making clinical diagnosis challenging 1, 2
• This variability is a common diagnostic pitfall that can delay recognition 2

Visual Symptoms

• Transient visual obscurations occur frequently, characterized by unilateral or bilateral darkening of vision typically lasting seconds 1, 2
• Visual blurring is a common complaint 1, 2
• Visual changes were reported in 62% of patients in one large series 4
• Visual field defects may be present on formal testing 6

Auditory Symptoms

• Pulsatile tinnitus (whooshing sound synchronous with pulse) occurs in approximately 48% of patients 1, 2, 4
• This symptom shows excellent response to treatment, with 93% experiencing resolution after venous sinus stenting 4

Other Neurological Symptoms

• Horizontal diplopia (typically from sixth nerve palsy) 1, 2
• Dizziness 1, 2
• Neck pain 1, 2
• Back pain 1, 2
• Cognitive disturbances 1, 2
• Radicular pain 1, 2

Critical caveat: None of these symptoms are pathognomonic for IIH, meaning they can occur in other conditions and should not be used in isolation for diagnosis. 1, 2

Physical Examination Findings

Ophthalmological Examination (Essential)

• Papilledema is the hallmark finding in IIH and must be documented 2, 5
• Papilledema was present in 89% of patients in large case series 4
• IIH without papilledema is a rare subtype that meets all other diagnostic criteria but lacks papilledema, making diagnosis more difficult 2, 5
• Papilledema may be highly asymmetric or even unilateral in atypical presentations 7
• Visual field testing should be performed to document any defects 6

Cranial Nerve Examination

• Typically, there should be no cranial nerve involvement other than possible sixth nerve palsy/palsies 2
• Sixth nerve palsy or divergence insufficiency causing horizontal diplopia is the most common cranial nerve finding 7
• If other cranial nerves or pathological findings are involved, alternative diagnoses should be strongly considered 2

Atypical Cranial Nerve Findings (Red Flags)

When present, these findings should prompt investigation for alternative etiologies:

• Third nerve palsy 7
• Fourth nerve palsy 7
• Internuclear ophthalmoplegia 7
• Diffuse ophthalmoplegia 7
• Skew deviation 7
• Olfactory dysfunction 7
• Trigeminal nerve dysfunction 7
• Facial nerve dysfunction 7
• Hearing loss and vestibular dysfunction 7
• Lower cranial nerve dysfunction (deviated uvula, torticollis, tongue weakness) 7

Blood Pressure Measurement

• Blood pressure must be measured to exclude malignant hypertension as a cause of papilledema 1

Diagnostic Confirmation Requirements

Lumbar Puncture

• CSF opening pressure must be ≥25 cm H₂O (≥250 mm H₂O) measured in the lateral decubitus position to meet modified Dandy criteria 2
• Proper measurement technique is essential: patient in lateral decubitus position, relaxed, with legs extended 2
• All patients in case series had CSF pressure >250 mm H₂O 8
• Pressure may fluctuate, so if initial pressure is borderline, arrange close follow-up with repeat lumbar puncture at 2 weeks 2

Neuroimaging Findings

While not strictly "examination findings," neuroimaging reveals characteristic features:

• Partially empty or empty sella turcica 5, 6
• Flattening of the posterior sclera 5, 6
• Transverse sinus stenosis (bilateral or in dominant sinus) 5, 6
• Increased optic nerve tortuosity 5, 6
• Enlarged optic nerve sheath 5, 6
• Intraocular protrusion of optic nerve head 5, 6
• Prominent perioptic subarachnoid space 6

Common Diagnostic Pitfalls

• The highly variable headache phenotype can mimic primary headache disorders, leading to misdiagnosis and delayed treatment 1, 2
• Asymmetric or unilateral papilledema may be mistaken for other optic nerve pathology 7
• Atypical cranial nerve findings should raise suspicion for alternative diagnoses rather than being attributed to IIH 2, 7
• Failure to measure CSF opening pressure properly (wrong position, patient not relaxed) can lead to inaccurate readings 2
• Single borderline CSF pressure measurements may miss the diagnosis, as pressure fluctuates 2