What is the diagnostic approach to Idiopathic Intracranial Hypertension (IIH)?

Diagnostic Approach to Idiopathic Intracranial Hypertension (IIH)

The diagnosis of IIH requires fulfillment of the modified Dandy criteria, which includes an opening CSF pressure of at least 25 cm H₂O, normal neuroimaging, normal CSF composition, and normal neurological examination except for possible papilledema and sixth nerve palsy. 1

Diagnostic Criteria

The diagnostic approach to IIH follows these key steps:

1. Clinical Presentation Assessment:

   • Most common in females of reproductive age with BMI >30 kg/m² 1
   • Common symptoms include:
     • Headache (92% of patients) 2
     • Transient visual obscurations (72%) 2
     • Intracranial noises/pulsatile tinnitus (60%) 2
     • Visual loss complaints (26% initially) 2

2. Neurological Examination:

   • Look specifically for:
     • Papilledema (cardinal sign)
     • Sixth nerve palsy (possible)
     • Otherwise normal neurological exam
   • Note: Other cranial nerve involvement suggests alternative diagnosis 1

3. Neuroimaging:

   • Urgent MRI brain within 24 hours (or CT if MRI unavailable) 1
   • CT or MR venography to exclude cerebral sinus thrombosis 1
   • Look for neuroimaging signs suggestive of IIH:
     • Moderate suprasellar herniation (71.4% of IIH patients) 3
     • Perioptic nerve sheath distension (69.8%) 3
     • Flattening of the globe (67.1%) 3
     • Transverse sinus stenosis (60.2%) 3
   • The presence of ≥3 neuroimaging signs has 59.5% sensitivity and 93.5% specificity for IIH 3

4. Lumbar Puncture:

   • Essential for diagnosis
   • Opening pressure must be ≥25 cm H₂O 1
   • CSF composition must be normal (normal glucose, protein, cell count) 1

5. Ophthalmological Assessment:

   • Visual acuity testing
   • Visual field assessment (abnormal in 96% with Goldmann perimetry) 2
   • Contrast sensitivity testing (abnormal in 50%) 2
   • Fundus examination for papilledema

Diagnostic Algorithm

1. Initial Screening:

   • If patient presents with headache, visual disturbances, or pulsatile tinnitus, especially if female and obese, consider IIH
   • Perform funduscopic examination to check for papilledema

2. If Papilledema Present:

   • Proceed with urgent neuroimaging (MRI brain + MR venography)
   • If neuroimaging normal (no mass, hydrocephalus, or venous thrombosis), proceed to lumbar puncture
   • If opening pressure ≥25 cm H₂O and normal CSF composition, diagnosis of IIH is confirmed

3. If No Papilledema but High Clinical Suspicion:

   • Consider IIH without papilledema if ≥3 neuroimaging signs are present 3
   • Lumbar puncture still required to confirm elevated opening pressure

Important Considerations and Pitfalls

• Beware of asymptomatic cases: 24.7% of patients may be asymptomatic and discovered only during routine ophthalmic examination 4

• Secondary causes: Always exclude secondary causes of intracranial hypertension, especially in non-obese patients 1

• Diagnostic pitfall: Relying solely on symptoms can lead to missed diagnosis, as visual field defects are present in 92-96% of patients but only 26% complain of visual loss initially 2

• Recent diagnostic proposal: Recent evidence suggests IIH can be defined by two out of three objective findings: papilledema, opening pressure ≥25 cm CSF, and ≥3 neuroimaging signs 3

• Monitoring implications: Since visual loss is common (96% by perimetry) but potentially reversible (60% improve with treatment), thorough baseline visual assessment is crucial 2

• Cerebral perfusion: Consider perfusion changes as cerebrovascular complications may be associated with IIH 5