19th June 2023

Idiopathic Intracranial Hypertension

Diagnosis

• Idiopathic intracranial hypertension (IIH) is a rare condition resulting in increased intracranial pressure without underlying cause, such as hydrocephalus or a mass lesion. CSF composition is also normal. It is also termed Benign Intracranial Hypertension. It mostly affects young women and has a strong association with obesity.
• Clinical features include:
  • Headache with increasing severity and frequency. Headache typically worse on waking and on performing manoeuvres which increase intracranial pressure (ICP), such as bending over.
  • Visual disturbance or loss, horizontal diplopia due to abducens nerve (CNVI) palsy, reduced peripheral vision, blurred vision with loss of acuity and colour sensitivity, momentary darkening of vision on standing or bending (visual obscuration).
  • Pulsatile tinnitus, dizziness, mild cognitive disturbance, and upper cervical or radicular back pain
  • On examination, there may be oculomotor nerve palsies, papilloedema or optic atrophy.

Idiopathic Intracranial Hypertension diagnostic criteria:

1. Papilloedema
2. Normal neurological examination (except 6th CN palsy)
3. Normal brain parenchyma on imaging with no evidence of hydrocephalus, mass lesion or venous thrombosis.
4. Normal CSF composition
5. Raised opening pressure on lumbar puncture ≥ 25cm

IIH without papilledema (IIHWOP) diagnostic criteria:

1. Normal neurological examination
2. Normal neuroimaging
3. Normal CSF composition
4. Raised opening pressure on lumbar puncture ≥ 25cm
5. Unilateral or bilateral 6th cranial nerve palsy

Investigations

Investigations for IIH involve assessing complications of raised ICP and ruling out other causes. Investigations include:

• Ophthalmology examination to assess visual acuity, visual fields and fundoscopy
• Blood pressure measurement to rule out malignant hypertension
• Brain imaging within 24hrs of identification of papilloedema with CT/MRI and CT venography to rule out mass lesion, hydrocephalus, or venous thrombosis.
• Lumbar puncture in lateral decubitus position to measure CSF opening pressure and composition.

Management

There are 3 principles when it comes to the management of IIH:

1. Treat the underlying disease
2. Protect the vision
3. Manage headache itself

To treat the underlying disease – Weight loss is the only disease modifying therapy for typical IIH known to induce disease remission. Patients with IIH with a BMI >30 kg/m2 should be counselled about weight management, whilst also considering the biopsychosocial complexities around weight and weight loss.

To protect the vision – in the presence of declining visual function, surgical options are the most appropriate management options:

• CSF diversion procedures, e.g. ventriculoperitoneal shunt
• Optic nerve fenestration.

Lumbar drain can be a useful temporary option to protect vision whilst preparing for urgent surgical intervention.

To manage headache 

• Acetazolamide – carbonic anhydrase inhibitor. Reduces CSF production and can improve quality of life.

• Topiramate – if intolerant to acetazolamide. It has some carbonic anhydrase activity and can cause appetite suppression. Patients should be counselled about possible side effects, including teratogenicity, before prescribing topiramate.
• Acute headaches can be managed with NSAIDs and paracetamol, however, opioids are not recommended.
• Serial LP procedures (also known as therapeutic taps) can provide temporary relief of headaches; however, the CSF is rapidly replaced. It is not recommended due to potential associated risks, anxiety, and potential for acute and chronic back pain as a complication.

Follow up is advised with a multidisciplinary team, including ophthalmologist and neurologist. Frequently co-existing conditions like obstructive sleep apnoea, low mood, and polycystic ovary syndrome should be managed under the relevant specialist team.