Diagnosis: Idiopathic Intracranial Hypertension (Pseudotumor Cerebri)
Idiopathic intracranial hypertension (IIH), formerly referred to as pseudotumor cerebri, occurs due to increased intracrainal pressure (ICP) in the setting of normal neuroimaging. The disease is thought to be due to excess CSF production and insufficient CSF resorption, causing increased ICP. The clinical picture and physical exam, notably fundoscopy, can point towards the diagnosis of IIH. Fundoscopic examination will often reveal bilateral swelling of the optic discs, which is referred to as papilledema when the etiology of the disc edema is increased intracranial pressure. IIH is a diagnosis of exclusion, so all other causes of high ICP must be thoroughly evaluated. Neuroimaging must be performed to rule out other causes such as a space-occupying lesion, and prior to performing lumbar puncture. Lumbar puncture must be performed to confirm normal CSF composition and assess the level of elevation in intracranial pressure, by measurement of opening pressure. It will show an elevated opening pressure >25 cm H2O with a normal CSF analysis. This diagnostic lumbar puncture often alleviates symptoms for patients temporarily. (Above left image credit: CC BY-SA 4.0)
The modified Dandy Criteria, used to diagnose patients with IIH, includes the following:
- Symptoms and signs of increased intracranial pressure (ie headache, visual obscurations, nausea, vomiting)
- No other neurologic abnormalities or impaired level of consciousness
- Elevated intracranial pressure with normal CSF composition
- A neuroimaging study that shows no etiology for intracranial hypertension
- No other cause of intracranial hypertension apparent
Consider IIH on the differential when there are signs of increased intracranial pressure (eg., headaches, papilledema) in an otherwise healthy patient. Although the underlying pathogenesis remains to be further explored, there is a strong association between IIH and obesity. IIH most commonly presents in young, obese women (BMI >30 kg/m2) of childbearing age. The symptoms can vary, but almost all patients will present with headache and visual obscurations, such as transient visual loss with positional changes or Valsalva. Unilateral or bilateral abducens nerve (CNVI) palsy may be associated with IIH, as well as visual acuity and visual field loss in severe cases, but the rest of the neurologic exam is otherwise intact. (The above left image is an example of a right CNVI palsy, image credit: © 2020 American Academy of Ophthalmology).
The headache is generally constant, and occurs daily or nearly every day, usually described as pulsating or throbbing. It can be accompanied by nausea and vomiting. Other common symptoms include pulsatile tinnitus (“whooshing sound”), back pain, dizziness, neck pain, and photophobia, with approximately half of patients presenting with these symptoms. Certain known triggers associated with the development of IIH include excessive Vitamin A and its metabolites in the form of isotretinoin (acne medication), as well as growth hormone.
Weight loss is recommended in all obese patients. 5-10% reduction in weight can lead to significant improvement in symptoms. The first line medical treatment is acetazolamide, a carbonic anhydrase inhibitor, which works by decreasing the production of CSF. If the patient does not respond adequately to acetazolamide, furosemide can be added. Topiramate is another alternative medication that can be used if acetazolamide is contraindicated. However, patients must be counseled on possible adverse ocular symptoms of topiramate (see case 9).
If medical management fails, surgical interventions including placement of a CSF shunt (ventriculo-peritoneal (VP) or lumbo-peritoneal (LP) shunt) or optic nerve sheath fenestration may be considered. CSF shunting is typically effective for improving headache symptoms, while optic nerve sheath fenestration is often reserved for patients with vision loss. Due to potential complications, serial lumbar punctures are not recommended long term, but can be used in the interim while awaiting definitive surgical management. If IIH progresses untreated, it can lead to permanent vision loss (The above left image shows a diagram of a VP shunt, image credit: License CC BY-SA 4.0).
References and Additional Resources:
1. “EyeWiki: Pseudotumor Cerebri (Idiopathic Intracranial Hypertension).” Available at: https://eyewiki.aao.org/Pseudotumor_cerebri_(idiopathic_intracranial_hypertension).
2. Biousse V. Idiopathic intracranial hypertension: Diagnosis, monitoring and treatment. Rev Neurol (Paris). 2012;168(10):673–683.
3. Jensen. RH, Radojicic A, Yri H. The diagnosis and management of idiopathic intracranial hypertension and the associated headache. Ther Adv Neurol Disord. 2016;9(4):317-326.
4. Lee AG, Wall M. (2015). Idiopathic intracranial hypertension (pseudotumor cerebri): Clinical features and diagnosis. Brazis PW & Wilterdink JL (Eds), UptoDate. Available at: https://www.uptodate.com/contents/idiopathic-intracranial-hypertension-pseudotumor-cerebri-clinical-features-and-diagnosis.
5. Thurtell MJ, Wall M. Idiopathic intracranial hypertension (pseudotumor cerebri): recognition, treatment, and ongoing management. Curr Treat Options Neurol. 2013;15(1):1–12.
Neuro-oph Case 2 Index