What are the risk factors, causes, pathophysiology, and treatment of Idiopathic Intracranial Hypertension (IIH)?

From the Guidelines

Idiopathic Intracranial Hypertension (IIH) is primarily managed through weight loss, which is the only disease-modifying therapy, and should be initiated in all patients with a BMI >30 kg/m2 at the earliest opportunity. Risk factors for IIH include female sex, obesity (BMI >30), reproductive age (20-45 years), recent weight gain, and certain medications like tetracyclines, vitamin A derivatives, and hormonal contraceptives 1. The pathophysiology involves impaired CSF absorption at arachnoid granulations, increased CSF production, or cerebral venous outflow obstruction, leading to elevated intracranial pressure that causes papilledema and potential vision loss.

Key Principles of Management

• Weight loss is the primary principle for IIH management, aiming to modify the underlying disease 1
• Protecting vision is crucial, especially in cases of progressive visual loss
• Minimizing headache morbidity is also a key principle in managing IIH 1

Treatment Approaches

• First-line medication is acetazolamide, starting at 500mg twice daily, increasing to 1000-2000mg daily if needed, to reduce CSF production
• Topiramate (25-50mg twice daily) serves as an alternative with the added benefit of appetite suppression
• For severe or rapidly progressive cases, serial lumbar punctures may provide temporary relief
• Surgical interventions include optic nerve sheath fenestration to protect vision or CSF diversion procedures like ventriculoperitoneal or lumboperitoneal shunting for intractable headaches or visual symptoms

Role of Neurovascular Stenting

• The role of neurovascular stenting in IIH is not yet established, although it has been reported to lead to an improvement in symptoms of intracranial hypertension 1
• Complications of the procedure include short-lived ipsilateral headache, stent-adjacent stenosis, vessel perforation, stent migration, and thrombosis
• Long-term antithrombotic therapy is required for longer than 6 months following neurovascular stenting treatment 1

Monitoring and Follow-Up

• Regular ophthalmologic monitoring is essential to track visual function and papilledema
• Treatment should continue until symptoms resolve and papilledema improves, typically requiring 3-6 months of therapy, with gradual medication tapering under medical supervision.

From the Research

Risk Factors

• Idiopathic intracranial hypertension (IIH) most often occurs in women of childbearing age 2
• Most patients are overweight or obese with a history of recent weight gain 2
• Obesity is a common factor in IIH, with an estimated incidence of one to three people per 100,000 people per year, occurring most commonly in obese, young women 3

Causes

• The cause of IIH is unknown, but it is characterized by signs and symptoms of raised intracranial pressure with no established pathogenesis 4
• IIH is a diagnosis of exclusion, and other causes of increased intracranial pressure must be sought with history, imaging, and cerebrospinal fluid examination before the diagnosis can be made 5

Pathophysiology

• IIH is a disorder of raised intracranial pressure of unknown etiology 6
• The pathophysiological concepts of IIH are not fully understood, but it is thought to be related to increased intracranial pressure without an identifiable cause 4

Treatment

• The main goals of treatment are alleviation of symptoms, including headache, and preservation of vision 5
• Weight loss and acetazolamide are the cornerstones in the treatment of IIH 4
• Conservative measures centre on weight loss, and pharmacological therapy includes use of diuretics such as acetazolamide 3
• Surgical interventions, such as optic nerve sheath fenestration or cerebrospinal fluid shunting, may be required to prevent further irreversible visual loss in severe cases 3, 6, 5
• Other treatments include venous sinus stenting and bariatric surgery, although the role of transverse venous sinus stenting remains unclear 3, 5