Idiopathic Intracranial Hypertension

Idiopathic intracranial hypertension (IIH) is a neurological disorder characterized by an increased pressure within the skull, similar to the pressure caused by a brain tumor. It is caused by a build up of cerebrospinal fluid (CSF) around the brain (the fluid which surrounds the brain and spinal cord). This can put pressure on the optic nerve, which helps you to see, leading to vision changes or temporary blindness.

Idiopathic means ‘unknown cause’, intracranial means ‘in the skull’ and hypertension means ‘high pressure’. IHH is also sometimes referred to as pseudotumor cerebri, which means ‘false brain tumor’.

What causes idiopathic intracranial hypertension?

The exact cause of IIH remains unknown, but several factors contribute to the condition:

• Increased intracranial pressure: IIH is defined by increased pressure within the skull. This pressure can cause symptoms and, if left untreated, may lead to vision loss.
• Abnormal cerebrospinal fluid (CSF) circulation: CSF is produced and absorbed in the brain. In IIH, the balance between CSF production and absorption is disrupted, leading to increased pressure.
• Unknown Triggers: While the exact triggers are unknown, factors like obesity and hormonal changes are believed to play a role in IIH development. Some medications, particularly those related to hormonal treatments, may also contribute.

Who is affected by idiopathic intracranial hypertension?

IIH predominantly affects women of childbearing age, particularly those who are overweight or obese.

The primary risk factors for IIH include:

• Gender: IIH primarily affects women aged 20 to 50 years old.
• Weight: Being overweight or obese significantly increases the risk. Weight loss can help manage the condition.
• Hormonal factors: Some hormonal medications and conditions that affect the hormones (such as hypothyroidism or hyperthyroidism) may increase the risk of IIH.
• Anemia: A condition characterized by a decrease in the number of red blood cells or a decrease in the amount of hemoglobin in the blood, anemia has also been suggested as a possible risk factor for IIH, although the exact relationship is not fully understood.
• Medications: Some medications are associated with IIH, including:

• Cycline antibiotics: Antibiotics such as tetracycline, doxycycline and minocycline, which are commonly used to treat bacterial infections, have been linked to IIH.
• Isotretinoin and vitamin A derivatives: Isotretinoin is a potent medication used for the treatment of severe acne. It has been associated with an increased risk of IIH, and patients taking isotretinoin should be closely monitored for symptoms of intracranial hypertension.
• Corticosteroids: While they can be prescribed for a wide range of conditions, including inflammatory diseases and allergies, corticosteroids are another class of medications that may be associated with IIH. These drugs can cause fluid retention and weight gain, both of which can contribute to increased intracranial pressure.
• Growth Hormone: Some individuals, often children, are prescribed growth hormone as part of their treatment. Growth hormone therapy has been linked to the development of IIH in certain cases.
• Oral contraceptives and hormone replacement therapy: Some hormonal medications, including certain oral contraceptives and hormone replacement therapy, have been suggested as potential risk factors for IIH, particularly in women.

What are the symptoms of idiopathic intracranial hypertension?

The most common sign of IHH is severe headache. It can come on suddenly and feel like an intense, throbbing pain at the back of the head.

Other symptoms of IIH include:

• Dizziness: This usually accompanies the headaches and is worse when the head moves.
• Double vision: This is caused by the pressure placed on the nerves controlling eye movement, resulting in misalignment of the eyes.
• Visual disturbances: These can range from blurred or double vision to transient visual obscurations. They occur when blood flow to the optic nerves is compromised, leading to temporary vision loss. In severe cases, these disturbances can lead to visual loss or even blindness.
• Pulsatile tinnitus: Patients may experience a pulsating or whooshing sound in the ears. This occurs due to elevated intracranial pressure, which can affect blood flow within the brain and around the ear.
• Papilledema: Papilledema is optic disc swelling due to increased intracranial pressure. This is a hallmark sign of IIH and can be observed during eye examinations. It occurs in 100% of IIH patients, but it might not be immediately apparent.

How is idiopathic intracranial hypertension diagnosed?

A comprehensive, multi-step diagnostic approach involving the evaluation of symptoms, neuroimaging, lumbar puncture, and ophthalmologic assessments are essential to confirm a diagnosis of IIH and guide appropriate treatment.

Firstly, your doctor will discuss your symptoms in detail and perform an examination.

Ophthalmologic evaluations are essential to assess the impact of IIH on the optic nerve and visual function. Ophthalmologic evaluations may include:

• Optic nerve assessment: Ophthalmologists examine the optic nerve for signs of swelling and may also use imaging techniques, such as optical coherence tomography (OCT), to quantify optic nerve swelling.
• Visual field testing: This test assesses the visual field and can determine the extent of optic nerve damage. It is crucial in monitoring disease progression and treatment effectiveness.

Neuroimaging plays a crucial role in the diagnosis of IIH. Brain imaging may include:

• Magnetic resonance imaging (MRI): This is primarily used to rule out other potential causes of the pressure. It helps doctors see any abnormalities, tumors, or structural issues in the brain.
• Magnetic resonance venography (MRV): This examines the venous sinuses, as venous abnormalities can contribute to IIH.

A lumbar puncture is another key diagnostic procedure, which provides valuable information about CSF pressure and composition.

Additional tests

Sometimes, further tests may be needed to rule out other causes of symptoms. These may include blood pressure checks, blood tests, and endocrine evaluations to identify hormonal factors that can play a role in IIH.

How is idiopathic intracranial hypertension treated?

For most people, IIH symptoms improve with treatment, which may include:

Diet and Lifestyle Changes

Achieving and maintaining a healthy weight is crucial. A registered dietitian or nutrition specialist can help create a tailored weight loss plan that includes a balanced diet and regular physical activity.

Medications

Acetazolamide is the primary medication used to treat IIH. It works by reducing the production of CSF and therefore decreasing intracranial pressure. Side effects may include tingling in the fingers and toes, frequent urination, and a metallic taste in the mouth. Topiramate may be prescribed as an alternative, which also reduces CSF production. Side effects may include cognitive changes and weight loss.

A diuretic called furosemide can help the body excrete excess fluid and reduce intracranial pressure. Side effects include increased urination and electrolyte imbalances.

Other Medications: Other medications can be provided to help manage specific symptoms, such as pain relievers for headaches.

Surgical Interventions

Optic Nerve Sheath Fenestration: In this procedure, small windows are created in the protective sheath around the optic nerve to relieve pressure. It is typically considered when vision loss is progressive or severe and doesn't respond to medications.

Shunt Placement: A shunt, such as a lumboperitoneal or ventriculoperitoneal shunt, may be implanted to divert excess CSF away from the brain, reducing intracranial pressure.

Venous Stenting: In some cases, a stent may be placed in the transverse sinus, a major blood vessel that drains blood and CSF from the brain. This can help improve CSF drainage and reduce pressure.

Bariatric Surgery: For individuals with obesity related IIH, weight loss surgery may be recommended. Procedures like gastric bypass or gastric sleeve surgery can lead to significant weight loss, which often alleviates intracranial pressure.

A multidisciplinary approach to treatment

Working closely with a multidisciplinary healthcare team, like the one offered at Cleveland Clinic Abu Dhabi’s Neuro-Ophthalmology Program, that includes neurologists, neuro-ophthalmologists, and neurosurgeons, is an important factor in determining the most appropriate treatment plan. The choice of treatment will depend on the severity of symptoms, overall health, and the response to previous interventions.

Regular assessments are needed to monitor the effectiveness of treatment and to make adjustments as needed. Managing IIH is often a long-term process, and a personalized approach is key to improving symptoms and preventing vision loss.

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