Idiopathic intracranial hypertension (IIH) is a syndrome characterized by increased pressure around the brain. It occurs when cerebrospinal fluid (CSF) builds up in the skull. It is called an idiopathic disease because the origin of this disease is unknown.
The incidence of IIH in the general population is thought to be about 1 per 100,000. More specifically, in obese young females, the incidence of IIH is about 20 per 100,000 and in men and children but with substantially lower frequency.
What happens in idiopathic intracranial hypertension?
A blood clot on the brain's surface (subdural haematoma) is formed because of an encephalitis infection. This leads to hydrocephalus, where fluid builds up around the brain and optic nerve. This excess fluid causes the ventricles to widen, putting pressure on the brain's tissues.
What is the possible cause of IIH?
Women make up over 90% of IIH patients, but the reason behind this gender bias for the disease is still not fully understood. It is noteworthy that prepubescent children do not exhibit any gender preference for the disease, whereas older children who get IIH after puberty are more likely to be female. This suggests that ovarian hormones play a role in the pathophysiology of the disease. Changes in hormones are a potential cause of the disease because they can be controlled by adipose tissue and obesity. Obesity and sex hormones are the two main risk factors for IIH. However, endocrine and hormonal alterations most likely contribute to the condition.
Is IIH life-threatening?
IIH does not normally affect life expectancy. The major complications from IIH arise from untreated or treatment-resistant papilledema. In various case series, the long-term risk of one's vision is significantly affected by IIH is reported to lie anywhere between 10 and 25%.
Idiopathic IH is not usually life-threatening but can be a lifelong problem. While many people find their symptoms are relieved with treatment, the symptoms can come back and significantly impact patients' lives.
Case study of a 20-year-old female with IIH:
A 20-year-old female university student presented on October 18, 2016, with a month's history of poor vision in both eyes, worse in the right. She started experiencing blackouts initially and later developed severe frontal headaches radiating to the eyes. On examination, she weighed 124 kg and her blood pressure was 149/96mmHg. This means that her severe obesity could be the root cause of her getting IIH.
The patient was referred to see the dietician for weight reduction. The dose of Acetazolamide was increased initially to 500mg three times daily and a week later to 500mg 6 hourly. On the week two review visit, her weight had dropped to 121kg, and the symptoms of headache and vision in her right eye significantly improved. This shows that her condition improved after weight loss, and the drug Acetazolamide effectively reduced the amount of CSF produced by her body.
What are the symptoms of IIH?
Headaches.
Tinnitus (ringing in the ears)
Temporary blindness.
Double vision.
Blind spots.
Neck and shoulder pain.
Peripheral (side) vision loss.
What are the earliest signs of IIH?
Early signs of IIH include changes in mental status, such as disorientation, restlessness, and mental confusion. As a result, there are often purposeless movements from the patients.
How is intracranial hypertension diagnosed?
A brain CT scan or MRI is done to exclude other possible causes of elevated CSF pressure, such as brain tumors and dural sinus thrombosis.
Eye exam to check for swelling near the optic nerve
Spinal tap or a lumbar puncture which measures an increase in CSF pressure above 250 mm H20 if they have IIH
Tests to check reflexes, balance or muscle strength
Visual Field test to check for blind spots in vision
Weight loss: For a person with a high BMI, weight loss can reduce IIH symptoms. It is recommended to lose 5% to 10% of body weight.
Medication: Some medicines manage IIH symptoms. Doctors may prescribe acetazolamide (Diamox®) or topiramate to help the body produce less CSF. Patients may also take a diuretic (water pill) to decrease fluid retention.
Surgery: In severe cases, surgery is needed for IIH. Doctors may recommend a spinal fluid shunt. A shunt is a long, thin tube placed in the brain to drain excess CSF. Or the patient may have an eye surgery called optic nerve sheath fenestration. The doctor makes small incisions around the patient's optic nerve to allow better CSF drainage.
What is the dietary advice for patients with IIH? Be conscious about the amount of fats and salt present in the diet. Patients must also limit their consumption of foods rich in vitamin A. This is because vitamin A intoxicates the CSF, which leads to an alteration of mental status. It also increases the risk of seizures, headaches and blurred vision. Foods rich in vitamin A include sweet potatoes, carrots, tomatoes, and leafy greens. Food containing tyramines should also be avoided as they cause a rise in blood pressure leading to migraine headaches. Food and drinks that are high in tyramine include cheese, pepperoni, salami, beer, and wine.
Conclusion
Idiopathic intracranial hypertension is a disease that mainly affects women in the childbearing years, and its prevalence is increasing due to the worldwide obesity epidemic. There are many risk factors that have been associated with IIH, many of which appear to be chance associations. Recognising and understanding the risk factors that truly contribute to intracranial hypertension is important in both diagnosing and understanding the pathophysiology of the disease. This disease can usually be treated by following dietary and exercise guidelines given by the doctor. But severe cases of IIH need to be treated by spinal fluid shunt or an eye surgery called optic nerve sheath fenestration. IIH is not a life-threatening disease as it can be easily diagnosed and treated, but its symptoms must be managed effectively to reduce long-term impacts.
Written By: Aditya Bagwe
Edited By: Svasti Tewari
Glossary:
Intracranial hypertension: Build up of blood pressure around the inside of the brain.
Chance: A random error appearing to cause an association between an exposure and an outcome.
Epidemic: a widespread occurrence of an infectious disease in a community at a particular time.
Hematoma: a collection (or pooling) of blood outside the blood vessel. Hematomas are classified as subdural, spinal, subungual (under the finder or toenail bed) or hepatic.
Pathophysiology: the disordered physiological processes associated with disease or injury.
Cerebrospinal fluid: The liquid that cushions the spinal cord and brain.
Papilledema: When an optic disc swelling is secondary to increased intracranial pressure.
Optic nerve sheath fenestration: It is a surgical procedure used to relieve pressure from the subarachnoid space in the setting of increased intracranial hypertension.
Subarachnoid space: the interval between the arachnoid membrane and the pia mater.
Bibliography:
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Eye Institute, National. “What Is Idiopathic Intracranial Hypertension?” Idiopathic Intracranial Hypertension | National Eye Institute, National Eye Institute, 22 Sept. 2020, https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/idiopathic-intracranial-hypertension.
Chen, John, and Michael Wall. “Epidemiology and Risk Factors for Idiopathic Intracranial Hypertension.” Idiopathic Intracranial Hypertension , National Library of Medicine, 1 Jan. 2015, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3864361/.
Tagoe, Naa N, and Vera M Beyuo. “Case Series of Six Patients Diagnosed and Managed for Idiopathic Intracranial Hypertension at a Tertiary Institution Eye Centre.” Idiopathic Intracranial Hypertension (IIH) , National Library of Medicine, 3 Mar. 2019, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6527823/
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