QuestionSBA
QuestionChoice
The most likely drug to be used here is acetazolamide, a carbonic anhydrase inhibitor. The patient has idiopathic intracranial hypertension, with the typical features of raised intracranial pressure (headache, tinnitus, papilloedema, visual loss). The treatment involves carbonic anhydrase inhibitors to decrease the rate of cerebrospinal fluid production
32113
a
Carbonic anhydrase inhibitor
QuestionChoice
This is the mechanism of action of furosemide, which may be considered as an adjunct to acetazolamide
32114
b
Inhibitor of the luminal Na-K-Cl cotransporter in the ascending loop of Henle
QuestionChoice
This is the mechanism of action of sumatriptan, which may be used in the treatment of acute migraine. However, this would not be effective here as the headache is secondary to idiopathic intracranial hypertension
32117
e
5HT1 receptor agonist
QuestionChoice
This is the mechanism of action of prednisolone. Steroids are not recommended for use in idiopathic intracranial hypertension as their withdrawal can cause severe rebound intracranial hypertension with visual loss, and may worsen weight gain, which is a risk factor for the condition. It may, however, be useful as a temporary measure prior to surgery in the setting of acute visual loss
32116
d
Decreases inflammation via suppression of migration of polymorphonuclear leukocytes and reversal of increased capillary permeability
QuestionChoice
This is the mechanism of action of ibuprofen, a nonsteroidal inflammatory drug that may be used for pain relief of migraines but would not be the treatment in this case
32115
c
Reversible inhibitor of cyclooxygenase-1 and 2 (COX-1 and 2) enzymes
Concept
Chapter
## Summary
 

Idiopathic Intracranial Hypertension (IIH), also known formerly as benign intracranial hypertension or pseudotumor cerebri, is a condition characterised by increased intracranial pressure in the absence of a detectable cause. It predominantly affects young, overweight women and can lead to serious consequences such as permanent visual loss if left untreated. The mainstay of management includes weight loss, acetazolamide and symptomatic management of headaches. Severe cases may require surgical intervention, particularly if there is evidence of progressive visual loss.
 

## Definition
 
IIH is a disorder of unidentified cause which leads to increased intracranial pressure, typically with an opening pressure above 25 cmH2O on lumbar puncture. 
 
It has been previously referred to as benign intracranial hypertension, though it is not benign, and pseudotumor cerebri, which can cause confusion as it is not related to an identifiable structural lesion.
 
## Epidemiology
 

This condition most frequently occurs in young and obese women, with a sex ratio of approximately 9:1 favoring women. 
 
## Aetiology
 

The aetiology of IIH remains uncertain. There are some reported associations with several drugs, including:
 

 - Oral contraceptive pill
 - Steroids
 - Tetracycline
 - Vitamin A
 - Lithium
 


## Signs and Symptoms
 

Classic symptoms of IIH include:
 

 - Non-pulsatile, bilateral headaches, typically worse in the morning or after bending forwards. Some patients may also experience morning vomiting.
 - Visual disturbances, such as transient visual darkening or loss, likely due to optic nerve ischaemia. 
 - Bilateral papilloedema seen on fundoscopy, indicating increased intracranial pressure.
 - 6th nerve palsy: horizontal diplopia
 

If untreated, permanent visual damage may result, with 1-3% of patients experiencing vision loss within a year of onset. 
 

## Differential Diagnosis
 

Differential diagnoses for IIH mainly include other causes of increased intracranial pressure or morning headaches, such as:
 

 - Brain tumour: Symptoms include new onset or change in pattern of headaches, headaches that gradually become more frequent and more severe, unexplained nausea or vomiting, vision problems, such as blurred vision, double vision or loss of peripheral vision, gradual loss of sensation or movement in an arm or a leg, difficulty with balance, speech difficulties, confusion in everyday matters, personality or behaviour changes, and seizures, especially in someone who doesn't have a history of seizures.
 - Venous sinus thrombosis: Presents with a headache, seizures, abnormal vision, and various neurological symptoms such as weakness, loss of sensation, and decreased level of consciousness. 
 - Sleep apnoea: Characterized by excessive daytime sleepiness, loud snoring, observed episodes of stopped breathing during sleep, abrupt awakenings accompanied by gasping or choking, awakening with a dry mouth or sore throat, morning headache, difficulty concentrating during the day, experiencing mood changes, such as depression or irritability, high blood pressure, and nighttime sweating.
 - Migraines: Characterised by nausea, vomitting, phonophobia and photophobia. Usually without visual loss or postural headache.
 

## Investigations
 

Several investigations are used to diagnose IIH and rule out other causes of raised intracranial pressure:
 

 - Ophthalmoscopy, which typically shows bilateral papilloedema. A referral to ophthalmology for a detailed visual field assessment may be warranted.
 - Imaging studies such as CT and MRI of the head may show signs of increased intracranial pressure. An MRI Venogram may be performed to rule out secondary causes, particularly venous sinus thrombosis.
 - Lumbar puncture is a key diagnostic tool, typically revealing an opening pressure above 20 cmH2O. An abnormal CSF profile may suggest a different diagnosis.
 

## Management
 

Managing IIH effectively includes:
 

 - Encouraging weight loss as the first-line and best-supported intervention for managing IIH.
 - Carbonic anhydrase inhibitors such as acetazolamide can be used, but are often poorly tolerated due to side effects like peripheral paraesthesia.
 - Topiramate and candesartan are also commonly used alternatives.
 - More invasive procedures such as therapeutic lumbar punctures, surgical CSF shunting or optic nerve sheath fenestration may be necessary for resistant cases to prevent progressive visual loss.
 

## Prognosis
 

The prognosis of Idiopathic Intracranial Hypertension (IIH) varies among patients. 
 

Most patients have a benign course, but a small proportion may develop severe visual impairment or blindness. 
 

Visual outcome can often be favourable if the disease is diagnosed and treated early. The visual morbidity mainly results from the delay in diagnosis or inadequate treatment which can lead to irreversible damage.
 

Weight loss has been associated with remission and can potentially result in a better prognosis. Even a modest weight loss can lead to a significant reduction in intracranial pressure. In some patients, weight gain has been linked with worsening symptoms and increased intracranial pressure.
 

## References
 

 1. Friedman, D. I., Liu, G. T., & Digre, K. B. (2014). Revised diagnostic criteria for the pseudotumor cerebri syndrome in adults and children. Neurology, 81(13), 1159–1165. [Link](https://doi.org/10.1212/WNL.0b013e31824e9821)
 2. Mollan, S. P., Davies, B., Silver, N. C., Shaw, S., Mallucci, C. L., Wakerley, B. R., Krishnan, A., Chavda, S. V., Ramalingam, S., Edwards, J., Hemmings, K., Williamson, M., Burdon, M. A., Hassan-Smith, G., Digre, K., Liu, G. T., Jensen, R. H., & Sinclair, A. J. (2018). Idiopathic intracranial hypertension: consensus guidelines on management. Journal of Neurology, Neurosurgery & Psychiatry, 89(10), 1088–1100. [Link](https://doi.org/10.1136/jnnp-2017-317440)
 3. Wall, M. (2010). Idiopathic Intracranial Hypertension. Neurologic Clinics, 28(3), 593–617. [Link](https://doi.org/10.1016/j.ncl.2010.03.003)
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Picture
A typical appearance of papilloedema.
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Papilloedema.jpeg
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2645
Idiopathic Intracranial Hypertension
Topic
16
Ophthalmology
6423
Carbonic anhydrase inhibitors, like acetazolamide, reduce cerebrospinal fluid production, aiding in the management of idiopathic intracranial hypertension.
A 45-year-old woman presents to Accident & Emergency with a one-week history of persistent headache. She was worried as she started experiencing bilateral blurring of vision in the past day. She also reports hearing the sound of 'rushing water' in both ears. Fundoscopy reveals bilateral swelling of the optic discs.

The consultant reviews her and decides to start her on medication. What is the mechanism of action of the most likely drug used?
a