Idiopathic Intracranial Hypertension in Pregnancy

About one-third of patients with IIH experience diplopia. This binocular, horizontal diplopia is caused by a sixth nerve palsy in 10% to 20% of patients.¹ Cranial nerves II, VI, and VII make a 90-degree bend and seem to be prone to damage at the site of the bend.¹

Pulse-synchronous tinnitus is common in IIH as well.^2,3 This generally occurs unilaterally and may be eliminated by jugular compression or the head turning to the ipsilateral side.^1,3 The sound is caused by the transmission of an increase in the vascular pulse due to high pressure on the cerebrospinal fluid (CSF).^1,3

Idiopathic intracranial hypertension most typically presents in obese women of childbearing age.^1-3 An increasing degree of obesity is generally associated with an increased risk of vision loss.^1,2 Men seem to have worse acuity and visual fields at presentation than do women.² Men are less likely to report headaches than are women and, therefore, have double the likelihood of severe vision loss.² Hence, closer monitoring and more aggressive intervention is recommended for men due to their lesser tendency for headaches.² Black patients also demonstrate more aggressive disease and, therefore, require closer monitoring and early aggressive intervention.^1,2

Papilledema is the most common sign of IIH and may be caused by several processes. In this case, most were ruled out given the patient’s normal visual acuities, pupillary 
reaction, color vision testing, BP measurement, and B-scan imaging. The patient’s systemic history was negative for thyroid-related disease, diabetes, hypertension, autoimmune disease, or infection. She had no family history of vision loss or hereditary ocular conditions. The most recent MRI was negative for any long-standing space-occupying lesion or hydrocephalus.

Pathophysiology

Several mechanisms leading to increased ICP have been proposed. These include increased brain water content, excess CSF production, reduced CSF absorption, and increased cerebral venous pressure.^2,3 There is also a suspicion of the role of sex hormones in IIH due to its high predilection for females.²

The role of vitamin A metabolism has also been studied in IIH.¹ Retinol levels are elevated in the CSF of patients with IIH. Patients may ingest an abnormally large amount of vitamin A, metabolize it abnormally, or be sensitive to its effects.^2,4 The function of adipose tissue as an actively secreting endocrine tissue may play a role in IIH due to its release of adipose tissue-derived retinol binding protein.² Other adipose-produced cytokines include leptin, which has been implicated in IIH due to its elevated levels found in the CSF of patients with IIH.²

Stenosis of the cerebral sinuses is another proposed mechanism of IIH.^1-3 Cerebrospinal fluid exits the cranium into the venous sinuses via the arachnoid villi.² An obstruction in these sinuses may impair CSF outflow and result in intracranial hypertension. Microthrombosis caused by hypercoaguable disorders may result in increased cerebral venous pressure and impaired CSF absorption as well.^2,4

Some medications have been found in association with IIH. These include tetracycline, cyclosporine, lithium, nalidixic acid, nitrofurantoin, oral contraceptives, levonorgestrel, danaxol, and tamoxifen.^1-4 Tetracycline seems to have the strongest association with IIH and should be discontinued in those patients where the association is very likely to be the causative factor.² The link to oral contraceptives may occur simply due to their association with young women most at risk for IIH.^1-3

Related:Young Man With Headache, Confusion, and Hearing Loss

Management

The goals of treatment with IIH are to preserve vision and relieve symptoms, particularly headache. The general recommendation is that pregnant women with IIH should be managed and treated the same as any other patient with IIH. However, imaging and some drug contraindications exist between these 2 groups.

The diagnostic test for IIH is a lumbar puncture, which is also the most effective treatment.^1-3,5 Lumbar puncture should be performed in the relaxed lateral decubitus position without sedation.^1-3 The opening pressure should be measured and is the most clinically significant diagnostic tool for diagnosis of IIH. Opening pressures of > 250 mm H₂O are diagnostic of IIH.^1-3,5

Weight loss is an essential part of treatment in obese patients with IIH.^1-3 A low-calorie, low-salt diet with mild fluid restriction seems to reverse the symptoms of IIH. A 5% to 10% reduction in body weight may reduce symptoms and signs of IIH.²

Carbonic anhydrase inhibitors (CAIs), such as acetalzolamide, have a multifactorial role in IIH.4 They are usually prescribed in 1 to 2 grams over several doses and function by decreasing CSF production.¹ Carbonic anhydrase inhibitors also are known to change the taste of foods and may, therefore, aid in weight loss.^1,2 Patients prescribed CAIs commonly experience a tingling in their fingers, toes, and perioral region, an indication that the medication is working.^1,2 A rare but serious adverse effect (AE) is aplastic anemia, which generally occurs in the first 6 months of treatment in elderly patients.¹ The use of CAIs in pregnancy is controversial, and although rare complications are reported, it is considered a class C drug.⁵