PSEUDOTUMOR CEREBRI

Signs and Symptoms

Champagne cork appearance of papilledema in PTC.

Pseudotumor cerebri (PTC), also known as idiopathic intracranial hypertension, is encountered most frequently in young, overweight women between the ages of 20 and 45.^1,2 Headache is the most common presenting complaint, occurring in more than 90% of cases seen.³ Dizziness, nausea and vomiting may also be encountered, but typically there are no alterations of consciousness or higher cognitive function. Tinnitus, or a "rushing" sound in the ears, is another frequent complaint. Visual symptoms are present in up to 70% of all patients with PTC, and include transient visual obscurations, general blurriness, and intermittent horizontal diplopia.³ These symptoms tend to worsen in association with Valsalva maneuvers and changes in posture.

Funduscopic evaluation demonstrates bilaterally swollen, edematous optic nerves consistent with true papilledema. Ophthalmoscopy may reveal striations within the nerve fiber layer, blurring of the superior and inferior margins of the neural rim, disc hyperemia, and capillary dilation. More severe presentations involve engorged and tortuous retinal venules, peripapillary hemorrhages and/or cotton-wool spots, and circumferential retinal microfolds (Paton's lines). Chronic papilledema may result in atrophy of the nerve head, with associated pallor and gliosis. Most cases of true papilledema will not present with a relative afferent pupillary defect; however, visual field deficits may be present. The most common visual field defect associated with PTC is an enlarged blind spot, followed by a nasal visual field defect, typically affecting the inferior quadrants. Other field losses seen in PTC include arcuate defects, generalized constriction, and least commonly, cecocentral scotoma.⁴ Sixth-nerve palsies, usually unilateral and intermittent, may be seen as well.

Pathophysiology

Pseudotumor cerebri is a syndrome disorder that involves elevated intracranial pressure in the absence of mass lesion, hydrocephalus, hemorrhage or other identifiable intracranial pathology. The Dandy Criteria (originally penned by Walter E. Dandy in 1937) delineates the diagnostic paradigm for PTC. Individuals such as J. Lawton Smith and Michael Wall have modified these criteria over the years. Most recently, Friedman and Jacobson published their diagnostic criteria, which includes the following:⁵

1. If symptoms present, they may only reflect those of generalized intracranial hypertension or papilledema.
2. If signs present, they may only reflect those of generalized intracranial hypertension or papilledema.
3. Documented elevated intracranial pressure measured in the lateral decubitus position.
4. Normal cerebrospinal fluid (CSF) composition.
5. No evidence of hydrocephalus, mass, structural, or vascular lesion on MRI or contrast-enhanced CT for typical patients, and MRI and MR venography for all others.
6. No other cause of intracranial hypertension identified.

The precise mechanism of PTC is not fully understood; however many consider it to be a result of poor CSF absorption by the meninges surrounding the brain and spinal cord. Many conditions and factors have been proposed as causative or contributory agents, including exogenous drugs (e.g., naladixic acid, tetracycline, minocycline, corticosteroids, vitamin A), endocrinologic abnormalities, anemias, blood dyscrasias, and chronic respiratory insufficiency, including obstructive sleep apnea.⁶ Another interesting theory involves increased intra-abdominal pressure (the result of obesity), with subsequent elevation of intrathoracic pressure with diminished venous drainage from the brain.⁷ Though current theories are not without merit, there is still little consensus on the exact etiology of PTC.

Whatever the cause, the subsequent result is elevation of intracranial pressure. However, because the process is typically slow and insidious, there is ample time for the ventricular system to compensate. This is the reason that there is no dilation of the cerebral ventricles in PTC. Increased intracranial pressure induces stress on the peripheral aspects of the brain, including the cranial nerves. Stagnation of axoplasmic flow in the optic nerve (CN II) results in papilledema and transient visual obscurations; when the abducens nerve (CN VI) is involved, the result is intermittent nerve palsy and diplopia.

Management

All patients presenting with suspected papilledema or other manifestations of intracranial hypertension warrant prompt medical evaluation and neuroimaging. Current protocol dictates that patients presumptively suspected of having true papilledema undergo magnetic resonance imaging within 24 hours. The purpose of this test is to rule out any space occupying mass lesions; thus, intravenous contrast media should be utilized unless medically contraindicated. In cases of PTC, neuroimaging typically displays small to normal-sized cerebral ventricles with otherwise normal brain structure. Patients with unremarkable radio-graphic studies should be subsequently referred for neurosurgical consultation and lumbar puncture. Additional medical testing may include serologic and hematological studies, depending upon the disposition of the attending physician.

Less severe disc edema in the fellow eye.

Therapy for patients with PTC varies, but in most instances systemic medications are initiated as a first line treatment. Typically, the drug of choice for the initial management of PTC is oral acetazolamide (Diamox, Wyeth), although other diuretics including chlorthalidone (Hygroton, Rhone) and furosemide (Lasix, Aventis) may also be used effectively.

Corticosteroid therapy is considered controversial in the management of PTC. While a short-term course of oral or intravenous dexamethasone may be helpful in initially lowering intracranial pressure, it is not considered to be an effective long-term therapy because of the potential for systemic and ocular complications. For patients in whom conventional medical therapy fails to alleviate the symptoms and prevent pathologic decline, surgical intervention is the only definitive treatment. Optic nerve sheath fenestration is recommended for those patients with chronic disc edema and severe or progressive vision loss. Although this technique fails to directly address the issue of elevated intracranial pressure, it has been shown to stabilize or improve visual function in more than 90% of patients, and may even help alleviate headaches.^8,9 Patients with more severe complications or recalcitrant PTC may require cerebrospinal fluid shunting procedures. The initial success rate of such procedures is, however, less than 50%.¹⁰

Optometric management of patients diagnosed with PTC should include careful and frequent evaluation with threshold visual field assessment, acuity measurement, contrast sensitivity testing and indirect ophthalmoscopy. Photodocumentation of the nerve heads should also be performed. Weight loss should be strongly encouraged. To that end, gastric bypass surgery has recently been suggested as a course of therapy for PTC associated with morbid obesity.¹¹

Clinical Pearls

• Past literature refers to PTC as benign idiopathic intracranial hypertension; however, it should be stressed that this condition is far from benign. Patients may suffer intractable headache, severe nausea, intermittent diplopia and permanent vision loss if not properly managed.
• While PTC is most commonly encountered in obese women of childbearing age, it may be encountered in patients of both sexes and various ages. A number of cases involving male children have been documented.

Other reports in this section

• Traumatic Optic Neuropathy
• Orbital Inflammatory Pseudotumor
• Brown's Syndrome
• Pseudotumor Cerebri