What is pseudotumor cerebri (idiopathic intracranial hypertension)?

What is Pseudotumor Cerebri (Idiopathic Intracranial Hypertension)?

Pseudotumor cerebri, now termed idiopathic intracranial hypertension (IIH), is a syndrome of elevated intracranial pressure without an identifiable cause, occurring predominantly in obese women of childbearing age, characterized by papilledema and risk of permanent vision loss if untreated. 1

Definition and Diagnostic Criteria

IIH is defined by the combination of raised intracranial pressure without hydrocephalus or mass lesion, normal cerebrospinal fluid (CSF) composition, and no underlying identifiable etiology. 1 The diagnosis requires:

• Papilledema on examination 1
• Normal neurological examination (except for cranial nerve abnormalities) 1
• Normal brain parenchyma on neuroimaging without hydrocephalus, mass, structural lesion, or abnormal meningeal enhancement 2
• Elevated lumbar puncture opening pressure >250 mm H₂O 2
• Normal CSF composition 1

Epidemiology and Risk Factors

The condition occurs predominantly in women with a female-to-male ratio of 7:1, with a mean age of 27 years. 3 The overall age-adjusted and gender-adjusted annual incidence is 2.4 per 100,000 and is increasing, strongly associated with the obesity epidemic. 1

The striking association with obesity is a defining feature, with the condition primarily affecting overweight females of childbearing age. 4

Clinical Presentation

Primary Symptoms

Headache occurs in nearly 90% of patients with IIH, typically holocephalic or unilateral throbbing, worse in the morning after supine positioning and improving with upright posture throughout the day. 4 The headache is progressively more severe and frequent, though the phenotype is highly variable and may mimic other primary headache disorders. 1

Associated Symptoms

• Transient visual obscurations (unilateral or bilateral darkening of vision lasting seconds) 1
• Pulsatile tinnitus 1, 4
• Visual blurring 1
• Horizontal diplopia (typically due to sixth nerve palsy) 1, 4
• Nausea and vomiting related to elevated intracranial pressure 4
• Back pain, dizziness, neck pain, cognitive disturbances, and radicular pain 1

None of these symptoms are pathognomonic for IIH. 1

Neuroimaging Findings

MRI of the head and orbits is the most useful imaging modality for initial evaluation. 5 Secondary signs of elevated intracranial pressure on MRI include:

• Empty or partially empty sella 2, 4
• Posterior globe flattening (56% sensitivity, 100% specificity) 4
• Enlarged optic nerve sheaths 2, 4
• Horizontal tortuosity of optic nerves (68% sensitivity, 83% specificity) 4
• Intraocular protrusion of optic nerve (40% sensitivity, 100% specificity) 4

CT venography (CTV) or MR venography (MRV) should be performed to evaluate cerebral venous sinuses. 5

Pathophysiology

Although the underlying pathogenesis is not fully understood, most theories focus on intracranial venous hypertension and/or increased CSF outflow resistance and how this relates to obesity. 6 The condition represents a syndrome of elevated intracranial pressure rather than a true tumor, hence the historical term "pseudotumor cerebri." 7

Clinical Significance and Prognosis

The term "benign intracranial hypertension" should be abandoned, as permanent visual impairment can complicate the condition if untreated. 8 Papilledema, if untreated, can cause progressive irreversible visual loss and optic atrophy. 7

Treatment failure rates are substantial, with worsening vision after stabilization occurring in 34% of patients at 1 year and 45% at 3 years. 5 Failure to improve headache occurs in one-third to one-half of treated patients. 5

Three Main Treatment Principles

The consensus guidelines identify three fundamental goals: 1

1. Treat the underlying disease (primarily weight loss) 1
2. Protect the vision 1
3. Minimize headache morbidity 1

Common Diagnostic Pitfalls

The emergency department diagnosis may be complicated by atypical clinical features, with 27% of patients not diagnosed on their initial visit. 3 Atypical features include paresthesias, neck/back pain, unilateral headache, vertigo, and nystagmus. 3

Papilledema, the ophthalmoscopic hallmark of IIH, may not be detected initially in 21% of patients. 3 Once papilledema has resolved, caution is needed for asymptomatic patients at presentation who may remain asymptomatic during recurrence. 5