Diagnostic criteria for idiopathic intracranial hypertension

If symptoms are present, they may only reflect those of generalized intracranial hypertension or papilledema.

This criterion implies that the diagnosis may be established in asymptomatic patients with papilledema (table 2). More commonly, symptoms of IIH that reflect generalized intracranial hypertension include headache, pulsatile intracranial noises, and double vision.4 Less frequently, neck pain, back and shoulder pain, or radicular pain occurs in adults. Other nonspecific symptoms of meningeal irritation may be present, including photophobia, nausea, and vomiting. Symptoms that are distinctly rare and more often reflect underlying cerebral venous thrombosis, venous infarction, or meningitis producing intracranial hypertension include focal symptoms, seizures, encephalopathy, or altered level of consciousness. When the onset of symptoms is acute and the course is progressive, a secondary cause is suspected.

Typical symptoms of papilledema include transient visual obscurations and visual loss. Because papilledema does not generally cause central visual field loss until it is advanced, early central visual impairment should raise concern of some other cause of optic disc edema, such as optic neuritis or anterior ischemic optic neuropathy. Central visual loss may occur in IIH if severe optic disc edema is associated with retinal edema, hemorrhages, exudates, or choroidal folds in the papillomacular bundle or macula.

If signs are present, they may only reflect those of generalized intracranial hypertension or papilledema.

Typical signs of IIH include papilledema, papilledema-associated visual loss, and ophthalmoplegia from sixth cranial nerve palsy4 or, less often, divergence insufficiency.12 Other patterns of ophthalmoplegia (i.e., third and fourth cranial nerve palsy, internuclear ophthalmoplegia, skew deviation, and diffuse bilateral ophthalmoplegia) have been reported in patients with IIH but are sufficiently atypical to raise concern of some other cause of intracranial hypertension, such as cerebral venous sinus thrombosis.13 Focal neurologic signs or encephalopathy are not consistent with IIH. Children with IIH sometimes develop signs that suggest a posterior fossa lesion, including ataxia, facial palsy, nuchal rigidity, malaise, irritability, torticollis, or Babinski sign.7 However, none of these signs is typically present in adults.

There are rare patients with otherwise typical IIH who do not have papilledema so it is not a requirement to establish the diagnosis.14 A second lumbar puncture or prolonged intracranial pressure monitoring may be necessary to document that such patients have sustained intracranial hypertension.15 The diagnosis of IIH without papilledema should not be made at symptom onset unless the patient has another condition that would preclude the development of optic disc edema, such as optic atrophy. Some infants with intracranial hypertension may not develop significant papilledema if their sutures have not fused but will have a bulging fontanelle. Slight optic disc swelling may be difficult to detect using the direct ophthalmoscope through an undilated pupil examination. Congenital, anomalous variations in optic nerve head architecture may simulate papilledema.

Documented elevated intracranial pressure measured with the patient in the lateral decubitus position.

To diagnose IIH, the lumbar CSF opening pressure should be greater than 250 mm of water measured with the patient in the lateral decubitus position with the legs extended and as relaxed as possible.16 Values between 200 and 250 mm of water are nondiagnostic.3 Because CSF pressure naturally fluctuates, a repeat lumbar puncture may be necessary if the opening pressure is low in the appropriate clinical setting. Transducer monitoring through a lumbar drain for 6 to 24 hours or 24-hour intracranial pressure monitoring is only occasionally needed to confirm the diagnosis.15 Conversely, patients with chronic daily headaches but no papilledema may have an erroneously elevated CSF pressure from the Valsalva that accompanies crying or anxiety in acute pain.

Those patients requiring lumbar puncture under fluoroscopy present an additional challenge, as the procedure is generally performed by a radiologist who places the patient in the prone position. Until comparable data of lumbar puncture opening pressures obtained in the same patient in the prone and lateral decubitus positions are available, prone measurements are unsatisfactory.

Normal CSF composition.

CSF composition should be normal with no evidence of pleocytosis, cellular atypia, or hypoglycorrhachia. The CSF protein in patients with IIH is within the normal range.17

No evidence of mass, structural, or vascular lesion on MRI or contrast-enhanced CT for typical patients, and MRI and MR venography for all others.

Perhaps the biggest controversy among physicians treating patients with IIH is the choice of neuroimaging studies. Although CT is adequate to exclude hydrocephalus and most mass lesions causing intracranial hypertension, many other causes of intracranial hypertension are not detected on unenhanced CT. These include venous sinus thrombosis, radiographic signs of meningeal infiltration, and isodense tumors. MRI will detect the vast majority of such changes. Incorporating MR venography further enhances the ability to detect most symptomatic patients with venous–sinus occlusions causing intracranial hypertension and masquerading as IIH.18-20⇓⇓

The incidence of venous–sinus thrombosis in typical patients with IIH is sufficiently low that CT is generally acceptable to fulfill this criterion if the clinical presentation is otherwise typical.21,22⇓ If CT is the only alternative because of availability or body weight limitation, a contrast-enhanced study should be performed.

For atypical patients with suspected IIH, the incidence of venous–sinus thrombosis and other vascular anomalies simulating IIH is sufficiently high that MRI and MR venography are recommended.9,23-25⇓⇓⇓ MRI and MR venography should also be considered for adults and children with a recent history of sinus infection or otitis media, those with a “fulminant” presentation of rapidly deteriorating vision, or patients who do not respond to conventional therapy.

Radiographic signs of increased intracranial pressure in IIH include flattening of the posterior globe where the optic nerve inserts in 80% of patients, empty sella in 70% of patients, and distension of the perioptic nerve sheath in 45% of patients.26 However, these radiographic signs cannot be used as a substitute for measuring the intracranial pressure during lumbar puncture or for examining the CSF constituents because they are nonspecific. A small and asymptomatic Chiari I malformation may occasionally be present. Slit-like ventricles are not a sign of IIH and the ventricular size should be normal for the patient’s age.27

No other cause of intracranial hypertension identified.

Once criteria 1 through 5 have been met, there remain a small number of medical conditions and medications that may mimic IIH (table 3).28 The small number of patients enrolled in case-controlled studies limits the establishment of definite associated conditions and toxic medications.3,29,30⇓⇓ Still, adequate clinical experience exists to justify a diligent scrutiny of the patient’s history and medication intake, along with laboratory testing, as indicated clinically. If one of these conditions is present, it precludes the diagnosis of IIH, and indicates a secondary cause of intracranial hypertension. The conditions listed in table 3 are subject to revision as new information becomes available. Many of the conditions previously thought to be associated with IIH—such as mastoiditis, birth control pill use, and systemic lupus erythematosus—are based on the presence of venous–sinus thrombosis or corticosteroid use.