Laboratory Studies

Although routine blood tests are not essential, it is advised that patients with IIH should have a baseline complete blood count, electrolytes, bicarbonate, and coagulation profile (PT,PTT). These baseline tests may elucidate abnormalities that prompt consideration of alternative differential diagnoses.

The role of anemia in patients with IIH was recently investigated in a matched case-control retrospective study, which found that there was no significant association between IIH and anemia when comparing standardized CBC values. ^[32]

MRI and CT Scanning

As mentioned above, patients with bilateral disc swelling should undergo urgent neuroimaging studies to rule out an intracranial mass or a dural sinus thrombosis. This applies to all patients as even "typical" IIH patients may harbor intracranial pathology.

Brain MRI with gadolinium enhancement and Magnetic resonance venography (MRV) is the study of choice in patients with IIH, in that it provides sensitive screening for hydrocephalus, intracerebral masses, meningeal infiltrative or inflammatory disease, and dural venous sinus thrombosis. Flattening of the globes, an empty sella, distended optic nerve sheaths and slit like ventricles are common neuroradiology findings in IIH.^[33]

In addition to a brain MRI, MRV is now becoming the standard of practice in IIH to rule out a dural venous sinus thrombosis. Sagittal T1-weighted images provide excellent views of the superior sagittal sinus, and these should be included in routine brain MRI's. Extraluminal narrowing of the transverse sinuses is a common neuroradiologic finding in IIH.^[33]

Brain CT scanning is less expensive and faster than MRI and is usually adequate to rule out an intracranial lesion. However, MRI and MRV are more effective in ruling out a mass lesion and a dural sinus thrombosis, respectively. CT scanning with contrast enhancement may be necessary in patients with contraindications to MRI (ie, pacemakers, metallic clips/foreign bodies).

Lumbar Puncture

Once an intracranial mass lesion is ruled out, a lumbar puncture is indicated. The opening pressure should be measured with the patient relaxed in the decubitus position to prevent a falsely elevated pressure reading. If any specific difficulty is encountered that may have caused such a false elevation, the clinician performing the procedure must communicate this to the ophthalmologist. Unfortunately, some patients demonstrate a transiently normal pressure despite harboring IIH. An opening pressure of greater than 25 cm H₂O is considered high, however patients with typical presenting symptoms of IIH and normal opening pressures may be considered to have "probable" IIH.^[34] However, the range of normal cerebrospinal fluid (CSF) pressure in children (10th to 90th percentil) at the time of lumbar puncture is 12 to 28 cm H₂O, which is slightly higher than that in adults. ^{[35, 36, 37]}

Besides the value of the opening pressure, the clarity and color of the CSF should be noted. In addition, the CSF should be forwarded for cell count, cytology, culture, and measurement of glucose, protein, and electrolyte concentrations. All of these findings are normal in patients with IIH.

In obese patients, finding landmarks may be difficult; consequently, the tap is often performed with the patient seated. The normal CSF pressure at the foramen magnum in the seated position is nearly 50cm H₂O from the lumbar entry point in persons of average height. Therefore, the position of the patient during lumbar puncture should be considered when interpreting the CSF pressure. If possible, the patient should be moved to the lateral decubitus position before the pressure is measured.

Another approach to lumbar puncture in obese patients involves fluoroscopic guidance in the radiology department. Prone positioning on the x-ray table and increased abdominal pressure in this position may falsely elevate the CSF pressure. If the pressure is normal with the patient in the prone position, then the measurement is probably accurate. However, if it is high, the patient must be rolled into the lateral decubitus position and allowed to relax before a reliable pressure reading can be completed.

Obviously, such maneuvers carry a risk of displacing the needle from the thecal space. However, no alternative method exists for obtaining an accurate pressure reading.

Treatment & Management

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Media Gallery

Left optic disc with moderate chronic papilledema in a patient with idiopathic intracranial hypertension (pseudotumor cerebri). Paton lines (arc-shaped retinal wrinkles concentric with the disc margin) are seen along the temporal side of the optic nerve head.
Right optic disc with postpapilledema optic atrophy in a patient with idiopathic intracranial hypertension (pseudotumor cerebri). Diffuse pallor of disc and absence of small arterial vessels on surface are noted, with very little disc elevation. The disc margin at the upper and lower poles and the nasal border is obscured by some residual edema in the nerve fiber layer and secondary gliosis that persists despite the resolution of acute edema.
Most common early visual field defect in papilledema as optic nerve develops optic atrophy is inferior nasal defect, as shown in left eye field chart (left side of figure). Shaded area indicates defective portion of field. Note sharp line of demarcation between defective lower nasal quadrant and normal upper nasal quadrant along horizontal midline. This is characteristic of early papilledema optic atrophy and is referred to as nasal step or inferonasal step.

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Author

Andrea Tham, MD Resident Physician, Department of Ophthalmology, University of California, Irvine, School of Medicine

Andrea Tham, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Physicians, American Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Donny W Suh, MD, MBA, FAAP, FACS Professor, Department of Ophthalmology, Chief of Pediatric Ophthalmology and Adult Strabismus, Medical Director of Eye-Mobile, Gavin Herbert Eye Institute, UC Irvine Health, University of California, Irvine, School of Medicine; Associate Clinical Professor, Department of Pediatrics, Creighton University School of Medicine; Chief Medical Officer, Suh Precision Syringe, LLC; Medical Staff, Children’s Hospital of Orange County

Donny W Suh, MD, MBA, FAAP, FACS is a member of the following medical societies: American Academy of Ophthalmology, American Academy of Pediatrics, American Association for Pediatric Ophthalmology and Strabismus, American College of Healthcare Executives, American College of Surgeons, American Medical Association, Section on Ophthalmology, American Ophthalmological Society, International Strabismological Association, Iowa Medical Society, Metro Omaha Medical Society, National Eye Care Project, Nebraska Chapter of American Academy of Pediatrics, ORBIS, Surgical Eye Expeditions (SEE) International

Disclosure: Nothing to disclose.

Chief Editor

Andrew G Lee, MD Chair, Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital; Clinical Professor, Associate Program Director, Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch School of Medicine; Clinical Professor, Department of Surgery, Division of Head and Neck Surgery, University of Texas MD Anderson Cancer Center; Professor of Ophthalmology, Neurology, and Neurological Surgery, Weill Medical College of Cornell University; Clinical Associate Professor, University of Buffalo, State University of New York School of Medicine

Andrew G Lee, MD is a member of the following medical societies: American Academy of Ophthalmology, American Geriatrics Society, Houston Neurological Society, Houston Ophthalmological Society, International Council of Ophthalmology, North American Neuro-Ophthalmology Society, Texas Ophthalmological Association

Disclosure: Received ownership interest from Credential Protection for other.

Additional Contributors

Mark S Gans, MD Associate Professor, Director of Neuro-Ophthalmology, Interim Chair, Department of Ophthalmology, McGill University Faculty of Medicine; Clinical Director, Department of Ophthalmology, Adult Sites, McGill University Hospital Center, Canada

Mark S Gans, MD is a member of the following medical societies: American Academy of Ophthalmology, Canadian Medical Association, Canadian Ophthalmological Society, North American Neuro-Ophthalmology Society

Disclosure: Nothing to disclose.

Ariel Chen Baylor College of Medicine

Disclosure: Nothing to disclose.

Ashwini Kini, MD, FRCS Clinical Fellow in Neuro-Ophthalmology, Department of Ophthalmology, Houston Methodist Hospital

Ashwini Kini, MD, FRCS is a member of the following medical societies: All India Ophthalmological Society, Indian Medical Association

Disclosure: Nothing to disclose.

Acknowledgements

Robert A Egan, MD Director of Neuro-Ophthalmology, St Helena Hospital

Robert A Egan, MD is a member of the following medical societies: American Academy of Neurology, American Heart Association, North American Neuro-Ophthalmology Society, and Oregon Medical Association