Idiopathic Intracranial Hypertension: Papilledema and Neuro-Ophthalmology Referral Patterns

Idiopathic intracranial hypertension (IIH) is a syndrome that involves headache as one of its primary symptoms, and papilledema is a finding that supports this diagnosis. Permanent visual defects are serious and not infrequent complications.1 For these reasons, IIH is a syndrome that straddles the subspecialties of headache medicine and neuro-opthalmology.

IIH most commonly affects young obese women. Given the high incidence of primary headache disorders among young women,2,3 and the high prevalence of obesity,4 IIH is often considered in the differential diagnosis in this sub-population of headache sufferers. In clinical practice, funduscopic examinations are not performed frequently enough, and the exams that are performed are often unable to reliably detect abnormalities.5,6

The Problem with Neuro-Ophthalmology Referrals

If a funduscopic examination is not performed or papilledema is not appreciated on examination, providers may refer these patients to neuro-ophthalmology. Although such referrals are often appropriate, further evaluation and treatment based on clinical suspicion should not be delayed until after the patient is evaluated by a neuro-ophthalmologist, as some studies have indicated.2 In fact, early evaluation and treatment by the referring provider may actually eliminate the need for a referral to neuro-ophthalmology.

Due to the limited number of neuro-ophthalmology specialty clinics and wait times that span weeks or even months, it may be more practical from a patient care perspective to manage IIH patients without a referral to neuro-ophthalmology. As of May 2016, the estimated wait time to see a neuro-ophthalmologist at Massachusetts Eye and Ear Infirmary was at least four weeks, but this issue is not unique to Boston. Based on data from the North American Neuro-Ophthalmology Society, there are only 412 registered neuro-ophthalmologists in the United States. In addition, some states (such as Wyoming, Montana, and North Dakota) have no practicing neuro-ophthalmologists.7 In contrast, there are currently 19,216 ophthalmologists, according to the American Academy of Ophthalmology, and 16,366 neurologists, according to the American Academy of Neurology, practicing in the US.8,9 With such a lack of neuro-ophthalmologists, it is evident that neurologists and ophthalmologists have an integral role as the primary clinicians managing IIH. Therefore, it is not practical for patients with IIH to be seen by a neuro-opthalmologist before a diagnosis is made and treatment is rendered.2

Although the majority of patients with IIH have papilledema, IIH without papilledema can occur.10 Some of these patients with IIH without papilledema may actually have fluctuating papilledema with or without treatment, which would have caused even the most seasoned neuro-ophthalmologists to make a false negative diagnosis depending on what point in time a funduscopic examination was performed.

Diagnosis and Management of IIH

To expand on this subject, we must first address the question of what aspects of a patient history drive clinical suspicion of IIH. Clinical suspicion tends to increase as an increasing number of the following signs/symptoms are present:

The previously used term for IIH is pseudotumor cerebri because these headaches behave similarly to headaches that are induced by a tumor. As such, it is not inappropriate to proceed with MRI imaging to rule out a mass lesion based on clinical suspicion. Insurance companies would be hard pressed not to cover the expense of an MRI of the brain for a patient with new onset (often worsening) headaches that involve characteristics of headaches caused by a brain tumor, pulsatile tinnitus, and unexplained visual disturbances. IIH neuroimaging findings include empty sella turcica, distension of the perioptic subarachnoid space, flattening of the posterior sclerae, protrusion of the optic nerve papillae into the vitreous, and transverse cerebral venous sinus stenosis.10 Like the absence of papilledema on examination, the absence of these MRI findings should not dissuade further testing and treatment in the appropriate clinical setting.

The diagnostic characteristics for IIH were first outlined by Dandy in 1937,12 and formulated into a set of criteria by Smith in 1985,13 known as the modified Dandy Criteria. It has since been updated14 and then more recently revised.15 The diagnostic criteria continue to evolve as more is learned about this disorder, especially with the advancement of imaging techniques. Depending on the version of the Dandy Criteria used, papilledema and/or a strict CSF opening pressure cut off may or may not be required to establish the diagnosis. Even with the most recent and strict revised criteria,15 a diagnosis of IIH can still be established in the absence of papilledema, which is helpful for the subset of patients with otherwise typical IIH who do not have papilledema.16 Given the various iterations of the diagnostic criteria and the provision to diagnose probable IIH if certain required criteria are not met,15 the diagnostic interpretation of a given clinical presentation may differ from one clinician to another.

When making a diagnosis of IIH, most headache specialists refer to the International Classification of Headache Disorders 3rd Edition, Beta Version (ICHD-3b) diagnostic criteria, which are listed in Table 1.10

According to the ICHD-3b criteria, a diagnosis of IIH can only be made once a lumbar puncture (LP) has demonstrated elevated opening pressure over 250 mm CSF. As such, an LP should not be considered an unnecessary, invasive procedure in the setting of high clinical suspicion of IIH. Again, high clinical suspicion should not solely be an obese woman with headaches. In addition to diagnostic value, an LP can be of therapeutic benefit when performed in the setting of a severe headache. As such, performing routine lumbar punctures in the absence of a headache should be avoided, as the intervention will not be of any therapeutic benefit, and the opening pressure may not be at peak elevation as can occur with a severe headache. Due to the unpredictable timing of flares, it is at times recommended that patients proceed to the emergency department for an urgent diagnostic/therapeutic LP the next time they have a severe headache. A mildly elevated CSF opening pressure should not be dismissed, as CSF pressure can vary over time.10 Continuous CSF pressure monitoring studies have demonstrated that intracranial pressure elevations tend to occur over a 24-hour period, especially during sleep, which may not be noted with a ‘spot’ lumbar puncture over minutes.17

Prior to performing MRI imaging and an LP, it is reasonable to proceed with empiric IIH treatment based on clinical suspicion. Proceeding with acetazolamide treatment in the right clinical setting is appropriate in that it may improve the patient’s headache and reduce the chances of developing permanent visual loss. Treatment with acetazolamide can lead to improvement and resolution of papilledema.10 Topiramate can also be utilized, which is a medication that tends to be effective for the treatment of both IIH and migraine. The benefits of early treatment certainly outweigh the possibility that no papilledema will be appreciated during a subsequent neuro-ophthalmology evaluation. This scenario is not significantly different from treating a patient with suspected temporal arteritis with prednisone prior to proceeding with a temporal artery biopsy. Steroids may affect the biopsy results, but the consequences of not starting steroids in a timely fashion can have grave consequences.

In clinical practice, a referral to neuro-ophthalmology is at times generated if visual disturbances/deficits are a prominent and concerning feature of the clinical presentation. As such, a referral to neuro-ophthalmology is usually not necessarily to confirm the presence of papilledema, but rather to identify other potential causes of visual disturbances/deficts, to perform formal visual field testing, and to help determine if optic nerve fenestration is an intervention that should be on the radar of the physicians caring for the patient.

Conclusion

A funduscopic examination should be performed on all patients presenting with suspected IIH, and the ophthalmoscope is a valuable diagnostic tool that is heavily underutilized throughout the practice of medicine. For this reason, proper use of the ophthalmoscope is a skill that should be emphasized with all trainees. The presence of papilledema certainly supports the diagnosis of IIH, but is not a formal part of the ICHD-3b diagnostic criteria for IIH. As such, the absence or inability of a provider to appreciate papilledema should not delay further evaluations. In a clinical presentation consistent with IIH (more features than just an obese female with headaches), ruling out an intracranial mass lesion with imaging studies and performing a diagnostic/therapeutic lumbar puncture are appropriate in making the correct diagnosis. Empiric treatment with a medication to lower intracranial pressure should be instituted based on clinical suspicion. Given the long wait times for a neuro-ophthalmology consultation and a lack of neuro-ophthalmologists in many parts of the United States, delaying appropriate diagnostic and therapeutic interventions for IIH is not only impractical, but can seriously compromise patient care with at times grave consequences including blindness. n

Paul G. Mathew, MD, FAAN, FAHS, is an Assistant Professor of Neurology at Harvard Medical School and Director of Continuing Medical Education at Brigham and Women’s Hospital John R. Graham Headache Center.

Umer Najib, MD is an Assistant Professor of Neurology at West Virginia University School of Medicine in Morgantown, WV.

Regina Krel, MD is a practicing neurologist at Angel’s Neurological Centers, PC in Brighton, MA.

Paul B. Rizzoli, MD, FAAN, FAHS is an Assistant Professor of Neurology at Harvard Medical School in Boston, MA and Fellowship Director at the Brigham & Women’s Hospital John R. Graham Headache Center..

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