Overdiagnosis of Idiopathic Intracranial Hypertension
By Louise M. Klebanoff, MD
Assistant Professor of Clinical Neurology, Weill Cornell Medical College
Dr. Klebanoff reports no financial relationships relevant to this field of study.
SYNOPSIS: Idiopathic intracranial hypertension is over-diagnosed because of a lack of physician expertise in performing accurate ophthalmoscopy. When considering the diagnosis, referral to a neuro-ophthalmologist is strongly recommended.
SOURCE: Fisayo A, et al. Overdiagnosis of idiopathic intracranial hypertension. Neurology 2016;86:341-350.
Idiopathic intracranial hypertension (IIH) with papilledema is a clinical syndrome characterized by elevated intracranial pressure (ICP) of unknown etiology. The condition is seen primarily in young, obese women presenting with headaches, visual obscuration, double vision due to sixth nerve palsies, and pulsatile tinnitus. Although rare cases of IIH without papilledema have been described, the vast majority of patients have optic nerve head edema. As awareness of IIH increases, there is a risk of overdiagnosis of IIH. Primary headache disorders are common in young women. The incidence of obesity in this population is also on the rise. Physicians may be biased in making a diagnosis of IIH in young, obese women with chronic headaches. Physicians, even those trained in ophthalmology and neurology, are not adequately trained in performing and interpreting the fundoscopic examination, potentially leading to incorrect diagnoses, invasive diagnostic testing, and inappropriate treatments.
Fisano et al performed a retrospective study of patients referred for neuro-ophthalmological consultation at a tertiary health care institution. Over an 8-month period, 165 patients were referred for evaluation of previously diagnosed IIH (86) or suspected IIH (79). Almost 40% (34 patients) with previously diagnosed IIH did not have IIH; 16 had pseudopapilledema and nine had primary headache disorders. Of the 79 patients referred with a suspicion of IIH, < 20% (15 patients) were diagnosed with IIH after re-assessment.
Most of the diagnostic errors resulted from the inability to perform an accurate ocular fundus examination coupled with the challenges of deviating from a previously suspected diagnosis (often due to the bias of assuming that obese woman with headaches have IIH). In this study, 20% of referring providers did not attempt to perform ophthalmoscopy, and 44% of those who performed the examination misinterpreted the appearance of the optic nerve over-diagnosing papilledema.
Incidental non-specific findings on MRI, such as empty sella, dilatation of the optic nerve sheath, or anomalies of the transverse venous sinuses, also contribute to the overdiagnosis of IIH and lead to additional testing such as lumbar puncture. However, the cerebrospinal fluid (CSF) opening pressure is not always helpful in accurately identifying patients with IIH. The diagnosis of IIH cannot be made on the basis of CSF opening pressure alone. In adults, the cutoff for normal opening pressure is 25 cm of water; however, the measurement of opening pressure can be affected by poor positioning, the use of sedation, failure to relax the legs, or poor needle position. Most headache patients with moderately elevated ICP but without papilledema have primary headache disorders rather than IIH.
This retrospective study highlights the challenges of making a correct diagnosis of IIH. Patients presenting with chronic headache, even obese young women, need careful physical examination, especially accurate examination and interpretation of the ocular fundus, before embarking on invasive diagnostic testing and treatments for IIH.
Idiopathic intracranial hypertension is over-diagnosed because of a lack of physician expertise in performing accurate ophthalmoscopy. When considering the diagnosis, referral to a neuro-ophthalmologist is strongly recommended.
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