Thursday, February 4, 2016

Overdiagnosis of idiopathic intracranial hypertension

Fisayo A, Bruce BB, Newman NJ, Biousse V. Overdiagnosis of idiopathic
intracranial hypertension. Neurology. 2016 Jan 26;86(4):341-50.



To delineate the factors contributing to overdiagnosis of idiopathic intracranial hypertension (IIH) among patients seen in one neuro-ophthalmology service at a tertiary center.


We retrospectively reviewed new patients referred with a working diagnosis of IIH over 8 months. The Diagnosis Error Evaluation and Research taxonomy tool was applied to cases referred with a diagnosis of IIH and a discrepant final diagnosis.


Of 1,249 patients, 165 (13.2%) were referred either with a preexisting diagnosis of IIH or to rule out IIH. Of the 86/165 patients (52.1%) with a preexisting diagnosis of IIH, 34/86 (39.5%) did not have IIH. The most common diagnostic error was inaccurate ophthalmoscopic examination in headache patients. Of 34 patients misdiagnosed as having IIH, 27 (27/34 [79.4%]; 27/86 [31.4%]) had at least one lumbar puncture, 29 (29/34 [85.3%]; 29/86 [33.7%]) had a brain MRI, and 8 (8/34 [23.5%]; 8/86 [9.3%]) had a magnetic resonance/CT venogram. Twenty-six had received medical treatment, 1 had a lumbar drain, and 4 were referred for surgery. In 8 patients (8/34 [23.5%]; 8/86 [9.3%]), an alternative diagnosis requiring further evaluation was identified.


Diagnostic errors resulted in overdiagnosis of IIH in 39.5% of patients referred for presumed IIH, and prompted unnecessary tests, invasive procedures, and missed diagnoses. The most common errors were inaccurate ophthalmoscopic examination in headache patients and thinking biases, reinforcing the need for rapid access to specialists with experience in diagnosing optic nerve disorders. Indeed, the high prevalence of primary benign headaches and obesity in young women often leads to costly and invasive evaluations for presumed IIH.

Commentary on the above:
Galetta SL, Digre KB. Misdiagnosing idiopathic intracranial hypertension:
You've got some nerve. Neurology. 2016 Jan 26;86(4):318-9.

The article has the limitations inherent in a retrospective study. It is difficult to judge by just reviewing records what the confidence of a particular diagnosis is by the referring doctor. Therefore, referral bias of the most challenging cases may be likely. In some patients, disc swelling may resolve over time and with treatment. There are patients with IIH who do not manifest disc swelling; these patients may be more frequent than once recognized, particularly among those with headache. Vascular headaches commonly occur in the setting of IIH, and many of these patients have chronic daily headaches. There may be variability in the interpretation of neuroimaging findings and some of the misdiagnosis of IIH may reside with the neuroradiologists themselves. 

Where do we go from here? It is clear that we need multicenter prospective studies to better understand the true frequency of IIH misdiagnosis. Effects of referral bias may be magnified in a single-center study by virtue of practices and other factors unique to a given geographical area. The emergence of telemedicine might bring neuro-ophthalmologists and other experts in ophthalmoscopy closer to practicing neurologists. Reimbursement and compensation for telemedicine are issues that still need to be worked out. The digital world is bringing us closer together, and is leveling the playing field for certain technical skills. Nonetheless, fundus interpretation will continue to require basic clinical expertise that ultimately trumps technology.


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