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paul lederer, Dmitri Poltavski; Utility of VEP in identifying concussion history in patients with Convergence Insufficiency.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1498.
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© 2017 Association for Research in Vision and Ophthalmology.
A number of studies have suggested utility of VEP testing in identifying individuals with a history of mTBI. There is also evidence of frequent occurrence of oculomotor deficits in patients with a history of mTBI. The present study was intended to develop diagnostic criteria using N75-P100 VEP for discriminating between patients with Convergence Insufficiency (CI) and a previous history of mTBI (i.e. concussion) and those with CI and no prior history of concussion.
Seventy-nine patients with CI were selected from 150 patients who visited a Midwestern clinic in a 6 month period and received VEP evaluation. Thirty-five of them reported a history of one or more concussions with the last concussion sustained at least 12 months prior to their VEP assessment. Patients with other diagnoses (e.g. strabismus, amblyopia, convergence excess, general neurological delays, dyslexia) were excluded from the study. The VEP-T module used in the present study was developed by Diopsys to separate the parvocellular (sustained) and magnocellular (transient) pathways by presenting slow (2Hz), high contrast (85%) edgy checkerboard stimuli of 2 different sizes (16 x 16 and 8 x 8) and fast (4Hz), low contrast (10%) non-edgy stimuli (vertical sinusoidal grating) with spacial frequencies of 16 and 8 vertical bars. We tested two models to discriminate between the two CI groups: an a-priori clinical model based on at least 2 msec lag of transient response latencies behind sustained response latencies and a statistical model derived from the sample data.
Both models discriminated between mTBI and non-mTBI groups significantly above chance (with 76 and 86% accuracy, respectively). In the final statistical model those with mean 8 VSG response latencies > 118.65 msec OR mean 16 VSG latencies > 112.60 msec AND mean 16 VSG amplitudes < 14.75mV were classified as having had a history of concussion. The resultant ROC curve for this model had excellent discrimination between the mTBI and non-mTBI (ROCAUC=0.857; p<0.01) groups with sensitivity of 0.92 and specificity of 0.80.
The results suggest significant magnocellular deficits in individuals with CI and a history of mTBI. Since the a-priori clinical model also had good discrimination between the groups, magnocellular deficits could become a robust electrophysiological marker of concussion history in patients with CI.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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