Visual-Evoked Potential (VEP) to Measure Visual Attention Objectively in Mild Traumatic Brain Injury (mTBI)

Abstract

Purpose: Currently, there are no objective clinical techniques available to assess visual attention (VA) in the mild traumatic brain injury (mTBI) population. The hypothesis was that the visual-evoked potential (VEP) would be able to detect, assess, and differentiate objectively VA deficits in the mTBI population. The purpose of the present study was to quantify VA objectively using the VEP in those having mTBI, both with and without a self-reported VA deficit.

Methods: Subjects were comprised of 16 adults with mTBI: 11 with a VA deficit (mean=38 years), and 5 without (mean=29.8 years). The Diopsys^TM NOVA-TR VEP system was used to measure attention-related, alpha-band power (8-13 Hz) under three conditions: 1) pattern VEP eyes open (EO); 2) eyes-closed (EC); and 3) eyes-closed number counting (ECNC). The VEP alpha attenuation ratios (ARs=EC÷EO and ECNC÷EC) were calculated for both the individual and combined alpha band frequencies. The normative alpha AR values for EC÷EO and ECNC÷EC are >2.00 and <1.00, respectively. The objective results were compared to two subjective tests of visual and general attention [i.e., the Visual Search and Attention Test (VSAT) and the Adult ADHD Self-Report Scale (ASRS)], respectively.

Results: There was a significant effect of ARs (EC÷EO and ECNC÷EC) on each alpha frequency (p<0.05). The two ARs for individual alpha frequency were abnormal (<2.00 and >1.00), and normal (>2.00 and <1.00), in those with and without a VA deficit, respectively. Similar results were found for the combined alpha ARs in both groups. The ASRS mean score was abnormal (mean=22.8; range=17 to 28) and normal (mean=12.4; range=8 to 16) in those with and without a VA deficit, respectively. The ASRS scores were significantly higher in those with a VA deficit (p<0.05). In contrast, the VSAT percentile scores were normal and non-significantly different (p >0.05) in both mTBI groups. Lastly, the ARs were significantly correlated with the ASRS (p<0.05), but not with VSAT (p>0.05), test scores.

Conclusions: The objective VEP (ARs) and subjective (ASRS) tests differentiated between those having mTBI with versus without a VA deficit. The ASRS questionnaire was an excellent predictor (100%) of a VA deficit in the mTBI population. The proposed VEP test can be used in the clinic to quantitatively detect and assess objectively and reliably presence of a VA deficit in the mTBI population.