Photosensitivity Is Associated with Chronic Pain following Traumatic Brain Injury

Abstract

Individuals with a history of traumatic brain injury (TBI) report increased rates of chronic pain. Photosensitivity is also a common chronic symptom following TBI and is prevalent among other types of chronic pain. The aim of this study was to better understand the relationship between chronic pain, pain-related disability, and photosensitivity in a TBI population. We quantified participants' visual photosensitivity thresholds (VPT) using an Ocular Photosensitivity Analyzer and measured pressure-pain sensitivity using pressure algometry. Participants also completed a battery of self-report measures related to chronic pain, TBI history, and mental health. A total of 395 participants completed testing, with 233 reporting a history of TBI. The TBI group was divided into 120 symptomatic TBI participants (s-TBI), and 113 asymptomatic TBI participants (a-TBI) based on their Neurobehavioral Symptom Inventory (NSI) scores. Participants in the s-TBI group scored significantly higher on self-reported chronic pain measures compared with a-TBI and no-TBI participants, including the Symptom Impact Questionnaire Revised (SIQR; p < 0.001) and the Michigan Body Map (MBM; p < 0.001). Despite differences in chronic pain complaints, groups displayed similar pressure-pain thresholds (p = 0.270). Additionally, s-TBI participants were more sensitive to light (lower VPT, p < 0.001), and VPT was correlated with SIQR scores across all participants (R = -0.452, p < 0.001). These data demonstrate that photosensitivity is associated with self-reported chronic pain and disability in individuals with chronic TBI symptomatology. Photosensitivity could therefore serve as a simple, more highly quantitative marker of high-impact chronic pain after TBI.

Keywords: chronic pain; concussion; hypersensitivity; photosensitivity, polytrauma triad; traumatic brain injury.

FIG. 1.

Distribution of Neurobehavioral Symptom Inventory (NSI) scores in traumatic brain injury (TBI) participants. (A) Raincloud plots illustrating the distribution on NSI scores across TBI severity (n = 231, two participants were discarded for missing data). Whisker plots mark the lowest/highest observations, upper/lower quartiles, and median scores within each group, while raincloud plot displays probability density. All three TBI groups scored significantly greater than the no-TBI group (p < 0.001, n = 162) but did not differ from one another. (B) Frequency histogram depicting the range of NSI scores in participants with confirmed TBI. Dashed lines mark lower quartile, median, and upper quartile scores. Due to the skewness of the distribution, TBI participants were categorized as symptomatic or asymptotic using a median split. NSI, Neurobehavioral Symptom Inventory, range 0-80.

FIG. 2.

Symptomatic traumatic brain injury (TBI) group reports more intense and more widespread chronic pain. (A) Participants in the TBI group reported significantly higher Symptom Impact Questionnaire Revised (SIQR) scores than the no-TBI group (no-TBI n = 162, TBI n = 233; *** p < 0.001). (B) The TBI group also endorsed significantly more body areas affected by chronic pain (***p < 0.001). When broken down into symptomatic (s-TBI) and asymptomatic (a-TBI) groups, we found the s-TBI group scored significantly higher on the SIQR (C) and the MBM (D) than both the a-TBI and no-TBI groups. The no-TBI and a-TBI groups did not significantly differ on either measure (SIQR, p = 0.061; MBM, p = 0.985). Due to demographic differences across groups, sex was used as a covariate in these analyses. Data are presented as mean ± standard error.

FIG. 3.

No differences in pressure pain levels between traumatic brain injury (TBI) groups Despite the TBI group reporting significantly higher levels of chronic pain, we found no differences between groups on either experimental pressure-pain thresholds (A; p = 0.224) or pressure-pain tolerance levels (B; p = 0.300). This was also true when we analyzed a-TBI and s-TBI groups separately on both measures (C; p = 0.503; D, p = 0.490). Due to demographic differences across groups, sex was used as a covariate in these analyses. Data are presented as mean ± standard error.

FIG. 4.

Symptomatic traumatic brain injury (s-TBI) participants have lower light-evoked discomfort levels. (A) TBI participants had significantly lower visual photosensitivity thresholds compared with the no-TBI group (***p < 0.001). (B) This difference was almost entirely due to the s-TBI participants, which were significantly lower compared with both the no-TBI group and the aymptomatic TBI (a-TBI) group (***p < 0.001). The a-TBI participants were not significantly different from the no-TBI participants (p = 0.670). Due to demographic differences across groups, sex was used as a covariate in these analyses. Data are presented as mean ± standard error.

FIG. 5.

Strong correlation between photosensitivity and chronic pain complaints. (A) Visual photosensitivity threshold (VPT) levels were strongly correlated with Symptom Impact Questionnaire Revised (SIQR) scores across all participants, regardless of traumatic brain injury (TBI) status (black; R = -0.447, p < 0.001). (B) When broken down by group, we found that no-TBI participants (green; R = −0.379, p < 0.001), s-TBI participants (purple; R = −0.306, p < 0.001) and a-TBI participants (orange; a-TBI: R = −0.258; p = 0.007) all displayed strong negative correlations between VPT and SIQR scores, and these did not differ statistically from one another.

FIG. 6.

Radar plot depicting self-report and behavioral scores between groups. Points farther out from the center represent higher severity and high (worse) scores. The symptomatic TBI (s-TBI) group has the highest severity in all measures, except for pressure-pain threshold and tolerance levels. VPT, visual photosensitivity threshold; SIQR Symptom Impact Questionnaire Revised scores (chronic pain); SI, Insomnia Severity Index scores (sleep disurbances); WHODAS, World Health Organization Disability Assessment Schedule 2.0 scores (disability); PCL-5 Post-Traumatic Stress Disorder (PTSD) Checklist for Diagnostic and Statistical Manual of Mental Disorders-5 scores (PSTD symptoms); PHQ-9, Patient Health Questionnaire 9 scores (depression).