Purchase this article with an account.
Lora Likova, Christopher W Tyler; When light hurts: Brain-morphometry in concussion photophobia. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4670.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
A well-known consequence of diffuse or, mild traumatic brain injury (mTBI) is the development of light-induced pain, known as photophobia or, better - ‘photalgia’, which often leads to prolonged debilitation; the mechanism of the sensitizing to light, however, although intensively studied, is still unclear. Based on brain imaging and computational modeling findings, we propose the brainstem-damage hypothesis that the tissue edema (swelling) or shrinkage - which are a common feature in mTBI - might sensitize the trigeminal nucleus to sources of irritation activated by bright light. We tested this hypothesis by means of Tensor-Based Morphometry (TBM) of the human brainstem.
The participants were mTBI patients i) with mild and ii) with severe photalgia or iii) without photalgia, and iv) non-TBI controls. Each participant underwent high-resolution Magnetic Resonance Imaging to determine the configuration of the brainstem by TBM, for comparison across the participant groups. The TBM was based on a T1-weighted structural sequence acquired with cubic voxels with 0.8 mm edges for each participant. The T1 volume was processed with the FIRST tools from FSL, which provided an affine registration to a standard brain metric (the MNI152), and generated triangular mesh representation of the brainstem. Data were visualized as a rendering of the surface of the control group colored by the magnitude of the difference tensors across vertices.
The TBM revealed statistically significant deviations (p < 0.05, corrected) in the brainstem morphology of all mTBI groups. Furthermore, there was a pronounced difference between the patterns of average swelling and shrinkage for the non-photalgic and photalgic mTBI groups. mTBI without photalgia showed bilateral expansion at the pontine/medulla junction, while mTBI with photalgia showed a band of mid-pontine shrinkage, consistent with deterioration of the trigeminal complex.
These results support the hypothesis that mTBI affects the trigeminal complex of the brainstem. Furthermore, the specific pattern of mid-pontine shrinkage exhibited for photalgic mTBI may represent the morphological substrate of the photalgic sensitization to light.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
This PDF is available to Subscribers Only