July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
When light hurts: Brain-morphometry in concussion photophobia
Author Affiliations & Notes
  • Lora Likova
    Smith-Kettlewell Eye Research Institute, San Francisco, California, United States
  • Christopher W Tyler
    Smith-Kettlewell Eye Research Institute, San Francisco, California, United States
  • Footnotes
    Commercial Relationships   Lora Likova, None; Christopher Tyler, None
  • Footnotes
    Support  CDMRP MR130266 to LL
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 4670. doi:
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      Lora Likova, Christopher W Tyler; When light hurts: Brain-morphometry in concussion photophobia
      . Invest. Ophthalmol. Vis. Sci. 2018;59(9):4670.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : 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.

Methods : 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.

Results : 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.

Conclusions : 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.

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