Is photophobia associated with the structure of the visual thalamus? A MRI morphometric study

Photophobia is a common migraine symptom, but its cause is unknown. The posterior thalamic nuclei may directly affect ambient light discomfort. This study examined the link between photophobia and the structure and morphometry of the thalamus and its subregions, including the lateral geniculate nuclei and pulvinar subnuclei.

Twenty episodic migraine patients without aura (MO) and 20 healthy controls (HCs) underwent high-resolution T1-weighted magnetic resonance imaging, diffusion tensor imaging (DTI), and full ophthalmological assessment. Scans were acquired interictally, with all patients off preventive therapy. Volumetric segmentation included the whole thalamus, lateral geniculate nuclei, and pulvinar subregions. Photophobia was rated from 0 to 10 using a visual analogue scale. Thalamic and subregion volumes served as dependent variables, while photophobia scores were independent variables in a general linear model (GLM). Bilateral thalamic DTI metrics were analyzed for relationships with volumes and photophobia scores using GLMs.

No statistically significant differences were observed in the overall thalamic volume or in any of its subregions and DTI metrics between MO patients and HCs (p > 0.05). No relationships emerged between thalamic volumes, DTI metrics, and interictal subjective photophobia scores (p > 0.05).

Our results suggest a lack of association between photophobia and thalamic macro- and microstructural measures in MO patients during the interictal phase, with no significant structural or microstructural correlates identified. Further research is needed to determine whether these negative results could be extended to patients with migraine with aura or during other phases of the migraine cycle.