Is Photophobia Linked to the Structure of the Visual Thalamus? A MRI Morphometric Study

Background/Objectives: Photophobia is one of the most prevalent migraine symptoms, both during and outside of attacks, but its pathogenesis 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. Methods: Twenty patients with episodic migraine without aura (MO) and 20 healthy controls (HCs) underwent high-resolution T1-weighted magnetic resonance imaging and comprehensive ophthalmological assessment. Patients were scanned interictally and none of them were under preventive therapy. Volumetric segmentation encompassed the whole thalamus and the lateral geniculate nuclei and pulvinar subregions. Interictal photophobia was evaluated using a visual analogue scale, ranging from 0 to 10. All thalamic and subregion volumes were used as independent variables and photophobia levels as dependent variables in general linear models. The model considered gender as a factor and total intracranial volume as a covariate. Results: No statistically significant differences were observed in the overall thalamic volume or in any of its subregions between MO patients and healthy controls (punc > 0.05). No relationships emerged between thalamic volumes and interictal subjective photophobia levels (p > 0.05). Conclusions: Our results suggest that photophobia is not linked to thalamic macroscopic volumes alterations during the interictal phase of MO patients. Further research is needed to determine whether these results could be extended to patients with migraine with aura or during other phases of the migraine cycle.