Abstract
Objectives: The purpose was to quantitatively examine brain structures using 7 Tesla MRI in the presence of visual loss caused by retinitis pigmentosa (RP) related to retinitis pigmentosa GTPase regulator (RPGR) gene pathogenic variants. Methods: Twelve male patients with RP (mean visual acuity 0.4) related to confirmed RPGR pathogenic variants and fifteen healthy volunteers were examined with 7 Tesla MRI of the brain. Measures of the lateral geniculate nucleus (LGN) volume were performed manually by three independent investigators (radiologists) using ITK-SNAP (Insight Segmentation and Registration Toolkit) software. Other brain structures were evaluated using the open-source automated software package FreeSurfer. Prior to the 7 Tesla MRI, patients underwent an ophthalmic examination and a 1.5 Tesla MRI. Results: The mean LGN volume (right-100 mm3, left-96 mm3) and left lingual gyrus volume (6162 mm3) were significantly lower in RPGR patients in comparison to the control group (129 mm3, 125 mm3, and 7310 mm3, respectively), whilst some brain regions related to other sensory information such as the left isthmus cingulate (3690 mm3) and entorhinal cortex (right-1564 mm3, left 1734 mm3) were significantly or almost significantly higher in the RPGR group than in the control group (2682 mm3, 960 mm3, and 1030 mm3, respectively). Moreover, compared to the control group, the RPGR group's thalamus-to-LGN ratio was substantially higher. Conclusions: The use of the 7 Tesla MRI revealed numerous structural abnormalities of the visual pathway in patients with RPGR-related RP. The reorganization of the structures of the brain demonstrated in patients with RPGR-related RP reveals a certain degree of plasticity in response to visual loss. These findings may help improve diagnostic and therapeutic strategies for RP patients and contribute to the development of precision medicine.