Trigeminal neuralgia is a severe chronic pain condition with a major impact on quality of life. Although Gamma Knife radiosurgery is an established treatment for pharmacoresistant trigeminal neuralgia, its mechanisms of action and the temporal dynamics of clinical response remain incompletely understood.

This prospective longitudinal study aims to investigate changes in brain functional connectivity using resting-state functional magnetic resonance imaging (rs-fMRI) in patients with classical trigeminal neuralgia treated with Gamma Knife radiosurgery. Participants will undergo rs-fMRI examinations before treatment and at 1 month, 3 months, and 12 months after radiosurgery.

Functional connectivity patterns will be analyzed over time and correlated with clinical outcomes, including pain intensity and treatment response. Imaging data will be compared with those from a cohort of age- and sex-matched healthy volunteers. The study does not modify standard clinical care; only additional non-invasive MRI examinations without contrast injection are performed for research purposes.

Inclusion Criteria:

• Adults aged 18 to 73 years
• Diagnosis of classical trigeminal neuralgia confirmed by an experienced neurologist
• Unilateral facial pain with a normal neurological examination
• Pharmacoresistant trigeminal neuralgia, defined as failure of at least two appropriate medical treatments, intolerance to medication, or recurrence despite adequate treatment
• Indication for Gamma Knife radiosurgery as part of standard clinical care
• Affiliation to a social security or health insurance system
• Ability to understand the study information and provide written informed consent

Exclusion Criteria:

• Diagnostic uncertainty or secondary/idiopathic trigeminal neuralgia
• Previous surgical or radiosurgical treatment for trigeminal neuralgia
• Participation in another interventional clinical study at the time of inclusion
• Individuals belonging to protected populations as defined by applicable regulations (including minors, adults under legal protection, persons deprived of liberty, pregnant or breastfeeding women)
• Inability to understand the French language
• Contraindication to 3 Tesla MRI, including claustrophobia, presence of pacemaker, defibrillator, metallic prosthesis, or any MRI-incompatible device or foreign body
• Residence distance incompatible with the required follow-up schedule