Case inclusion criteria  age > or equal to 18 years presence of neurological symptoms compatible with GSP7 (ataxia, spasticity progressive external ophthalmoplegia, and/or optic atrophy) presence of two mutations in the SPG7 gene (= recessive forms of SPG7) or of a single mutation in the simple heterozygous state in the absence of other genetic factors explaining the symptoms  Inclusion criteria for controls  Age > or equal to 18 years Subject who is already undergoing neurosurgical intervention as part of the care pathway for an for an acquired, non-genetic neurological problem (e.g. herniated disc, narrow lumbar canal)  Non-inclusion Criteria of cases  Refusal to sign the written informed consent signed by the patient (or by his representative in case of a patient under guardianship. Patients with specific contraindications for skin biopsy current anticoagulant treatment; any pathologies that may cause a risk of bleeding (e.g. hemophiliacs) Refusal of the patient, of the guardian if necessary, to sign the informed consent to participate in the in the research Not being a beneficiary of a social protection plan Patient deprived of liberty  Non-inclusion Criteria of controls  Patients with a genetic neurological disease or mitochondrial disease Patients with specific contraindications for skin biopsy: current anticoagulant treatment; all pathologies that may cause a risk of bleeding (e.g. hemophilia) Refusal to sign the informed consent to participate in the research Not benefiting from a social protection plan Patient deprived of liberty Patient under guardianship or curatorship