Inclusion criteria :  Subjects with first and/or second motor neuron disease, evolving clinically and/or electrically over at least 12 months, not meeting the diagnostic criteria for ALS (revised El Escorial criteria):  Isolated peripheral motor neuron disease (at least one region of the PNM) OR Isolated central motor neuron involvement (at least two areas of the MNC) OR associated involvement of the MNP and MNC but in the presence of an associated pathology responsible for a persistent diagnostic doubt (double narrow cervical and lumbar canal, associated evolving cancer evoking a paraneoplastic syndrome without specific antibody found) Age superior to 18 years Management and follow-up in one of the French ALS centers Patient able to express his non-opposition Affiliation with social security or beneficiary of such a plan  Non-inclusion criteria:  Refusal of the patient Person under a legal protection measure (guardianship, curatorship or safeguard of justice).  Person deprived of liberty by judicial or administrative decision.