The cognitive disorders of adult forms of myotonic dystrophies type 1 are heterogeneous (impairment of executive functions, visio construction and theory of the mind, which can progress to the stage of dementia). Nevertheless, patients have very different degrees of cognitive impairment. Expansion of CTG triplets disrupts the alternative splicing of mRNAs of various proteins, including the insulin receptor and Tau protein. Type 2 diabetes, associated with peripheral insulin resistance, is therefore common in this pathology.

Type 2 diabetes,could to explain the cognitive impairment of patients, through the accelerated development of brain lesions (especially tauopathy and cerebral atrophy).

Inclusion Criteria:

• Molecularly proven type 1 myotonic dystrophy
• Voluntary, having given informed consent
• Socially insured patient
• Patient willing to comply with all study procedures and duration (3 hours + MRI 35 minutes)
• Patient insured under the French social security system
• Signed consent form

Exclusion Criteria:

• Neurological history other than neuropathy: epilepsy, stroke, dementia
• Pregnancy or breastfeeding or woman of childbearing age without effective contraception (a pregnancy test will be done)
• Contra indication to MRI
• Person under guardianship or curators
• Persons of full age deprived of their liberties by a judicial or administrative decision
• Major comorbidity considered as a contraindication by the investigator (cancer, unstable angina, etc.).

Patients with DM type 1 monitored annually by the Neuromuscular Disease Reference Centre