Study of Dopamine and Serotonin Transporters in Patients With Amyotrophic Lateral Sclerosis and Controls

Inclusion Criteria: 1. Patients (men or women) * between 39 (exclusive) and 66 (inclusive) years old * with a sporadic ALS, defined, probable or laboratory possible * with a disease duration between 3 months (inclusive) and 5 years (exclusive) * treated with rilutek at 100 mg/ day since at least 1 month 2. Patients will be assigned in three groups in relation with the clinical phenotypes: * 20 patients without stiffness * 20 patients with pyramidal stiffness (spasticity patients). * 20 patients with mixed stiffness (both spasticity and rigidity). 3. Patients have to be capable of thoroughly understanding the information given; have signed the informed consent form (signature of spouse or family relative or acceptable third party is acceptable if the patient is physically unable to sign). 4. To have social insurance Exclusion Criteria: 1. Patients with a FRONTO temporal dementia (according to NEARY' criteria) 2. Patients with any concomitant life-threatening disease or any disease or impairment likely to interfere with functional assessment; 3. Patients with any major evolving psychiatric disorder or major anxiety disorder according to DSM-IV criteria (APA, 1996) 4. Patients receiving treatments which could interfere with the serotonin or dopamine metabolism 5. Patients with contraindications for the dat-scan and /or ADAM scan 6. Patients with contraindications for the MRI scan. 7. Patients with previous vascular, traumatic or tumoral cerebral lesions making impossible the quantification of the tracer 8. Patients with a cancer within the past 5 9. Patients child bearing, breast feeding or in the second part of their cycle without any efficient contraceptive device or treatment 10. Patients liable not to be co-operative or comply with the trial requirements (as assessed by the investigator), or unable to be reached in the event of an emergency;