Scientists track how a single gene causes two brain diseases

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

* INCLUSION CRITERIA: Patients will be included if they: * Are age 18 or older * Have a confirmed repeat expansion in the C9ORF72 gene EXCLUSION CRITERIA: Patients will be excluded if they * have other major neurological or medical diseases that may cause progressive weakness or cognitive dysfunction, such as structural brain or spinal cord disease, metabolic diseases, paraneoplastic syndromes, hereditary diseases, infectious diseases, peripheral neuropathy or radiculopathy or other significant neurological abnormalities. * require daytime ventilator support at the time of study entry * are unable to travel to NIH at the time of study entry * are unwilling to have follow-up visits * are unable to understand or decline to sign the Informed Consent at the time of study entry. Participants can remain in the study (with DPA consent and participant assent) if they lose consent capacity. * have pacemakers or other implanted electrical devices, brain stimulators, dental implants, aneurysm clips (metal clips on the wall of a large artery), metallic prostheses (including metal pins and rods, heart valves, and cochlear implants), permanent eyeliner, implanted delivery pumps, or shrapnel fragments, metal fragments in the eye) that exclude magnetic resonance imaging * have unstable medical conditions that, in the opinion of the investigators, prevent safe participation in this study. * are participating in experimental treatment trials at the time of study entry or plan such participation within 6 months of entry. Patients will not be excluded if they are receiving standard care medications for treatment of ALS and its symptoms, or are participating in non-treatment clinical research studies. Patients will be permitted to participate in experimental treatment trials after the 6 month follow-up visit. Patients with pacemakers or other implanted electrical devices, brain stimulators, dental implants, aneurysm clips (metal clips on the wall of a large artery), metallic prostheses (including metal pins and rods, heart valves, and cochlear implants), permanent eyeliner, implanted delivery pumps, or shrapnel fragments, metal fragments in the eye) will not be excluded but will not undergo magnetic resonance imaging or transcranial magnetic stimulation.