- Are 18 years or older
- Have a confirmed mutation in the gene C9ORF72
- Have symptoms of ALS or FTD, or are family members who are carriers of the C9ORF72 gene mutation
- Have other major neurological or medical diseases that may cause progressive weakness or cognitive dysfunction
- Require daytime ventilator support at the time of study entry
- Are unable to understand or decline to sign the Informed Consent at the time of study entry. Participants can remain in the study (with Durable Power of Attorney (DPA) consent and participant assent) if they lose consent capacity.
- Have pacemakers or other implanted electrical devices that make having magnetic resonance imaging unsafe
- 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
Eligible persons 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. Participants will be permitted to take part in experimental treatment trials after the six month follow-up visit.