Study of Inherited Neurological Disorders

* Participants include those with inherited neurological conditions based on the training and research needs of the Neurogenetics Branch program. There is no logical limit; however, the total number of participants that can be enrolled in the protocol will be restricted. No more than 3,500 participants with either diagnosed or undiagnosed neurological conditions and their unaffected relatives will be enrolled in this evaluation and diagnostic protocol. INCLUSION CRITERIA: Participants will be eligible if they: * Have either a known or suspected, inherited neurological disease, OR are an unaffected relative (first-, second-, third, or higher degree relative) of a participant with a genetic neurological disease. * Have the ability to understand and sign an informed consent or have a parent/legal guardian to do so if they are minor children or a legal guardian to provide consent for adults without consent capacity. * Aged 2 years and above. EXCLUSION CRITERIA: Participants will not be eligible if they: -Have a systemic disease that compromises the ability to provide adequate neurologic examination or diagnosis. An example of this would be a contagious disease that would compromise our ability to do an adequate neurological exam.