Study of Electrical Impedance Myography (EIM) in ALS

Early ALS Inclusion Criteria: * Sporadic or familial ALS (as defined by revised El Escorial criteria) * Onset of weakness or spasticity due to ALS ≤ 36 months prior to the Screening/Baseline Visit. * Slow vital capacity (SVC) ≥60% of predicted for gender, height, and age Early ALS Exclusion Criteria: \- The presence of unstable psychiatric disease, cognitive impairment, or dementia that would impair ability of the subject to provide informed consent, or a history of active substance abuse within the prior year. ALS Disease Mimics Inclusion Criteria: \- Diagnosis of one of the following: a. Pure Lower Motor Neuron Disease (LMND) mimics: i. Multi-focal motor neuropathy ii. Autoimmune motor neuropathy iii. Cervical or lumbosacral radiculopathies with weakness involving more than one extremity or more than a single myotome if restricted to one extremity. iv. Multiple peripheral mononeuropathies with clinical weakness v. Charcot-Marie-Tooth Disease vi. Any condition that produces generalized or localized weakness without concomitant sensory symptoms, including myasthenia gravis or myopathy, that the evaluating physician deems mimics ALS. b. Pure Upper Motor Neuron Disease (UMND) mimics: i. Cervical myelopathy ii. Multiple sclerosis iii. Hereditary spastic paraparesis ALS Disease Mimics Exclusion Criteria: * Diagnosis of possible, probable, probable-laboratory supported, or definite ALS * Presence of positive family history of ALS. * The presence of unstable psychiatric disease, cognitive impairment, or dementia that would impair ability of the subject to provide informed consent, or a history of active substance abuse within the prior year. Healthy Volunteer Inclusion Criteria: \- Absence of a known neurological disorder. Healthy Volunteer Exclusion Criteria: * History of ALS, myopathy, neuropathy, ALS mimic disorder or other neurodegenerative disease. * Presence of positive family history of ALS. * The presence of unstable psychiatric disease, cognitive impairment, or dementia that would impair ability of the subject to provide informed consent, or a history of active substance abuse within the prior year. \*Please note that this is not a complete listing on all eligibility criteria.\*