This trial is studying Electrical Impedance Myography (EIM) for measuring muscle health. The trial is studying people with Amyotrophic Lateral Sclerosis (ALS), other neuromuscular diseases, and healthy volunteers to see if the EIM device can measure disease in muscle tissue.

This is a multicenter, 9-month study evaluating the effectiveness of electrical impedance myography (EIM) as a diagnostic and disease-tracking tool. In addition, the following will be studied:

1. Determine EIM device's ability to discriminate between ALS and "look-alike" non-fatal, motor-predominant syndromes;
2. Track EIM progression over time and determine the best summary EIM measure that could serve as an endpoint in future clinical trials and individual patient care; and,
3. Determine whether EIM progression is predictive of a combined outcome of survival and progression as measured by ALS Functional Rating Scale, Revised (ALSFRS-R), Hand-held Dynamometry (HHD) and Vital Capacity (VC) measures.

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.*

People with ALS People diagnosed with early ALS (possible, probable, probable- laboratory supported or definite ALS according to El Escorial criteria)

Other Neurological Diseases People with a diagnosis of a disease that mimics ALS

Healthy Controls Healthy Volunteers that do not have ALS or another neurological disease that mimics ALS.