Lower motor neuron signs include atrophy and fasciculations. No loss of anal sphincter tone occurs. Cardiac and smooth muscle are not involved. The course is progressive, and initial symptoms primarily are those of weakness. Weakness often is asymmetric and begins in the legs, arms, or oropharyngeal muscles with approximately equal frequency.
Masticatory weakness occurs late.
Ultimately, weakness becomes symmetrical. Ocular musculature is never involved. Muscle atrophy and weight loss almost always are recognized by the time the patient seeks medical treatment. Fasciculations may be quite widespread and active. Surprisingly, the patient often ignores this symptom.