HISTORY. Because the first evidence of the disease is often gradually developing asymmetrical weakness in one limb, establish a recent history of muscle weakness or involuntary contractions (fasciculations) of the muscles, especially in the feet and hands. Ask whether the patient has lost weight, experienced difficulty in chewing or swallowing, or if he or she has been drooling. Elicit a history of breathing difficulties or choking. Ask if the patient has experienced any crying spells or periods of inappropriate laughter, which can be caused by progressive bulbar palsy (degeneration of upper motor neurons in the medulla oblongata).

PHYSICAL EXAMINATION. Determine how the disease is affecting the patient's functioning and ability to carry out the activities of daily living. Assess for the characteristic atrophic changes such as weakness or fasciculation in the muscles of the forearms, hands, and legs. One side of the body may have more muscle involvement than the other. Assess the patient's respiratory status, noting rate and pattern and the patient's breath sounds.

As the disease progresses, muscle weakness that began asymmetrically becomes symmetrical. Muscles of chewing, swallowing, and tongue movement are affected. Note facial symmetry,

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the presence or absence of a gag reflex, slurred speech, and the ability to swallow. Note any tendency to drool or any tongue tremors.

PSYCHOSOCIAL. The patient with ALS is confronted with a progressive fatal illness. Because mental capacity is not affected by this disease, the patient remains alert even in the late stages of the disease. Patients with ALS usually experience depression and need a great deal of emotional support, as do their families and significant others.

Diagnostic Highlights

General Comments: Because ALS is currently untreatable, it is essential that other potential causes of motor neuron dysfunction be excluded by diagnostic testing.


Normal Result

Abnormality with Condition


Needle electromyography (EMG) and nerve conduction studies

Normal conduction velocity 40-80 m/sec after a nerve is stimulated with normal muscle action potentials

Diffuse denervation signs, decreased amplitude of compound muscle action potentials, and normal conduction velocities

Rules out other muscle diseases; often reflects a decrease in motor units of the affected muscles

Other Tests: Muscle biopsy; cerebrospinal fluid analysis; pulmonary function tests; computed tomography (CT) scan; magnetic resonance imaging (MRI); other conduction studies. Serum protein immunoelectrophoresis, HIV testing, and Lyme disease serology to rule out other disorders.

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