An evaluation of a patient’s history will guide the neurologist to consider certain areas of the nervous system and certain disorders.
Symptoms of dysfunction of the neuromuscular system include those governed by sensory nerves or those that arise from impairment of the motor unit, the nerve fibers and muscle fibers that each fiber supplies.
Disorders of the nerve include inherited conditions, e.g. Charcot-Marie-Tooth, metabolic disorders that impair nerve function, e.g. diabetic neuropathy, and inflammatory conditions of the nerve, e.g. Guillain-Barre syndrome or chronic inflammatory demyelinating polyneuropathy.
Disorders of the motor unit include degenerative diseases, for example amyotrophic lateral sclerosis (ALS or Lou Gehrig disease) and inherited conditions like Kennedy disease and spinal muscular atrophy, where there is degeneration of the nerve cells that activate the muscle.
A specialized junction exists where the nerve meets the muscle, the neuromuscular junction. The most common ailment that affects this site is myasthenia gravis, an immune mediated disorder.
There are primary diseases of the muscle; some are inherited such as muscular dystrophy, mitochondrial disorders and disorders of energy production from specific enzyme defects; others are inflammatory such as polymyositis or dermatomyositis. Research continues to identify specific proteins causing some of the inherited disorders, and it is hoped that treatments for many of these illnesses will emerge through this research.
Specialized testing, nerve conduction studies and electromyography may be used to identify the disorder. Nerve conduction studies measure the response to small electric stimuli given to the skin or peripheral nerve underlying the skin. The neurologist can measure how quickly the nerve impulses travel along the course of the nerve and measure the amplitude of these responses and compare these to normal values to help diagnose the nature of the trouble. Electromyography utilizes a small needle electrode placed through the skin into the muscle. This electrode measures the electrical activity generated by muscle fibers supplied by individual nerve fibers; the signal can be displayed on a screen and heard on a loudspeaker. These studies can distinguish normal findings from those caused by disorder of the nerve or muscle itself.
- Progressive muscle wasting
- Difficulty with speech
- Difficulty swallowing
- Double vision
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- Online Mendelian Inheritance in Man
- Muscular Dystrophy Association
- ALS Association
- Myasthenia Gravis Foundation of America