MUSCULAR ATROPHY
MUSCULAR ATROPHY: Excerpt from Differential Diagnosis in Primary Care
This symptom is developed using both anatomy and
physiology. Atrophy of any muscle may develop in seven ways.
-
Lack of use of the muscle
- Malnutrition or increased body metabolism
- Primary muscle disease
- Myoneural junction disease
- Peripheral nerve disease
- Nerve root disease
- Spinal cord disease
When recalling the differential diagnosis of muscular atrophy, think of
these seven factors and the causes will unfold.
-
Lack of use of the muscle. In focal or generalized bone or joint
disease there is diminished use of the extremity or part involved, so the
muscles atrophy. “Disuse” atrophy may also occur in compensation neurosis,
hysteria, depression, and in many central nervous system diseases in which
motivation is gone.
- Malnutrition or body hypermetabolism. Starvation causes diffuse
muscular wasting. Diffuse muscular wasting also occurs in anything that
speeds up body metabolism, including hyperthyroidism, metastatic carcinoma
and other diffuse neoplasms, chronic inflammatory conditions such as
rheumatoid arthritis (RA) and collagen disease, and chronic fever of any
cause.
- Primary muscle disease. Muscular dystrophy, dermatomyositis,
trichinosis, and McArdle syndrome should be considered here.
- Myoneural junction. This category makes one think of myasthenia
gravis.
- Peripheral nerve disease. Diabetic neuropathy and the neuropathy
from lead, arsenic, and other toxins should be considered here.
Periarteritis nodosa and trauma to the nerve may give an asymmetric
neuritis. Hereditary neuropathies such as Charcot–Marie–Tooth disease and
Dejerine–Sottas hereditary hypertrophic neuritis are also considered here.
Porphyria is another cause to recall in this category.
- Nerve root disease. Spinal column disorders that compress the
root include fractures, herniated disks, spondylolisthesis, tuberculosis,
metastatic tumors, and multiple myelomas.
- Spinal cord disease. The degenerative diseases such as
amyotrophic lateral sclerosis, progressive muscular atrophy, and
syringomyelia must be considered here. In addition, poliomyelitis,
transverse myelitis of various areas, anterior spinal artery occlusion,
infectious polyneuritis, and spinal cord tumors must be recalled.
Approach to the Diagnosis
Focal atrophy of a muscle often means a damaged peripheral nerve or
root. If there are visible fasciculations, a lesion of the spinal cord or
root is most likely. Electromyography will determine which portion of the
nerve is affected. It will also be helpful in diagnosing muscle disease.
Muscle biopsy is valuable in ruling out trichinosis, dermatomyositis,
or muscular dystrophy. If there are
fasciculations, a spine x-ray, spinal tap, and myelography or MRI may be
necessary to establish the diagnosis. Sedimentation rate, CRP, RA titer,
ANA, and tuberculin tests may be necessary.
Other Useful Tests
-
Serum protein electrophoresis (collagen disease, multiple
myeloma)
- Muscle enzyme tests (muscular dystrophy, dermatomyositis)
- 24-hour urine creatine and creatinine levels (muscular
dystrophy)
- Acetylcholine receptor antibody titer (myasthenia gravis)
- Thyroid function tests (hypothyroid myopathy)
- Glucose tolerance test (diabetic neuropathy)
Pictures
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins MD, FACP
- Year of Publication: 2007
- Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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