What are the signs and symptoms of focal muscular atrophy (FMA)?

Updated: Feb 20, 2018
  • Author: Sridharan Ramaratnam, MD, MBBS; Chief Editor: Helmi L Lutsep, MD  more...
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Focal muscular atrophy (FMA) has various causes and, hence, various signs and symptoms.

  • Muscle wasting is probably the presenting symptom when the onset is insidious (see images below). Weakness may not be a primary symptom in these patients.

    A man with neuralgic amyotrophy presenting with wa A man with neuralgic amyotrophy presenting with wasting of deltoids involving the right side more than the left.
    A middle-aged man with (atypical) anterior horn ce A middle-aged man with (atypical) anterior horn cell disease presenting with wasting of the right quadriceps.
  • Muscle weakness occurs when the onset is more abrupt.

    • Distal weakness in the upper limbs may manifest with the following difficulties: opening jars, holding tightly to a pencil, typing, fingering a musical instrument, buttoning a shirt, or tying shoelaces.

    • Proximal weakness in upper limbs may manifest with difficulty in raising the arms or reaching for high objects.

    • Weakness of lower limb muscles may result in the following difficulties: walking, climbing stairs, walking on uneven surfaces, and stumbling over small objects.

  • Muscle twitching (fasciculations) occurs when anterior horn cells or proximal roots are involved.

  • Muscle cramps, commonly experienced in the gastrocnemius muscles, are characterized by sudden, brief, intense muscle pain; a strong, hard, palpable muscular contraction; and immediate relief by stretching the muscle.

  • Sensory symptoms (eg, pain, numbness, tingling or burning sensation) suggest involvement of roots, plexi, or peripheral nerves.

  • Trophic changes may be seen when small fibers of the peripheral nerve are involved or a defect in pain, temperature, or joint-position sensation is noted.

  • Systemic symptoms suggest diabetes, arthritis, articular injury, collagenosis, malignancy, abuse of prescription or nonprescription drugs, or intravenous (IV) drug abuse.

  • Geographic preponderances of monomelic amyotrophy, polio, and leprous neuropathy have been recognized. Consider such diseases in immigrants from the appropriate geographic regions.

  • A history of affected family members may suggest genetic disorders such as spinal muscle atrophy (SMA) or a familial clustering due to infectious disease or environmental mechanisms.

  • Past history of polio, trauma, radiation, electrical injury, malignancy, or lymphoma should suggest an etiology for FMA.

  • Occupational exposure to toxins may lead to FMA.

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