This is an important clinical distinction to make, but may not always be easy.
Myopathy (Break down or inflammation of muscle)
- Tends to affect (large) muscle groups (i.e Hips, Shoulders) causing proximal weakness.
- There will be a lack of sensory deficits (but they may complain of myalgias or tenderness to palpation (if myositis)).
- Reflexes should be intact and no fasciculations should be seen.
Neuropathy (Damage to your peripheral nerves)
- Tends to affect distal muscles first in a length dependent distribution.
- Typically will have sensory findings (i.e paresthesia, dysesthesia).
- May have loss of reflexes (i.e Lower Motor Neuron pathology).
- Fasciculations may be present.
NOTE: Tests such as CK and NCS/EMG can help delineate the two etiologies should the clinical picture not be clear.
REFERENCES
- Saguil A. Evaluation of the patient with muscle weakness. Am Fam Physician. 2005 Apr 1;71(7):1327-36.
- Paganoni, S., Amato, A. Electrodiagnostic Evaluation of Myopathies. Phys Med Rehabil Clin N Am. 24 (2013) 193–207.
- Chawla, J. Stepwise Approach to Myopathy in Systemic Disease. Front Neurol. 2011; 2: 49.