The term myopathy means a primary disorder of muscle causing wasting and/or weakness in the absence of sensory abnormalities. Clinically, myopathic processes need to be differentiated from neuropathies, particularly anterior horn cell diseases and motor neuropathies, and neuromuscular junction disorders. Generally in primary muscle disease there are no fasciculations, reflexes are lost late, and phenomena such as (peripheral) fatigue and facilitation do not occur.
Myopathies may be subdivided according to the clinical pattern of weakness, and/or their etiology:
Affecting shoulder abductors, hip flexors predominantly: Inflammatory: polymyositis, dermatomyositis
Progressive muscular dystrophies: Duchenne, Becker, limbgirdle, facioscapulohumeral (FSH)
Metabolic: acid-maltase deficiency; thyroid dysfunction, Cushing’s syndrome
Nonmetastatic feature of malignant disease.
An unusual pattern for myopathy, which needs to be differentiated from distal polyneuropathy:
Myotonic dystrophy Miyoshi dystrophy Desmin myopathy.
- Bulbar palsy (q.v.).
- Facial paresis (q.v.).
- Diaphragm weakness:
Acid-maltase deficiency Acute polymyositis Neuralgic amyotrophy.
- Axial myopathy:
Camptocormia ("bent spine syndrome") Dropped head syndrome.
Barnes PRJ, Hilton-Jones D, Dalakas MC, Palace JA, Rose MR.
Myopathy in clinical practice. London: Martin Dunitz, 2003
Mandler RN. Myopathy. In: Biller J (ed.). Practical neurology (2nd edition). Philadelphia: Lippincott Williams & Wilkins, 2002: 623-641