Synonyms:
a.k.a. acute quadriplegic myopathy
Diagnosis:
This is a clinical diagnosis supported by exclusion of other causes. Usually it does not require biopsy but often it is used in cases of uncertainty
Clinical features:
All limbs, diaphragmatic and intercostal weakness,
Occurs in severe illness +/-sepsis, +/-steroids, +/-neuromuscular blocking agents
Findings on investigations:
+CK normal or moderately raised
+EMG myopathic pattern +reduced excitability to direct muscle stimulation
+NCS normal, or slightly reduced CMAP, to exclude Critical care neuropathy
+RNST to exclude Myasthenia Gravis
+Muscle Biopsy:
HE: Nonspecific changes, fibre atrophy especially type 2, necrosis may occur
+EM loss of myosin (absent A bands= thick bands), preserved Z-bands and thin filaments
Immunohistochemistry: myosin heavy chain: reduced