Denervation changes in muscles or denervation myopathy can be observed in a number of settings and results from partial or complete loss of innervation.
There is a wide spectrum of clinical manifestations:
- temporary or permanent
- symptomatic or asymptomatic.
Causes include 2:
- autoimmune disorders
- viral infection
- prolonged nerve compression
- nerve infiltration by neoplasm
- penetrating injury
- Parsonage-Turner syndrome
In the very early stage, muscle signal may be normal.
- the earliest and most pathognomonic feature is increased T2 signal (best seen on a fat-saturated T2WI such as STIR) representing muscle edema
- normal muscle contrast enhancement
- muscle bulk is normal
- causative lesions may be apparent such as:
- tumor compressing or displacing the neurovascular bundle
- nerve discontinuity due to penetrating trauma
Subacute and chronic denervation
- features are less specific
- muscle atrophy and fatty infiltration with an increase in T1 signal
- heterogeneous edema-like signal
- 1. Scalf RE, Wenger DE, Frick MA et-al. MRI findings of 26 patients with Parsonage-Turner syndrome. AJR Am J Roentgenol. 2007;189 (1): W39-44. doi:10.2214/AJR.06.1136 - Pubmed citation
- 2. William Palmer, Laura Bancroft, Fiona Bonar, Jung-Ah Choi, Anne Cotten, James F. Griffith, Philip Robinson, Christian W.A. Pfirrmann. Glossary of terms for musculoskeletal radiology. (2020) Skeletal Radiology. doi:10.1007/s00256-020-03465-1 - Pubmed