Clinical and laboratory findings of 21 patients with radiation-induced myopathy.
BACKGROUND
Limited data are available on radiation-induced myopathy (RIM) in adult cancer survivors.


METHODS
We retrospectively reviewed the clinical, electrophysiological, serological, radiological and pathological findings of patients with RIM seen in the neurology clinic over a 11-year period (2002-2013).


RESULTS
Out of 251 patients with radiotherapy-induced neuromuscular complications, 21 had RIM (11 men and 10 women). Cancers included: Hodgkin's lymphoma (13), non-Hodgkin's lymphoma (one), pinealoblastoma (one), tongue (two), nasopharyngeal (one), thyroid (one) and testicular cancer (two). Various radiotherapy protocols were used but all patients received neck and upper torso radiation. The mean latency between radiation exposure and onset of RIM was 15 years (range 2-45 years). The most common presentation was head drop (43%) followed by neck pain (38%). Axial (86%) and periscapular (81%) muscle weakness and atrophy were frequent findings. Two patients died in follow-up from hypercapnic respiratory failure secondary to neuromuscular weakness. Serum creatine kinase values were usually normal or slightly elevated. EMG revealed predominantly myopathic changes in the axial and periscapular muscles. Half of the muscle biopsies (6/12) showed myopathic changes; increased connective tissue elements were observed in seven of eight muscle biopsies performed in the irradiated field; and mitochondrial dysfunction in two.


CONCLUSIONS
RIM is a potential long-term neuromuscular adverse effect of radiation exposure in Hodgkin's disease and other types of cancer manifesting predominantly as head drop and can be fatal due to neuromuscular respiratory failure. Improved radiotherapy protocols might reduce the risk of RIM and other radiation-induced neuromuscular complications.
Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.
Partha S
PS
Ghosh
Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA.
Margherita
M
Milone
D000328:Adult; D000368:Aged; D001284:Atrophy / Q000473:pathology; D003402:Creatine Kinase / Q000097:blood; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008910:Minnesota / Q000453:epidemiology; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009135:Muscular Diseases / Q000453:epidemiology / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D009336:Necrosis / Q000473:pathology; D009369:Neoplasms / Q000150:complications / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000453:epidemiology / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D013997:Time Factors
D003402:Creatine Kinase
EMG; Lymphoma; Muscle Disease; Neurochemistry, Muscle; Neuromuscular