Myopathy in CRPS-I: disuse or neurogenic?

The diagnosis Complex Regional Pain Syndrome type I (CRPS-I) is based on clinical symptoms, including motor symptoms. Histological changes in muscle tissue may be present in the chronic phase of CRPS-I. Aim of this study was to analyze skeletal muscle tissue from amputated limbs of patients with CRPS-I, in order to gain more insight in factors that may play a role in changes in muscles in CRPS-I. These changes may be helpful in clarifying the pathophysiology of CRPS-I. Fourteen patients with therapy resistant and longstanding CRPS-I, underwent an amputation of the affected limb. In all patients histological analysis showed extensive changes in muscle tissue, such as fatty degeneration, fibre atrophy and nuclear clumping, which was not related to duration of CRPS-I prior to amputation. In all muscles affected, both type 1 and type 2 fibre atrophy was found, without selective type 2 fibre atrophy. In four patients, type grouping was observed, indicating a sequence of denervation and reinnervation of muscle tissue. In two patients even large group atrophy was present, suggesting new denervation after reinnervation. Comparison between subgroups in arms and legs showed no difference in the number of changes in muscle tissue. Intrinsic and extrinsic muscles were affected equally. Our findings show that in the chronic phase of CRPS-I extensive changes can be seen in muscle tissue, not related to duration of CRPS-I symptoms. Signs of neurogenic myopathy were present in five patients.