Ultrasound appearance of forearm muscles in 18 patients with complex regional pain syndrome 1 of the upper extremity.

Objective: To explore the potential diagnostic utility of musculoskeletal ultrasonography (USG) changes in complex regional pain syndrome type 1 (CRPS-1) of the upper extremity.

Methods: With informed consent, 18 consecutive patients referred to our institution with CRPS-1 of the upper limb were examined with ultrasound scanning of both upper limbs. Qualitative comparison of the scan of the forearm muscles of the affected side with the unaffected side was made.

Results: The muscles affected by CRPS-1 demonstrated increased echogenecity. The outlines of the muscles were either indistinct or completely obliterated. A group of several muscles appeared like one homogenous, hyperechoic mass, with loss of normal architecture. Compared with the unaffected side, the muscle thickness on the CRPS-1 side measured by calipers on ultrasound was reduced irrespective of the duration of disability or disuse of the hand. The flexors and extensor muscles of the forearm were maximally affected.

Conclusion: Ultrasonography provides useful anatomical information, regarding structure, kinesiology, and gross pathological changes of muscle, that may prove useful in understanding the motor impairment associated with CRPS-1. USG shows promise as a cost-effective bedside tool for the diagnosis of CRPS-1 and in guiding physical therapy.