Exercise induced muscle blood flow is decreased in Charcot–Marie–Tooth disease type 1 polyneuropathy: a power Doppler analysis

Background and purpose: Intramuscular blood flow increases during physical activity and may be quantified immediately following exercise using power Doppler sonography. Post-exercise intramuscular blood flow is reduced in patients with muscular dystrophy, associated with disease severity and degenerative changes. It is not known if intramuscular blood flow is reduced in patients with neuropathy, nor if it correlates with muscle strength and structural changes. The aim was to determine whether blood flow is reduced in patients with polyneuropathy due to Charcot–Marie–Tooth disease type 1 (CMT1) and to compare more affected distal to less affected proximal muscles. Methods: This was a cross-sectional study including 21 healthy volunteers and 17 CMT patients. Power Doppler ultrasound was used to quantify post-exercise intramuscular blood flow in distal (gastrocnemius) and proximal (elbow flexor) muscles. Intramuscular blood flow was compared to muscle echo intensity, muscle strength, disease severity score, patient age and electromyography. Results: Polyneuropathy patients showed reduced post-exercise blood flow in both gastrocnemius and elbow flexors compared to controls. A more prominent reduction was seen in the gastrocnemius (2.51% vs. 10.34%, p < 0.0001) than in elbow flexors (4.48% vs. 7.03%, p < 0.0001). Gastrocnemius intramuscular blood flow correlated with muscle strength, disease severity and age. Receiver operating characteristic analysis showed that quantification of intramuscular blood flow was superior to echo intensity for detecting impairment in the gastrocnemius (area under the curve 0.962 vs. 0.738, p = 0.0126). Conclusion: Post-exercise intramuscular blood flow is reduced in CMT1 polyneuropathy. This reduction is present in both impaired distal and minimally affected proximal muscles, indicating it as an early marker of muscle impairment due to neuropathy.