Objective—To determine functional and morphologic
changes in palmar digital nerves after nonfocused
extracorporeal shock wave (ESW) treatment in horses.
Procedures—The medial and lateral palmar digital
nerves of the left forelimb were treated with nonfocused
ESWs. The medial palmar digital nerve of the
right forelimb served as a nontreated control nerve.
At 3, 7, and 35 days after treatment, respectively, 2
horses each were anesthetized and nerves were surgically
exposed. Sensory nerve conduction velocities
(SNCVs) of treated and control nerves were recorded,
after which palmar digital neurectomies were performed.
Morphologic changes in nerves were
assessed via transmission electron microscopy.
Results—Significantly lower SNCV in treated medial
and lateral nerves, compared with control nerves, was
found 3 and 7 days after treatment. A significantly lower
SNCV was detected in treated medial but not lateral
nerves 35 days after treatment. Transmission electron
microscopy of treated nerves revealed disruption of the
myelin sheath with no evidence of damage to Schwann
cell bodies or axons, 3, 7, and 35 days after treatment.
Conclusions and Clinical Relevance—Nonfocused
ESW treatment of the metacarpophalangeal area resulted
in lower SNCV in palmar digital nerves. This effect
likely contributes to the post-treatment analgesia
observed in horses and may result in altered peripheral
pain perception. Horses with preexisting lesions may be
at greater risk of sustaining catastrophic injuries when
exercised after treatment. (Am J Vet Res