Neuromuscular electrodiagnostic studies in ferrets

Neurologic diseases are frequently reported in the domestic ferret (Mustela putorius furo), but experiences with most neurodiagnostic tests in this species are limited. Especially lacking are data on clinical neurophysiology procedures. Object of this study was to establish the normal values of motor nerve conduction studies (MNCS), supramaximal repetitive nerve stimulation (SRNS), F waves and cord dorsum potentials (CDP) of tibial nerve in the domestic ferret. The tests were performed on 10 sedated domestic ferrets (6 females and 4 males) of ages ranging from 8 months to 2 years while rectal temperature was maintained above 36.5 1C. All subjects had no history of neurologic problems and unremarkable physical and neurological examinations. The sciatic-tibial nerve was stimulated at the level of the femoral neck (MNCS) and at the tarsus (MNCS, SRNS, F waves, CDP), and the muscular potentials were recorded in the plantar interosseous muscles (MNCS, SRNS, F waves). Trains of 10 stimuli with a rate of 2Hz were used for SRNS. The late responses (F waves) were obtained recording at least 20 supramaximal stimuli. CDP were recorded from the L4-L5 intervertebral space after averaging 250–500 stimulations. Only one tibial nerve for each subject was evaluated. Descriptive statistics were calculated for the main parameters. Conduction velocity, proximal and distal CMAP amplitudes of MNCS of sciatic-tibial nerve were respectively 63.25 1/_ 7.6 m/sec, 10.79 1/_ 2.7 mV, 13.02 1/_ 3.4 mV. In all ferrets for each train of SRNS were obtained decrements of less than 8% of CMAP amplitudes and areas between the first and the following waves. The late potentials (F waves) had a minimum latency of 8.49 1/_ 0.65 ms and a ‘‘F ratio’’ of 1.921/_ 0.169. CDP onset latency was 1.991/_ 0.03 ms, onset to peak latency difference was 1.85 1/_ 0.36 ms and peak amplitude was 4.92 1/_ 2.93 uV. The waveforms recorded in ferrets were not dissimilar from those found in other species. Late potentials could be elicited only with supramaximal stimuli, therefore they were probably constituted mainly by F waves, but a contamination by the H reflex can’t be excluded. Latencies of these F waves and of CDP were stable among subjects as expected for the lack of limb length variability of this species. At the authors’ knowledge this is the first report on normal values of neuromuscular electrodiagnostic studies in domestic ferrets. More studies including other electrodiagnostic tests and nerves are needed to further increase the information available for investigation of disorders affecting the peripheral nervous system of ferrets.