Electrodiagnostic examination is a fairly noninvasive method of assessing functional neuromuscular disorders in veterinary and human medicine. Routine electrodiagnostic examinations in domestic animals often include electromyography, motor and sensory nerve conduction evaluations, and assessment of SSEPs.1,2 Results of these diagnostic tests can help clinicians distinguish between myopathic and neuropathic (axonal or demyelinating) disease processes as well as differentiate between proximal and distal lesions within the peripheral nerves. Motor nerve conduction velocities can be determined by stimulating a minimum of 2 sites along a peripheral nerve and recording the compound muscle action potential (M wave) from a muscle innervated by that nerve.1 The SNCVs are determined by recording the conducted volley along a peripheral nerve following sensory nerve stimulation. The CNAP is a reflection of peripheral sensory nerve function.1,2 Cord dorsum potentials are stationary field potentials that are generated by pools of spinal cord interneurons in the lumbar and cervical intumescences. The presence of a CDP indicates that conducted sensory nerve action potentials from the brachial or lumbar plexus have reached the spinal cord.3,4 Despite the development of neuromuscular disorders in avian species, electrodiagnostic evaluations are not routinely performed, and to our knowledge, there is little information describing electrodiagnostic techniques in birds. Electromyography has been used to confirm the presence of brachial plexus avulsions in red-tailed hawks (Buteo jamaicensis)5 and assess organophosphate-induced delayed neuropathy in chickens.6 Reference values for ulnar MNCVs have been determined for rheas (Rhea americana) and barred owls (Strix varia),7 and cerebral SSEPs have been evaluated in studies8 to assess the efficacy of electrical stunning following stimulation of the radial nerve in chickens. Conduction velocities and evoked potentials have also been recorded following radial nerve stimulation and during open surgical laminectomy procedures in pigeons.9,10 Results of similar invasive experiments investigating evoked potentials and SNCVs following stimulation of the caudal cutaneous femoral nerve in chickens have been reported.11
The purpose of the study reported here was to develop a clinically applicable technique for recording CDPs following stimulation of the radial and ulnar nerves and establish reference values for radial and ulnar SNCVs in the wings of ducks. We hypothesized that CNAPs and CDPs could be consistently measured in birds following noninvasive stimulation of the radial and ulnar nerves and that the presence of the CDP would reflect the integrity of the brachial plexus. Mallard ducks (Anas platyrhynchos) were chosen as the model species for evaluating these techniques because of their size, tractability, and wing anatomy. It was anticipated that the SNCV and CDP values could potentially be used for assessment of brachial plexus integrity and function in mallard ducks and may be clinically applicable in the diagnosis of traumatic injuries to the brachial plexus; evaluation of toxic neuropathies associated with chemicals such as lead,12,13 arsenic,14 and n-hexane15; or assessment of the efficacy of therapeutic interventions such as a brachial plexus nerve blockade in this avian species.
Cord dorsum potential
Compound nerve action potential
Motor nerve conduction velocity
Sensory nerve conduction velocity
Somatosensory evoked (spinal cord) potential
Isoflo, Abbott Animal Health, Abbott Park, Ill.
Tidal wave 715, Respironics, Carlsbad, Calif.
Yellow Springs 700 Thermistor, Measurement Specialties, Dayton, Ohio.
Parks Medical Electronics, Aloha, Ore.
Speidel & Keller, Jungingen, Germany.
Nicolet Biomedical, Madison, Wis.
Grass-Telefactor, West Warwick, RI.
Nicolet S403 stimulator probes, Nicolet Biomedical, Madison, Wis.
Nicolet Viking IV EMG/Evoked Potential System, Nicolet Biomedical, Madison, Wis.
Beuthanasia, 1 mL/kg, IV, Schering-Plough Animal Health, Kenilworth, NJ.
Graphpad Instat, version 3.06, 32 bit for Windows, GraphPad Software Inc, San Diego, Calif.
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Cuddon PA, Delauche AJ, Hutchison JM. Assessment of dorsal nerve root and spinal cord dorsal horn function in clinically normal dogs by determination of cord dorsum potentials. Am J Vet Res 1999;60:222–226.
Shell L, Richards M, Saunders G. Brachial plexus injury in two Red-tailed hawks (Buteo jamaicensis). J Wildl Dis 1993;29:177–179.
Shell L, Jortner BS, Ehrich M. Assessment of organophosphorus-induced delayed neuropathy in chickens using needle electromyography. J Toxicol Environ Health 1988;25:21–33.
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Gregory NG, Wooten SB. Effect of electrical stunning on somatosensory evoked potentials in chickens. Br Vet J 1989;145:159–164.
Necker R, Meinecke CC. Conduction velocities and fiber diameters in a cutaneous nerve of the pigeon. J Comp Physiol [A] 1984;154:817–824.
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Mazliah J, Barron S, Bental E, et al. The effects of long-term lead intoxication on the nervous system of the chicken. Neurosci Lett 1989;101:253–257.
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Tseng HP, Wang YH, Wu MM, et al. Association between chronic exposure to arsenic and slow nerve conduction velocity among adolescents in Taiwan. J Health Popul Nutr 2006;24:182–189.
Yokoyama K, Feldman RG, Sax DS, et al. Relation of distribution of conduction velocities to nerve biopsy findings in n-hexane poisoning. Muscle Nerve 1990;13:314–320.
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Nickel R. Nerves of the spinal cord. In: Nickel R, Schummer A, Seiferle E, eds. Anatomy of the domestic birds. New York: Springer-Verlag Inc, 1977;131–143.
International Species Inventory System. Physiologic data references values for Anas platyrhynchos. Eagan, Minn: International Species Inventory System, 2002.
Redding RW, Ingram JT. Sensory nerve conduction velocity of cutaneous afferents of the radial, ulnar, peroneal, and tibial nerves of the cat: reference values. Am J Vet Res 1984;45:1042–1045.
Bagley RS, Wheeler SJ, Gay JM. Effects of age on temperaturerelated variation in motor nerve conduction velocity in healthy chickens. Am J Vet Res 1995;56:819–821.