Some Studies of the Clinical Neurophysiology of Denervation in the Dog

Magnetic stimulation of the radial nerve in dogs and cats with brachial plexus trauma: a report of 53 cases

Brachial plexus trauma is a common clinical entity in small animal practice and prognostic indicators are essential early in the course of the disease. Magnetic stimulation of the radial nerve and consequent recording of the magnetic motor evoked potential (MMEP) was examined in 36 dogs and 17 cats with unilateral brachial plexus trauma. Absence of deep pain perception (DPP), ipsilateral loss of panniculus reflex, partial Horner's syndrome and a poor response to MMEP were related to the clinical outcome in 29 of the dogs and 13 of the cats. For all animals, a significant difference was found in MMEP between the normal and the affected limb. Absence of DPP and unilateral loss of the panniculus reflex were indicative of an unsuccessful outcome in dogs. Additionally, the inability to evoke a MMEP was associated with an unsuccessful outcome in all animals. It was concluded that magnetic stimulation of the radial nerve in dogs and cats with brachial plexus trauma may provide an additional diagnostic and prognostic tool.

Diagnosis of cauda equina abnormalities by using electromyography, discography, and epidurography in dogs

Electromyography (EMG), L7-S1 discography and epidurography were investigated in 15 dogs with clinical signs of cauda equina dysfunction and in 7 control dogs without such clinical signs. Electromyography of paraspinal and pelvic limb muscles was done in 13 of 15 affected dogs. An L7-S1 discogram followed by an epidurogram was performed in all 22 dogs using 20% iopamidol. Results of discograms, epidurograms, and gross necropsy examinations were normal in six of seven control dogs. The one dog in which these studies were abnormal had a mild L7-S1 disc protrusion that did not result in nerve root compression at necropsy. Electromyographic analysis was 100% accurate in predicting the presence or absence of cauda equina disease. None of the results of discograms were falsely negative. Twelve of 15 discograms in clinically affected dogs indicated dorsal disc protrusion, but 2 of these protrusions were found to be noncompressive at surgery (13% error). Abnormal epidurograms occurred in 9 of 15 clinically affected dogs. There was one false positive and two false negatives (20% error). Electromyography was a sensitive screening technique for the presence of cauda equina disease. Discography may be more sensitive for detection of L7-S1 disc protrusion than epidurography. An abnormal radiographic contrast study of the cauda equina may only be useful when combined with an abnormal EMG.

Insulinoma and subclinical peripheral neuropathy in two dogs

Two dogs with diffuse, subclinical polyneuropathy associated with insulinoma are reported. Seizures were the dominant sign of central nervous system disease. One dog had clinical signs of facial nerve paralysis. Lesions in selected appendicular and cranial nerves included a mixture of demyelination, remyelination, and axonal degeneration. The incidence (range: 18-47%) of these changes far exceeded that of comparable nerves from six control dogs (range 0-11%). Myopathic and electrodiagnostic findings were compatible with the nerve changes.

Clinical application of neuromuscular electrophysiology in the dog: a review

A review of the literature concerning the application of electromyography and electroneurography in canine neurology is presented. Measurements of amplitude and duration of motor unit potentials in normal dogs varied largely in the various reports. It was therefore concluded that these measurements are of limited clinical value. The results of motor and sensory nerve conduction studies in normal dogs are summarised. The differences between the methods used are discussed. It is concluded that variations in reported normal values are due mainly to differences in method. The application of electromyography and electroneurography in neuromuscular disorders in the dog is systematically presented, based upon the reported diagnoses. The considerable number of first descriptions of newly-recognised and described neuromuscular diseases appears to be related to the introduction of neuromuscular electrophysiology into veterinary medicine.

Stimulation techniques and response characteristics of the M and F waves and H reflex in dogs

The voltage and duration of electrical rectangular pulsed stimuli needed to produce an F wave and a monosynaptic reflex (H wave) and the characteristics of these responses were recorded in clinically normal dogs. Optimal stimulus to produce H waves was 0.1 to 0.2 ms and less than 80 volts. F waves were variable in appearance and were most evident following 0.5 ms and 125 to 150 volt stimulation. F waves had shorter latency than comparable H waves.

Distal symmetrical polyneuropathy in a dog

A 1.3-year-old Great Dane dog had a chronic progressive neurologic disease clinically expressed as a distal symmetrical polyneuropathy characterized by weakness and bilateral atrophy of bulbar and distal appendicular musculature. Qualitative and quantitative studies showed neurogenic atrophy of muscles below the elbow and stifle. There was Wallerian-type degeneration, Schwann cell proliferation and cell bands of Büngner, and marked depletion of medium (5 to 8 microns) to large (9 to 15 microns) diameter myelinated fibers in the distal parts of appendicular and laryngeal nerves. Sensory (saphenous and superficial radial) and autonomic (sympathetic and dorsal vagal trunk) nerves were affected to a lesser degree. A distribution of distal axonal degeneration suggested a dying back process. The disease differed from classical dying back disorders by absence of axonal degeneration in selected pathways of the central nervous system.