PubMed Health⌕ Search

Biomedical subjects

L Poncelet

Publications and source records attributed to L Poncelet.

27 records · Page 2Linked to original sources
PubMed1993

Influence of body size on tibial nerve somatosensory evoked potentials in dogs.

Somatosensory evoked potentials in response to tibial nerve stimulation were recorded from the scalp of 31 clinically normal mixed-breed dogs. The latency and amplitude of a main positive potential (P18), recorded with a frontal electrode referenced to the nose, were measured in subjects with body length ranging from 316 to 962 mm. A linear relation to body size explained the variations in latency among dogs (r2 = 0.81); the amplitude variations were explained in part by body size (r2 = 0.44). Bilateral tibial nerve stimulation significantly (P < 0.05) increased the amplitude of P18, but its latency was unaffected, compared with unilateral stimulation. Results of unilateral right and left tibial nerve stimulation were compared and were not different. Replacing acepromazine with xylazine as premedication before thiopental anesthesia did not influence the recordings.

Animals↗
PubMed1992

Effect of bilateral stimulation on spinal evoked potentials in dogs.

We compared the effects of bilateral vs unilateral tibial nerve stimulation of percutaneously recorded spinal evoked potentials (SEP) in the lumbar and caudal thoracic area in dogs. The overall amplitude of the SEP is increased by this means. Use of this method could improve legibility of the recordings. Amplitudes of root and interneuronal components of the SEP are doubled as are cranially transmitted depolarizations. However, the amplitude of the SEP component arising from the primary afferents' depolarization was less than doubled. Latencies of the components were unaffected by bilateral stimulation. Careful observation of the latencies disclosed a 0.9-ms delay in transmission of the fastest component in the midlumbar area. This delay was consistent with results of previous cordotomy experiments, and could influence precision of conduction velocity measurement.

Animals↗
PubMed1991

Nature of the late potentials and F-ratio values in dogs.

There is controversy about the nature of the late potentials (F-waves and H-reflexes) in dogs. This work has attempted to clarify the problem by comparing late potentials in eight intact and four chronically deafferented dogs. Pure H-reflexes were recorded inconsistently from intact preparations at voltages below the threshold for the M-wave. At stimulation voltages giving maximum direct responses, there was no statistically significant difference between the amplitude and latency of the late potentials of the two groups. However, there was a tendency for the late potentials to be of larger amplitude and longer duration in intact preparations. Late potentials in intact preparations had a composite waveform consisting of both F-waves and H-reflex components. F-waves only were present in deafferented limbs, and their amplitude was proportional to the intensity of the stimulus. F-ratios could be calculated by using the latencies of the late potentials, because the F-wave did not have a longer latency than the H-reflex. The following reference values for the F-ratio are proposed: 1.954 +/- 0.086 when stimulating at the hock and 0.883 +/- 0.052 when stimulating at the popliteal fossa.

Animals↗
PubMedDate not supplied

Bilateral deafness in a maltese terrier and a great pyrenean puppy: inner ear morphology.

Two puppies, a 4-month-old female Maltese terrier and a 6-week-old male Great Pyrenean, were presented for confirmation of bilateral deafness by electrophysiological testing. In both puppies, brainstem auditory potentials were not evoked by 90 dB NHL click stimulation of each ear. Examination of the inner ear revealed a bilateral cochleo-saccular degeneration in both animals. The lesions were characterized by generalized atrophy of the stria vascularis, collapse of the cochlear duct, degeneration of the organ of Corti, an abnormal tectorial membrane, and saccular collapse, with a normal spiral ganglion. The cochlear duct was entirely obliterated throughout the cochleae in the Maltese terrier puppy, but was locally and asymmetrically affected in the Great Pyrenean. The abnormalities observed in the Maltese terrier puppy were identical with those previously described in deaf Dalmatian puppies; the lesions observed in the Great Pyrenean, however, were less typical. This is the first histopathological description of cochleo-saccular degeneration in the Maltese terrier and Great Pyrenean breeds. In both puppies the defect was probably congenital.

Animals↗
PubMedDate not supplied

Probable trigeminal nerve schwannoma in a dog.

A 7-year-old male Husky dog developed atrophy of the right masseter muscle and pruritus of the right side of the face. A myogenic origin was excluded using muscular biopsy. Electrophysiologically, there was involvement of the motor and sensory fibers of the trigeminal nerve, suggesting a lesion located between the brainstem and the trigeminal ganglion. On MRI examination, a nodular mass was detected in the right caudal fossa. This mass was characterized by intense enhancement after injection of contrast medium. Because of the progressive clinical signs, electrophysiology, and MRI results, a presumptive diagnosis of a trigeminal nerve schwannoma was made. The animal's condition improved slightly with corticosteroids. The dog underwent euthanasia 3 months after initial presentation. Necropsy was not performed.

Animals↗
PubMedDate not supplied

Brainstem auditory evoked potential wave V latency-intensity function in normal Dalmatian and Beagle puppies.

This study investigated whether Dalmatian puppies with normal hearing bilaterally had the same click-evoked brainstem auditory potential characteristics as age-matched dogs of another breed. Short-latency brainstem auditory potentials evoked by condensation and rarefaction clicks were recorded in 23 1.5- to 2-month-old Dalmatian puppies with normal hearing bilaterally by a qualitative brainstem auditory evoked potential test and in 16 Beagle dogs of the same age. For each stimulus intensity, from 90 dB normal hearing level down to the wave V threshold, the sum of the potentials evoked by the 2 kinds of stimuli were added, giving an equivalent to the alternate click polarity stimulation. The slope of the L segment of the wave V latency-intensity curve was steeper in Dalmatian (-40 +/- 10 micros/dB) than in Beagles (-28 +/- 5 micros/dB, P < .001) puppies. The hearing threshold was lower in the Beagle puppies (P < .05). These results suggest that interbreed differences may exist at the level of cochlear function in this age class. The wave V latency and wave V-wave I latencies differences at high stimulus intensity were different between the groups of puppies (4.3 +/- 0.2 and 2.5 +/- 0.2 milliseconds, respectively, for Beagles; and 4.1 +/- 0.2 and 2.3 +/- 0.2 milliseconds for Dalmatians, P < .05). A different maturation speed of the neural pathways is one possible explanation of this observation.

Animals↗