Summary The middle and inner ears of 16 dogs, from 1.5 to 17 years of age, with differing degrees of suspected hearing loss were examined. Auditory function was assessed subjectively, and electrophysiologically by recording brainstem auditory‐evoked responses (BAER) to click stimuli. Ossicular chains and stapediovestibular articulations were evaluated macroscopically and by light microscopy for evidence of bony ankylosis; no abnormalities were found. A determination of spiral ganglion packing density revealed a loss of spiral ganglion cells in all areas of the cochlea in dogs of the deaf group and in the upper and lower basal region of dogs from the hearing impaired group. The largest losses of spiral ganglion cells in the deaf group were located in the upper and lower basal region. The deaf group's density was reduced to 44 % (upper basal) and 15 % (lower basal) of the normal hearing group. The largest spiral ganglion cell loss for dogs in the hearing impaired group occurred in the lower basal region where the density was reduced to 40 % of the normal hearing group. These morphological findings in the aging canine are consistent with a peripheral nerve hearing loss. Zusammenfassung Verminderung der Neuronen des Ganglion spirale bei alternden Hunden mit Hörschaden Bei 16 Hunden im Alter von 1,5 bis 17 Jahren mit offenbar unterschiedlich ausgeprägten Hörschäden wurde das Mittel‐ und Innenohr untersucht. Die Hörfunktion wurde subjektiv sowie elektrophysiologisch mittels Registrierung der Reaktion des Hirnstamms auf kurze Schallreize beurteilt. Die Anordnung der Gehörknöchelchen sowie der Kontakt des Steigbügels mit dem ovalen Fenster wurden makroskopisch untersucht. Für den Nachweis knöcherner Ankylosen wurden lichtmikroskopische Untersuchungen durchgeführt. In beiden Fällen ergaben sich keine Veränderungen. Die Bestimmung der Populationsdichte von Nervenzellen im Ganglion spirale ergab bei den tauben Hunden in allen Abschnitten der Cochlea einen Verlust an Ganglienzellen, während dies bei Hunden mit verringertem Hörvermögen im Bereich der oberen und unteren Basalregion der Fall war. Die größten Verluste an Ganglienzellen waren bei den tauben Hunden in der oberen und unteren Basalregion zu verzeichnen. Die Zelldichte war bei der Gruppe der tauben Hunde auf 44 % (obere Basalregion) bzw. 15 % (untere Basalregion) der Gruppe der normal hörenden Hunde reduziert. Der größte Verlust an Ganglienzellen war bei den Hunden mit beeinträchtigtem Hörvermögen im Bereich der unteren Basalregion festzustellen, wo die Zelldichte auf 40% der normal hörenden Hunde vermindert war. Diese morphologischen Befunde beim alternden Hund sprechen für einen peripheren nervalen Hörschaden.
Posterior paresis of increasing severity was observed in two dogs, a female crossbred Terrier (9 months old) and a male Poodle (5 years old). Radio‐graphic examination revealed that in both dogs paresis was due to atlanto‐axial subluxation resulting from a congenital separation of the odontoid process. Necropsy and histopathological studies confirmed these findings.
Using 20 calves of 3% months age or less, clinical signs were closely evaluated for 5, 10 or 15 days following experimental lesions of the spinal cord or dorsal rootlets. The experimental preparations included transections and hemisections at the TIO neuromere level, rhizotomy of the dorsal rootlets of the left lumbosacral plexus, and application of pressure at the L, neuromere level. The calves were necropsied at 5, 10 or 15 days post-lesion.The results of motor findings indicate that the order of return of reflexes following spinal shock in the calf is anal and tail, pelvic limb flexor and patellar reflex. It appears very likely that the gastrocnemius reflex returns at about the same time as the patellar reflex. The L, spinal nerve does not appear to be an important component of the patellar reflex in the calf. Calves are able to maintain motor control of the pelvic limbs with lesions of the spinal cord that would cause hemiparesis in dogs or humans.The sensory findings indicate that the L3 nerve is a component of the lateral cutaneous femoral nerve and extends to the cranial lateral surface of the crus. Sensory innervation by the saphenous nerve can be present even when femoral nerve innervation is insufficient to produce the patellar reflex. Transection of the portion of the spinal cord corresponding to the lateral spinothalarnic tract does not produce a contralateral area of analgesia or hypalgesia as it does in humans.It must be concluded that extrapolating information about the nervous system of humans or dogs to that of the ox may lead to erroneous results when evaluating the ox for neurologic deficits. The ox has a spinal cord which can adapt to tremendous insults and still maintain some if not all of its motor and sensory functions. Just how it does this should be of interest to those investigating the human spinal cord.
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