This chapter on the physiology of the auditory system discusses the divisions of the ear; sound l... more This chapter on the physiology of the auditory system discusses the divisions of the ear; sound localization and central projections in dogs and cats.
1. Anatomy of the Auditory System Anatomy of the External Ear Anatomy of the Middle Ear Anatomy o... more 1. Anatomy of the Auditory System Anatomy of the External Ear Anatomy of the Middle Ear Anatomy of the Inner Ear Development of the Ear Blood Supply of the Ear Innervation of the Ear 2. Physiology of the Auditory System Sound Divisions of the Ear The Cochlea The Organ of Corti Cochlear Information Processing Sound Localization Central Projections 3. Forms and Mechanisms of Deafness Unilateral vs. Bilateral Deafness Partial vs. Total Deafness Syndromic vs. Non-syndromic Deafness Peripheral vs. Central Deafness Forms of Peripheral Deafness Other Forms of Hearing Disturbance Treatment of Deafness 4. Hereditary Deafness Dogs, Cats 5. Later Onset Deafness Ototoxicity Presbycusis Noise Trauma Anesthesia-associated Deafness Conduction Deafness 6. Brainstem Auditory Evoked Response (BAER) Biophysics of BAER Recordings Overview of the BAER Extrinsic Factors Affecting the BAER Intrinsic Factors Affecting the BAER Clinical Applications of the BAER 7. Other Tests of Auditory Function Endocochlear Potential Cochlear Microphonic and Summating Potential Electrocochleogram Acoustic Impedance, Tympanometry and the Acoustic Reflex Middle and Long Latency Evoked Responses Distortion Product Otoacoustic Emissions 8. Living with a Deaf Dog or Cat Behaviour of Deaf Animals Hand Signal Training Counselling For Owners/Breeders of Deaf Animal.
Summary: No influences of chronic cerebellar stimulation were found in 10 different controlled ex... more Summary: No influences of chronic cerebellar stimulation were found in 10 different controlled experiments in 5 different monkeys with chronic alumina‐induced psychomotor seizures. The stimulation paramétérs used were comparable to those used in human epileptics, and continuous daily EEG and behavioral monitoring allowed all seizures to be measured for daily frequency and duration over the several weeks of the experiments. Nocturnal seizures were similarly quantified in 3 monkeys to verify that cerebellar stimulation did not affect them. Motor cortex potentials evoked by cerebellar pulses confirmed that the stimulations were activating the cerebellum throughout the experiments, and measures of electrode access resistance and impedance verified that the electrodes remained in contact with the cerebellum. In one monkey given phenobarbital medication, interictal morbid behavior appeared to be improved by chronic stimulation of either cerebellum or dorsolateral frontal cortex, thus indicating an arousal influence of brain stimulation not due to cerebellum per se.RÉSUMÉAucun effet de la stimulation cérébelleuse chronique n'a pu être observé au cours de 10 expearimentations différentes effectuées chez 5 singes présentant de façon chronique des crises psychomotrices induites par L';alumine. Les conditions de stimulation étaient tout à fait comparables à celles utilisées chez les malades épileptiques; durant les quelques semaines de L';expérimentation une étude diurne continue de L';E.E.G. et du comportement des animaux permit d'enregistrer I'ensemble des crises diurnes et d'en précisr la fréquence et la durée. Les crises nocturnes ont étéétudiées de la même façon chez 3 singes afin de vérifier que la stimulatìon cérébelleuse n'agissait pas sur elles. Les potentiels évoqués au niveau du cortex moteur par les stimulations cérébelleuses confirment que celles‐ci activaient effectivement le cervelet dur‐ant toute la durée des expérimentations; des mesures de la résitance et de L';impédance d'entrée des électrodes permettaient de vérifier que celles‐ci restaient bien en contact avec le cervelet. Chez un singe recev‐ant du phénobarbital, le comportement intercritique a été amélioré aussi bien par la stimulation chronique du cervelet que par celle du cortex frontal dorso‐latéral; ceci traduit L';obtention d'un effet d'éveil par la stimulation cérébrale non liée directement au cervelet lui‐même.RESUMENLa estimulación cerebelosa crónica no tuvo influencia en diez experimentos controlados diferentes llevados a cabo en cinco monos con crisis psicomotoras crónicas inducidas con alúmina. Los parámetros de estimulación fueron comparables a los que se utilizan en seres humanos con epilepsyía ye se monítorizó de modo continuo tanto la frecuencia como la duratión de todas las crisis durante las varias semanas que duraron los experimentos. Egta monitorización incluyó observatión del EEG y de la conducta. Las crisis nocturnas fueron también cuantificadas en tres monos verificando que la estimulación cerebelosa no las modified. Potenciales evocados en la corteza motora por medio de pulsos cerebelosos confirmaron que las estimulaciones activaron el cerebelo a todo lo largo de los experimentos y la medición de la resistencia y de la impedancia de los electrodos evidenció que esos electrodos estaban en contacto con el cerebelo. En un mono al que se le administró fenobarbital, se notó una mejoria en su conducta inter‐ictal tanto cuando se estimuló de modo crónico el cerebelo como la corteza frontal dorso‐lateral. Esto indicó que la influencia del alertamiento cerebral por estimulación no se debía al cerebelo “per se”.ZUSAMMENFASSUNGIn 10 unterschiedlich kontrollierten Experimenten bei 5 verschiedenen Affen mit chronischen Aluminium‐induzierten psychomotorischen Anfällen konnte kein Einfluß der chronischen zerebellären Stimulation gefunden werden. Die Parameter der Stimulation waren vergleichbar mit denen, die bei Patienten mit Epilepsie angewendet werden; kon‐tinuierliches Monitoring des EEG und des Verhaltens erlaubte es, alle Krämpfe hinsichtlich Häufigkeit und Dauer während mehrerer Wochen des Experiments aufzuzeichnen. Nächtliche Krämpfe wurden ebenfalls bei 3 Affen quantifiziert und nachgewiesen, daß die zerebelläre Stimulation sie nicht beeinträchtigte. Die motorischen Cortexpotentiale, die durch zerebelläre Stimulation hervorgerufen werden, bestätigen, daß die Stimulationen das Zerebellum während der Experimente aktivierte; Untersuchungen des Elektrodenwiderstands und der Impedanz bestätigten, daß die Elektroden mit dem Zerebellum im Kontakt blieben. Bei einem Affen unter Phenobarbitalmedika‐tion schien das interiktale Verhalten sowohl durch chronische Stimulierung des Zerebellums wie des dor‐solateralen frontalen Cortex gebessert. Das deutet darauf hin, daß ein Einfluß der Hirnstimulation auf das Arousal nicht speziell dem Zerebellum zukommt.
Veterinary Clinics of North America-small Animal Practice, Jul 1, 1999
Congenital deafness in dogs and cats is primarily of the hereditary sensorineural form associated... more Congenital deafness in dogs and cats is primarily of the hereditary sensorineural form associated with white pigmentation genes, although acquired forms of deafness are possible. Highest prevalence is seen in white cats, especially those with blue eyes, and the Dalmatian, with many other dog breeds affected to some extent. This deafness results from degeneration of the cochlear blood supply at age 3-4 weeks, presumably resulting from suppression of melanocytes by the white (cat) or merle or piebald (dog) genes. Mechanism of inheritance is not understood for most breeds. Such animals should not be bred and may present liabilities for their owners. Objective diagnosis of deafness, especially when unilateral, relies on the brainstem auditory evoked response, an electrodiagnostic test where electrical activity in response to a click stimulus is recorded from the scalp using needle electrodes and a special purpose computer. Client counseling guidelines are presented.
Pigment-associated deafness is a common hereditary condition in a range of dog breeds. The aim of... more Pigment-associated deafness is a common hereditary condition in a range of dog breeds. The aim of this study was to perform a genome-wide association analysis to investigate the genetic architecture of deafness in Australian Cattle Dogs. Genotypes for 104 757 polymorphisms in 216 dogs were available for analyses after quality control. A genomic relationship matrix was used in the mixed model analyses to account for polygenic effects, as we tested each polymorphism for its association with deafness, in a case/control experimental design. Three approaches were used to code the genotypes and test for additive, recessive and dominant SNP effects. The genome-wide association study analyses identified a clear association peak on CFA20, with the most significant SNPs on this chromosome (1.29 × 10-4 ) in the vicinity of MITF. Variants in MITF have been associated with white pigmentation in dogs and with deafness in humans and other species, supporting the premise that canine deafness is associated with variants in or near this gene. A recessive inheritance for the peak in CFA20 is possible given the significant results in the recessive model; however, the estimated heritability was low (4.54 × 10-5 ). Further validation, identification of variants and testing in other dog breeds are needed.
A seizure disorder of 4.5 years' duration in a 6-year-old female Nubian goat was diagnosed as par... more A seizure disorder of 4.5 years' duration in a 6-year-old female Nubian goat was diagnosed as partial epilepsy on the basis of history, focal electroencephalogram (EEG) abnormalities, convulsive response to ketamine, and necropsy findings. The goat appeared to maintain consciousness during her seizures. A 1.5-day period of continuous seizures during a pregnancy at age 1.5 years may have resulted in a postanoxic seizure focus responsible for the seizures. A morphologic cause for the seizures was not detected. Two spontaneous seizures and 2 drug-induced seizures were detected during 1 month of observation after donation. The amplitude of the EEG over the left frontocentral cortex was depressed, and periodic bursts of high-frequency interictal spiking were detected over the same site. Acepromazine, intermittent photic stimulation, or ketamine after acepromazine failed to elicit seizures or EEG abnormalities, but ketamine alone (50 mg, IV) twice elicited seizures. Seizure severity appeared to parallel plasma estrogen concentration.
Determinations were made by laser nephelometry of serum and CSF immunoglobulin (Ig) G concentrati... more Determinations were made by laser nephelometry of serum and CSF immunoglobulin (Ig) G concentrations in Suffolk sheep with naturally occurring scrapie. The serum IgG concentrations in 3 sheep with confirmed or suspected scrapie were between 2,140 and 3,290 mg of IgG/100 ml, and the CSF values were between less than 10 and 75 mg of IgG/100 ml. In 8 clinically healthy (control) sheep, serum IgG concentrations were 2,647 to 7,380 mg/100 ml and CSF IgG concentrations were between 0 (undetectable) and 162 mg/100 ml. A sheep with pulmonary adenomatosis had 1,445 mg of IgG/100 ml of serum. The results indicated that neither serum nor CSF IgG concentrations were increased in sheep with naturally occurring infection with scrapie and that the severity of the disease did not correspond with the IgG concentration.
Recordings of visual-evoked potentials that were induced by flashes of white light were obtained ... more Recordings of visual-evoked potentials that were induced by flashes of white light were obtained from 13 Beagle pups to document the development of the response from age 7 to 100 days. Responses were recorded between needle electrodes placed on the nuchal crest and the interorbital line, with ground at the vertex. Five alternating positive (P) and negative (N) peaks were observed in most visual-evoked potentials: P1, N1, P2, N2, and P3. Responses were recorded from 2 pups prior to opening of the eyelids. Recordings were performed without sedation or dark adaptation. Peak latencies were essentially mature (equal to those of adult dogs) by day 11 for P1, and by day 38 for N1 and P2. The latencies to N2 and P3 did not reach adult values by day 100, but did reach plateau values by day 43. The P1-N1 amplitude measurements reached mature levels by day 14, whereas N1-P2 amplitudes were mature by day 32. The P2-N2 and N2-P3 amplitudes reached plateaus that greatly exceeded adult amplitudes by days 50 and 58, respectively. Maturation of visual-evoked potential responses paralleled reported morphologic development of the visual cortex. All of the measured latency and amplitude values had significant (P less than or equal to 0.004) linear regression lines of latency vs age or amplitude vs age.
Electroencephalogram (EEG), brain stem auditory-evoked potential, and flash visual-evoked potenti... more Electroencephalogram (EEG), brain stem auditory-evoked potential, and flash visual-evoked potential recordings were taken from healthy sheep and from 3 sheep with scrapie, a CNS slow virus infection. The EEG changes included semi-periodic, polyphasic, high-voltage sharp waves (bilaterally synchronous and symmetric in all channels), and a cyclic alternating pattern consisting of a high-voltage low-frequency phase, followed by a low-voltage high-frequency phase. The high-voltage phase occurred with increased arousal, and the low-voltage phase occurred with decreased arousal. Myoclonic jerks were coincident with EEG sharp waves in one sheep with scrapie. Several spontaneous focal seizures were observed. Wave-form amplitudes were greatly reduced in the brain stem auditory-evoked potential and flash visual-evoked potential; degree of reduction did not always correlate with disease severity. The EEG and evoked potential changes were seen in an exposed sheep that had not yet developed clinical signs of scrapie.
Recordings of averaged brain stem auditory-evoked potentials were obtained from 13 Beagle pups of... more Recordings of averaged brain stem auditory-evoked potentials were obtained from 13 Beagle pups of both genders to document the postnatal development of the response from age 1 to 76 days. Responses were recorded between needle electrodes placed on the vertex and the ipsilateral ear, with ground at the interorbital line. Recordings were performed without sedation. Low-amplitude responses to high-intensity stimuli could be recorded from animals prior to opening of the ear canals. Peak latencies did not change after day 20 for peak I, day 30 for peaks II and III, and day 40 for peak V. As a result, the interpeak latencies between peaks I and III did not change after day 30, but continued to decrease until day 40 for peaks III-V and I-V. Peak amplitudes reached plateau values by day 20 (peak I) or day 30 (peaks II, III, and V). All of the measured latency and amplitude values had significant (P less than 0.001) linear regression lines of latency vs age and amplitude vs age. The brain stem auditory-evoked potential thresholds were mature by day 20.
Veterinary Clinics of North America-small Animal Practice, Nov 1, 2012
Conductive deafness, caused by outer or middle ear obstruction, may be corrected, whereas sensori... more Conductive deafness, caused by outer or middle ear obstruction, may be corrected, whereas sensorineural deafness cannot. Most deafness in dogs is congenital sensorineural hereditary deafness, associated with the genes for white pigment: piebald or merle. The genetic cause has not yet been identified. Dogs with blue eyes have a greater likelihood of hereditary deafness than brown-eyed dogs. Other common forms of sensorineural deafness include presbycusis, ototoxicity, noise-induced hearing loss, otitis interna, and anesthesia. Definitive diagnosis of deafness requires brainstem auditory evoked response testing.
BackgroundThe Dogo Argentino dog breed is affected by hereditary congenital sensorineural deafnes... more BackgroundThe Dogo Argentino dog breed is affected by hereditary congenital sensorineural deafness (CSD) associated with white pigmentation, but prevalence data and associations with phenotypes have not been reported.MethodsIn a retrospective study, animals were tested by the brainstem auditory evoked response, and phenotype data of sex, iris color, patch presence/absence and parent hearing status were collected. Chi‐square analyses were performed to identify associations between deafness and phenotype traits.ResultsBAER results and phenotype data were collected for 811 dogs. Hearing status was 74.23% bilaterally hearing, 20.35% unilaterally deaf and 5.43% bilaterally deaf or an overall prevalence of 25.77%. CSD was not associated with sex, but dogs without a patch had a significantly higher prevalence rate than patched dogs. Blue‐eyed dogs had higher prevalence rates than brown‐eyed dogs, but because of small sample size the χ2 association was not considered valid. Insufficient numbers of dogs with a unilaterally deaf parent were present to assess the effects of parent hearing status.ConclusionApproximately one fourth of a US Dogo Argentino population was deaf in one or both ears, but dogs with a patch had a lower prevalence. Dogs with a blue eye were more likely to be deaf, but the association significance could not be reliably assessed.
This chapter on living with a deaf dog or cat discusses topics on behaviour of deaf animals; hand... more This chapter on living with a deaf dog or cat discusses topics on behaviour of deaf animals; hand signal training; and counselling for owners and breeders of deaf animals.
Congenital deafness associated with white pigmentation has become a widely recognised disorder in... more Congenital deafness associated with white pigmentation has become a widely recognised disorder in dogs and cats, described in the dog at least as early as 1896 (Strain, 1996). The same condition is recognised in a variety of other domestic species, including pigs, cattle and horses. In most dog and cat breeds, the deafness is of the cochleosaccular or Schiebe type, where a sequence is followed of degeneration of the stria vascularis, death of organ of Corti hair cells, collapse of Reissner’s membrane and the cochlear duct and secondary loss of spiral ganglion cells, whose axons form the auditory branch of the eighth cranial nerve (Coppens et al., 2003). Deafness that is not associated with genes for white is of the neuroepithelial type, where hair cells degenerate without preceding injury to the stria; this form is much less common. The initial degeneration of the stria in the cochleosaccular type is linked to the absence or dysfunction of melanocytes in the stria following migration of melanocyte precursors from the neural crest. Strial melanocytes maintain the ionic composition of endolymph and, in their absence, the stria atrophies, leading to hair cell death (Steel and Barkway, 1989; Steel, 1995; Coppens et al., 2003). Serious efforts to assess the prevalence of deafness in dog breeds began in the early 1990s (Holliday et al., 1992; Strain et al., 1992) and have continued (Strain, 2004; Wood et al., 2004; Platt et al., 2006; Strain et al., 2009), including the study in Border Collies by Luisa De Risio and colleagues at the Animal Health Trust, Newmarket, UK, published in this issue of The Veterinary Journal (De Risio et al., 2011). The prevalence of deafness in dog breeds in the USA ranges from 30% (unilateral and bilateral deafness) in Dalmatians to 1.3% in colored Bull Terriers (Strain, 2004). Studies correlating deafness with phenotypic traits have confirmed a variety of associations, while disproving others. Congenital deafness has been reported in 90 breeds of dogs (Strain, 2010); in most breeds, deafness is associated with white pigmentation of skin and hair, which is linked in turn to the piebald and/or merle genes. These genes suppress melanocytes, producing white skin and hair, as well as being responsible for strial degeneration. The genes often also produce blue irises as a consequence of the absence of melanin in the iris. Significant associations between the absence of iris pigment and deafness have been demonstrated for several breeds with the piebald gene (Strain, 2004). Since not all dogs with piebald are deaf or have blue eyes, it can be argued that this variable outcome is the consequence of incomplete penetrance of a causative gene, or that one or more additional genes regulate the expression of the pigment gene. Support for the latter is suggested by the condition in which strong gene expression results in blue eyes and deafness, whereas weak expression results in the failure of the piebald gene to suppress melanocytes in areas of normally white skin, as seen in Dalmatians born with
This chapter on the physiology of the auditory system discusses the divisions of the ear; sound l... more This chapter on the physiology of the auditory system discusses the divisions of the ear; sound localization and central projections in dogs and cats.
1. Anatomy of the Auditory System Anatomy of the External Ear Anatomy of the Middle Ear Anatomy o... more 1. Anatomy of the Auditory System Anatomy of the External Ear Anatomy of the Middle Ear Anatomy of the Inner Ear Development of the Ear Blood Supply of the Ear Innervation of the Ear 2. Physiology of the Auditory System Sound Divisions of the Ear The Cochlea The Organ of Corti Cochlear Information Processing Sound Localization Central Projections 3. Forms and Mechanisms of Deafness Unilateral vs. Bilateral Deafness Partial vs. Total Deafness Syndromic vs. Non-syndromic Deafness Peripheral vs. Central Deafness Forms of Peripheral Deafness Other Forms of Hearing Disturbance Treatment of Deafness 4. Hereditary Deafness Dogs, Cats 5. Later Onset Deafness Ototoxicity Presbycusis Noise Trauma Anesthesia-associated Deafness Conduction Deafness 6. Brainstem Auditory Evoked Response (BAER) Biophysics of BAER Recordings Overview of the BAER Extrinsic Factors Affecting the BAER Intrinsic Factors Affecting the BAER Clinical Applications of the BAER 7. Other Tests of Auditory Function Endocochlear Potential Cochlear Microphonic and Summating Potential Electrocochleogram Acoustic Impedance, Tympanometry and the Acoustic Reflex Middle and Long Latency Evoked Responses Distortion Product Otoacoustic Emissions 8. Living with a Deaf Dog or Cat Behaviour of Deaf Animals Hand Signal Training Counselling For Owners/Breeders of Deaf Animal.
Summary: No influences of chronic cerebellar stimulation were found in 10 different controlled ex... more Summary: No influences of chronic cerebellar stimulation were found in 10 different controlled experiments in 5 different monkeys with chronic alumina‐induced psychomotor seizures. The stimulation paramétérs used were comparable to those used in human epileptics, and continuous daily EEG and behavioral monitoring allowed all seizures to be measured for daily frequency and duration over the several weeks of the experiments. Nocturnal seizures were similarly quantified in 3 monkeys to verify that cerebellar stimulation did not affect them. Motor cortex potentials evoked by cerebellar pulses confirmed that the stimulations were activating the cerebellum throughout the experiments, and measures of electrode access resistance and impedance verified that the electrodes remained in contact with the cerebellum. In one monkey given phenobarbital medication, interictal morbid behavior appeared to be improved by chronic stimulation of either cerebellum or dorsolateral frontal cortex, thus indicating an arousal influence of brain stimulation not due to cerebellum per se.RÉSUMÉAucun effet de la stimulation cérébelleuse chronique n'a pu être observé au cours de 10 expearimentations différentes effectuées chez 5 singes présentant de façon chronique des crises psychomotrices induites par L';alumine. Les conditions de stimulation étaient tout à fait comparables à celles utilisées chez les malades épileptiques; durant les quelques semaines de L';expérimentation une étude diurne continue de L';E.E.G. et du comportement des animaux permit d'enregistrer I'ensemble des crises diurnes et d'en précisr la fréquence et la durée. Les crises nocturnes ont étéétudiées de la même façon chez 3 singes afin de vérifier que la stimulatìon cérébelleuse n'agissait pas sur elles. Les potentiels évoqués au niveau du cortex moteur par les stimulations cérébelleuses confirment que celles‐ci activaient effectivement le cervelet dur‐ant toute la durée des expérimentations; des mesures de la résitance et de L';impédance d'entrée des électrodes permettaient de vérifier que celles‐ci restaient bien en contact avec le cervelet. Chez un singe recev‐ant du phénobarbital, le comportement intercritique a été amélioré aussi bien par la stimulation chronique du cervelet que par celle du cortex frontal dorso‐latéral; ceci traduit L';obtention d'un effet d'éveil par la stimulation cérébrale non liée directement au cervelet lui‐même.RESUMENLa estimulación cerebelosa crónica no tuvo influencia en diez experimentos controlados diferentes llevados a cabo en cinco monos con crisis psicomotoras crónicas inducidas con alúmina. Los parámetros de estimulación fueron comparables a los que se utilizan en seres humanos con epilepsyía ye se monítorizó de modo continuo tanto la frecuencia como la duratión de todas las crisis durante las varias semanas que duraron los experimentos. Egta monitorización incluyó observatión del EEG y de la conducta. Las crisis nocturnas fueron también cuantificadas en tres monos verificando que la estimulación cerebelosa no las modified. Potenciales evocados en la corteza motora por medio de pulsos cerebelosos confirmaron que las estimulaciones activaron el cerebelo a todo lo largo de los experimentos y la medición de la resistencia y de la impedancia de los electrodos evidenció que esos electrodos estaban en contacto con el cerebelo. En un mono al que se le administró fenobarbital, se notó una mejoria en su conducta inter‐ictal tanto cuando se estimuló de modo crónico el cerebelo como la corteza frontal dorso‐lateral. Esto indicó que la influencia del alertamiento cerebral por estimulación no se debía al cerebelo “per se”.ZUSAMMENFASSUNGIn 10 unterschiedlich kontrollierten Experimenten bei 5 verschiedenen Affen mit chronischen Aluminium‐induzierten psychomotorischen Anfällen konnte kein Einfluß der chronischen zerebellären Stimulation gefunden werden. Die Parameter der Stimulation waren vergleichbar mit denen, die bei Patienten mit Epilepsie angewendet werden; kon‐tinuierliches Monitoring des EEG und des Verhaltens erlaubte es, alle Krämpfe hinsichtlich Häufigkeit und Dauer während mehrerer Wochen des Experiments aufzuzeichnen. Nächtliche Krämpfe wurden ebenfalls bei 3 Affen quantifiziert und nachgewiesen, daß die zerebelläre Stimulation sie nicht beeinträchtigte. Die motorischen Cortexpotentiale, die durch zerebelläre Stimulation hervorgerufen werden, bestätigen, daß die Stimulationen das Zerebellum während der Experimente aktivierte; Untersuchungen des Elektrodenwiderstands und der Impedanz bestätigten, daß die Elektroden mit dem Zerebellum im Kontakt blieben. Bei einem Affen unter Phenobarbitalmedika‐tion schien das interiktale Verhalten sowohl durch chronische Stimulierung des Zerebellums wie des dor‐solateralen frontalen Cortex gebessert. Das deutet darauf hin, daß ein Einfluß der Hirnstimulation auf das Arousal nicht speziell dem Zerebellum zukommt.
Veterinary Clinics of North America-small Animal Practice, Jul 1, 1999
Congenital deafness in dogs and cats is primarily of the hereditary sensorineural form associated... more Congenital deafness in dogs and cats is primarily of the hereditary sensorineural form associated with white pigmentation genes, although acquired forms of deafness are possible. Highest prevalence is seen in white cats, especially those with blue eyes, and the Dalmatian, with many other dog breeds affected to some extent. This deafness results from degeneration of the cochlear blood supply at age 3-4 weeks, presumably resulting from suppression of melanocytes by the white (cat) or merle or piebald (dog) genes. Mechanism of inheritance is not understood for most breeds. Such animals should not be bred and may present liabilities for their owners. Objective diagnosis of deafness, especially when unilateral, relies on the brainstem auditory evoked response, an electrodiagnostic test where electrical activity in response to a click stimulus is recorded from the scalp using needle electrodes and a special purpose computer. Client counseling guidelines are presented.
Pigment-associated deafness is a common hereditary condition in a range of dog breeds. The aim of... more Pigment-associated deafness is a common hereditary condition in a range of dog breeds. The aim of this study was to perform a genome-wide association analysis to investigate the genetic architecture of deafness in Australian Cattle Dogs. Genotypes for 104 757 polymorphisms in 216 dogs were available for analyses after quality control. A genomic relationship matrix was used in the mixed model analyses to account for polygenic effects, as we tested each polymorphism for its association with deafness, in a case/control experimental design. Three approaches were used to code the genotypes and test for additive, recessive and dominant SNP effects. The genome-wide association study analyses identified a clear association peak on CFA20, with the most significant SNPs on this chromosome (1.29 × 10-4 ) in the vicinity of MITF. Variants in MITF have been associated with white pigmentation in dogs and with deafness in humans and other species, supporting the premise that canine deafness is associated with variants in or near this gene. A recessive inheritance for the peak in CFA20 is possible given the significant results in the recessive model; however, the estimated heritability was low (4.54 × 10-5 ). Further validation, identification of variants and testing in other dog breeds are needed.
A seizure disorder of 4.5 years' duration in a 6-year-old female Nubian goat was diagnosed as par... more A seizure disorder of 4.5 years' duration in a 6-year-old female Nubian goat was diagnosed as partial epilepsy on the basis of history, focal electroencephalogram (EEG) abnormalities, convulsive response to ketamine, and necropsy findings. The goat appeared to maintain consciousness during her seizures. A 1.5-day period of continuous seizures during a pregnancy at age 1.5 years may have resulted in a postanoxic seizure focus responsible for the seizures. A morphologic cause for the seizures was not detected. Two spontaneous seizures and 2 drug-induced seizures were detected during 1 month of observation after donation. The amplitude of the EEG over the left frontocentral cortex was depressed, and periodic bursts of high-frequency interictal spiking were detected over the same site. Acepromazine, intermittent photic stimulation, or ketamine after acepromazine failed to elicit seizures or EEG abnormalities, but ketamine alone (50 mg, IV) twice elicited seizures. Seizure severity appeared to parallel plasma estrogen concentration.
Determinations were made by laser nephelometry of serum and CSF immunoglobulin (Ig) G concentrati... more Determinations were made by laser nephelometry of serum and CSF immunoglobulin (Ig) G concentrations in Suffolk sheep with naturally occurring scrapie. The serum IgG concentrations in 3 sheep with confirmed or suspected scrapie were between 2,140 and 3,290 mg of IgG/100 ml, and the CSF values were between less than 10 and 75 mg of IgG/100 ml. In 8 clinically healthy (control) sheep, serum IgG concentrations were 2,647 to 7,380 mg/100 ml and CSF IgG concentrations were between 0 (undetectable) and 162 mg/100 ml. A sheep with pulmonary adenomatosis had 1,445 mg of IgG/100 ml of serum. The results indicated that neither serum nor CSF IgG concentrations were increased in sheep with naturally occurring infection with scrapie and that the severity of the disease did not correspond with the IgG concentration.
Recordings of visual-evoked potentials that were induced by flashes of white light were obtained ... more Recordings of visual-evoked potentials that were induced by flashes of white light were obtained from 13 Beagle pups to document the development of the response from age 7 to 100 days. Responses were recorded between needle electrodes placed on the nuchal crest and the interorbital line, with ground at the vertex. Five alternating positive (P) and negative (N) peaks were observed in most visual-evoked potentials: P1, N1, P2, N2, and P3. Responses were recorded from 2 pups prior to opening of the eyelids. Recordings were performed without sedation or dark adaptation. Peak latencies were essentially mature (equal to those of adult dogs) by day 11 for P1, and by day 38 for N1 and P2. The latencies to N2 and P3 did not reach adult values by day 100, but did reach plateau values by day 43. The P1-N1 amplitude measurements reached mature levels by day 14, whereas N1-P2 amplitudes were mature by day 32. The P2-N2 and N2-P3 amplitudes reached plateaus that greatly exceeded adult amplitudes by days 50 and 58, respectively. Maturation of visual-evoked potential responses paralleled reported morphologic development of the visual cortex. All of the measured latency and amplitude values had significant (P less than or equal to 0.004) linear regression lines of latency vs age or amplitude vs age.
Electroencephalogram (EEG), brain stem auditory-evoked potential, and flash visual-evoked potenti... more Electroencephalogram (EEG), brain stem auditory-evoked potential, and flash visual-evoked potential recordings were taken from healthy sheep and from 3 sheep with scrapie, a CNS slow virus infection. The EEG changes included semi-periodic, polyphasic, high-voltage sharp waves (bilaterally synchronous and symmetric in all channels), and a cyclic alternating pattern consisting of a high-voltage low-frequency phase, followed by a low-voltage high-frequency phase. The high-voltage phase occurred with increased arousal, and the low-voltage phase occurred with decreased arousal. Myoclonic jerks were coincident with EEG sharp waves in one sheep with scrapie. Several spontaneous focal seizures were observed. Wave-form amplitudes were greatly reduced in the brain stem auditory-evoked potential and flash visual-evoked potential; degree of reduction did not always correlate with disease severity. The EEG and evoked potential changes were seen in an exposed sheep that had not yet developed clinical signs of scrapie.
Recordings of averaged brain stem auditory-evoked potentials were obtained from 13 Beagle pups of... more Recordings of averaged brain stem auditory-evoked potentials were obtained from 13 Beagle pups of both genders to document the postnatal development of the response from age 1 to 76 days. Responses were recorded between needle electrodes placed on the vertex and the ipsilateral ear, with ground at the interorbital line. Recordings were performed without sedation. Low-amplitude responses to high-intensity stimuli could be recorded from animals prior to opening of the ear canals. Peak latencies did not change after day 20 for peak I, day 30 for peaks II and III, and day 40 for peak V. As a result, the interpeak latencies between peaks I and III did not change after day 30, but continued to decrease until day 40 for peaks III-V and I-V. Peak amplitudes reached plateau values by day 20 (peak I) or day 30 (peaks II, III, and V). All of the measured latency and amplitude values had significant (P less than 0.001) linear regression lines of latency vs age and amplitude vs age. The brain stem auditory-evoked potential thresholds were mature by day 20.
Veterinary Clinics of North America-small Animal Practice, Nov 1, 2012
Conductive deafness, caused by outer or middle ear obstruction, may be corrected, whereas sensori... more Conductive deafness, caused by outer or middle ear obstruction, may be corrected, whereas sensorineural deafness cannot. Most deafness in dogs is congenital sensorineural hereditary deafness, associated with the genes for white pigment: piebald or merle. The genetic cause has not yet been identified. Dogs with blue eyes have a greater likelihood of hereditary deafness than brown-eyed dogs. Other common forms of sensorineural deafness include presbycusis, ototoxicity, noise-induced hearing loss, otitis interna, and anesthesia. Definitive diagnosis of deafness requires brainstem auditory evoked response testing.
BackgroundThe Dogo Argentino dog breed is affected by hereditary congenital sensorineural deafnes... more BackgroundThe Dogo Argentino dog breed is affected by hereditary congenital sensorineural deafness (CSD) associated with white pigmentation, but prevalence data and associations with phenotypes have not been reported.MethodsIn a retrospective study, animals were tested by the brainstem auditory evoked response, and phenotype data of sex, iris color, patch presence/absence and parent hearing status were collected. Chi‐square analyses were performed to identify associations between deafness and phenotype traits.ResultsBAER results and phenotype data were collected for 811 dogs. Hearing status was 74.23% bilaterally hearing, 20.35% unilaterally deaf and 5.43% bilaterally deaf or an overall prevalence of 25.77%. CSD was not associated with sex, but dogs without a patch had a significantly higher prevalence rate than patched dogs. Blue‐eyed dogs had higher prevalence rates than brown‐eyed dogs, but because of small sample size the χ2 association was not considered valid. Insufficient numbers of dogs with a unilaterally deaf parent were present to assess the effects of parent hearing status.ConclusionApproximately one fourth of a US Dogo Argentino population was deaf in one or both ears, but dogs with a patch had a lower prevalence. Dogs with a blue eye were more likely to be deaf, but the association significance could not be reliably assessed.
This chapter on living with a deaf dog or cat discusses topics on behaviour of deaf animals; hand... more This chapter on living with a deaf dog or cat discusses topics on behaviour of deaf animals; hand signal training; and counselling for owners and breeders of deaf animals.
Congenital deafness associated with white pigmentation has become a widely recognised disorder in... more Congenital deafness associated with white pigmentation has become a widely recognised disorder in dogs and cats, described in the dog at least as early as 1896 (Strain, 1996). The same condition is recognised in a variety of other domestic species, including pigs, cattle and horses. In most dog and cat breeds, the deafness is of the cochleosaccular or Schiebe type, where a sequence is followed of degeneration of the stria vascularis, death of organ of Corti hair cells, collapse of Reissner’s membrane and the cochlear duct and secondary loss of spiral ganglion cells, whose axons form the auditory branch of the eighth cranial nerve (Coppens et al., 2003). Deafness that is not associated with genes for white is of the neuroepithelial type, where hair cells degenerate without preceding injury to the stria; this form is much less common. The initial degeneration of the stria in the cochleosaccular type is linked to the absence or dysfunction of melanocytes in the stria following migration of melanocyte precursors from the neural crest. Strial melanocytes maintain the ionic composition of endolymph and, in their absence, the stria atrophies, leading to hair cell death (Steel and Barkway, 1989; Steel, 1995; Coppens et al., 2003). Serious efforts to assess the prevalence of deafness in dog breeds began in the early 1990s (Holliday et al., 1992; Strain et al., 1992) and have continued (Strain, 2004; Wood et al., 2004; Platt et al., 2006; Strain et al., 2009), including the study in Border Collies by Luisa De Risio and colleagues at the Animal Health Trust, Newmarket, UK, published in this issue of The Veterinary Journal (De Risio et al., 2011). The prevalence of deafness in dog breeds in the USA ranges from 30% (unilateral and bilateral deafness) in Dalmatians to 1.3% in colored Bull Terriers (Strain, 2004). Studies correlating deafness with phenotypic traits have confirmed a variety of associations, while disproving others. Congenital deafness has been reported in 90 breeds of dogs (Strain, 2010); in most breeds, deafness is associated with white pigmentation of skin and hair, which is linked in turn to the piebald and/or merle genes. These genes suppress melanocytes, producing white skin and hair, as well as being responsible for strial degeneration. The genes often also produce blue irises as a consequence of the absence of melanin in the iris. Significant associations between the absence of iris pigment and deafness have been demonstrated for several breeds with the piebald gene (Strain, 2004). Since not all dogs with piebald are deaf or have blue eyes, it can be argued that this variable outcome is the consequence of incomplete penetrance of a causative gene, or that one or more additional genes regulate the expression of the pigment gene. Support for the latter is suggested by the condition in which strong gene expression results in blue eyes and deafness, whereas weak expression results in the failure of the piebald gene to suppress melanocytes in areas of normally white skin, as seen in Dalmatians born with
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Papers by George M Strain