Joe Mayhew | Massey University (original) (raw)
Papers by Joe Mayhew
Equine Veterinary Education, 1989
The Journal of Physiology, 1999
Veterinary and Comparative Orthopaedics and Traumatology, 2018
Objective This article aims to report the medium-term clinical outcome and assess persistence of ... more Objective This article aims to report the medium-term clinical outcome and assess persistence of enlargement of the lumbosacral lateral intervertebral neurovascular foramen using computed tomography (CT) volumetric analysis in dogs following lateral foraminotomy. Materials Six dogs that underwent lumbosacral lateral foraminotomy on one or both sides were evaluated with CT prior to, immediately postoperatively (n = 2) and at 12 to 44 months of follow-up. Five out of six dogs had successful clinical outcomes with alleviation of pain and increased levels of activity, according to subjective assessment. Immediate postoperative CT volumetric analysis of the lateral intervertebral neurovascular foramina in two dogs indicated a 650 to 800% increase in volume in extension achieved by foraminotomy (four foramens). At subsequent follow-up, bone regrowth had occurred with reduction in foraminal volume, though in both dogs foraminal volume remained higher than preoperative values. Follow-up CT ...
Acta Neuropathologica, 2001
Equine grass sickness (EGS) is an acquired disease of unknown aetiology affecting horses kept at ... more Equine grass sickness (EGS) is an acquired disease of unknown aetiology affecting horses kept at grass. The disease is characterised by postganglionic sympathetic and parasympathetic neuronal pathology and is categorised as a dysautonomia. This study undertook a systematic examination of brain stem cranial nerve nuclei in 59 cases of EGS. Pathology consisting of neuronal chromatolysis was most consistently noted in the lower motor neurons of the general visceral efferent nucleus of CN III and X and the general somatic efferent nuclei of CN III, V, VII and XII. The prevalence of chromatolysis differed significantly between the diagnostic categories and was inversely related to the age of the animal. Duration of disease had a small but significant negative effect on the proportion of nuclei with chromatolytic neurons in chronic cases. The distribution of chromatolytic neurons is unlike that reported in any other equine or human disease; however, it appears to be equivalent to that in other animals with primary dysautonomias. EGS should be classified as a multisystem disease.
Equine Veterinary Education, 1990
SUMMARY From a neurological point of view the evaluation of horses suffering from urination disor... more SUMMARY From a neurological point of view the evaluation of horses suffering from urination disorders and abnormalities of erection and ejaculation must include a thorough neurological evaluation. Some consideration should be given to the use of diagnostic aids. The case presented on p62 emphasises that careful and sensible management is more likely to be effective, compared to the random use of adrenergic and cholinergic agonists and antagonists. However, some consideration should be given to the probable innervation of the bladder (Fig 1), if the use of pharmacological agents is to be attempted.
Equine Veterinary Education, 2009
The accompanying Case Report (Muno et al. 2009) on cervical vertebral fracture in a Thoroughbred ... more The accompanying Case Report (Muno et al. 2009) on cervical vertebral fracture in a Thoroughbred filly introduces the case by stating "Trauma resulting in neurological dysfunction is relatively common in horses". Although many practitioners would tend to agree, such cases are probably not as frequent as colic, lameness or respiratory disorders. Notwithstanding, such cases are not always easy to evaluate for appropriate care, which makes the beautifully illustrated Case Report educational and worthy of comment. On reading the report, this author is reminded of several clinical maxims and of the perennial issues of correct terminology so that we can communicate clearly and precisely.
Veterinary surgery : VS, 2017
To determine the effect of dorsal annulectomy and partial discectomy on the volume of the lumbosa... more To determine the effect of dorsal annulectomy and partial discectomy on the volume of the lumbosacral lateral intervertebral neurovascular foramina (intervertebral foramina) in canine cadavers during extension of the lumbosacral junction. Ex vivo experiment. Lumbosacral specimens from 10 large breed dogs euthanatized for reasons unrelated to lumbosacral disease. The lumbosacral specimens were clamped in a wooden jig and scanned using computed tomography (CT) with the lumbosacral junction in a neutral position and loaded in extension using a tensioning device. The 3-dimensional volumes of the lumbosacral intervertebral neurovascular foramina were measured and the extent of any disc degeneration was determined from the CT data. A limited dorsal laminectomy of S1 and a dorsal LS annulectomy and partial discectomy were then performed. The lumbosacral specimens were remounted into the jig and loaded into extension at the same tension and were re-scanned. Measurements of intervertebral fo...
Veterinary surgery : VS, 2017
To develop a computed tomographic (CT) method to measure the volume of the lumbosacral interverte... more To develop a computed tomographic (CT) method to measure the volume of the lumbosacral intervertebral neurovascular foramina (IVF) in dogs, and determine the effect of the range of motion of the lumbosacral (LS) junction on this measurement in German shepherd dogs (GSDs) with degenerative lumbosacral stenosis (DLSS) compared to unaffected controls. In vivo analysis and retrospective case series. Twenty-four working Police GSDs, 12 diagnosed with DLSS and 12 unaffected by DLSS were compared to 10 Greyhounds without DLSS. Three-dimensional renderings of CT data were used to measure the lumbosacral foraminal volume of dogs positioned in dorsal recumbency with the LS junction alternately positioned in extension, neutral position, and flexion. Volumetric analysis of the IVF was found repeatable for the extended and neutral positions (interclass correlation coefficient of 0.89 and 0.8, respectively). The mean lumbosacral IVF volume was decreased by 74% between LS flexion and extension in ...
Veterinary Record, 2005
Cases so far are typically in the age range of nine to 15 months, but farmers have commented that... more Cases so far are typically in the age range of nine to 15 months, but farmers have commented that the earliest signs have been noted as young as six months old. The signs first noted by the owners are usually the development of an unusual gait. Clinical signs usually have been ...
In Practice, 1995
POLYNEURITIS EQUI has been previously described as neuritis of the cauda equina, due to an appare... more POLYNEURITIS EQUI has been previously described as neuritis of the cauda equina, due to an apparent predisposition for involvement of the extradural nerve roots of the cauda equina. However, the term polyneuritis equi more adequately reflects the more diffuse ...
Equine Respiratory Medicine and Surgery, 1983
Idiopathic Recurrent Laryngeal Neuropathy: Etiopathogenesis Caroline Hahn and Joe Mayhew Introduc... more Idiopathic Recurrent Laryngeal Neuropathy: Etiopathogenesis Caroline Hahn and Joe Mayhew Introduction Idiopathic recurrent laryngeal neuropathy (RLN) is a prominent disease of domestic horses that is character-ized by the distal degeneration of axons in the recurrent ...
Equine Veterinary Education, 1993
The Veterinary Journal, 2012
The study on trigeminal reflex testing in horses described by Dr. Kata Veres-Nyéki of the Vetsuis... more The study on trigeminal reflex testing in horses described by Dr. Kata Veres-Nyéki of the Vetsuisse-Faculty at the University of Berne and colleagues, published in this issue of The Veterinary Journal, is a welcome contribution in attempting to objectively measure the apparent neuropathic aberrations seen as the ubiquitous and enigmatic syndrome of headshaking that frustrates owners and veterinary surgeons (and certainly horses!) world-wide (Veres-Nyék et al., 2011). Watching horses headshaking certainly gives one the impression that there must be some altered stimulation being received by the patient from the rostral head region. It is thus tempting to suggest that such stimuli are at least annoying and most likely are painful to the horse, making comparison with painful conditions in humans warranted. Such conditions include trigeminal neuralgia, trigeminal neuritis, post-herpetic neuralgia, cluster headaches, focal tension headaches, intractable paroxysmal sneezing, exercise associated rhinitis and allergic rhinitis. This begs the question as to whether or not one can demonstrate gain in somatic or visceral afferent function and if so whether this may be categorised as inflammatory or neuropathic pain or even some other, as yet non-defined, functional aberration. The pertinence of the study by Veres-Nyék et al. (2011) is thus obvious. Wisely, the authors are cautious in indicating what (if any) relevance the procedure may have in unravelling any differences present in headshakers. Determining subtle electrophysiological abnormalities in patients when there is no permanent, morbid, pathological lesion currently identifiable, as appears to be the case with headshaking, is thwart with problems. To undertake such conduction testing in the non-sedated, relaxed state is a good start, although without full patient compliance, attaining an actual resting state, or perhaps a preferred active state, to test neural pathways is always problematic with animals. Electrophysiological conduction parameters are robust ways of characterising the functional integrity of neural pathways. This is best done in standardised conditions when one can place the stimulator (electrical, auditory, magnetic, visual etc.) on or near appropriate receptors and place recording electrodes on a distant relay site or target organ, with a single anatomical pathway connecting them. To help determine that this pathway is precisely defined one should functionally block (anaesthetise) or cut the path at various sites to modify or obliterate the conduction appropriately (Anor et al., 1999). Obviously with peripheral structures (nerves) one is reasonably (but not absolutely) sure of such a pathway, but when involving the CNS, many modifying, interconnecting pathways and mechanisms can come into play, altering the
Equine Veterinary Education - EQUINE VET EDUC, 1990
Journal of the American Veterinary Medical Association, 2010
Objective—To compare signalment of horses with cervical vertebral malformation-malarticulation (C... more Objective—To compare signalment of horses with cervical vertebral malformation-malarticulation (CVM) with that of control horses and to describe results of clinical examination, diagnostic imaging and necropsy findings, and reported outcome in horses with CVM. Design—Retrospective case-control study. Animals—270 horses with CVM and 608 control horses admitted to 6 veterinary hospitals from 1992 through 2007. Procedures—Medical records of participating hospitals were reviewed to identify horses with CVM (ie, case horses) and contemporaneous control (non-CVM-affected) horses that were admitted for treatment. Signalment was compared between case horses and control horses. Results of clinical examination, laboratory and diagnostic imaging findings, necropsy results, and outcome were assessed for horses with CVM. Results—Case horses were younger (median age, 2 years) than were control horses (median age, 7 years). Thoroughbreds, warmbloods, and Tennessee Walking Horses were overrepresent...
Journal of Equine Veterinary Science, 2000
Clinical Techniques in Equine Practice, 2006
As our understanding of equine diseases has rapidly grown, studies have been published that allow... more As our understanding of equine diseases has rapidly grown, studies have been published that allow clinicians to take an evidence-based approach in daily practice, allowing a more accurate diagnosis of cervical vertebral compressive myelopathy (CVCM). However, the equine ...
Equine Veterinary Journal, 2010
Evaluation of horses for eye problems and for suspected impairment of visual acuity often require... more Evaluation of horses for eye problems and for suspected impairment of visual acuity often requires a thorough neuroophthalmic examination to be conducted. Along with a full ophthalmic evaluation, the results of such an examination should indicate the likely site of any lesion(s) accounting for blindness, miosis, mydriasis, anisocoria, Horner's syndrome, strabismus, facial paralysis and facial spasm, nystagmus and other signs of vestibular disease, and cerebellar disorders, that may be present. Such a thorough examination with guidance for correct interpretation of findings is given here.
Equine Veterinary Education - EQUINE VET EDUC, 1993
PAIN, 2007
Laminitis is a common debilitating disease in horses that involves painful disruption of the lame... more Laminitis is a common debilitating disease in horses that involves painful disruption of the lamellar dermo-epidermal junction within the hoof. This condition is often refractory to conventional anti-inflammatory analgesia and results in unremitting pain, which in severe cases requires euthanasia. The mechanisms underlying pain in laminitis were investigated using quantification of behavioural pain indicators in conjunction with histological studies of peripheral nerves innervating the hoof. Laminitic horses displayed consistently altered or abnormal behaviours such as increased forelimb lifting and an increased proportion of time spent at the back of the box compared to normal horses. Electron micrographic analysis of the digital nerve of laminitic horses showed peripheral nerve morphology to be abnormal, as well as having reduced numbers of unmyelinated (43.2%) and myelinated fibers (34.6%) compared to normal horses. Sensory nerve cell bodies innervating the hoof, in cervical, C8 dorsal root ganglia (DRG), showed an upregulated expression of the neuronal injury marker, activating transcription factor-3 (ATF3) in both large NF-200-immunopositive neurons and small neurons that were either peripherin-or IB4-positive. A significantly increased expression of neuropeptide Y (NPY) was also observed in myelinated afferent neurons. These changes are similar to those reported in other neuropathic pain states and were not observed in the C4 DRG of laminitic horses, which is not associated with innervation of the forelimb. This study provides novel evidence for a neuropathic component to the chronic pain state associated with equine laminitis, indicating that anti-neuropathic analgesic treatment may well have a role in the management of this condition.
Equine Veterinary Education, 1989
The Journal of Physiology, 1999
Veterinary and Comparative Orthopaedics and Traumatology, 2018
Objective This article aims to report the medium-term clinical outcome and assess persistence of ... more Objective This article aims to report the medium-term clinical outcome and assess persistence of enlargement of the lumbosacral lateral intervertebral neurovascular foramen using computed tomography (CT) volumetric analysis in dogs following lateral foraminotomy. Materials Six dogs that underwent lumbosacral lateral foraminotomy on one or both sides were evaluated with CT prior to, immediately postoperatively (n = 2) and at 12 to 44 months of follow-up. Five out of six dogs had successful clinical outcomes with alleviation of pain and increased levels of activity, according to subjective assessment. Immediate postoperative CT volumetric analysis of the lateral intervertebral neurovascular foramina in two dogs indicated a 650 to 800% increase in volume in extension achieved by foraminotomy (four foramens). At subsequent follow-up, bone regrowth had occurred with reduction in foraminal volume, though in both dogs foraminal volume remained higher than preoperative values. Follow-up CT ...
Acta Neuropathologica, 2001
Equine grass sickness (EGS) is an acquired disease of unknown aetiology affecting horses kept at ... more Equine grass sickness (EGS) is an acquired disease of unknown aetiology affecting horses kept at grass. The disease is characterised by postganglionic sympathetic and parasympathetic neuronal pathology and is categorised as a dysautonomia. This study undertook a systematic examination of brain stem cranial nerve nuclei in 59 cases of EGS. Pathology consisting of neuronal chromatolysis was most consistently noted in the lower motor neurons of the general visceral efferent nucleus of CN III and X and the general somatic efferent nuclei of CN III, V, VII and XII. The prevalence of chromatolysis differed significantly between the diagnostic categories and was inversely related to the age of the animal. Duration of disease had a small but significant negative effect on the proportion of nuclei with chromatolytic neurons in chronic cases. The distribution of chromatolytic neurons is unlike that reported in any other equine or human disease; however, it appears to be equivalent to that in other animals with primary dysautonomias. EGS should be classified as a multisystem disease.
Equine Veterinary Education, 1990
SUMMARY From a neurological point of view the evaluation of horses suffering from urination disor... more SUMMARY From a neurological point of view the evaluation of horses suffering from urination disorders and abnormalities of erection and ejaculation must include a thorough neurological evaluation. Some consideration should be given to the use of diagnostic aids. The case presented on p62 emphasises that careful and sensible management is more likely to be effective, compared to the random use of adrenergic and cholinergic agonists and antagonists. However, some consideration should be given to the probable innervation of the bladder (Fig 1), if the use of pharmacological agents is to be attempted.
Equine Veterinary Education, 2009
The accompanying Case Report (Muno et al. 2009) on cervical vertebral fracture in a Thoroughbred ... more The accompanying Case Report (Muno et al. 2009) on cervical vertebral fracture in a Thoroughbred filly introduces the case by stating "Trauma resulting in neurological dysfunction is relatively common in horses". Although many practitioners would tend to agree, such cases are probably not as frequent as colic, lameness or respiratory disorders. Notwithstanding, such cases are not always easy to evaluate for appropriate care, which makes the beautifully illustrated Case Report educational and worthy of comment. On reading the report, this author is reminded of several clinical maxims and of the perennial issues of correct terminology so that we can communicate clearly and precisely.
Veterinary surgery : VS, 2017
To determine the effect of dorsal annulectomy and partial discectomy on the volume of the lumbosa... more To determine the effect of dorsal annulectomy and partial discectomy on the volume of the lumbosacral lateral intervertebral neurovascular foramina (intervertebral foramina) in canine cadavers during extension of the lumbosacral junction. Ex vivo experiment. Lumbosacral specimens from 10 large breed dogs euthanatized for reasons unrelated to lumbosacral disease. The lumbosacral specimens were clamped in a wooden jig and scanned using computed tomography (CT) with the lumbosacral junction in a neutral position and loaded in extension using a tensioning device. The 3-dimensional volumes of the lumbosacral intervertebral neurovascular foramina were measured and the extent of any disc degeneration was determined from the CT data. A limited dorsal laminectomy of S1 and a dorsal LS annulectomy and partial discectomy were then performed. The lumbosacral specimens were remounted into the jig and loaded into extension at the same tension and were re-scanned. Measurements of intervertebral fo...
Veterinary surgery : VS, 2017
To develop a computed tomographic (CT) method to measure the volume of the lumbosacral interverte... more To develop a computed tomographic (CT) method to measure the volume of the lumbosacral intervertebral neurovascular foramina (IVF) in dogs, and determine the effect of the range of motion of the lumbosacral (LS) junction on this measurement in German shepherd dogs (GSDs) with degenerative lumbosacral stenosis (DLSS) compared to unaffected controls. In vivo analysis and retrospective case series. Twenty-four working Police GSDs, 12 diagnosed with DLSS and 12 unaffected by DLSS were compared to 10 Greyhounds without DLSS. Three-dimensional renderings of CT data were used to measure the lumbosacral foraminal volume of dogs positioned in dorsal recumbency with the LS junction alternately positioned in extension, neutral position, and flexion. Volumetric analysis of the IVF was found repeatable for the extended and neutral positions (interclass correlation coefficient of 0.89 and 0.8, respectively). The mean lumbosacral IVF volume was decreased by 74% between LS flexion and extension in ...
Veterinary Record, 2005
Cases so far are typically in the age range of nine to 15 months, but farmers have commented that... more Cases so far are typically in the age range of nine to 15 months, but farmers have commented that the earliest signs have been noted as young as six months old. The signs first noted by the owners are usually the development of an unusual gait. Clinical signs usually have been ...
In Practice, 1995
POLYNEURITIS EQUI has been previously described as neuritis of the cauda equina, due to an appare... more POLYNEURITIS EQUI has been previously described as neuritis of the cauda equina, due to an apparent predisposition for involvement of the extradural nerve roots of the cauda equina. However, the term polyneuritis equi more adequately reflects the more diffuse ...
Equine Respiratory Medicine and Surgery, 1983
Idiopathic Recurrent Laryngeal Neuropathy: Etiopathogenesis Caroline Hahn and Joe Mayhew Introduc... more Idiopathic Recurrent Laryngeal Neuropathy: Etiopathogenesis Caroline Hahn and Joe Mayhew Introduction Idiopathic recurrent laryngeal neuropathy (RLN) is a prominent disease of domestic horses that is character-ized by the distal degeneration of axons in the recurrent ...
Equine Veterinary Education, 1993
The Veterinary Journal, 2012
The study on trigeminal reflex testing in horses described by Dr. Kata Veres-Nyéki of the Vetsuis... more The study on trigeminal reflex testing in horses described by Dr. Kata Veres-Nyéki of the Vetsuisse-Faculty at the University of Berne and colleagues, published in this issue of The Veterinary Journal, is a welcome contribution in attempting to objectively measure the apparent neuropathic aberrations seen as the ubiquitous and enigmatic syndrome of headshaking that frustrates owners and veterinary surgeons (and certainly horses!) world-wide (Veres-Nyék et al., 2011). Watching horses headshaking certainly gives one the impression that there must be some altered stimulation being received by the patient from the rostral head region. It is thus tempting to suggest that such stimuli are at least annoying and most likely are painful to the horse, making comparison with painful conditions in humans warranted. Such conditions include trigeminal neuralgia, trigeminal neuritis, post-herpetic neuralgia, cluster headaches, focal tension headaches, intractable paroxysmal sneezing, exercise associated rhinitis and allergic rhinitis. This begs the question as to whether or not one can demonstrate gain in somatic or visceral afferent function and if so whether this may be categorised as inflammatory or neuropathic pain or even some other, as yet non-defined, functional aberration. The pertinence of the study by Veres-Nyék et al. (2011) is thus obvious. Wisely, the authors are cautious in indicating what (if any) relevance the procedure may have in unravelling any differences present in headshakers. Determining subtle electrophysiological abnormalities in patients when there is no permanent, morbid, pathological lesion currently identifiable, as appears to be the case with headshaking, is thwart with problems. To undertake such conduction testing in the non-sedated, relaxed state is a good start, although without full patient compliance, attaining an actual resting state, or perhaps a preferred active state, to test neural pathways is always problematic with animals. Electrophysiological conduction parameters are robust ways of characterising the functional integrity of neural pathways. This is best done in standardised conditions when one can place the stimulator (electrical, auditory, magnetic, visual etc.) on or near appropriate receptors and place recording electrodes on a distant relay site or target organ, with a single anatomical pathway connecting them. To help determine that this pathway is precisely defined one should functionally block (anaesthetise) or cut the path at various sites to modify or obliterate the conduction appropriately (Anor et al., 1999). Obviously with peripheral structures (nerves) one is reasonably (but not absolutely) sure of such a pathway, but when involving the CNS, many modifying, interconnecting pathways and mechanisms can come into play, altering the
Equine Veterinary Education - EQUINE VET EDUC, 1990
Journal of the American Veterinary Medical Association, 2010
Objective—To compare signalment of horses with cervical vertebral malformation-malarticulation (C... more Objective—To compare signalment of horses with cervical vertebral malformation-malarticulation (CVM) with that of control horses and to describe results of clinical examination, diagnostic imaging and necropsy findings, and reported outcome in horses with CVM. Design—Retrospective case-control study. Animals—270 horses with CVM and 608 control horses admitted to 6 veterinary hospitals from 1992 through 2007. Procedures—Medical records of participating hospitals were reviewed to identify horses with CVM (ie, case horses) and contemporaneous control (non-CVM-affected) horses that were admitted for treatment. Signalment was compared between case horses and control horses. Results of clinical examination, laboratory and diagnostic imaging findings, necropsy results, and outcome were assessed for horses with CVM. Results—Case horses were younger (median age, 2 years) than were control horses (median age, 7 years). Thoroughbreds, warmbloods, and Tennessee Walking Horses were overrepresent...
Journal of Equine Veterinary Science, 2000
Clinical Techniques in Equine Practice, 2006
As our understanding of equine diseases has rapidly grown, studies have been published that allow... more As our understanding of equine diseases has rapidly grown, studies have been published that allow clinicians to take an evidence-based approach in daily practice, allowing a more accurate diagnosis of cervical vertebral compressive myelopathy (CVCM). However, the equine ...
Equine Veterinary Journal, 2010
Evaluation of horses for eye problems and for suspected impairment of visual acuity often require... more Evaluation of horses for eye problems and for suspected impairment of visual acuity often requires a thorough neuroophthalmic examination to be conducted. Along with a full ophthalmic evaluation, the results of such an examination should indicate the likely site of any lesion(s) accounting for blindness, miosis, mydriasis, anisocoria, Horner's syndrome, strabismus, facial paralysis and facial spasm, nystagmus and other signs of vestibular disease, and cerebellar disorders, that may be present. Such a thorough examination with guidance for correct interpretation of findings is given here.
Equine Veterinary Education - EQUINE VET EDUC, 1993
PAIN, 2007
Laminitis is a common debilitating disease in horses that involves painful disruption of the lame... more Laminitis is a common debilitating disease in horses that involves painful disruption of the lamellar dermo-epidermal junction within the hoof. This condition is often refractory to conventional anti-inflammatory analgesia and results in unremitting pain, which in severe cases requires euthanasia. The mechanisms underlying pain in laminitis were investigated using quantification of behavioural pain indicators in conjunction with histological studies of peripheral nerves innervating the hoof. Laminitic horses displayed consistently altered or abnormal behaviours such as increased forelimb lifting and an increased proportion of time spent at the back of the box compared to normal horses. Electron micrographic analysis of the digital nerve of laminitic horses showed peripheral nerve morphology to be abnormal, as well as having reduced numbers of unmyelinated (43.2%) and myelinated fibers (34.6%) compared to normal horses. Sensory nerve cell bodies innervating the hoof, in cervical, C8 dorsal root ganglia (DRG), showed an upregulated expression of the neuronal injury marker, activating transcription factor-3 (ATF3) in both large NF-200-immunopositive neurons and small neurons that were either peripherin-or IB4-positive. A significantly increased expression of neuropeptide Y (NPY) was also observed in myelinated afferent neurons. These changes are similar to those reported in other neuropathic pain states and were not observed in the C4 DRG of laminitic horses, which is not associated with innervation of the forelimb. This study provides novel evidence for a neuropathic component to the chronic pain state associated with equine laminitis, indicating that anti-neuropathic analgesic treatment may well have a role in the management of this condition.