Thoracic hemivertebra in a 14-year-old gelding with neurological symptoms

Thoracic hemivertebra in a 14-year-old gelding with neurological symptoms | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 19 February 2026 V1 Latest version Share on Thoracic hemivertebra in a 14-year-old gelding with neurological symptoms Authors : Chantal Blaettler , Thomas Maddox W , Gail Leeming 0000-0003-3409-399X , April Lawson 0000-0002-7948-3652 , and Alison Talbot 0000-0003-2765-2490 [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.177148454.49489032/v1 120 views 83 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Summary : Thoracic vertebral malformations occur frequently in small animals; however, they are uncommon in horses and usually appear as incidental findings on radiographs or at necropsy. Very few affected horses show clinical signs and typically these are observed at a young age. The previously reported cases of clinically apparent hemivertebrae in the thoracic spine of horses describe animals less than 28 months old. This case report describes the clinical, diagnostic and post-mortem findings in a 14-year-old gelding with a thoracic hemivertebra and insidious onset of ataxia. In addition to being the first reported clinically apparent case of a thoracic hemivertebra in an adult horse, this case illustrates the difficulty of diagnosing thoracic vertebral malformations in mature horses. Computed tomography of the thoracic spine can yield a reliable post-mortem diagnosis. Case Report Thoracic hemivertebra in a 14-year-old gelding with neurological symptoms Thoracic hemivertebra in an adult horse C. B. Blaettler $ , T. W. Maddox*, G. Leeming*, A. L. Lawson* A. Talbot* $ Hambleton Equine Clinic, Great Ayton, TS9 6QD, UK. *Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Neston, CH64 7TE, UK Keywords: horse, vertebral malformation, ataxia, computed tomography Summary: Thoracic vertebral malformations occur frequently in small animals; however, they are uncommon in horses and usually appear as incidental findings on radiographs or at necropsy. Very few affected horses show clinical signs and typically these are observed at a young age. The previously reported cases of clinically apparent hemivertebrae in the thoracic spine of horses describe animals less than 28 months old. This case report describes the clinical, diagnostic and post-mortem findings in a 14-year-old gelding with a thoracic hemivertebra and insidious onset of ataxia. In addition to being the first reported clinically apparent case of a thoracic hemivertebra in an adult horse, this case illustrates the difficulty of diagnosing thoracic vertebral malformations in mature horses. Computed tomography of the thoracic spine can yield a reliable post-mortem diagnosis. Main Text 1. Introduction Thoracic vertebral malformations occur frequently in small animals (Bailey and Morgan 1992) but are uncommonly reported in horses (Jeffcott 1980, Kirberger and Gottschalk 1989, Wong et al. 2005, Rush 2006, Henson 2009) and typically appear as incidental findings on radiographs or necropsy (Bailey and Morgan 1992, Denoix 2005, Wong et al. 2005, Henson 2009) . If thoracic vertebral malformations become clinically apparent, they typically do so in immature animals where compression of the spinal cord causes neurological deficits (Bailey and Morgan 1992, Denoix 2005, Wong et al. 2005, Rush 2006) . The previously reported cases of clinically significant thoracic hemivertebrae describe horses less than 28 months old (Kirberger and Gottschalk 1989, Ryan et al. 1992, Wong et al. 2005) . Assessment of abnormalities in the thoracic spine poses some challenges. Radiography of this area may be difficult, and findings may have questionable clinical significance (Kirberger and Gottschalk 1989, Bailey and Morgan 1992, Wong et al. 2005, Henson 2009) . Computed tomography (CT) appears to yield the most reliable diagnosis, apart from post-mortem examination, but is often not possible in horses due to their size (Wong et al. 2005) . This case report describes a thoracic hemivertebra found in a 14-year-old Thoroughbred cross gelding with insidious onset of ataxia 1.5 years prior to presentation. In addition to being the first reported clinically apparent case of a thoracic hemivertebra in an adult horse, it also illustrates the difficulty of diagnosing thoracic vertebral malformations in animals of this size. 2. Case details 2.1 Case history A 14-year-old Thoroughbred cross gelding presented to the Philip Leverhulme Equine Hospital (PLEH), University of Liverpool, for further investigation of insidious onset ataxia. The owner first noticed gait abnormalities 18 months prior to presentation. The symptoms progressively worsened and during the three months before presentation the horse showed weakness and dragging of the hindlimbs causing abrasions at the coronary band, bunny hopping when cantering, and reluctance to move forward and take weight whilst ridden. During this period the owner noticed the horse failing to lift its tail when defecating, accompanied by an increased amount of faecal material on the tail. Treatment with oral phenylbutazone and physiotherapy did not resolve the clinical signs. No previous episodes of ataxia or other neurological abnormalities were reported by the owner during the 12 years in which the horse had been in their possession. The reported medical history of this horse included a recurring submandibular abscess, which had been investigated seven years prior, surgical removal of a sarcoid on the left hindlimb, and left orbital fracture. 2.2 Clinical findings 2.2.1 General examination On presentation the horse was bright and alert with a body condition score of four out of five (Modified Henneke BCS system (Henneke et al. 1983) ). Vital parameters and auscultation of the thorax and abdomen were within normal limits. The gelding was seen to urinate and defecate normally. The pre-existing injury to the left orbit was found to be quiescent and not affecting the horse’s vision. 2.2.2 Neurological and orthopaedic examination Static neurological examination revealed an unaltered mental status, no behavioural abnormalities, and no cranial nerve deficits. The cutaneous trunci reflex was intact, but anal and tail tone were reduced. The gelding had an abnormal limb placement at rest, indicating proprioceptive deficits. Palpation revealed consistent, mild-to-moderate, lower cervical pain (located to the region of the articular process joints in C5-C7, particularly on the left side) as well as marked thoracolumbar pain. The range of motion of the back was reduced. Dynamic examination at walk revealed a stilted gait (particularly noticeable in the right hindlimb), an intermittent bilateral forelimb toe drag, and inconsistent bilateral hindlimb lameness and hypermetria. During examination the horse repeatedly knuckled or buckled. At trot the horse consistently moved on three tracks shifting the hind quarters to the right. Lunging exercise appeared to improve the horse’s gait in trot on hard and soft ground although a 4-beat canter was consistently observed on the left rein. The horse was able to lift his tail at exercise. The hindlimb ataxia, thoracolumbar pain, and reduced range of motion of the back were compatible with a lesion in the thoracolumbar region. A lesion of the upper motor neuron T3-L3 would account for the described ataxia and back pain. An additional lesion of the lower motor neuron L4-S1 or cauda equina could be feasible and would better explain the reduced tail/anal tone, however the typically associated urinary and faecal incontinence was not present in this case. 2.3 Radiography Laterolateral radiographs of the cervical, thoracic, lumbar, and coccygeal regions were obtained using a gantry-mounted X-ray generator [Apelem Magnum X, Med Imaging Healthcare Ltd, UK] and wireless digital detector [Canon CXDI-701C Wireless, Canon Medical Systems Ltd, UK]. Cervical radiographs showed a mild and likely incidental ventral location of C7 relative to C6. Images of the thoracic spine ( figure 1 and 2 ) showed an abnormally shaped vertebral body of T14 with an unusually wide dorsal spinous process (DSP). T13 had sclerotic bony remodelling of the caudal articular processes and ventral spondylosis deformans bridging to T14. Due to these changes the joint spaces were obscured. The DSPs of T11 to T13 appeared subjectively narrowed. Based on the above findings, congenital deformation of the thoracic spine was suspected. The implications of this were discussed with the owner and they elected to have the horse humanely destroyed. The body was donated for teaching and research purposes. 2.4 Post-mortem CT examination The region of interest based on radiography was dissected from the horse for further imaging with a multidetector (16 slice) CT scanner [Canon-Aquilion LB 1800mm, Canon Medical Systems Ltd, UK] ( figure 3 and 4 ). This identified a vertebral malformation at the level of T13-14. The vertebral body of T14 was asymmetrically misshapen and possessed an additional mamillary process and rib on the right side, while the cranial articular facet process on the left side was hypoplastic. Associated with the additional rib there was an extra vertebral foramen. The shape of the vertebral body resulted in an asymmetric narrowing of the right ventral aspect of the vertebral canal. Likely secondary to this lesion there was kyphoscoliosis, mild vertebral subluxation and marked ventral spondylosis, the latter suggesting instability. The degree of bony stenosis of the vertebral canal was likely causing spinal cord compression explaining the clinical signs, although the spinal cord did not undergo gross or histological evaluation 2.5 Diagnosis The post-mortem CT revealed a hemivertebra at the level of T14. This lesion likely caused instability at this region, indicated by the new bone formation and deviations of the vertebral column from the midline, and caused compression of the spinal cord at this level. Such a compression would explain the neurological deficits this horse showed on clinical and neurological examination. 3. Discussion 3.1 Epidemiology, Aetiology, and Pathogenesis Hemivertebrae occur frequently in small animals (Bailey and Morgan 1992). Anomalies of the thoracic vertebrae are typically incidental findings, but they may lead to neurological abnormalities secondary to stenosis, instability, or spinal angulation (Bailey and Morgan 1992). In horses, thoracic vertebral anomalies are uncommonly detected (Jeffcott 1980, Kirberger and Gottschalk 1989, Wong et al. 2005, Rush 2006, Henson 2009) and make up less than 3% of horses with thoracolumbar complaints (Jeffcott 1980). The lack of clinical signs could be contributing to this perceived low prevalence, appearing instead as incidental findings during radiography or necropsy (Bailey and Morgan 1992, Henson 2009). If thoracic vertebral malformations cause spinal cord compression, neurological symptoms such as ataxia or paraparesis usually become apparent in immature horses (Bailey and Morgan 1992, Wong et al. 2005, Rush 2006) , as the forces acting on the vertebral column after parturition quickly worsen the condition (Kirberger and Gottschalk 1989). This case is the first to document a clinically significant thoracic hemivertebra in a skeletally mature horse. Hemivertebrae are considered congenital malformations in which the vertebral bodies are wedge-shaped (Bailey and Morgan 1992, De Heer and Nout 2011). In the embryonic stage a mass of sclerotomal cells migrate toward the notochord and neural tube to form cranial and caudal sclerotomes, which later recombine with each other to form primordial vertebrae (Rush 2006). This recombination is called metameric shift and failure of this process results in the formation of hemivertebrae (Kirberger and Gottschalk 1989, Bailey and Morgan 1992, De Heer and Nout 2011). Hemivertebrae can also be caused by insufficient vascular supply to half of the vertebral body leading to a lack of ossification (Kirberger and Gottschalk 1989, Bailey and Morgan 1992, De Heer and Nout 2011). The aetiology of vertebral malformations such as hemivertebrae is suspected to be multifactorial, including genetic, metabolic, toxic, infectious, or traumatic factors (Kirberger and Gottschalk 1989, Bailey and Morgan 1992, Wong et al. 2005, Rush 2006) . In horses, hemivertebrae are typically found in the cervical spine (Denoix 2005) and may cause moderate to severe kyphosis, lordosis, or scoliosis (Denoix 2005, Rush 2006, De Heer and Nout 2011), typically worsening during growth and resulting in compression of the spinal cord (Rush 2006). Cervical hemivertebrae are usually accompanied by neurological deficits (Denoix 2005). Only a few cases of thoracic hemivertebrae in horses have been recorded. Ryan and colleagues (Ryan et al. 1992) described multiple hemivertebrae in two miniature horses: a yearling presenting with a mass at the withers expanding since birth, and a three-day-old foal submitted for necropsy. The affected vertebrae were T10-14 and T9-14 respectively. Kirberger and Gottschalk (Kirberger and Gottschalk 1989) described a case of a one-year-old American saddle horse with a hemivertebra at the level of T15 which, along with other vertebral malformations, lead to an increasing kyphosis and scoliosis at six months of age. The most recent case report (Wong et al. 2005) describes a nine-month-old quarter horse gelding with progressively worsening neurological symptoms caused by multiple spinal abnormalities including a hemivertebra at T7 and multiple fused DSPs and ribs. In contrast, the case described here was not associated with obvious deformation of the back and only became clinically apparent once mature. Clinical signs of congenital spinal malformations typically become apparent in immature animals (Bailey and Morgan 1992, Wong et al. 2005, Rush 2006) . The reason for the late onset of symptoms in this case is unclear. It is possible that less obvious clinical signs had been present for some time prior to presentation or even since birth, but remained either unrecognised or misinterpreted (e.g., as a mild intermittent hindlimb lameness). Alternatively, it may be that the area of the malformation remained stable initially, only developing instability later, either through a specific traumatic event or repetitive loading. However, since the bony remodelling suggests the instability had been present for some time, it remains unclear why there was a delayed onset of clinical signs. Spinal cord compression secondary to instability in the region of the hemivertebra (T14) can explain the hindlimb ataxia, thoracolumbar pain, and reduced range of motion. A reduced anal and tail tone is typically associated with injury to the cauda equina (Furr and Reed 2008). No lesion in this area was identified on radiography; however, CT images were not acquired of the sacrococcygeal region and thus a lesion may have been missed in this location. Full post-mortem examination and histopathology were not performed in this case but may have yielded further information. 3.2 Diagnostic approach Apart from clinical and neurological examination, the most common diagnostic modality used to identify vertebral abnormalities is radiography (Jeffcott 1980, Bailey and Morgan 1992, Denoix 2005, Henson 2009). Radiographically, hemivertebrae may be identified by their abnormal shape and effect on the vertebral alignment. In this case the DSPs of T11-T13 appeared subjectively narrowed, indicative of a congenital abnormality and usually associated with abnormalities of the vertebral bodies and articular process joints (Butler et al. 2000) . Secondary changes, such as sclerosis of the vertebral end plates or new bone formation, may also be present and can indicate clinical relevance and prognosis (Jeffcott 1980, Bailey and Morgan 1992). Uncommonly, ventral spondylosis deformans may be identified in horses (Butler et al. 2000, Henson 2009) , but its clinical significance is controversial (Jeffcott 1980, Butler et al. 2000, Henson 2009) . In the above cases, laterolateral radiographs of the thoracic spine were acquired and ventrodorsal images were obtained when patient size allowed. This did not always allow identification of the exact location and dimension of the vertebral malformations. Kirberger and Gottschalk state that it was difficult to distinguish individual vertebral abnormalities (Kirberger and Gottschalk 1989) and, in the case of the quarter horse gelding (Wong et al. 2005) , the radiographs failed to diagnose the number of affected vertebrae with certainty. The difficulties in radiography of the equine back are largely based on the size of the patient (Henson 2009), the overlaying anatomy (Bailey and Morgan 1992, Henson 2009), and the high prevalence of incidental findings (Henson 2009). Myelography is recommended to ascertain the presence of vertebral canal stenosis and thus clinical significance of hemivertebrae, and to look for other congenital or concurrent lesions (Bailey and Morgan 1992). Myelography of the lumbosacral region is possible in mature horses under standing sedation but has similar limitations to plain radiography (Vautravers et al. 2021) . Myelography was performed in two of the above-mentioned cases and appeared to be a useful tool for assessing spinal cord compression. In the case of the nine-month-old gelding with progressive ataxia an extradural compressive lesion at the level of the hemivertebra could be diagnosed (Wong et al. 2005) . However, similar findings were noted on the myelogram of the American saddle horse yearling, despite it not showing any neurological symptoms or defects (Kirberger and Gottschalk 1989). Computed tomography (CT) was only described in the most recent case report, delivering the most reliable diagnosis, allowing clinicians to identify the same malformations as during necropsy (Wong et al. 2005) . Ante-mortem CT examinations are limited to smaller patients due to physical limitations of fitting a large patient in a CT bore, and the considerable loss of image quality owing to the significant attenuation of the X-ray beam as it travels through the patient. 3.3 Treatment and Prognosis Most animals with clinically significant spinal malformations are euthanised (Kirberger and Gottschalk 1989, Bailey and Morgan 1992). Surgical decompression and stabilization can be performed in small animals (Bailey and Morgan 1992), but has not been described in horses (Kirberger and Gottschalk 1989). Additionally, these horses are predisposed to other congenital malformations as the embryologic formation of the spinal column is closely interrelated to that of other tissues and organs (Bailey and Morgan 1992, Rush 2006). 4. Conclusion The gelding presented in this case report showed spinal ataxia and back pain of insidious onset attributable to a lesion in the thoracolumbar spine. Clinical and radiographic examination revealed thoracic abnormalities. Further characterisation of these malformations as hemivertebra at the level of T14 was only possible on post-mortem CT. CT examination of the equine thoracic spine is limited ante-mortem due to the size of the thorax of adult horses. Thus, it may be concluded that thoracic vertebral malformations may go undiagnosed. Authorship: A. L. Lawson, A. Talbot, G. Leeming and T. Maddox were involved in the care and diagnostic investigations of the case. C. Blaettler prepared the manuscript. All authors contributed to the drafting, preparation and gave their final approval of the manuscript. Authors’ declaration of interests: No conflicts of interest have been declared. Source of funding: None. Ethics statement: The data in this study was collected from the clinical record retrospectively. Generic research consent was obtained from the owner on admission as well as prior to submission of this article. Acknowledgements: We would like to thank the owner of the horse presented in this study. We are grateful to the referring veterinarian and the hospital staff involved in the care of the horse admitted. Manufacturers’ addresses: Apelem Magnum X: Med Imaging Healthcare Ltd, Penrhyn Court, Penrhyn Road, Knowsley, Merseyside, L34 9AB, UK Canon CXDI-701C Wireless: Canon Medical Systems Ltd, Boundary Court, Gatwick Road, Crawley, West Sussex, RH10 9AX, UK Canon-Aquilion LB 1800mm: Canon Medical Systems Ltd, Boundary Court, Gatwick Road, Crawley, West Sussex, RH10 9AX, UK References Bailey, C.S. and Morgan, J.P. (1992) Congenital spinal malformations. Vet Clin North Am Small Anim Pract 22 , 985–1015. Butler, J.A., Colles, C.M., Dyson, S.J., Kold, S.E. and Poulos, P.W. (2017) The vertebral column. In: Clinical Radiology of the Horse, 4th ed., Wiley-Blackwell, Chichester. pp 531-601. Denoix, J.M. (2005) Thoracolumbar malformations or injuries and neurological manifestations. Equine Vet Educ 17 , 191–194. Furr, M. and Reed, S. (2015) Differential Diagnosis of Urinary Incontinence and Cauda Equine Syndrome. In: Equine Neurology , 2nd ed., Wiley-Blackwell, Chichester. pp 139-148 De Heer, N. and Nout, Y.S. (2011) Congenital kyphosis secondary to lumbar vertebral hypoplasia causing paraparesis in a Friesian foal. Equine Vet Educ 23 , 231–234. Henneke, D.R., Potter, G.D., Kreider, J.L. and Yeates, B.F. (1983) Relationship between condition score, physical measurements and body fat percentage in mares. Equine Vet J 15 , 371–372. Henson, F.M.D. (2009) Miscellaneous osseous conditions. In: Equine back pathology: diagnosis and treatment . 1st ed., Wiley-Blackwell, Chichester. pp 157-167 Jeffcott, L.B. (1980) Disorders of the thoracolumbar spine of the horse — a survey of 443 cases. Equine Vet J 12 , 197–210. Kirberger, R.M. and Gottschalk, R.D. (1989) Developmental kyphoscoliosis in a foal. J S Afr Vet Assoc 60 , 146–148. Rush, B.R. (2012) Developmental vertebral anomalies. In: Equine Surgery, 4 th ed., Elsevier Saunders, St. Louis. pp 693-700. Ryan, J.A., Modransky, P.D., Welker, F.H., Moon, M.L. and Saunders, G.K. (1992) Kyphoscoliosis in two miniature horses. Equine Practice 14 , 21–23. Vautravers, G., Coudry, V. and Denoix, J. ‐M. (2021) Review of the use of transrectal ultrasonography for evaluation of the caudal lumbar – including lumbosacral – intervertebral discs and symphyses: Normal and abnormal ultrasonographic appearance. Equine Vet Educ 33 , 310–319. Wong, D.M., Scarratt, W.K. and Rohleder, J. (2005) Hindlimb paresis associated with kyphosis, hemivertebrae and multiple thoracic vertebral malformations in a Quarter Horse gelding. Equine Vet Educ 17 , 187–194. Figure legends Figure 1. Laterolateral radiograph of the dorsal spinous processes (DSP) of the thoracic vertebrae T13-18, cranial is to the left. The DSP of T14 appears widened and has a focal, smooth bony protuberance on its cranial aspect (*). The interspinous space cranial to T14 is narrowed. The caudal margin of the DSP has a normal contour and radiodensity. Figure 2. Laterolateral radiograph of the vertebral bodies T12-17, cranial is to the left. The dorsal spinous process of T14 appears widened (see image above). Its vertebral body has an abnormal shape with the cranial margin presenting as concave in the ventral half (*). The caudal margin of T13 forms the convex counterpart. Marked ventral spondylosis can be seen bridging between T13 and T14 (arrow). Figure 3a and b. 3D constructed post-mortem computed tomographic scan of the thoracic and lumbar spine. 3a. Ventral view, cranial is to the left, left is to the top of the image. 3b. View of the left side, cranial is to the left. The vertebral bodies of T13-15 have an abnormal shape, with T14 being narrowed ventrally and extending further to the right side than its neighbouring vertebral bodies. The left costovertebral joint of T13 is displaced caudally (arrow) and there is an additional rib articulating with T14 on the right side (*). These findings are suggestive of a semi-segmental hemivertebra, which may be the result of two vertebrae which have failed to separate and subsequently fused on one side. Figure 4a-c. Post-mortem CT images of the thoracic and lumbar spine. 4a. Mid-sagittal plane, cranial is to the left of the image. 4b. Dorsal plane, cranial is to the top of the image. 4c. Horizontal plane through T14 in a computed tomographic scan of the thoracic spine, right is to the right of the image. The vertebral body has a malformed shape, and the right ventral aspect of the bony vertebral canal is narrowed (*). This asymmetric bony stenosis is likely associated with compression of the spinal cord, although this cannot be evaluated on these post-mortem obtained images. Also note the asymmetric position of the mamillary processes and articulating ribs (arrow). The multifocal gas-hypoattenuating areas represent air present due to the post-mortem nature of these images. Supplementary Material File (figures.pdf) Download 575.43 KB Information & Authors Information Version history V1 Version 1 19 February 2026 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords ataxia computed tomography horse vertebral malformation Authors Affiliations Chantal Blaettler Great Ayton View all articles by this author Thomas Maddox W University of Liverpool School of Veterinary Science View all articles by this author Gail Leeming 0000-0003-3409-399X University of Liverpool School of Veterinary Science View all articles by this author April Lawson 0000-0002-7948-3652 University of Liverpool School of Veterinary Science View all articles by this author Alison Talbot 0000-0003-2765-2490 [email protected] University of Liverpool School of Veterinary Science View all articles by this author Metrics & Citations Metrics Article Usage 120 views 83 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Chantal Blaettler, Thomas Maddox W, Gail Leeming, et al. Thoracic hemivertebra in a 14-year-old gelding with neurological symptoms. Authorea . 19 February 2026. 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