Assessment of the utility of using intra- and intervertebral minimum sagittal diameter ratios in the diagnosis of cervical vertebral malformation in horses.

Cervical vertebral malformation is one of the most common causes of ataxia in horses. The most important factor in the diagnosis of cervical vertebral malformation is the identification of cervical vertebral canal stenosis, but published data for minimum sagittal diameter ratios in adult horses are only available for C4-C7 intravertebral sites. Intra- and intervertebral sagittal diameter ratios at C2-C7 were evaluated in 26 ataxic horses, for which a complete clinical and neuropathological evaluation was undertaken. Eight of these horses were diagnosed with cervical vertebral malformation. In these horses the majority of compressive lesions were intervertebral. The mean sagittal diameter ratios of horses with cervical vertebral malformation were significantly smaller than those of horses without cervical vertebral malformation, and for an individual horse in our study, the site with the smallest intervertebral sagittal diameter ratio was always the site at which the spinal cord was compressed. Mean sagittal diameter ratio intravertebral site measurements of horses with cervical vertebral malformation were smaller than those of horses without cervical vertebral malformation; however, the site of compression could not be predicted from the data. For our dataset, horses with a sagittal diameter ratio of < or = 0.485 at any inter- or intravertebral site could be correctly classified as having cervical vertebral malformation, and sagittal diameter ratio measurements were an effective tool to identify at least one site of compression in an individual case.     

Congenital occipitoatlantoaxial malformations in the horse

From a clinical, radiological and morphological study of 9 horses with congenital malformations of the occiput, atlas and axis, and from a study of 2 reported cases, 3 diseases were defined: A. Familial occipitalisation of the atlas with atlantalisation of the axis in Arabian horses (7 cases in this report and the case reported by Leipold, et al., 1974). These horses had congenital atlantooccipital fusion, hypoplasia of the atlas and dens, malformation of the axis and modification of the atlantoaxial joint. B. Congenital asymmetrical occipitoatlantoaxial malformation (2 cases in this report). A Standardbred and a Morgan horse had atlantooccipital fusion, a wedge shaped vertebral piece attached to the caudal end of the axis and sigmoid scoliosis of the cervical vertebrae. C. Asymmetrical atlantooccipital fusion (the case reported by Schmaltz, 1915). This horse of an unknown breed had asymmetrical fusion between the atlas and occiput and cervical scoliosis. The clinical syndromes shown by horses with these malformations were variable but were broadly classified as: 1. Foal dead at birth, seen in one foal with A. 2. Tetraparesis at birth, seen in 5 foals with A. These foals were born with signs varying from tetraparesis to tetraplegia. 3. Progressive ataxia, seen in 2 foals with A. Clinical signs were due to a progressive focal cervical compressive myelopathy. 4. Congenital cervical scoliosis/deviated head, seen in the 2 horses with B and the horse with C. These horses had no signs of spinal cord or brain disease. The diagnoses were made clinically by palpation of the occipitoatlantoaxial region and were confirmed radiographically and/or by post mortem examination in all except one case. Pedigree analysis showed the familial nature of the particular occipitoatlantoaxial malformation seen in horses of only the Arabian breed.     

Retrospective study of 38 cases of femur fractures in horses less than one year of age.

Medical records of 38 horses less than 1 year of age and diagnosed as having a fracture of the femoral diaphysis, metaphysis or distal physis were evaluated. Twenty-six foals had fractures of the femoral diaphysis or metaphysis with the most common fracture configuration being comminuted. Twelve foals had distal physeal fractures with the most common fracture configuration being a Salter-Harris type II. Twenty-one foals with fractures of the capital femoral physis, neck or greater trochanter during the same time period were excluded from this study. Surgical repair was attempted in 16 diaphyseal and 2 distal physeal fractures. Most of the diaphyseal fractures were repaired by placing plates on the lateral and cranial surfaces of the bone. Dynamic condylar screw plates or angle blade plates were used for increased bone purchase in 4 foals with short distal fragments. Five foals with distal physeal fractures were treated; 2 were surgically treated by placing an angle blade plate on the lateral cortex, and 3 foals with minimally displaced distal physeal fractures were managed with stall confinement. Eight of the 16 surgically repaired diaphyseal fractures healed. Fracture location and configuration was not a determinant of outcome, but the mean age of foals with successfully repaired diaphyseal fractures was 2 months compared with 4 months for the unsuccessful cases, indicating that the age and size of the foal was important. Long-term follow up revealed that 6 of the 8 successfully repaired diaphyseal fractures had no residual effects of the fracture observed during performance of the horse for its intended use. Only 1 of the 2 surgically repaired distal physeal fractures healed, but this horse was eventually killed because of unthriftiness related to a malabsorption syndrome. Some form of complication developed in 13 of the 18 surgically repaired fractures. Infection was the primary cause of failure. The greatest determinant associated with infection was the inability to control post-surgical seroma formation.     

Pneumocephalus in five horses

Pneumocephalus is occasionally encountered in horses but poorly described in the literature. The study aimed to describe historical, clinical and diagnostic imaging findings and outcome in horses to increase the awareness and recognition of the condition amongst equine practitioners, allowing appropriate management of these cases. Cases of pneumocephalus from 4 participating institutions were identified and case details extracted from the medical records. Five cases of pneumocephalus were identified. Head trauma with suspected or confirmed fractures of the sinuses was the underlying cause in 4 cases, while the remaining horse was thought to have developed pneumocephalus secondary to sinusitis or trauma. Diagnosis was established radiographically in 4 cases and by computed tomography in a fifth. Gas was noted between the cranial vault and the brain, in the lateral ventricles, in the brain parenchyma and within the cranial cervical canal. The gas accumulation resolved gradually in all horses and did not appear independently to result in neurological compromise. Long‐term outcome was available for 3 cases, 2 of which were ultimately subjected to euthanasia due to neurological deficits. Pneumocephalus is a possible consequence of head trauma or sinusitis in horses; although the finding is frequently incidental, it has the potential to develop into a life‐threatening complication. Imaging the complete skull and cranial cervical spine is important to allow identification and appropriate management of these cases. The use of computed tomography enables easier identification and localisation of the gas accumulation within the central nervous system.     

Juvenile idiopathic epilepsy in Egyptian Arabian foals: 22 cases (1985-2005)

Background:Epilepsy is relatively uncommon in horses compared with other species and limited information is available.
Hypothesis:The objectives of the study were to describe the age of onset, clinical signs, clinicopathologic data, electroencephalographic findings, treatment, and outcome, including long-term prognosis in Arabian foals with idiopathic epilepsy.
Animals:Twenty-two foals were included in the study.
Materials and Methods: Medical records from 1985 to 2005 were reviewed.
Results:The age of onset of affected foals ranged from 2 days to 6 months. Seizures were characterized by generalized tonic and clonic motor activity, staring, and loss of consciousness. The most common postictal signs were transient blindness and abnormal mental status. The interictal neurologic examination was otherwise normal. Clinicopathologic data and imaging diagnostics were normal except in 4 foals that developed complications. Electroencephalography revealed epileptiform activity in 9 of 13 foals. Foals were treated with benzodiazepines for the short-term; whereas phenobarbital was used over the long-term. Potassium bromide was added in 3 foals in which seizures were multiple, frequent, and difficult to control. The long-term prognosis was favorable with cessation of seizures by 1 year of age. The most common complication was head trauma. The most common concurrent disease was pneumonia.
Conclusions and Clinical Importance: Juvenile idiopathic epilepsy of Egyptian Arabian foals has an early clinical onset but appears to be self-limiting. Information obtained from this study strongly suggests a heritable condition that merits further investigation.     

EX VIVO COMPUTED TOMOGRAPHIC EVALUATION OF MORPHOLOGY VARIATIONS IN EQUINE CERVICAL VERTEBRAE

Diagnostic imaging is one of the pillars in the clinical workup of horses with clinical signs of cervical spinal disease. An improved awareness of morphologic variations in equine cervical vertebrae would be helpful for interpreting findings. The aim of this anatomic study was to describe CT variations in left–right symmetry and morphology of the cervical and cervicothoracic vertebrae in a sample of horses. Postmortem CT examinations of the cervical spine for horses without congenital growth disorders were prospectively and retrospectively recruited. A total of 78 horses (27 foals, 51 mature horses) were evaluated. Twenty‐six horses (33.3%) had homologous changes in which a transposition of the caudal part of the transverse process (caudal ventral tubercle) of C6 toward the ventral aspect of the transverse process of C7 was present (n = 10 bilateral, n = 12 unilateral left‐sided, n = 4 unilateral right‐sided). There was one horse with occipito‐atlantal malformation, two horses with rudimentary first ribs bilaterally, and one horse with bilateral transverse processes at Th1, representing homeotic (transitional) vertebral changes. Chi‐square tests identified no significant differences in the number of conformational variations between the group of mature horses with or without clinical signs (P = 0.81) or between the group of mature horses and the group of foals (P = 0.72). Findings indicated that, in this sample of horses, the most frequently identified variations were homologous variations (transposition of the caudal part of the transverse process of C6–C7) in the caudal equine cervical vertebral column. Homeotic (transitional) variations at the cervicothoracic vertebral column were less common.     

Dorsal Laminectomy in the Horse III. Results in Horses With Cervical Vertebral Malformation

Subtotal dorsal cervical laminectomy was used to relieve spinal cord compression due to cervical vertebral malformation in 16 horses. The majority were Thoroughbred or Quarter Horse males, 1 to 4 years old. The caudal cervical vertebrae were involved in all but two instances. A Funkquist type B laminectomy was performed and the defect filled with a free autogenous nuchal fat graft. All horses recovered from surgery without complication or deterioration in neurological status. Neurological improvement occurred in 12 cases, including six that became sound. Three horses fractured a vertebral articular process and were euthanized. A modification to the shape of the laminectomy was adopted to reduce this complication.     

Contracted Foal Syndrome Associated with Multiple Malformations in Two Foals

Congenital anomalies in horses are very rare, and contracted foal syndrome is one of the most commonly reported. This malformation is characterized by contraction of the joints of the forelimbs and/or hindlimbs. In addition, the syndrome can be characterized by vertebral column malformations, such as scoliosis or torticollis, and cranial deformity. The present report describes the radiological and necroscopical findings of multiple rare malformations in two foals. Both foals showed skeletal abnormalities and fenestration of the abdominal cavity. Other pathological findings include a interventricular septal defect in one and a unilateral hydronephrosis and partial hydroureter in the other foal. Although in this report a specific aetiology could not be provided, insecticides treatment provided during the second month of pregnancy might play a role in the pathogenesis of these malformations.     

Surgical management of complete diaphyseal third metacarpal and metatarsal bone fractures: Clinical outcome in 10 mature horses and 11 foals

Reasons for performing study: Osteosynthesis of third metacarpal (McIII) and third metatarsal (MtIII) bone fractures in horses is a surgical challenge and complications surrounding the repair are common. Retrospective studies evaluating surgical repair, complications and outcome are necessary to increase knowledge and improve success of long bone fracture repair in the horse. Objectives: To evaluate clinical findings, surgical repair, post operative complications and outcome of 10 mature horses and 11 foals with McIII or MtIII fractures that were treated with open reduction and internal fixation (ORIF). Methods: Medical records were reviewed and follow‐up information obtained by means of radiographs and/or telephone questionnaire. Results: Survival was achieved in 62% of the horses (3 mature/10 foals). On long‐term evaluation (>6 months) 11 horses (2 mature/9 foals) were fit for their intended activity, one mature horse had a chronic low grade lameness, and one foal was lost to follow‐up because it was sold. The main fracture types were simple transverse (33.3%) or simple oblique (28.6%) and 71.4% of the fractures were open, 3 Type I (one mature/2 foals) and 12 type II (7 mature/5 foals). The preoperative assessment revealed inadequate emergency treatment in 10 horses (5 mature/5 foals; 47.6%). Survival rate of horses with open fractures was 12.5% (1/8) in mature and 85.7% (6/7) in foals. Post operative incisional infection (4 mature, 3 foals) was only managed successfully in 2 foals. Fracture instability related to inadequate fracture fixation technique occurred in 4 horses (all mature) and was always associated with unsuccessful outcome. Conclusions: Age, bodyweight and infection are strongly associated with outcome in treatment of complete McIII/MtIII fractures. Clinical relevance: Rigid fixation using plates and screws can be successful in treatment of closed or open, complete diaphyseal McIII/MtIII fractures in mature horses and foals. Instable fixation, infection and a bodyweight >320 kg are major risk factors for unsuccessful outcome.     

Surgical Stabilization of the Equine Cervical Spine

The Cloward technique for intervertebral fusion was utilized on 12 horses ranging from 3 months to 2 years of age. Of the 12 horses, 9 had been diagnosed as having equine cervical vertebral malformation (CVM) or "wobbles," and 3 were normal controls. A large hole was drilled from the ventral border of the vertebral bodies spanning the intervertebral disc and the vertebral end plates of the 2 articulating vertebrae. Frozen homologous bone dowels of slightly larger diameter from equine cadaver ilia were inserted in the holes. No adverse postoperative complication arose. Clinical improvement was seen in all horses with CVM. Three months postoperatively, partial or complete fusion was evident radiographically in 11 of the 12 horses. Necropsies were performed 3–6 months postoperatively to evaluate the quality of the fusion. Cadaver manipulation demonstrated reduced intervertebral movement at the operative site in all cases. The articulations of the equine cervical spine can be operatively fused by the Cloward technique, and surgically induced trauma is minimal. This technique can be used for stabilizing subluxations and may be applicable for treating fractures and osteolytic processes that have weakened vertebrae.     

Femoral Capital Physeal Fractures in 25 Foals

The medical records of 25 horses 1 year of age or younger affected with femoral head and neck fractures during an 18 year period were reviewed. Each fracture involved the capital physis. The foals were 11 days to 12 months of age (mean, 5 months). No femoral capital physeal fractures occurred in horses older than 1 year of age during the same period. The history in each case included acute onset of severe unilateral hindlimb lameness, 3 hours to 2 months (mean, 12 days) before presentation. Injuries observed were violent falls, struggles, and kicks. Crepitation, swelling, pain with manipulation or palpation or both, and apparent fracture fragment displacement were inconsistently noted. Tentative clinical diagnoses were confirmed by radiography in 24 foals and by necropsy alone in one foal. Twenty-one foals were euthanatized due to poor prognosis. One foal sent home for stall rest was lost to follow-up. Surgical repair was attempted in three foals. Two fractures were repaired with multiple intramedullary pins and the foals were euthanatized within 2 weeks due to surgical failure and, in one case, contralateral limb breakdown. The third fracture was repaired with a compressing screw and plate device; the animal was pasture sound at month 20.     

Evaluation of Cervical Spinal Fusion as a Treatment in the Equine "Wobbler" Syndrome

Cervical vertebral interbody fusion was performed on 30 horses affected with cervical vertebral malformation (CVM) or "wobbles" to assess the efficacy of the surgery in either preventing progression of or reversing the neurologic deficit induced by the syndrome. Evaluation of each horse prior to surgery included clinical, radiographic, neurologic, and laboratory examination. Subjects ranged from 3 months to 8 years of age, and included 22 males and 8 females of various breeds. Three normal horses were included as controls. The Cloward method of cervical fusion was used to achieve stabilization at the affected vertebral articulation. Horses were reexamined 3 months after surgery. Clinical improvement was seen in 90% (27 of 30) of the cases. Four horses were returned to training, which had been interrupted by onset of symptoms. Seven were returned to owners as breeding animals. Twelve horses were kept for long-term studies. Seven horses were sacrificed to examine the surgical site. In 6 of the 7 horses on which necropsy was performed, the most severe histologic lesion in the spinal cord could be predicted from lesions seen radiographically. The spinal cords of control animals were normal. Osseous fusion was dependent on the completeness of removal of disc fibrocartilage during surgery. We conclude that clinical improvement in some horses affected with CVM can be achieved by cervical fusion.     

Thoracic trauma in newborn foals

In a report describing life ending fractures (255 horses) from the Livestock Disease Diagnostic Center, Kentucky (1993 and 1994), 32 foals had rib fractures. The purpose of our study was to examine the incidence of rib fractures in newborn foals on a Thoroughbred studfarm by physical and radiographic examination, to determine factors which may contribute to the problem and to document any clinical consequences. All foals (263) included were examined within 3 days of birth. The thoracic cage was palpated externally for abnormalities and all foals were placed in dorsal recumbency to evaluate thoracic cage symmetry. Radiographs were used to diagnose foals with thoracic cage asymmetry (TCA) and rib fracture (RF). A diagnosis of costochondral dislocation (CD) was made when no radiographic evidence of fracture was present but there was severe TCA. Fifty-five foals (20.1%) had TCA (9 RF). One to 5 ribs were fractured on 9 of 40 radiographic studies. No consequences of the thoracic trauma was detected clinically, radiographically or ultrasonographically in this group of foals or at a 2- and 4-week follow-up examination. The percentage of foals with a history of abnormal parturition was higher in the TCA foals (15%) compared to the normal foals (6.8%). There were more primiparous dams in the TCA group than in the normal foal group. Fillies (56.6%) had a higher incidence of birth trauma than colts (43.4%). This study demonstrates that thoracic trauma is often present in newborn foals and may not always be of clinical significance. Dystocia foals and foals from primiparous mares should be considered high risk for thoracic trauma.     

Putative intestinal hyperammonaemia in horses: 36 cases

Reasons for performing the study: Intestinal hyperammonaemia (HA) has been infrequently reported in individual horses; however, there have been no studies describing clinical and laboratory data as well as short‐ and long‐term outcome in a larger number of cases. Objectives: To describe clinical and laboratory data and short‐ and long‐term outcome in a large group of horses with intestinal HA. Methods: Multi‐centred, retrospective study; case records of horses with HA were reviewed and any horse with a clinical or post mortem diagnosis of intestinal HA was included. Hyperammonaemia was defined as a blood ammonium (NH₄⁺) concentration ≥60 µmol/l and horses with a diagnosis of primary hepatic disease were excluded. Relevant data were recorded and, if appropriate, data from survivors were compared to nonsurvivors to identify potential prognostic indicators. Results: Thirty‐six cases, 26 mature horses and 10 foals with intestinal HA were identified. Case histories included diarrhoea, colic and neurological signs and the most common clinical diagnosis was colitis and/or enteritis. The most common clinical and laboratory abnormalities included tachycardia, increased packed cell volume, hyperlactataemia and hyperglycaemia. Fourteen horses (39%) survived to discharge; NH₄⁺ concentration on admission was the only parameter significantly associated with survival. All surviving horses and foals for which follow‐up information was available recovered completely and returned to their intended use without further complications. Conclusions and potential relevance: Intestinal HA occurs in mature horses and foals and can be associated with severe clinical and laboratory abnormalities; further studies are required to investigate predisposing factors and delineate possible differences in aetiologies.     

A Necropsy Survey of Neurologic Diseases in 4,319 Horses Examined in Normandy (France) from 1986 to 2006

The frequencies of neurologic diseases and various corresponding causes were analyzed in 4,319 Norman horses examined by autopsy between 1986 and 2006. Five hundred forty-three cases of nervous system disorders were detected, or a total prevalence of 12.6%. One hundred eighty-seven of the 543 horses (34.4%) exhibited lesions of a traumatic origin affecting the skull or the vertebral column at different levels. Their frequency was less in foals younger than 1 month of age and higher in horses aged 6 months to 2 years. Eighty-three cases of cervical vertebral compressive myelopathy (CVCM) (15.3%) were identified. Males and geldings were more often affected than females. CVCM was diagnosed mostly in animals aged 6 months to 2 years. Horses affected with lesions in the mid-cervical region (region C3–C5) were significantly younger than those exhibiting more caudal lesions (region C5–C7). Neonatal maladjustment syndrome was diagnosed in 62 foals younger than 3.5 days (4.8% of the causes of death between birth and 1 month) by using clinical or lesional criteria. The prevalence was higher in Thoroughbreds as well as in the miscellaneous breed category and less in French Standardbreds. Bacterial meningoencephalomyelitis and meningitis represented 9.6% of nervous system disorders (52 cases) and most often affected foals aged 1 to 6 months. The main bacteria identified were beta-hemolytic Streptococci , Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, and Actinobacillus sp. The other causes diagnosed were, in decreasing order of frequency: grass sickness or equine dysautonomia (6.3% of neurologic diseases), hepatic encephalopathy syndrome (5.2%), septic vertebral arthritis or osteitis mainly caused by Rhodococcus equi (2.6%), congenital defects of the nervous system (2.4%), equine herpesvirus 1 myeloencephalopathy (2.2%), botulism (2.2%), malformations of the vertebral column other than CVCM (2%), and neighboring polyneuritis associated with guttural pouch mycosis (1.5%).     

A retrospective study of nineteen ataxic horses

A retrospective study of 19 ataxic horses admitted to the College of Veterinary Medicine of the University of Montreal during the period of January 1985 to December 1988 is presented. There were 11 cases of cervical vertebral malformation, four of equine degenerative myeloencephalopathy, two of equine protozoal myeloencephalitis, one each of vertebral osteomyelitis and intervertebral disc protrusion. The clinical diagnosis of ataxia in horses requires neurological, radiographic, myelographic, and laboratory examinations.     

A retrospective study of head fractures in 21 horses

The clinical features of 21 horses which sustained head fractures are reviewed. There was a higher incidence of fractures in males and Standardbred horses. Surgical treatment was practical and successful in most cases when the fractures involved the bones of the jaws and the face. Fractures which involved the cranial cavity or the cranial nerves were difficult to treat and usually held a poor prognosis.     

Fractures of the rostral portion of the mandible and maxilla in horses: 89 cases (1979-1997).

OBJECTIVE: To compare fracture locations, repair methods, complications, and outcomes of horses with fractures of the rostral portions of the mandible and maxilla. DESIGN: Retrospective study. ANIMALS: 89 horses with fractures of the rostral portions of the mandible and maxilla. PROCEDURE: Medical records and radiographs were reviewed. Fractures were categorized by fracture location and stability. Postoperative complications and long-term outcome were determined by clinical examination and telephone interviews with horse owners. RESULTS: 4 fracture types were recognized. Fractures involving just the alveolar plate (33%) and those involving the alveolar plate and the body of the bone (32%) were most common and were often repaired by interdental wiring. Unilateral fractures of the mandible (11%) were managed without surgery if stable. Unstable fractures were repaired with wires, a U-shaped bar (U-bar), or a bone plate. Bilateral fractures (24%) were often repaired with orthopedic wires in foals or with a U-bar, acrylic splint, wires, or bone plate in adult horses. In 2 horses, bilateral fractures were managed conservatively. Short-term complications developed in 24 of 89 (27%) horses. Soft tissue infections and wire loosening or failure were the most common short-term and long-term complications. Wire replacement was not required in any horses after release from hospital. Persistent draining tracts were most often associated with bone sequestration. Long-term functional and cosmetic outcomes were favorable for all fracture types and repair methods. CLINICAL IMPLICATIONS: Although complications in horses with fractures of the mandible and maxilla are common, long-term prognoses for functional and cosmetic outcome are favorable.     

Brachygnathia in horses: 20 cases (1979-1989).

The medical records of 20 horses admitted to the veterinary medical center with a diagnosis of brachygnathia over a 10-year period (1979 to 1989) were reviewed. The study included 18 foals and 2 adult horses. Males were affected 5.7 times more frequently than females. The amount of disparity between the mandible and premaxilla varied between 0.75 and 3 cm. Sixteen foals were treated surgically with the temporary application of premaxillary tension band devices. Thirteen of the 16 surgical cases were available for follow-up evaluation. All of the surgically treated animals had improved incisive occlusion, and 6 foals had complete resolution of the deformity with corrections ranging from 0.75 to 2.5 cm. Complete correction of the malocclusion was more likely to occur if foals were treated when they were less than or equal to 6 months old. The average amount of correction achieved in foals treated when they were less than or equal to 6 months old was 1.5 cm. (range, 0.75 to 2.5 cm). Foals treated, when they were 7 to 12 months old, had an average of 0.6 cm of reduction in the malocclusion (range, 0.25 to 1 cm). Implant failure was the most common complication and occurred in 9 of the 13 foals treated surgically.