Cervical vertebral canal endoscopy in a horse with cervical vertebral stenotic myelopathy

A 3-year-old Thoroughbred gelding presented with a history of neurological signs, including incoordination in his hindlimbs, of about 7 months' duration. On initial examination, the horse exhibited ataxia and paresis in all limbs with more severe deficits in the hindlimbs. Cervical radiographs displayed severe osteoarthritis of the articular processes between C5 and C6. On subsequent cervical myelography the dorsal contrast column was reduced by 90% at the level of the intervertebral space between C5 and C6. Cervical vertebral canal endoscopy, including epidural (epiduroscopy) and subarachnoid endoscopy (myeloscopy), was performed under general anaesthesia. A substantial narrowing of the subarachnoid space at the level between C6 and C7 was seen during myeloscopy, while no compression was apparent between C5 and C6. Epiduroscopy showed no abnormalities. After completion of the procedure, the horse was subjected to euthanasia and the cervical spinal cord submitted for histopathological examination. Severe myelin and axon degeneration of the white matter was diagnosed at the level of the intervertebral space between C6 and C7, with Wallerian degeneration cranially and caudally, indicating chronic spinal cord compression at this site. Myeloscopy was successfully used to identify the site of spinal cord compression in a horse with cervical vertebral stenotic myelopathy, while myelography results were misleading.     

Tracheal trauma and pneumonia secondary to endotracheal intubation in a horse undergoing general anaesthesia,computerised tomography and myelography

Endotracheal intubation is commonly performed in horses undergoing general anaesthesia to avoid fluid aspiration and provide mechanical ventilation and inhalational anaesthetic agents. Secondary laryngeal and tracheal trauma following intubation is not rare. This case report describes the successful treatment of a horse with laryngeal and tracheal trauma secondary to intubation during myelography. Based on other clinical reports and clinical experience, movement of the endotracheal tube during myelography was considered the most likely cause of the damage. This case underscores the importance of monitoring horses for development of respiratory signs after general anaesthesia for computerised tomography and myelography.     

Sequelae of myelography in the horse

The records of 131 horses undergoing general anaesthesia and positive contrast cervical myelography with metrizamide were examined to determine the effect of the procedure on the 'patient'. Three per cent of minimally ataxic and moderately ataxic horses had serious complications after myelography. Thirty-two per cent of severely ataxic horses died or were destroyed after general anaesthesia and myelography. Although general anaesthesia and myelography are essential components of a complete neurological evaluation of a horse, they impose a significant risk.     

Tracheal necrosis as a fatal complication of endotracheal intubation

This case report describes the death of a yearling Thoroughbred colt due to segmental severe necrotising tracheitis with stenosis of the tracheal lumen, 19 days after endotracheal intubation for elective endoscopic surgery. The stenosis of the trachea leading to asphyxiation was caused by an inflammatory process accompanied by massive accumulation of necrotic material, fibrinous inflammatory exudate, oedema and granulation tissue. The cause of this inflammation was likely to be a bacterial infection secondary to traumatic damage of the tracheal mucosa. Given the clinical history and location of the lesion, the endotracheal tube used for general anaesthesia was hypothesised to be responsible for this damage. Delayed tracheal necrosis as a fatal complication of endotracheal intubation has not previously been described in the horse and should be considered as a potential catastrophic consequence following relatively innocuous clinical signs.     

Postanesthetic hemorrhagic myelopathy in a horse

Acute hemorrhagic myelopathy developed in the sixth cervical to the eighth thoracic spinal cord segments of a 1-year-old Quarter Horse colt that was castrated under general anesthesia while in dorsal recumbency. Clinical signs were consistent with severe transverse myelopathy caudal to the brachial enlargement and cranial to the lumbosacral enlargement of the spinal cord. Histologic examination of the spinal cord revealed hemorrhage in the gray matter, with multiple blood-filled clefts in otherwise normal neuropil. Hemodynamic changes in the spinal cord associated with anesthesia and dorsal recumbency may have led to hypoxic vessel damage, with massive hemorrhage after surgery, when the horse was returned to lateral recumbency. Postanesthetic hemorrhagic myelopathy is a possible complication of positioning in dorsal recumbency, during anesthesia, in rapidly growing, young horses.     

Computed tomographic myelography of a foal with discospondylitis and extradural spinal cord compression due to a vertebral abscess

A one‐month‐old Quarter Horse colt presented with progressive gait abnormalities and weakness. The foal was ataxic at presentation. Radiography identified focal endplate irregularities and lysis at C6–7. Radiographic diagnosis was discospondylitis. Computed tomographic myelography was performed immediately following euthanasia and identified an extradural compressive spinal cord lesion corresponding to the site of discospondylitis. Post mortem examination findings included abscess formation at the C6–7 intervertebral space with osteomyelitis extending into the adjacent physes and subchondral bone of caudal C6 and cranial C7. The vertebral abscess extended into the ventral spinal canal at C6–7 and was identified as the cause of extradural spinal cord compression. Salmonella sp. was cultured and isolated from purulent exudate at the intervertebral space. Computed tomographic myelography has not been previously reported for assessment of discospondylitis in horses and was successful at accurately characterising spinal cord compression in addition to osteolytic changes associated with discospondylitis.     

Unilateral degenerative joint disease of a cervical articular process joint between the fourth and fifth cervical vertebrae causing asymmetrical ataxia in a young horse

A 5-year-old horse was examined for investigation of asymmetrical, quadrilateral ataxia and paresis. Clinical examination was unremarkable, and a thorough neurological examination localised the lesion to the cervical spine. Following this, magnetic motor evoked potentials were acquired to allow for latency times to be determined. Abnormal conduction times were found to the right thoracic and right pelvic limbs, confirming that the horse had an asymmetrical cervical spinal myelopathy. Radiographs were acquired to ensure that the horse had no significant pathology which would contraindicate general anaesthesia. There were no abnormalities noted on these, so the horse underwent contrast-enhanced computed tomography of its cervical spine which revealed enlargement of the right articular process joint between C4 and C5 with dorsolateral impingement of the spinal canal and cord. Due to the poor prognosis for future performance, the horse was subsequently euthanised. A post-mortem examination confirmed the findings of degenerative joint disease, with some unexpected changes seen on histology of the spinal cord. The unilateral right-sided compression had caused degenerative changes to ascending and descending tract bilaterally indicating a dynamic component to this lesion, which would be more commonly understood to be static.     

Spinal ataxia in a 2-year-old colt caused by a compressive primary vertebral osteosarcoma

Neoplasia is a rare cause of ataxia in horses. This report describes a 2-year-old colt presented with sudden-onset ataxia in which a cervical vertebral osteosarcoma causing severe compression of the spinal cord was diagnosed. Radiological changes included a large osteolytic lesion in the vertebral body, the vertebral arch, the right cranial articular process and the right transverse process of C4, interrupting the borders of the vertebral foramen and the right transverse foramen. Myelography revealed a marked spinal cord compression. Necropsy confirmed the presence of a well-demarcated, invasive and firm mass protruding from the fourth cervical vertebral body that led to severe compression of the spinal cord. In spite of its strongly pleomorphic nature, the detection of osteoid confirmed the diagnosis of a central osteosarcoma of the combined type. To the best of our knowledge, a primary single vertebral osteosarcoma causing ataxia in a juvenile horse has not previously been reported, and findings of this case report could help in the diagnostic work-up of similar cases.     

Post-anaesthetic myelomalacia in a horse

This article describes a rare neurological complication of anaesthesia in a 2 year-old Clydesdale colt undergoing castration. Anaesthesia was induced with glyceryl guaiacol ether and ketamine and maintained with halothane. Following an uneventful anaesthetic of 40 minutes, the horse recovered from anaesthesia in a padded recovery stall. After approximately 70 minutes in the recovery stall, the horse attempted to stand and adopted a dog sitting position. One hundred and fifty minutes later, the horse became distressed and was sedated with xylazine. Clinical examination of the horse did not reveal any evidence of myositis or fractures. A neurological examination revealed an intact anal reflex, deep pain response in the hind legs, tail tone and voluntary movement of the hind legs was possible. The horse deteriorated neurologically over the next 24 hours and was euthanased on humane grounds. The horse was submitted for necropsy. Gross pathology was unremarkable except for a small amount of haemorrhage around the right kidney. Histopathology revealed no abnormalities in any muscle groups or peripheral nerves. Congestion and axonal swelling of the spinal cord was evident from T16 to S1. Ischaemic neurons were evident from L 1 to L 6. The most prominent lesions were at L4 and L5. A diagnosis of myelomalacia was made. This is a rare complication of anaesthesia in horses with 9 case studies appearing in the literature since 1979. This is the 1st case to be reported in South Africa. The speculated pathophysiology and risk factors for this complication are discussed.     

Tracheal perforation managed by temporary tracheostomy in a horse

Tracheal trauma with resultant rupture is uncommonly reported in veterinary literature. We report the case of a 16-year-old Thoroughbred gelding that sustained a 1 cm longitudinal perforation of the dorsal tracheal membrane in the proximal cervical region. The horse subsequently developed dyspnoea due to acute upper respiratory obstruction secondary to severe emphysema of the guttural pouches. A temporary tracheostomy caudal to the site of tracheal perforation was performed under local anaesthesia. This procedure helped relieve the upper airway obstruction and aided resolution of the injury by diverting air away from the site of tracheal perforation. After conservative management, the gelding recovered completely.     

Congenital kyphosis secondary to lumbar vertebral hypoplasia causing paraparesis in a Friesian foal

A 5‐day‐old Friesian colt was presented with a history of severe bilateral pelvic limb weakness since birth. Clinical examination revealed a painful dorsal deviation of the spinous processes of the lumbar vertebrae, pelvic limb paraparesis and grade 4/5 ataxia. Radiographic examination revealed kyphosis due to hypoplasia and malformation of the 5 lumbar vertebrae present. At myelography performed immediately after euthanasia, dorsal deviation of the myelographic contrast column was demonstrated at the level of T18–L4 with suspected spinal cord compression noticeable at L1. There was no lateral deviation of the spinal cord or scoliosis of the vertebrae visible.     

Otitis media‐interna and secondary meningitis associated with Corynebacterium pseudotuberculosis infection in a horse

A one‐year‐old Thoroughbred colt was evaluated because of facial nerve paralysis, ataxia and fever. Neurological evaluation found the colt to be obtunded and grade 3/5 ataxic in all 4 limbs. Right‐sided facial nerve paralysis was present and a large, deep corneal ulcer noted in the right eye. Signs of vestibular disease were also present, including circling towards the right and horizontal nystagmus. A complete blood count showed mild leucocytosis, neutrophilia and hyperfibrinogenaemia. A computed tomography (CT) examination of the skull was performed under general anaesthesia and a diagnosis of right sided otitis media‐interna was made. Culture of fluid taken from the middle ear and cerebrospinal fluid collected from the atlanto‐occipital site yielded pure growth of Corynebacterium pseudotuberculosis. Initial therapy consisted of antimicrobial treatment with cefotaxime and anti‐inflammatory treatment with flunixin meglumine. Six days after initiating treatment, the colt developed Clostridium difficile associated colitis. The colitis resolved with supportive care and the colt was discharged from the hospital receiving chloramphenicol. Eight months later, the colt continued to be mildly ataxic (grade 1/5), with a slight head tilt and facial nerve paralysis. To the authors' knowledge, this is the first reported case of otitis media‐interna due to C. pseudotuberculosis in the horse.     

Iopamidol myelography in the horse

The use of the non-ionic, water-soluble contrast agent iopamidol for myelography in seven horses is described. Contrast columns of diagnostic quality were produced in all seven cases and the procedure did not invoke any adverse reactions in the five cases which were recovered from general anaesthesia. It is concluded that iopamidol is a safe and effective contrast agent for myelography in the horse.     

COMPUTED TOMOGRAPHY IN THE EVALUATION OF CAUDAL CERVICAL SPONDYLOMYELOPATHY OF THE DOBERMAN PINSCHER

Caudal cervical spondylomyelopathy is a common neurologic disorder of Doberman pinschers which has a number of striking similarities to cervical spondylotic myelopathy in humans. Diagnosis of this human disease is facilitated considerably by the use of computed tomographic (CT) myelography. Sixteen Doberman pinscher dogs with caudal cervical spondylomyelopathy were studied by conventional myelography followed by CT myelography. A close correlation was noted between the CT myelographic appearance of the cervical spinal cord in these dogs, and that reported for human cervical spondylotic myelopathy. Five dogs had atrophy of the spinal cord, and in another there was an accumulation of contrast medium within the spinal cord. These features are often associated with a poor response to surgical decompression in humans with cervical spondylotic myelopathy. The CT examination provided information that could not be obtained by conventional myelography alone and should be considered as an additional diagnostic procedure in dogs with caudal cervical spondylomyelopathy.     

Fibrocartilaginous embolic myelopathy in a horse

Fibrocartilaginous embolic myelopathy was diagnosed in a 11-year-old, male, Tennessee Walking Horse by histopathological examination of the spinal cord after the horse was killed because of severe neurological dysfunction. Both ventral funiculi of C6 and C7 cervical spinal cord had extensive necrosis with blood vessels containing fibrocartilaginous emboli. A similar fibrocartilaginous embolus was observed in a single large spinal artery adjoining the vertebral leptomeninges.     

STANDING MYELOGRAPHY IN THE HORSE USING A NONIONIC CONTRAST AGENT

Standing myelography in the horse has been previously described. In that study, metrizamide was used and significant complications were reported. In recent years, the introduction of less-toxic nonionic contrast media has reduced the incidence of complications. This study was undertaken to determine whether standing myelography using a nonionic contrast medium could provide a diagnostic study and be performed safely in the equine patient. Standing myelography was performed in eight horses. The contrast medium used was iohexol. In five horses a myelogram of diagnostic quality was achieved; in one horse contrast flowed only to the level of C6 and in two horses contrast medium did not reach the cervical subarachnoid space. Owing to the difficulty in achieving good flow of the contrast medium in some horses, this procedure may be of limited utility. However, if puncture of the lumbosacral subarachnoid space can be achieved easily and quickly, standing myelography may be a clinically useful procedure. It may be attempted in cases in which the economic value of the patient makes myelography under general anesthesia impractical. In patients presenting for evaluation of ataxia it may be possible to perform a standing myelogram at the time of CSF sample collection from the lumbosacral space.     

Spinal mast cell tumor in a dog.

A 6-year-old, spayed female rottweiler was referred for left forelimb lameness followed by tetraparesis. A mast cell tumor compressing the spinal cord at the level of the sixth cervical to first thoracic (C6-T1) vertebrae was diagnosed based on cervical myelography and necropsy findings. This was considered a primary extracutaneous mast cell tumor, as no evidence of disease was found elsewhere. This is the first report of a primary mast cell tumor in this location.     

Iohexol myelography in the horse

Iohexol, a water soluble non-ionic contrast agent, was evaluated for myelography in the horse. Both 300 and 350 mg iodine/ml iohexol gave diagnostic cervical myelograms. Pathological changes were limited to extradural oedema and an increase in the number of white blood cells and specific gravity in the cerebrospinal fluid two days after myelography. This increase in white blood cells in the cerebrospinal fluid was, however, much less than that recorded by other authors using metrizamide and iopamidol contrast media. These findings indicate that iohexol is a less irritant myelographic contrast agent than those previously evaluated in the horse.     

Characteristic computed tomographic myelography findings in 23 Thoroughbred horses

The purpose of this observational study was to determine the characteristic computed tomographic (CT) myelography findings of cervical vertebral stenotic myelopathy (CVSM) lesions in Thoroughbred horses. A total of 23 Thoroughbred horses (age range, 155–717 days on CT examination; mean, 410.9 days) were analyzed. All 23 Thoroughbred horses underwent unenhanced radiography, radiographic myelography, and CT myelography. Unenhanced radiographs were observed the presence of cervical vertebral malalignment and osseous lesions. Radiographic myelograms were observed for signs of cervical spinal cord compression; additionally, CT myelograms were used to detect cervical vertebral osseous lesions. Ventral compressions were frequently observed in the cranial cervical vertebrae (C2–C4), whereas dorsal compressions were frequently observed in the caudal cervical vertebrae (C5–C7). Furthermore, osseous lesions of the caudal articular process developed more frequently than those of the cranial articular process. CT myelography in Thoroughbred horses is a useful method for detecting CVSM changes.