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Cervical Vertebral Injuries in Camelids

by David E Anderson, DVM, MS, Diplomate ACVS
International Camelid Institute
College of Veterinary Medicine
The Ohio State University

Neurologic deficits originating in the cervical spinal cord are most commonly caused by larval migration of the meningeal worm Parelaphostrongylus tenuis. However, neurological deficits occasionally are found to be associated with either congenital vertebral malformations or cervical vertebral injuries. This discussion will be confined to our experiences with diagnosis and treatment of cervical vertebral injuries.

HISTORY (ANAMNESIS)

Many cervical injuries go unnoticed because the extensive fiber coverage of the cervical region hides cervical deviations from view. These injuries become apparent when the animal is sheared, develops an abnormal posture, or demonstrates neurological deficits. These observations may not be made for months following the injury. Acute injuries often occur when camelids are being halter trained by an inexperienced handler or when an individual becomes entrapped in a gate, fence, or feed bin. Rarely, these injuries are caused by fighting.

PHYSICAL EXAMINATION

Acute cervical injuries usually occur as subluxation of the vertebra (most often C3-4, C4-5, C5-6). Most often, the camelid is presented for examination because of abnormal head and neck posture, but may demonstrate neurological deficits. The most common neurologic deficits are upper motor neuron (UMN) deficits to the rear limbs, but either UMN or lower motor neuron deficits may be seen in the forelimbs depending on the site of the lesion. Hypermetric gait, most pronounced in the pelvic limbs, is commonly observed. Conscious proprioception deficits also may be seen. Most camelids are ambulatory when first examined, but may present paraplegic or tetraplegia.

Chronic cervical injuries often are presented for examination because of abnormal head and neck posture or difficulty grazing. Neurologic deficits are caused by progressive enlargement of callus around the vertebral articulations or fibroplasia of the longitudinal ligaments of the spinal column.

DIAGNOSIS

Diagnosis is usually obvious on physical examination. However, radiographic examination of the cervical vertebral column is required to evaluate the severity of the lesion(s) and assessment of candidacy for surgical intervention. We do not routinely perform a myelogram unless the radiographic findings do not match those expected based on the physical examination. Lesions usually are obvious and I do not feel that the risks and expense of myelography are justified in most cases. When multiple lesions are expected or physical examination findings suggest multifocal neurologic deficits, I perform myelography to determine candidacy for surgical intervention. I perform cerebrospinal fluid analysis as part of the routine data base in all camelids with neurologic deficits. CSF analysis allows me to distinguish between camelids with symptomatic cervical lesions and asymptomatic lesions also having parasitic myelitis.

TREATMENT
Non-surgical Management

Initial experiences with surgical intervention for cervical vertebral lesions were overwhelmingly poor. Therefore, I prefer to treat cervical subluxation conservatively when possible. Candidates for conservative management are those camelids having acute cervical subluxation, minimal to no neurologic deficits, and an owner willing to accept permanent deviation of the cervical spine. Rolled cotton is applied from the region of C2 to approximately T8. The cotton is placed in "figure 8" pattern around the forelimbs. Then, a fiberglass cast is applied to 4 layers thickness, a 1/4 inch aluminum rod is formed to fit over the dorsal thorax and along side of the neck, and additional casting material is placed to 4 layers thickness. The neck should be placed slightly elevated to the thoracic vertebral column. The fiberglass cast is maintained for 4 to 6 weeks and removed. The camelid is maintained in confinement for 4 weeks after the cast is removed. Feed and water should be elevated for easy access (2 feet above the ground). The purpose of the neck and body cast is to allow the cervical vertebral column to "stabilize" in a near normal overall conformation and to minimize the amount of callus and fibroplasia that will form. This will minimize the risk of the development of compressive lesions of the cervical spinal cord. The ventral aspect of the cranial end of the cast must be adjusted so that the head can be easily flexed without restriction.

Sugical Management

Surgical treatment of cervical injuries is indicated in animals with significant neurologic deficits or when owners desire correction of the cervical deviation for cosmetic reasons. Surgical approach is mandated by the lesions documented via radiography. Camelids have minimal soft tissue coverage of the cervical vertebra and, therefore, the surgical approach is straightforward. In my experience, decompressive laminectomy (dorsal or hemilaminectomy) and ventral vertebral stabilization have a poor prognosis for success. I have observed acute neurogenic edema and death following hemilaminectomy of a chronic, progressive C4-5 lesion. Also, I have observed respiratory failure and apparent coma after ventral stabilization of an acute subluxation of C3-4. I currently prefer surgical restoration of anatomic alignment of the cervical vertebral column via a dorsolateral approach without laminectomy. The fused articular facets are resected and the vertebral bodies re-aligned. Two 6.5-mm cancellous bone screws or end-threaded positive profile pins are placed into each vertebral body and these are connected by orthopaedic PMMA cement (antibiotic impregnated - optional). Application of bone plates is less desirable because the vertebral contour is complex, the vertebra have limited holding power for bone screws, and molding of the bone plate in multiple planes (3.5-mm broad minimum) decreases its resistance to bending and torque. A neck or neck and body cast is placed for 30 days following surgery.

When surgical correction is elected, I recommend that the anesthetist "capture" respirations from the beginning of surgery. The goal is to maintain arterial CO2 less than 40 mm Hg. I have observed a tendency toward severe hypercapnia (PaCO2 = 120 mm Hg) during cervical vertebral surgery in camelids.

PROGNOSIS

Conservative treatment has a fair to good prognosis for prevention of development of neurologic deficits, but anatomic alignment is not restored. In my experience, camelids with moderate to no neurologic deficits respond favorably to surgical intervention. Camelids with significant neurologic deficits (especially if the animal is unable to stand without assistance) are unlikely to improve and usually worsen after surgical intervention. I have been able to achieve 60 to 75 % of normal alignment of the cervical vertebral column with surgery.

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