Page 418 - WSAVA2017
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An Urban Experience
has had a relapse: prednisolone at 4 mg/kg/day, PO or IV initially. After 2 days, the dose is reduced to 2 mg/kg daily for 1 to 2 weeks, followed by 1 mg/kg daily. Dogs are re-examined, including CSF analysis and hematology, every 4 to 6 weeks. When signs and CSF are normal, the dose can be reduced to half of the previous dosage until a dosage of 0.5 mg/kg every 48 to 72 hours is attained. Treatment is stopped 6 months after clinical examination, CSF, and blood profiles are normal. In refractory cases, other immunosuppressive drugs such as azathioprine
(at 1.5 mg/kg PO every 48 hours) may be used in combination with steroids (e.g., alternating each drug every other day). Antibiotics are ineffective.
Atlantoaxial subluxation
Onset of signs in dogs with the congenital form of the disease usually occurs in young dogs (less than two years of age), although problems can develop at any age. Signs can develop acutely or gradually, and waxing and waning of signs is often reported; presumably a reflection of instability at the atlantoaxial junction causing repeated injury to the spinal cord. Signs include neck pain (variably present), ataxia, tetraparesis, and postural reaction and conscious proprioceptive deficits with normal to increased muscle tone and myotatic reflexes in all four legs. In severe cases, animals can present with tetraplegia and difficulty breathing and they may die acutely as a result of respiratory failure.
Atlantoaxial subluxation can be diagnosed from survey radiographs of the cervical spine although extreme care must be taken when restraining and moving dogs in which this disease is suspected. It is preferable to do this with fluoroscopy so that the movement can be monitored to prevent accidental iatrogenic subluxation. Recently, MRI evaluation of the spine and cord has proved beneficial in both the diagnosis and prognosis.
Dogs with mild signs can be treated conservatively
by placing an external splint for at least 6 weeks. The splint must immobilize the atlantoaxial junction and so must come over the head cranial to the ears and go back to the level of the chest. The aim is to stabilize the junction while the ligamentous structures heal. The splint should be checked daily for signs of pressure sores
by the owner and checked weekly by the veterinarian, with regular bandage changes if necessary. While often effective in the short term, the long-term efficacy of this approach is not known and dogs treated in this way will always be at risk of repeated injury.
Surgery is recommended in dogs with neurological deficits, although it can be associated with high perioperative morbidity and mortality. Dorsal and ventral approaches to the atlantoaxial junction have been described, but dorsal approaches are associated with a greater risk of causing spinal cord injury during surgery, and a higher incidence of implant failure. This is a serious
disease but dogs with mild deficits treated surgically have an excellent prognosis if they survive the 48-hour perioperative period. Although reported surgical success rates range from 50% to 90%, the majority report a mortality rate in the region of 20% with the majority
of deaths occurring either during or immediately after surgery. As with all spinal cord diseases, prognosis is worse in animals with severe and chronic neurological deficits. It has also been shown that prognosis is better in young dogs (<24 months).
Spinal Meningiomas
Tumors affecting the spinal cord are described based
on their location as extradural, intradural–extramedullary and intramedullary. Intradural–extramedullary tumors that occur include meningioma and nerve sheath tumors. Meningiomas affecting the spinal cord are most common in the neck. Meningiomas of the spinal cord in dogs and cats tend to present with a progressive paraparesis. The clinical signs represent the spinal cord region involved. Paraspinal pain may or may not be present. Spinal meningiomas are the most common primary spinal cord tumor in cats older than 8 years of age. Mean age for spinal meningiomas in dogs is 9 years of age. Spinal meningiomas in dogs are most common in the cervical spinal cord, but occur in any region of the spinal cord. Myelography typically shows an intradural extramedullary compressive lesion. With MRI, these tumours are iso- to hypointense on T1-weighted (T1W) images, hyperintense on T2-weighted (T2W) images, and demonstrate strong, uniform contrast enhancement. These lesions should
be surgically explored because many meningiomas can be completely or partially removed and therefore may
be associated with prolonged survival after surgery. Postoperative radiation therapy may be used adjunctively to prolong survival in dogs with incompletely excised tumors. Treatment with surgery and radiation therapy can result in an improved outcome and prevent recurrence. Surgical results are guarded when meningiomas are associated with an intumescence and tumors with ventral location and invasion of the neural parenchyma.

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