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Degenerative lumbosacral stenosis is narrowing of the lumbosacral vertebral canal that results in compression of the cauda equina or nerve roots. It is most common in large breeds of dogs, especially German Shepherds, and is rare in cats. It results from degeneration and protrusion of the L7 to S1 disk, hypertrophy of the ligamentum flavum, or rarely subluxation of the lumbosacral joint. The cause is unknown, although German Shepherds with congenital transitional
vertebrae are at increased risk. Clinical signs typically begin at 3-7 yr of age and may include difficulty using the pelvic limbs, pelvic limb lameness, tail weakness, and incontinence. Pain on palpation or extension of the lumbosacral joint is the most consistent finding. There may be proprioceptive deficits, muscle atrophy, or a weak flexor reflex in the pelvic limbs. Plain radiographs may show degenerative changes, but definitive diagnosis requires MRI, computed tomography, or
epidurography. Dogs in which mild pain is the only sign may improve with 4-6 wk of rest. Treatment consists of surgical decompression of the cauda equina and spinal nerves. Prognosis for recovery is good, although urinary incontinence may not resolve. |
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Degenerative myelopathy of dogs (chronic degenerative radiculomyelopathy) is a slowly progressive, noninflammatory degeneration of the axons and myelin in the white matter of the spinal cord. It is most common in German Shepherds and Welsh Corgis, but is occasionally recognized in other breeds. The cause is unknown, although genetic factors are suspected. Pathologically, there is noninflammatory degeneration of axons in the white matter of the spinal cord, which is most
severe in the thoracic region. Affected dogs are usually >5 yr old and develop an insidious onset of nonpainful ataxia and weakness of the pelvic limbs. Spinal reflexes are usually normal or exaggerated, but in ~10% of cases, patellar reflexes are weak, reflecting involvement of lumbar dorsal nerve roots. Early cases may be confused with orthopedic disorders; however, proprioceptive deficits are an early feature of degenerative myelopathy and are not seen in orthopedic disease.
Signs slowly progress to paraplegia over 6-36 mo, although signs may fluctuate. Myelography or MRI and CSF analysis are essential to rule out compressive and inflammatory diseases. Treatment with aminocaproic acid (500 mg, PO, tid), vitamin supplements, and exercise has been recommended, but the safety and efficacy of this treatment has not been documented. The longterm prognosis is poor; most animals are euthanized within 1-3 yr of diagnosis. |
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Equine degenerative encephalomyelopathy is a progressive neurologic disorder of horses and zebras characterized by diffuse degeneration of axons, myelin, and neurons in the spinal cord and, to a lesser degree, the brain stem. It has been reported in many equine breeds in North America, Australia, and England. The etiology is incompletely understood, but a
vitamin E deficiency and genetic factors are suspected. Clinical signs usually become apparent during the first year of life and consist of ataxia and weakness in all 4 limbs, although the hindlimbs may be more severely affected. Clinical signs may stabilize or slowly progress. Myelography and CSF analysis are normal. Vitamin E supplementation is preventive in some cases, and affected horses may improve with supplementation. |
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Intervertebral disk disease is degeneration and protrusion of the intervertebral disk that results in compression of the spinal cord, spinal nerve, and/or nerve root. It is a common cause of spinal cord disease in dogs. Clinical signs due to disk disease are rare in cats and horses. Chondrodystrophoid breeds of dogs (eg, Dachshund, Beagle, Shih Tzu, Lhasa Apso, and Pekingese) are most commonly affected. In these breeds, there is chondroid degeneration of the disks within
the first few months of life. Disk extrusion can occur as early as 1-2 yr of age, and clinical signs are often acute and severe. In contrast, fibroid disk degeneration typically occurs in large breeds of dogs >5 yr old and causes slowly progressive clinical signs. The most common sites of disk extrusion are the cervical and thoracolumbar regions. The predominant sign of cervical disk extrusion is neck pain, manifested as cervical rigidity and muscle spasms. There may be thoracic
limb lameness or neurologic deficits, ranging from mild tetraparesis to tetraplegia. In thoracolumbar disk extrusion, there may be back pain, evident as kyphosis and reluctance to move. Neurologic deficits are usually more severe than those seen in cervical disk disease and range from pelvic limb ataxia to paraplegia and incontinence. In paraplegic animals, the most important prognostic finding is whether or not there is deep pain perception caudal to the lesion. This is assessed by
pinching the toe or tail and observing whether or not there is a behavioral response, such as a bark or turn of the head. Reflex flexion of the limb must not be mistaken for a behavioral response. |
| Definitive diagnosis of disk extrusion is based on radiography and myelography. Dogs with pain and minimal to moderate neurologic deficits often recover with 2-3 wk of cage rest. A short course of prednisone (1 mg/kg/day for 3 days) is often helpful in relieving pain. The use of anti-inflammatory or analgesic medication without concurrent cage rest is contraindicated because an increase in the dog’s activity may lead to further disk extrusion and worsening of spinal cord
compression. Clinical signs recur after conservative therapy in 30-40% of cases. |
| In animals with severe neurologic deficits, methylprednisolone sodium succinate may improve recovery of severe spinal cord injuries if given within 8 hr of injury (see
trauma,
Trauma). Medical therapy, however, is not a substitute for surgery, which should be performed promptly to decompress the spinal cord in animals with substantial neurologic deficits. Other indications for surgery are failure of conservative therapy and recurrent episodes. The prognosis is good for dogs with intact deep pain perception that are treated surgically. If surgery is performed within 24 hr of the loss of deep pain
perception, the chance of recovery is ~50%. If surgery is delayed for >48 hours after deep pain perception is lost, the prognosis is poor. Progressive myelomalacia develops in a small percentage of dogs with paraplegia and loss of deep pain perception caused by acute disk extrusion. |
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Equine motor neuron disease is a progressive, noninflammatory degeneration of motor neurons in the spinal cord and brain stem of horses. It is most common in the northeastern USA but has been reported in several areas of North and South America, Europe, and Japan. The etiology is unknown, although low plasma concentrations of vitamin E have been detected in affected horses. Adult horses of any age and breed can be affected, although Quarter Horses are affected most
commonly. It is more common in horses without access to pasture grass. Clinical signs consist of generalized symmetric weakness, trembling, and muscle atrophy. Affected horses often stand with their head held low and their feet camped under their body, frequently shifting their weight from one limb to another. Ataxia is not a feature of this disease, in contrast to most spinal cord diseases. Many affected horses have retinal abnormalities, including a distinct reticulated pigment
pattern and areas of hyper-reflectivity. Electromyography and biopsy of the spinal accessory nerve or the sacrodorsalis caudalis muscle are useful in the diagnosis. There is no specific treatment, but some horses improve partially after 2-3 mo of illness. |
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Degeneration of motor neurons is seen as an inherited or sporadic disease in Brittany Spaniels, Pointers, German Shepherds, Doberman Pinschers, and Rottweilers; cats; Hereford, Brown Swiss, and red Danish cattle; Yorkshire pigs; and goats. |
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Metabolic storage disorders are rare, usually inherited, metabolic disorders that can affect the CNS, including the spinal cord. See also
congenital and inherited anomalies of the nervous system,
Congenital and Inherited Anomalies of the Nervous System: Introduction. |
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Spondylosis deformans is a noninflammatory, degenerative disease characterized by production of osteophytes along the ventral and lateral aspects of the vertebral bodies. In advanced cases, the osteophytes may appear to bridge the intervertebral disk space. It is seen in dogs, cats, and bulls, and the incidence increases with age. The cause is breakdown of the outer fibers of the annulus fibrosis and stretching of the longitudinal ligament. The increased stress at the
vertebral attachment of the longitudinal ligament incites osteophyte production. It is usually an incidental radiographic finding. Rare cases cause spinal hyperesthesia, which should be treated with analgesics. |
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