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Spinal muscular atrophy is an inherited lower motor neuron (LMN) disorder in Brittany Spaniels that can have an early (by 1 mo), intermediate (by 4-6 mo), or delayed (>1 yr old) onset. Rottweilers can also develop an early form of spinal muscular atrophy that is referred to as a motor neuron disease. Swedish Lapland puppies are affected at 5-7 wk of age,
Stockard’s paralysis (seen in Great Danes crossed with Bloodhounds or Saint Bernards) has an onset at 11-14 wk, and English Pointers are affected when ~5 mo old. LMN disease also is seen in puppies of other breeds, including Doberman Pinschers and Briquet Griffon Vendéens; a focal form involving the thoracic limb(s) is seen in German Shepherds. Paraparesis or tetraparesis with neurogenic muscle atrophy are the main clinical
features. The severe, generalized LMN disease in spinal muscular atrophy closely resembles the signs of a peripheral neuropathy. Loss of motor neurons in the spinal cord is the most striking feature on necropsy. There is no treatment. |
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Demyelination of miniature Poodles is presumed to be an inherited disorder involving primarily the spinal cord. This rare condition causes paraparesis at 2-4 mo of age that rapidly progresses to tetraplegia. There is no treatment. |
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Ataxia of Jack Russell and Smooth-haired Fox Terriers causes ataxia and dysmetria of the pelvic limbs at <6 mo of age. Signs progress over 1-2 yr. Many cases manifest seizures. Spinal cord demyelination is found on necropsy. Clinical signs may stabilize after several months, and some affected animals are able to live a relatively normal life, in spite of the abnormal movements. |
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Afghan Hound myelopathy is an inherited disorder that causes both demyelination and necrosis of the spinal cord. Paraparesis develops some time during the first year of life and progresses to paraplegia within 1 wk. The thoracic limbs become involved over the next 1-2 wk. A similar condition is seen in young Kooiker dogs (Dutch Decoy dogs), of either sex, with signs beginning from 3-12 mo of age. Prognosis is poor in both breeds. |
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Neuraxonal dystrophy is described in both cats and dogs but primarily in Rottweiler dogs (autosomal recessive inheritance). In Rottweilers, the onset is between 3-24 mo of age, and the disorder progresses slowly over several years. Signs include cerebellar dysfunction and dysmetria in all 4 limbs, but with preservation of paw position sense, which should distinguish it from leukoencephalomyelopathy (see below) and from advanced motor neuron disease in
the same breed. Collie dogs in Australia and New Zealand develop similar clinical signs at 2-4 mo of age. There is also early onset in Papillons and Chihuahuas and in cats (autosomal recessive in Domestic Tricolored cats). Axonal spheroids, often in specific regions of the brain and spinal cord, are the characteristic pathologic finding of these conditions. |
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Leukoencephalomyelopathy of Rottweilers has a later onset than neuraxonal dystrophy (see above), usually at ~2-3 yr of age. It is possible that the disorders have a similar basis because animals occasionally may show histopathologic features of both conditions. In leukoencephalomyelopathy, there is no head tremor and paw position sense is delayed. Bilaterally symmetric areas of spinal cord demyelination are the predominant findings on necropsy. |
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Calcium phosphate deposition in Great Danes causes mineralization of soft tissues and bone deformity, with dorsal displacement of C7. The resultant compressive myelopathy is seen in puppies 1-2 mo old. This condition is distinct from caudal cervical spondylomyelopathy (see below). |
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Progressive axonopathy of Boxer dogs is an autosomal recessive disorder that causes patellar hyporeflexia, severe dysmetria, loss of paw position sense, and spastic paresis at 1-7 mo of age. Axonal spheroids are widespread in both the central and peripheral nervous system on necropsy. Although this condition does cause loss of the patellar reflex, in general, the signs are more suggestive of spinal cord disease than of a peripheral neuropathy. There is no treatment, but
affected dogs can live relatively comfortably for a considerable time. |
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Breed-associated aseptic meningitis (steroid-responsive meningitis-arteritis) has been reported in Beagles, Bernese Mountain Dogs, Boxers, German Shorthaired Pointers, and sporadically in other breeds. The main signs are neck pain, pyrexia, and dramatic pleocytosis in the CSF in young dogs. Prognosis is guarded to favorable, especially in dogs with acute disease that are treated promptly using immunosuppressive doses of corticosteroids. |
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Congenital vertebral malformations include
hemivertebrae (shortened or misshapen vertebrae),
block (fused) vertebrae, and butterfly vertebrae (having a sagittal cleft). Hemivertebrae are most common in screw-tailed dog breeds and are inherited in German Shorthaired Pointers. Decompressive surgery can be very successful but sometimes needs to be combined with spinal stabilization.
Multiple cartilaginous exostosis is a benign proliferation of cartilage or bone that can affect the ribs, long bones, or vertebrae and may have a familial basis.
Transitional vertebrae are often clinically associated with lumbosacral stenosis. Myelography or specialized imaging techniques (eg, computed tomography) are usually required to confirm spinal cord compression in these congenital conditions. Treatment consists of surgical removal
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Caudal cervical spondylomyelopathy (wobbler syndrome) may have a heritable basis in Borzois (5-8 yr) and Basset Hounds (<8 mo) and probably also Doberman Pinschers (³2 yr) and Great Danes (<2 yr). Neurologic deficits range from mild ataxia of the pelvic limbs to tetraplegia. Affected dogs often keep their neck flexed ventrally, and there may be caudal cervical pain. Spinal radiographs may show malalignment or remodeling of the vertebrae, narrowing of one or more
disk spaces, or spondylosis deformans. Myelography usually reveals a marked stenosis at the cranial orifice of the midcervical or caudal cervical vertebrae. Several surgical techniques can provide stabilization of the vertebrae or decompression of the spinal cord.
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Atlantoaxial subluxation is most commonly seen as a congenital disorder in young toy or miniature breeds of dogs and occasionally as a congenital disorder in several large breeds, including Rottweilers and Doberman Pinschers. Signs usually develop within the first few years of life and consist of an acute or slowly progressive onset of neck pain or gait dysfunction, ranging from ataxia to tetraplegia. Radiographic confirmation of diagnosis should be followed by
stabilization using ventral lag screw fixation. The prognosis is guarded.
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Arachnoid cysts (meningeal cysts, leptomeningeal cysts, subarachnoid cysts) cause accumulations of CSF and a focal myelopathy in young dogs. The etiology is unknown, but some cysts may have a congenital origin. Signs consist of progressive ataxia and weakness. Diagnosis is made by myelography and/or computed tomography. Prognosis may be favorable following surgical excision, although recurrence is possible. |
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Spinal dysraphism or myelodysplasia includes anomalies of the skin, vertebrae, and spinal cord that are secondary to faulty closure of the neural tube. Spinal dysraphism is inherited in Weimaraners. Neurologic deficits are evident by 4-6 wk of age and include paraparesis and a symmetric “bunny-hopping” gait in the pelvic limbs. There is a bilateral flexor reflex; pinching one paw elicits flexion of both pelvic limbs. There may be scoliosis or abnormal hair streams on the
dorsal aspect of the neck. Diagnosis is based on clinical signs and imaging techniques such as myelography and computed tomography. There is no treatment, but neurologic deficits usually do not progress. Similar malformations have been seen in other breeds of dogs and in calves, foals, and lambs. |
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Syringomyelia is the development of one or more fluid-filled cavities within the spinal cord.
Hydromyelia is accumulation of fluid within an enlarged central canal of the spinal cord. It is often difficult to differentiate between syringomyelia and hydromyelia, so the term syringohydromyelia is often used. Syringohydromyelia causes progressive ataxia and paresis; scoliosis and spinal pain is possible. Causes include trauma, neoplasia, inflammatory conditions, and developmental malformations. The most important is Chiari I malformation, an
underdeveloped occipital bone that induces overcrowding of the caudal fossa. This interferes with the circulation of spinal fluid and can result in hydrocephalus and/or syringohydromyelia of the cervical spinal segments. Syringohydromyelia associated with Chiari I malformation is most common in small-breed dogs, especially Cavalier King Charles Spaniels. Any age dog can be affected. Signs consist of ataxia and tetraparesis, neck pain, and persistent scratching at the base of the head
or shoulder. Radiography and myelography are usually normal. MRI can identify the cavitation in the spinal cord and any caudal fossa malformations. Treatment is directed at the underlying cause, if possible. Signs may improve with corticosteroids (prednisone at 1 mg/kg, sid). Surgery to decompress the caudal fossa can be helpful for Chiari I malformations. |
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Spina bifida occulta is a failure of the neural arch to fuse; if the spinal cord is also involved, it is called
spina bifida manifesta. The most likely clinical signs of spina bifida are LMN signs in the pelvic limbs and urinary or fecal incontinence. The prognosis for animals with substantial neurologic deficits is poor. Spina bifida can also accompany the
sacrocaudal dysgenesis that is inherited as an autosomal dominant trait in Manx cats. |
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Pilonidal sinus (dermoid sinus, dermoid cyst) is another consequence of faulty neural tubulation that appears to be inherited (autosomal recessive) in Rhodesian Ridgeback dogs. The sinus is lined by skin and may communicate with the subarachnoid space, causing possible meningitis or myelitis. Treatment consists of antibiotics and surgical excision of the sinus. |
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Epidermoid cysts are rare lesions that arise from entrapment of epithelial cells during closure of the neural tube. Myelography will reveal an intramedullary lesion in a young dog with progressive neurologic deficits. |
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