Introduction:
Quadriparesis (weakness and ataxia of all 4 limbs) and quadriplegia (paralysis of all 4 limbs)
are common problems in all animals.
Once the neurologist, faced with an animal who has
neurologic disease affecting all 4 limbs, has determined that the lesion is below the foramen
magnum (meaning a spinal cord or peripheral disease), there are 4 possible anatomic locations for
the disease process:
1) if there is UMN disfunction in all 4 legs, the lesion is most likely to be in the
spinal cord between C1-C5;
2) if there is LMN disfunction in the fore legs and UMN disfunction
to the rear legs, the lesion is severe and involves spinal cord segments C6-T2;
3) if there is UMN
disfunction to the rear legs and “root signature” (lameness due to nerve root involvement) in the
forelegs, the lesion is mild and affecting spinal cord segments C6-T2; or,
4) if there is LMN
disfunction in all 4 limbs, the lesion is due to a diffuse LMN disease.
In developing the differential diagnosis for quadriparesis, the basic mechanisms of disease
must be considered along with the signalment and history.
Congenital diseases are not uncommon
in the cervical spinal column of dogs. These include agenesis of the dens (with resultant atlantoaxial
subluxation), blocked vertebra, multiple cartilaginous exostoses, leukoencephalomyelopathy of
Rottweilers, and hereditary ataxia of Jack Russell and Smooth-haired Fox terriers.
In older animals,
degenerative intervertebral disc (IVD) disease, inflammatory meningomyelitis and neoplasia are not
uncommon.
If the signs are symmetrical, then nutritional, metabolic and toxic diseases must be
considered.
On the other hand, most asymmetrical diseases can be separated into their most likely
causes, which must be included in the differential. These causes are discospondylitis,
meningomyelitis, IVD disease and neoplasia.
Diagnostic Approach:
Like the rest of the nervous system, the neurologic examination is the single most important
diagnostic method to localize diseases of the cervical spine, providing an indication from which to make a tentative differential diagnostic list. On the other hand, localizing diseases in the cervical
spinal column to a specific spinal segment can be difficult, since tests like the panniculus response
cannot be performed there.
Hyperpathia can be difficult to elicit and hyperesthesia is not easily
mapped.
The ancillary diagnostic tests for spinal cord disease are similar regardless of the cause and
include the minimum data base, spinal radiographs, EMG, CSF tap and analysis, myelography and
MRI. The minimum data base will often be normal or may need to be expanded based upon the
physical and neurologic examinations.
In older patients, routine chest and abdominal radiographs
and abdominal ultrasound may help make a diagnosis of the cervical disease or assist in making the
prognosis.
Spinal radiographs may show signs of degenerative disc disease, congenital
malformation, spinal arthritis or discospondylitis. The later disease being the only disease diagnosis
which can be made on plain spinal radiographs. The other diseases will need additional imaging
techniques to confirm that they are the source of the problem.
In acute diseases, the EMG may not
help identify denervation until 5-7 days have past; however, nerve conduction velocity studies may
help identify damaged nerves or diffuse LMN disorders. On the other hand, in chronic diseases, the
EMG may help to localize the disease process, so that radiographs can concentrate on the lesion.
The CSF tap can help determine the presence of inflammation or infection in cervical diseases. The
problem of inflammatory myelitis is increasing, making CSF tap and analysis critical in assessing
cervical neurologic disease. Even when other neurologic conditions are identified, myelitis may be
present. Unfortunately, many patients are treated with corticosteroids before being adequately
worked-up for cervical disease. The work-up performed in the face of the steroids may be
erroneous. As such, surgical intervention may be performed, only later to discover the cause of neck
pain was inflammatory meningomyelitis.
Spinal myelography helps to contrast the spinal cord when
looking for mass lesions. It can be an extremely valuable diagnostic aid in determining the need for
surgical intervention and what surgical approach is best.
In cervical vertebral malformation
complex, the lesion is dynamic. The only imaging technique which can provide dynamic views is
the myelogram. Myelography, therefore, remains the single most important imaging technique for
assessing surgical diseases in the cervical spine. When the myelographic data is lacking or when
it is not clear what the lesion represents, MRI can add diagnostic detail.
MRI may be important is
assessing neoplastic disease precesses, including nerve root tumors. The sequence of diagnostic
tests logically follows the pattern of minimum data base, EMG, spinal radiographs, CSF tap,
myelography and, finally, MRI. If an accurate diagnosis is made along the way, the remaining test
may not be needed. |
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