Page 233 - Zoo Animal Learning and Training

240 Section III: Spinal Procedures

Diagnostic Evaluation noted in the CSF compared with cats since dogs typically have lym-
As with most disease syndromes, the clinician’s main goal is to phoma associated with the leptomeninges more commonly than
localize the underlying problem. As previously mentioned, the his- cats. Elevated protein levels without concurrent increased cellular-
tory and physical examination are paramount. The next step is ity is the most common result (albuminocytologic dissociation) [9].
deciding the most appropriate diagnostic tests and their order. A Obtaining either a cytological or small Trucut biopsy when pos-
complete blood count, biochemical profile, and urinalysis are usu- sible can often help with the overall plan and prognosis prior to
ally the initial part of a basic work‐up. In many cases of spinal neu- definitive treatment options. Typically, aspiration and/or small
rological disease all these results will be normal. In practice, Trucut biopsies are only practical and safe for extradural tumors
veterinarians find themselves differentiating spinal neoplasia from involving the vertebrae or surrounding supporting structures.
the more common syndromes such as disc disease, degenerative Cytology is usually safer and less traumatic with less risk but may
myelopathy, fibrocartilagenous emboli, cervical vertebral instability not be as sensitive as a biopsy and certainly not as specific in
or similar disorders. Certain basic testing results may reveal “red providing the grade of tumor. Histological grade may be very
flags” that preclude the more common differentials. For example, important in treatment options and certainly with prognosis [17].
elevated calcium (lymphoma), low hematocrit (anemia of chronic Depending on the size, location and involvement of the vertebral
disease), and significantly elevated globulins (plasma cell tumor) tumor, blind aspirates or Trucut biopsies can be obtained.
signal underlying issues that are strongly indicative of a possible Ultrasound guidance and CT‐assisted biopsy are other more accu-
neoplastic process. Radiographs would be the next step in the pro- rate means of obtaining preoperative samples.
cess. While many spinal tumors are primary in origin, it is still If lymphoma specifically is suspected, then other diagnostics may
imperative to exclude the possibility of a metastatic lesion. obtain a definitive diagnosis when the CSF does not yield a conclu-
Radiological studies should include three‐view thoracic radio- sive answer. If enlarged lymph nodes are detected on physical exami-
graphs. Abdominal radiographs and possibly abdominal ultra- nation, abdominal ultrasound or chest radiographs and aspiration of
sound may also be indicated. Radiographs of the spinal column are an abnormal/enlarged lymph node may be beneficial. Liver, splenic
the next logical step. Patients are sedated to allow proper position- or bone marrow cytology may also give a definitive answer.
ing. In some cases radiographs of the pelvis and hips are also done
at this time. Advanced imaging of the spine generally confirms the
diagnosis: MRI, CT, and myelography are the mainstays. Each has Treatment Options
advantages and disadvantages and not everyone has easy access to Surgical intervention is of paramount importance in the treatment
every modality. MRI, CT and myelography are all very good at eval- of spinal neoplasia. Spinal lymphoma, which responds very favora-
uating extradural lesions. If bony involvement is suspected, then bly to radiation therapy, might be the only or one of the few excep-
some of the older lower‐quality MRI machines may give under- tions to this rule. Three important aspects of treatment are deciding
whelming results when compared with CT and myelography. on the best approach for removal or debulking the mass, seeking the
Generally, MRI or CT myelography will provide the necessary input of an oncologist for adjunctive therapy, and considering the
imaging. CT can detect changes in physical bone density as small as risk–benefit ratio of the surgery. How best to remove or debulk
0.5%, whereas radiographs need about a 10% change in density the tumor can influence the success and long‐term comfort for the
before it becomes obvious [9]. One clear advantage of using CT to patient. Working with an oncologist will provide the most effective
scan a bony vertebral tumor is the ability to reconstruct an image and current follow‐up therapy. The potential effectiveness of radia-
for use in surgical planning. Intramedullary tumors would be best tion and chemotherapy can be a consideration in the aggressiveness
evaluated with MRI and myelography. Tumors caudal to the L6 of the surgery and in some instances the procedure to perform. In
region are typically better evaluated with MRI and/or CT with epi- most cases complete removal is the ideal result but this must be
durography. Myelograms and epidurograms are less sensitive in this weighed against possible permanent damage to the spinal cord and
area due to lack of the dural sac in this location. Intradural/ the risks of fracture, luxation or generalized instability as a result of
extramedullary tumors and intramedullary tumors from C1 to L6 surgical removal of supporting structures. The surgeon must act as a
are usually well defined with a myelogram. patient advocate and evaluate as fully as possible the risk–benefit
Intradural/extramedullary tumors often appear as expanded and ratio in performing a specific surgery. In many cases long‐term
outlined masses on one side of the spinal column. The other side of results are significantly improved with follow‐up radiation and/or
the column often deviates abaxially due to spinal cord swelling. chemotherapy and owners should be made aware of this prior to
This phenomenon is known as the “golf tee” sign (see Figure 27.2). surgical intervention. Specific approaches to spinal tumors are
In contrast, intramedullary tumors appear expansile and give the described elsewhere in this book as well as many other sources. In
spinal cord the impression of being “fat” due to the bilateral devia- general, surgeons should use the approach that allows the best visu-
tion of the contrast column in the affected area. Bone scintigraphy alization of the tumor as well as allowing the best chance for removal
can also be used to detect early signs of bony vertebral neoplasia [9]. with least possible untoward complications.
However, this is rarely used in private referral practice and is not Sometimes, performing a rhizotomy is necessary to either gain
widely available in the university teaching hospital setting. better access to the tumor or for alleviating regional pain.
Rhizotomies in the lumbosacral and caudal cervical region can, of
course, have possible neurological consequences. Removal of
tumors within the dura require a durotomy. This is best achieved
Cytology/Biopsy using a #11 or #12 scalpel blade. The tumor can often be “teased”
When possible, cellular evaluation prior to any major surgical ther- from the spinal cord (Figure 27.9). Ultrasonic surgical aspirators
apy is important. Cerebrospinal fluid (CSF) analysis, with the have also been employed. The surgeon attempts as complete
exception of spinal lymphoma, does not typically give a definitive removal as possible while at the same time balancing the risk–ben-
diagnosis. Dogs have a higher chance of lymphoma cells being efit ratio of removal. Surgery alone for dogs with spinal tumors can