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eferences 277

muscle atrophy was the most common physical exam finding (>90% of cases) in one study (Brehm
et al. 1995). The muscles affected will depend on which nerve root or nerve is affected by the tumor.
Deep palpation of the axillary area can elicit pain or the observer may be able to palpate a mass
effect if the tumor involves the distal aspect of the brachial plexus. In the latter cases, ultrasound
can be helpful to establish a diagnosis; however, MRI is the imaging modality of choice, with CT
being a less desirable alternative. Early tumors can cause visible lameness with no pain detected on
physical exam and in some dogs, no changes may be observed on MRI. These cases require sequen-
tial MRIs to accomplish a diagnosis (i.e. initially the tumor is too small to see on MRI). FNA or
biopsy is needed to provide a definitive diagnosis. Yet, since these tumors are mesenchymal in
origin, an FNA may yield a nondiagnostic sample (which does not rule out a malignant tumor). A
biopsy will be needed in these instances to provide an accurate diagnosis.
Early diagnosis of these tumors is critical since cases with distal tumors can be cured with ampu-
tation if treated prior to developing metastatic disease. The location and extent of the tumor with
respect to the plexus will influence the treatment options. Tumors in or distal to the plexus can be
treated with amputation alone, while tumors invading the spinal canal should be treated with a
hemilaminectomy, and radiation therapy in addition to amputation. Local excision can be possible
in some cases and stereotactic radiation therapy is an alternative treatment.

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