Research Update: The utility of ultrasonography to detect brachial plexus tumors in dogs
The shaved axillary region medial to the shoulder and cranial to the first rib was imaged with a 5- to 8-MHz curvilinear or linear transducer while the patient was in ventral recumbency with the limb extended and abducted. Large, hypoechoic tubular masses that displaced vessels and destroyed normal soft tissue architecture were identified in each patient. After the ultrasonographic screening, computed tomography (CT) or magnetic resonance imaging (MRI) was used to more fully assess the extent of the tumor. Subsequent histologic evaluations revealed peripheral nerve sheath tumors in three dogs and rhabdomyosarcoma in one dog.
In this retrospective study from a university teaching hospital, five dogs with progressive, unilateral forelimb lameness and neurologic deficits having undergone ultrasonographic evaluation of the brachial plexus region were described. None of the dogs had skeletal or joint disease or a response to antiarthritis medication.
The authors concluded that ultrasonography is a useful screening tool for imaging axillary tumors. Success depends on the tumor's size and location, one's ability to distinguish between a tumor and lymph node or tubular mass and normal vascular elements, and a clinical suspicion based on neurologic signs.COMMENTARY
Although not frequently diagnosed—in part because of a limited index of suspicion or paucity of advanced imaging modalities—brachial plexus tumors carry a poor prognosis for patients because of the lesions' progressively invasive nature. Treatment usually involves local nerve root tumor resection, forelimb amputation, or hemilaminectomy for nerve sheath tumors involving the spinal canal. Ultrasonographic screening, as described in this article, can be a useful diagnostic tool for practitioners lacking access to myelography, CT, or MRI equipment. Early diagnosis and subsequent surgical intervention may help reduce the morbidity and mortality associated with this condition.
Rose S, Long C, Knipe M, et al. Ultrasonographic evaluation of brachial plexus tumors in five dogs. Vet Radiol Ultrasound 2005;46:514-517.