peripheral nerve tumors
Tumors involving the peripheral nerves, brachial plexus, or lumbrosacral plexus are uncommon and usually malignant sarcomas. Peripheral nerve sheath tumors extend along the nerve and can extend into the spinal cord. Peripheral nerve sheath tumors are classified according to their level of involvement with peripheral tumors defined as being distal to the brachial or lumbrosacral plexus, plexus tumors involving the nerves in the brachial or lumbrosacral plexus but distal to the intervertebral foramina, and root tumors involving the ventral or dorsal nerve roots and extending into the spinal cord. Lameness, muscle atrophy, and pain are common clinical signs. Metastasis is uncommon.
Peripheral nerve sheath tumors are suspected based on clinical examination and exclusion of other causes of lameness, such as orthopedic conditions and intervertebral disk disease. Electromyography may be useful for determining the location and extent of peripheral nerve involvement. Advanced imaging is preferred for the definitive diagnosis of a mass involving either a peripheral nerve or plexus and to determine whether this mass has extended into the spinal canal. MRI is preferred but CT scans can also be useful.
Surgical excision is recommended, but the type of surgery depends on the location of the tumor. Excision of the tumor with wide margins is recommended for peripheral tumors. Limb amputation, perhaps combined with laminectomy if the tumor has extended into the spinal canal, is recommended for plexus and root tumors. Radiation therapy has not been reported in the treatment of peripheral nerve tumors, but should be considered following surgical excision of plexus and root tumors.
The prognosis depends on the level of involvement and the ability to achieve complete surgical excision. The prognosis is excellent for dogs with peripheral tumors as complete surgical excision is possible. Tumor-related deaths are reported in 0% of dogs with peripheral tumors, but up to 78% dogs with plexus and root tumors following surgical resection.
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