Case Report: A Novel Lateral Approach to the C7, C8, and T1 Intervertebral Foramina for Resection of Malignant Peripheral Nerve Sheath Neoplasia, Followed by Adjunctive Radiotherapy, in Three Dogs

Abstract

This case report describes the diagnosis, management and outcome of three dogs with peripheral nerve sheath tumors (PNSTs) involving the brachial plexus, C7 (case 1), C8 (case 2), and C8 and T1 (case 3) spinal nerves and nerve roots with intrathoracic invasion. Surgical resection required thoracic limb amputation and removal of the first rib, facilitating a novel lateral approach to the spinal nerves and foramina in all cases. This was followed by hemilaminectomy and rhizotomy in cases 1 and 2. Adjunctive radiotherapy was then performed in all dogs. All three dogs regained a good quality of life in the short-term following surgery. Two were euthanased after 3 and 10 months, following detection of a pulmonary mass in one case and multiple thoracic and abdominal masses in the other. The third dog was alive and well at the time of writing (7 months post-surgery). This surgical approach facilitated good access and allowed gross neoplastic tissue to be resected. The ease of surgical access was dependent, to a degree, on the size of the patient. This surgical approach can be considered in cases of PNSTs involving the caudal cervical or cranial thoracic spinal nerves and nerve roots. Adjunctive radiotherapy should be considered as part of a multi-modal approach to these challenging tumors due to the difficulty of achieving clean margins, particularly proximally, even with optimal surgical access.

Keywords: brachial plexus; dog; peripheral nerve sheath tumor; radiotherapy; surgery.

Figure 1

Left, case 1: transverse CT image at the level of the C7 vertebral body. There is a large, irregular soft tissue attenuating mass in the left axilla (outlined) which extends dorsally (arrowheads) through the enlarged C6–C7 intervertebral foramen to enter the vertebral canal. Middle, case 2: transverse CT image at the level of the C7–T1 intervertebral formamina showing a large, irregular mass (asterisk in its center) in the left axilla, extending proximally (arrowheads) through the C7–T1 intervertebral foramina to enter the vertebral canal. Right, case 3: transverse T1 weighted post-contrast image at the level of the mid T1 vertebral body. The right C8 spinal nerve (arrowheads) is enlarged and irregular and shows mild, homogenous contrast uptake. The right side of the dog is on the left side of each image.

Figure 2

Patient positioning prior to surgery. Both thoracic limbs are retracted caudally to allow the surgeon closer and more comfortable access. The dog is held securely to the table using tape and elasticated bandage, to prevent movement when the table is tilted. Sandbags (not visible in this image) are placed under the dog's cervical region to maintain the vertebral column in horizontal alignment. The yellow line shows how the initial incision is performed- dorsoventrally over the spine of the scapula and then in a circumflex manner around the limb.

Figure 3

Intraoperative image from case 2 showing a large ovoid axillary mass (circled) with extension (arrow) toward the C7–T1 intervertebral foramen. The star shows the medial aspect of the scapula. The forceps in the surgeon's right hand show the region of the osteotomised rib.