Axis Dorsal Laminotomy for Excision of a Meningioma in a Dog
Background: Surgical access to the spinal cord at the level of C2 vertebra presents technical limitations, due to anatomical particularities in this region. The ventral slot technique does not allow space for the removal of dorsolateral masses. The axis hemilaminectomy technique provides limited access to the dorsal aspect of spinal cord and there is a risk of damaging the vertebral arteries. The axis dorsal laminotomy technique allows good access to spinal cord and preserves the atlantoaxial and nuchal ligaments, however few papers describe this technique. The objective of this paper is to report the axis dorsal laminotomy performed in a dog with a meningioma at this level.
Case: An 11-year-old male, Maltese dog, was presented with a 15-day history of progressive weakness, intense cervical pain and difficulty in locomotion of the four limbs. He was being treated with painkillers without improvement. On clinical examination, the physiological parameters were normal. Neurological examination showed tetraparesis with the syndrome localized in the cranial cervical region. The main differential diagnoses were intervertebral disc disease, neoplasia, inflammatory or infectious disease. Computed tomography was performed and the evaluation of images allowed the visualization of an intradural-extramedullary neoplastic process, promoting important spinal compression, with approximate dimensions of the lesion 0.70 cm high x 0.67 cm wide x 0.78 cm long, with apparent involvement of the meninges, with a more lateralized location on the left, with meningioma being the main differential diagnosis. Thus, exploratory surgery, through the technique of dorsal laminotomy of the axis was performed. After the removal of the mass, the spinous process was repositioned in its anatomical location and fixed with 0.6 mm steel cerclage wire that was passed through the holes made in the dorsal lamina of the axis. After the surgery a neck brace was kept for 45 days. According to the histological changes observed, the neoplasm was classified as grade one meningothelial meningioma. The patient showed gradual improvement and started walking again 4 days after the surgery, staying well and without pain for 5 months, when there was a recurrence of the neoplasia.
Discussion: Surgical access to the cervical region in question is limited due to the presence of complex ligamentous structures, vascular network and the anatomical features of the first and second cervical vertebrae. Thus, the dorsal axis laminotomy technique was used. The approach allowed good visualization of the spinal canal as well as the preservation of the atlantoaxial ligament, maintaining atlantoaxial stability. Through histopathological analysis, the neoplasm was classified as grade I meningothelial, which is considered a benign meningioma, but its behavior is considered malignant due to the compression of the spinal cord and the impossibility of removal with surgical margins, as recommended for oncological surgeries. The patient's survival after surgical treatment is in accordance with that described by other authors which varies from 2.2 to 47 months. Radiotherapy seems to improve the prognosis, but this therapeutic modality is not easily available in the country. There is also insufficient information on the use of chemotherapy for this type of neoplasia, or on the relationship between tumor graduation and survival. The surgery was proposed in order to confirm the suspicion, decompress the spinal cord and collect material for biopsy; the technique performed is feasible and no intraoperative complications have occurred.
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