Anatomic Basis for Minimally Invasive Resection of Intradural Extramedullary Lesions in Thoracic Spine.

Abstract

Since the first resections of intradural extramedullary neoplasms, neurosurgeons have tended to preserve as much of the integrity of the spine as possible while ensuring a safe corridor to resect these lesions. A dimensional analysis of intradural lesions superimposed on a dimensional analysis of the thoracic canal would provide the anatomic basis for a minimal access approach. The authors report the results of such an analysis on a series of patients with intradural extramedullary lesions. A retrospective analysis was undertaken of 26 thoracic intradural extramedullary lesions managed with open or minimally invasive resection. The size of each lesion was measured in the rostrocaudal, lateral, and anteroposterior dimensions and then averaged and compared with reported dimensions of the thoracic spinal canal. The mean (range) dimensions of the surgically resected thoracic lesions were 18.6 mm (10-25 mm) for rostrocaudal, 13.0 mm (7-18 mm) for lateral, and 13.6 mm (9-17 mm) for anteroposterior. No patient had any evidence of thoracic canal remodeling. Thoracic intradural extramedullary lesions become symptomatic as they approach the limits of the thoracic canal, resulting in an inherent dimensional limitation in the rostrocaudal, lateral, and anteroposterior dimensions. Displacement of the spinal cord by the lesion to one side further favors a minimally invasive unilateral approach. A paraspinal unilateral hemilaminectomy approach with a 35× 20 mm exposure centered over the lesion offers a safe surgical corridor for resection while preserving the posterior tension band, facet complexes, and paraspinal musculature.