Minimally Invasive Resection of Intradural-Extramedullary Spinal Neoplasms

To the Editor: We read the article “Minimally invasive resection of intradural-extramedullary spinal neoplasms” by Tredway et al. (8) with great interest. The unilateral approach to spinal tumors was pioneered by Chiou et al. (2) and Yaşargil et al. (9). Since then, a number of other authors have reported significant series (4, 6, 7), all of which stressed the prevention of instability, the unnecessity of postoperative external bracing, the reduction of postoperative pain and distress, the advantaged of early mobilization, and the reduction of hospital stay and overall costs. Tredway et al. use a nice, self-retaining retractor for their operations, along with a paramedian incision and unilateral laminectomy for one-two level. We do not understand why they extend their approach contralaterally under the spinous process to the contralateral ligamentum flavum and, eventually, to the contralateral lamina. The concept of minimally invasive surgery may be rather lost with this technique, which may also be time consuming and unnecessary. We think they may do it to permit a median dural incision. Clinical data and biomechanical studies show that bilateral disruption and damage to paraspinal muscles and ligaments might favor postoperative instability and kyphosis (1, 3). We operated on 10 patients with dorsolumbar neurofibroma between June 2000 and June 2002 (5). To date, we have operated on 22 patients for spinal neurofibroma using a strictly unilateral approach. We do a midline incision and retract the paraspinal muscles laterally, exposing the ligamentum flavum and the upper and lower laminae. A limited laminectomy is then performed with a high-speed drill and/or rongeurs. The dural opening should be paramedian. The identification of the tumor and of the affected root is then rather easy. The tumor can be removed “en bloc” if it is smaller than 2 cm or after internal debulking if it is larger. The closure of the dura is performed with 5.0 or 6.0 stitches. The operating time varies between 100 and 210 minutes (average, 140 min). Careful positioning of the patient and radioscopic identification of the level are mandatory. It should be noted that, in the prone position, the tumor will generally be found approximately 1 cm more cranially than observed on the MRI scans due to the mobility of the cord in the spinal canal. This is particularly evident in lower spinal tumors. Tredway et al. affirm that this series is their “learning curve.” We think that they should be able to do a real “unilateral approach” to intradural-extramedullary tumors that are, as they emphasize, eccentric in position. In experienced hands, the minimally invasive technique should become the one of choice for all extramedullary-intradural tumors, particularly neurofibromas. Alfredo Pompili Fabrizio Caroli Stefano Telera Emanuele Occhipinti Rome, Italy