Patients with Spinal Ependymomas Attached to the Anterior Median Septum are at Risks for Postoperative Functional Impairment : A Correlating Analysis

Abstract

When operating on spinal ependymomas, careful dissection of tumors in the ventral attachment is important because the tumor-feeding arteries and the central vessels of the cord, both of which branch from the anterior spinal artery, are located close to the anterior median septum(AMS), which is an extension of the pia in the cord. In this study, we examined the clinical features of tumor attachment to the AMS. We divided 10 patients who underwent total removal of spinal ependymomas into 2 groups based on the ventral attachment of their tumors. In Group A(n=5), the tumor was attached to the AMS, and in Group B(n=5), it was not attached to the AMS. We recorded the patients’ modified McCormick grades at the time of admission, immediately, and 4 weeks after surgery. Pre-and postoperative changes in their functional status were evaluated by a deterioration/amelioration scoring system where 0=no change of grade, -1,-2=deterioration by 1 or 2 grades, and +1=improvement by 1 grade. We compared the scores recorded for Group A and B patients just after and 4 weeks after surgery. In addition, we compared the motor evoked potentials(MEPs), preoperative magnetic resonance imaging(MRI)results(proportion of the tumor to the cord, intratumoral cyst, and syrinx), and pathological findings(anaplastic changes and MIB-1 index)in the 2 groups. In group A, tight adhesion of the tumor to the AMS rendered selective division of the feeding arteries difficult. The mean deterioration/amelioration scores immediately and 4 weeks after surgery were -1.2(range 0 to -2)and -0.6(range +1 to -2), respectively in Group A. They were -0.8 (range 0 to -2)and +0.2(range +1 to -1) respectively in Group B. Four weeks after surgery, one patient of Group A was scored -2, whereas no patient of Group B had a score of -2. Both groups, manifested decreases in MEP amplitudes. There were no specific MRI and pathological findings pertinent to the pattern of a attachment to the septum. Tumors with adhesion to the AMS raise the risks of damage to the central vessels, tend to produce deterioration, and result in delayed postoperative recovery. Careful dissection that is based on an understanding of the anatomical relationship between the AMS and the central vessels and feeding arteries facilitates the safe detachment of these tumors from the AMS. (Received:October 15, 2012;accepted:April 8, 2013)