Application of intraoperative ultrasound in microsurgical treatment of intramedullary ependymoma and astrocytoma of the spinal cord

Objective To evaluate the role of intraoperative ultrasound (IoUS) in the microsurgical treatment of intramedullary ependymoma and astrocytoma of the spinal cord. Methods A retrospective review was performed on 78 cases of intramedullary ependymoma and 34 cases of intramedullary astrocytoma which were treated microsurgically between January 2010 and May 2018 at Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology. All cases of ependymoma or astrocytoma were divided into IoUS group(44 cases of ependymomas, 18 cases of astrocytomas) and control group(34 cases of ependymomas, 16 cases of astrocytomas) according to whether IoUS was employed during operation. All patients were followed up in the clinic or by telephone to assess tumor recurrence and spinal function recovery by radiographic reexamination and Modified McCormick Scale (MMS), which were then compared between IoUS and control group in ependymomas and astrocytomas, respectively. The accuracy of intraoperative ultrasound in evaluating the gross total resection (GTR) rate was also evaluated. Results No significant differences were observed in age, sex, presenting symptoms, MMS or spinal cord segment of tumor location between IoUS and control groups in ependymoma or astrocytoma (all P>0.05). Compared with control group in ependymoma, the IoUS group had slightly higher GTR rate [97.7% (43/44) vs. 91.2% (31/34)], slightly higher rate of good outcomes in terms of spinal function [36.4% (16/44) vs. 32.4% (11/34)] and slightly lower incidence of complications [8.8% (3/44) vs. 11.8% (4/34)], which, however, were not significantly different (all P>0.05). For astrocytoma, the IoUS group had significantly higher GTR rate [16/18 vs. 9/16, P 0.05] and slightly lower incidence of complications [0/18 vs. 2/16, P>0.05] compared with control group. However, those differences were not significant (P>0.05). Postoperative enhanced MRI was used as the gold standard for verification of GTR. The accuracy rate of IoUS for prediction of GTR was 97.7% (43/44) in ependymoma and 14/16 in astrocytoma. Conclusion The intraoperative ultrasound technique could facilitate the real-time and accurate judgement of tumor resection extent, which might have greater application value in the astrocytoma. Key words: Ependymoma; Astrocytoma; Microsurgery; Intraoperative ultrasound; Intrame-dullary tumor