Case Report: The Coronal Magnetic Resonance Imaging of Three-Dimensional Fast-Field Echo With Water-Selective Excitation Can Identify the Wrapping of Spinal Nerve Fibers Into Subdural Tumors Prior to Operation

Abstract

Purpose: In the present study, the authors intend to identify the spatial relationship between subdural tumors and spinal nerve fibers of cauda equina prior to operation using the coronal MRI of three-dimensional fast-field echo with water-selective excitation (CMRI).

Methods: In total, 30 case series with surgically and pathologically verified subdural tumors were enrolled in the present study. The spatial relationship between subdural tumors and spinal nerve fibers of the cauda equina was assessed via conventional MRI and CMRI by three experts prior to operation. The spatial relationship between subdural tumors and spinal nerve fibers of the cauda equina was classified using CMRI. The accuracy of imaging observation was determined via intraoperative observation.

Results: Though conventional MRI and gadolinium (Gd)-enhanced MRI (Gd MRI) cannot identify the spatial relationship between subdural tumors and spinal nerve fibers of cauda equina in all cases, CMRI can identify it prior to operation and divide the spatial relationship of spinal nerve fibers of cauda equina with subdural tumors into three types. CMRI shows higher sensitivity (97.44%) and specificity (90.47%) in identifying the spatial relationship of spinal nerve fibers of cauda equina with subdural tumors. Additionally, CMRI also showed a substantial agreement with a kappa value of 0.78.

Conclusion: Herein, the authors first describe a potential novel application that CMRI can successfully identify the spatial relationship between subdural tumors and spinal nerve fibers of cauda equina prior to operation, which play an essential role in making a prudent surgical plan and preventing postoperative nerve damage.

Summary: Intraoperative observation confirms spinal nerve fibers of cauda equina are often wrapped into subdural tumors of the thoracolumbar and lumbar region, which can result in a high rate of sensory and motor dysfunction after the operation due to the unconscious about the wrapping of nerves into subdural tumors prior to operation. To date, there is not an effective strategy to identify the wrapping before operation.

Keywords: cMRI; cauda equina; sensitivity; specificity; subdural tumors.

Figure 1

(A) A subdural mass with hypersignal T1 and T2 was identified on a segment of L2 in a 55-year-old man via T2-weighted MRI prior to operation. (B) The mass presented inhomogeneous enhancement via Gd MRI. (C) Though both preoperative MRI and Gd MRI did not identify the spatial relationship between the tumor and spinal nerve fibers of cauda equina, the CMRI clearly showed that no nerve fibers enter or pass through the tumor. (D) Based on the spatial relationship between the tumor and the spinal nerve, the case was considered type I according to the pattern diagram. (E) As expected, an intraoperative observation confirmed that no nerve fibers passed through the tumor (type I). (F) The mass was totally resected and confirmed to be schwannoma by postoperative pathology.

Figure 2

(A) A subdural mass with hypersignal T1 and T2 was identified on a segment of T12 in a 58-year-old man via preoperative MRI. (B) The mass presented inhomogeneous enhancement via Gd MRI. (C) Though both preoperative MRI and Gd MRI did not identify the spatial relationship between the tumor and the spinal nerve, the CMRI clearly showed that a part of the nerves enter the tumor and terminate at the end of the tumor. (D) Based on the spatial relationship between the tumor and the spinal nerve, the case was considered type II according to the pattern diagram. (E) As expected, an intraoperative observation confirmed that a part of the nerves enters the tumor and terminates at the end of the tumor (type II). (F) The mass was resected and confirmed to be schwannoma by postoperative pathology.

Figure 3

(A) A subdural mass with hypersignal T1 and T2 was identified on a segment of T12 in a 27-year-old man via T2-weighted MRI prior to operation. (B) The mass presented inhomogeneous enhancement via Gd MRI. (C) Though both preoperative MRI and Gd MRI did not identify the spatial relationship between the tumor and the spinal nerve, the CMRI clearly showed that the spinal nerves pass through the tumor. (D) Based on the spatial relationship between the tumor and the spinal nerve, the case was considered type III according to the pattern diagram. (E) As expected, an intraoperative observation confirmed that nerve fibers passed through the tumor (type III). (F) The mass was removed and confirmed to be schwannoma by postoperative pathology.