The precise midline myelotomy through anatomical posterior median septum by dissecting dorsal column in microsurgical resection of ependymoma (2-dimensional operative video)

Although resection is the gold standard treatment for spinal ependymoma, permanent neurological deterioration has been reported postoperatively in 20%–27% of patients. Despite thorough dissection of the tumor from its surroundings, conventional longitudinally directed midline myelotomy can lead to injury to the dorsal column, possibly due to deformation of the posterior median septum as the tumor grows. To address this issue, the authors have been performing precise midline myelotomy through the anatomical posterior median septum by directly dissecting the dorsal column. This video presents the principles and application of this technique.

we choose to dissect dorsal column directly when doing midline myelotomy because posterior median septum is not linear and not vertical.Further explanations of this will be covered on the next page.
1:59 Explanation on Deformation of Posterior Median Septum.As you can see in the picture, the exposed posterior median septum is not linear.And the figure shows that the posterior median septum is oblique rather than vertical.Even in cases where the tumor is located centrally within the spinal cord and spinal cord rotation is not present, it is likely that the growth of the tumor caused deformation of the posterior median septum, resulting in an oblique orientation.
2:29 Risk of Procedure and Its Potential Benefit.During midline myelotomy, there is a risk of dorsal column injury, and other additional neural damage may occur during dissection of the tumor.By dissecting the dorsal column during midline myelotomy, we can safely approach the lesion with minimal neural tissue damage, as mentioned earlier.[3][4]   Although resection is the gold standard treatment for spinal ependymoma, permanent neurological deterioration has been reported postoperatively in 20%-27% of patients.Despite thorough dissection of the tumor from its surroundings, conventional longitudinally directed midline myelotomy can lead to injury to the dorsal column, possibly due to deformation of the posterior median septum as the tumor grows.To address this issue, the authors have been performing precise midline myelotomy through the anatomical posterior median septum by directly dissecting the dorsal column.This video presents the principles and application of this technique.
3:47 Description for the Setup (Key Surgical Steps).After midline skin incision and subperiosteal muscle dissection, laminotomy was performed with a high-speed drill.After the dura was exposed, midline durotomy and arachnoidotomy was performed.The rest of the procedures are going to be demonstrated in the operative video.

4:09 Midline Myelotomy (Dorsal Column Dissection).
To tell you about the process of midline myelotomy, first of all, we accurately delineated the posterior median sulcus by careful inspection of surrounding structures such as posterior median spinal vein, contour of dorsal column, and dorsal root entry zones at both sides.After pial membrane-only incision, precise dorsal column dissection was done, maintaining the structural integrity of the dorsal columns.Finally, the tumor was exposed after carefully dissecting the overlying dorsal column from the tumor.
4:51 Identification of Posterior Median Sulcus.After coagulating the posterior median vein, pial membrane incision was done in midline and posterior median sulcus between bilateral dorsal columns was identified.
5:08 Identification of Posterior Median Septum.As we dissected the dorsal columns from each other, posterior median septum became more prominent.
5:20 Dorsal Column Dissection.Extending the posterior median septum developed previously, the dorsal column dissection for the planned level was done.
5:48 Exposure of Tumor.After that, the tumor was shown behind the ependymal lining.
5:55 Deformation of Posterior Median Septum.The posterior median septum was deviated to the right because tumor was sprouted from left side, so the dorsal surface of tumor was covered by left dorsal column.
6:09 Dissection of Overlying Left Dorsal Column.When you dissect the overlying dorsal column, particular attention should be paid for dorsal column injury.
6:24 Identification of Caudal End of Tumor.After the entire length of the tumor was exposed, the caudal end of the tumor was identified.
6:36 En Bloc Removal of the Tumor.From caudal to cephalad, the tumor was dissected from surrounding tissue and en bloc removal of the tumor was done.
6:53 Preserved Bilateral Dorsal Column.After tumor removal, bilateral dorsal column was intact.Intraoperative neuromonitoring such as MEP and SSEP show no change until the very end of surgery.
7:33 Disease Background: Ependymoma.7][8] WHO grade II or III comprise up to 75% and 11% of all adult spinal ependymoma cases, respectively. 92][3][4] Although grosstotal resection is a primary target of surgery, permanent neurological decline was observed 20%-27% of patients. 5,6:18 A Brief Review of Outcome.After the surgery, the patient maintained good swallowing and gait functions.Bilateral hip flexion motor power was improved from grade 4 to grade 5.There is nearly no newly developed neurological deficit postoperatively except for bilateral foot hypesthesia.Postoperative contrast-enhanced MR image revealed total resection of the tumor without any complicating features.