Spinal cord herniation following cervical meningioma excision: a rare clinical entity and review of literature

Description of the Diversity in Surgical Indication and Surgical Strategies for Primary Spinal Cord Tumors: A Nationwide Survey by the Neurospinal Society of Japan

OBJECTIVE

To assess the current management of primary spinal cord tumors (PSCTs) and determine whether and to what extent there are differences in surgical strategies for PSCTs.

METHODS

The Neurospinal Society of Japan conducted a survey between April 1 and 30, 2021. Certified spine surgeons were requested for information on the frequency of surgeries in 2020 and the surgical strategies adopted for each PSCTs. The following tumor histologies were focused: schwannoma, meningioma, and cauda equina tumor as extramedullary tumors; and ependymoma, hemangioblastoma, astrocytoma, and cavernoma as intramedullary tumors. The participants were divided according to their response as follows: experts, who had experienced ≥ 100 surgeries for PSCTs, and nonexperts.

RESULTS

Among 308 participants (63%), 35 (11%) were experts. The total number of PSCTs in 2020 was 802 of which 564 tumors were extramedullary and 223 were intramedullary. Schwannoma accounted for 53% of the extramedullary tumors, and ependymoma accounted for 39% of the intramedullary tumors. Surgical strategies significantly differed among both the experts and nonexperts groups. Some discrepancies in the adopted surgical strategies were observed between groups. Some of the nonexperts, and none of the experts, ruled out surgery for schwannomas (Eden type 4), astrocytomas, or cavernomas. Five nonexperts (2.2%), and none of the experts, resected the entire dura for meningiomas.

CONCLUSION

A nationwide survey revealed that a sufficient consensus did not exist regarding surgical strategies for PSCTs. A disease-specific registry for PSCTs is necessary in academic societies.

Case Report: Idiopathic Spinal Cord Herniation: An Overlooked and Frequently Misdiagnosed Entity

Background

Idiopathic spinal cord herniation is an extremely rare entity that is characterized by protrusion of the spinal cord through a defect in the ventral dura. Due to the paucity of enough clinical evidence, the treatment and prognosis of idiopathic spinal cord herniation are still elusive. Herein, we reported a case of idiopathic spinal cord herniation occurring at the C7–T1 levels that was treated by surgical reduction.

Case description

A 44-year-old Chinese woman presented with a 5-year history of numbness and weakness in the bilateral lower limbs. Spinal magnetic resonance imaging demonstrated ventral displacement of the spinal cord at the C7–T1 levels, and there seemed to be a cuneiform space-occupying lesion dorsal to the spinal cord. A diagnosis of the spinal intradural extramedullary tumor was suspected. An exploratory operation was performed via a posterior midline approach. Intraoperatively, we found a defect in the ventral dura through which the spinal cord herniated to the epidural space. After the herniated parenchyma was returned, an artificial dura matter was used to repair the defect. The postoperative course was uneventful. After a 3-month follow-up, the lower-extremity weakness was significantly improved, and there was no recurrence of the spinal cord herniation.

Conclusion

Preoperative diagnosis of idiopathic spinal cord herniation is exceedingly challenging. Surgical reduction of the herniated spinal cord with the repair of the dural defect is an effective approach for the treatment of this rare disorder, and the surgical outcome is favorable.

Posterior Surgical Approach for Ventral Cervical Spinal Cord Herniation: 2-Dimensional Operative Video

Spinal cord herniation (SCH) is a rare condition that is typically of idiopathic origin. Although SCH is mostly found in the thoracic region because of a dural defect, there are some reports of cervical SCH following surgery or trauma.1-3 Spinal cord tethering can be a result of SCH or as a standalone issue.4,5 These conditions can lead to progressive neurological deficits, including numbness, gait disturbances, and decreased muscle strength, requiring surgical correction. There are limited reports of surgical procedures for ventral SCHs. Several reports exist using a ventral approach for intradural tumors, but it is not commonly employed because of the inability to obtain adequate dural closure.6 Much of the literature on SCH comes from idiopathic and congenital cases in the thoracic spine.7,8 Posterior and posterolateral approaches for a ventral thoracic SCH have been described, as well as an anterior approach for a ventral cervical SCH.9-12 In this video, we describe a posterior approach for a ventral cervical SCH. A 38-yr-old male presented with progressive cervical myelopathy 9 yr after a C2-C3 schwannoma resection requiring an anterior approach and corpectomy of C3 with partial corpectomies of C2 and C4. A preoperative magnetic resonance imaging showed a ventrally herniated spinal cord at the top of the C3 vertebral body and below the C4 vertebral body. Informed consent was obtained. The posterior surgical approach involved a C1-C5 laminectomy, sectioning the dentate ligament, ventral cord untethering, removal of residual tumor, and placement of a ventral sling. A significant improvement in sensory and motor function was observed postoperatively.

Late Cervical Spinal Cord Herniation Resulting from Post-Traumatic Brachial Plexus Avulsion Injury

BACKGROUND

Spinal cord herniation (SCH) is often described as occurring spontaneously in the thoracic spine, with few cases of cervical SCH reported as a late complication of traumatic brachial plexus avulsion. We present 2 cases of nerve root avulsion and pseudomeningocele formation, resulting in delayed cervical SCH and neurologic deterioration.

CASE DESCRIPTION

Case 1: A 37-year old man presented with progressive leg weakness 2 years after experiencing traumatic C8 and T1 root avulsions. Magnetic resonance imaging (MRI) showed previously documented C8-T1 nerve avulsions with new SCH in a T1 pseudomeningocele. A C7-T1 costotransversectomy and C4-T4 instrumented fusion were completed, allowing SCH reduction and patch graft repair of the dural defects without the need for adhesiolysis. At last follow-up, the patient's leg weakness had resolved. Case 2: A 32-year old man presented with progressive right arm numbness, weakness, and signs of myelopathy 9 years after experiencing C8 and T1 root avulsions. MRI showed previously documented root avulsions and new SCH with extensive and compressive pseudomeningocele formation. A C7 transpedicular approach with C5-T1 instrumented fusion was completed for dural repair. A large pseudomeningocele was found and drained on drilling the C7 pedicle, and adhesiolysis was required at the spinal cord avulsion site to reduce the SCH and allow patch graft repair. At last follow-up, the patient's right arm weakness was improving, although numbness persisted.

CONCLUSIONS

SCH is a rare cause of delayed neurologic deterioration after brachial plexus avulsion, with few case reports describing its occurrence. We present 2 cases of this complication and describe its successful surgical treatment through dural repair after instrumented fusion.

The Pathogenesis of Ventral Idiopathic Herniation of the Spinal Cord: A Hypothesis Based on the Review of the Literature

Idiopathic ventral herniation of the spinal cord (SC) is not often encountered in daily practice. Its clinical prevalence, however, will increase through increasing awareness and more frequent use of MRI. A clear explanation of its pathophysiology has never been formulated. It was hypothesized that the findings during surgery might indicate the real causative mechanism. An extensive literature search was performed, using Embase, PubMed, and Google Scholar. Titles and abstracts were screened by two investigators, using strict inclusion and exclusion criteria. Reference lists of the full paper versions of each included article were checked. The following data were registered for the articles included: age, gender, level of herniation, relation to intervertebral disk, duration of symptoms, findings from surgery, and outcomes. Nine cases treated at our department were added. A total of 117 articles reporting on 259 patients were included. Including our cases, 268 patients were reviewed. Females outnumbered males (160/100). The mean age was 51.3 ± 12.0 years. In 236 patients, the duration of symptoms was reported: 55.5 ± 55.6 months. In 178 patients, the intraoperative findings for the herniated part of the SC were not mentioned. In 59 patients, a tumor-like extrusion was seen, without any alteration to the SC. Deformation of the SC itself was never observed. Biopsies of these structures were without clinical consequence. Based on the intraoperative findings reported in literature and the cases presented, acquired causes, such as trauma and erosion of the dura due to a herniated disk, were not plausible. We hypothesize that a non-functioning appendix to the SC can only develop during an early embryologic phase, in which several layers separate. We propose renaming this entity as congenital transdural appendix of the SC.