Anterior Transthoracic Surgery with Motor Evoked Potential Monitoring for High-Risk Thoracic Disc Herniations: Technique and Results

[Thoracic disc herniation]

Contrary to traditional opinion thoracic herniation is more frequent than expected. The disease poses two main challenges: (1) surgical removal and (2) early and correct diagnosis. It is without a doubt that herniated thoracic discs can be difficult to remove. Often enough, it is equally challenging to attribute the correct symptoms to the disease to reach the diagnosis, because there is a great variability and supposedly low specificity of the clinical symptoms, especially concerning pain related symptoms, which are often attributed to muscular or joint related causes. However, radicular complaints and myelopathic deficits usually predominate, but also algetic symptoms exist in patients harboring this disease. The surgical approach should be a ventral one. The postoperative prognosis is mostly good after adequate decompression.

Accuracy of Intraoperative Neuromonitoring in the Diagnosis of Intraoperative Neurological Decline in the Setting of Spinal Surgery-A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVES

In an effort to prevent intraoperative neurological injury during spine surgery, the use of intraoperative neurophysiological monitoring (IONM) has increased significantly in recent years. Using IONM, spinal cord function can be evaluated intraoperatively by recording signals from specific nerve roots, motor tracts, and sensory tracts. We performed a systematic review and meta-analysis of diagnostic test accuracy (DTA) studies to evaluate the efficacy of IONM among patients undergoing spine surgery for any indication.

METHODS

The current systematic review and meta-analysis was performed using the Preferred Reporting Items for a Systematic Review and Meta-analysis statement for Diagnostic Test Accuracy Studies (PRISMA-DTA) and was registered on PROSPERO. A comprehensive search was performed using MEDLINE, EMBASE and SCOPUS for all studies assessing the diagnostic accuracy of neuromonitoring, including somatosensory evoked potential (SSEP), motor evoked potential (MEP) and electromyography (EMG), either on their own or in combination (multimodal). Studies were included if they reported raw numbers for True Positives (TP), False Negatives (FN), False Positives (FP) and True Negative (TN) either in a 2 × 2 contingency table or in text, and if they used postoperative neurologic exam as a reference standard. Pooled sensitivity and specificity were calculated to evaluate the overall efficacy of each modality type using a bivariate model adapted by Reitsma et al, for all spine surgeries and for individual disease groups and regions of spine. The risk of bias (ROB) of included studies was assessed using the quality assessment tool for diagnostic accuracy studies (QUADAS-2).

RESULTS

A total of 163 studies were included; 52 of these studies with 16,310 patients reported data for SSEP, 68 studies with 71,144 patients reported data for MEP, 16 studies with 7888 patients reported data for EMG and 69 studies with 17,968 patients reported data for multimodal monitoring. The overall sensitivity, specificity, DOR and AUC for SSEP were 71.4% (95% CI 54.8-83.7), 97.1% (95% CI 95.3-98.3), 41.9 (95% CI 24.1-73.1) and .899, respectively; for MEP, these were 90.2% (95% CI 86.2-93.1), 96% (95% CI 94.3-97.2), 103.25 (95% CI 69.98-152.34) and .927; for EMG, these were 48.3% (95% CI 31.4-65.6), 92.9% (95% CI 84.4-96.9), 11.2 (95% CI 4.84-25.97) and .773; for multimodal, these were found to be 83.5% (95% CI 81-85.7), 93.8% (95% CI 90.6-95.9), 60 (95% CI 35.6-101.3) and .895, respectively. Using the QUADAS-2 ROB analysis, of the 52 studies reporting on SSEP, 13 (25%) were high-risk, 10 (19.2%) had some concerns and 29 (55.8%) were low-risk; for MEP, 8 (11.7%) were high-risk, 21 had some concerns and 39 (57.3%) were low-risk; for EMG, 4 (25%) were high-risk, 3 (18.75%) had some concerns and 9 (56.25%) were low-risk; for multimodal, 14 (20.3%) were high-risk, 13 (18.8%) had some concerns and 42 (60.7%) were low-risk.

CONCLUSIONS

These results indicate that all neuromonitoring modalities have diagnostic utility in successfully detecting impending or incident intraoperative neurologic injuries among patients undergoing spine surgery for any condition, although it is clear that the accuracy of each modality differs.PROSPERO Registration Number: CRD42023384158.

Giant calcified thoracic disk herniations: ossification of PLL or autonomous entity?

BACKGROUND

Giant calcified thoracic disk herniation (GCTD) is an uncommon event, which requires surgical treatment in less than 1% of patients. GCDTs are a specific subgroup of herniated thoracic disks occupying more than 40% of the spinal canal showing calcifications associated with a certain degree of ossification. In this paper, we are reporting our whole experience in the surgical management of GCTDs through anterior approaches. We believe that they present characteristics that associate them to the circumscribed type of ossified posterior longitudinal ligament (OPLL) with a possible common pathophysiology consisting in the dural violation.

METHODS

Twenty-three consecutive patients with GCDTs were managed through anterior approaches during the period 1996-2019 at the Niguarda Hospital, Milan, Italy. Clinical data, radiological features, surgical reports, histological findings, and outcomes were reviewed.

RESULTS

There was no mortality, whereas permanent morbidity consisted of 1 case of worsened paraparesis due to accidental spinal cord contusion. One patient required reoperation to repair a postoperative cerebrospinal fluid (CSF) leakage. All patients underwent postoperative MRI which showed excellent decompression of cord and dural sac in all cases. Histological study of en-bloc removed GCTD showed typical calcification patterns of the PLL.

CONCLUSIONS

GCDTs may be assimilated to the so-called "circumscribed type" of OPLL. The GCDTs may show the same radiological CT and MRI pattern of OPLL. The anterior accesses now represent the standard of care for GCTDs. The use of operative microscope and intraoperative monitoring is mandatory. The risk of CSF leakage can be markedly reduced by meticulous reconstruction of the dura and the placement of spinal drainage. Adequate exposition may sometimes require one or two levels of corpectomy with consequent vertebral body reconstruction and fixation of anterior column of the spine.

Thoracoscopic Microdiscectomy with Preservation of Rib and Costovertebral Joint

INTRODUCTION

Thoracic disc herniations (TDH) may cause major morbidity. While thoracoscopic microdiscectomy (TMD) is an excellent technique, postoperative band-like pain is an important drawback.

MATERIAL AND METHODS

We performed 181 consecutive TMDs (including 39 high-risk cases) with preservation of rib and costovertebral joint (CVJ). We shave a few mm of the rib, drill straight to target, and avoid opening the canal before the TDH is completely free and (in case of giant TDHs) internally debulked, creating initial decompression and limiting epidural venous oozing. Subsequently, we gently mobilize and remove the residual TDH while avoiding leverage.

RESULTS

Skin-to-skin time was <90' in 64, 90-120' in 48, >120' in 20, unknown in 10, and 162' mean in 39 high-risk procedures. Blood loss was <100 mL in 76, <250 mL in 48, and 537 mL mean in 39 high-risk procedures. The technique was successfully applied in all (including nine dural repairs) without a single conversion. We observed an increased neurological deficit in two (1.1%) and inadequate decompression in merely one (wrong level). Complications (mainly pulmonary) were few and managed conservatively, except for a segmental artery pseudoaneurysm treated endovascularly. We observed a substantial decrease in acute and chronic postoperative pain.

DISCUSSION

The technique is fast, straightforward, minimizes bone resection and blood loss, improves orientation, safely and effectively deals with any TDH, and prevents postoperative band-like pain as the CVJ is preserved.

CONCLUSION

We hope this technique will find broader acceptance among a new generation of spine surgeons to benefit patients suffering TDH-related myelopathy or merely intractable pain.

T3-T4 Disc Herniations: Clinical Presentation, Imaging, and Transaxillary Approach

OBJECTIVE

To describe a cohort of T3-T4 thoracic disc herniations (TDHs), their clinical and radiologic characteristics, and unique thoracoscopic transaxillary approach (TAA).

METHODS

All patients operated on for a T3-T4 TDH with minimal follow-up of 1 year were selected.

RESULTS

Eight TAA procedures (6 males and 2 females) were included (1.4%). Six patients reported axial pain, irradiating in 2, 4 sensory changes, 1 objective and 1 merely subjective motor weakness. Only 1 TDH was calcified, none was giant, 2 were accompanied by myelomalacia, and 2 by a small segmental syrinx. A cardiothoracic surgeon helped with exposure through a curved axillary incision using anterior cervical and more recently double-ring wound retractors. All patients were operated on using a 10-mm 30° rigid (three-dimensional) high-definition scope. There were no major complications and a good outcome with symptomatic relief in 7 of 8 patients.

CONCLUSIONS

T3-T4 TDHs are infrequent but may be underdiagnosed because they tend to be small and their signs and symptoms may mimic a cervical problem involving the shoulders and even the arms. There may be a male predominance. The TAA is straightforward, safe, efficacious, and well tolerated despite the supposed vulnerability of the upper thoracic spinal cord. Dissection between large crowded subpleural veins characteristic for the upper thoracic spine and ensuring adequate dura decompression when the steep angle may partially obscure the tip of the instruments does require some extra time. Thorough knowledge of the unique anatomy of the upper thorax is mandatory and the assistance of a cardiothoracic surgeon is highly recommended.

Incidence and degrees of neurologic decline following thoracic costotransversectomy

BACKGROUND CONTEXT

Thoracic costotransversectomies (TCT) are amongst the most invasive spine procedures performed. Of greatest concern to the patient and surgeon is the risk of iatrogenic neurologic injury associated with these procedures. Most available studies limit their assessment of neurologic function to nonspecific scales such as the broader ASIA scoring system of A to E and have not comprehensively described the rates of iatrogenic injury following these procedures by looking more precisely with ASIA motor scoring (0-100) which allows for more in-depth analysis.

PURPOSE

The purpose of this study is to investigate the rates and degree of iatrogenic neurologic decline following TCT and subsequent rates and degree of motor recovery.

STUDY DESIGN/SETTING

Retrospective medical record review at a single institution.

PATIENT SAMPLE

Around 116 consecutive patients undergoing TCT operations.

OUTCOME MEASURES

Neurological changes from preprocedure to final follow-up assessed by lower extremity motor score.

METHODS

A retrospective chart review of patients undergoing TCT between May 2008 and April 2018 was carried out. Clinical, surgical, and intraoperative neuromonitoring data were collected. Patients who demonstrated an initial postoperative decline in lower extremity motor scores (LEMS) were followed through their final follow up to assess recovery.

RESULTS

Around 116 patients underwent TCT between T2 and T12 between May 2008 and April 2018. Seven (6.0%) patients demonstrated an immediate postoperative decline as defined by a drop of more than 4 points (mean 15.1; range 5-50) in motor score. All patients who demonstrated an initial postoperative motor score decline returned to within 4 LEMS points of their preoperative LEMS by final follow up. IOMN changes were noted only in half of all monitored patients who were noted to have a decline.

CONCLUSIONS

In our series, 6.0% of patients undergoing TCT experienced an initial decline in motor score with 94.0% demonstrating an unchanged or improved examination compared to preoperative exam. In our series, all patients who exhibited a decline recovered to within 4 points of the preoperative motor score within the first year postoperatively.

Trans-thoracic versus retropleural approach for symptomatic thoracic disc herniations: comparative analysis of 94 consecutive cases

PURPOSE

The authors illustrate their results in the surgical treatment of symptomatic thoracic disc herniations (TDHs) by comparing the traditional open to the less invasive retropleural lateral approaches.

METHODS

Retrospective review of 94 consecutive cases treated at a single Institution between 1988 and 2014. Fifty-two patients were males, 42 females, mean age was 53.9 years. Mean follow-up was 46.9 months (12-79 months). 33 patients were diagnosed with a giant thoracic disc herniation (GTDH). Upon admission, the most common symptoms were: motor impairment (91.4%, n = 86), neuropathic radicular pain with VAS > 4 (50%), bladder and bowel dysfunction (57.4% and 41.4% respectively) and sensory disturbances (29.7%). The surgical approach was based upon level, laterality and presence or absence of calcified lesions.

RESULTS

Decompression was performed in 7 cases via a thoraco-laparo-phrenotomy and in 87 cases via an antero-lateral thoracotomy. Out of the latter cases, 49 (56%) were trans-thoracic trans-pleural approaches (TTA) and 38 (44%) were less invasive retropleural approaches (MIRA). At follow-up, there were 59.5% neurologically intact patients according to the McCormick Scale, while 64.8% and 67% had no bladder or bowel dysfunction respectively. Complications occurred in 24 patients (25.5%). Pulmonary complications were the commonest (12.7%) with pleural effusion being significantly more common in patients treated with TTA compared to MIRA (20% vs 5.2%: X² 4.13 P:0.042). Severe post-operative neuralgia (VAS 7-10) was also significantly more frequent in the TTA group (22.4% vs 2.6% X² 7.07 p 0.0078).

CONCLUSIONS

MIRA is a safe and effective technique to obtain adequate TDH decompression and is associated with lower morbidity compared to TTA.

Transdural Thoracic Disk Herniation with Longitudinal Slitlike Dural Defect Causing Intracranial Hypotension: Report of 2 Cases

BACKGROUND

Intracranial hypotension (IH) has a widely variable clinical and radiologic presentation. Secondary IH may be caused by degenerative spine disorders and in particular by thoracic disk herniations (TDHs).

METHODS

We present 2 patients with a transdural TDH, a secondary IH, and superficial siderosis in 1.

RESULTS

Case 1 presented with headache, cognitive decline, staggering gait, bilateral subdural effusions, cerebral sagging, an extradural spinal cerebrospinal fluid (CSF) collection suggesting secondary IH, and a calcified TDH at T9-T10. Case 2 presented with intermittent pain at the craniocervical junction provoked exclusively by specific physical activities, superficial siderosis mainly in the posterior fossa, an extradural spinal CSF collection, and a calcified TDH at T7-T8 yet no intracranial signs of IH. In both cases, using strict thoracoscopic technique, we removed a transdural TDH and reconstructed an underlying longitudinal slitlike dural defect with smooth lining. Follow-up magnetic resonance imaging scans confirmed a dramatically improved situation without residual extradural intraspinal CSF collection or signs of IH.

CONCLUSIONS

This paper adds to the evidence that some cases of IH and even superficial siderosis are caused by transdural erosion of a TDH that may be otherwise asymptomatic. The dura may degenerate due to chronic compression, and a longitudinal slitlike dural defect with smooth lining may develop, causing continuous (Case 1) or intermittent (Case 2) intraspinal CSF leakage. To the best of our knowledge, such dural defects closely resembling the ones observed in idiopathic spinal cord herniation have never been demonstrated on intraoperative endoscopic video in IH patients.

Revision surgery in thoracic disc herniation

PURPOSE

Surgical treatment failures or strategies for the reoperation of residual thoracic disc herniations are sparsely discussed. We investigated factors that led to incomplete disc removal and recommend reoperation strategies.

METHODS

As a referral centre for thoracic disc disease, we reviewed retrospectively the clinical records and imaging studies before and after the treatment of patients who were sent to us for revision surgery for thoracic disc herniation from 2013 to 2018.

RESULTS

A total of 456 patients were treated from 2013 to 2018 at our institution. Twenty-one patients had undergone previously thoracic discectomy at an outside facility and harboured residual, incompletely excised and symptomatic herniated thoracic discs. In 12 patients (57%), the initial symptoms that led to their primary operation were improved after the first surgery, but recurred after a mean of 2.8 years. In seven patients (33%) they remained stable, and in two cases they were worse. All patients were treated via all dorsal approaches. In all 21 cases, the initial excision was incomplete regarding medullar decompression. All of the discs were removed completely in a single revision procedure. After mean follow-up of 24 months (range 12-57 months), clinical neurological improvement was demonstrated in seven patients, while three patients suffered a worsening and 11 patients remained stable.

CONCLUSION

Our data suggest that pure dorsal decompression provides a short relief of the symptoms caused by spinal cord compression. Progressive myelopathy (probably due to mechanical and vascular deficits) and scar formation may cause worsening of symptoms. These slides can be retrieved under Electronic Supplementary Material.

Complications Associated with Surgery for Thoracic Disc Herniation: A Systematic Review and Network Meta-Analysis

BACKGROUND

A systematic review and network meta-analysis (Prospero ID CRD42018106936) were performed.

OBJECTIVE

The selection of the appropriate surgical approach for the management of thoracic disc herniation (TDH) is often challenging because of the frequency and variability of the associated complications. We evaluated the safety of the surgical approaches for TDH by estimating the mortality (Q1) and morbidity (Q2), and frequency of the most common complications (Q3).

METHODS

We searched the medical literature for randomized controlled trials and observational studies reporting on the management of TDH. Postoperative complications were the outcome of interest. The absolute and relative risk estimates, along with the rank probability scores, were estimated for each approach, through a network meta-analysis. The results were read in the light of the quality of the available evidence.

RESULTS

Fifteen studies with a total of 1036 patients fulfilled our eligibility criteria. Three deaths were reported. The overall morbidity was as high as 29%, largely attributed to medical (21%; 95% confidence interval [CI], 10%-38%), surgical site (11%; 95% CI, 5%-22%), cerebrospinal fluid-related (8%; 95% CI, 3%-8%), and neurologic complications (5%; 95% CI, 1%-24%). The anterior and lateral approaches were associated with a higher risk for medical and surgical complications compared with the posterolateral approach.

CONCLUSIONS

Surgery for TDH is associated with minimal mortality but significant morbidity, with large variations among the available approaches. An understanding of the perioperative complications rates is important to develop complication avoidance strategies and to aid accurate patient-to-doctor communication.

A Review of Minimally Invasive Surgical Techniques for the Management of Thoracic Disc Herniations

Thoracic disc herniation (TDH) is a rare, but technically challenging, disorder. Apart from their unfamiliarity with this condition, surgeons are often posed with challenges regarding the diverse methods available to address TDH, the neurological disturbances accompanying the disorder, the prospect of iatrogenic cord damage during surgical procedures, and the complications associated with various surgical approaches. In today's era, when minimally invasive surgery has been incorporated into almost every aspect of managing spine disorders, it is necessary for surgeons to be aware of the various minimally invasive techniques available for the management of these rare and difficult conditions. In this review article, we provide a synopsis of the epidemiology, clinical features, and technical aspects of TDH, starting from level identification to intraoperative neuromonitoring and including important steps and guidance for all the minimally invasive approaches to TDH. We conclude the review by providing insights into the clinical decision-making process and outline the specific aspects of "giant" thoracic discs and indications for fusion in certain conditions. Outcomes of minimally invasive surgery for these conditions are generally favorable. The location of herniation is an important factor for surgical planning.

Surgical treatment of thoracic disc herniation: an overview

BACKGROUND

Surgical treatment of thoracic disc herniation (TDH) is technically demanding due to its proximity to the spinal cord.

METHODS

Literature review.

RESULTS

Symptomatic TDH is a rare condition predominantly localized between T8 and L1. Surgical indications include intractable back or radicular pain, neurological deficits, and myelopathy signs. Giant calcified TDH (> 40% spinal canal occupation) are frequently associated with myelopathy, intradural extension, and post-operative complications. Careful pre-operative planning helps reduce the risk of complications. Pre-operative CT and MRI identify the hernia's location and size, calcifications, and intradural extension. The approach must provide adequate dural sac visualization with minimal manipulation of the cord. Non-anterior approaches are favoured if they provide at least equal exposure than anterior approach owing to higher risk of pulmonary morbidity associated with anterior approach. A transthoracic approach is recommended for central calcified herniated discs. A posterolateral approach is often suitable for non-calcified lateralized TDH. Thoracoscopic approaches are less invasive but have a substantial learning curve. Retropleural mini-thoracotomy is an acceptable alternative. Pre-operative identification of the pathological level is confirmed by intra-operative level check. Intra-operative cord monitoring is preferable but warrant further studies. Magnification and adequate lightening of the surgical field are paramount (microscope, thoracoscopy). Intra-operative CT scan with navigation is becoming increasingly popular since it provides real-time control on the decompression. Indications of fusion consist of pre-operative back pain, Scheuermann's disease, multilevel resection, wide vertebral body resection (> 50%), and herniation at thoracolumbar junction. Neurological deterioration, dural tear, and subarachnoid-pleural fistula are the most severe complications.

CONCLUSION

Further improvements are still warranted in thoracic spine surgery despite the advent of minimally invasive techniques. Intra-operative CT scan will probably enhance the safety of the TDH surgery.