Long-term evaluation of intraoperative neurophysiological monitoring-assisted tethered cord surgery

Classification of and individual treatment strategies for complex tethered cord syndrome

Objective

To study the classification, diagnosis, and treatment strategies of complex tethered cord syndrome (C-TCS) on the basis of the patients' clinical symptoms, imaging findings, and therapeutic schedule.

Methods

The clinical data of 126 patients with C-TCS admitted to our department from January 2015 to December 2020 were retrospectively analyzed. Classification criteria for C-TCS were established by analyzing the causes of C-TCS. Different surgical strategies were adopted for different types of C-TCS. The Kirollos grading, visual analogue scale (VAS), critical muscle strength, and Japanese Orthopaedic Association (JOA) scores were used to evaluate the surgical outcomes and explore individualized diagnosis and treatment strategies for C-TCS.

Results

C-TCS was usually attributable to three or more types of tether-causing factors. The disease mechanisms could be categorized as pathological thickening and lipomatosis of the filum terminal (filum terminal type), arachnoid adhesion (arachnoid type), spina bifida with lipomyelomeningocele/meningocele (cele type), spinal lipoma (lipoma type), spinal deformity (bone type), and diastomyelia malformation (diastomyelia type). Patients with different subtypes showed complex and varied symptoms and required individualized treatment strategies.

Conclusion

Since C-TCS is attributable to different tether-related factors, C-TCS classification can guide individualized surgical treatment strategies to ensure complete release of the tethered cord and reduce surgical complications.

The Association of Physiological and Pharmacological Anesthetic Parameters With Motor-Evoked Potentials: A Multivariable Longitudinal Mixed Model Analysis

BACKGROUND

During spinal surgery, the motor tracts can be monitored using muscle-recorded transcranial electrical stimulation motor-evoked potentials (mTc-MEPs). We aimed to investigate the association of anesthetic and physiological parameters with mTc-MEPs.

METHODS

Intraoperative mTc-MEP amplitudes, mTc-MEP area under the curves (AUC), and anesthetic and physiological measurements were collected retrospectively from the records of 108 consecutive patients undergoing elective spinal surgery. Pharmacological parameters of interest included propofol and opioid concentration, ketamine and noradrenaline infusion rates. Physiological parameters recorded included mean arterial pressure (MAP), bispectral index (BIS), heart rate, hemoglobin O2 saturation, temperature, and Etco2. A forward selection procedure was performed using multivariable mixed model analysis.

RESULTS

Data from 75 (69.4%) patients were included. MAP and BIS were significantly associated with mTc-MEP amplitude (P < .001). mTc-MEP amplitudes increased by 6.6% (95% confidence interval [CI], 2.7%-10.4%) per 10 mm Hg increase in MAP and by 2.79% (CI, 2.26%-3.32%) for every unit increase in BIS. MAP (P < .001), BIS (P < .001), heart rate (P = .01), and temperature (P = .02) were significantly associated with mTc-MEP AUC. The AUC increased by 7.5% (CI, 3.3%-11.7%) per 10 mm Hg increase of MAP, by 2.98% (CI, 2.41%-3.54%) per unit increase in BIS, and by 0.68% (CI, 0.13%-1.23%) per beat per minute increase in heart rate. mTc-MEP AUC decreased by 21.4% (CI, -38.11% to -3.98%) per degree increase in temperature.

CONCLUSIONS

MAP, BIS, heart rate, and temperature were significantly associated with mTc-MEP amplitude and/or AUC. Maintenance of BIS and MAP at the high normal values may attenuate anesthetic effects on mTc-MEPs.

Surgery for spina bifida occulta: spinal lipoma and tethered spinal cord

The technical evolution of the surgery for spina bifida occulta (SBO) over the course of a half-century was reviewed with special foci placed on the spinal lipoma and tethered spinal cord. Looking back through history, SBO had been included in spina bifida (SB). Since the first surgery for spinal lipoma in the mid-nineteenth century, SBO has come to be recognized as an independent pathology in the early twentieth century. A half-century ago, the only option available for SB diagnosis was the plain X-ray, and pioneers of the time persevered in the field of surgery. The classification of spinal lipoma was first described in the early 1970s, and the concept of tethered spinal cord (TSC) was proposed in 1976. Surgical management of spinal lipoma with partial resection was the most widely practiced approach and was indicated only for symptomatic patients. After understanding TSC and tethered cord syndrome (TCS), more aggressive approaches became preferred. A PubMed search suggested that there was a dramatic increase of publications on the topic beginning around 1980. There have been immense academic achievements and technical evolutions since then. From the authors' viewpoint, landmark achievements in this field are listed as follows: (1) establishment of the concept of TSC and the understanding of TCS; (2) unraveling the process of secondary and junctional neurulation; (3) introduction of modern intraoperative neurophysiological mapping and monitoring (IONM) for surgery of spinal lipomas, especially the introduction of bulbocavernosus reflex (BCR) monitoring; (4) introduction of radical resection as a surgical technique; and (5) proposal of a new classification system of spinal lipomas based on embryonic stage. Understanding the embryonic background seems critical because different embryonic stages bring different clinical features and of course different spinal lipomas. Surgical indications and selection of surgical technique should be judged based on the background embryonic stage of the spinal lipoma. As time flows forward, technology continues to advance. Further accumulation of clinical experience and research will open the new horizon in the management of spinal lipomas and other SBO in the next half-century.

[Classification and microsurgical treatment of primary tethered cord syndrome in adults]

OBJECTIVE

To summarize the clinical manifestation, classification, and experience of surgical treatment of primary tethered cord syndrome (TCS) in adults.

METHODS

The authors retrospectively analyzed a series of 171 adult patients with primary TCS who were surgically treated under microscope from March 2007 to October 2019. There were 61 males and 110 females whose ages were 18-65 years, with an average age of (39.02±11.81) years. Clinically, the patients presented with various neurological symptoms and signs including lower back and legs pain, reflex changes, sensory disturbances, muscle weakness, and sphincter problems. They were divided into 5 types by clinical manifestations and neuro-imaging features: (1) filum terminale traction in 69 cases, (2) split cord malformation in 21 cases, (3) myelomeningocele in 20 cases, (4) lipomyelomeningocele in 36 cases, and (5) dermal sinus traction in 25 cases. All the patients underwent microsurgery to untether the spinal cord. The patients kept prone position 7 days postoperatively. The Kirollos grading was used to evaluate the outcome of intraoperative untethering. The visual analogue scale (VAS) was used to evaluate the pain, the score of critical muscle strength was used to evaluate the lower extremity motor function, and the Japanese Orthopaedic Association (JOA) sphincter function score was used to evaluate the bladder function.

RESULTS

All of the 171 patients were treated with microsurgery to release the adhesion and cut off the filum terminalis. 61 cases of them received resection of the lesions according to the etiology. All the tethered spinal cord reached Kirollos grade Ⅰ untethering and the dural sac was reconstructed. Other than 5 patients had cerebrospinal fluid leakage and incision laceration and underwent re-suture, there was no surgical complication. The local pain was relieved, the lower limbs weakness or bowel and bladder dysfunction gradually recovered postoperatively. The period of follow-up ranged from 6 months to 12.5 years with an average of (5.62±2.31) years. The neurological function was improved in 153 cases and stable in 18 cases. There was no recurrence of tethered cord be found during the follow-up period.

CONCLUSION

The primary TCS in adulthood could be classified into 5 types by clinical manifestations and neuro-imaging features and surgical treatment should be undertaken in regard to the classifications including dissection and resection of the lesion detethering the spinal cord and reconstruction of the dura sac under microscope. The outcome of surgical treatment is satisfactory.

Early- and long-term surgical outcomes in 109 children with lipomyelomeningocele

AIM

To determine the functional outcomes and risk factors for outcomes following surgery for lipomyelomeningocele (LMMC).

METHODS

Data from 109 children with LMMC who underwent surgery from January 2008 to December 2017 were retrospectively studied to evaluate functional outcomes and possible risk factors for early- (at discharge from hospital or within 1 month of surgery) and long-term outcomes after surgery.

RESULTS

There were 53 boys and 56 girls with median age of 36 months (IQR 12-90 months; range, 4 months to 18 years) at surgery. At presentation, neurological function was normal (asymptomatic group) in 28 (25.7%) children while there was neurological dysfunction (symptomatic group) in 81 (74.3%). Near total or radical excision of lipoma was done in 71 (65.1%) children. Six (5.8%) children had deterioration of neurological function in the post-operative period with recovery of function in three of them. There were no statistically significant risk factors for early outcomes. At a mean follow-up of 62.5 months (IQR 35-82 months; range, 12-146 months), 21 (27.6%) of the 76 symptomatic group children (including 59.3% with incomplete bladder dysfunction) showed improvement, 52 (68.4%) remained the same, while 3 (4%) deteriorated. In 31 children (symptomatic group) who developed symptoms after 1 year of age, early surgery after development of symptoms was associated with better chances of recovery (p = 0.0008). In the asymptomatic group, 23 (88.5%) had normal neurological function at mean follow-up of 57.5 months (IQR 30-77 months; range, 12-141 months) and 3 (11.5%) had neurological deterioration. The mean time to late deterioration (re-tethering) from surgery was 51.3 months (IQR 24-75 months; range, 24-84 months). Presence of syrinx on initial MRI (p = 0.008) and partial resection of the lipoma (p = 0.02) were independent risk factors for delayed deterioration.

CONCLUSION

Radical resection of LMMC probably helps in preserving neurological function in > 90% of children at long-term follow-up. Fifty-five percent of children > 2 years of age with incomplete bladder dysfunction regained normal function following surgery. In children who develop symptoms after birth, early surgical intervention can reverse the neurological deficits.

The influence of depth of anesthesia and blood pressure on muscle recorded motor evoked potentials in spinal surgery. A prospective observational study protocol

For high-risk spinal surgeries, intraoperative neurophysiological monitoring (IONM) is used to detect and prevent intraoperative neurological injury. The motor tracts are monitored by recording and analyzing muscle transcranial electrical stimulation motor evoked potentials (mTc-MEPs). A mTc-MEP amplitude decrease of 50–80% is the most common warning criterion for possible neurological injury. However, these warning criteria often result in false positive warnings. False positives may be caused by inadequate depth of anesthesia and blood pressure on mTc-MEP amplitudes. The aim of this paper is to validate the study protocol in which the goal is to investigate the effects of depth of anesthesia (part 1) and blood pressure (part 2) on mTc-MEPs. Per part, 25 patients will be included. In order to investigate the effects of depth of anesthesia, a processed electroencephalogram (pEEG) monitor will be used. At pEEG values of 30, 40 and 50, mTc-MEP measurements will be performed. To examine the effect of blood pressure on mTc-MEPs the mean arterial pressure will be elevated from 60 to 100 mmHg during which mTc-MEP measurements will be performed. We hypothesize that by understanding the effects of depth of anesthesia and blood pressure on mTc-MEPs, the mTc-MEP monitoring can be interpreted more reliably. This may contribute to fewer false positive warnings. By performing this study after induction and prior to incision, this protocol provides a unique opportunity to study the effects of depths of anesthesia and blood pressure on mTc-MEPs alone with as little confounders as possible.

Trial registration number NL7772.

The incidence and effect of tethered cord release for tethered cord syndrome in patients with myelomeningocele: a population-based study

OBJECTIVE

The goal of this study was to establish an incidence and assess the effect of tethered cord release for tethered cord syndrome in patients with myelomeningocele.

METHODS

The study population was based on the Western Denmark Myelomeningocele Database, which contains all patients born with myelomeningocele in western Denmark since 1970. The study population was cross-referenced in 2015 with a database for surgical procedures containing all surgical procedures performed in the central Denmark region since 1996. Patients alive between 1996 and 2015 were identified. Incidences was calculated and presented for year of age. File reviews were conducted for all patients who underwent the procedure. Follow-up was divided into short-term and long-term follow-up.

RESULTS

One hundred sixty-six patients were alive during various time periods between 1996 and 2015. Of these, 45 patients underwent the procedure. Seven underwent reoperation. The median age for the procedure was 12 years and the highest incidence was found at 15 years of age. Incidence was bimodal with highest incidence in children and adolescents. The most common indications were progressive spine deformity (40%), deteriorating ambulation (38%), and deteriorating neurogenic bladder and/or bowel dysfunction (32%). The mean short-term follow-up was 4.7 months and the mean long-term follow-up was 72.6 months. Postoperatively, the majority had improved (27%) or stabilized (27%) at short-term follow-up. At long-term follow-up, most patients were stable (27%) or had deteriorated (24%). For both follow-up terms there was a loss of approximately one-third of all patients. Complications occurred in 17% of the procedures.

CONCLUSIONS

In this population-based study, tethered cord release has the highest incidence in children and adolescents. The beneficial effect of the procedure seems to be short term. Due to the uncertainty of a long-term effect of the procedure in patients with myelomeningocele and the registered complications, the authors suggest that this surgical indication should be reserved for well-selected patients.

Clinical Outcomes of Primary and Revision Untethering Surgery in Patients with Tethered Cord Syndrome and Spinal Bifida

BACKGROUND

Tethered cord syndrome (TCS) is an increasingly recognized clinical condition, with untethering surgery considered the classically effective treatment. Yet, as evidence has aggregated, the surgical outcomes of untethering remain controversial. This study aimed to systematically evaluate the clinical outcomes in patients who underwent primary or revision untethering.

METHODS

This retrospective study was conducted at the Department of Spine Surgery of Changzheng Hospital between January and December 2016. Patients with TCS who underwent untethering surgery were recruited for the study. Information collected included demographic data, main clinical manifestations, and outcomes after untethering surgery.

RESULTS

A total of 112 patients (60 males and 52 females) were included in this study, with mean follow-up of 13.7 years. The surgical outcomes of the primary untethering varied among symptoms, with remission rates of 30.0% for pain, 24.4% for paresthesia, 18.6% for motor deficit, 12.6% for bladder dysfunction, and 21.2% for bowel dysfunction. Moreover, 23.3%-40.2% of patients suffered deterioration after surgery during the follow-up period. Twenty-eight patients underwent revision untethering surgery. In these patients, the remission rate decreased by 5.6%-16.7% compared with the primary operation. Moreover, most patients (58.8%-70.6%) experienced no benefits after revision surgery.

CONCLUSIONS

With a possible high risk of recurrence, further exploration of the indications and timing of the untethering surgery is needed. Conservative treatment and omnidirectional care might be a better choice for patients with retethering with recurrent symptoms.