Intraoperative neurophysiological monitoring in paediatric Chiari surgery-help or hindrance?

Intraoperative neuromonitoring is not a useful adjunct for Chiari malformation decompressive surgery: a cost-benefit and legal analysis

OBJECTIVES

Posterior fossa decompression is currently an operative treatment of choice for Chiari Malformation I (CM1). However, there is controversy surrounding the possible benefits of employing intraoperative neuromonitoring (INM) for this type of procedure. In addition to presenting our single-center experience on the use of INM, we analyze the cost associated with INM in Chiari Malformation (CM) decompression surgery using the Healthcare Cost and Utilization Project (HCUP) database and discuss the legal implications of somatosensory evoked potentials (SSEP) monitoring during decompression for CM1.

METHODS

We conducted a retrospective review of all patients undergoing CM1 decompression with SSEP neuromonitoring from 2011 to 2018. We collected patient characteristics, hospital charges, and surgical cost data from the HCUP database for patients undergoing CM decompression. Finally, we performed a review within the Thompson Reuters Westlaw Edge database for reported litigation involving INM for CM decompression.

RESULTS

None of the 110 patients submitted to surgery for CM1 at our institution had any significant SSEP changes intraoperatively or developed post-operative neurological deterioration. There were higher mean total hospital charges and surgical costs associated with INM ($31,272) for patients who received INM compared to patients who did not receive INM ($24,112). A careful review of the Westlaw database with multiple-word search strategies revealed no reported medical malpractice claims regarding the absence of SSEP neuromonitoring in a CM decompression procedure.

CONCLUSION

Using data collected at our institution and the HCUP national database, we showed that intraoperative neuromonitoring did not affect surgical planning and decision-making or post operative care, while adding unnecessary costs to CM decompression procedures. The absence of reported malpractice claims targeting the lack of neuromonitoring in CM cases suggests that SSEP neuromonitoring during CM may be unnecessary. We propose that neuromonitoring should not be used for routine CM decompression.

Intraoperative neuromonitoring in Chiari I malformation surgery: a systematic review and meta-analysis

Chiari Malformation Type I (CMI) is a prevalent neurosurgical condition characterized by the descent of cerebellar tonsils below the foramen magnum. Surgery, aimed at reducing symptomatology and syrinx size, presents risks, making intraoperative neuromonitoring (IONM) a potentially vital tool. Despite its widespread use in cervical spine surgery, the utility of IONM in CMI surgery remains controversial, with concerns over increased operative time, cost, restricted anesthetic techniques and tongue lacerations. This systematic review and meta-analysis followed the Cochrane Group standards and PRISMA framework. It encompassed an extensive search through PubMed, Embase, and Web of Science up to December 2023, focusing on clinical and surgical outcomes of IONM in CMI surgery. Primary outcomes included the use of various IONM techniques, complication rates, clinical improvement, reoperation, and mortality. The review, registered at PROSPERO (CRD42024498996), included both prospective and retrospective studies, with rigorous selection and data extraction processes. Statistical analysis was conducted using R software. The review included 16 studies, comprising 1358 patients. It revealed that IONM techniques predominantly involved somatosensory evoked potentials (SSEPs), followed by motor evoked potentials (MEPs) and Brainstem auditory evoked potentials (BAEPs). The estimated risk of complications with IONM was 6% (95% CI: 2-11%; I2 = 89%), lower than previously reported rates without IONM. Notably, the clinical improvement rate post-surgery was high at 99% (95% CI: 98-100%; I2 = 56%). The analysis also showed lower reoperation rates in surgeries with IONM compared to those without. Interestingly, no mortality was observed in the included studies. This systematic review and meta-analysis indicate that intraoperative neuromonitoring in Chiari I malformation surgery is associated with favorable clinical outcomes, including lower complication and reoperation rates, and high rates of clinical improvement.

In-House Intraoperative Monitoring in Neurosurgery in England - Benefits and Challenges

BACKGROUND

Intraoperative neurophysiological monitoring (IOM) is a valuable adjunct for neurosurgical operative techniques, and has been shown to improve clinical outcomes in cranial and spinal surgery. It is not necessarily provided by NHS hospitals so may be outsourced to private companies, which are expensive and at cost to the NHS trusts. We discuss the benefits and challenges of developing an in-house service.

METHODS

We surveyed NHS neurosurgical departments across England regarding their expenditure on IOM over the period January 2018 - December 2022 on cranial neurosurgery and spinal surgery. Out of 24 units, all responded to our Freedom of Information requests and 21 provided data. The standard NHS England salary of NHS staff who would normally be involved in IOM, including physiologists and doctors, was also compiled for comparison.

RESULTS

The total spend on outsourced IOM, across the units who responded, was over £8 million in total for the four years. The annual total increased, between 2018 and 2022, from £1.1 to £3.5 million. The highest single unit yearly spend was £568,462. This is in addition to salaries for staff in neurophysiology departments. The mean NHS salaries for staff is also presented.

CONCLUSION

IOM is valuable in surgical decision-making, planning, and technique, having been shown to lead to fewer patient complications and shorter length of stay. Current demand for IOM outstrips the internal NHS provision in many trusts across England, leading to outsourcing to private companies. This is at significant cost to the NHS. Although there is a learning curve, there are many benefits to in-house provision, such as stable working relationships, consistent methods, training of the future IOM workforce, and reduced long-term costs, which planned expansion of NHS services may provide.

The Role of Neurophysiology in Managing Patients with Chiari Malformations

Chiari malformation type 1 (CM1) includes various congenital anomalies that share ectopia of the cerebellar tonsils lower than the foramen magnum, in some cases associated with syringomyelia or hydrocephalus. CM1 can cause dysfunction of the brainstem, spinal cord, and cranial nerves. This functional alteration of the nervous system can be detected by various modalities of neurophysiological tests, such as brainstem auditory evoked potentials, somatosensory evoked potentials, motor evoked potentials, electromyography and nerve conduction studies of the cranial nerves and spinal roots, as well as brainstem reflexes. The main goal of this study is to review the findings of multimodal neurophysiological examinations in published studies of patients with CM1 and their indication in the diagnosis, treatment, and follow-up of these patients, as well as their utility in intraoperative monitoring.

Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines for Patients With Chiari Malformation: Surgical Interventions

BACKGROUND

Chiari malformation type I (CIM) diagnoses have increased in recent years. Controversy regarding the best operative management prompted a review of the literature to offer guidance on surgical interventions.

OBJECTIVE

To assess the literature to determine (1) whether posterior fossa decompression or posterior fossa decompression with duraplasty is more effective in preoperative symptom resolution; (2) whether there is benefit from cerebellar tonsillar resection/reduction; (3) the role of intraoperative neuromonitoring; (4) in patients with a syrinx, how long should a syrinx be observed for improvement before additional surgery is performed; and 5) what is the optimal duration of follow-up care after preoperative symptom resolution.

METHODS

A systematic review was performed using the National Library of Medicine/PubMed and Embase databases for studies on CIM in children and adults. The most appropriate surgical interventions, the use of neuromonitoring, and clinical improvement during follow-up were reviewed for studies published between 1946 and January 23, 2021.

RESULTS

A total of 80 studies met inclusion criteria. Posterior fossa decompression with or without duraplasty or cerebellar tonsil reduction all appeared to show some benefit for symptom relief and syrinx reduction. There was insufficient evidence to determine whether duraplasty or cerebellar tonsil reduction was needed for specific patient groups. There was no strong correlation between symptom relief and syringomyelia resolution. Many surgeons follow patients for 6-12 months before considering reoperation for persistent syringomyelia. No benefit or harm was seen with the use of neuromonitoring.

CONCLUSION

This evidence-based clinical guidelines for the treatment of CIM provide 1 Class II and 4 Class III recommendations. In patients with CIM with or without syringomyelia, treatment options include bone decompression with or without duraplasty or cerebellar tonsil reduction. Improved syrinx resolution may potentially be seen with dural patch grafting. Symptom resolution and syrinx resolution did not correlate directly. Reoperation for a persistent syrinx was potentially beneficial if the syrinx had not improved 6 to 12 months after the initial operation. The full guidelines can be seen online at https://www.cns.org/guidelines/browse-guidelines-detail/3-surgical-interventions .

Use of Intraoperative Neuromonitoring in Surgical Treatment of Acute Presentation of Chiari I Malformation: A Case Report

Intraoperative neuromonitoring (IONM) has been used in neurosurgical procedures to assess patient safety and minimize risk of neurological deficit. However, its use in decompressive surgeries of Chiari malformation type I (CM-I) remains a topic of debate. Here we present the case of a 5-year-old girl who presented with acute right lower extremity monoplegia after accidental self-induced hyperflexion of the neck while playing. Imaging revealed 15 mm of tonsillar ectopia with cervical and upper thoracic spinal cord edema. She was taken to surgery for a suboccipital decompression with expansile duraplasty. IONM demonstrated improvement in motor evoked potentials during the decompression. Postoperatively, she had full recovery of strength and mobility. This is a case of acute weakness after mild trauma in the setting of previously asymptomatic CM-I that showed close correlation with IONM, clinical findings, and imaging. IONM during decompressive surgery for CM-I may be useful in patients who present acutely with cervical cord edema.

Chiari Type 1 Malformation and Syringomyelia in Children: Classification and Treatment Options

Chiari type 1 malformation (CIM) is defined as tonsillar ectopia of >5 mm, while syringomyelia (SM) is defined as a cerebrospinal fluid (CSF)-filled cavity larger than 3 mm dissecting the spinal cord. Over the last decades, our understanding of these pathologies has grown; however, many controversies still exist almost in every aspect of CIM and SM, including etiology, indication for treatment, timing of treatment, surgical technique, follow-up regime, and outcome. This chapter provides a comprehensive overview on different aspects of CIM and SM and on the still existing controversies, based on the evidence presently available. Future directions for clinical research concerning CIM and SM treatment and outcome are elaborated and discussed as well.

Monitoring surgery around the cranial nerves

Intraoperative neurophysiologic monitoring (IONM) of cranial nerve (CN) function is an essential component in multimodality monitoring of surgical procedures where CNs are at risk for injury. In most cases, IONM consists of localizing and mapping CNs and their pathways, and monitoring of CN motor function during surgery. However, CN VIII, which has no motor function, and is at risk for injury in many surgical procedures, can be easily and accurately monitored using brainstem auditory evoked potentials. For motor CNs, the literature is clear that function can be safely and adequately performed using basic electromyographic (EMG) techniques, such as recording of continuous EMG activity and electrically evoked compound muscle actions potentials. Newer techniques, such as corticobulbar motor evoked potentials and reflex studies, show good potential for a greater degree of functional assessment but require further study to determine their clinical utility. EMG remains the basic clinical neurophysiologic technique with the greatest clinical research supporting its utility in IONM of motor CN function and should be used as part of a comprehensive multimodality IONM protocol. Understanding the physiologic basis of EMG and the changes associated with altered motor function will allow the practitioner to alter surgical course to prevent injury and improve patient safety.

Utility of intraoperative neuromonitoring for decompression of Chiari type I malformation in 93 adult patients

OBJECTIVE

There is currently a lack of consensus on the utility of intraoperative neuromonitoring (IONM) for decompression of Chiari type I malformation (CM-I). Commonly used monitoring modalities include somatosensory evoked potentials (SSEPs), motor evoked potentials (MEPs), and brainstem auditory evoked potentials (BAEPs). The purpose of this study was to evaluate the utility of IONM in preventing neurological injury for CM-I decompression.

METHODS

The authors conducted a retrospective study of a population of adult patients (ages 17-76 years) diagnosed with CM-I between 2013 and 2021. IONM modalities included SSEPs, MEPs, and/or BAEPs. Prepositioning baseline signals and operative alerts of significant signal attenuation were recorded.

RESULTS

Ninety-three patients (average age 38.4 ± 14.6 years) underwent a suboccipital craniectomy for CM-I decompression. Eighty-two (88.2%) of 93 patients underwent C1 laminectomy, 8 (8.6%) underwent C1 and C2 laminectomy, and 4 (4.3%) underwent suboccipital craniectomy with concomitant cervical decompression and fusion in the setting of degenerative cervical spondylosis. Radiographically, the average cerebellar tonsillar ectopia/descent was 1.1 ± 0.5 cm and 53 (57.0%) of 93 patients presented with a syrinx. The average number of vertebral levels traversed by the syrinx was 5.3 ± 3.5, and the average maximum width of the syrinx was 5.8 ± 3.3 mm. There was one instance (1/93, 1.1%) of an MEP alert, which resolved spontaneously after 10 minutes in a patient who had concomitant stenosis due to pannus formation at C1-2. No patient developed a permanent neurological complication.

CONCLUSIONS

There were no permanent complications related to intraoperative neurological injury. Transient fluctuations in IONM signals can be detected without clinical significance. The authors suggest that CM-I suboccipital decompression surgery may be performed safely without IONM. The use of IONM in patients with additional occipitocervical pathology should be left as an option to the performing surgeon on a case-by-case basis.