1Department of Neurological Surgery, University of Washington, Seattle.
2Department of Rehabilitation Medicine, University of Washington, Seattle; and.
Neurosurg Focus. 2023 Mar;54(3):E9. doi: 10.3171/2022.12.FOCUS22632.
Surgical treatment for symptomatic Chiari I malformation involves surgical decompression of the craniovertebral junction. Given the proximity of critical brainstem structures, intraoperative neuromonitoring (IONM) is employed for safe decompression in some institutions. However, IONM adds time and cost to the operation, and the benefit to the patient has not been defined. Given the diversity in surgical practices, there is no evidence-based standard of care regarding when to use IONM and which modalities are most helpful. The purpose of this study was to review a single-surgeon experience with IONM in order to determine the sensitivity, specificity, and predictive values of various IONM modalities routinely used in pediatric Chiari I decompression; to examine the associations between patient, clinical, and radiographic characteristics and IONM alerts; and to obtain data regarding the usefulness of these modalities during the surgical process to improve patient outcomes.
A retrospective review was performed for 300 consecutive pediatric patients who underwent suboccipital craniectomy and C1 laminectomy for Chiari decompression performed by a single surgeon over a 15-year period. Clinical, radiographic, and IONM data were collected. Radiographic measurements of the skull base morphological abnormalities, including clival angle, Chamberlain's line, and Grabb-Oakes line, were compared between patients with and without true IONM signal changes.
A total of 291 cases were included, with an age range of 6 months to 19 years. Among 291 cases, somatosensory evoked potentials (SSEPs) were monitored in 291, motor evoked potentials (MEPs) in 209, cranial nerve spontaneous electromyography (sEMG) in 290, and brainstem auditory evoked potentials (BAEPs) in 110. Sensitivity, specificity, positive predictive value, and negative predictive value, respectively, were as follows: 1.00, 1.00, 1.00, and 1.00 for SSEPs; 1.00, 0.99, 0.67, and 1.00 for MEPs; 0.00, 0.88, 0.00, and 1.00 for sEMG; and not appliable, 1.00, not applicable, and 1.00 for BAEPs. Six patients had true IONM signal changes. These patients had radiographic evidence of more severe concomitant craniocervical instability and basilar invagination, with steeper clival angles (124° vs 146°, p = 0.02) and larger Grabb-Oakes lines (10.1 mm vs 6.7 mm, p = 0.02), when compared with the patients without any true IONM changes.
Intraoperative neuromonitoring may be best utilized for patients who show radiographic features of abnormal skull base morphology, defined as a clival angle < 135° or Grabb-Oakes line > 9 mm. When IONM is employed, SSEP and MEP monitoring are the most useful modalities.
针对有症状的 Chiari I 畸形的手术治疗包括颅颈交界区的减压。由于靠近关键的脑干结构，一些机构在术中使用术中神经监测（IONM）来进行安全减压。然而，IONM 增加了手术的时间和成本，并且尚未确定对患者的益处。鉴于手术实践的多样性，关于何时使用 IONM 以及哪种方式最有帮助，尚无循证护理标准。本研究的目的是回顾一位外科医生在 IONM 方面的经验，以确定在儿科 Chiari I 减压术中常规使用的各种 IONM 方式的敏感性、特异性和预测值；检查患者、临床和影像学特征与 IONM 警报之间的关联；并获得有关这些方式在手术过程中改善患者结局的有用数据。
对 300 例连续接受同种术式治疗的儿童患者进行回顾性研究，这些患者均由同一位外科医生进行了枕下颅骨切除术和 C1 椎板切除术治疗 Chiari 减压，该研究进行了 15 年。收集了临床、影像学和 IONM 数据。比较了有和无真正 IONM 信号改变的患者的颅底形态异常的影像学测量值，包括斜坡角、Chamberlain 线和 Grabb-Oakes 线。
共纳入 291 例病例，年龄范围为 6 个月至 19 岁。在 291 例患者中，监测体感诱发电位（SSEP）291 例，运动诱发电位（MEP）209 例，颅神经自发性肌电图（sEMG）290 例，脑干听觉诱发电位（BAEP）110 例。SSEP 的敏感性、特异性、阳性预测值和阴性预测值分别为 1.00、1.00、1.00 和 1.00；MEP 的敏感性、特异性、阳性预测值和阴性预测值分别为 1.00、0.99、0.67 和 1.00；sEMG 的敏感性、特异性、阳性预测值和阴性预测值分别为 0.00、0.88、0.00 和 1.00；BAEP 的敏感性、特异性、阳性预测值和阴性预测值分别为不适用、1.00、不适用和 1.00。6 例患者出现真正的 IONM 信号改变。这些患者的影像学证据显示存在更严重的并发颅颈交界区不稳定和颅底凹陷，其斜坡角更陡峭（124°比 146°，p = 0.02），Grabb-Oakes 线更大（10.1 毫米比 6.7 毫米，p = 0.02），与无任何真正 IONM 改变的患者相比。
术中神经监测可能最适用于具有异常颅底形态影像学特征的患者，定义为斜坡角<135°或 Grabb-Oakes 线>9mm。当使用 IONM 时，SSEP 和 MEP 监测是最有用的方式。
