| 저자 |
Jinyoung Park1*, Chae Hwan Lim 1, Myeong Eun Yoo1, Seok Young Chung1, Hyo Jeong Lee1, Dawoon Kim1, Hyo Sik Eom1, Yoon Ghil Park1† |
Introduction
Intraoperative neurophysiological monitoring (IONM) is widely used to avoid neurologic insult during surgical procedures in ossification of posterior longitudinal ligament (OPLL) patients. In this study, we hypothesized that the larger the OPLL size, the greater the significant change of IONM parameters, and the more severe the postoperative neurologic deterioration.
Methods
This retrospective cohort study screened the patients with OPLL who underwent preoperative electrodiagnosis and surgery under IONM in a tertiary hospital between February 2015 and November 2017. Based on the axial view of the spine computed tomography (CT) image taken before surgery, the anteroposterior (AP) diameters of the spinal canal and OPLL were measured at each C2-C7 level. The OPLL AP diameter occupying ratio and the OPLL area occupying ratio were calculated. The number of levels involving OPLL was measured. The preoperative somatosensory evoked potentials (preSEPs) of bilateral median nerves were evaluated. Intraoperative SEPs (ioSEPs) of bilateral median or tibial nerves, and intraoperative motor evoked potentials (ioMEPs) which recorded at bilateral deltoids, abductor pollices brevis, tibialis anterior, and abductor halluces muscles. The alarm criteria for ioSEPs was >10% latency prolongation or > 50% amplitude reduction compared to baseline. For ioMEPs, > 50% amplitude reduction was considered as alarm criteria. The motor scores of the 10 key muscles of International Standards for Neurological Classification of Spinal Cord Injury were evaluated a day before, 48 hours after, and 4 weeks after the operation applying the Medical Research Council scale. Any decline in the motor score compared with the preoperative state was considered postoperative motor deterioration (PMD).
Results
Excluding 24 patients, history of previous spine operation (n=4), OPLL lesion other than cervical spine (n=20), data of total 100 patients were analyzed.
1. OPLL size and preoperative neurologic condition
The mean values of the maximum values of OPLL diameter occupying ratio and the OPLL area occupying ratio, and the number of levels involving OPLL did not differ according to whether preSEP prolongation or preoperative motor deficit (Table 1).
2. OPLL size and IONM parameters
When the patients were classified according to the alarm criteria of ioSEP latency, ioSEP amplitude, and ioMEP amplitude, the mean values of the OPLL diameter occupying ratio and the OPLL area occupying ratio, and the number of levels involving OPLL did not differ (Table 2).
3. OPLL size and PMD
The mean values of the OPLL diameter occupying ratio and the OPLL area occupying ratio, and the number of levels involving OPLL did not differ according to the occurrence of PMD at postoperative 48 hours and 4 weeks (Table 3).
Conclusion
The OPLL size was not statistically related to preoperative motor deficit, preSEPs, ioSEP latency or amplitude, ioMEP amplitude, and PMD.
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