Neurophysiological Monitoring in Radiofrequency Ablation of Spinal Osteoid Osteoma With a Progressive Time and Temperature Protocol in Children.

STUDY DESIGN: Retrospective. Level IV Evidence. OBJECTIVE: To assess the utility of intraoperative neurophysiological monitoring (IONM) to detect and eventually prevent impending neurovascular damage during computed tomography (CT)-guided radiofrequency ablation (RFA) of spinal osteoid osteoma (OO) in children. SUMMARY AND BACKGROUND DATA: To our knowledge, this is the first case series of spinal OO in pediatric patients treated at a single center employing IONM during RFA. METHODS: This is a retrospective study of seven consecutive patients (3 girls and 4 boys, mean age: 9 years 4 months) with imaging and clinical signs compatible with spinal OO who underwent CT-guided RFA, under general anesthesia, and IONM in a single center between 2011 and 2015. Before the RFA procedure, a CT-guided percutaneous biopsy of the nidus was performed in the same setting. RFA was divided into four cycles of increasing time and temperature and performed under IONM in every patient. RESULTS: Two patients had lesions located in the thoracic spine and five patients had lumbar involvement. The RFA technical and clinical success was 85.7%. Six patients presented with reversible neurophysiological changes either during biopsy needle positioning or RFA cycles. In the remaining case, as IONM changes did not improve after several minutes of neuroprotective hypertension, the procedure was interrupted. Neither neurologic nor vascular complications were observed after RFA treatment. In only one biopsy sample, OO was confirmed by histopathologic studies. CONCLUSION: CT-guided RFA is an accepted minimally invasive technique for the treatment of spinal OO in children. IONM may be a helpful tool that requires minimal additional time and provides feedback on the state of the spinal cord and nerves at risk during the procedure. We promote the use of IONM during these procedures to detect and possibly prevent impending neurologic damage. LEVEL OF EVIDENCE: Level IV.

A Multiparametric Alarm Criterion for Motor Evoked Potential Monitoring During Spine Deformity Surgery.

PURPOSE: This is a pilot study to compare changes in the amplitude, area below the curve, number of phases, duration, and latency of the intraoperative transcranial motor evoked potentials (TcMEP) for early detection of impending spinal cord injury. An empirical ratio calculated by a combination of the above-mentioned parameters was also assessed. METHODS: Intraoperative TcMEP recordings from five patients presenting with neuromuscular kyphoscoliosis, idiopathic scoliosis, achondroplasia and lumbar kyphosis, congenital kyphosis, and achondroplasia with cervical instability were reviewed. Anesthesia was sustained with propofol or sevoflurane plus remifentanil, no muscle relaxants were used after intubation. The TcMEPs to multipulse electrical stimulation were recorded from upper-limb and lower-limb muscles. To be worthy of analyses, changes should include TcMEP disappearance or amplitude decrease >-65% during surgical/force maneuverings. RESULTS: Transient TcMEP changes related to surgical/force maneuvering were observed in all five patients consisting of a decrease in the empirical ratio value (>-95%), followed in magnitude by a drop in the area below the curve, amplitude (>-80%), duration, and number of phases, whereas latency increased. Changes returned to baseline when maneuverings were reverted. No hemodynamic/anesthetic factors were present during these events. After surgeries, no new neurological deficits were detected. CONCLUSIONS: An empirical ratio accounting for all TcMEP parameters seems to drop more than the amplitude during an intraoperative event. As few cases were analyzed, further studies in larger series of patients will be necessary to assess empirical ratio sensitivity/specificity and to determine whether this may be a useful monitoring warning criterion not leading to unnecessary interference with surgical treatment.