Feasibility and diagnostic accuracy of intra-operative monitoring of motor evoked potentials in children <2 years of age undergoing tethered cord surgery: results in 100 children.

OBJECTIVE: This study documents the monitorability using different anesthesia regimes and accuracy of muscle motor evoked potentials (mMEPs) in children ≤2 years of age undergoing tethered cord surgery (TCS). METHODS: Intraoperative mMEP monitoring was attempted in 100 consecutive children, ≤2 years of age, undergoing TCS. MEP monitoring was done under 4 different anesthetic regimes: (Total intravenous anesthesia (TIVA); balanced anesthesia with sevoflurane and ketamine; balanced anesthesia with isoflurane and ketamine; and balanced anesthesia with sevoflurane). Factors analyzed for their effect on monitorability were: age, neurological deficits, type of anesthesia, and the number of pulses used for stimulation. RESULTS: Baseline mMEPs were obtained in 87% children. Monitorability of mMEPs was similar in children ≤1 year and 1-2 years of age (85.7% and 87.5%). In multivariate analysis, anesthesia regime was the only significant factor predicting presence of baseline mMEPs. Children undergoing TIVA (p=0.02) or balanced anesthesia with a combination of propofol, sevoflurane, and ketamine (p=0.05) were most likely to have baseline mMEPs. mMEPs had a sensitivity of 97.4%, specificity of 96.4%, negative predictive value of 98.2% and accuracy of 96.8%. CONCLUSIONS: Baseline mMEPs were obtained in >85% of children ≤2 years of age including those who had motor deficits. TIVA and balanced anesthesia with sevoflurane and ketamine are ideal for mMEP monitoring. mMEPs have a high accuracy although, false positive and false negative results can occasionally be experienced.

The utility of facial nerve amplitude and latency ratios in predicting postoperative facial nerve function after vestibular schwannoma surgery.

BACKGROUND: Despite advances in vestibular schwannoma (VS) surgery and intraoperative electrophysiological monitoring, immediate and delayed facial nerve outcomes are difficult to accurately predict consistently. OBJECTIVE: To determine the utility of proximal to distal facial nerve amplitude and latency ratios in predicting the long-term postoperative facial nerve function in patients undergoing excision of VS. MATERIALS AND METHODS: One hundred consecutive patients undergoing surgery for VS with intraoperative facial nerve monitoring were included. Clinical, radiological, electrophysiological, and postoperative outcome data were prospectively entered into a database. Other parameters such as brainstem distance, size of the porus acousticus, and facial nerve length were also analyzed. RESULTS: Of the 100 patients, 53 were women. The mean age was 42.5 ± 14.1 years (range, 14-71 years) and the average tumor size was 4.1 ± 0.8 cm (range, 2.4-6.5 cm). Total excision was done in 89% of patients. Intraoperatively, the facial nerve was anatomically preserved in 86 patients, but electrophysiological responses were obtained from the root entry zone (REZ) in only 77 patients at the end of surgery, 75% of which had good facial function at long-term follow-up. In nine patients where no responses were obtained but the facial nerve was anatomically intact, 50% had good facial function at long-term follow-up. Proximal and distal amplitude and latency ratios, size or consistency of the tumor, brainstem distance, size of the porus acousticus, and length of the facial nerve were not useful in predicting long-term functional outcome. CONCLUSIONS: While a positive response to facial nerve stimulation at the end of VS surgery is a good predictor of long-term postoperative function, the absence of responses in an anatomically intact nerve does not preclude good function in the long term. Proximal to-distal amplitude and latency ratios did not correlate with the final facial function.

Time-Dependent Bidirectional Neuroprotection by Adenosine 2A Receptor in Experimental Traumatic Brain Injury.

BACKGROUND: Traumatic brain injury (TBI) results in both focal and diffuse brain pathological features that become severely exacerbated after the initial injury. Owing to this disease complexity, no effective therapeutic measure has yet been devised aimed directly at these pathological processes. We developed a clinically relevant model of TBI and tested the bidirectional neuroprotective role of adenosine 2A receptors (A2ARs) at different times. METHODS: Wistar rats were divided into 4 treatment groups (sham, TBI, A2AR agonist [CGS-21680], and A2AR antagonist [SCH-58261]) and 4 post-TBI intervals (15 minutes and 1, 12, and 24 hours). A2AR agonist and antagonist effects were tested by the neurological functional score (NFS) and levels of cyclic adenosine monophosphate, interleukin-1ß, oxidative stress antioxidant markers, and caspase-3. RESULTS: The A2AR agonist-treated group showed significant NFS improvement at 15 minutes and 1 hour after TBI compared with the TBI group. However, no improvement was observed at 12 and 24 hours. The A2AR antagonists resulted in no NFS improvement at 15 minutes and 1 hour, and significant improvement observed at 12 and 24 hours. Significant neuroprotective effect with an A2AR agonist were observed with cyclic adenosine monophosphate, interleukin-1ß, oxidative stress markers, catalase, and caspase-3 levels at 15 minutes and 1 hour after TBI. The A2AR antagonist showed no effect at these intervals but showed a protective effect at 12 and 24 hours after TBI. CONCLUSIONS: The A2AR agonist showed a beneficial neuroprotective effect at the early stages after TBI, and the A2AR antagonist showed a benefit at the later stages after TBI. These findings suggest that A2AR agonists and antagonists should be used in accordance with the point at which the TBI occurred.

Pial and arachnoid welding for restoration of normal cord anatomy after excision of intramedullary spinal cord tumors.

A significant postoperative problem in patients undergoing excision of intramedullary tumors is painful dysesthesiae, attributed to various causes, including edema, arachnoid scarring and cord tethering. The authors describe a technique of welding the pia and arachnoid after the excision of intramedullary spinal cord tumors used in seven cases. Using a fine bipolar forcep and a low current, the pial edges of the myelotomy were brought together and welded under saline irrigation. A similar method was used for closing the arachnoid while the dura was closed with a running 5-0 vicryl suture. Closing the pia and arachnoid restores normal cord anatomy after tumor excision and may reduce the incidence of postoperative painful dysesthesiae.