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Hyper Smash

Friday, April 16, 2010

Pedicle Screws & Triggered EMGs!

Spine (Phila Pa 1976). 2010 Jan 15;35(2):E43-8.

Usefulness of electromyography compared to computed tomography scans in pedicle screw placement.
Duffy MF, Phillips JH, Knapp DR, Herrera-Soto JA.
STUDY DESIGN: This is a retrospective analysis of 30 pediatric deformity surgeries. OBJECTIVE: The purpose of this study was to evaluate the accuracy of neuromonitoring in comparison to postoperative computed tomography scans for pedicle screw position. SUMMARY OF BACKGROUND DATA: Triggered electromyography potentials in aiding the placement of lumbar pedicle screws are considered useful; however, this method is less accepted in thoracic screw placement. METHODS: Thirty pediatric deformity surgeries were reviewed. All screws were placed using fluoroscopic assistance. Electromyography data were obtained on all screws. Every patient underwent postoperative computed tomography scanning. Computed tomography scans were assessed by all authors, and each screw was classified. Sensitivity, specificity, negative predictive value, and likelihood ratios were determined for the cut-off value of an electromyography > or =6 mA. RESULTS: A total of 329 screws were reviewed. No complications occurred. An overall accuracy of 93% was obtained. No retained screw had greater than 2 mm medial pedicle wall breach. Nine screws were removed intraoperatively due to medial breach. The mean electromyography potential for all classes of screws was not statistically different (P > 0.1). The negative predictive value of the test was 0.92 in the thoracic spine and 0.93 in the lumbar spine. The negative likelihood ratios were 0.96 and 0.35 for the thoracic and lumbar spines respectively, and the positive likelihood ratio was 1.4 for the thoracic spine and 12.5 for the lumbar spine. CONCLUSION: Thoracic and lumbar pedicle screws are safe surgical options in the treatment of pediatric scoliosis. Comparison of electromyography potentials and postoperative computed tomography scans showed no statistically significant difference for all classes of screws. The likelihood ratio for electromyography testing was more clinically significant in the lumbar spine. A triggered electromyography value greater than or equal to 6 mA has a high likelihood of that screw being in the "safe zone." However, there is no true electromyography cut-off value that guarantees accurate placement and avoidance of neurologic injury.

New Guidlines for TCD!

J Neuroimaging. 2010 Mar 17. [Epub ahead of print]
American Society of Neurophysiologic Monitoring and American Society of Neuroimaging Joint Guidelines for Transcranial Doppler Ultrasonic Monitoring.

Edmonds HL Jr, Isley MR, Sloan TB, Alexandrov AV, Razumovsky AY.
The American Society of Neurophysiologic Monitoring (ASNM) and American Society of Neuroimaging (ASN) Guidelines Committees formed a joint task force and developed guidelines to assist in the use of transcranial Doppler (TCD) monitoring in the surgical and intensive care settings. Specifically, these guidelines: (1) delineate the objectives of TCD monitoring; (2) characterize the responsibilities and behaviors of the sonographer during monitoring; (3) describe methodological and ethical issues uniquely relevant to monitoring. The ASNM and ASN strongly support the positions that (1) acquisition and interpretation of intraoperative TCD ultrasonograms be performed by qualified individuals, (2) service providers define their diagnostic criteria and develop on-going self-validation programs of these performance criteria in their practices. We agree with the guidelines of other professional societies regarding the technical and professional qualifications of individuals responsible for TCD signal acquisition and interpretation (Class III evidence, Type C recommendation). On the basis of current clinical literature and scientific evidence, TCD monitoring is an established monitoring modality for the: (1) assessment of cerebral vasomotor reactivity and autoregulation; (2) documentation of the circle of Willis functional status; (3) identification of cerebral hypo- and hyperperfusion, recanalization and re-occlusion; and (4) detection of cerebral emboli (Class II and III evidence, Type B recommendation). J Neuroimaging 2010;XX:1-7.