Microvascular Decompression for Classic Trigeminal Neuralgia: Determination of Minimum Clinically I

BACKGROUND: Outcomes studies use patient-reported outcome (PRO) measurements to assess treatment effectiveness, but can lack direct clinical meaning. Minimum clinically important difference (MCID) calculation provides a point estimate of the critical threshold needed to achieve clinically relevant treatment effectiveness. MCID remains uninvestigated for microvascular decompression (MVD), a common surgical procedure for trigeminal neuralgia. OBJECTIVE: We aimed to determine MCID for the most commonly used PRO measures of pain after MVD: Visual Analog Scale (VAS) and Barrow Neurological Institute Pain Scale (BNI-PS). METHODS: Sixty consecutive patients with classic trigeminal neuralgia who decided to undergo MVD by a single surgeon were prospectively assessed with VAS and BNI-PS preoperatively and 2 years postoperatively. Three anchors were used to assign each patient's outcome. We then used 3 well-established, anchor-based methods to calculate MCID. RESULTS: Patients experienced significant improvement in both VAS (9.9 vs 2.0, P < .001) and BNI-PS (5.0 vs 1.9, P < .001) after MVD. The area under the receiver-operating characteristic curve was greater for BNI-PS than for VAS for all 3 anchors, indicating that BNI-PS is probably better suited for calculating MCID. The 3 MCID calculation methods generated a range of MCID values for each of the PROs (VAS: 1.40-8.87, BNI-PS: 0.95-3.26). CONCLUSION: MVD-specific MCID is highly variable based on calculation technique. Some of these calculations appear to either overestimate or underestimate the patients' preoperative expectations. When the different MCID methods are averaged, the results are clinically appropriate and consistent with preoperative expectations. The average MCID for VAS is 6.25 and for BNI-PS is 2.44. ABBREVIATIONS: AUC, area under the receiver-operating characteristic curve BNI-PS, Barrow Neurological Institute Pain Scale CI, confidence interval HTI, Health Transition Index MCID, minimum clinically important difference MDC, minimum detectable change MVD, microvascular decompression PRO, patient-reported outcome SD, standard deviation TN, trigeminal neuralgia VAS, Visual Analog Scale

http://journals.lww.com/neurosurgery/Fulltext/2013/05000/Microvascular_Decompression_for_Classic_Trigeminal.8.aspx

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Julio Pereira, MD

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