Parathyroid hormone decline 4 hours after total thyroidectomy accurately predicts hypocalcemia.

BACKGROUND: The level of parathyroid hormone (iPTH) serum has been controversial in the prediction of postthyroidectomy hypocalcemia. Analysis of the decrease between preoperative and postoperative iPTH levels should be more accurate. Therefore, the aim of our study was to prospectively establish the reliability of the iPTH decrease for early diagnosis of postoperative hypocalcemia and to identify the patients who are not at risk for hypocalcemia. METHODS: A prospective study of 137 consecutive patients who underwent total thyroidectomy was performed. Serum iPTH level was measured preoperatively and 4 hours postoperatively (iPTH(H4)). The sensitivity, specificity, and positive and negative predictive values for the iPTH(H4) and for the iPTH decline were estimated by confidence interval from thresholds determined by ROC curve analysis. RESULTS: Thirty-nine patients developed hypocalcemia (28.5%). Patients who developed hypocalcemia had a significantly lower iPTH(H4) and a significantly greater iPTH decrease (P < .001). The thresholds enabling prediction of hypocalcemia were 19.4 ng/L for iPTH(H4) and 68.5% for iPTH decline. Sensitivity, specificity, and positive and negative predictive values for iPTH(H4) were 84.6%, 92.9%, 82.5%, and 93.8% (overall accuracy, 90.5%). iPTH decline was more accurate to predict hypocalcemia (sensitivity, 97.4%; specificity, 95.9%; positive predictive values 90.5%; negative predictive values, 98.6%; and overall accuracy, 96.4%). CONCLUSION: The decrease in iPTH is more precise than the iPTH(H4) alone and can accurately predict hypocalcemia after total thyroidectomy. Patients with a decrease in iPTH less than 68.5% can be discharged at postoperative day one without any supplementation. Patients with iPTH decline more than 68.5% should be administered calcium and vitamin D supplementation before symptoms appear.

Midmodiolar reconstruction as a valuable tool to determine the exact position of the cochlear implant electrode array.

HYPOTHESIS: A midmodiolar reconstruction with multislice computed tomography could potentially be used clinically to determine the cochlear implant electrode array position if the technique was validated with a cadaveric temporal bone study. BACKGROUND: Several radiologic studies using sophisticated techniques have been described. This study was designed to validate a standard multislice computed tomography scan technique to determine the electrode array position. METHODS: This ex vivo study was conducted on 18 cadaveric temporal bones without malformation. Cochlear electrode dummies were implanted by a single experimented surgeon with the Advance Off-Stylet technique. After randomization, the placement was processed through an anteroinferior or superior cochleostomy for respective scala tympani or vestibuli positioning with direct location of the basilar membrane. Cadaveric temporal bones were then scanned (Philips Brilliance 40 computed tomographic scan) and reconstructed into the midmodiolar computed tomography scan plane (± 45 degrees, z-axis in the cochlear coordinate system). Two independent neuroradiologists, who were unaware of the implanted scala, evaluated the electrode array position on a computed tomographic scan through the midmodiolar reconstruction. In the end, the microanatomic study was the criterion standard to determine the exact scala localization of the electrode array. RESULTS: Nine electrodes were inserted into the scala tympani, and 9 were inserted into the scala vestibuli. According to our anatomic criterion standard, the midmodiolar reconstruction sensitivity and the specificity for the scala tympani position were 0.875 (range, 0.722-1.0) and 1.0, respectively; the sensitivity and specificity for dislocation and the scala vestibuli position were both 1.0. The radioanatomic concordance was 0.94 (range, 0.89-0.98) for determining the electrode array position into scalae with midmodiolar reconstruction. CONCLUSION: Our cadaveric study validates midmodiolar reconstruction as a valuable tool to routinely determine the precise position of the cochlear implant electrode array. This study opens the field for further clinical studies.