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Bell Palsy: Quantitative Analysis of MR Imaging Data as a Method of Predicting Outcome¹

¹ From the Department of Neurology, Division of Neuroradiology, University of Heidelberg Medical Center, Im Neuenheimer Feld 400, D-69120 Heidelberg, Germany (B.K., C.S., K.S.); and Departments of Radiology (B.K., W.B.) and Neurology (F.G.), Armed Forces Hospital, Ulm, Germany. Received October 22, 2002; revision requested January 6, 2003; final revision received May 23; accepted June 16. Address correspondence to B.K. (e-mail: bodo_kress@med.uni-heidelberg.de).

View larger version (166K): [in a new window]   Figure 1a. Transverse T1-weighted fast-field-echo MR images (9.4/3.2; section thickness, 0.7 mm) through the cerebellopontine angle on the left side of the face in a 47-year-old man who had had Bell palsy for 4 days. Images were obtained (a, c) before and (b, d) after contrast agent administration. Images clearly show contrast agent uptake in the IAC ROI (circled area in b and d); ROI measurements provided accurate information regarding the neurovascular bundle. The IAC in this patient showed a signal intensity increase of 84% after contrast agent administration. 1 = IAC, 2 = geniculate ganglion, 3 = labyrinth portion.

View larger version (168K): [in a new window]   Figure 1b. Transverse T1-weighted fast-field-echo MR images (9.4/3.2; section thickness, 0.7 mm) through the cerebellopontine angle on the left side of the face in a 47-year-old man who had had Bell palsy for 4 days. Images were obtained (a, c) before and (b, d) after contrast agent administration. Images clearly show contrast agent uptake in the IAC ROI (circled area in b and d); ROI measurements provided accurate information regarding the neurovascular bundle. The IAC in this patient showed a signal intensity increase of 84% after contrast agent administration. 1 = IAC, 2 = geniculate ganglion, 3 = labyrinth portion.

View larger version (165K): [in a new window]   Figure 1c. Transverse T1-weighted fast-field-echo MR images (9.4/3.2; section thickness, 0.7 mm) through the cerebellopontine angle on the left side of the face in a 47-year-old man who had had Bell palsy for 4 days. Images were obtained (a, c) before and (b, d) after contrast agent administration. Images clearly show contrast agent uptake in the IAC ROI (circled area in b and d); ROI measurements provided accurate information regarding the neurovascular bundle. The IAC in this patient showed a signal intensity increase of 84% after contrast agent administration. 1 = IAC, 2 = geniculate ganglion, 3 = labyrinth portion.

View larger version (167K): [in a new window]   Figure 1d. Transverse T1-weighted fast-field-echo MR images (9.4/3.2; section thickness, 0.7 mm) through the cerebellopontine angle on the left side of the face in a 47-year-old man who had had Bell palsy for 4 days. Images were obtained (a, c) before and (b, d) after contrast agent administration. Images clearly show contrast agent uptake in the IAC ROI (circled area in b and d); ROI measurements provided accurate information regarding the neurovascular bundle. The IAC in this patient showed a signal intensity increase of 84% after contrast agent administration. 1 = IAC, 2 = geniculate ganglion, 3 = labyrinth portion.

View larger version (30K): [in a new window]   Figure 2. Graph shows specificity (black bars) and sensitivity (white bars) in percentages for the signal intensity increase in five segments of the intratemporal portion of the facial nerve as a prognostic tool for clinical outcome. Assuming a threshold value of a signal intensity increase of 90%, the specificity and sensitivity of the measurements in the IAC are particularly high, with only one false-positive and no false-negative results occurring. The specificity and sensitivity of the measurements in the labyrinth portion are also sufficiently high for diagnostic purposes, while measurements in the tympanic portion and in the mastoid portion have relatively low sensitivity and measurements at the geniculate ganglion have only moderate specificity and low sensitivity.

View larger version (27K): [in a new window]   Figure 3. Graph illustrates comparison of signal intensity increases measured in the IAC (after contrast agent administration) with clinical course. No patient with idiopathic facial paralysis who had a favorable outcome (35 patients) had higher signal intensity increases than any of the patients who developed chronic paralysis (four patients [the square at the level of the signal intensity increase of 110% represents two patients]).

View larger version (16K): [in a new window]   Figure 4. Graph illustrates correlation between signal intensity increases in the IAC and the results of CMAP measurements. MR images in patients with a low CMAP (and therefore a poor prognosis) showed a signal intensity increase in the IAC of more than 100%. If results in the patient with a 302% increase in signal intensity are excluded, correlation decreases to 30%, but the sensitivity of an increase in signal intensity stays at 100%.

View larger version (23K): [in a new window]   Figure 5. Graph illustrates correlation between the MR imaging index and signal intensity increases measured in the five segments of the intratemporal portion of the facial nerve. A lower degree of correlation was observed in the distal segments of the nerve. A high degree of correlation (85%) was found between the MR imaging indexes and the measurements of signal intensity increase in the IAC.