Quantitative analysis of ROI MR imaging data is a valid method of predicting the outcome of acute facial nerve palsy during the first days after onset of symptoms and thus at a time when it is not yet possible to obtain valuable prognostic information by using electrophysiologic methods.
Our objective was to assess the prognostic value of measurements of the degree of contrast enhancement of the intratemporal segments of the facial nerve. We prospectively obtained MRI, slice thickness <1 mm of 20 patients with a facial palsy on the first day of inpatient treatment, and measured contrast enhancement of the nerve. The data were compared with compound muscle action potential (CMAP) measurements and the clinical course. Analysis of the initial enabled differentiation of three patients whose palsy was to show no improvement from 17 whose palsy was to resolve as expected. No patient with a poor outcome showed lesser increase in signal in the internal auditory canal, pars tympanica and pars mastoidea than patients who fully recovered. In no patient who had been diagnosed on the basis of the initial MRI as having a "normal" palsy was the amplitude of the (CMAP) reduced to less than 20% that of the normal side. Measurement of contrast enhancement was thus shown to be a prognostic indicator and may provide a basis for a differential treatment of facial palsy.
The objective of this study was to evaluate signal intensity increases in the greater petrosal nerve after contrast agent administration to gather information on the etiology of idiopathic peripheral facial paralysis. Magnetic resonance images were obtained from 18 patients who received inpatient medical treatment for acute peripheral facial nerve palsy. Images of intratemporal segments of the facial nerve were taken with a slice thickness of 0.75 mm. After multiplanar reconstruction, regions of interest (ROI) were defined in the proximal segment of the greater petrosal nerve. After multiplanar reconstruction, it was possible to visualize the greater petrosal nerves of all 18 patients. The nerve's average diameter was found to be 0.68 mm (range 0.5-0.9). Signal intensity increased by an average of 50.3% (range -10-146%) after contrast agent administration. Whereas this intensity was slightly reduced in two patients, it was increased in 16. No correlation could be established between greater signal intensity and medical history, clinical condition, laboratory findings, or electrophysiological data. In contrast to quantitative measurements in the facial nerve, ROI measurements in the greater petrosal nerve do not correlate with medical history, clinical condition, or laboratory findings. For this reason, MRI of this nerve does not enable us to draw conclusions on the etiology of idiopathic peripheral facial paralysis.
The measured quantitative increase in signal intensity after administration of contrast medium is more reliable than subjective assessment. The quantitative method enables reproducible signal intensity measurements even for different window settings and can be easily and swiftly performed at the workstation.
MRI has a prognostic value at an early stage of the illness. In the clinical setting this measurement is easy to perform, so that it is possible to obtain prognostic information at a stage when causal treatment is still possible.
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