PMC5473113_01
Root exit zone compression by the anterior inferior cerebellar artery (AICA, arrowhead) was seen on axial MRI (FIESTA) (a) and was released by transposition of the AICA (b)
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F1
Magnetic resonance imaging (MRI) with fast imaging employing steady-state acquisition (FIESTA) showed that the left anterior inferior cerebellar artery (AICA) compressed the root exit zone (REZ) of the left VIIth nerve [Figure 1a]. Decompression of the REZ after transposition of the AICA was confirmed by MRI FIESTA [Figure 1b].
Abnormal muscle responses (AMR) were recorded from the orbicularis oculi muscle (upper) and mentalis muscle (lower) at the outpatient clinic (a) and during surgery (b) with 6.5 mA stimulation. AMR disappeared completely after microvascular decompression (c). AMR are not M-responses at 2.9 ms but F-responses at 10-15 ms after stimulation of the nerve to the ipsilateral frontalis muscle
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F2
With stimulation at 6.5 mA, we obtained clear AMR at 15 ms, and HFS was induced which lasted for approximately 1 minute after stimulation [Figure 2a]. The AMR detected at 20 ms [Figure 2b] disappeared just after transposition of the AICA to relieve firm compression of the VIIth nerve REZ [Figure 2c].