PMC8645491_01
Preoperative MRI images. (a) Sagittal T1-weighted contrast-enhanced image; (b) coronal T1-weighted contrast-enhanced image; (c) axial T1-weighted contrast-enhanced image; (d) Sagittal FSE T2-weighted image; (e) axial T2-weighted sequence; and (f) axial T2-weighted sequence.
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F1
The brain MRI showed an extra-axial pontomedullary lesion with the classic appearance of a CM, that is, a reticulated salt-and-pepper core, surrounded by a halo rim [Figure 1].
Intraoperative images. (a) A reddish pulsating lesion in the cerebellopontine angle; (b) view of the CM (white arrow) and the distal course of the abducens nerve entering the Dorello's canal (black arrow); (c) severed abducens nerve distal to the lesion (black arrow); (d) the resected CM with part of the abducens nerve (black arrow), passing through the lesion; (e) the prepared nerve graph (3 cm of the greater auricular nerve); (f) resection cavity after removal of the lesion, with the interposition nerve graft placed meticulously between the proximal and distal ends of the abducens nerve.
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F2
Since the lesion could not be separated from the nerve and its integrity was unclear, we resected the CM by cutting the proximal and distal portions (before the Dorello's canal) of the sixth cranial nerve [Figure 2].
Histopathological image of the lesion. (a) Blood-filled medium-sized vessels (H&E staining; x100); (b) large cavernous space (H&E staining; x100); and (c) black stained elongated nuclei of nerve fibers (S100 protein staining, x100).
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F3
The histopathological examination of the lesion demonstrated typical characteristics of a CM [Figure 3]. To determine the origin of the lesion, immunohistochemistry staining for the S100 marker was carried out, and the results showed the intraneural origin of the lesion [Figure 3].