PMC4533476_01
A: Postcontrast axial T1-weighted magnetic resonance (MR) image revealing a dumbbell-shaped mass in both the left middle fossa and the left prepontine cistern. B: Postcontrast sagittal MR image showing a heterogeneously enhanced dumbbell-shaped mass with marked displacement of the brainstem. C: Three-dimensional venography with a view of the skull base, revealing a sphenobasal vein (arrow) and erosion of the left petrous apex.
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F1
T2-weighted images, the lesion was hyperin-tense compared with the surrounding brain regions and showed heterogeneous enhancement after contrast injection (Fig. 1A, B). Three-dimensional venography with a skull base view revealed a sphenobasal vein and left petrous apex erosion (Fig. 1C). The preoperative differential diagnosis was trigeminal schwannoma.
The first operation via an anterior transpetrosal approach. A: An intraoperative picture showing a tumor in the cavernous sinus, B: a tumor in the posterior fossa, and C: a tumor entering Dorello's canal with the thin abducens nerve on the surface. D: The second operation via a lateral suboccipital approach. An intraoperative picture showing the tumor mass between the VIIth and VIIIth nerve complex and the lower cranial nerves (IXth-XIth). PICA: posterior inferior cerebellar artery.
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F2
The tumor did not adhere to the trigeminal nerve (Fig. 2A) but partially adhered to the surrounding structures. In the posterior fossa, the abducens nerve run on the tumor's surface, and the tumor extended into the cavernous sinus along with the abducens nerve through Dorello's canal, but not Meckel's cave (Fig. 2B, C). Retraction of the cerebellum after craniectomy exposed a yellowish tumor mass extending from the caudal side of the lower nerves to the space between the lower cranial nerves and the facial and vestibulocochlear nerve complex (Fig. 2D).
Postcontrast axial (A) and sagittal (B) T1-weighted magnetic resonance (MR) images after the first operation via the anterior transpetrosal approach revealing a residual tumor in the left prepontine cistern. Postcontrast axial (C) and sagittal (D) T1-weighted MR images revealing a tumor subjected to subtotal removal using the lateral suboccipital approach.
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F3
Postoperative MRI showed a residual tumor in the lower posterior fossae (Fig. 3A, B). Because the tumor strongly adhered to the brainstem, it was debulked and dissected piecemeal from the adjacent neurovascular structures, with the capsule remaining attached to the brainstem (Fig. 3C, D).
Histological specimen showing nuclei forming palisades and the typical fascicular constitution of the schwannoma (hematoxylin and eosin staining).
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F4
The tissue showed Antoni A areas consisting of closely apposed spindle-shaped cells, often in a palisading pattern (Fig. 4).