PMC5309449_01
(a) Brain CT showing a 3 x 3x 4 cm 4th ventricle mass, predominantly hyperdense, causing active triventricular dilation. (b) MRI showing a heterogeneous lesion with cystic areas in both T1WI (c) and T2WI (b and d), scarce areas of enhancement (c) and associated edema (b). Linear hypointense signal, in T2WI, along the pial surface/subarachnoid space of the convexity sulci, cerebellar folia, and brainstem and spinal surface, is typical of SS (b, d, e, f). Signs of compensated hydrocephalus are also present (bulging suprasellar cistern, remodellation of the sella turcica) (c and d)
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F1
Emergent computed tomography (CT) [Figure 1a] revealed a heterogeneous fourth ventricle mass causing acute obstructive hydrocephalus (HCP). A brain magnetic resonance imaging (MRI) was then obtained [Figure 1b-d], which confirmed the presence of a fourth ventricle lesion displaying signs of both intra and extratumoral hemorrhage with SS.
Sequence of photographs obtained during the microsurgical procedure. (a and b) A bilateral telovelar approach was carried out. Notice the brownish colored pial surface of the cerebellum, typical of SS. After evacuation of xanthochromic CSF, a rubbery mass was identified occupying the fourth ventricular chamber. A friable xantochromic material covered both the tumor and the boundaries of the fourth ventricle. Although this material facilitated the definition of a plane of dissection that allowed an en block resection of the tumor (c), it precluded the identification of the anatomical structures of the floor of the fourth ventricle (d), except clear CSF gushing forth from the aqueduct
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F2
The tumor was resected through a bilateral telovelar approach with neurophysiological monitoring [Figure 2].
(a) Macroscopic aspect of the lesion, with a heterogeneous surface delimited by a capsule of variable width, which is irregular on one of its borders, with a brownish content. (b) Great vessels with thickened walls of cavernous appearance and minimal areas of tumor in the periphery of the lesion (arrow) (H and E x4). (c) Tumor cells arranged around hyalinized vessels and signs of recent hemorrhage (H and E x10). (d) Hemosiderinic pigment (arrows) and tumoral cells with an eosinophilic unclearly delimited cytoplasm and nuclei with finely granular chromatin and small nucleoli (H and E x40). (e) Perivascular tumor cells express GFAP. (f) Dot-like intracytoplasmic EMA immunoreactivity in tumoral cells
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F3
These tumor cells were glial fibrillary acidic protein (GFAP) positive, and they showed dot-like intracytoplasmic epithelial membrane antigen (EMA) immunoreactivity [Figure 3].