PMC3872663_01
Magnetic resonance T2W images showing (a) a large posterior fossa arachnoid cyst more on left side extending into the left cerebellopontine angle with marked compression of the left cerebellar hemisphere and (b) there is caudal displacement of the cerebellar tonsils with obstruction of foramen magnum and associated syringomyelia
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F1
Patient was investigated with magnetic resonance imaging (MRI) brain and cervical spine and it showed giant retrocerebellar arachnoid cyst extending into the left cerebellopontine angle causing descent of the cerebellar tonsils across the foramen magnum with a syringomyelic cavity extending from C1 down and associated ventriculomegaly [Figure 1].
(a-c) Section showing cyst wall lined by meningeal cells showing stratification with subepithelial tissue showing acute inflammatory cells (H and E, x100), (d) Section showing cyst wall lined by meningeal cells showing stratification with neutrophilic infiltrate and the subepithelial fibrocollagenous tissue shows acute inflammatory infiltrate (H and E, x400)
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F2
Histopathological examination of the cyst wall showed a cuboidal layer of arachnoid cells suggestive of arachnoid cyst [Figure 2].
Following magnetic resonance images showing the reduction in the size of cyst and also reduction in the mass effect over cerebellum and brain stem structures
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F3
Follow-up images showed a reduction in the size of the cyst and reduction in the mass effect over cerebellum and brain stem structures [Figure 3].