The development of cystic components in intracranial schwannoma is not
rare but has not been emphasized in any previous series or reviews. C
ystic areas usually develop from coalescence of mucinous or microcysti
c areas in Antoni B tissue of the schwannoma. Hemorrhagic degeneration
or necrosis due to the characteristic vascular abnormalities of these
lesions may cause the formation of tiny cysts but not large ones. The
formation of an associated arachnoid cyst and, rarely, the formation
of cysts in glandular or pseudoglandular elements have also been repor
ted. Awareness of the potential for partially or largely cystic schwan
noma of the acoustic or trigeminal nerve is important for both the dif
ferential diagnosis and surgical planning. Surgically proven large cys
ts (occupying more than 50% of tumour volume) were detected preoperati
vely by computed tomography (CT) in 7 of the 35 cases of acoustic nerv
e schwannoma and both cases of trigeminal nerve schwannoma managed sur
gically at the authors' institution between 1980 and 1990. In a review
of the literature the authors found descriptions of low-attenuation r
egions in CT scans for an average of 13% of acoustic and 29% of trigem
inal nerve sheath tumours. Magnetic resonance imaging, ideally perform
ed after intravenous administration of contrast material, also plays a
n important role in the detection and delineation of these tumour cyst
s,