Giant vestibular schwannomas: focusing on the differences between the solid and the cystic variants

In vestibular schwannomas (VS), the tumour size, as well as the size of the cystic component, have a considerable bearing on the outcome. This study addresses the differences between the cystic and solid variants of giant vestibular schwannomas. The study included 62 patients with giant VSs, of which 40 were solid and 22 were cystic (those in which cystic component greater or equal to 30% of the total tumour volume). The cystic tumour group was further divided into type A (31-60% volume of the cyst within tumour), type B (61-90% intra-tumoural cyst volume) and type C (more than 90% volume of the cyst). The clinicoradiological features, operative findings, histopathological characteristics and outcome of surgery of the two groups were compared. The mean duration of symptoms for the solid and cystic tumours were 21.1 and 26.2 months, respectively. However, six patients with cystic tumours showed recent and rapid neurological deterioration after a protracted existence. Papilloedema, lower cranial nerve involvement, facial paraesthesias and preoperative hydrocephalus were significantly more in cystic tumours. Total excision was achieved in 38 of the solid and 18 of the cystic tumours. VIIth nerve preservation was higher in the cystic lesions [solid 33/40 (82.5%), cystic 21/22 (95.4%)]. Myxoid degeneration, lobular growth patterns and cellular atypia were more prominent in the cystic variants. The giant vestibular schwannomas were associated with a higher incidence of cystic degeneration than has been reported for smaller tumours in literature. In cystic lesions, VIIth nerve preservation was higher due to early decompression of the lesion that facilitated in early identification of the VIIth nerve, except in patients with type C cystic tumour.