Acoustic Neurinoma

Definition

Tumor arising from the nerve sheath cells. Other terms to describe this entity include acoustic schwannoma, neurilemoma, acoustic neuroma. This tumor arises on the cranial nerve VIII (acoustic). It is presumably formed by Schwann cells (or their progenitors).

Schwannoma arises eccentrically within the nerve, displacing the axons and sparing the nerve. This feature makes nerve-sparing surgery possible in some cases.

Tissue architecture of the tumor is characterized by dense or loose structures named Antoni A or B respectively. Acoustic schwannoma corresponds histologically to WHO grade I. Maligant progression of acoustic schwannoma is extremely rare. Clinical presentation typically includes tinnitus (ringing in the ear) and hearing loss. Magnetic resonance imaging (MRI) is the study of choice for detection of this tumor and usually reveals well-circumscribed, sometimes cystic and enhancing mass. Treatment modalities employed include observation, surgical resection and/ or...