internal auditory canal ct without contrast

Most have an intracanalicular component, often widening the porus acusticus ( trumpeted IAM sign) (up to 90%) 5Ī small 'CSF cap' typically remains, separating intracanalicular tumour from the cochlea however, growth laterally through the cochlea (transmodiolar) or vestibule (transmacular) into the middle ear may occasionally occur Immunohistochemical staining is usually positive for S-100 protein 11. Verocay bodies: nuclear-free zones of processes lying between regions of nuclear palisading They can display two types of growth patterns:Įlongated cells with cytoplasmic processes arranged in fascicles 7 They are well-circumscribed encapsulated masses that, unlike neuromas, arise from but are separate from nerve fibres 7, which they usually splay and displace rather than engulf. Less than 5% cases arise from the cochlear component of the vestibulocochlear nerve (CN VIII) 13. In over 90% of cases, these tumours arise from the inferior division of the vestibular nerve 8. They were classically described as originating near the transition zone between glial and Schwann cells but contemporary data suggests they can originate at any point along the nerve 8,16,17. Vestibular schwannomas are benign tumours (WHO grade 1), which usually arise from the intracanalicular segment of the vestibular portion of the vestibulocochlear nerve (CN VIII) 2,4. cranial nerve dysfunction, other than vestibulocochlear), or hydrocephalus due to effacement of the fourth ventricle. Possibilities include cerebellar and brainstem symptoms (e.g. In some patients, this goes unnoticed, and presentation is delayed until the lesion is much larger and presents with symptoms related to mass effect. The typical presentation is with adult-onset sensorineural hearing loss or non-pulsatile tinnitus. Although rare, vestibular schwannomas may occur in children ref.

Bilateral vestibular schwannomas are highly suggestive of neurofibromatosis type 2 (NF2), although bilateral tumours are encountered in the familial form of vestibular schwannomas in the absence of other stigmata of NF2 5.Īlthough they usually occur between the fourth to sixth decades of life, with a median age of 50 years 11, individuals with NF2 tend to present earlier, with a peak incidence around the third decade of life ref. The vast majority (95%) of solitary lesions are sporadic.

Vestibular schwannomas account for ~8% 15 of all primary intracranial tumours 2 and 75-90% of CPA masses 1,2,8.

Internal auditory canal ct without contrast