There was a significant correlation between the size of the tumour and facial palsy (r=-0.72). Postoperatively six (27%) had a facial palsy and eight (36%) had hearing loss. We studied 22 patients with vestibular schwannomas having hearing-preservation surgery. We compared contrast-enhanced T1-weighted and 3D constructive interference in steady state (CISS) sequences for demonstrating possible prognostic factors in hearing-preservation surgery for vestibular schwannoma. Abbreviations: CPA cerebellopontine angle, CSF cerebrospinal fluid A close association between CT and MR imaging findings is very helpful in establishing the preoperative diagnosis for unusual lesions of the CPA. Finally, CPA lesions can be secondary to an exophytic brainstem or ventricular tumor (glioma, choroid plexus papilloma, lymphoma, hemangioblas-toma, ependymoma, medulloblastoma, dysembryoplastic neuroepithe-lial tumor). Tumors can also invade the CPA by extension from the petrous bone or skull base (cholesterol granuloma, paraganglioma, chondromatous tumors, chordoma, en-dolymphatic sac tumor, pituitary adenoma, apex petrositis). CPA masses can primarily arise from the cerebellopontine cistern and other CPA structures (arachnoid cyst, nonacoustic schwannoma, aneurysm, melanoma, miscellaneous meningeal lesions) or from embryologic remnants (epidermoid cyst, dermoid cyst, lipoma).
In addition, it is essential to analyze attenuation at computed tomography (CT), signal intensity at magnetic resonance (MR) imaging, enhancement, shape and margins, extent, mass effect, and adjacent bone reaction. The site of origin is the main factor in making a pre-operative diagnosis for an unusual lesion of the CPA. However, a large variety of unusual lesions can also be encountered in the CPA. Structures that can be seen are facial and vestibulocochlear nerves.Tumors of the cerebellopontine angle (CPA) are frequent acoustic neuromas and meningiomas represent the great majority of such tumors. The anatomy of the internal auditory canal is best seen on high-resolution T2-weighted image sequences. Narrow duplicated internal acoustic canal 2 From here three bundles emerge: superior and inferior division of the vestibular nerve and the nerve from the posterior semicircular canal (see article: vestibulocochlear nerve (CN VIII) for further details). In addition to the three nerves which enter it, it also contains the vestibular ganglion ( ganglion of Scarpa). See mnemonic for the position of the nerves in the IAC. Inferior: cochlear nerve and inferior vestibular nerve (IVN) the cochlear nerve is situated anteriorly
Superior: facial nerve and superior vestibular nerve (SVN) the facial nerve is anterior to the SVN and is separated from it laterally by Bill's bar, a vertical ridge of bone This horizontal ridge divides the canal into superior and inferior portions: Their position is most constant in the lateral portion of the meatus which is anatomically divided by the falciform crest. Superior vestibular nerve (component of CN VIII) Inferior vestibular nerve (component of CN VIII) Nervus intermedius (sensory component of CN VII)įacial motor root (motor component of CN VII) There are five nerves that run through the IAM: Labyrinthine artery (usually a branch of the AICA or basilar artery) The canal narrows laterally, and the lateral boundary is the fundus, where the canal splits into three distinct openings, one of which is the facial nerve canal. The margins of the opening are smooth and rounded, and the canal is short (1 cm), running laterally to the bone. The opening of the IAM, the porus acusticus internus, is located within the cranial cavity, near the posterior surface of the temporal bone.
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