The screening MRI protocol was more cost-effective than a full MRI protocol with a willingness-to-pay from $0 to 20,000 USD. Results The mean charge for a full MRI with contrast was significantly higher than a screening MRI ($4089 ± 1086 versus $2872 ± 741 p < 0.05). One-way and probabilistic sensitivity analyses were completed to determine CE model threshold points for MRI performance characteristics and charges. Institutional charge data were obtained using representative patient cohorts. Vestibular schwannoma prevalence, MRI specificity and sensitivity, and gadolinium anaphylaxis incidence were obtained through literature review. If a patient were to have a positive screening MRI, s/he received a full MRI. Methods A decision tree was constructed to evaluate full MRI and screening MRI strategies for patients with asymmetric sensorineural hearing loss. Purpose We aimed to determine if a non-contrast screening MRI is cost-effective compared to a full MRI protocol with contrast for the evaluation of vestibular schwannomas. We think that 3D-CISS images better show the features influencing surgical outcome, but that contrast-enhanced T1-weighted images are required for diagnosis. The direction of displacement of the facial nerve did not correlate with facial palsy or hearing loss. The 3D-CISS sequence, by virtue of its high contrast resolution was superior to T1-weighted images ( P<0.05) for detection of the fundal involvement. Involvement of the fundus of the internal auditory canal (IAC) and a small distance between the lateral border of the tumour and the fundus were correlated significantly with hearing loss (r=-0.81 and -0.75, respectively). Both techniques adequately demonstrated all tumours. 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. Tumors of the cerebellopontine angle (CPA) are frequent acoustic neuromas and meningiomas represent the great majority of such tumors.
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