A patient is suspected to have Vestibular Shwanomma. The investigation of choice for its diagnosis is

(B) Gadolinium enhanced MRI # Neurological tests. Complete examination of cranial nerves, cerebellar functions, brainstem signs of pyramidal and sensory tracts should be done. Fundus is examined for blurring of disc margins or papilloedema.> Radiological tests, (a) Plain x-rays (transorbital, Stenver's, Towne's and submentovertical views) give positive findings in 80% of patients. However, small intracanalicular tumours are not detected.> CT scan. A tumour that projects even 0.5 cm into the posterior fossa can be detected by a CT scan. If combined with intrathecal air, even the intrameatal tumour can be detected.> CT scan has replaced earlier methods of pneumoencephalography and myodil meatography.> MRI with gadolinium contrast. It is superior to CT scan and is the gold standard for diagnosis of acoustic neuroma. Intracanalicular tumour, of even a few millimeters, can be easily diagnosed by this method.> Vertebral angiography. This is helpful to differentiate acoustic neuroma from other tumours of cerebellopontine angle when doubt exists.> Electric response audiometry. It is very useful in the diagnosis of retrocochlear lesions.> In the presence of VINth nerve tumour, a delay of >0.2 msec in wave V between two ears is significant.> CSF examination. Protein level is raised. Lumbar puncture is usually avoided.