Radiography Subsequent to diagnosis of sensorineural hearing loss, and differential diagnosis of retrocochlear or neural etiologies, radiological assessment of the CPA is performed to assess the presence of anatomical retrocochlear lesions. Traditional protocols Before the advent of MRI, electronystagmography and Computed Tomography were employed for diagnosis of acoustic neuroma. Auditory brainstem response audiometry and adjunct tests The auditory brainstem response (ABR) test gives information about the inner ear (cochlea) and nerve pathways for hearing via ongoing electrical activity in the brain measured by electrodes placed on the scalp. Five different waves (I to V) are measured for each ear. Each waveform represents specific anatomical points along the auditory neural pathway. Delays of one side relative to the other suggest a lesion in cranial nerve VIII between the ear and brainstem or in the brainstem itself. The most reliable indicator for acoustic neuromas from the ABR is the interaural latency differences in wave V: the latency in the impaired ear is prolonged. Different studies have indicated the sensitivity of ABR for detection of acoustic neuromas 1cm or larger to be between 90 and 95%. Sensitivity for neuromas smaller than 1cm are 63-77%. A newer technology, stacked ABR, may have sensitivity as high as 95% with specificity 88% for smaller tumors. ABR is considerably more cost effective, but MRI provides more information. Stapedius reflex (SR) and caloric vestibular response (CVR) are non-invasive otologic tests for auditory neural function. These are not primary diagnostics for CPA neuromas, and are usually used in conjunction with ABR. Magnetic resonance imaging Several different types of magnetic resonance imaging (MRI) may be employed in diagnosis: MRI without contrast, Gd contrast enhanced T1-weighted MRI (GdT1W) or T2-weighted enhanced MRI (T2W or T2*W). Non-contrast enhanced MRI is considerably less expensive than any of the contrast enhanced MRI scans. The gold standard in diagnosis is GdT1W MRI. The reliability of non-contrast enhanced MRI is highly dependent on the sequence of scans, and the experience of the operator.
Cerebellopontine angle syndrome
Trigeminal trophic syndrome
Bulbar palsy
Chiasmal syndrome
Lateral pontine syndrome
Occipital horn syndrome
Jugular foramen syndrome
Medial pontine syndrome