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. Management
Acoustic neuromas are managed by either surgery, radiation therapy, or observation with regular MRI scanning. With treatment, the likelihood of hearing preservation varies inversely with the size of the tumor; for large tumors, preservation of hearing is rare. Because acoustic neuromas, meningiomas and most other CPA tumors are benign, slow growing or non-growing, and non-invasive, observation is a viable management option. Stereotactic radiosurgery
The objective of irradiation is to halt the growth of the acoustic neuroma tumour, it does not excise it from the body, as the term radiosurgery or gammaknife implies. Radiosurgery is only suitable for small to medium size tumors.
The cranial nerves affected are (from most common to least common) : VIII (cochlear component), VIII (vestibular component), V

Acoustic neuroma/vestibular schwannoma
Meningioma, a tumor of the meninges or membranes that surround the nerves passing through the CPA
Cerebellar astrocytoma, a malignant tumor of star-shaped glial cells called astrocytes in the cerebellum
Intracranial epidermoid cyst
Lipoma
Glomus jugulare associated with the glossopharyngeal nerve
Idiopathic hypertrophic pachymeningitis
IgG4-related hypertrophic pachymeningitis
CPA Metastases in cancer patients with inner ear symptoms (rare)

Diagnosis
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%.