Cerebellopontine angle (CPA) tumors are masses located in the region between the cerebellum and pons. They constitute the most frequently diagnosed tumors of the posterior fossa and account for up to 10% of all intracranial neoplasms.
A majority of the CPA tumors are benign and can be divided into various types, depending on their histopathological features, such as lipomas, acoustic neuromas, meningiomas, hemangiomas and vascular malformations. Most CPA tumors belong to the category of vestibular neuromas (VS, acoustic neuromas) and their symptomatology is dependent upon their anatomical location and their size.
Vestibular neuromas typically cause no symptoms in the initial stages of the disease; occasionally, unilateral tinnitus, headaches, and sensorineural impairment are experienced . Sudden-onset hearing loss is attributed to vascular irregularities since the impairment caused by the acoustic neuroma develops gradually . Similarly, during the initial stages of the condition, vertigo and imbalance tend to be mild, since the unaffected side compensates for the abnormalities. Other symptoms include facial asymmetry, pain, and weakness; These symptoms also tend to be mild and are attributed to the expansion of the tumor with compression of the trigeminal nerve  . A severe degree of facial asymmetry and weakness experienced by the patient usually indicates an extensive tumor and constitutes a more emergent condition.
At the more progressed stages of the disease, ataxia, tremor and loss of coordination begin to manifest. If a VS is left untreated or undiagnosed, it is expected to ultimately lead to communicative hydrocephalus due to elevated intracranial pressure .
Meningiomas are a different subcategory of CPA tumors and are the most frequently diagnosed CPA tumors of non-acoustic nature. Tinnitus, deafness, and imbalance are amongst the primary symptoms induced by meningiomas. Should they expand excessively, symptoms associated with trigeminal involvement and hydrocephalus may be elicited.
Vestibular schwannomas are optimally depicted with the aid of a gadolinium-enhanced magnetic resonance imaging scan (MRI), since it can illustrate even tumors that are smaller than 4 mm . In cases where gadolinium-enhanced MRI is not available, a computerized tomography scan can help to detect small acoustic neuromas; nevertheless, this modality is limited to detecting tumors larger than 1 cm .
Brain stem evoked response audiometry (BERA) is a method that monitors cerebral response to auditory stimuli (clicking sounds). The patterns are evaluated using the normal side as a comparative parameter; retrocochlear tumors are suspected when the pattern deviates considerably from the one displayed on the normal side or when there is an interaural delay. Tumors that are small in size cannot be detected via this modality.
Meningiomas cannot be distinguished from acoustic neuromas by means of examinations which evaluate auditory capacity. A gadolinium-enhanced MRI is the optimum choice in order to diagnose a suspected meningioma. Typical characteristics of a meningioma include a hemispherical tumor, with a broad attachment, forming an obtuse angle with the bone and with an eccentric location.