Vestibular schwannoma diagnosis
In the 1980s tests for cerebrospinal fluid protein, vestibular testing, and arteriography have been supplanted by modern audiometry with acoustic reflex testing, brain stem evoked responses, and computed tomography (CT). The various types of plain radiography are confirmed as an extremely useful screening modality. CT is insufficiently sensitive to serve as a primary screening procedure, but is a valuable confirmatory test 1).
Vestibular schwannoma (VS) usually present the widening of internal auditory canal (IAC), and these bony changes are typically limited to IAC, not extend to temporal bone 2).
Audiologic evaluation
Evaluation—should include pure tone audiometry and speech discrimination test (50/50 is considered serviceable hearing with 50 Db pure tone hearing and 50% speech discrimination).
The most common chief complaint in patients diagnosed with CPA tumors was asymmetrical hearing loss, with most frequent accompanying symptoms being tinnitus in patients with vestibular schwannoma (VS) and dizziness in those with other types of CPA tumor. The most frequent patterns of hearing loss were the descending type in patients with VS and the flat type in patients with non-VS tumors (p < 0.05). Pure tone thresholds tended to increase more in patients with VS than non-VS tumors according to tumor size, and pure tone averages were significantly higher in patients with VS than non-VS tumors of 11-25 mm in size (p < 0.05) 3).
Neurological examination
Trigeminal nerve dysfunction
Trigeminal nerve, and facial nerve dysfunction are common preoperative findings.
Examination may show hypoesthesia in the most superficial part of the external auditory canal. In a population of 46 patients tested by a Schirmer test before radiosurgery, Tamura et al found that 41% of patients experienced some lacrimal deficit on the side of the tumor. more common at the time of presentation than facial weakness (about 10% of patients). A decrease in the corneal reflex generally occurs earlier and more commonly than documented facial hypoesthesia. Even though approximately 50–70% of individuals with large tumors have facial hypoesthesia on neurological examination, they are often unaware of it, and it is rarely the presenting symptom.
Facial nerve dysfunction
The HBS produced comparable results between different observers in patients with normal or only mildly impaired facial nerve function. Interobserver variability increased depending on the severity of facial nerve paresis. The results suggest that the HBS does not promote uniformity of reporting and comparison of outcomes in patients with moderate or severe facial nerve paresis 4).