Abstract
Most large cerebello-pontine angle (CPA) tumors usually cause typical abnormal oculomotor findings on vestibular and oculomotor examinations, reflecting brainstem and cerebellar lesions. However, we encountered four patients with large CPA tumor without the typical abnormal neurotological findings and these cases are described in this report. Case 1 : A 63-year-old female. Chief compliment (CC) was double vision. Audiovestibular examinations showed normal findings except for slight nystagmus on ENG. MRI revealed a 4.8 × 4.7 cm lesion of the right CPA. The histopathological diagnosis was CPA meningioma.Case 2 : A 58-year-old female. CC was a tinnitus. Pure tone audiometry indicated right-sided sensorineural hearing loss (SNHL). Results of vestibular examination were normal. MRI revealed a 4.0 × 3.5 cm lesion from the clivus to the CPA that was diagnosed radiologically as a meningioma. Case 3 : A 50-year-old female. CC were tinnitus and head heaviness. Audiovestibular examinations were all unremarkable. MRI revealed a 3.0 × 2.7 cm lesion of the right CPA that was diagnosed as an epidermoid cyst. Case 4 : A 48-year-old female. CC were hearing loss and tinnitus. Audiometric studies indicated right-sided moderate-to-profound SNHL. There were no responses on ABR. Vestibular examinations were unremarkable. MRI revealed a 4.2 × 4.0 cm left-sided CPA mass that was diagnosed at surgery as an acoustic neuroma with cystic changes. Previous study showed that when the CPA tumor is larger than 3 cm, ETT and OKP demonstrate abnormal findings in 70 to 78% of patients, respectively. However, in our cases, despite pronounced compressions of the brainstem and cerebellum by large CPA tumors, vestibular examinations did not reveal any significant findings. These atypical findings might have resulted from the histological characteristics and slow growth of the CPA tomor, in addition to factors related to central vestibular compensation and indivisual differences in susceptibility to the lesions.
