Ear, Nose, And Throat Disorders Chapter 85. As the tumor grows larger, it projects from the internal auditory meatus into the cerebellopontine angle and begins to compress the cerebellum and brain stem. The 5th cranial nerve and later the 7th are affected. Symptoms, Signs, and Diagnosis Hearing loss and tinnitus are early symptoms. Although the patient complains of dizziness and unsteadiness, true vertigo is not usually present.
Recruitment is absent, and tone decay is marked.
Acoustic reflex decay, the absence of waveforms, and increased latency of the 5th waveform in auditory brain stem response testing are further evidence of a neural lesion. Early diagnosis is based on the audiologic assessment, particularly auditory brain stem response and MRI with gadolinium enhancement. Treatment Small tumors may be removed with microsurgical techniques that preserve the facial nerve, using a middle cranial fossa route to preserve the remaining hearing or a translabyrinthine route if no useful hearing remains. Large tumors are removed by a combined translabyrinthine and suboccipital approach. Alternatively, radiation therapy or gamma knife radiosurgery may be used.