Contributed by Klaus Bumm 1, Abbas Agaimy 2, Gerald Niedobitek 2, Heinrich Iro 1, Helmut Steinhart 1
1 Department of Otorhinolaryngology, University of Erlangen-Nuremberg, Germany
2 Department of Pathology, University of Erlangen-Nuremberg, Germany
CLINICAL HISTORY AND IMAGING STUDIES
A 47-year-old male patient presented with a fluctuating hearing impairment in his left ear over the past 5 years. Tinnitus or vertigo was not observed. Audiometric analysis showed an inner ear deficit of 50 dB between 1500 and 6000 kHz on the left side. Hearing in the right ear was normal. The facial nerve was clinically and by means of electrophysiological testing without pathological findings. BEAP (brainstem evoked auditory potentials) revealed a latency increase between J1 and J3 up to 2.5 ms for the left side, whereas only 2.3 ms on the right side. MRI (magnetic resonance imaging) scanning showed a tumor of the cerebellopontine angle in the left inner auditory canal (IAC) of 1.2 x 0.7 x 0.9 cm in size (Figure 1). After application of contrast media, the tumor showed clear signal enhancement. The tumor was entirely removed by a transtemporal approach to the IAC. Surgical exploration found the cochlear nerve embedded in a tumorous mass, whereas the vestibular and the facial nerve were normal (Figure 2, vestibular nerve arrow A and cochlear nerve with tumor arrow B). Nerve and tumor (Figure 3) were removed and sent to histopathological examination. The patient lost his hearing after the operation due to the removal of the cochlear nerve, whereas a regular postoperative vestibular function was observed. The postoperative course as well as the 5-year follow-up examination was unremarkable and control MRI scanning showed no recurrence.
Histopathological examination revealed a tumor composed of loosely packed irregular nerve fibres embedded within loose connective tissue (Figure 4, H&E-stain, x 100). Mature adipose tissue elements and numerous capillary- to medium-sized thin-walled vascular channels were diffusely dispersed between nerve fibres. In addition, isolated adipocytes were seen within the endoneurium of some nerve fibres, but no skeletal muscle cells, ganglionic cells, glial elements or other tissue derivatives were seen. Also, hemosiderin pigment, scarring or inflammatory cells as would be anticipated in amputation (traumatic) neuroma were not observed. Immunohistochemistry revealed a strong expression of protein S100 and neurofilament protein in the nerve axons and Schwann cells (Figure. 5, x 100). An intact perineurial sheath was highlighted by reactivity for epithelial membrane antigen (Figure 6, EMA).