[Immunohistochemical study on temporal bone of autopsy cases with Mycobacterium leprae infection]

Three temporal bones were obtained en bloc from autopsy cases with lepromatous leprosy from the middle cranial fossa side after removing the brain. After fixation with 10% formalin followed by sufficient decalcification, the specimens were embedded in paraffin en bloc and cut serially to stain every 10th section with hematoxylin and eosin (H&E) for anatomical orientation. An immunohistochemical study with anti-neurofilament, anti-MBP (myelin basic protein), anti-BCG (Bacillus Calmette-Gue'rin) and anti-PGL (Mycobacterium leprae-specific antiphenolic glycolipid-I) antibodies were performed to vestibular, cochlear and facial nerves, respectively, on the basis of anatomical orientation of the adjacent H&E sections. In one of three cases, positive staining by anti-PGL antibodies was recognized only in the facial nerve both in its internal auditory meatal and tympanic portions. However, even in this case, no neural damage was observed either by anti-neurofilament nor anti-MBP stainings. This finding supports the possibility of central neural infection by Mycobacterium leprae.