Co‐localization of Bunina bodies and TDP‐43 inclusions in lower motor neurons in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized by motor neuron involvement with Bunina bodies (BBs) and transactivation response DNA protein 43 (TDP-43) inclusions. We examined the spinal cord (n = 20), hypoglossal nucleus (n = 6) and facial nucleus (n = 5) from ALS patients to elucidate the relationship between BBs and TDP-43 inclusions. BBs were found in the anterior horn in 16 of 20 cases, in the hypoglossal nucleus in all six cases and in the facial nucleus in four out of five cases. TDP-43 inclusions were found in each region of all the cases. Co-localization of BBs and TDP-43 inclusions was found in 15.2% of total neurons in the anterior horn, 29.2% in the hypoglossal nucleus and 17.3% in the facial nucleus. The frequency of TDP-43 inclusions was significantly higher in neurons with BBs than in those without in each region. Ultrastructurally, TDP-43-positive filamentous structures were intermingled with BBs. These findings suggest that there is a close relationship in the occurrence between BBs and TDP-43 inclusions.