Comparison of phosphorylated TDP-43-positive inclusions in oculomotor neurons in patients with non-ALS and ALS disorders

TDP-43 has been identified as a major component of the pathological inclusions in most forms of frontotemporal lobar degeneration with ubiquitin-positive inclusions and in amyotrophic lateral sclerosis (ALS). In the present study, paraffin sections of the midbrain in 112 patients with various non-ALS disorders and 27 patients with sporadic ALS were immunostained with antibody against phosphorylated TDP-43 (pTDP-43). pTDP-43-positive inclusions in oculomotor neurons were detected in 18 of 112 patients with non-ALS disorders (16.1%). The appearance of the inclusions showed fine filamentous structures rather than the skein-like inclusions seen in the anterior horn cells of ALS spinal cords. The incidence was increased in the age range of 80-89 years old (10/37 cases; 27.0%), in which 6 of 10 cases demonstrated AD pathology in the temporal lobes. Twenty-seven ALS patients were examined and the findings were compared with those of non-ALS patients. There were 13 cases demonstrating pTDP-43-positive inclusions (48.1%) which showed stronger immunoreactivities in ALS cases. This is the first report demonstrating fine filamentous pTDP-43-positive inclusions in oculomotor neurons in non-ALS disorders. Although the mechanisms underlying pTDP-43 in oculomotor neurons are currently unknown, its detection is of interest, and the expression may occur not only in ALS but also during the aging process.