The nucleus raphe interpositus in the Steele-Richardson-Olszewski syndrome (progressive supranuclear palsy)

As the integrity of the omnipause neurons located in the nucleus raphe interpositus is a prerequisite of normal ocular motility, cell and neurofibrillary tangle densities were determined in 13 Steele-Richardson-Olszewski syndrome (SROS) cases [eight with supranuclear gaze palsy (SGP) and five without] and six controls. Compared with normal controls, cases with SGP were associated with approximately 50% nerve cell loss (P < 0.001), whereas data from cases without SGP were not significantly different (P = 0.18). Furthermore, cases with SGP had lower neuronal cell (P = 0.016) and higher neurofibrillary tangle densities than those without (P = 0.011). These results indicate that the involvement of the omnipause neurons, which are glycinergic, contributes to abnormal eye motility in SROS. Involvement of these glycinergic nerve cells suggests that the degeneration of brainstem structures in SROS affects neurochemically diverse systems; so far other brainstem nuclei concerned with eye motility; and known to be affected in SROS, are cholinergic. The results of this study provide evidence that clinically distinct subgroups of SROS may be differentiated histologically when adequate morphometric techniques are applied.