Fig. 7.

Non-connected or connected explanations for variable gradient. Relative quantity of Lewy pathology could be quite variable with predominance at the dorsal motor nucleus (dmX, a, d), the locus coeruleus (LC, b, e) or the substantia nigra (SN, c, f). Putative directions of intraneuronal spread for αS inclusion pathology are indicated with orange or red arrows. Expected directions of possible transneuronal spread of αS inclusion pathology along interrupted lines are indicated with gray arrows and arrowheads. Either dmX (d), LC (e) or SN (f) is assumed to be initially involved and subsequently spread of αS inclusion pathology through interneuronal connections. Both intra- and inter-neuronal directions are reversed according to the primary site of involvement (d–f). See text for details