FIGURE 1.

Operational definition of locus coeruleus (LC) counting frame. Hematoxylin and eosin stain shows the requisite landmarks in a representative rostral pons tissue section at the start of the counting frame. The decussation of 4 (trochlear nerve) was visible in the medullary vellum (MV) and the mesencephalic tract of 5 (trigeminal nerve, me5) was dorsolateral to the pigmented LC neuron field. Identification of these anatomical relationships was used as inclusion criteria in case selection and to normalize the rostrocaudal extent of the LC analyzed by stereology across the cases. Abbreviations: SCP, superior cerebellar peduncle; MLF, medial longitudinal fasciculus; IV, fourth ventricle.