Immunohistochemistry Case 1. (A) The vacuolated large cells are negative with NeuN although scattered normal white matter neurons are still labelled. (B) Ankyrin-G antibody (marker of axon initial segment = AIS) shows somatic expression in the vacuolated large cells but no labelling of the AIS apart from scattered puncta in keeping with the nodes of Ranvier. (C) Parvalbumin reveals only weak staining in some of the vacuolated large cells, while calretinin (D) shows strong granular cytoplasmic expression. Scale bars: A = 200 μm; B-D = 50 μm.