Acta Neuropathol (2008) 116:119–124 led to variable distension of the perikarya and axon hill- ocks which, on occasion, were remarkably distended. The storage frequently led to neuronal regression and loss (see below). There were strong signals for SCMAS and for cathepsin D. The deposits displayed uniform curvilinear ultrastructure with variable admixture of dense homoge- nous droplet like deposits; no Wngerprints were observed. Infrequently, the neuronal storage lysosomes displayed fusion with transformation of the stored material, a process which has been shown to exist, to variable degrees in other NCL types and is characterized by altered staining, absence of detectable SCMAS and electron densiWcation [4, 8]. It was accompanied by either reduced or absent cathepsin D signals. The process was expressed in some of the nigral neurons but to a low degree and was rarely seen in locations typical of the classical late infantile CLN2 variants [4]. Storage distribution Neuronal storage in the brain neocortex was uniform and was expressed in layers II, III, IV and VI, layer I being unaVected while layer V was severely depleted of neurons, severely astrogliosed and inWltrated by CD68 positive microglial phagocytes containing autoXuorescent storage granules (Fig. 1a). Layer V was also somewhat spongy in appearance. Other cortical layers displayed a lesser degree of astrogliosis. Neuronal storage in the entorhinal cortex had a similar distribution with moderate neuronal depletion in layers II and IV, and was expressed in all transitional Welds of the hippocampal formation (parasubiculum, praesubiculum), as well as in the subiculum, although, without signiWcant neuronal reduction. In the hippocampal Welds CA1–CA4, neuronal storage was restricted to the stratum pyramidale with decreasing order from CA1 to CA4. In both CA3 and CA4 Welds it was restricted to 121 isolated neurons. There were discrete storage granules in the dentate gyrus neurons. The cerebellar cortex was depleted of the majority of its neurons in all layers and massively astrogliosed (Fig. 1b). There were only exceptional persisting Purkinje cells, which were loaded with storage granules. The dentate nucleus exhibited neuronal storage and only mild neuronal loss. Neurons in the thalamus and in the basal ganglia dis- played variable degrees of storage with questionable signs of regression and loss. Large striatal neurons displayed bor- derline storage (borderline autoXuorescence and borderline SCMAS signal) and diVered from the surrounding small and medium-sized neurons (Fig. 2a, b). In other parts of the CNS, storage was present without signiWcant regression. There were neurons in the oblongata and brain stem that were either without detectable or with only borderline focal perikaryal storage especially on the Xoor of the 4th ventri- cle (Fig. 2c, d). In the spinal medulla, maximal storage was found in the neurons of the posterior columns, while being virtually absent from the bulk of the anterior horn neurons (Fig. 2e, f). Myelin staining was not signiWcantly reduced. The ependyma displayed discrete storage. No autoXuores- cent granules were detectable in the choroid plexus epithe- lium. Signs of active demyelinization were absent. CD68 positive microglial phagocytes containing autoXuorescent SCMAS positive granules were exceptional and concen- trated in areas of neuronal degeneration. Occasional peri- vascular macrophages harbored lipofuscin with a nonspeciWc ultrastructure. Extraneuronal storage was characterized by autoXuores- cent and SCMAS positive granules. It was observed, in decreasing order, in cardiocytes, kidney tubules, smooth muscle cells of visceral arteries, adipocytes, hepatocytes, spleen (macrophages and sinusoidal endothelium), and in vascular endothelium. Comparisons with classical CLN2 showed a major diVerence in hepatocytes, which displayed Fig. 1 a ParaYn section of cerebral cortex showing storage conWned to layers II, III, IV, and VI. Layer V is almost totally depleted of stor- age neurons. SCMAS staining (bar 200 m). Insert shows detail of perikaryal and axon hillock distension (bar 50 m). b Cerebellar cortex with extreme depopulation of the cortical neuronal layers and pro- nounced gliosis in the Bergmann astrocytic layer. H&E (bar 200 m) 123