Neuropathology in cerebral lactic acidosis.

The neuropathology in two young infants with cerebral lactic acidosis is presented. Both cases showed microcephaly, ventricular dilatation, absent corpus callosum, absent or extremely hypoplastic pyramids, heterotopic inferior olives, focal neuroglial overgrowth into meninges, focal cystic change with gliosis and recent degenerative changes in the germinal matrix. The cerebellum, basal ganglia, Ammon's horn, inferior colliculi and layering of the cortex were well preserved. The features suggest a continuous damage with very old, relatively old and recent lesions. This striking combination of abnormalities should raise the possibility of a disturbance of lactate/pyruvate metabolism.

Observations of the pineal region of non-eutherian mammals.

A survey has been made of the pineal region of the brain of 11 species of marsupials belonging to 5 families and a species from both families of monotremes. The results show that the pineal body of non-eutherian mammals, although well-defined in all species, has a very varied morphology. Three types of pineal recess occur: (i) a pineal recess in sensu stricto, (ii) an intercommissural pineal recess, and (iii) an infrapineal recess. The existence of nerve fibres which pass through the pineal body and form a spatial link between the habenular and posterior commissures, has been demonstrated in marsupials and monotremes. It is also likely that these animals as well as eutherian mammals possess a nervus conarii. Nerve cells are not a constant feature of the non-eutherian pineal body. The subcommissural organ (SCO) is present in all species. It does not exhibit the same degree of morphological variation as the pineal body. Horizontal sections available for 4 species within 3 families of marsupials show it to be composed of a median portion jointed to bilateral protuberances. Large nerve cells occur within the SCO in all marsupial species; they are absent from the monotreme SCO. Tentatively, the relationship of these neurons to the SCO is considered to be merely one of association. The importance of an extended comparative study of this region in non-eutherian mammals in order to add insight into its phylogeny and function is emphasized.