Cerebellar cortex scheme in pontocerebellar hypoplasia

(A) Control. (B) Pontocerebellar hypoplasia type 2. (C) Pontocerebellar hypoplasia type 4. In (A) normal folial development is shown by normal length and 8 to 15 folial branches for each folium. The confines of 1 folium are indicated by a broken line. The dentate nucleus (DN) is shown beneath the cerebellar cortex as an undulating unbroken line. (B) is an example of pontocerebellar hypoplasia type 2 with short folia and limited branching. Space between the folia is depleted (arrows), and only remnants of lost cortex can be found by microscopy in these places. The dentate nucleus (DN) is broken in small islands, possibly resulting from the loss of segments of overlying cortex by antegrade degeneration. (C) shows the findings in cerebellar cortex and dentate nucleus (DN) in pontocerebellar hypoplasia type 4. The cortex is completely denuded, and a ghost folium can only be discerned by its external shape. The gliotic cortex contains microscopic remnants of neurons. Only minute islands of dentate nucleus (DN) remain. (Contributed by Dr. Peter Barth.)