Adult leptomeningeal cerebellar heterotopia in contact with the posterior inferior cerebellar artery

A leptomeningeal mass was encountered during microdissection of a 63-year-old male cadaver, located dorsal to the left side of the medulla oblongata. The structure was compressing the posterior inferior cerebellar artery (PICA) and was composed of cerebellar-like tissue. Immunohistochemistry for S100 protein, glial fibrillary acidic protein and neurofilaments (NF, the triplet proteins and the 200 kD antibody) on paraffin-embedded samples confirmed the cerebellar heterotopion. Abundant Lewy-like degenerative bodies were also identified within the heterotopion; they were positive for the NF triplet and negative for the 200 kD neurofilaments. Purkinje cells were rare. This is the first evidence of a leptomeningeal cerebellar heterotopia in contact with PICA in adult. Such subtentorial heterotopias, even if rare, should be searched for during clinical, paraclinical and surgical explorations of the posterior fossa.