Ultrastructural investigations of peripheral nerves in neuronal ceroid-lipofuscinoses (NCL).

Specimens of brachial plexus, sural nerve and two cranial nerves of one patient with Jansky-Bielschowsky type and 3 patients with the Spielmeyer-Sjögren type of NCL were studied by electron microscopy. Significant light microscopic changes were absent in all specimens. Ultrastructurally, curvilinear and/or fingerprint inclusions were present in each case, located chiefly in Schwann cells. These diagnostic findings were, however, overshadowed by masses of lamellar pi-granule-like cytosomes, usually not mixed with curvilinear or finger-print profiles in the juvenile cases and only rarely associated with curvilinear profiles in the late infantile case. Since secondary changes of axons and myelin sheaths were mild, these lamellar cytosomes might indicate chronic damage to Schwann cells, perhaps by "wear and tear" as seen in aging as well as NCL. On account of the abundance of pi-granules in NCL, peripheral nerve biopsy appears less suitable for confirming this diagnosis than biopsy of skin, striated muscle and rectal tissue.