Tangled Masses of Central Axons Central Axonomas) in the Brain Stem

Abstract

Eight additional cases of tangled masses of unmyelinated fine axons occurring in the brain stem in association with cystic infarcts or traumatic cysts are described. Because they are solely composed of bare axons and because of their consistent association with old, destructive lesions, they are called axonomas in lieu of the previous designation as non-myelinated neuromas. Axonomas were located at the border of the associated lesions exclusively in or near the central tegmental tract of the midbrain, pons or medulla. Their occurrence in the restricted region is considered as the reason for their rarity and for the failure to observe them in the past. The discrete, compact, mass formation, the occurrence of a large number in groups, the exclusive occurrence in specific regions of the central nervous system (CNS), and the consistent association with old axonal injury are presented as circumstantial evidence that axonomas represent regenerative growths of central axons. Based on the restricted site of predilection, it is inferred that axonomas originate from a special group or groups of CNS neurons which may have an exceptionally high capacity to regenerate. In other words, certain central neurons in man are not only capable of abundant regenerative sprouting but also are able to sustain the newly formed sprouts in the form of axonomas for years or perhaps permanently, but the specific neurons are not yet identified.