Abstract
A case is reported of a 52 year old man who sustained a head injury and survived for three years and two months in coma. He was subsequently shown to have severe brain stem damage, with a bilateral lesion of the central tegmental tract and bilateral hypertrophic olivary degeneration, associated with a widespread loss of Purkinje cells in the cerebellar cortex. Hypertrophic olivary degeneration is considered to be a trans-synaptic change associated with a lesion of the central tegmental tract, which in this case was thought to be due to primary shearing injury of the brain stem involving the superior cerebellar peduncles. It is suggested that, as a consequence of long survival, Purkinje cell degeneration represents further trans-synaptic changes, the result of neuronal degeneration in the hypertrophied inferior olivary nuclei and in the dentate nuclei. A chain or `circuit' of degenerated neurones is thereby produced.