Deafness in Cockayne's syndrome: morphological, morphometric, and quantitative study of the auditory pathway.

The auditory pathway of a 17-year-old deaf patient with Cockayne's syndrome was examined histologically. The cochlea showed marked atrophy of the spiral ganglion and attenuation of the cochlear division of the eighth cranial nerve. By means of the Computer Image Analyzer, the total number of neurons in the ventral cochlear nucleus was found to be reduced from 30,440 to 18,821. The mean diameter of the neurons in the ventral cochlear nucleus, medial dorsal olivary nucleus, and inferior colliculus was smaller than in a control patient, whereas in the medial geniculate nucleus and anterior transverse gyrus of Heschl, the neuronal size approximated the norm. The changes in the first three auditory relay nuclei were considered to represent transsynaptic atrophy caused by degeneration of the spiral ganglion and, possibly, the cochlear neuroepithelium. This histological report verifies that deafness in Cockayne's syndrome is largely sensorineural and that degeneration of spiral ganglion in humans can lead to a chain of trans-synaptic degeneration in the ventral cochlear nucleus, medial dorsal olivary nucleus, and inferior colliculus.