Unilateral hypertrophy of the medullary pyramid apparently developed subsequent to the occurrence of contralateral cerebral damage in the antenatal or perinatal period. Quantitative analysis of this material demonstrates a pyramidal size which is greater than those of reported cases and also a marked increase in the number of both large and small axons, which is at variance with earlier reports in which only an increase in larger fibers was found. The early age of onset may be responsible for this difference in fiber distribution. It is suggested that failure of the damaged pyramid to develop causes a hypertrophic response to occur in the contralateral uncrossed pyramidal tract.
Scales DA, Collins GH. Cerebral Degeneration With Hypertrophy of the Contralateral Pyramid. Arch Neurol. 1972;26(2):186–190. doi:10.1001/archneur.1972.00490080104013
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