Factors influencing dementia and epilepsy in Huntington's disease of early onset.

A sample of young patients with Huntington's disease, ascertained from case material reported in the literature, was examined to determine whether muscular rigidity or age at onset of the disorder is the major factor in giving rise to early dementia and epilepsy. Because of correlation between explanatory variables, adjustment for their effects was made in calculating the strength of associations. The risk of incurring dementia early was found to be over twice as great for rigid patients than for those without the sign. Onset age was independently involved with rigidity in this relationship. When the effect of muscular rigidity was adjusted for sex and onset age, virtually no influence on the occurrence of epilepsy was detected. Onset age, on the other hand, was strongly associated with the likelihood of epileptic attack.