Head extension and age-dependent posturographic instability in normal subjects.

We have investigated the role of head extension in posturographic testing of normal subjects. We especially wished to determine the number of falls that occurred in the "normal" elderly so as to distinguish them from elderly patients with abnormal neurologic and vestibular patterns. We tested 144 normal subjects ages 22 to 85, the majority older than 60 years, with the NeuroCom Equitest sensory posturography protocol: first with their heads erect and then with their heads extended 55 degrees. None of our subjects younger than age 59 experienced a fall during sensory posturography tests with their heads erect. However, 35 of the 101 older subjects exhibited a total of 79 falls during these same tests. When the tests were repeated with the head extended 55 degrees, the number of falls for the whole group increased from 79 to 171. Where only 24% of all the subjects fell with head erect, 52% fell with head extended. The increase was especially notable among the elderly. Head extension increases the difficulty of performing certain posturography tests and has been useful in uncovering compensated deficits in equilibrium in young and middle-aged patients. However, because head extension significantly increases falls among normal elderly subjects, this does not seem to be an effective tool to determine abnormality in this age group.