[Development of vestibular system in children with/without attention deficit hyperactivity disorder]

To investigate the development of vestibular system function in 7 to 14 years old normal boys and the ADHD boys;

The present study involved two groups of subjects: 148 ADHD boys (age range 7 years to 14 years) diagnosed with DSM-IV diagnostic criteria and 148 normal boys with the same age. Each group was divided into 4 clusters according to two years gap. All subjects were tested for the vestibular system function by the Vestibular Function Test System 2000/ ENG-V600 with the eye movement index.

From 7 to 14 years, the development of vestibular system function in normal boys had the characters as the description below. The optokinetic system function exhibited more development from seven years in the normal group. From 7 to 10 years, the time delay of saccade and anti-saccade in normal boys was significantly shorter(In the normal controls , the delay time of left saccade was 149+/-66 ms in 7-8 years old boys, 108+/-64 ms in 9-10 years old boys, 117+/-72 ms in 9-10 years old boys, the delay time of left anti-saccade was 178+/-127 ms in 7-8 years old boys, 101+/-88 ms in 9-10 years old boys,P<0.05). The velocity of saccade was faster significantly(right saccade velocity was 138+/-11 degrees /s in 7-8 years old boys, 147+/-15 degrees /s in 9-10 years old boys, P<0.05). From 9 to 12 years, the velocity of anti-saccade in normal boys was significantly faster(left anti-saccade velocity was 155+/-26 degrees /s in 9-10 years old boys, 172+/-34 degrees /s in 11-12 years old P<0.05 and their accuracy of saccade enhanced(left saccade accuracy was 0.88 in 9-10 years old boys, 0.90 in 11-12 years old boys,P<0.05) . From 13 to 14 years, time delay was much shorter than before(the delay time of left saccade was 101+/-62 ms in 11-12 years old boys, 76+/-63 ms in 13-14 years old boys, P<0.05). But in ADHD group, there was the different development tendency. Their time delay shorten only in 7 to 10 years old boys(In ADHD group, the delay time of left saccade was 179.03+/-66.69 ms in 7-8 years old boys, 138+/-76 ms in 9-10 years old boys,P<0.05). And at other age, the vestibular function of ADHD boys appeared to have no significant change. The velocity of optokinetic nystagmus in 7 to 14 years old ADHD boys was slower than that of the same age in normal controls(the velocity of OKN slow phase was 138.07 degrees /s in 7-8 years old boys, 40.24 degrees /s in 9-10 years old boys and 41.30 degrees /s in 13-14 years old boys ; the velocity of OKN fast phase was 226.88 degrees /s in 11-12 years old boys. In the same conditions, the velocity of OKN slow phase was 179.03 degrees /s in 7- 8 years old boys, 43.86 degrees /s in 9-10 years old boys and 47.32 degrees /s in 13-14 years old boys; the velocity of OKN fast phase was 262.92 degrees /s in 11-12 years old boys, P<0.05). The ratio of max slow phase velocity of VVOR/OKN+VOR of 7-8 years old and 11-12 years old ADHD boys were significantly larger than those of the normal controls(left VVOR/OKN+VOR of ADHD group was 0.73 in 7-8 years old, in normal controls this ratio was 0.66; in ADHD group of 11- 12 years old, left ratio was 0.80, in normal controls this ratio was 0.71. P<0.05) .

Saccade, antisaccade and visual-vestibular interaction system are developing in 7 to 14 years old normal boys, while the optokinetic nystagmus is stable. Vestibuloocular system is stable also. The development of optokinetic system and visual-vestibular interaction system in 7 to 14 years old ADHD boys delays that of the same age normal boys. Most significant differences between ADHD boys and normal boys can be seen in 11 to 12 years old boys.