An event-related functional MRI study on working memory impairment in children with primary nocturnal enuresis

Abstract

Objective To assess the working memory and explore the activation of brain areas for children with primary nocturnal enuresis (PNE) with fMRI scan. Methods Twenty three right-handed children with PNE and 20 age-matched right-handed healthy children as the controls were recruited.Intelligence tests were performed by means of Wechsler Young Children Scales of Intelligence (C-WISC) in children with PNE and normal controls. The full intelligence quotient (FIQ), verbal IQ (VIQ),performances IQ (PIQ) and the memory/caution (M/C) factor of PNE children and the controls were measured. After Intelligence tests, an enent-related fMRI scan was performed using the categorial N-Back working memory task. Percent of correct responses (PCR) and mean reaction time to correct response (mRT) were recorded and analyzed by the student t test. The fMRI data were analyzed using Statistical Parametric Mapping 2 (SPM2), the differences in activation were compared between two groups. Results The data of 15 PNE children and 15 healthy children were evaluated. The FIQ, VIQ and PIQ in PNE group were in a normal range and no statistical significance with the control group ( P ＞ 0. 05). M/C factor in the PNE group(90.4 ±10.2)was significantly lower than that in the control group (99. 6 ± 11.9) (t =2. 260,P ＜ 0. 05). In the N-Back test, PNE children had significantly less PCR [(72.7±6.3 ) % vs. ( 86. 3 ±6. 7) %, t = 5. 727,P ＜ 0. 01] and longer mRT [ (625. 8 ± 72.5) ms vs. (534. 8 ± 63. 3 ) ms, t = 3. 684,P ＜ 0.01] than the healthy controls. The activation regions of PNE patients and healthy children were mainly in the dorsal right frontal lobe, right parietal lobe, left temporal lobe gyrus fusiformis and bilateral cerebellum posterior lobe. The activation level in left posterior cerebellar lobe in PNE children was significant lower than that in healthy controls (P＜0.01). Conclusion The children with PNE have deficits in working memory which might be associated with the dysfunction of the left cerebellum. Key words: Nocturnal enuresis; Magnetic resonance imaging; Memory disorders