Simultaneous EMG-fMRI during startle inhibition in monosymptomatic enuresis--an exploratory study

Area of Science:

• Neuroscience
• Pediatric Neurology
• Sleep Medicine

Background:

• Monosymptomatic enuresis (ME) is increasingly viewed as a central nervous system maturational disorder.
• Reduced prepulse inhibition (PPI) of the startle reflex is observed in children with enuresis.
• The precise neural level (brainstem vs. cortical) of abnormal PPI in enuresis remains unclear.

Purpose of the Study:

• To investigate the cortical and brainstem mechanisms underlying abnormal PPI in children with monosymptomatic enuresis.
• To differentiate between brainstem and cortical inhibitory deficits in ME pathogenesis.
• To explore the role of prefrontal cortex activation in the control of startle reflexes in ME.

Main Methods:

• Simultaneous recording of electromyography (EMG) and functional magnetic resonance imaging (fMRI) in nine children with ME and ten healthy controls.
• Experimental paradigm involving acoustic startle stimulation with and without prepulse inhibition.
• fMRI data analysis using multiple regression and parametric modulation with startle amplitudes.

Main Results:

• No measurable PPI was detected in either group within the MRI scanner.
• Hemodynamic changes in response to startle stimuli were similar across acoustic and prefrontal cortical areas in both groups.
• Healthy children exhibited a stronger correlation between startle amplitude and BOLD signal changes in the anterior cingulate cortex during PPI conditions compared to ME patients, indicating greater prefrontal cortex engagement for inhibition.

Conclusions:

• Methodological challenges may affect PPI recordings within MRI scanners.
• Results suggest that impaired high-level cortical control mechanisms in the prefrontal cortex are implicated in the pathogenesis of monosymptomatic enuresis.
• This highlights the potential role of prefrontal cortex dysfunction in the lack of arousal and inhibited micturition reflex seen in ME.