Sensorimotor integration in patients with parkinsonian type multisystem atrophy

Area of Science:

• Neuroscience
• Neurology
• Motor Control

Background:

• Sensorimotor integration is crucial for precise motor task execution.
• Multiple system atrophy with parkinsonian features (MSAp) patients may display abnormal central nervous system excitability to somatosensory inputs.
• Clinical signs like action myoclonus and enhanced reflexes suggest sensorimotor processing deficits in MSAp.

Purpose of the Study:

• To investigate the specific sites of sensorimotor integration dysfunction in MSAp.
• To examine the inhibitory effects of cutaneous afferent volleys on motor evoked potentials (MEP) and blink reflexes in MSAp patients.

Main Methods:

• 10 MSAp patients and 10 healthy controls were studied.
• Electrical digital nerve stimuli conditioned motor evoked potentials (MEP) in hand muscles via transcranial magnetic stimulation.
• Electrical digital nerve stimuli also conditioned blink reflex R2 responses in orbicularis oculi muscles via supraorbital nerve stimulation.
• Inter-stimulus intervals (ISI) were 20-50 ms for MEP and 90-110 ms for blink reflex.

Main Results:

• Healthy volunteers showed significant MEP inhibition (mean 32% of baseline at 35 ms ISI) and blink reflex inhibition (mean 12% of baseline at 100 ms ISI).
• MSAp patients exhibited abnormally reduced inhibitory effects on MEP (in 8/10 patients) and blink reflex (in 7/10 patients).
• Significant group differences in conditioned MEP and blink reflex sizes were observed between MSAp patients and controls.

Conclusions:

• Sensorimotor integration is demonstrably abnormal in multiple system atrophy with parkinsonian features (MSAp).
• Dysfunction occurs at multiple central nervous system levels, including the sensorimotor cortex and brainstem reticular formation.
• These findings highlight the widespread impact of MSAp on sensorimotor processing and motor control.