Abnormal control of orbicularis oculi reflex excitability in multiple sclerosis

Area of Science:

• Neuroscience
• Neurology
• Neurophysiology

Background:

• Multiple sclerosis (MS) can cause abnormal brainstem reflex circuit excitability due to impaired descending control.
• This study investigates blink reflex responses to identify abnormalities in MS patients.

Purpose of the Study:

• To determine if asymmetries in blink reflex response size indicate abnormal excitability in MS.
• To correlate neurophysiological findings with MRI-assessed brain lesion load.

Main Methods:

• Blink reflex responses were analyzed in 20 MS patients and 12 healthy controls.
• Latency abnormalities (AbLat) and excitability abnormalities (AbEx) were identified.
• Response size, excitability recovery (BRER), and prepulse inhibition (BRIP) were assessed and correlated with MRI lesion data.

Main Results:

• Abnormal excitability (AbEx) was linked to asymmetric hemispheral lesions and lower brainstem lesion load compared to latency abnormalities (AbLat).
• AbEx patients showed milder disability (EDSS=1.5) than AbLat patients (EDSS=2.75).
• Asymmetric abnormalities in response size, BRER, and BRIP were observed in AbEx patients.

Conclusions:

• Asymmetric blink reflex excitability abnormalities in MS are associated with less disability and lower tissue loss than latency abnormalities.
• Testing blink reflex excitability may serve as a reliable neurophysiological index for early MS dysfunction.