Reduced spontaneous sympathetic nerve activity in multiple sclerosis patients

Area of Science:

• Neurology
• Autonomic Neuroscience
• Cardiovascular Physiology

Background:

• Multiple sclerosis (MS) is a chronic neurological disease affecting the central nervous system.
• Autonomic nervous system dysfunction is increasingly recognized in MS patients.
• Muscle sympathetic nerve activity (MSNA) is a key indicator of sympathetic nervous system function.

Purpose of the Study:

• To investigate spontaneous resting muscle sympathetic nerve activity (MSNA) in relapsing-remitting MS patients.
• To compare MSNA in MS patients receiving disease-modifying therapy (MS-DT) and those on additional symptom-related treatments (MS-DT/ST) against healthy controls (CON).
• To determine if reduced MSNA is associated with autonomic dysfunction in MS.

Main Methods:

• Direct intra-neural measurements of MSNA using microneurography on the peroneal nerve.
• Measurement of plasma norepinephrine levels, arterial blood pressure, and heart rate at rest.
• Comparison between three groups: MS-DT (n=6), MS-DT/ST (n=5), and healthy CON (n=6).

Main Results:

• Significantly lower MSNA burst frequency (bursts/min) in both MS-DT (P=0.027) and MS-DT/ST (P=0.003) groups compared to CON.
• Significantly reduced MSNA burst incidence (bursts/100 heartbeats) in MS-DT (P=0.049) and MS-DT/ST (P=0.004) groups versus CON.
• Lower resting plasma norepinephrine levels observed in both MS-DT (P=0.039) and MS-DT/ST (P=0.021) groups compared to CON.

Conclusions:

• Spontaneous resting MSNA is significantly reduced in relapsing-remitting MS patients, irrespective of additional symptom-modifying medications.
• Reduced MSNA and plasma norepinephrine levels suggest impaired sympathetic nervous system function in MS.
• This autonomic dysfunction may play a role in the cardiovascular complications associated with MS.