Autonomic dysfunction in Guillain-Barré syndrome and multiple sclerosis.

This review gives an overview of autonomic dysfunction encountered in Guillain-Barré syndrome (GBS) and multiple sclerosis (MS). In GBS, cardiovascular dysregulation is common and may lead to serious bradyarrhythmias that need to be recognised for the early initiation of appropriate therapy. Although standardised autonomic tests were useful for the diagnosis of autonomic failure, they were not able to indicate vagal over-reactivity. In this regard, eyeball pressure testing may correctly identify patients at risk for impending and potentially life-threatening bradyarrhythmias which may easily be administered at the bedside. In MS, cardiovascular autonomic dysfunction is usually of minor clinical importance. However, orthostatic intolerance may be present in approximately 50% of patients and could easily be detected by routine measurements of heart rate and blood pressure during rest and during standing. More subtle alterations may require more sophisticated methods such as autonomic reflex testing or baroreflex stimulation. Several in vitro, animal and clinical studies provide evidence that there are many interactions between the sympathetic nervous system and the immune system giving rise to the hypothesis that autonomic dysfunction in MS may not only be a consequence of the disease, but may in itself affect the course of MS.