Implication of altered autonomic control for orthostatic tolerance in SCI

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Rehabilitation Medicine

Background:

• The autonomic nervous system (ANS) integrates sympathetic and parasympathetic outputs for cardiovascular control during daily activities like orthostatic positioning.
• Sympathetic innervation of the cardiovascular system has segmental origins in the spinal cord (T1-T5 for upper body/heart, T5-L2 for lower body/splanchnic vasculature).
• The parasympathetic nervous system primarily influences the heart's SA node via the vagus nerve (cranial nerve X).

Purpose of the Study:

• To review the mechanisms underlying orthostatic hypotension (OH) and orthostatic intolerance (OI) following spinal cord injury (SCI).
• To discuss the prevalence and consequences of OH and OI in individuals with SCI.
• To explore potential treatment options for OH and OI in the SCI population.

Main Methods:

• This is a review article, synthesizing existing knowledge on the topic.
• The review discusses the neuroanatomical basis of cardiovascular control and its disruption in SCI.
• It examines clinical manifestations and potential therapeutic strategies.

Main Results:

• Spinal cord injury (SCI), particularly lesions above T6, impairs sympathetic cardiovascular control, leading to a high incidence of orthostatic hypotension (OH) and orthostatic intolerance (OI).
• Symptomatic OH can cause cerebral hypoperfusion, presenting with dizziness, lightheadedness, and syncope.
• Many individuals with SCI experience asymptomatic or minimally symptomatic OH/hypotension, potentially delaying clinical concern.

Conclusions:

• Understanding the segmental differences in sympathetic innervation is crucial for predicting cardiovascular control deficits after SCI.
• OH and OI are significant complications in the SCI population, impacting quality of life and requiring further investigation.
• Further research is needed to elucidate the full spectrum of OH/OI in SCI and to develop effective management strategies.