Objective
To investigate autonomic nervous system (ANS) function in mitochondrial disorders (MD).
Background
MD are characterized by a wide range of clinical features, including heart abnormalities and peripheral and central nervous
systems involvement. Rarely autonomic symptoms have been reported.
Methods
22 patients with MD underwent a battery of cardiovascular reflex tests including five tests of parasympathetic function and
four tests of sympathetic function. Power spectral analyses (PSA) of heart rate variability in the supine and upright positions
were also evaluated. Plasma levels of adrenaline, noradrenaline and dopamine were determined in the standing and lying positions.
Results
Only 4/22 patients referred symptoms related to ANS dysfunction. 46% of patients had a definite autonomic damage (i. e. an
autonomic score ≥ 4). 36% showed moderate alterations with an autonomic score in the range 2–3 and 18 % had a normal autonomic
function. MD patients had a significantly (p <0.03) lower increase of adrenaline level after standing.
Conclusions
Our data indicate an autonomic dysfunction in more than 80% of MD patients, even in the absence of a clinically manifested
autonomic involvement. Cardiovascular autonomic investigation might be systematically employed in the characterization of
MD.
Key words mitochondrial encephalomyopathies - autonomic nervous system - cardiovascular reflex tests - plasma catecholamines - power spectral analysis