A 71-year-old man developed
dysarthria and difficulty of swallowing in December 1997. He was diagnosed as having the bulbar type of
amyotrophic lateral sclerosis (ALS). In November 1998, he was admitted to our hospital to undergo treatment for
bulbar palsy and respiratory discomfort. In January 1999, ventilatory support (synchronous intermittent mandatory ventilation) during sleep at night was initiated. Severe progressive
hypotension and
loss of consciousness were observed soon after the start of
artificial respiration, and both symptoms disappeared after
artificial respiration was discontinued. This phenomenon was observed consistently during ventilatory support, while unpleasant stimuli such as bronchoscopy and replacement of the
cannula tube induced severe
hypertension. To clarify the mechanism of underlying these abnormal changes in blood pressure, autonomic function tests were performed while awake during the daytime. Ventilatory support induced a drop in blood pressure accompanied by a decrease in influx speed to the right ventriculum, the latter of which suggested a reduction in venous return. These values returned to the baseline following detachment of the
ventilator. A 60 degrees head-up tilt (HUT) angle and standing from a supine position produced
orthostatic hypotension, the latter of which was accompanied by a compensatory increase in pulse rate. The basal supine plasma
noradrenaline (NA) level was high and the HUT showed a slight elevation of NA. The basal supine plasma
arginine vasopressin (AVP) level was within the normal range, whereas the AVP level did not increase during HUT. Urinary secretion rates of NA and 3-methoxy-4-hydroxy-phenylglycol were elevated. A cold pressor test demonstrated reflex
hypertension. The oculovagal reflex, coefficient of variation of R-R intervals. (CVR-R) and increase in pulse rate in response to
atropine administration were within the normal range. The combination of
midodrine, L-dihydroxyphenylserine (DOPS) and increasing intravascular volume via continuous
intravenous drip infusion relieved the
circulatory collapse during
artificial respiration. In conclusion, the present case of ALS had sympathetic hyperactivity, somatosympathetic reflex and dysregulation of the baroreflex
arc. Degeneration of central autonomic network, including the hypothalamus and the central nucleus of the amygdala, which has been shown in some ALS patients, might underlie the autonomic abnormalities in this patient.