[Autonomic nervous function of vertiginous patients--assessment by spectral analysis of heart rate variability]

Vertigo with dysautonomia and serious allergy: An unusual case of juvenile Ménière's disease

A 13-year-old boy with frequent episodes of vertigo and otologic symptoms was diagnosed with Ménière's disease (MD) but failed to respond to conventional treatment. Allergy testing revealed serious reactions to many allergens, and autonomic tests showed he was dysautonomic. An allergen-restricted diet and treatment of dysautonomia were effective, the boy being free from vertigo within 2 months. This case provides evidence to promote the understanding of MD in children. The authors hypothesize that the autonomic nerves and the immune system can interact, and that such an interaction of dysautonomia and allergy can lead to a serious vertigo episode.

Oxidative stress and heart rate variability in patients with vertigo

Aims

Peripheral vertigo has been reported to result from oxidative stress or autonomic nervous dysfunction. Recently, heart rate variability has been used to evaluate autonomic nervous activity. Parasympathetic nervous dysfunction is associated with peripheral vertigo; however, the relationships between vertigo, oxidative stress, and autonomic nervous activity have not been investigated. The aim of this study was to elucidate the changes in oxidative stress and autonomic nervous activity in vertigo patients compared with healthy volunteers.

Methods

Oxidative stress was assessed by evaluating biological antioxidant potential and reactive oxygen metabolites, and heart rate variability was measured to evaluate autonomic nervous activity. Thirty-four patients who complained of peripheral vertigo and were treated in our emergency department between January and August 2011 were enrolled in study 1. Oxidative stress and heart rate variability were measured and compared with those of healthy volunteers (n = 23). In study 2, oxidative stress in 18 vertigo patients and heart rate variability in 41 vertigo patients were measured between January and August 2012 before and after conventional treatment of vertigo to evaluate the effect of the treatment on oxidative stress and autonomic nervous activity.

Results

Reactive oxygen metabolites were higher in vertigo patients than in healthy volunteers. Parasympathetic nervous activity was lower and the sympathetic/parasympathetic nervous activity ratio (autonomic nervous activity ratio) was higher in vertigo patients than in healthy volunteers. After treatment of vertigo, reactive oxygen metabolites decreased significantly and the autonomic nervous activity ratio became similar to that observed in healthy volunteers.

Conclusions

Bedside monitoring of oxidative stress and heart rate variability may be useful for the diagnosis of vertigo and evaluation of the effect of treatment.

Sympathetic skin responses from postauricular region in Meniere’s disease

OBJECTIVE

To investigate the sympathetic nervous system activity in Meniere's disease (MD) by recording sympathetic skin responses (SSRs) from the postauricular region (PA).

METHODS

Twenty-one patients with definite unilateral MD diagnosis and 12 healthy volunteers were studied by evoking right and left PA-SSRs with electrical stimulation of the left median nerve at the wrist in attack and interval periods of MD. Mean latencies and maximum amplitudes were used in statistical analyses.

RESULTS

In unilateral definite MD patients, the mean latencies were longer and the maximum amplitudes were smaller on the involved ear side than those on the normal ear side (p<0.01 for both amplitude and latency) and than those from the controls (p<0.01 and p<0.05). In three patients, there was no detectable PA-SSR on the involved ear side while there were SSRs on the healthy side. In four patients, the responses were absent bilaterally during the attack period.

CONCLUSIONS

There is a marked asymmetric sympathetic hypofunction in the area of the PA region of the involved ear in MD patients.

SIGNIFICANCE

The PA region is a new site for recording sympathetic skin responses. PA-SSR is a useful tool to investigate sympathetic nervous system function in MD patients.

Response to vestibular stimulation of sympathetic outflow to muscle in humans

The objective of the present study was to determine the effect of vestibular stimulation on the sympathetic outflow to muscle in humans. Fourteen healthy volunteers were studied while in the supine position with electrocardiography, blood pressure monitoring and electro-oculography. The muscle sympathetic nerve activity (MSNA) was recorded directly from the bilateral tibial nerves by using microneurographic double recording technique. Caloric vestibular stimulation was loaded by alternate irrigation with 50 ml of cold (10 degrees C) water and 50 ml of hot (44 degrees C) water into the left and right external meatus. After cold water irrigation, two MSNA response peaks were elicited, respectively, before and after the maximum slow phase velocity (SPV) of nystagmus. The first peak of the MSNA enhancement was caused by non-specific factors because its time course coincided with that in cold pressor test with immersion of the subject's hand in ice/water (4 degrees C). Transient suppression of MSNA after cold water irrigation in the period of maximum SPV of nystagmus was observed by cross correlogram analysis between the SPV of the nystagmus and MSNA. After hot water irrigation, only one MSNA response peak was elicited after the period of strong nystagmus. The second peak of MSNA enhancement evoked by cold irrigation (379.4 +/- 221.8%, with the control value set as 100%, mean +/- SE) was significantly higher than that evoked by hot irrigation (243.0 +/- 14.5%). The degree of MSNA enhancement by either cold (the second peak) or hot stimulation was proportional to the maximum SPV of the nystagmus. There was no significant difference between the MSNA responses ipsilateral to and contralateral to the irrigated side. In conclusion, the caloric vestibular stimulation can influence the bilateral sympathetic outflow to muscle in humans. The degree of MSNA enhancement is proportional to the magnitude of vestibular excitement indicated by maximum slow phase velocity of the nystagmus.