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The right insular cortex infarction: a critical factor for mortality?

Sirs, We read the interesting clinical report by Hanne et al. [1], who found a relationship between right insular cortex (Ic) infarction and mortality after ischaemic stroke. However, data on cause of death were not collected prospectively in the underlying database. Several studies have shown that the cardiovascular system is regulated by a central cortical autonomic network consisting of the Ic, anterior cingulate gyrus and amygdala [2]. Because the Ic is located in the region of the middle cerebral arteries, its structure tends to be exposed to a higher risk of stroke [2]. Many studies have shown the relationship between Ic infarction and autonomic nervous system abnormality. Tokgozoglu et al. [3] evaluated the differential impacts of stroke localization on heart rate variability measures in 62 patients with ischaemic stroke and 62 controls matched for age and gender. Stroke patients had significantly decreased low frequency (LF), high frequency (HF) and standard deviation of all normal-to-normal (SDNN) R wave to R wave (RR) intervals. Specifically, patients with right Ic lesion had significantly lower values of LF, HF and SDNN than those with other localizations [3]. In addition, Colivicchi et al. [4] performed 24-h Holter electrocardiogram monitoring in 103 consecutive patients with first-ever acute ischaemic stroke. Compared with all other stroke patients, patients with right Ic involvement had significantly lower values of SDNN, standard deviation of the root mean square of differences of adjacent normal-to-normal RR intervals, and higher LF/HF. Right Ic lesion was associated with more premature ventricular contractions and premature supraventricular contractions than left-sided ischaemia and with more non-sustained ventricular tachycardia and supraventricular tachyarrhythmias than all other localizations [4]. During the 1-year follow-up in 208 consecutive patients with first-ever acute ischaemic stroke, right Ic lesion, lower SDNN values and the presence of non-sustained ventricular tachycardia were significant predictors for mortality at 1 year [5]. These results suggest that ischaemia including the right Ic is associated with decreased autonomic nervous system activity. And right insular infarction has led to a decrease in parasympathetic nervous activity and shifted the sympathovagal balance towards predominant sympathetic tone. Thus, it was suggested that ventricular tachycardia due to relatively higher sympathetic nervous system activity is associated with mortality in patients with right Ic infarction. Until now, there have been few reports assessing the Ic and autonomic nervous system activity in relation to hemispheric laterality in a large study population. The data presented in the paper by Hanne et al. [1] would have much more importance if the exact mechanism underlying the relationship between the right Ic infarction and mortality were provided.