Autonomic Nervous System Dysfunction in PD with and without Dementia, and in Dementia with Lewy Bodies
Abstract & Commentary
By Panida Piboolnurak, MD, Assistant Professor, Department of Neurology and Neuroscience, Weill Medical College, Cornell University. Dr. Piboolnurak reports no financial relationship relevant to this field of study.
Synopsis: The sequence of disease progression in Parkinson's disease (PD) and dementia with Lewy bodies (DLB) is different, with earlier limbic cortical involvement in DLB. Limbic cortical involvement may explain the more severe autonomic dysfunction that occurs in DLB and PD with dementia.
Source: Akaogi Y, Asahina M, Yamanaka Y, et al. Sudomotor, skin vasomotor, and cardiovascular reflexes in 3 clinical forms of Lewy body disease. Neurology 2009;73:59-65.
Autonomic dysfunction is common in parkinson's disease without dementia (PD), Parkinson's disease with dementia (PDD), and in dementia with Lewy bodies (DLB). However, autonomic dysfunction appears to be more severe in DLB and PDD than in PD. This study shows the difference in autonomic nervous system involvement among these three entities.
Sudomotor, skin vasomotor, and cardiovascular reflexes were studied in 12 patients with DLB, 12 with PDD, 12 with PD, and 12 age-matched healthy controls. The tests included sympathetic sweat response (SSwR) on the palm side of the thumb, and skin vasomotor reflex (SkVR) at the index fingertip during sympathetic activation procedures (deep inspiration, mental arithmetic task, exercise, and tactile stimulation), and head-up tilt test.
The basal sweat output, basal skin blood flow, as well as baseline systolic blood pressure and heart rate in the supine position did not differ among four groups. Seven DLB patients, six PDD, and three PD showed absence of SSwR, but there was no significant difference in mean amplitudes of SSwR among these three groups. One DLB patient and three PDD had no SkVR. The SkVR amplitudes in PD and controls were comparable, but SkVR amplitudes in DLB and PDD were lower than those in controls. Orthostatic hypotension was observed in six DLB, eight PDD, and three PD. However, unlike PD, mean decreases in systolic and diastolic blood pressure during tilt test in DLB and PDD were lower than that in controls. Although mean change in heart rate during tilt test did not differ among four groups, abnormally low coefficient of variation of R-R intervals (CVR-R) was observed in six DLB, three PDD, and three PD, with the lowest mean CVR-R in DLB.
The authors explained that the impairment in sudomotor and skin vasomotor reflexes may be related to pathology in raphe nuclei. Furthermore, because a decrease in SSwR on the palm indicated a dysfunction in a so-called emotional sweating, they suggested that limbic involvement may explain autonomic dysfunction in PDD and DLB since limbic system plays an important role in emotional sweating as well as cardiovascular regulation. Moreover, given similarities in autonomic dysfunction in PDD and DLB, there is a possible uniformity of autonomic nervous system impairment in these two diseases.
Findings from this study suggest that, although autonomic dysfunction can occur in PD, PDD, and DLB, it is more severe in PDD and DLB. Many parts of the nervous system, including hypothalamus, brainstem, spinal cord, and limbic system, are involved in autonomic nervous system regulation. Given the predominant limbic and neocortical pathology in DLB, the more severe autonomic dysfunction in PDD and DLB may be partly explained by limbic involvement. However, this study has two weak points, including a small number of patients and no pathological diagnosic confirmation of the clinical syndromes.