Autonomic dysfunction: A comparative study of patients with Alzheimer's and frontotemporal dementia - A pilot study.
BACKGROUND
In frontotemporal dementia (FTD) and Alzheimer's disease (AD), central autonomic structures get affected early. An insight into autonomic functions in these patients is likely to be of diagnostic importance and thus help in prognosticating and also probably explain unexplained sudden death in some of these patients.


OBJECTIVE
The objective of this study is to identify autonomic dysfunction prevailing in patients. Then, if there is dysfunction, is the pattern same or different in these two conditions. And if different it will serve as an additional biomarker for specific diagnosis.


METHODS
There were 25 patients and 25 controls and six patients and three controls in AD and FTD groups, respectively. The participants who were recruited were assessed for heart rate variability and conventional cardiac autonomic function testing. The parameters were analyzed using LabChart version 7 software and compared with control population using appropriate statistical methods using SPSS version 22 software.


RESULTS
The mean overall total power was low in the FTD group (P< 0.001), and there was significant reduction in the standard deviation of normal-to-normal intervals and root mean square of successive differences (P< 0.001) with elevated sympathovagal balance in the FTD group (P= 0.04). Patients with AD also showed sympathetic dominance, but there was in addition parasympathetic suppression unlike in the FTD group.


CONCLUSIONS
This study reveals autonomic dysfunction in patients with FTD and AD. Both conditions show sympathetic dominance, probably consecutive to the involvement of central autonomic regulatory structures as a shared domain. It remains to be confirmed if these findings are the cause or effect of neurodegeneration and might open up newer territories of research based on the causal role of neurotransmitters in these regions and thus lead to novel therapeutic options such as yoga. The presence of parasympathetic suppression in AD in addition helps differentiate these two conditions.
Department of Clinical Neurosciences, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India.
Thomas Gregor
TG
Issac
Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India.
Sadanandavalli Retnaswami
SR
Chandra
Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India.
Neelesh
N
Gupta
Department of Neurophysiology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India.
Malligurki Raghurama
MR
Rukmani
Department of Clinical Neurosciences, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India.
S
S
Deepika
Department of Neurophysiology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India.
T N
TN
Sathyaprabha
Alzheimer's disease; autonomic function tests; frontotemporal dementia; heart rate variability; sympathovagal balance