Autonomic dysfunction in progressive supranuclear palsy (PSP) remains controversial. Some studies found no significant autonomic dysfunction in PSP patients [43–46], whereas others reported autonomic cardiovascular abnormalities in PSP patients [14, 47–50]. Holmberg et al. [51] evaluated autonomic function in PD, PSP, and MSA by means of laboratory autonomic tests, which included analysis of HRV at rest and during deep respiration, as well as blood pressure changes during 75° head-up tilt. Decreased HRV and severe hypotensive responses were seen in MSA patients regardless of age and disease duration, whereas this combination of findings was seen only in PD patients who were very elderly and had a prolonged disease duration. In PSP, only a few patients showed decreased HRV, and hypotensive responses were limited (Fig. 11.2).

Resting HRV and heart rate changes to deep breathing (HRDB) and to standing (30:15 ratio), which indicate cardiac vagal denervation, are reduced in DLB. Cardiac vagal dysfunction is also found in dementia with PD (PDD) [52, 53]. Differences among dementia with Lewy bodies (DLB), PDD, and PD without dementia with respect to the involvement of the autonomic nervous system have been demonstrated in a study investigating cutaneous and cardiovascular autonomic functions in patients with Lewy body disease [53]. That study used the coefficient of variation of RR intervals (CVRR) to estimate cardiovascular function. Abnormally low values of CVRR were observed in half of the patients with DLB, as compared with 25 % of the patients with PDD and PD. The mean CVRR value was significantly lower in the patients with DLB (Fig. 11.3). It was also reported that sudomotor function may be severely affected in Lewy body disorders, while skin vasomotor function and the cardiovascular system may be more severely affected in DLB and PDD than in PD.

Allan et al. [52] used spectral analysis of HRV to assess cardiovascular autonomic function in patients with Alzheimer disease (AD), vascular dementia (VaD), DLB, and PDD. They reported that the severity of cardiovascular autonomic dysfunction differed significantly among these four types of dementia. These four groups of patients also showed significant differences in total spectral power as well as LF and HF components (Table 11.3). Mean RR interval, very LF component, and LF/HF ratio did not differ significantly among the four groups, while LF and HF components were lower in patients with PDD than in healthy controls. The LF and HF components were also reduced as compared with the AD patient group. The LF components in patients with DLB were significantly lower than those in the healthy controls. Allan et al. [52] also evaluated cardiac autonomic dysfunction using Ewing’s protocol to perform autonomic function tests in patients with dementia. Ewing’s protocol consisted of five tests, consisting of three predominantly parasympathetic tests and two predominantly sympathetic tests, to assess autonomic dysfunction at bedside [54]. The test results were used to classify autonomic dysfunction into five groups according to severity [55, 56]
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According to Ewing’s protocol, PDD was consistently associated with impairment of both parasympathetic and sympathetic function as compared with controls and AD. DLB showed impairment of parasympathetic function. PDD showed significantly higher impairment than DLB in terms of the Valsalva ratio, considered an indicator of parasympathetic function. Patients with VaD showed impairment based on the Valsalva ratio. Autonomic dysfunction occurs in all common dementias but is especially prominent in PDD and has important treatment implications [52]. Several studies have also described partial impairment of the sympathovagal balance and abnormal postural heart modulation in AD [57, 58], while recent reports indicate that cardiovagal dysfunction in AD correlates with cognitive decline [59], although resting HRV can be normal [60].

Autonomic dysfunction is frequently seen in patients with ischemic stroke [61, 62]. Patients with ischemic stroke have depressed parasympathetic activity in the acute or chronic stages, while the impairment of sympathetic activity remains controversial [63]. Acute cerebrovascular diseases are thought to significantly decrease HRV as a result of cardiovascular autonomic dysregulation. Decreased HRV has been demonstrated in stroke by cardiovascular reflex tests [64], as well as by spectral analysis of HRV based on 24-h ECG recordings [65, 66]. The HF and LF spectral components of HRV seem to be persistently reduced in hemispheric lesions [67, 68]. It is also known that decreased HRV is an independent predictor of mortality in patients with acute ischemic stroke [69]. The underlying mechanisms of these findings in patients with ischemic stroke remain to be elucidated. Increased sympathetic activity has been reported in acute stroke in some studies [61], although Korpelainen et al. found no impairment of sympathetic activity in patients with acute ischemic stroke [63]. The increased blood pressure variability in patients with acute stroke has been attributed to impaired baroreceptor reflex sensitivity (BRS) associated with the central parasympathetic and sympathetic nervous systems [62, 69]. Impaired BRS has also been linked to increased long-term mortality after acute stroke.

Xiong et al. [70] have studied whether autonomic function is impaired during different phases in ischemic stroke, using Ewing’s protocol of autonomic function tests as well as spectral analysis of HRV. Stroke patients in both the acute and chronic phases had significantly lower LF than did controls. On autonomic function testing by Ewing’s protocol [53–55], patients with acute ischemic stroke showed impairment in two parasympathetic tests (Valsalva ratio, heart rate response to deep breathing), while those in the chronic stage showed impairment in all parasympathetic tests as compared with controls. They concluded that autonomic dysfunction in ischemic stroke persisted in the chronic stage (up to 6 months) after stroke and that parasympathetic dysfunction rather than sympathetic dysfunction predominates after ischemic stroke. The mechanism underlying the autonomic impairment in patients with stroke remains unclear. A few studies have assessed cardiovascular autonomic function in subtypes of ischemic stroke [71, 72], but the results were conflicting. One study reported that there was no significant association between impaired autonomic function and subtypes of acute ischemic stroke [73], whereas another study demonstrated that patients with acute atherosclerotic infarction of large arteries had lower parasympathetic activity and higher sympathetic activity than those with acute lacunar infarction [71]. Xiong et al. [73] evaluated cardiovascular autonomic function in ischemic stroke patients with large-artery atherosclerosis (LAA) and patients with small-vessel occlusion (SCO) by performing autonomic function tests by Ewing’s protocol and spectral analysis of HRV. The results demonstrated that cardiovascular autonomic dysfunction was influenced by the subtype of ischemia and that patients with LAA had more severely impaired parasympathetic and sympathetic functions than those with SCO (Table 11.4).