Faculty Bibliography

OBJECTIVE: To define the clinical features and biomarkers that predict which patients with pure autonomic failure will develop Parkinson disease, dementia with Lewy bodies, or multiple system atrophy. METHODS: One hundred patients who presented with pure autonomic failure were recruited at 5 medical centers in the U.S. Seventy-four patients agreed to be followed prospectively. Patients underwent clinical evaluations including neurological rating scales, sleep questionnaires, smell test, and sympathetic and parasympathetic cardiovascular autonomic function tests. RESULTS: At enrollment, patients were 68(12) years old [(median (interquartile range)] and had had autonomic failure for 5(7) years. Within 4-years of follow-up, 25 of 74 subjects (34%) developed dementia with Lewy bodies (in 13), Parkinson disease (in 6), or multiple system atrophy (in 6). The presence of probable REM sleep behavior disorder was strongly associated with the development of a manifest CNS synucleinopathy (odds ratio=7.1). Patients who phenoconverted to multiple system atrophy had younger age at onset of autonomic failure, severe bladder/bowel dysfunction, preserved olfaction, and a cardiac chronotrophic response upon tilt >10 beats per minute. Those who phenoconverted to Parkinson disease or dementia with Lewy bodies had decreased olfaction, a lesser chronotrophic response to tilt, and a longer duration of illness. The small group of patients retaining the pure autonomic failure phenotype had very low plasma norepinephrine levels, slow resting heart rate, no REM sleep behavior disorder, and preserved smell. INTERPRETATION: Patients presenting with pure autonomic failure are at high risk of phenoconverting to a manifest CNS synucleinopathy. Specific clinical features predict future diagnosis

BACKGROUND: Multiple system atrophy (MSA) is a rare, adult-onset, rapidly progressive fatal synucleinopathy that primarily affects oligodendroglial cells in the brain. Patients with MSA only rarely have visual complaints, but recent studies of the retina using optical coherence tomography (OCT) showed atrophy of the peripapillary retinal nerve fiber layer (RNFL) and to a lesser extent the macular ganglion cell layer (GCL) complex. METHODS: We performed a literature review and meta-analysis according to the preferred reporting items for systematic reviews and meta-analyses guidelines for studies published before January 2017, identified through PubMed and Google Scholar databases, which reported OCT-related outcomes in patients with MSA and controls. A random-effects model was constructed. RESULTS: The meta-analysis search strategy yielded 15 articles of which 7 met the inclusion criteria. The pooled difference in the average thickness of the RNFL was -5.48 mum (95% CI, -6.23 to -4.73; p < 0.0001), indicating significant thinning in patients with MSA. The pooled results showed significant thinning in all the specific RNFL quadrants, except in the temporal RNFL quadrant, where the thickness in MSA and controls was similar [pooled difference of 1.11 microm (95% CI, -4.03 to 6.26; p = 0.67)]. This pattern of retinal damage suggests that MSA patients have preferential loss of retinal ganglion cells projecting to the magnocellular pathway (M-cells), which are mainly located in the peripheral retina and are not essential for visual acuity. Visual acuity, on the other hand, relies mostly on macular ganglion cells projecting to the parvocellular pathway (P-cells) through the temporal portion of the RNFL, which are relatively spared in MSA patients. CONCLUSION: The retinal damage in patients with MSA differs from that observed in patients with Parkinson disease (PD). Patients with MSA have more relative preservation of temporal sector of the RNFL and less severe atrophy of the macular GCL complex. We hypothesize that in patients with MSA there is predominant damage of large myelinated optic nerve axons like those originating from the M-cells. These large axons may require higher support from oligodendrocytes. Conversely, in patients with PD, P-cells might be more affected.

BACKGROUND:Putaminal diffusivity in brain magnetic resonance diffusion-weighted imaging (DWI) is increased in patients with the parkinsonian variant of multiple system atrophy (MSA-P) compared to Parkinson disease (PD) patients. PURPOSE/OBJECTIVE:We performed a systematic review and meta-analysis to evaluate the diagnostic accuracy of DWI to distinguish MSA-P from PD. METHODS:Studies on DWI were identified through a systematic PubMed and Clarivate Analytics® Web of Science® Core Collection search. Papers were selected based on stringent inclusion criteria; minimum requirement was the inclusion of MSA-P and PD patients and documented true positive, true negative, false positive and false negative rates or overall sample size and reported sensitivity and specificity. Meta-analysis was performed using the hierarchical summary receiver operating characteristics curve approach. RESULTS:The database search yielded 1678 results of which 9 studies were deemed relevant. Diagnostic accuracy of putaminal diffusivity measurements were reported in all of these 9 studies, whereas results of other regions of interest were only reported irregularly. Therefore, a meta-analysis could only be performed for putaminal diffusivity measurements: 127 patients with MSA-P, 262 patients with PD and 70 healthy controls were included in the quantitative synthesis. The meta-analysis showed an overall sensitivity of 90% (95% confidence interval (CI): 76.7%-95.8%) and an overall specificity of 93% (95% CI: 80.0%-97.7%) to distinguish MSA-P from PD based on putaminal diffusivity. CONCLUSION/CONCLUSIONS:Putaminal diffusivity yields high sensitivity and specificity to distinguish clinically diagnosed patients with MSA-P from PD. The confidence intervals indicate substantial variability. Further multicenter studies with harmonized protocols are warranted particularly in early disease stages when clinical diagnosis is less certain.

The ability of the skin to conduct electricity depends on sweat secretion. This is referred to as electrodermal or electrochemical skin conductance. Recently, a technique has been developed to assess electrodermal activity using reverse iontophoresis dependent on sweat chloride levels. This method can reliably identify patients with cystic fibrosis, a disease with well-described increases in chloride concentration in sweat. Our goal was to determine the relationship between electrodermal response and serum chloride levels in other patient groups. We conducted a cross-sectional study involving 38 subjects with HSAN-III (familial dysautonomia, FD) and 20 healthy controls. Electrodermal activity of the soles was assessed using stainless steelbased plate electrodes applied under the soles of the feet for 3 min (Sudoscan). The influence of age, serum electrolyte levels, and medications were analyzed.
Result(s): Electrodermal activity was normal (>60 microS) in 24 patients (63 %) and reduced (<60 microS) in the remaining 14. There was a direct correlation between electrodermal activity and serum chloride levels (p = 0.007). Reduced electrodermal activity was explained by low serum chloride in 6 patients, and likely by medications in 8 (clonidine). All controls had normal electrodermal activity, but because their serum chloride levels were normal in every subject (>97 mEq/L), no correlation could be established.
Conclusion(s): Low serum chloride levels result in reduced electrodermal activity. In addition to medications, serum chloride levels should be checked to properly interpret electrodermal activity measurements

Background: Normally, during sleep, when cortical influences are minimized, blood pressure (BP) and heart rate (HR) fall (i.e., nocturnal dipping). In patients with afferent baroreflex failure, in whom BP and HR are highly dependent on cortical influences, this nocturnal dipping is usually preserved. There are, however, a number of patients with afferent baroreflex failure in whom BP does not dip at night. The reasons for this are unknown.
Method(s): We examined the 24-hour ambulatory BP profiles in 50 patients with afferent baroreflex failure of acquired (n = 6) or genetic origin (familial dysautonomia n = 44). BP and HR were captured at 30-minute intervals over a 24-h period. Nighttime sleep periods were identified from the patient's diary. Dipping was defined as a 10 % or greater fall in systolic and diastolic blood pressure at night.
Result(s): Normal BP nocturnal dipping was present in only 50 % of the patients; 33 % of patients had reversal of the circadian rhythm with higher blood pressures at night. In the remaining 17 %, nocturnal BP was similar to daytime BP. Patients with preserved nocturnal dipping had a significantly higher glomerular filtration rate (8430 mL/ min) than those that did not dip at night (6130 mL/min, p = 0.043).
Conclusion(s): Lack of nocturnal BP dipping in patients with afferent baroreflex failure was associated with impaired renal function. These findings suggest that in patients with FD, a non-dipping profile may involve abnormalities in extracellular volume and/or impaired regulation of vascular resistance (i.e., abnormal endothelial function)

Background: Infusion of vasoactive agents in the assessment of orthostatic intolerance in the autonomic laboratory is controversial. The technique of lower body negative pressure (LBNP) was described two decades ago. LBNP exaggerates orthostatic stress by closely mimicking a physiologic stimulus, and has the advantage of being quickly reversible. However, it is not routinely used in clinical practice.
Objective(s): To describe our experience using LBNP in the clinical autonomic laboratory in patients with orthostatic intolerance of unclear origin.
Method(s): We used a customized airtight cover, sealed to a tilttable and to the subject at the level of the iliac crest. After 30 min of asymptomatic passive head-up tilt, LBNP was applied while the patient was still upright. Suction was briefly initiated at -20 mmHg for 1-min and then increased to -40 mmHg for the following 10-min. Blood pressure, heart rate and plasma catecholamines when supine, after 10-min of head up tilt, and during syncope or other paroxysmal event, were measured. Time from LBNP onset to episode was recorded.
Result(s): Fifteen subjects (8 men; aged 40 +/- 20 years, range: 12-75 years) were enrolled. During LBNP, 7 subjects developed typical vasovagal syncope (after 3.8 +/- 1.3 min of LBNP) with hypotension and bradycardia and marked increases in plasma levels of epinephrine and vasopressin. Six tolerated the procedure uneventfully. One patient became unresponsive and his head stooped forward but BP and HR remained stable without changes in plasma catecholamines. The remaining patient had flailing bilateral movements with no changes in consciousness, BP or HR, but a significant increase in plasma epinephrine levels. All patients recovered without sequelae.
Conclusion(s): LBNP is a useful technique in the differential diagnosis of patients with orthostatic intolerance of unclear origin and can be easily implemented in the clinical setting. In addition to its wellknown value to induce vasovagal syncope, this technique can also be useful to induce psychogenic episodes

Background: Pure autonomic failure is a neurodegenerative synucleinopathy largely restricted to the peripheral nervous system. Later in the clinical course of the disease some patients may develop parkinsonism, cerebellar ataxia or cognitive impairment. The purpose of this study is to define the clinical features and biomarkers that predict which patients will retain a pure autonomic failure phenotype, and which will develop clinical deficits indicating spread of the synucleinopathy to the central nervous system.
Method(s): One hundred patients with pure autonomic failure were recruited at 5 medical centers in the US. Participants were followed at 12-months intervals, for 4 years to determine whether they had developed motor/cognitive abnormalities and met the diagnostic criteria of Parkinson disease (PD)/dementia with Lewy bodies (DLB) or multiple system atrophy (MSA). Smell discrimination, occurrence of REM sleep behavior disorder (RBD) and sympathetic and parasympathetic cardiovascular autonomic functions were assessed.
Finding(s): Mean age of onset of autonomic failure was 61 (+/-12) years. Patients had a 10 % per year cumulative risk for developing a CNS synucleinopathy with locomotor dysfunction or dementia. All patients who developed a CNS synucleinopathy had subtle motor impairment and RBD at the time of enrolment. Factors that predicted a future diagnosis of MSA included younger age at onset of autonomic failure, severe bladder/bowel abnormalities, normal olfaction and a >10 bpm cardiac chronotrophic response to tilt. Factors that predicted future diagnosis of PD/DLB were abnormal olfaction, a lesser chronotrophic response to tilt and longer disease duration. Patients that retained a PAF phenotype had very low circulating norepinephrine levels, slow resting heart rate, no RBD or subtle motor deficits and preserved smell discrimination.
Interpretation(s): Pure autonomic failure can be a premotor stage of a central nervous system synucleinopathy or may remain as a restricted peripheral disorder. Patients who developed PD/DLB or MSA have distinct premotor features. Patients who retain a pure autonomic failure phenotype had more severe peripheral sympathetic involvement

Droxidopa, a synthetic norepinephrine precursor, was recently approved to treat symptomatic neurogenic orthostatic hypotension (nOH). The pressor response is variable with some patients responding to doses of 100 mg while others requiring up to 600 mg three times/day. It is not known which factors predict the magnitude of the pressor response to droxidopa. We prospectively evaluated the BP response to increasing doses of droxidopa in patients with nOH in an outpatient setting. BP supine and after 3-min standing was measured before and 1-h after oral administration of 100 mg of droxidopa. Droxidopa was progressively increased until (i) complete relief of symptoms, (ii) supine systolic BP >180 mmHg, (iii) occurrence of side effects, or (iv) the maximum dose of 600 mg was reached. Sixteen subjects with nOH (6 with Parkinson disease, 5 with pure autonomic failure, 3 with autoimmune autonomic ganglionopathy, and 2 with multiple system atrophy) were evaluated. Mean BP was 126 +/- 28/72 +/- 11 mmHg supine, and 89 +/- 19/ 53 +/- 15 mmHg after 3-min standing (fall of 37/18 mmHg). Mean plasma norepinephrine while supine was 192 +/- 216 pg/ml. Maximum droxidopa dose during the titration was 212 +/- 102 mg (range 100-400 mg). Droxidopa increased BP to an average of 148 +/- 53/ 90 +/- 13 mmHg supine and 135 +/- 38/66 +/- 16 mmHg after 3-min standing (p<0.001). Plasma norepinephrine levels were inversely correlated with higher systolic BP after 3-min standing following droxidopa treatment (R2 = 0.42; p = 0.023). Four patients (3 with AAG and 1 with PAF) with very low plasma norepinephrine levels (<90 pg/ml) experienced transient nausea, vomiting, and abdominal pain during titration with dosages of 200 mg. In these patients, treatment with 100 mg/day was effective and well tolerated. Diagnostic categories did not predict response to droxidopa. In patients with nOH, lower plasma norepinephrine levels are associated with a greater pressor response to droxidopa. This response is probably related to the degree of denervation supersensitivity. Supine norepinephrine levels may be useful to predict appropriate dosing of droxidopa in a clinical setting