Faculty Bibliography

PURPOSE: Vagus nerve stimulation (VNS) is used as an adjunctive therapy for treating patients with drug-resistant epilepsy. The impact of VNS on cardiovascular autonomic function remains to be fully understood. We determined changes in cardiovascular sympathetic and parasympathetic, and hemodynamic function in association with VNS in patients with drug-resistant focal epilepsy. METHOD: Longitudinal (n=15) evaluation of beat-to-beat blood pressure (BP) and heart rate variability (HRV), baroreflex sensibility, and hemodynamic function performed before VNS implantation, 6-months after implantation, and a mean of 12-months after implantation; and cross-sectional study (n=14) of BP and HR variability and baroreflex sensitivity during VNS on and VNS off. RESULTS: In the longitudinal study, no differences were observed between the baseline, the 6-month visit, and the final visit in markers of parasympathetic cardiovagal tone or baroreflex sensitivity. Systolic and diastolic BP upon 5-min of head-up tilt increased significantly after VNS implantation (Systolic BP: -16.69+/-5.65mmHg at baseline, 2.86+/-16.54mmHg at 6-month, 12.25+/-12.95mmHg at final visit, p=0.01; diastolic BP: -14.84+/-24.72mmHg at baseline, 0.86+/-16.97mmHg at 6-month, and 17+/-12.76mmHg at final visit, p=0.001). CONCLUSION: VNS does not seem to produce alterations in parasympathetic cardiovagal tone, regardless of the laterality of the stimulus. We observed a slight increase in sympathetic cardiovascular modulations. These changes had no significant hemodynamic implications. These findings contribute to the understanding of potential mechanisms of action of VNS.

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.

Background: Stress-induced adrenergic hypertensive crises are a cardinal feature of familial dysautonomia (FD). Classically, this is treated with clonidine and benzodiazepines, which cause excessive sedation and can lead to respiratory arrest. Dexmedetomidine is a recently introduced compound, 8 times more specific for central alpha-2 adrenergic receptors than clonidine, resulting in less sedation. Advantages over clonidine are also that dexmedetomidine can be administered intravenously (IV), and its half-life is shorter (12 vs. 2 h), which allows an easy titration.
Method(s): Retrospective chart review of IV dexmedetomidine use to treat refractory hypertensive crisis in patients with FD.
Result(s): IV dexmedetomidine was used 15 times in 9 patients (mean age: 26 years; 44 % men) with acute adrenergic crisis. Crisis triggers included respiratory infection (n = 8), emotional stress (n = 3), surgery (n = 1), bacteremia (n = 1), gastroenteritis (n = 1) and bleeding gastric ulcer (n = 1). Before treatment, all patients had signs of adrenergic activation including skin flushing, nausea/retching, vomiting, diaphoresis, and agitation. Blood pressure (BP) was 1616/1026 mmHg and heart rate (HR) was 1134 bpm. IV dexmedetomidine was administered at an average rate of 0.510.13 mcg/kg/h. One hour post-infusion, BP decreased to 1165/586 mmHg (p<0.0001) and HR to 975 bpm (p = 0.002). Drowsiness occurred in one patient, although he was easily arousable. There were no episodes of rebound hypertension or respiratory depression. In one case, rapid titration at a high dose resulted in paradoxical hypertension, which subsided immediately upon dexmedetomidine discontinuation.
Conclusion(s): IV dexmedetomidine is an effective, well-tolerated approach for managing adrenergic crises in patients with FD. In contrast to other commonly used medications, dexmedetomidine does not induce excessive sedation or respiratory depression. In a small percentage of patients, rapid IV dosing may result in paradoxical hypertension due to its direct action on peripheral postsynaptic alpha2-adrenergic receptors

Autoimmune autonomic ganglionopathy (AAG) is a rare condition characterized by acute-onset generalized autonomic failure. Some of these patients also develop severe sensory and motor deficits. Droxidopa, an oral norepinephrine precursor, has been previously reported as effective treatment of neurogenic orthostatic hypotension (nOH) in one patient with AAG. Here we report our experience using droxidopa to treat symptomatic nOH in 3 patients with suspected AAG. Patient #1 (35-year-old woman) presented with acute-onset recurrent syncope, urinary retention, constipation, dry mouth, and decreased sweating, but no motor or sensory deficits. Patient #2 (11 year-old boy) and patient #3 (43-year-old woman) presented with similar autonomic deficits as well as severe impairment in all sensory modalities, but patient #3 also had severe generalized muscle weakness and had been initially diagnosed with Guillain-Barre syndrome. In all three patients, autonomic testing showed severe nOH confirmed by absent phase IV blood pressure overshoot after release of the Valsalva strain and very low or undetectable plasma norepinephrine levels. Ganglionic acetylcholine receptor antibodies were not detected in any patient. Droxidopa increased blood pressure and improved symptoms in all three patients. After 1 year, patient #1 is still receiving droxidopa 200 mg three times/day with normalization of standing BP, and continued symptomatic improvement. During the initial droxidopa titration, patients #2 and #3 experienced nausea, abdominal pain, and severe hypertension (>180 mmHg) with dosages > 200 mg. Both have now been receiving 100 mg once/day for a year with improvement in orthostatic tolerance and BP, no side effects and no supine hypertension. In conclusion, droxidopa substantially increased blood pressure standing and reduced symptoms of orthostatic hypotension in adult and pediatric patients with suspected acute autonomic ganglionopathy

Congenital insensitivity to pain with anhidrosis (CIPA, also known as hereditary sensory and autonomic neuropathy type IV) is a rare autosomal recessive disorder caused by mutations in the gene encoding for neurotrophic tyrosine kinase receptor type 1, a receptor for nerve growth factor (NTRK1-NGF). We recently described that patients with CIPA have very low or undetectable circulating norepinephrine levels. Since these mutations severely deplete the development of noradrenergic neurons in the periphery, they presumably also affect those in the central nervous system. Patients with CIPA have low IQ and behavioral problems including hyperactivity and reckless impulsivity, likely the result of a central deficiency in norepinephrine. We explored whether treatment with droxidopa, a synthetic norepinephrine precursor, which crosses the blood brain barrier, could improve behavioral features in a patient with CIPA. Our patient was a 29-year-old woman with a classic phenotype and molecular confirmation of a mutation in the NTRK1 gene (c360- 2A >C pathogenic variant). She had symptoms of attention deficit and hyperactivity and scored highly on the adult ADHD self-report scales (Scores Part A: 4/6 and Part B: 9/12). She had high scores in the attentional (17 and 4), motor (21 and 10), and planning (21 and 17) domains of Barratt impulsiveness scale. NICHQ Vanderbilt assessment scale also indicated attention deficits and hyperactivity. After two months treatment with droxidopa (at 400 mg/day), attention and hyperactivity scales scores decreased to the normal range (Scores Part A: 3/6 and Part B: 4/12). Impulsiveness scores assessed by Barratt impulsiveness scales also improved (attentional scores 15 and 11, motor scores 19 and 9 and planning scores 20 and 9). This case report suggests that behavioral deficits might be reversed in patients with CIPA by norepinephrine replenishment therapy. Clinical studies to evaluate the usefulness of droxidopa to treat behavioral problems in CIPA patients are warranted

Background: Patients with familial dysautonomia (FD) have asthmalike exacerbations with coughing, wheezing, and hypoxia. While many are treated empirically with bronchodilators, it is still unknown whether airway obstruction in these patients is pharmacologically reversible by modifying autonomic tone.
Method(s): We conducted a two-center, randomized, placebo-controlled, double blind, crossover study to assess the safety and efficacy of albuterol (a direct acting sympathomimetic) vs. ipratropium bromide (a parasympatholytic muscarinic blocker). Albuterol (0.083 %, 2.5 mg/3 ml), ipratroprium bromide (0.02 %, 500 mcg/2.5 ml) and placebo (0.9 % sodium chloride 3 ml) were administered by nebulization in random order over 15 min in the seated position. Airway responses were assessed with spirometry and impulse oscillometry pre- and 30 min post-dose. Continuous blood pressure, RR-intervals and cardiac impedance were measured non-invasively (TaskForce Monitor, CNSystems, Graz, Austria). Raw data tracings were analyzed blindly.
Result(s): Fifteen patients were enrolled. All had a documented history of aspiration into the airway and acute episodes of coughing and wheezing. Beta-adrenergic activation with albuterol significantly increased forced vital capacity (p = 0.041) and forced expiratory volume within 1 s (p = 0.002). In line with this, impulse oscillometry at 5 Hz was significantly lower post-albuterol (p = 0.006), suggesting a reduction in total airway resistance. Blockade of muscarinic acetylcholine receptors with ipratroprium had less bronchodilatory effects. Both treatments were well tolerated and had no effects on blood pressure, heart rate or derived cardiac output.
Conclusion(s): In patients with FD, beta-adrenergic stimulation more effectively reversed airway obstruction than muscarinic blockade. Both treatments were well tolerated and had no measureable systemic effects