Faculty Bibliography

Familial dysautonomia (FD) is a rare genetic disease with extremely labile blood pressure due to baroreflex deafferentation. Patients have marked surges in sympathetic activity, frequently surrounding meals. We conducted an observational study to document the autonomic responses to eating in patients with FD, and to determine whether sympathetic activation was caused by chewing, swallowing or stomach distension. Blood pressure and RR intervals were measured continuously while chewing gum (n = 15), eating (n = 20) and distending the stomach with a percutaneous endoscopic gastrostomy (PEG) tube feeding (n = 9). Responses were compared to those of normal controls (n = 10) and of patients with autonomic failure (n = 10) who have chronically impaired sympathetic outflow. In patients with FD, eating was associated with a marked, but transient pressor response (p<0.0001) and additional signs of sympathetic activation including tachycardia, diaphoresis and flushing of the skin. Chewing gum evoked a similar increase in blood pressure that was higher in patients with FD than in controls (p = 0.0001), but was absent in patients with autonomic failure. In patients with FD distending the stomach with a PEG tube feeding failed to elicit a pressor response. The results provide indirect evidence that chewing triggers sympathetic activation. The increase in blood pressure that is exaggerated in patients with FD due to blunted afferent baroreceptor signalling. The chewing pressor response may be useful as a counter-manoeuvre to raise blood pressure and prevent symptomatic orthostatic hypotension in patients with FD

BACKGROUND: Objective measures of disease progression that can be used as endpoints in clinical trials of MSA are necessary. We studied retinal thickness in patients with MSA and assessed changes over time to determine its usefulness as an imaging biomarker of disease progression. METHODS: This was a cross-sectional study including 24 patients with MSA, 20 with PD, and 35 controls, followed by a longitudinal study of 13 MSA patients. Patients were evaluated with high-definition optical coherence tomography and the Unified Multiple System Atrophy Rating Scale. Evaluations were performed at baseline and at consecutive follow-up visits for up to 26 months. RESULTS: MSA subjects had normal visual acuity and color discrimination. Compared to controls, retinal nerve fiber layer (P = 0.008 and P = 0.001) and ganglion cell complex (P = 0.013 and P = 0.001) thicknesses were reduced in MSA and PD. No significant differences between MSA and PD were found. Over time, in patients with MSA, there was a significant reduction of the retinal nerve fiber layer and ganglion cell complex thicknesses, with estimated annual average losses of 3.7 and 1.8 mum, respectively. CONCLUSIONS: Visually asymptomatic MSA patients exhibit progressive reductions in the thickness of the retinal nerve fiber layer and, to a lesser extent, in the macular ganglion cell complex, which can be quantified by high-definition optical coherence tomography. Specific patterns of retinal nerve fiber damage could be a useful imaging biomarker of disease progression in future clinical trials. (c) 2015 International Parkinson and Movement Disorder Society.

BACKGROUND: Familial dysautonomia (FD, OMIM# 223900) is an autosomal recessive disease with features of impaired pain and temperature perception and lack of functional muscle spindles. After 3 FD patients presented with rhabdomyolysis in a short time span, we aimed to determine the frequency of rhabdomyolysis is this population. METHODS AND RESULTS: In a retrospective chart review of 665 FD patients, 8 patients had at least 1 episode of rhabdomyolysis. Two patients had 2 episodes. The average incidence of rhabdomyolysis in FD was 7.5 per 10,000 person-years. By comparison, the average incidence with statins has been reported to be 0.44 per 10,000 person-years. Mean maximum creatine kinase (CK) level was 32,714 +/- 64,749 U/l. Three patients had a hip magnetic resonance imaging showing gluteal hyperintensities. CONCLUSIONS: Patients with FD have an increased incidence of rhabdomyolysis. We hypothesize that this may result from a combination of absent functional muscle spindles and muscle mitochondrial abnormalities

Neurogenic orthostatic hypotension (nOH) is a fall in blood pressure (BP) on standing due to reduced norepinephrine release from sympathetic nerve terminals. nOH is a feature of several neurological disorders that affect the autonomic nervous system, most notably Parkinson disease (PD), multiple system atrophy (MSA), pure autonomic failure (PAF), and other autonomic neuropathies. Droxidopa, an orally active synthetic amino acid that is converted to norepinephrine by the enzyme aromatic L-amino acid decarboxylase (dopa-decarboxylase), was recently approved by the FDA for the short-term treatment of nOH. It is presumed to raise BP by acting at the neurovascular junction to increase vascular tone. This article summarizes the pharmacological properties of droxidopa, its mechanism of action, and the efficacy and safety results of clinical trials.

OBJECTIVE: Congenital insensitivity to pain with anhidrosis (CIPA) is caused by mutations in the NKTR1 gene. This affects the development of nerve growth factor (NGF)-dependent neurons including sympathetic cholinergic neurons in the skin, causing anhidrosis. Cardiovascular and blood pressure regulation appears normal, but the integrity of sympathetic adrenergic neurons has not been tested. METHODS: We examined the effect of posture on blood pressure, heart rate, plasma concentration of catecholamines, vasopressin, endothelin, and renin activity in 14 patients with CIPA, 10 patients with chronically deficient sympathetic activity (pure autonomic failure), and 15 normal age-matched controls. RESULTS: In all 14 patients with CIPA, plasma norepinephrine levels were very low or undetectable and failed to increase when the patient was upright, yet upright blood pressure was well maintained. Plasma epinephrine levels were normal and increased when the patient was upright. Plasma renin activity also increased appropriately when the patient was upright and after furosemide-induced volume depletion. Nitric oxide-mediated endothelial function was intact. Patients with pure autonomic failure also had very low levels of plasma norepinephrine both supine and upright, but in contrast to patients with CIPA failed to maintain blood pressure upright. INTERPRETATION: The results indicate that postganglionic sympathetic neurons are severely depleted in CIPA, but chromaffin cells of the adrenal medulla are spared. This confirms the differential effect of NGF signaling for sympathetic neural and chromaffin cell development. The finding that patients with CIPA maintain blood pressure well on standing challenges current concepts of the role of norepinephrine in the regulation of arterial pressure. Ann Neurol 2015;77:743-752.