Faculty Bibliography

Background: Hereditary sensory and autonomic neuropathy type IV (HSAN-IV) is a recessive disease caused by mutations affecting the tyrosine kinase receptor. The disorder affects the development of sensory and sudomotor sympathetic nerve fibers resulting in complete insensitivity to pain and anhidrosis. However, little is known about the cardiovascular autonomic phenotype of the disorder. Methods: We measured blood pressure, heart rate and catecholamines, vasopressin, endothelin and renin activity in plasma while supine and after 10 min of passive upright tilt in 10 patients with typical clinical features of HSAN-IV and diagnostic confirmation with genetic testing (mean age 9 +/- 2 years old, 4 females). Results: In the supine position, blood pressures (104 +/- 5/ 58 +/- 4 mmHg) and heart rates (87 +/- 9 beats/min) were normal. During upright tilt, mean arterial blood pressure changed little (-5 +/- 5 mmHg, p = 0.17) and heart rate increased appropriately (+23 +/- 5 beat/min, p<0.001). In all patients, plasma norepinephrine levels were low or undetectable while in the supine position (31 +/- 3 pg/ml) and failed to increase with upright tilt (4 +/- 5 pg/ml). Plasma renin activity levels increased slightly from 2.0 +/- 0.6 to 3.6 +/- 1.1 pg/ml with head-up tilt (+68 +/- 33 D%, p<0.03). Plasma vasopressin increased little and endothelin levels were essentially unchanged during upright tilt. Conclusions: Patients with HSAN-IV have very low levels of norepinephrine while supine and upright, but do not have orthostatic hypotension. Other vasoactive peptides involved in orthostatic blood pressure maintenance are not increased. These results challenge our current concepts of the role of norepinephrine in the regulation of blood pressure. The mechanism by which patients with HSAN-IV maintain their blood pressure is unknown

Background: Sympathetic denervation of the heart is frequent in patients with sporadic and genetic synucleinopathies. In 2004, we described a new mutation in the synuclein gene (E46K). The aim of this study was to analyze autonomic function and cardiac sympathetic innervation in symptomatic and asymptomatic carriers of this mutation. Patients and methods: We studied 6 members of the original family, four symptomatic (i.e., with parkinsonism, ages 88, index case, deceased, 46, 59 and 52 years) and two asymptomatic carriers (i.e., without motor impairment, age 52 and 29 years). Patients filled the SCOPA autonomic questionnaire, and underwent blood pressure and heart rate monitoring during head up tilt with measurements of plasma norepinephrine, Valsalva maneuver and deep breathing, recording of sympathetic skin response (SSR), and cardiac MIBG scintigraphy. The myocardium of the index case was stained with tyrosine hydroxylase to identify sympathetic nerve terminals. Results: All symptomatic and the older asymptomatic carrier reported abnormalities in the SCOPA questionnaire. Plasma norepinephrine supine and tilted was normal in all subjects. One patient had significant orthostatic hypotension. Heart rate during deep breathing was reduced in one patient and during Valsalva in 2 patients. SSR was normal in all subjects. All the symptomatic and the older asymptomatic carrier of the mutation had markedly diminished cardiac MIBG uptake. There was complete absence of tyrosine hydroxylase immune staining of the myocardium. Conclusions: We found imaging and histological evidence of cardiac sympathetic denervation in symptomatic and asymptomatic carriers of the E46K synuclein gene mutation. Cardiac innervation was preserved in a young asymptomatic carrier of the mutation. The sympathetic denervation appears to be organ specific selectively affecting the heart because plasma norepinephrine, blood pressure and SSR responses were normal. Follow up of asymptomatic carriers will help determine the precise sequence of synuclein-related neurodegeneration, an important step for neuroprotective strategies

Background: Visceral sensations are relayed to the brain through a network of afferent nerves. Awareness of these sensations differs among individuals, likely due to different thresholds and CNS processing characteristics. Differences in the conscious awareness of bodily sensations may explain specific cardiovascular phenotypes. Thus, our goal was to evaluate the role, if any, of conscious awareness of body sensations and their relationship with hemodynamic responses to tilt in patients with orthostatic intolerance. Methods: Thirty-two otherwise healthy patients who complained of orthostatic intolerance participated in the study. We assessed perception of body sensations on a self-reported body vigilance scale. We measured blood pressure, heart rate and plasma catecholamine responses to passive upright tilt. Thirteen patients experienced typical vasovagal syncope (i.e., a fall in blood pressure and heart rate) 4; patients had an increase in heart rate >30 beat/min without a fall in blood pressure and were diagnosed as postural tachycardia syndrome; and 15 patients had normal cardiovascular responses to tilt and were classified as having unexplained orthostatic intolerance. Results: Self-reported feelings of shortness of breath (p<0.05), tingling (p<0.01), numbness (p<0.003) and chest discomfort (p<0.01) were correlated positively with supine plasma epinephrine levels and the increase in plasma epinephrine levels with tilt (p<0.02). Higher body vigilance was significantly related with the increase in heart rate during tilt, both at 3 min (p<0.02) and the maximum heart rate recorded (p<0.002). Patients with unexplained orthostatic intolerance scored higher for the time spent 'scanning their body for sensations' compared with patients who had vasovagal syncope during tilt (52 +/- 9 vs. 23 +/- 6%, p<0.02). Conclusion: Increased somatic vigilance is associated with a greater release of epinephrine on standing and faster heart rates. Increased somatic vigilance is associated with the postural tachycardia syndrome and may be the cause of hitherto unexplained orthostatic intolerance

Background: Patients with familial dysautonomia have a selective defect in the afferent neurons of the baroreflex. Failure to sense blood pressure result in the unregulated release of plasma catecholamines and volatile blood pressure. One of the most disabling features of familial dysautonomia are the recurrent attacks of nausea, retching and vomiting triggered by emotional or physiological stressors and associated with hypertension, tachycardia and psychomotor agitation. A pronounced surge in circulating norepinephrine during these crises readily explains the hypertension, but the cause of the nausea and vomiting remains unknown. Methods: Seven patients with familial dysautonomia (mean age 17 +/- 3 years, 4 females) confirmed by genetic testing were studied. We monitored blood pressure and heart rate and measured plasma catecholamines when they were feeling well and during typical vomiting crises triggered by emotionally charged situations. Results: When the patients were feeling well, average supine blood pressure was 124 +/- 7/64 +/- 5 mmHg with a heart rate of 81 +/- 3 beats/min. All patients experienced typical crises when they complained of severe nausea and were retching loudly. Vomiting was prevented by the fundoplication surgery. During crises, all patients were hypertensive (180 +/- 9/116 +/- 4 mmHg) and tachycardic (124 +/- 4 beats/min) but denied feeling palpitations. While supine, plasma norepinephrine levels increased from 130 +/- 42 to 772 +/- 151 pg/ml (p<0.002), plasma epinephrine levels increased from 20 +/- 5 to 63 pg/ml, and plasma dopamine levels increased markedly from 22 +/- 2 to 96 +/- 20 pg/ml. Conclusions: Our finding of high levels of circulating dopamine during crises in patients with familial dysautonomia suggest that the severe nausea and vomiting is due to activation of dopamine receptors in the chemoreceptor trigger zone

Familial dysautonomia is an hereditary sensory and autonomic neuropathy (HSAN type III), expressed at birth, that is associated with reduced or absent pain and temperature sensibilities, postural hypotension, absent baroreflex function and labile blood pressure that increases markedly during emotional excitement (Norcliffe-Kaufmann et al. 2010). Given the absent baroreflex function we tested the hypothesis that cardiac-locked bursts of muscle sympathetic nerve activity (MSNA) are absent in familial dysautonomia. Tungsten microelectrodes were inserted percutaneously into muscle or cutaneous fascicles of the common peroneal nerve in 10 patients with FD. Spontaneous bursts of MSNA were absent, but we found evidence of tonically firing sympathetic neurones that increased during emotional arousal. Conversely, skin sympathetic nerve activity (SSNA) appeared normal. We conclude that the loss of phasic bursts of MSNA and the loss of baroreflex modulation of muscle vasoconstrictor drive contributes to the poor control of blood pressure in familial dysautonomia

OBJECTIVE: To test the hypothesis that panic disorder (PD) patients have a heightened or deregulated autonomic nervous system at rest and during autonomic challenge compared with healthy controls (HC); and to test a second hypothesis that severity of illness differentiates patients'; sympathovagal balance both at rest and during orthostatic challenge. METHODS: Spectral analysis of heart rate (HR) and blood pressure was performed on 30 PD and 10 HC participants during an orthostatic challenge (head-up tilt). RESULTS: PD patients presented higher HR (p < .001), lower heart rate variability (HRV) (p < .015), higher mean diastolic blood pressure (p < .006), higher low-frequency component of HR (p < .001), and a higher ratio of low-frequency to high-frequency component of HR (LF/HF) (p < .022) than HC at baseline. During tilt, PD patients responded with higher HR (p < .039), lower HRV (p < .043), increased mean diastolic blood pressure (p < .028), and a mild increase in LF/HF, whereas controls responded with a five-fold increase in LF/HF (p < .022). Patients with higher illness severity ratings (Clinical Global Impression Scale) showed higher HR (p < .002), lower HRV (p < .026), and a lower total power of systolic blood pressure (p < .02) compared with less ill patients. CONCLUSION: These findings demonstrate a consistently higher or deregulated autonomic arousal in PD patients at rest and during orthostatic challenge compared with HC. These data also reveal a possible association between the level of anxiety illness severity and sympathovagal balance, which may imply greater cardiac risk

Renal failure is a common problem in patients with familial dysautonomia (FD). By age 25, 20% of patients with FD have end stage renal disease. To determine the role of arterial hypertension in the development and progression of kidney disease, we compared glomerular filtration rate (Cockcroft-Gault equation) over time in 50 patients with FD according to their level of arterial hypertension throughout childhood (until age 15). In addition, to assess the possible impact of increased blood pressure variability on renal function we examined the relationship between the standard deviation of ambulatory blood pressure over 24-h, an indicator of blood pressure volatility, and glomerular filtration rate. Patients with average systolic blood pressure[180 mmHg during childhood (stage III and IV hypertension American Heart Association) had a faster decline in glomerular filtration rate over time than patients with lower blood pressures (Kaplan-Meyer survival curve). There was an inverse relationship between the standard deviation of ambulatory blood pressure over 24-h and glomerular filtration rate, i.e., patients with higher standard deviation had lower glomerular filtration rates (y = - 3.3044x + 167.54, R² = 0.1949, p<0.01). Our results indicate that arterial hypertension during childhood and the magnitude of blood pressure volatility are risk factors for the development of renal failure in patients with familial dysautonomia. Prospective studies are warranted to determine whether controlling hypertension and blood pressure variability can delay the onset or slow the progression of renal failure in these patients

We report the case of a woman with Munchausen syndrome who surreptitiously injected epinephrine causing recurrent ventricular tachyarrhythmias accompanied by dramatically high plasma levels of epinephrine and normal norepinephrine levels