Faculty Bibliography

OBJECTIVE: To determine if carbidopa, a dopa-decarboxylase inhibitor that blocks the formation of dopamine outside the brain, is an effective antiemetic in patients with familial dysautonomia (FD). BACKGROUND: Patients with FD, an hereditary neuropathy that affects the development of sensory neurons of the baroreflex, are unable to restrain the release of catecholamines from sympathetic nerve terminals at times of stress. Recurrent attacks of nausea, retching and vomiting, associated with high levels of circulating dopamine are a disabling feature of the disease for which there is no effective treatment. DESIGN/METHODS: We enrolled 12 patients with FD in an open-label titration and treatment study to assess the safety of carbidopa, an inhibitor of the enzyme dopa decarboxylase that does not cross the blood brain barrier. We then conducted a randomized, double-blind, placebo-controlled, crossover study to evaluate its antiemetic efficacy. RESULTS: All patients experienced severe cyclical nausea and uncontrollable retching that was refractory to standard treatments. Carbidopa at an average daily dose of 480 mg (range 325 to 600 mg/day) was well tolerated. In the double-blind phase, patients experienced significantly less nausea and retching while on carbidopa than on placebo (p<0.03 and p<0.02. respectively). Twenty-four hour urinary dopamine excretion was significantly lower while on carbidopa (147+/-32 ug/g crt) than while on placebo (222+/-41 ug/g crt, p<0.05). CONCLUSIONS: Carbidopa appears to be a safe and effective antiemetic in patients with FD likely by reducing the formation of dopamine outside the brain. Larger trials are warranted

Familial dysautonomia (Riley-Day syndrome) is an hereditary sensory and autonomic neuropathy (HSAN type III), expressed at birth, that is associated with reduced pain and temperature sensibilities and absent baroreflexes, causing orthostatic hypotension as well as labile blood pressure that increases markedly during emotional excitement. Given the apparent absence of functional baroreceptor afferents, we tested the hypothesis that the normal cardiac-locked bursts of muscle sympathetic nerve activity (MSNA) are absent in patients with familial dysautonomia. Tungsten microelectrodes were inserted percutaneously into muscle or cutaneous fascicles of the common peroneal nerve in 12 patients with familial dysautonomia. Spontaneous bursts of MSNA were absent in all patients, but in five patients we found evidence of tonically firing sympathetic neurones, with no cardiac rhythmicity, that increased their spontaneous discharge during emotional arousal but not during a manoeuvre that unloads the baroreceptors. Conversely, skin sympathetic nerve activity (SSNA), recorded in four patients, 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, and that the increase in tonic firing of muscle vasoconstrictor neurones contributes to the increase in blood pressure during emotional excitement.

GOALS: : To analyze the neurochemical profile during the recurrent attacks of nausea and vomiting in patients with Riley-day syndrome. BACKGROUND: : One of the most disabling features of patients with Riley-day syndrome are recurrent attacks of severe nausea/retching/vomiting accompanied by hypertension, tachycardia, and skin flushing, usually triggered by emotional or other stresses. STUDY: : We monitored blood pressure and heart rate and measured plasma catecholamines during typical dysautonomic crises triggered by emotionally charged situations. For comparison, measurements were repeated at follow-up after the symptoms had resolved and the patients were feeling calm and well. RESULTS: : During a typical attack, patients were hypertensive and tachycardic. In all patients, circulating levels of norepinephrine (P<0.002) and dopamine (P<0.007) increased significantly. CONCLUSIONS: : Activation of dopamine receptors in the chemoreceptor trigger zone may explain the cyclic nausea/retching/vomiting of patients with Riley-day syndrome.

Riley Day syndrome, commonly referred to as familial dysautonomia (FD), is a genetic disease with extremely labile blood pressure owing to baroreflex deafferenation. Chronic renal disease is very frequent in these patients and was attributed to recurrent arterial hypotension and renal hypoperfusion. Aggressive treatment of hypotension, however, has not reduced its prevalence. We evaluated the frequency of kidney malformations as well as the impact of hypertension, hypotension and blood pressure variability on the severity of renal impairment. We also investigated the effect of fludrocortisone treatment on the progression of renal disease. Patients with FD appeared to have an increased incidence of hydronephrosis/reflux and patterning defects. Patients <4 years old had hypertension and normal estimated glomerular filtration rates (eGFR). Patients with more severe hypertension and greater variability in their blood pressure had worse renal function (both, P<0.01). In contrast, there was no relationship between eGFR and the lowest blood pressure recorded during upright tilt. The progression of renal disease was faster in patients receiving fludrocortisone (P<0.02). Hypertension precedes kidney disease in these patients. Moreover, increased blood pressure variability as well as mineralocorticoid treatment accelerate the progression of renal disease. No association was found between hypotension and renal disease in patients with FD.Journal of Human Hypertension advance online publication, 1 December 2011; doi:10.1038/jhh.2011.107

OBJECTIVE: To develop a reliable rating scale to assess functional capacity in children with familial dysautonomia, evaluate changes over time, and determine whether severity within a particular functional category at a young age affected survival. STUDY DESIGN: Ten functional categories were retrospectively assessed in 123 patients with familial dysautonomia at age 7 years +/- 6 months. Each of the 10 Functional Severity Scale categories (motor development, cognitive ability, psychological status, expressive speech, balance, oral coordination, frequency of dysautonomic crisis, respiratory, cardiovascular, and nutritional status) were scored from 1 (worst or severely affected) to 5 (best or no impairment). Changes over time were analyzed further in 22 of the 123 patients who were also available at ages 17 and 27 years. RESULTS: Severely impaired cardiovascular function and high frequency of dysautonomic crisis negatively affected survival (P < .005 and P < .001, respectively). In the 22 individuals followed up to age 27 years, psychological status significantly worsened (P = .01), and expressive speech improved (P = .045). From age 17 to 27 years, balance worsened markedly (P = .048). CONCLUSION: The Functional Severity Scale is a reliable tool to measure functional capacity in patients with familial dysautonomia. The scale may prove useful in providing prognosis and as a complementary endpoint in clinical trials.

Drinking pure water markedly increases blood pressure in patients with chronic autonomic failure because water-induced hypo-osmolarity, sensed by peripheral osmoreceptors, triggers sympatho-excitation likely arising from a spinal mechanism. Osmosensory transduction involves transient receptor potential vanilloid 4 channels (TRPV4) expressed on afferent neurons with their cell bodies in the dorsal root ganglia (delta;RG). Patients with familial dysautonomia (FD, hereditary sensory and autonomic neuropathy type-III) have a reduced number of afferent neurons in the DRG. The aim of our study was to investigate whether a pronounced osmopressor responsewas also present in patientswith FD. Nine patients withFDand 6with chronic autonomic failure participated in this study (5 with MSA and 1 with PAF). Beat-to-beat BP was recorded in a supine position before and following the ingestion of 500 ml of room temperature water for 30 min. As expected, in patients with autonomic failure, mean blood pressure (MBP) increased significantly after water ingestion (from 104 +/- 13 to 128 +/- 20 mmHg, p<0.05, max response 19 +/- 9 mmHg, p<0.01). In contrast, in patients with FD, water ingestion did not increase MBP significantly over the 30 min period (90 +/- 13 to 94 +/- 13 mmHg, NS, max response 7 +/- 11 mmHg, NS,). Thus, the response to water drinking differed significantly between the two groups (2-way ANOVA: p<0.0001). These findings suggest an absence of functional peripheral osmoreceptors in FD patients and may have therapeutic implications

BACKGROUND: In patients with familial dysautonomia (FD), prominent orthostatic hypotension (OH) endangers cerebral perfusion. Supine repositioning or abdominal compression improves systolic and diastolic blood pressure (BPsys and BPdia). OBJECTIVE: To determine whether OH recovers faster with combined supine repositioning and abdominal compression than with supine repositioning alone. METHODS: In 9 patients with FD (17.8 +/- 3.9 years) and 10 healthy controls (18.8 +/- 5 years), we assessed 2-min averages of BPsys, BPdia, and heart rate (HR) during supine rest, standing, supine repositioning, another supine rest, second standing, and supine repositioning with abdominal compression by leg elevation and flexion. We determined BPsys- and BPdia-recovery-times as intervals from return to supine until BP reached values equivalent to each participant's 2-min average at supine rest minus two standard deviations. Differences in signal values and BP-recovery-times between groups and positions were assessed by ANOVA and post hoc testing (significance: P < 0.05). RESULTS: Patients with FD had pronounced OH that improved with supine repositioning. However, BP only reached supine rest values with additional abdominal compression. In controls, BP was stable during positional changes. Without abdominal compression, BP-recovery-times were longer in patients with FD than those in controls, but similar to control values with compression (BPsys: 83.7 +/- 64.1 vs 36.6 +/- 49.5 s; P = 0.013; BPdia: 84.6 +/- 65.2 vs 35.3 +/- 48.9 s; P = 0.009). CONCLUSION: Combining supine repositioning with abdominal compression significantly accelerates recovery from OH and thus lowers the risk of hypotension-induced cerebral hypoperfusion.

In 4 infants with a new lethal autonomic sensory neuropathy with clinical features similar to familial dysautonomia as well as contractures, we identified a deleterious mutation in the DST gene, using homozygosity mapping followed by exome sequencing. DST encodes dystonin, a cytoskeleton linker protein, and the mutation results in an unstable transcript. Interestingly, dystonin is significantly more abundant in cells of familial dysautonomia patients with IKBKAP (I-kappa-B kinase complex-associated protein) mutation compared to fibroblasts of controls, suggesting that upregulation of dystonin is responsible for the milder course in familial dysautonomia. Homozygosity mapping followed by exome sequencing is a successful approach to identify mutated genes in rare monogenic disorders. Ann Neurol 2012;71:569-572.

BACKGROUND:: To define the clinical neuro-ophthalmic abnormalities of patients with familial dysautonomia (FD). METHODS:: Sixteen patients (32 eyes) with the clinical and molecular diagnoses of FD underwent thorough neuro-ophthalmic clinical evaluation. RESULTS:: Visual acuity ranged from 0.05 to 1.0 decimal units and was reduced in 15 of 16 patients. Mild to moderate corneal opacities were found in most patients but were visually significant in only 2 eyes. Red-green color vision was impaired in almost all cases. Depression of the central visual fields was present on automated visual fields in all patients, even in those with normal visual acuity. Temporal optic nerve pallor was present in all cases and was associated with retinal nerve fiber layer loss in the papillomacular region. Various ocular motility abnormalities also were observed. CONCLUSION:: Patients with FD have a specific type of optic neuropathy with predominant loss of papillomacular nerve fibers, a pattern similar to other hereditary optic neuropathies caused by mutations either in nuclear or in mitochondrial DNA, affecting mitochondrial protein function. Defects of eye movements, particularly saccades, also appear to be a feature of patients with FD