Trophic functions of the neuron. V. Familial dysautonomis. Current concepts of dysautonomia: neuropathological defects

Autonomic failure: Clinicopathologic, physiologic, and genetic aspects

Over the past century, generations of neuroscientists, pathologists, and clinicians have elucidated the underlying causes of autonomic failure found in neurodegenerative, inherited, and antibody-mediated autoimmune disorders, each with pathognomonic clinicopathologic features. Autonomic failure affects central autonomic nervous system components in the α-synucleinopathy, multiple system atrophy, characterized clinically by levodopa-unresponsive parkinsonism or cerebellar ataxia, and pathologically by argyrophilic glial cytoplasmic inclusions (GCIs). Two other central neurodegenerative disorders, pure autonomic failure characterized clinically by deficits in norepinephrine synthesis and release from peripheral sympathetic nerve terminals; and Parkinson's disease, with early and widespread autonomic deficits independent of the loss of striatal dopamine terminals, both express Lewy pathology. The rare congenital disorder, hereditary sensory, and autonomic neuropathy type III (or Riley-Day, familial dysautonomia) causes life-threatening autonomic failure due to a genetic mutation that results in loss of functioning baroreceptors, effectively separating afferent mechanosensing neurons from the brain. Autoimmune autonomic ganglionopathy caused by autoantibodies targeting ganglionic α3-acetylcholine receptors instead presents with subacute isolated autonomic failure affecting sympathetic, parasympathetic, and enteric nervous system function in various combinations. This chapter is an overview of these major autonomic disorders with an emphasis on their historical background, neuropathological features, etiopathogenesis, diagnosis, and treatment.

Neonatal and infantile hypotonia

The underlying etiology of neonatal and infantile hypotonia can be divided into primary peripheral and central nervous system and acquired or genetic disorders. The approach to identifying the likeliest cause of hypotonia begins with a bedside assessment followed by a careful review of the birth history and early development and family pedigree and obtaining available genetic studies and age- and disease-appropriate laboratory investigations. Until about a decade ago, the main goal was to identify the clinical signs and a battery of basic investigations including electrophysiology to confirm or exclude a given neuromuscular disorder, however the availability of whole-exome sequencing and next generation sequencing and transcriptome sequencing has simplified the identification of specific underlying genetic defect and improved the accuracy of diagnosis in many related Mendelian disorders.

Nutritional Implications of Patients with Dysautonomia and Hypermobility Syndromes

PURPOSE OF REVIEW

Dysautonomia and hypermobility syndrome are two distinct but often overlapping clinical conditions that are recognized for their complex multiorgan system afflictions. The purpose of this review is to investigate dietary strategies to reduce symptoms and augment quality of life in this growing patient population.

RECENT FINDINGS

There is increasing evidence supporting dietary modifications to include food rich in probiotics and prebiotics, along with fiber supplements to reduce gastrointestinal symptoms. Adequate salt and fluid intake may reduce orthostatic hypotension symptoms. Dietary supplements may help with osteoarticular, musculoskeletal, and fatigue symptoms. Individualized diet strategies and supplements can reduce the multiorgan system symptoms observed in dysautonomia and hypermobility syndrome.

Obstructive Sleep-Disordered Breathing Is More Common than Central in Mild Familial Dysautonomia

STUDY OBJECTIVES

In familial dysautonomia (FD) patients, sleep-disordered breathing (SDB) might contribute to their high risk of sleep-related sudden death. Prevalence of central versus obstructive sleep apneas is controversial but may be therapeutically relevant. We, therefore, assessed sleep structure and SDB in FD-patients with no history of SDB.

METHODS

11 mildly affected FD-patients (28 ± 11 years) without clinically overt SDB and 13 controls (28 ± 10 years) underwent polysomnographic recording during one night. We assessed sleep stages, obstructive and central apneas (≥ 90% air flow reduction) and hypopneas (> 30% decrease in airflow with ≥ 4% oxygen-desaturation), and determined obstructive (oAI) and central (cAI) apnea indices and the hypopnea index (HI) as count of respective apneas/hypopneas divided by sleep time. We obtained the apnea-hypopnea index (AHI4%) from the total of apneas and hypopneas divided by sleep time. We determined differences between FD-patients and controls using the U-test and within-group differences between oAIs, cAIs, and HIs using the Friedman test and Wilcoxon test.

RESULTS

Sleep structure was similar in FD-patients and controls. AHI4% and HI were significantly higher in patients than controls. In patients, HIs were higher than oAIs and oAIs were higher than cAIs. In controls, there was no difference between HIs, oAIs, and cAIs. Only patients had apneas and hypopneas during slow wave sleep.

CONCLUSIONS

In our FD-patients, obstructive apneas were more common than central apneas. These findings may be related to FD-specific pathophysiology. The potential ramifications of SDB in FD-patients suggest the utility of polysomnography to unveil SDB and initiate treatment.

COMMENTARY

A commentary on this article appears in this issue on page 1583.

Involvement of IKAP in peripheral target innervation and in specific JNK and NGF signaling in developing PNS neurons

A splicing mutation in the ikbkap gene causes Familial Dysautonomia (FD), affecting the IKAP protein expression levels and proper development and function of the peripheral nervous system (PNS). Here we attempted to elucidate the role of IKAP in PNS development in the chick embryo and found that IKAP is required for proper axonal outgrowth, branching, and peripheral target innervation. Moreover, we demonstrate that IKAP colocalizes with activated JNK (pJNK), dynein, and β-tubulin at the axon terminals of dorsal root ganglia (DRG) neurons, and may be involved in transport of specific target derived signals required for transcription of JNK and NGF responsive genes in the nucleus. These results suggest the novel role of IKAP in neuronal transport and specific signaling mediated transcription, and provide, for the first time, the basis for a molecular mechanism behind the FD phenotype.

Relationship between proprioception at the knee joint and gait ataxia in HSAN III

BACKGROUND

Hereditary sensory and autonomic neuropathy type III features marked ataxic gait that progressively worsens over time. We assessed whether proprioceptive disturbances can explain the ataxia.

METHODS

Proprioception at the knee joint was assessed using passive joint angle matching in 18 patients and 14 age-matched controls; 5 patients with cerebellar ataxia were also studied. Ataxia was quantified using the Brief Ataxia Rating Score, which ranged from 7 to 26 of 30.

RESULTS

Neuropathy patients performed poorly in judging joint position: mean absolute error was 8.7° ± 1.0°, and the range was very wide (2.8°-18.1°); conversely, absolute error was only 2.7° ± 0.3° (1.6°-5.5°) in the controls and 3.0° ± 0.2° (2.1°-3.4°) in the cerebellar patients. This error was positively correlated to the degree of ataxia in the neuropathy patients but not the cerebellar patients.

CONCLUSIONS

These results suggest that poor proprioceptive acuity at the knee joint is a major contributor to the ataxic gait associated with hereditary sensory and autonomic neuropathy type III.

Cardiac-locked bursts of muscle sympathetic nerve activity are absent in familial dysautonomia

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.

Combined counter-maneuvers accelerate recovery from orthostatic hypotension in familial dysautonomia

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.

Can loss of muscle spindle afferents explain the ataxic gait in Riley-Day syndrome?

The Riley-Day syndrome is the most common of the hereditary sensory and autonomic neuropathies (Type III). Among the well-recognized clinical features are reduced pain and temperature sensation, absent deep tendon reflexes and a progressively ataxic gait. To explain the latter we tested the hypothesis that muscle spindles, or their afferents, are absent in hereditary sensory and autonomic neuropathy III by attempting to record from muscle spindle afferents from a nerve supplying the leg in 10 patients. For comparison we also recorded muscle spindles from 15 healthy subjects and from two patients with hereditary sensory and autonomic neuropathy IV, who have profound sensory disturbances but no ataxia. Tungsten microelectrodes were inserted percutaneously into fascicles of the common peroneal nerve at the fibular head. Intraneural stimulation within muscle fascicles evoked twitches at normal stimulus currents (10-30 µA), and deep pain (which often referred) at high intensities (1 mA). Microneurographic recordings from muscle fascicles revealed a complete absence of spontaneously active muscle spindles in patients with hereditary sensory and autonomic neuropathy III; moreover, responses to passive muscle stretch could not be observed. Conversely, muscle spindles appeared normal in patients with hereditary sensory and autonomic neuropathy IV, with mean firing rates of spontaneously active endings being similar to those recorded from healthy controls. Intraneural stimulation within cutaneous fascicles evoked paraesthesiae in the fascicular innervation territory at normal stimulus intensities, but cutaneous pain was never reported during high-intensity stimulation in any of the patients. Microneurographic recordings from cutaneous fascicles revealed the presence of normal large-diameter cutaneous mechanoreceptors in hereditary sensory and autonomic neuropathy III. Our results suggest that the complete absence of functional muscle spindles in these patients explains their loss of deep tendon reflexes. Moreover, we suggest that their ataxic gait is sensory in origin, due to the loss of functional muscle spindles and hence a compromised sensorimotor control of locomotion.

Modelling familial dysautonomia in human induced pluripotent stem cells

Induced pluripotent stem (iPS) cells have considerable promise as a novel tool for modelling human disease and for drug discovery. While the generation of disease-specific iPS cells has become routine, realizing the potential of iPS cells in disease modelling poses challenges at multiple fronts. Such challenges include selecting a suitable disease target, directing the fate of iPS cells into symptom-relevant cell populations, identifying disease-related phenotypes and showing reversibility of such phenotypes using genetic or pharmacological approaches. Finally, the system needs to be scalable for use in modern drug discovery. Here, we will discuss these points in the context of modelling familial dysautonomia (FD, Riley-Day syndrome, hereditary sensory and autonomic neuropathy III (HSAN-III)), a rare genetic disorder in the peripheral nervous system. We have demonstrated three disease-specific phenotypes in FD-iPS-derived cells that can be partially rescued by treating cells with the plant hormone kinetin. Here, we will discuss how to use FD-iPS cells further in high throughput drug discovery assays, in modelling disease severity and in performing mechanistic studies aimed at understanding disease pathogenesis. FD is a rare disease but represents an important testing ground for exploring the potential of iPS cell technology in modelling and treating human disease.

Neuroimaging supports central pathology in familial dysautonomia

Familial dysautonomia (FD) is a hereditary peripheral and central nervous system disorder with poorly defined central neuropathology. This prospective pilot study aimed to determine if MRI would provide objective parameters of central neuropathology. There were 14 study subjects, seven FD individuals (18.6 +/- 4.2 years, 3 female) and seven controls (19.1 +/- 5.8 years, 3 female). All subjects had standardized brain MRI evaluation including quantitative regional volume measurements, diffusion tensor imaging (DTI) for assessment of white matter (WM) microstructural integrity by calculation of fractional anisotropy (FA), and proton MR spectroscopy ((1)H MRS) to assess neuronal health. The FD patients had significantly decreased FA in optic radiation (p = 0.009) and middle cerebellar peduncle (p = 0.004). Voxel-wise analysis identified both GM and WM microstructural damage among FD subjects as there were nine clusters of WM FA reductions and 16 clusters of GM apparent diffusion coefficient (ADC) elevations. Their WM proportion was significantly decreased (p = 0.003) as was the WM proportion in the frontal region (p = 0.007). (1)H MRS showed no significant abnormalities. The findings of WM abnormalities and decreased optic radiation and middle cerebellar peduncle FA in the FD study group, suggest compromised myelination and WM micro-structural integrity in FD brains. These neuroimaging results are consistent with clinical visual abnormalities and gait disturbance. Furthermore the frontal lobe atrophy is consistent with previously reported neuropsychological deficits.

Pregabalin: a new approach to treatment of the dysautonomic crisis

Nausea and dysautonomic crises severely limit function and quality of life for a large number of individuals with familial dysautonomia. We treated a small cohort of 15 patients with familial dysautonomia who suffered frequent dysautonomic crises with pregabalin. Nausea and overt crises markedly decreased in 13 (87%) of these patients and the overall assessments of benefit were extremely favorable, suggesting that pregabalin may be a potentially useful therapeutic agent for this disorder.

Current approaches to development of the autonomic nervous system: clues to clinical problems

A number of different approaches to autonomic development utilizing a variety of experimental models and analytical techniques have been outlined. A scheme, which attempts to delineate a series of events involving separate but sometimes overlapping mechanisms, is proposed for the complex process of formation and maintenance of functional autonomic neuroeffector junctions. The relevance of these basic mechanisms of a variety of clinical abnormalities of autonomic function is discussed.

Defects in tongue papillae and taste sensation indicate a problem with neurotrophic support in various neurological diseases

Neurotrophic support of developing neurons by neurotrophins is of critical importance in the development of fungiform papillae and taste buds. A number of neurological disorders show a decrease or increase in fungiform papillae or taste sensation. These can be grouped into disorders with reduced papillae (Machado-Joseph disease, Stüve-Wiedemann syndrome, familial dysautonomia, dystonia musculorum, and Behçet's disease) and those with taste defects only (Alzheimer's disease, Huntington's disease, hereditary sensory and autonomic neuropathy type IV, and diabetes mellitus). In addition, Parkinson's disease results in increased taste sensation. Here, we hypothesize that the main problem in these disorders is either not enough or too much neurotrophic support. Proneurotrophic drugs such as some antidepressants and aldose reductase inhibitors may prove useful in the treatment of these sensory and central nervous system disorders. Similarly, antineurotrophic drugs may also be useful in Parkinson's disease. Here we show that the protein involved in familial dysautonomia, IKAP, localizes to keratin filaments in HeLa cells, suggesting a role for the keratin cytoskeleton in neurotrophic support.

The molecular basis of familial dysautonomia: overview, new discoveries and implications for directed therapies

Familial dysautonomia (FD) is a sensory and autonomic neuropathy that affects the development and survival of sensory, sympathetic, and some parasympathetic neurons. It is autosomally inherited and occurs almost exclusively among individuals of Ashkenazi Jewish descent. The pathological and clinical manifestations of FD have been extensively studied and therapeutic modalities have, until recently, focused primarily on addressing the symptoms experienced by those with this fatal disorder. The primary FD-causing mutation is an intronic nucleotide substitution that alters the splicing of the IKBKAP-derived transcript. Recent efforts have resulted in the development of new therapeutic modalities that facilitate the increased production of the correctly spliced transcript and mitigate the symptoms of those with FD. Furthermore, the recent demonstration of the reduced presence of monoamine oxidase A in cells and tissues of individuals with FD has provided new insight into the cause of hypertensive crises experienced by these patients.

Hereditary sensory and autonomic neuropathies: types II, III, and IV

The hereditary sensory and autonomic neuropathies (HSAN) encompass a number of inherited disorders that are associated with sensory dysfunction (depressed reflexes, altered pain and temperature perception) and varying degrees of autonomic dysfunction (gastroesophageal reflux, postural hypotention, excessive sweating). Subsequent to the numerical classification of four distinct forms of HSAN that was proposed by Dyck and Ohta, additional entities continue to be described, so that identification and classification are ongoing. As a group, the HSAN are rare diseases that affect both sexes. HSAN III is almost exclusive to individuals of Eastern European Jewish extraction, with incidence of 1 per 3600 live births. Several hundred cases with HSAN IV have been reported. The worldwide prevalence of HSAN type II is very low. This review focuses on the description of three of the disorders, HSAN II through IV, that are characterized by autosomal recessive inheritance and onset at birth. These three forms of HSAN have been the most intensively studied, especially familial dysautonomia (Riley-Day syndrome or HSAN III), which is often used as a prototype for comparison to the other HSAN. Each HSAN disorder is likely caused by different genetic errors that affect specific aspects of small fiber neurodevelopment, which result in variable phenotypic expression. As genetic tests are routinely used for diagnostic confirmation of HSAN III only, other means of differentiating between the disorders is necessary. Diagnosis is based on the clinical features, the degree of both sensory and autonomic dysfunction, and biochemical evaluations, with pathologic examinations serving to further confirm differences. Treatments for all these disorders are supportive.

A world without pain or tears

The world of the child with familial dysautonomia (FD), a genetic disorder affecting development of the sensory and autonomic nervous system, is not idyllic. However, over the last 35 years advances in supportive treatments have improved morbidity and mortality. Recent genetic breakthroughs have further expanded thinking about this disorder and suggested innovative approaches to modifying genetic expression. This article reviews the current supportive treatment modalities and their rationale, as well as the suggested new treatments that may alter the function and prognosis of an individual affected with FD.

Prevalence and Severity of Renal Disease in Familial Dysautonomia

BACKGROUND

One of the less well-defined complications of familial dysautonomia (FD) is chronic kidney disease (CKD). The goal of this report is to better define the prevalence and severity of kidney disease in this population and identify associated risk factors.

METHODS

We conducted a retrospective analysis of the database of the Dysautonomia Treatment and Evaluation Center at New York University School of Medicine for patients with FD who were seen at ages 15, 20, 25, 30, 35, and 40 years. Estimated glomerular filtration rate (GFR) was compared with that of the general population. Changes in mean blood pressure from supine to erect at ages 15 and 20 years were analyzed for patients who eventually required dialysis therapy and compared with those of the other patients with FD. Percentage of patients requiring dialysis and duration of treatment also were analyzed.

RESULTS

Mean estimated GFR of each predefined age group was considerably less than that of the general population starting at age 15 years (P < 0.001). Patients with FD were more likely to develop stage 3, 4, or 5 CKD than the general population. Of patients who remained alive at age 25 years, 19% eventually required dialysis. Those who required dialysis therapy were less likely to have had a feeding gastrostomy tube placed (P < 0.001) and had much more pronounced postural changes in blood pressure (P < 0.0001) by age 15 years. For those requiring dialysis therapy, average duration of treatment was 9 months.

CONCLUSION

Patients with FD are far more likely than the general population to develop CKD. Patients with FD who eventually required dialysis showed a greater degree of orthostatic hypotension and were significantly less likely to have had a feeding gastrostomy tube placed for hydration before the age of 15 years. Dialysis therapy is not well tolerated in this population.

Anesthesia management of familial dysautonomia

Familial dysautonomia (FD) is an autosomal recessive inherited disorder, predominantly affecting the Ashkenazi Jewish population that is characterized by sensory and autonomic neuropathy. The protean manifestations and perturbations result in high morbidity and mortality. However, as a result of supportive measures and centralized care, survival has improved. As surgical options are increasing to symptomatically treat FD, anesthesiologists need to be familiar with this disorder. Because the Dysautonomia Center at NYU Medical Center is a referral center for FD patients, we have attained considerable anesthetic experience with FD. This article reviews clinical features of FD that could potentially affect anesthetic management and outlines our present practices.

Tocotrienols reverse IKAP and monoamine oxidase deficiencies in familial dysautonomia

Familial dysautonomia (FD), a recessive neurodegenerative disease, is caused by mutations in the IKBKAP gene that result in the production of nonfunctional IKAP protein. Manifestations of FD include autonomic crises characterized by hypertension, tachycardia, diaphoresis, and vomiting. Elevated plasma levels of norepinephrine (NE) and dopamine observed during autonomic crises and an exaggerated hypertensive response to low doses of NE prompted an examination of monoamine oxidase (MAO) levels, key isoenzymes responsible for degrading biogenic and dietary monoamines, in individuals with FD. Fetal tissue homozygous for the common FD-causing mutation and peripheral blood cells of individuals with FD have reduced MAO A mRNA levels. FD-derived cells, stimulated with tocotrienols or EGCG to produce increased levels of functional IKAP, express increased amounts of MAO A mRNA transcript and protein. Administration of tocotrienol to individuals with FD results in increased expression of both functional IKAP and MAO A transcripts in their peripheral blood cells. These findings provide new insight into the pathophysiology of FD and demonstrate the value of therapeutic approaches designed to elevate cellular levels of functional IKAP and MAO A.

Fludrocortisone in patients with familial dysautonomia--assessing effect on clinical parameters and gene expression

The common familial dysautonomia (FD) mutation causes a splicing defect that leads to production of both wild-type (WT) and mutant (MU) IKBKAP mRNA. Because drugs may alter splicing, seven drugs, fludrocortisone, midodrine, diazepam, albuterol, clonidine, caffeine, and dopamine were screened. Since only fludrocortisone negatively altered gene expression, we assessed fludrocortisone's efficacy in treating postural hypotension, and its effect on survival and secondary long-term FD problems. For 341 FD patients we obtained demographic data and clinical information from the last Center evaluation (most current or prior to death) including mean blood pressures (supine, 1 min erect and 5 min erect) and history regarding syncope and presyncope symptoms. For 175 fludrocortisone-treated patients, data from the evaluation prior to start of fludrocortisone and from the last Center evaluation were compared. The fludrocortisone-treated patient cohort was compared to the nontreated patient cohort with respect to overall survival and event-free survival for crisis frequency, worsening gait, frequent fractures, spine curvature, renal insufficiency, and pacemaker insertion. Overall survivals of patients on fludrocortisone alone, on fludrocortisone and midodrine, and on neither drug were compared. Cumulative survival was significantly higher in fludrocortisone-treated patients than in non-treated patients during the first decade. In subsequent decades, the addition of midodrine improved cumulative survival. Fludrocortisone significantly increased mean blood pressures and decreased dizziness and leg cramping, but not headaches or syncope. Fludrocortisone was associated with more long-term problems, which may reflect more symptomatic status associated with longer survival. Our data suggest that fludrocortisone has clinical efficacy despite negative in vitro observations on gene expression.

Pacemakers in patients with familial dysautonomia--a review of experience with 20 patients

Familial dysautonomia (FD) is a genetic disease associated with a high incidence of sudden death. If fatal bradyarrhythmia is an etiological factor then the incidence of sudden death should decrease after pacemaker placement. Retrospective review of 596 registered FD patients revealed that 22 FD patients (3.7%) had pacemakers placed between December 1984 and June 2003. Clinical and electrocardiographic indications for placement and demographic data were assessed for 20 of the 22 patients (10 males, 10 females, ages 4 to 48 years). Two patients were excluded because of insufficient data. Prior to pacemaker placement, presenting symptoms were syncope and cardiac arrest, 16/20 (80%) and 6/20 (30 %), respectively. Asystole was the most frequent electrocardiographic finding and was documented in 17/20 patients (85 %). Other electrocardiographic abnormalities included bradycardia, AV block, prolonged QTc and prolonged JTc. The average duration of pacemaker utilization was 5.7 years (range 5 months to 14.5 years). Complications included infection (1 patient) and wire migration (2 patients). In the one patient with infection, the pacemaker was permanently removed. This patient then experienced multiple syncopal episodes and death. There were 7 other deaths. Three deaths occurred suddenly without preceding events, and 4 patients had non-cardiac causes of death. None of these 7 deceased patients had recurrence of syncope after pacemaker placement. In the 12 surviving patients, 6 had recurrence of syncope but none had cardiac arrest. Pacemaker placement may protect FD patients from fatal bradyarrhythmia and may decrease the incidence of syncope. However, data are limited and prospective analysis is needed.

Gastroesophageal reflux in familial dysautonomia: correlation with crisis frequency and sensory dysfunction

OBJECTIVES

Familial dysautonomia (FD), a genetic disorder resulting in sensory and autonomic nervous system dysfunction, is associated with a high frequency of gastroesophageal reflux (GER). In this study the authors attempted to determine if GER prevalence correlated with dysautonomic crisis frequency and small fiber sensory dysfunction.

METHODS

Of an initial population of 252 FD patients who had survived past their seventh year and were alive during the year of study from June 1, 2001 to June 1, 2002, 174 (69.0%) had sufficient data in their patient files to be included in this retrospective analysis. Subjects were stratified into three groups: those with no GER, those medically treated for GER and those surgically treated for GER with fundoplication. Data were obtained regarding frequency and severity of dysautonomic crises and sensory function including pain sensation, cold and warm thresholds and vibration perception.

RESULTS

There were no significant differences among the three groups regarding age or severity of sensory dysfunction. However, dysautonomic crises were significantly more frequent in FD patients who were presumed to have more intractable GER, as they had required fundoplication (P < 0.05).

CONCLUSIONS

The data confirm the high incidence of GER in the FD population and demonstrate that GER is independent of severity of sensory dysfunction. In addition, the authors demonstrate that fundoplication does not alleviate the central autonomic cause of retching, the dysautonomic crisis.

Familial dysautonomia

Familial dysautonomia (FD) is a neurodevelopmental genetic disorder within the larger classification of hereditary sensory and autonomic neuropathies, each caused by a different genetic error. The FD gene has been identified as IKBKAP. Mutations result in tissue-specific expression of mutant IkappaB kinase-associated protein (IKAP). The genetic error probably affects development, as well as maintenance, of neurons because there is neuropathological and clinical progression. Pathological alterations consist of decreased unmyelinated and small-fiber neurons. Clinical features reflect widespread involvement of sensory and autonomic neurons. Sensory loss includes impaired pain and temperature appreciation. Autonomic features include dysphagia, vomiting crises, blood pressure lability, and sudomotor dysfunction. Central dysfunction includes emotional lability and ataxia. With supportive treatment, prognosis has improved greatly. About 40% of patients are over age 20 years. The cause of death is usually pulmonary failure, unexplained sudden deaths, or renal failure. With the discovery of the genetic defect, definitive treatments are anticipated.

Survival in familial dysautonomia: Impact of early intervention

OBJECTIVE

To assess the effectiveness of advances in supportive centralized care on survival and function in patients with familial dysautonomia (FD).

STUDY DESIGN

From September l, 1969 through January 1, 2001. Five hundred fifty-one patients with FD entered the Dysautonomia Center. We divided the group into two cohorts: the first cohort (n = 227) entered until March 1, 1981, and the second cohort (n = 324) entered after March 1, 1981. Survival curves were compared by using log-rank tests. Demographic and disease characteristics were examined, including gender, geographic location, age at entry, birth weight, breath-holding history, age of walking, causes of death, and social data.

RESULTS

For both cohorts age at entry was the primary variable that influenced survival; mortality increased by 3% per year. Survival time lengthened for cohort 2 when survival time was defined as time from entry into the Center to last observation or death; in cohort 2, mortality was 73% that of cohort 1 even after adjustment for age at entry. Although survival improved, causes of death were unchanged; sleep deaths and sudden deaths remained frequent.

CONCLUSION

Our data indicate that the more recent cohort patients were younger at the time of entry and had improved survival, which suggests that early access to centralized and more advanced treatment appreciably benefits patients with familial dysautonomia.

Dermal microdialysis provides evidence for hypersensitivity to noradrenaline in patients with familial dysautonomia

OBJECTIVES

To use the technique of dermal microdialysis to examine sensitivity of skin vessels to noradrenaline (NA) in patients with familial dysautonomia (FD) and in healthy controls.

METHODS

In 14 patients with FD and 12 healthy controls, plasma extravasation, local laser Doppler blood flow, and skin blanching were observed before, during, and after application of 10(-6) M NA through a microdialysis membrane, located intradermally in the skin of the lower leg.

RESULTS

Maximum local vasoconstriction measured by laser Doppler blood flow did not differ between patients with FD and controls. In contrast, patients with FD had an earlier onset of vasoconstriction (p = 0.02). Moreover, reaction to NA was more prominent and prolonged in FD, shown by a larger zone of skin blanching around the microdialysis membrane (p < 0.001) and delayed reduction of the protein content in the dialysate after termination of NA application (p = 0.03).

CONCLUSION

These data support the hypothesis that peripheral blood vessels of patients with FD show a denervation hypersensitivity to catecholamines. This may be one mechanism contributing to the major hypertension that frequently occurs during "dysautonomic crises" in FD.

Cold pressor test demonstrates residual sympathetic cardiovascular activation in familial dysautonomia

In familial dysautonomia (FD), i.e. Riley-Day-syndrome, sympathetic cardiovascular function, as well as afferent temperature and pain mediating neurons, are significantly reduced. Thus, it was questioned if cold pressor test (CPT), which normally enhances sympathetic outflow and induces peripheral vasoconstriction by the activation of thermo- and nociceptive system activation, could be used to assess sympathetic function in FD. To evaluate whether CPT can be used to assess sympathetic activation in FD, we performed CPT in 15 FD patients and 18 controls. After a 35-min resting period, participants immersed their right hand and arm up to the elbow into 0-1 degrees C cold water while we monitored heart rate (HR), respiration, beat-to-beat radial artery blood pressure (BP), and laser Doppler skin blood flow (SBF) at the right index finger pulp. From these measurements, heart rate variability parameters were calculated: root mean square of successive differences (RMSSD), coefficient of variation (CV), low and high frequency (LF, HF) power spectra of the electrocardiogram (ECG). All participants perceived cold stimulation and indicated discomfort. In controls, SBF decreased and HR and BP increased rapidly upon CPT. After 60 s, SBF indicated secondary vasodilatation in six controls, BP rise attenuated and HR returned to baseline in all controls. In the patients, SBF remained unchanged, HR and BP increased significantly, but after 50-60 s of CPT and changes were lower than in controls (p<0.05). RMSSD and CV decreased and LF increased significantly only in the controls. We conclude that CPT activates sympathetic HR and BP modulation despite impaired pain and temperature perception in FD patients. BP increase in the presence of almost unchanged SBF might be due to HR increase and to nociceptive arousal and emotionally induced catecholamine release as seen in emotional crises of FD patients. CPT assesses sympathetic cardiovascular responses independently from baroreflex function, which is compromised in FD.

Sympathetic and parasympathetic pupillary dysfunction in familial dysautonomia

Objective assessment of autonomic dysfunction in familial dysautonomia (FD) is largely based on the analysis of cardiovascular responses to challenge maneuvers such as orthostatic stress. Infrared pupillometry (IPM) provides an additional reliable method for cranial autonomic evaluation and has the advantage of requiring minimal cooperation.This study was performed to determine whether IPM contributes to the assessment of autonomic function in FD patients. In 14 FD patients and 14 healthy controls, we studied absolute and relative light reflex amplitude, pupillary constriction velocity (v(constr)), pupillary diameter, early and late pupillary re-dilatation velocity (v(dil 1), v(dil 2)) after dark adaptation. Prior to IPM, all patients had an ophthamological examination to evaluate refraction and corneal integrity. In comparison to controls, patients had a significant reduction of the parameters reflecting parasympathetic pupillary function (absolute light reflex amplitude 1.34 +/- 0.21 vs. l.86 +/- 0.14 mm, relative light reflex amplitude 22.74 +/- 7.11% vs. 30.76 +/- 3.57%, v(constr) 3.75 +/- 1.09 vs. 5.80 +/- 0.59 mm/s) and of the parameters reflecting sympathetic pupillary function (diameter 5.69 +/- 0.66 vs. 6.35 +/- 0.60 mm, v(dil 1) 1.29 +/- 0.23 vs. 1.95 +/- 0.23 mm/s, v(dil 2) 0.64 +/- 0.13 vs. 0.72 +/- 0.l2 mm/s; Mann-Whitney U-test: p<0.05). The non-invasive technique of IPM demonstrates dysfunction not only of the cranial parasympathetic, but also of the cranial sympathetic nervous system and, thus, further characterizes autonomic dysfunction in FD.

Quantitative sensory testing of thermal and vibratory perception in familial dysautonomia

Familial dysautonomia (FD) is an inherited disorder that is known to affect both sensory and autonomic functions as a result of incomplete neuronal development and progressive loss but the degree to which patients are affected differs greatly. To determine if quantitative vibration and thermal testing refined the assessment of severity, 23 familial dysautonomia patients were evaluated by clinical examination, measurements of median, peroneal and sural nerve conduction velocities (NCV), and assessment of vibration thresholds at two body sites and of warm and cold perception thresholds at 6 body sites using the method of limits. Data from 80 age-matched normal individuals provided control data for vibration and temperature thresholds. All familial dysautonomia patients had abnormal thermal thresholds. Vibration perception was abnormal in 20 patients. NCVs were slowed in 8 of 16 patients who agreed to be tested. Abnormalities in thermal thresholds are consistent with the reduction of small nerve fibers in familial dysautonomia Abnormal vibration thresholds might be due to disturbed conduction of vibratory impulse trains and reflect the degree to which the disorder is progressive. Vibration and thermal sensation testing were better accepted and provided more information than NCV regarding severity of disease.

Sympathetic skin response following thermal, electrical, acoustic, and inspiratory gasp stimulation in familial dysautonomia patients and healthy persons

To determine whether sympathetic skin response (SSR) testing evaluates afferent small or efferent sympathetic nerve fiber dysfunction, we studied SSR in patients with familial dysautonomia (FD) in whom both afferent small and efferent sympathetic fibers are largely reduced. We analyzed whether the response pattern to a combination of stimuli specific for large or small fiber activation allows differentiation between afferent and efferent small fiber dysfunction. In 52 volunteers and 13 FD patients, SSR was studied at palms and soles after warm, cold and heat as well as electrical, acoustic, and inspiratory gasp stimulation. In addition, thermal thresholds were assessed at four body sites using a Thermotest device (Somedic; Stockholm, Sweden). In volunteers, any stimulus induced reproducible SSRs. Only cold failed to evoke SSR in two volunteers. In all FD patients, electrical SSR was present, but amplitudes were reduced. Five patients had no acoustic SSR, four had no inspiratory SSR. Thermal SSR was absent in 10 patients with abnormal thermal perception and present in one patient with preserved thermal sensation. In two patients, thermal SSR was present only when skin areas with preserved temperature perception were stimulated. In patients with FD, preserved electrical SSR demonstrated the overall integrity of the SSR reflex but amplitude reduction suggested impaired sudomotor activation. SSR responses were dependent on the perception of the stimulus. In the presence of preserved electrical SSR, absent thermal SSR reflects afferent small fiber dysfunction. A combination of SSR stimulus types allows differentiation between afferent small or efferent sympathetic nerve fiber dysfunction.

Cold face test demonstrates parasympathetic cardiac dysfunction in familial dysautonomia

In familial dysautonomia (FD), i.e., Riley-Day syndrome, parasympathetic dysfunction has not been sufficiently evaluated. The cold face test is a noninvasive method of activating trigeminal brain stem cardiovagal and sympathetic pathways and can be performed in patients with limited cooperation. We performed cold face tests in 11 FD patients and 15 controls. For 60 s, cold compresses (0-1 degrees C) were applied to the cheeks and forehead while we monitored heart rate, respiration, beat-to-beat radial artery blood pressure, and laser-Doppler skin blood flow at the first toe pulp. From these measurements heart rate variability parameters were calculated: root mean square of successive differences (RMSSD), coefficient of variation (CV), low- and high-frequency (LF and HF, respectively) power spectra of the electrocardiogram, and the LF transfer function gain between blood pressure and heart rate. All patients perceived cold stimulation and acknowledged discomfort. In controls, heart rate and skin blood flow decreased significantly during cold face test; in patients, both parameters decreased only briefly and not significantly. In controls, blood pressure, RMSSD, CV, and heart rate HF-power spectra increased but remained unchanged in patients. Respiration, as well as heart rate LF power spectra, did not change in either group. In controls, LF transfer function gain between blood pressure and heart rate indicated that bradycardia was not secondary to blood pressure increase. We conclude that the cold face test demonstrated that patients with FD have a reduced cardiac parasympathetic response, which implies efferent parasympathetic dysfunction.

Sympathetic skin response differentiates hereditary sensory autonomic neuropathies III and IV

OBJECTIVE

To evaluate whether sympathetic skin response (SSR) differs in patients with hereditary sensory autonomic neuropathy (HSAN) types III and IV.

BACKGROUND

HSAN types III and IV are rare autosomal recessive disorders that cause many similar autonomic, sensory, and motor dysfunctions, but different sweating characteristics. HSAN III patients have preserved and at times, excessive sweating, whereas anhidrosis is characteristic of HSAN IV. SSR reflects the integrity of sympathetic sudomotor fibers and the activation of sweat glands through the change in skin resistance in response to an arousal stimulus. Therefore, SSR is a test method that might facilitate differential diagnosis of HSAN III and IV.

METHODS

In 17 HSAN III patients (eight women, nine men; mean age, 20.65+/-5.45 years) and seven HSAN IV patients (five girls, two boys; mean age, 10.0+/-5.45 years) SSR was recorded from the palms and soles after repeated electrical, acoustic, and inspiratory gasp stimulations. In addition, all subjects underwent a neurologic examination; studies of median, peroneal motor, and sural nerve conduction velocities; and determination of vibratory and thermal perception thresholds.

RESULTS

Although clinical differences were appreciated between the two types of HSANs, both HSANs had evidence of small-fiber involvement. Both HSANs had abnormal temperature and pain perception. In contrast, SSR was preserved in all HSAN III and absent in all HSAN IV patients.

CONCLUSION

SSR provides another parameter to improve differentiation of HSAN III from HSAN IV, and also gives us additional information regarding sympathetic sudomotor fiber function in these developmental diseases.

Electrocardiographic repolarization abnormalities in familial dysautonomia: an indicator of cardiac autonomic dysfunction

OBJECTIVE

Electrocardiographic repolarization intervals were evaluated to determine the extent of cardiac autonomic dysfunction in patients with familial dysautonomia (FD) and to determine if any of these intervals could serve as a possible predictor of clinical symptoms.

METHODS

Thirty-seven electrocardiograms of patients with FD were retrospectively evaluated. QT, JT, rate-corrected QT and JT intervals were calculated as well as QT and QTC dispersion. Results were compared to normative data and electrocardiograms of 20 age-matched control subjects.

OBSERVATIONS

In the FD group, prolongation of QTC (>450 msec) was noted in 5/37 (13.5%) patients, as compared to 0/20 normal controls (p = NS), and prolongation of JTc (>340 msec) in 16/37 (43.3%) patients, as compared to 0/20 normal controls (p < 0.001). QT and QTC dispersion were abnormal in 3/37 (8.1%) and 5/37 (13.5%), respectively. In the 16 FD patients with prolonged JTc, six had a positive history of syncope, whereas none of the 21 with normal JTc had syncope or symptoms suggesting arrhythmia (p < 0.003). The positive predictive value of having syncope or symptoms suggestive of arrhythmia with an abnormal JTc is 37.5% (95% CI [15%, 65%]). The negative predictive value is 100% (95% CI [87%, 100%]).

CONCLUSION

In the FD population, the electrocardiographic measure of repolarization that was most frequently abnormal was the JTc interval . Prolongation of the JTc interval was significantly more frequent than prolongation of the QTC interval (p < 0.001) QT and QTC dispersions were less significantly affected in the FD population, indicating uniform ventricular recovery time. These results suggest that a prolonged JTc interval may be a more sensitive indicator of abnormal ventricular repolarization and cardiac autonomic dysfunction. Due to the known sympathetic denervation inherent in patients with FD, they are at risk for unopposed parasympathetic predominance. FD patients, therefore, are more likely to have brady arrhythmias and asystole rather than polymorphic ventricular tachycardia. The increased incidence of syncope in patients with prolonged JTc suggests that this measure may serve as a helpful marker to predict which FD patients are at increased risk of serious clinical sequelae including bradyarrhythmias with asystole or sudden death.

Highly abnormal thermotests in familial dysautonomia suggest increased cardiac autonomic risk

OBJECTIVE

Patients with familial dysautonomia have an increased risk of sudden death. In some patients with familial dysautonomia, sympathetic cardiac dysfunction is indicated by prolongation of corrected QT (QTc) interval, especially during stress tests. As many patients do not tolerate physical stress, additional indices are needed to predict autonomic risk. In familial dysautonomia there is a reduction of both sympathetic neurons and peripheral small nerve fibres which mediate temperature perception. Consequently, quantitative thermal perception test results might correlate with QTc values. If this assumption is correct, quantitative thermotesting could contribute to predicting increased autonomic risk.

METHODS

To test this hypothesis, QTc intervals were determined in 12 male and eight female patients with familial dysautonomia, aged 10 to 41 years (mean 21.7 (SD 10.1) years), in supine and erect positions and postexercise and correlated with warm and cold perception thresholds assessed at six body sites using a Thermotest.

RESULTS

Due to orthostatic presyncope, six patients were unable to undergo erect and postexercise QTc interval assessment. The QTc interval was prolonged (>440 ms) in two patients when supine and in two additional patients when erect and postexercise. Supine QTc intervals correlated significantly with thermal threshold values at the six body sites and with the number of sites with abnormal thermal perception (Spearman's rank correlation p<0.05). Abnormal Thermotest results were more frequent in the four patients with QTc prolongation and the six patients with intolerance to stress tests.

CONCLUSION

The results suggest that impaired thermal perception correlates with cardiac sympathetic dysfunction in patients with familial dysautonomia. Thus thermotesting may provide an alternative, albeit indirect, means of assessing sympathetic dysfunction in autonomic disorders.

Familial dysautonomia: a 47-year perspective. How technology confirms clinical acumen

A historical perspective of familial dysautonomia is presented, highlighting the early contributions of Dr. Joseph Dancis. As further investigations proceeded, his original observations have withstood the test of time and may contribute to determining the molecular abnormality in this rare genetic disorder. Dr. Dancis's work in this area serves as a model of how observations based on clinical acumen and critical thinking can be verified by future technological advances.

Assessing microcirculation in familial dysautonomia by laser Doppler flowmeter

Microcirculatory vasomotor responses to an alpha-adrenergic agonist and an antagonist were assessed in 11 familial dysautonomia and nine control subjects by laser Doppler flowmetry. Using two iontophoresis machines, blood flow in the midclavicular areas was continuously monitored by two channel laser Doppler flowmeter. Simultaneously, the alpha-antagonist (0.5 mM phentolamine hydrochloride) and a control solution (0.9% saline) were iontophoresed at 200 microA for 15 min. The alpha-agonist (0.5 mM norepinephrine bitartrate) was then iontophoresed (20 microA) to both pretreated areas for progressively longer pulses separated by 3-min observation intervals (15, 30, 60, 90, 120 s). The familial dysautonomia subject group had higher mean baseline perfusion with widely fluctuating baselines, especially on the phentolamine pretreated side (P = 0.03). Saline iontophoresis significantly increased perfusion in the control group, but not in the familial dysautonomia group (ANOVA: P = 0.02 and 0.15, respectively). There was > 100% increase in flow by the end of the saline observation period in seven of nine controls, but in only three of 11 familial dysautonomia subjects. Phentolamine iontophoresis differentiated familial dysautonomia subjects into responders and nonresponders by 7-8 min when all nine control subjects, but only five of 11 familial dysautonomia subjects, had > 200% increase in blood flow. Irrespective of pretreatment type, norepinephrine decreased blood flow in both familial dysautonomia and control groups (ANOVA: P < 0.0001), but the final mean change after saline was greater in the control group, P = 0.02. The final mean changes of flow after phentolamine pretreatment were not different between the two groups and were comparable to the familial dysautonomia group's smaller response after saline pretreatment. Higher baseline perfusion suggests dilation may be intrinsic to familial dysautonomia vasculature. Two populations of familial dysautonomia subjects are noted; those who like controls increase blood flow with iontophoresis of the alpha-antagonist and those who are refractory. In addition, in familial dysautonomia subjects, the microcirculatory constrictive response to alpha-agonist iontophoresis is less than that observed for controls. These data suggest that some familial dysautonomia subjects may have decreased or dysfunctional adrenoceptors as well as decreased innervation.

Aspects of spinal deformity in familial dysautonomia (Riley-Day syndrome)

Familial dysautonomia (FD) is a rare autosomal recessive disease occurring in Jews of Ashkenazi descent, with only some 500 recognized cases. The causative gene was identified on chromosome 9. FD is of considerable orthopedic interest, because of the prevalence of skeletal deformity. About 90% of surviving dysautonomic children will develop a spinal curvature, commonly a scoliosis. The scoliotic curve is usually kyphotic rather than lordotic, and appears during the first decade of life. Fifty-one of the 90 reported cases of familial dysautonomia in Israel involved patients who were seen at the scoliosis clinic for assessment and treatment of their spinal deformities. Most of the patients presented with a scoliotic deformity associated in 37 cases with an increased thoracic kyphosis. In our series orthotic treatment and physiotherapy were found to be minimally successful at best. Surgical treatment of the spine was performed in 13 of 51 patients in this series. A retrospective review of these patients' charts and radiographs was carried out. Six years of follow-up are reported. The primary indication for surgery was progression of the spinal curve. Only posterior spinal fusions were performed. Anterior transthoracic procedures were avoided in spite of the significance of the kyphotic deformity, because of the frequency of pulmonary complications. Harrington distraction and compression instrumentation was used. Three-millimeter compression rods were used in a distraction mode in thin, young children. "Harri-Luque" segmental sublaminar wiring technique and Wisconsin spinous process segmental wiring was used in some. In all cases, the spine fusion was supplemented by bank bone only, to avoid the additional trauma of graft removal. We believe that surgical intervention is advantageous, if done early in the evolution of spinal deformity. Greater technical difficulties and a higher complication rate were encountered in this series relative to the problems usually seen after spinal deformity surgery in children; this is all the more important in a disease in which general anesthesia is an additional major complicating factor. It is hoped that the improved physical condition now seen after early gastrostomy and fundoplication will aid in reducing this high complication rate. Only a small degree (about 25%) of correction was achieved in the majority of patients. Some of this apparent rigidity derived from the inability to apply sufficient instrumental corrective force because of the friable osteoporotic bone. After surgery, there was a marked decrease in the frequency of pneumonia and an improvement in the degree of ataxia, for reasons not understood, which led to an obvious improvement in the quality of life.

Pattern of plasma levels of catecholamines in familial dysautonomia

This report extends previous investigations of endogenous catecholamine levels in patients with orthostatic hypotension due to familial dysautonomia (FD), to define better the neurochemical phenotype and elucidate possible pathophysiological mechanisms. Ten FD patients (age 26.1 +/- 2.6 (SEM) years) and eight control subjects (age 29.5 +/- 3.7 years) were studied. Heart rate, blood pressure and venous blood samples were obtained while supine and after 5 min in the upright position. Plasma levels of dihydroxyphenylalanine (DOPA), noradrenaline (NA), adrenaline (A), dopamine (DA), dihydroxyphenylglycol (DHPG) and dihydroxyphenylacetic acid (DOPAC) were measured. When supine, the FD group had greater NA and DOPA levels, and lower DHPG levels. Plasma NA did not increase with erect posture in FD patients. Individual FD mean blood pressures were correlated positively with plasma NA levels when supine and with plasma DA and DOPAC when upright. In FD, DOPA:DHPG ratios were above the range found in normal subjects or that reported in patients with acquired forms of dysautonomia regardless of posture, whereas DOPAC:DHPG ratios remained normal. Thus FD patients have a characteristic neurochemical pattern which probably reflects either decreased vesicular storage of catecholamines or limited oxidative deamination despite normal or increased tyrosine hydroxylation.

Preliminary observations on the use of midodrine in treating orthostatic hypotension in familial dysautonomia

Midodrine, a peripheral alpha-adrenergic agonist, was evaluated in 7 female and 2 male patients with familial dysautonomia (FD), a disorder characterized by decreased sympathetic innervation. Prior to and after three months of midodrine treatment, each patient's response to postural change was assessed by arteriosonde readings of blood pressure and heart rate, corrected QT-interval measurements, Doppler evaluation of renal blood flow and circulating atrial natriuretic peptide (ANP) levels. The initial midodrine dose (2.5 mg three times daily) was raised until subjective symptoms improved. Doses were reduced if patients felt jittery or developed erect hypertension (systolic > 180 mmHg or diastolic > 110 mmHg). Midodrine, at an average dose of 0.25 mg/kg per day, improved subjective symptoms in all patients. With treatment, magnitude of blood pressure responses was variable. Although mean erect blood pressure did not increase significantly for the aggregate, it did increase in six of nine patients. In addition, the QTc interval normalized and erect renal perfusion improved. Changes in supine mean blood pressure and supine circulating ANP correlated directly. We judge midodrine to be useful in management of orthostatic hypotension in patients with familial dysautonomia.

Atrial natriuretic peptide response to postural change and medication in familial dysautonomia

Circulating atrial natriuretic peptide (ANP) was assayed before and after postural change and exercise in 54 patients with familial dysautonomia (FD) and 20 controls. ANP levels were compared with blood pressure, heart rate, plasma catecholamines and parameters of renal function. Compared with controls supine FD subjects had elevated blood pressures, heart rates and ANP levels (39 +/- 4 pg/ml vs. 23 +/- 3 pg/ml, p < 0.01). With the erect posture and exercise in FD subjects, blood pressure fell below control values, with ANP lowered. In FD subjects, blood pressure was correlated with ANP levels when supine and when erect and with heart rate post exercise. In controls, ANP levels did not correlate with other parameters. In FD patients on metoclopramide, supine and erect blood pressure and ANP levels were higher. FD subjects treated with fludrocortisone, had elevated supine and erect noradrenaline (p < 0.05 and p = 0.06); and those on diazepam had lower erect and post exercise noradrenaline (p < 0.05), but ANP levels were similar. In conclusion, sympathetic denervation may increase FD patients' responsiveness to other regulators of cardiovascular integrity, such as ANP. In addition, circulating ANP and catecholamines in FD subjects appear to be influenced by commonly used medications, such as metoclopramide.

The effects of postural change and exercise on renal haemodynamics in familial dysautonomia

Cardiovascular instability is a prominent manifestation of familial dysautonomia [FD] while renal insufficiency occurs in a large number of adult FD patients. To determine if there was a causative relationship, renal artery blood flow velocity using Doppler technology, was recorded and the ratio of the peak systolic velocity (point A) to the end diastolic velocity (point B) was calculated. The A/B ratio was assessed in response to change of position and exercise, and was correlated with renal function, heart rate and systemic blood pressure. Studies were performed in 54 FD patients with a mean age of 24 years +/- 9.8 years, and 20 controls, with a mean age of 24.7 +/- 7.6 years. In the supine position, the mean A/B ratios were not significantly different, but FD subjects had a significantly higher mean blood pressure and heart rate than controls. When erect and post exercise, the mean A/B ratios in FD subjects were significantly higher than controls, p = 0.0004 and p = 0.0001, respectively. In contrast to controls, when FD subjects were standing erect and post exercise, mean blood pressure decreased significantly without a significant change in heart rate. When FD subjects were divided into two groups based on their creatinine clearance value, the group with the lower creatinine clearances had a significantly greater fall in diastolic pressure when they moved from the supine to the erect position. Our results indicate that noninvasive Doppler techniques are helpful in detecting changes in renal blood flow in subjects with familial dysautonomia.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities of the corrected QT interval in familial dysautonomia: an indicator of autonomic dysfunction

We report abnormalities in corrected QT intervals with changes in position and after exercise in patients with familial dysautonomia and confirm the previously reported finding of abnormal heart rate and blood pressure responses. Prolonged corrected QT intervals (> 440 msec) with lack of appropriate shortening with exercise is a noninvasive means of demonstrating an aberration in autonomic regulation of cardiac conduction.

Dental and oral findings in patients with familial dysautonomia

Familial dysautonomia is an inherited autosomal recessive disease found almost exclusively in Ashkenazi Jews. It is characterized by selective damage to the sensory, motor, and autonomic peripheral nervous system. The main clinical features include decreased pain sensation, impaired temperature and blood pressure regulation, lack of tearing, absent tendon reflexes, and fungiform papillae on the tongue. The purpose of this study was to explore in depth and to verify the oral and dental status in familial dysautonomia. Twenty-two patients and 44 match-paired healthy persons of Ashkenazi descent were examined. Patients and parents had only little concern for their oral condition. Caries prevalence was lower than normal and plaque accumulation increased in all patients. Dental trauma was found in 59% of the patients, and 32% showed orodental self-mutilation. Dental age was within normal range, and dental arch measurements implied proportionally small jaws and little crowding. The low caries rate may be related to the known "hypersalivation" in familial dysautonomia and/or a possible change in the salivary composition and content, caused by chronic autonomic denervation.

Brainstem auditory evoked potentials in familial dysautonomia

The brainstem function of eight children with familial dysautonomia was investigated by brainstem auditory evoked potentials and compared with that of age-matched healthy control children. All median latencies of waves III and V in the study group were significantly higher than those of the control children. Brain transmission times of waves I-III and I-V were significantly prolonged in the study group compared with the control group. These results provide additional objective support for the assumption that the brainstem function of children with familial dysautonomia is affected by this disease.

Calcineurin and synaptophysin in the human spinal cord of normal individuals and patients with familial dysautonomia

This report concerns the immunohistochemical demonstration of two neuronal Ca2(+)-binding proteins, calcineurin and synaptophysin, in the spinal cord of normal controls and from patients with familial dysautonomia. In controls, calcineurin immunoreactivity was highly concentrated in small nerve cells and fibers of the substantia gelatinosa. Synaptophysin immunoreactivity was normally distributed throughout the spinal cord gray matter, being highly concentrated in the substantia gelatinosa, the dorsal nucleus of Clarke and the anterior horn. In patients with familial dysautonomia, no apparent changes in calcineurin immunoreactivity were found in the substantia gelatinosa. By contrast, there was a significant depletion of synaptophysin-positive axon terminals in the substantia gelatinosa and in the dorsal nucleus of Clarke of patients with familial dysautonomia.

Optic nerve dysfunction in familial dysautonomia

We examined 12 patients with familial dysautonomia who had clear corneas to determine if there was any optic nerve involvement. The patients ranged in age from 6 to 34 years. Visual acuity ranged from 20/20 to 20/100. Nineteen eyes of 12 patients (79%) had abnormal (mean +/- 3 S.D.) pattern reversal visual-evoked potentials as compared to 50 control eyes (P100 = 98.8 msec; S.D., +/- 4.5 msec). P100 latency appeared to worsen with age. Exodeviation was present in seven patients (58%) and correlated with visual acuity and P100 latency. Ophthalmoscopic examination showed some degree of optic nerve pallor in all eyes.