Sensory, motor, and autonomic dysfunction: the ner- vous system in familial dysautonomia

Sensorimotor control in the congenital absence of functional muscle spindles

Hereditary sensory and autonomic neuropathy type III (HSAN III), also known as familial dysautonomia or Riley-Day syndrome, results from an autosomal recessive genetic mutation that causes a selective loss of specific sensory neurones, leading to greatly elevated pain and temperature thresholds, poor proprioception, marked ataxia and disturbances in blood pressure control. Stretch reflexes are absent throughout the body, which can be explained by the absence of functional muscle spindle afferents - assessed by intraneural microelectrodes inserted into peripheral nerves in the upper and lower limbs. This also explains the greatly compromised proprioception at the knee joint, as assessed by passive joint-angle matching. Moreover, there is a tight correlation between loss of proprioceptive acuity at the knee and the severity of gait impairment. Surprisingly, proprioception is normal at the elbow, suggesting that participants are relying more on sensory cues from the overlying skin; microelectrode recordings have shown that myelinated tactile afferents in the upper and lower limbs appear to be normal. Nevertheless, the lack of muscle spindles does affect sensorimotor control in the upper limb: in addition to poor performance in the finger-to-nose test, manual performance in the Purdue pegboard task is much worse than in age-matched healthy controls. Unlike those rare individuals with large-fibre sensory neuropathy, in which both muscle spindle and cutaneous afferents are absent, those with HSAN III present as a means of assessing sensorimotor control following the selective loss of muscle spindle afferents.

Elbow proprioception is normal in patients with a congenital absence of functional muscle spindles

KEY POINTS

Individuals with hereditary sensory and autonomic neuropathy type III (HSAN III), also known as Riley-Day syndrome or familial dysautonomia, do not have functional muscle spindle afferents but do have essentially normal cutaneous mechanoreceptors. Lack of muscle spindle feedback from the legs may account for the poor proprioception at the knee and the ataxic gait typical of HSAN III. Given that functional muscle spindle afferents are also absent in the upper limb, we assessed whether proprioception at the elbow was likewise compromised. Passive joint angle matching showed that proprioception was normal at the elbow, suggesting that individuals with HSAN III rely more on cutaneous afferents around the elbow.

ABSTRACT

Hereditary sensory and autonomic neuropathy type III (HSAN III) is a rare neurological condition that features a marked ataxic gait that progressively worsens over time. We have shown that functional muscle spindle afferents are absent in the upper and lower limbs in HSAN III, and we have argued that this may account for the ataxia. We recently used passive joint angle matching to demonstrate that proprioception of the knee joint is very poor in HSAN III but can be improved towards normal by application of elastic kinesiology tape across the knee joints, which we attribute to the presence of intact cutaneous mechanoreceptors. Here we assessed whether proprioception was equally compromised at the elbow joint, and whether it could be improved through taping. Proprioception at the elbow joint was assessed using passive joint angle matching in 12 HSAN III patients and 12 age-matched controls. There was no difference in absolute error, gradient or correlation coefficient of the relationship between joint angles of the reference and indicator arms. Unlike at the knee, taping did not improve elbow proprioception in either group. Clearly, the lack of muscle spindles compromised proprioception at the knee but not at the elbow, and we suggest that the HSAN III patients rely more on proprioceptive signals from the skin around the elbow.

Impaired sensorimotor control of the hand in congenital absence of functional muscle spindles

Patients with hereditary sensory and autonomic neuropathy type III (HSAN III) exhibit marked ataxia, including gait disturbances. We recently showed that functional muscle spindle afferents in the leg, recorded via intraneural microelectrodes inserted into the peroneal nerve, are absent in HSAN III, although large-diameter cutaneous afferents are intact. Moreover, there is a tight correlation between loss of proprioceptive acuity at the knee and the severity of gait impairment. We tested the hypothesis that manual motor performance is also compromised in HSAN III, attributed to the predicted absence of muscle spindles in the intrinsic muscles of the hand. Manual performance in the Purdue pegboard task was assessed in 12 individuals with HSAN III and 11 age-matched healthy controls. The mean (±SD) pegboard score (number of pins inserted in 30 s) was 8.1 ± 1.9 and 8.6 ± 1.8 for the left and right hand, respectively, significantly lower than the scores for the controls (15.0 ± 1.3 and 16.0 ± 1.1; P < 0.0001). Performance was not improved after kinesiology tape was applied over the joints of the hand. In 5 patients we inserted a tungsten microelectrode into the ulnar nerve at the wrist. No spontaneous or stretch-evoked muscle afferent activity could be identified in any of the 11 fascicles supplying intrinsic muscles of the hand, whereas touch-evoked activity from low-threshold cutaneous mechanoreceptor afferents could readily be recorded from 4 cutaneous fascicles. We conclude that functional muscle spindles are absent in the short muscles of the hand and most likely absent in the long finger flexors and extensors, and that this largely accounts for the poor manual motor performance in HSAN III. NEW & NOTEWORTHY We describe the impaired manual motor performance in patients with hereditary sensory and autonomic neuropathy type III (Riley-Day syndrome), who exhibit congenital insensitivity to pain, poor proprioception, and marked gait ataxia. We show that functional muscle spindles are absent in the intrinsic muscles of the hand, which we argue contributes to their poor performance in a task involving the precision grip.

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.

Primary somatosensory contribution to action observation brain activity-combining fMRI and cTBS

Traditionally the mirror neuron system (MNS) only includes premotor and posterior parietal cortices. However, somatosensory cortices, BA1/2 in particular, are also activated during action execution and observation. Here, we examine whether BA1/2 and the parietofrontal MNS integrate information by using functional magnetic resonance imaging (fMRI)-guided continuous theta-burst stimulation (cTBS) to perturb BA1/2. Measuring brain activity using fMRI while participants are under the influence of cTBS shows local cTBS effects in BA1/2 varied, with some participants showing decreases and others increases in the BOLD response to viewing actions vs control stimuli. We show how measuring cTBS effects using fMRI can harness this variance using a whole-brain regression. This analysis identifies brain regions exchanging action-specific information with BA1/2 by mapping voxels away from the coil with cTBS-induced, action-observation-specific BOLD contrast changes that mirror those under the coil. This reveals BA1/2 exchanges action-specific information with premotor, posterior parietal and temporal nodes of the MNS during action observation. Although anatomical connections between BA1/2 and these regions are well known, this is the first demonstration that these connections carry action-specific signals during observation and hence, that BA1/2 plays a causal role in the human MNS.

Increasing cutaneous afferent feedback improves proprioceptive accuracy at the knee in patients with sensory ataxia

Hereditary sensory and autonomic neuropathy type III (HSAN III) features disturbed proprioception and a marked ataxic gait. We recently showed that joint angle matching error at the knee is positively correlated with the degree of ataxia. Using intraneural microelectrodes, we also documented that these patients lack functional muscle spindle afferents but have preserved large-diameter cutaneous afferents, suggesting that patients with better proprioception may be relying more on proprioceptive cues provided by tactile afferents. We tested the hypothesis that enhancing cutaneous sensory feedback by stretching the skin at the knee joint using unidirectional elasticity tape could improve proprioceptive accuracy in patients with a congenital absence of functional muscle spindles. Passive joint angle matching at the knee was used to assess proprioceptive accuracy in 25 patients with HSAN III and 9 age-matched control subjects, with and without taping. Angles of the reference and indicator knees were recorded with digital inclinometers and the absolute error, gradient, and correlation coefficient between the two sides calculated. Patients with HSAN III performed poorly on the joint angle matching test [mean matching error 8.0 ± 0.8° (±SE); controls 3.0 ± 0.3°]. Following application of tape bilaterally to the knee in an X-shaped pattern, proprioceptive performance improved significantly in the patients (mean error 5.4 ± 0.7°) but not in the controls (3.0 ± 0.2°). Across patients, but not controls, significant increases in gradient and correlation coefficient were also apparent following taping. We conclude that taping improves proprioception at the knee in HSAN III, presumably via enhanced sensory feedback from the skin.

Balance training using an iPhone application in people with familial dysautonomia: three case reports

BACKGROUND AND PURPOSE

Familial dysautonomia (FD) is a rare genetic autosomal recessive disease that impairs vital functions and causes neural and motor deficiency. These motor deficits often are characterized by static and dynamic instability and an ataxic gait. As a result, people with FD are at risk for significant physical impairment and falls and pose unique challenges for delivering rehabilitation exercise. Consequently, there is a need for challenging ways to safely and feasibly deliver active exercise rehabilitation to these individuals.

CASE DESCRIPTION

This case report describes 3 people with FD (ages 11, 12, and 22 years) with gait and stability problems who attended rehabilitation exercises augmented by the use of an iPhone application specifically developed for the program.

OUTCOMES

The Berg Balance Scale and the Four Square Step Test were conducted prior to training, after training, and after 2 months of follow-up without training. Two patients showed improvements on both measures at the posttest, which were maintained throughout follow-up testing.

DISCUSSION

Although greater experience is needed to more fully evaluate the efficiency of the iPhone application used in this program for people with FD, the results of these initial cases are encouraging. Systematically and prospectively tracking motor abilities and other functional outcomes during rehabilitation of individuals with FD who use the suggested application in balance training is recommended in order to provide greater evidence in this area.

Brainstem reflexes in patients with familial dysautonomia

OBJECTIVE

Several distinctive clinical features of patients with familial dysautonomia (FD) including dysarthria and dysphagia suggest a developmental defect in brainstem reflexes. Our aim was to characterize the neurophysiological profile of brainstem reflexes in these patients.

METHODS

We studied the function of sensory and motor trigeminal tracts in 28 patients with FD. All were homozygous for the common mutation in the IKAP gene. Each underwent a battery of electrophysiological tests including; blink reflexes, jaw jerk reflex, masseter silent periods and direct stimulation of the facial nerve. Responses were compared with 25 age-matched healthy controls.

RESULTS

All patients had significantly prolonged latencies and decreased amplitudes of all examined brainstem reflexes. Similar abnormalities were seen in the early and late components. In contrast, direct stimulation of the facial nerve revealed relative preservation of motor responses.

CONCLUSIONS

The brainstem reflex abnormalities in FD are best explained by impairment of the afferent and central pathways. A reduction in the number and/or excitability of trigeminal sensory axons is likely the main problem.

SIGNIFICANCE

These findings add further evidence to the concept that congenital mutations of the elongator-1 protein (or IKAP) affect the development of afferent neurons including those carrying information for the brainstem reflex pathways.

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.

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.

Sensory neuron diseases

Sensory neuron diseases (SND) are a distinct subgroup of peripheral-nervous-system diseases, first acknowledged in 1948. Acquired SND have a subacute or chronic course and are associated with systemic immune-mediated diseases, vitamin intoxication or deficiency, neurotoxic drugs, and life-threatening diseases such as cancer. SND are commonly idiopathic but can be genetic diseases; the latter tend to involve subtypes of sensory neurons and are associated with certain clinical pictures. The loss of sensory neurons in dorsal root ganglia causes the degeneration of short and long peripheral axons and central sensory projections in the posterior columns. This pathological process leads to a pattern of sensory nerve degeneration that is not length dependent and explains distinct clinical and neurophysiological abnormalities. Here we propose a comprehensive approach to the diagnosis of acquired and hereditary SND and discuss clinical, genetic, neurophysiological, neuroradiological, and neuropathological assessments.

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.

Calcitonin gene related peptide in familial dysautonomia

Familial dysautonomia (FD) patients have diminished sensory C-fibers. Calcitonin gene related peptide (CGRP) is a widely distributed neuropeptide and prominent neurotransmitter in C-fibers. We show that plasma CGRP levels measured by radioimmunoassay is significantly lower in 51 FD patients compared to controls (P<0.001). In 11/51 FD patients with FD crisis and in 19/51 FD patients with pneumonia, the mean CGRP levels rose significantly as compared to their baseline (P<0.003, P<0.001, respectively). The deficiency of CGRP in FD patients is consistent with their depletion of C-fibers, and may explain some of their symptoms, either directly or via modulation of sympathetic activity.

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.

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.

Abnormal enamel and pulp dimensions in familial dysautonomia

In familial dysautonomia (FD), a hereditary autonomic and sensory neuropathy, somatic growth is impaired. This study was conducted to explore the possibility that tooth dimensions are altered as a consequence of neural crest dysfunction known to be present in FD. Enamel, dentin, pulp, and tooth size measurements of mandibular primary and permanent molars from FD patients were compared with those of healthy controls. It was found that although tooth size in the FD patients was smaller than normal, the enamel was thicker on the occlusal table, while the pulp chamber was smaller and disproportional to tooth size. Our results suggest distorted tooth dimensions rather than a generalized growth arrest as observed in other hereditary syndromes, such as Down's or Crouzon.

Autonomic neuropathy, II: Specific peripheral neuropathies

Autonomic dysfunction is a common complication of peripheral neuropathies. It is often of little clinical importance, but some conditions may cause profound disturbance of autonomic function. These conditions include acute dysautonomia, diabetes, primary and familial amyloidosis, Guillain-Barré syndrome, porphyria, and some inherited neuropathies. A wide range of neuropathies are associated with lesser degrees of autonomic dysfunction. These include hereditary neuropathies, and neuropathies associated with metabolic disturbances, alcohol abuse, malignancy, medications, infections, and connective tissue disorders.

Oro-dental self-mutilation in familial dysautonomia

Orodental self-mutilation (ODSM) has not gained sufficient recognition in familial dysautonomia (FD). Among 38 patients with FD, ODSM was found in 14 (36.8%). ODSM may be due to peripheral neuropathy with insensibility to pain, which is characteristic of FD. Elimination of the sharp edges of teeth was found to be helpful.

Familial dysautonomia (Riley-Day syndrome)

Familial dysautonomia, also known as Riley-Day syndrome, is a disorder of autonomic nervous system with an autosomal recessive mode of inheritance. Reduction and/or loss of unmyelinated and small myelinated fibers is found, as reduction of dopamine beta-hydroxylase in blood. The diagnosis is based on clinical features: diminished lacrimation, insensitivity to pain, poor temperature control, abolished deep tendon reflexes, postural hypotension, vomiting attacks, poor motor coordination, and mental retardation. The treatment is symptomatic and many children die during the first years of life, usually as a result of repeated aspiration pneumonia. We report the case of a 1 year-old child with familial dysautonomia.

Hereditary sensory neuropathies

Hereditary sensory neuropathies have not shared in the major advances that have taken place in the molecular genetics of the hereditary demyelinating motor and sensory neuropathies. Thus far, classification depends upon their mode of inheritance and clinical features. The delineation of the various clinical syndromes is still not complete. This is a necessary preliminary to establishing the genetic basis of these neuropathies. The hereditary sensory neuropathies can be accordingly grouped into those with predominantly sensory and some associated autonomic features and those in which a sensory neuropathy is part of a spinocerebellar degeneration or other multisystem degeneration.

Tonic pupil, areflexia, and segmental anhidrosis: two additional cases of Ross syndrome and review of the literature

Two patients are described with the triad of tonic pupil, hyporeflexia and segmental anhidrosis (Ross syndrome). Only 18 cases of this syndrome have been reported in the literature so far. While tonic pupil and reduced sweating can be attributed to the affection of postganglionic cholinergic parasympathetic and sympathetic fibres projecting to the iris and sweat glands, respectively, the pathogenesis of diminished or lost tendon jerks remains obscure. To identify the characteristic clinical features, the previous cases of Ross syndrome are reviewed. Recent evidence of subclinical disturbances of sweating in most patients with Adie's syndrome, i.e. tonic pupil and areflexia, casts doubt on the nosological concept of Ross syndrome as a distinct clinical entity.

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.

Disorders of the autonomic nervous system: Part 1. Pathophysiology and clinical features

Autonomic dysfunction may result from diseases that affect primarily either the central nervous system or the peripheral autonomic nervous system. The most common pathogenesis of disturbed autonomic function in central nervous system diseases is degeneration of the intermediolateral cell columns (progressive autonomic failure) or disease or damage to descending pathways that synapse on the intermediolateral column cells (spinal cord lesions, cerebrovascular disease, brainstem tumors, multiple sclerosis). The peripheral autonomic nervous system may be damaged in isolation in the acute and subacute autonomic neuropathies or in association with a generalized peripheral neuropathy. The peripheral neuropathies most likely to cause severe autonomic disturbance are those in which small myelinated and unmyelinated fibers are damaged in the baroreflex afferents, the vagal efferents to the heart, and the sympathetic efferent pathways to the mesenteric vascular bed. Acute demyelination of the sympathetic and parasympathetic nerves in the Guillain-Barré syndrome may also cause acute autonomic dysfunction. Although autonomic disturbances may occur in other types of peripheral neuropathy, they are rarely clinically important.

Optic atrophy in familial dysautonomia

We examined three patients with classic findings of familial dysautonomia (Riley-Day syndrome) whose visual impairment was associated with optic atrophy. The presence of an optic atrophy in familial dysautonomia is indicative of central nervous system involvement, at least in these cases. Each of these patients was first noted to have visual impairment after the first decade. The late onset of optic atrophy may partly explain its apparent rarity. Since the life span of patients with familial dysautonomia is increasing, optic atrophy may be more commonly recognized in the future.

Sleep apnea and hypoventilation syndrome associated with acquired nonprogressive dysautonomia: clinical and pathological studies in a child

A 6-year-old girl had subacute onset of hypoventilation and apnea during sleep. Diffuse dysautonomic changes were identified, including dilated, nonreactive pupils, decreased tearing and sweating, and abnormal temperature and cardiovascular control. All-night polysomnographic studies revealed frequent obstructive and central sleep apnea episodes. Her serum contained cytotoxic antineuroblastoma immunoglobulins. She died two years later during sleep. The general pathological examination revealed a ganglioneuroma originating in the sympathetic ganglia. Abnormalities in the brain were confined to the brainstem and consisted of complete loss of neurons with severe fibrillary gliosis in the region of the Edinger-Westphal nuclei as well as loss of neurons with gliosis in the locus ceruleus and in the reticular formation bilaterally.

A new type of non-progressive sensory neuropathy in children with atypical dysautonomia

Three cases of non-progressive, sensory neuropathy with dysautonomia are presented. Light and electron microscopy on whole sural nerve biopsies revealed an almost total lack of myelinated nerve fibres. The total fibre count was also reduced as was the total number of Schwann cell nuclei. No degenerative phenomena were seen within the nerve fibres. The aberrations are probably caused by a maldevelopment of the neural crest implying a stunted proliferation and growth of sensory and autonomous neurones as well as a reduced proliferation of Schwann cells. Since the morphology and clinical features differ from that in other cases of sensory neuropathy with dysautonomia the three present cases are considered to represent a new type of the disease.

Quantitative studies of sympathetic ganglia and spinal cord intermedio-lateral gray columns in familial dysautonomia

In adult patients with familial dysautonomia the mean volume of superior cervical sympathetic ganglia is reduced to 34% of the normal of 222 mm3. Packing density of neurons is reduced to 37% of normal. The mean total number of ganglionic neurons is 120,000 as compared to 1,060,000 in controls. The mean totals of preganglionic neurons in the first three thoracic cord segments are 13,600 in patients and 25,150 in controls. Deficits in sympathetic neurons account for many of the clinical, pharmacological and biochemical manifestations of familial dysautonomia.

Quantitative studies of dorsal root ganglia and neuropathologic observations on spinal cords in familial dysautonomia

Intrauterine development and postnatal maintenance of dorsal root ganglion neurons are abnormal in familial dysautonomia, an autosomal recessive disorder associated with autonomic, motor and sensory deficits. Normally, dorsal root ganglion weight increases with age. This does not occur in the cervical plexus ganglia of dysautonomic patients. Neurons in dorsal root ganglia are found to be markedly diminished in the youngest patients and slow degeneration causes further depletion with age. Quantitative studies on C8 dorsal root ganglia show the normal neuron content to be between 42,500 and 53,600. In 3 patients with familial dysautonomia the range was 4,090-8,590 with the smallest number being in the oldest patient. Lateral root entry zones and Lissauer's tracts are severely depleted of axons. In older patients loss of dorsal column myelinated axons becomes evident and is first seen in lumbar fasciculus gracilis, cervical fasciculus cuneatus and interfascicular fasciculus. Temperature sensation is markedly impaired from infancy in familial dysautonomia. Loss of pain sensation is prominent and worsens with age. Vibration sense diminishes in adolescence and coordination of limb movements becomes poor in older patients. Neuron depletion in dorsal root ganglia and the progressive pattern of cord changes correlate well with these clinical observations.

Familial dysautonomia (Riley-Day syndrome). Temporal bone findings and otolaryngological manifestations

Familial dysautonomia, or Riley-Day syndrome, is inherited in an autosomal recessive fashion and occurs almost exclusively in Jewish families. This disorder is characterized by a smooth tongue devoid of fungiform papillae and of taste buds, and is clinically associated with poor taste discrimination. An unsteady gait and dizziness on change in position are also common presenting symptoms. This study reports the histopathological findings of eight temporal bones from four patients with documented familial dysautonomia. For the control series, 13 normal temporal bones were also studied. The most striking finding in the dysautonomic patients was an extreme paucity of geniculate ganglion cells (P less than 0.001). A statistically significant reduction in the number of neurons was also found both in the superior and in the inferior divisions of the vestibular nerve (P less than 0.001). The paucity of the geniculate ganglion cells correlates well with the impairment of the taste in dysautonomic individuals, since the afferent fibers leaving taste buds of the anterior two-thirds of the tongue run via the chorda tympani and have their cell bodies in the geniculate ganglion. Furthermore, the reduction in the number of Scarpa's ganglion cells observed in the dysautonomic patients studied here could account for a poor response to caloric test, positional vertigo and an unsteady gait in this condition.

Familial dysautonomia in a non-Jewish child

Few documented cases of Riley-Day syndrome fulfilling current diagnostic criteria have been recognized in non-Jews. In our case the diagnosis was established in a Norwegian child despite the absence of Jewish origin. It represents a report of this syndrome with bilateral pathological changes in the hypothalamus in addition to extensive abnormal findings in the spinal cord and the autonomic ganglia. These findings may have significance with regard to the pathogenesis of the disease.

Increased nerve-growth-factor beta-chain cross-reacting material in familial dysautonomia

To determine whether dysautonomia arises from alteration in nerve-growth factor (NGF), we measured serum levels of NGF subunits in normal and dysautonomic subjects using a biologic assay based on neurite outgrowth from chick ganglions, a binding assay based on displacement of radiolabeled betaNGF from rabbit-ganglion microsomes, and radioimmunoassays of chi, gamma and betaNGF subunits via antiserum to mouse NGF polypeptides. A threefold increase (P less than 0.001) in serum antigen levels of the biologically active subunit (betaNGF) was found for dysautonomic as compared with normal subjects. By all other assays, the groups were alike. The marked discrepancy in betaNGF levels between antigenic and functional (biologic and binding) measurements suggests a qualitative abnormaltiy of betaNGF in dysautonomia. Alternatively, elevation of betaNGF antigen can be regarded as secondary to disease. This alternative seems less likely since we must then suppose that the normalcy of functional assays in spurious.

Vestibular dysfunction in familial dysautonomia. The Riley-Day syndrome

We report the bilateral absence of response to tests of vestibular function in 5 patients with familial dysautonomia.