Neurofilament light chain in spinal fluid and plasma in multiple system atrophy: a prospective, longitudinal biomarker study

PURPOSE

There is a critical need for reliable diagnostic biomarkers as well as surrogate markers of disease progression in multiple system atrophy (MSA). Neurofilament light chain (NfL) has been reported to potentially meet those needs. We therefore sought to explore the value of NfL in plasma (NfL-p) in contrast to cerebrospinal fluid (NfL-c) as a diagnostic marker of MSA, and to assess NfL-p and NfL-c as markers of clinical disease progression.

METHODS

Well-characterized patients with early MSA (n = 32), Parkinson's disease (PD; n = 21), and matched controls (CON; n = 15) were enrolled in a prospective, longitudinal study of synucleinopathies with serial annual evaluations. NfL was measured using a high-sensitivity immunoassay, and findings were assessed by disease category and relationship with clinical measures of disease progression.

RESULTS

Measurements of NfL-c were highly reproducible across immunoassay platforms (Pearson, r = 0.99), while correlation between NfL-c and -p was only moderate (r = 0.66). NfL was significantly higher in MSA compared with CON and PD; the separation was essentially perfect for NfL-c, but there was overlap, particularly with PD, for NfL-p. While clinical measures of disease severity progressively increased over time, NfL-c and -p remained at stable elevated levels within subjects across serial measurements. Neither change in NfL nor baseline NfL were significantly associated with changes in clinical markers of disease severity.

CONCLUSIONS

These findings confirm NfL-c as a faithful diagnostic marker of MSA, while NfL-p showed less robust diagnostic value. The significant NfL elevation in MSA was found to be remarkably stable over time and was not predictive of clinical disease progression.

Neurofilament Light Chain in Spinal Fluid and Plasma in Multiple System Atrophy - A Prospective, Longitudinal Biomarker Study

Purpose There is a critical need for reliable diagnostic biomarkers as well as surrogate markers of disease progression in multiple system atrophy (MSA). Neurofilament light chain (NfL) has been reported to potentially meet those needs. We therefore sought to explore the value of NfL in plasma (NfL-p) in contrast to CSF (NfL-c) as diagnostic marker of MSA, and to assess NfL-p and NfL-c as markers of clinical disease progression. Methods Well-characterized patients with early MSA (n=32), Parkinson's disease (PD, n=21), and matched controls (CON, n=15) were enrolled in a prospective, longitudinal study of synucleinopathies with serial annual evaluations. NfL was measured using a high sensitivity immunoassay, and findings were assessed by disease category and relationship with clinical measures of disease progression. Results Measurements of NfL-c were highly reproducible across immunoassay platforms (Pearson,r=0.99), while correlation between NfL-c and -p was only moderate (r=0.66). NfL was significantly higher in MSA compared to CON and PD; the separation was essentially perfect for NfL-c, but there was overlap, particularly with PD, for NfL-p. While clinical measures of disease severity progressively increased over time, NfL-c and -p remained at stable elevated levels within subjects across serial measurements. Neither change in NfL nor baseline NfL were significantly associated with changes in clinical markers of disease severity. Conclusions These findings confirm NfL-c as faithful diagnostic marker of MSA, while NfL-p showed less robust diagnostic value. The significant NfL elevation in MSA was found to be remarkably stable over time and was not predictive of clinical disease progression.

Imaging biomarkers for early multiple system atrophy

OBJECTIVE

To systematically evaluate structural MRI and diffusion MRI features for cross-sectional discrimination and tracking of longitudinal disease progression in early multiple system atrophy (MSA).

METHODS

In a prospective, longitudinal study of synucleinopathies with imaging on 14 controls and 29 MSA patients recruited at an early disease stage (15 predominant cerebellar ataxia subtype or MSA-C and 14 predominant parkinsonism subtype or MSA-P), we computed regional morphometric and diffusion MRI features. We identified morphometric features by ranking them based on their ability to distinguish MSA-C from controls and MSA-P from controls and evaluated diffusion changes in these regions. For the top performing regions, we evaluated their utility for tracking longitudinal disease progression using imaging from 12-month follow-up and computed sample size estimates for a hypothetical clinical trial in MSA. We also computed these selected morphometric features in an independent validation dataset.

RESULTS

We found that morphometric changes in the cerebellar white matter, brainstem, and pons can separate early MSA-C patients from controls both cross-sectionally and longitudinally (p < 0.01). The putamen and striatum, though useful for separating early MSA-P patients from control subjects at baseline, were not useful for tracking MSA disease progression. Cerebellum white matter diffusion changes aided in capturing early disease related degeneration in MSA.

INTERPRETATION

Regardless of clinically predominant features at the time of MSA assessment, brainstem and cerebellar pathways progressively deteriorate with disease progression. Quantitative measurements of these regions are promising biomarkers for MSA diagnosis in early disease stage and potential surrogate markers for future MSA clinical trials.

Alpha-Synuclein Oligomers and Neurofilament Light Chain Predict Phenoconversion of Pure Autonomic Failure

OBJECTIVE

To explore the role of alpha-synuclein (αSyn) oligomers and neurofilament light chain (NfL) in cerebrospinal fluid (CSF) of patients with pure autonomic failure (PAF) as markers of future phenoconversion to multiple system atrophy (MSA).

METHODS

Well-characterized patients with PAF (n = 32) were enrolled between June 2016 and February 2019 at Mayo Clinic Rochester and followed prospectively with annual visits to determine future phenoconversion to MSA, Parkinson's disease (PD), or dementia with Lewy bodies (DLB). ELISA was utilized to measure NfL and protein misfolding cyclic amplification (PMCA) to detect αSyn oligomers in CSF collected at baseline.

RESULTS

Patients were followed for a median of 3.9 years. Five patients converted to MSA, 2 to PD, and 2 to DLB. NfL at baseline was elevated only in patients who later developed MSA, perfectly separating those from future PD and DLB converters as well as non-converters. ASyn-PMCA was positive in all but two cases (94%). The PMCA reaction was markedly different in five samples with maximum fluorescence and reaction kinetics previously described in MSA patients; all of these patients later developed MSA.

INTERPRETATION

αSyn-PMCA is almost invariably positive in the CSF of patients with PAF establishing this condition as α-synucleinopathy. Both NfL and the magnitude and reaction kinetics of αSyn PMCA faithfully predict which PAF patients will eventually phenoconvert to MSA. This finding has important implications not only for prognostication, but also for future trials of disease modifying therapies, allowing for differentiation of MSA from Lewy body synucleinopathies before motor symptoms develop. ANN NEUROL 2021;89:1212-1220.

Alpha-Synuclein Oligomers and Neurofilament Light Chain in Spinal Fluid Differentiate Multiple System Atrophy from Lewy Body Synucleinopathies

OBJECTIVE

To explore the role of alpha-synuclein (αSyn) oligomers and neurofilament light chain (NFL) in cerebrospinal fluid (CSF) as markers of early multiple system atrophy (MSA) and to contrast findings with Lewy body synucleinopathies.

METHODS

In a discovery cohort of well-characterized early MSA patients (n = 24) and matched healthy controls (CON, n = 14), we utilized enzyme-linked immunosorbent assay to measure NFL and protein misfolding cyclic amplification (PMCA) to detect αSyn oligomers in CSF. We confirmed findings in a separate prospectively enrolled cohort of patients with early MSA (n = 38), Parkinson disease (PD, n = 16), and dementia with Lewy bodies (DLB, n = 13), and CON subjects (n = 15).

RESULTS

In the discovery cohort, NFL was markedly elevated in MSA patients, with perfect separation from CON. αSyn-PMCA was nonreactive in all CON, whereas all MSA samples were positive. In the confirmatory cohort, NFL again perfectly separated MSA from CON, and was significantly lower in PD and DLB compared to MSA. PMCA was again nonreactive in all CON, and positive in all but 2 MSA cases. All PD and all but 2 DLB samples were also positive for αSyn aggregates but with markedly different reaction kinetics from MSA; aggregation occurred later, but maximum fluorescence was higher, allowing for perfect separation of reactive samples between MSA and Lewy body synucleinopathies.

INTERPRETATION

NFL and αSyn oligomers in CSF faithfully differentiate early MSA not only from CON but also from Lewy body synucleinopathies. The findings support the role of these markers as diagnostic biomarkers, and have important implications for understanding pathophysiologic mechanisms underlying the synucleinopathies. ANN NEUROL 2020;88:503-512.

Autonomic dysfunction and phenoconversion in idiopathic REM sleep behavior disorder

BACKGROUND

REM sleep behavior disorder (RBD) is a common finding among patients with synucleinopathies. We aimed to determine the degree of autonomic dysfunction in patients presenting with idiopathic RBD (iRBD), and the predictive value of autonomic dysfunction for phenoconversion to a defined neurodegenerative disease.

METHODS

We searched our electronic medical record for patients diagnosed with iRBD who also underwent standardized autonomic function testing within 6 months of iRBD diagnosis, and who had clinical follow-up of at least 3 years following iRBD diagnosis. The composite autonomic severity score (CASS) was derived and compared between phenoconverters and non-converters using chi-square and Wilcoxon rank-sum tests.

RESULTS

We identified 18 patients who fulfilled inclusion and exclusion criteria. Average age at autonomic testing was 67 ± 6.6 years. Twelve (67%) patients phenoconverted during the follow-up period; six developed Parkinson's disease (PD), and the other six, dementia with Lewy bodies (DLB). Fifteen (83%) patients had at least mild autonomic dysfunction. There were no significant differences between overall converters and non-converters in total CASS or CASS subscores. However, iRBD patients who developed DLB had significantly higher total and cardiovagal CASS scores compared with those who developed PD (p < 0.05), and a trend for higher adrenergic CASS scores compared to those who developed PD and those who did not phenoconvert.

DISCUSSION

Autonomic dysfunction was seen in 83% of iRBD patients, and more severe baseline cardiovagal autonomic dysfunction in iRBD was associated with phenoconversion to DLB but not PD. Prospective studies are needed to confirm the value of autonomic testing for predicting phenoconversion and disease phenotype in iRBD.

Intrathecal administration of autologous mesenchymal stem cells in multiple system atrophy

OBJECTIVE

This phase I/II study sought to explore intrathecal administration of mesenchymal stem cells (MSCs) as therapeutic approach to multiple system atrophy (MSA).

METHODS

Utilizing a dose-escalation design, we delivered between 10 and 200 million adipose-derived autologous MSCs intrathecally to patients with early MSA. Patients were closely followed with clinical, laboratory, and imaging surveillance. Primary endpoints were frequency and type of adverse events; key secondary endpoint was the rate of disease progression assessed by the Unified MSA Rating Scale (UMSARS).

RESULTS

Twenty-four patients received treatment. There were no attributable serious adverse events, and injections were generally well-tolerated. At the highest dose tier, 3 of 4 patients developed low back/posterior leg pain, associated with thickening/enhancement of lumbar nerve roots. Although there were no associated neurologic deficits, we decided that dose-limiting toxicity was reached. A total of 6 of 12 patients in the medium dose tier developed similar, but milder and transient discomfort. Rate of progression (UMSARS total) was markedly lower compared to a matched historical control group (0.40 ± 0.59 vs 1.44 ± 1.42 points/month, p = 0.004) with an apparent dose-dependent effect.

CONCLUSIONS

Intrathecal MSC administration in MSA is safe and well-tolerated but can be associated with a painful implantation response at high doses. Compelling dose-dependent efficacy signals are the basis for a planned placebo-controlled trial.

CLASSIFICATION OF EVIDENCE

This phase I/II study provides Class IV evidence that for patients with early MSA, intrathecal MSC administration is safe, may result in a painful implantation response at high doses, and is associated with dose-dependent efficacy signals.

Effects of patient-controlled abdominal compression on standing systolic blood pressure in adults with orthostatic hypotension

OBJECTIVE

To assess the effects of patient-controlled abdominal compression on postural changes in systolic blood pressure (SBP) associated with orthostatic hypotension (OH). Secondary variables included subject assessments of their preferences and the ease-of-use.

DESIGN

Randomized crossover trial.

SETTING

Clinical research laboratory.

PARTICIPANTS

Adults with neurogenic OH (N=13).

INTERVENTIONS

Four maneuvers were performed: moving from supine to standing without abdominal compression; moving from supine to standing with either a conventional or an adjustable abdominal binder in place; application of subject-determined maximal tolerable abdominal compression while standing; and while still erect, subsequent reduction of abdominal compression to a level the subject believed would be tolerable for a prolonged period.

MAIN OUTCOME MEASURES

The primary outcome variable included postural changes in SBP. Secondary outcome variables included subject assessments of their preferences and ease of use.

RESULTS

Baseline median SBP in the supine position was not affected by mild (10mmHg) abdominal compression prior to rising (without abdominal compression: 146mmHg; interquartile range, 124-164mmHg; with the conventional binder: 145mmHg; interquartile range, 129-167mmHg; with the adjustable binder: 153mmHg, interquartile range, 129-160mmHg; P=.85). Standing without a binder was associated with an -57mmHg (interquartile range, -40 to -76mmHg) SBP decrease. Levels of compression of 10mmHg applied prior to rising with the conventional and adjustable binders blunted these drops to -50mmHg (interquartile range, -33 to -70mmHg; P=.03) and -46mmHg (interquartile range, -34 to -75mmHg; P=.01), respectively. Increasing compression to subject-selected maximal tolerance while standing did not provide additional benefit and was associated with drops of -53mmHg (interquartile range, -26 to -71mmHg; P=.64) and -59mmHg (interquartile range, -49 to -76mmHg; P=.52) for the conventional and adjustable binders, respectively. Subsequent reduction of compression to more tolerable levels tended to worsen OH with both the conventional (-61mmHg; interquartile range, -33 to -80mmHg; P=.64) and adjustable (-67mmHg; interquartile range, -61 to -84mmHg; P=.79) binders. Subjects reported no differences in preferences between the binders in terms of preference or ease of use.

CONCLUSIONS

These results suggest that mild (10mmHg) abdominal compression prior to rising can ameliorate OH, but further compression once standing does not result in additional benefit.

Determination of vagal baroreflex sensitivity in normal subjects

INTRODUCTION

The Valsalva maneuver (VM) is used widely to quantify the sensitivity of the vagal baroreflex loop (vagal baroreflex sensitivity, BRS_v), but most studies have focused on the heart rate (HR) response to blood pressure (BP) decrement (BRS_v↓), even though the subsequent response to an increment in BP after the VM (BRS_v↑) is important and different.

METHODS

We evaluated recordings of HR and BP in 187 normal subjects during the VM and determined both BRS_v↑, as determined by relating HR to the BP increase after phase III and BRS_v↓.

RESULTS

BRS_v↑ was related inversely to age. In addition, BRS_v↓, age, and magnitude of phase IV were independent predictors of BRS_v↑ in a multivariate model, accounting for 47% of the variance of BRS_v↑.

CONCLUSIONS

The results indicate that both BRS_v↑ and BRS_v↓ become blunted with increasing age and that these indices relate to each other.

Decreased orthostatic adrenergic reactivity in non-dipping postural tachycardia syndrome

Whether non-dipping - the loss of the physiologic nocturnal drop in blood pressure - among patients with postural tachycardia syndrome (POTS) is secondary to autonomic neuropathy, a hyperadrenergic state, or other factors remains to be determined. In 51 patients with POTS (44 females), we retrospectively analyzed 24-hour ambulatory blood pressure recordings, laboratory indices of autonomic function, orthostatic norepinephrine response, 24-hour natriuresis and peak exercise oxygen consumption. Non-dipping (<10% day-night drop in systolic blood pressure) was found in 55% (n=28). Dippers and non-dippers did not differ in: 1) baseline characteristics including demographic and clinical profile, sleep duration, daytime blood pressure, 24-hour natriuresis, and peak exercise oxygen consumption; 2) severity of laboratory autonomic deficits (sudomotor, cardiovagal and adrenergic); 3) frequency of autonomic neuropathy (7/23 vs. 8/28, P=0.885); 4) supine resting heart rate (75.3±14.0bpm vs. 74.0±13.8bpm, P=0.532); or 5) supine plasma norepinephrine level (250.0±94.9pg/ml vs. 207.0±86.8pg/ml, P=0.08). However, dippers differed significantly from non-dippers in that they had significantly greater orthostatic heart rate increment (43±16bpm vs. 35±10bpm, P=0.007) and significantly greater orthostatic plasma norepinephrine increase (293±136.6pg/ml vs. 209±91.1pg/ml, P=0.028). Our data indicate that in patients with POTS, a non-dipping blood pressure profile is associated with a reduced orthostatic sympathetic reactivity not accounted for by autonomic neuropathy.

Autopsy confirmed multiple system atrophy cases: Mayo experience and role of autonomic function tests

BACKGROUND

Multiple system atrophy (MSA) is a sporadic progressive neurodegenerative disorder characterised by autonomic failure, manifested as orthostatic hypotension or urogenital dysfunction, with combinations of parkinsonism that is poorly responsive to levodopa, cerebellar ataxia and corticospinal dysfunction. Published autopsy confirmed cases have provided reasonable neurological characterisation but have lacked adequate autonomic function testing.

OBJECTIVES

To retrospectively evaluate if the autonomic characterisation of MSA is accurate in autopsy confirmed MSA and if consensus criteria are validated by autopsy confirmation.

METHODS

29 autopsy confirmed cases of MSA evaluated at the Mayo Clinic who had undergone formalised autonomic testing, including adrenergic, sudomotor and cardiovagal functions and Thermoregulatory Sweat Test (TST), from which the Composite Autonomic Severity Score (CASS) was derived, were included in the study.

PATIENT CHARACTERISTICS

17 men, 12 women; age of onset 57±8.1 years; disease duration to death 6.5±3.3 years; first symptom autonomic in 18, parkinsonism in seven and cerebellar in two. Clinical phenotype at first visit was MSA-P (predominant parkinsonism) in 18, MSA-C (predominant cerebellar involvement) in eight, pure autonomic failure in two and Parkinson's disease in one. Clinical diagnosis at last visit was MSA for 28 cases. Autonomic failure was severe: CASS was 7.2±2.3 (maximum 10). TST% was 65.6±33.9% and exceeded 30% in 82% of patients. The most common pattern was global anhidrosis. Norepinephrine was normal supine (203.6±112.7) but orthostatic increment of 33.5±23.2% was reduced. Four clinical features (rapid progression, early postural instability, poor levodopa responsiveness and symmetric involvement) were common.

CONCLUSION

The pattern of severe and progressive generalised autonomic failure with severe adrenergic and sudomotor failure combined with the clinical phenotype is highly predictive of MSA.

The role of autonomic testing in the differentiation of Parkinson's disease from multiple system atrophy

Differentiation of idiopathic Parkinson's disease (PD) from multiple system atrophy (MSA) can be difficult. Methods devised to help distinguish the two disorders include standardized autonomic testing and cardiac imaging with iodine-123 meta-iodobenzylguanidine myocardial scintigraphy. MSA patients had more severe adrenergic and overall autonomic dysfunction when compared to control and PD patients. Area of anhidrosis on thermoregulatory sweat test was greater in MSA (67.4±12.42, p<0.001) versus PD patients (area of anhidrosis, 1.7±2.96). Postganglionic cardiac sympathetic innervation (iodine-123 meta-iodobenzylguanidine) expressed as heart to mediastinal ratio was significantly lower in Parkinson's disease patients (1.4±0.40, p=0.025) compared to controls (2.0±0.29), but not in multiple system atrophy (2.0±0.76). These findings indicate that autonomic dysfunction is generalized and predominantly preganglionic in multiple system atrophy, and postganglionic in Parkinson's disease. In our hands the thermoregulatory sweat test provides the best distinction between MSA and PD. However further confirmatory studies using larger patient numbers are required. Currently a combination of clinical judgment and autonomic testing is recommended to help differentiate MSA and PD.

Prospective differentiation of multiple system atrophy from Parkinson disease, with and without autonomic failure

OBJECTIVE

To report preliminary results of a prospective ongoing study of multiple system atrophy (MSA) and Parkinson disease (PD), with a large subset of patients with PD with autonomic failure (25%), to evaluate autonomic indices that distinguish MSA from PD.

METHODS

We used consensus criteria, detailed autonomic studies (Composite Autonomic Symptom Scale, Composite Autonomic Scoring Scale, thermoregulatory sweat test, and plasma catecholamines), and functional scales (Unified MSA Rating Scale [UMSARS] I-IV and Hoehn-Yahr grading) on a prospective, repeated, and ongoing basis.

RESULTS

We report the results of a study on 52 patients with MSA (mean [SD], age, 61.1 [7.8] years; body mass index (calculated as weight in kilograms divided by height in meters squared), 27.2 [4.6]; Hoehn-Yahr grade, 3.2 [0.9]; UMSARS I score, 21.5 [7.4]; and UMSARS II score, 22.7 [9.0]) and 29 patients with PD, including PD with autonomic failure (mean [SD], age, 66.0 [8.1] years; body mass index, 26.6 [5.5]; Hoehn-Yahr grade, 2.2 [0.8]; UMSARS I score, 10.4 [6.1]; and UMSARS II score, 13.0 [5.9]). Autonomic indices were highly significantly more abnormal in MSA than PD (P < .001) for the Composite Autonomic Scoring Scale (5.9 [1.9] vs 3.3 [2.3], respectively), Composite Autonomic Symptom Scale (54.4 [21.8] vs 24.7 [20.5], respectively), and thermoregulatory sweat test (percentage anhidrosis, 57.4% [35.2%] vs 9.9% [17.7%], respectively). These differences were sustained and greater at 1-year follow-up, indicating a greater rate of progression of dysautonomia in MSA than PD.

CONCLUSIONS

The severity, distribution, and pattern of autonomic deficits at study entry will distinguish MSA from PD, and MSA from PD with autonomic failure. These differences continue and are increased at follow-up. Our ongoing conclusion is that autonomic function tests can separate MSA from PD. Autonomic indices support the notion that the primary lesion in PD is ganglionic and postganglionic, while MSA is preganglionic.

Patterns of neuropathy and autonomic failure in patients with amyloidosis

OBJECTIVE

To define the clinical patterns of peripheral neuropathy and autonomic testing abnormalities in patients with amyloidosis.

PATIENTS AND METHODS

A retrospective chart review was conducted of 65 patients who had biopsy-proven amyloidosis and autonomic function testing between January 1, 1985, and December 31, 1997, at Mayo Clinic's site in Rochester, MN. Patients were required to have neurologic evaluation, autonomic reflex screening, and tissue confirmation of amyloidosis.

RESULTS

We identified 5 clinical patterns of peripheral neuropathy: (1) generalized autonomic failure and polyneuropathy with pain (40 patients [62%]), (2) generalized autonomic failure and polyneuropathy without pain (11 [17%]), (3) isolated generalized autonomic failure (7 [11%]), (4) polyneuropathy without generalized autonomic failure (4 [6%]), and (5) generalized autonomic failure and small-fiber (ie, autonomic and somatic C-fiber) neuropathy (3 [5%]). Moderately severe generalized autonomic failure, involving adrenergic, cardiovagal, or sudomotor domains, was found in all patients, including those without clinically manifested autonomic failure. The diagnosis of amyloidosis was delayed in patients who did not have initial symptoms of pain or generalized autonomic failure (48 months to diagnosis in patients with polyneuropathy without autonomic failure vs 12 months to diagnosis in patients with autonomic failure and small-fiber neuropathy; P=.57).

CONCLUSION

Physicians should test for symptoms of generalized autonomic failure in patients who have peripheral neuropathy of unknown origin. Autonomic testing may give abnormal results in patients without overt symptoms of autonomic failure. Early recognition of autonomic failure may lead to earlier diagnosis of the underlying pathogenesis of amyloidosis, as well as earlier treatment for patients with this condition.

Pilot study of pyridostigmine in constipated patients with autonomic neuropathy

BACKGROUND

The effects of cholinesterase inhibitors, which increase colonic motility in health, on chronic constipation are unknown. Our aims were to evaluate the efficacy of cholinesterase inhibitors for dysautonomia and chronic constipation and to assess whether acute effects could predict the long term response.

METHODS

In this single-blind study, 10 patients with autonomic neuropathy and constipation were treated with placebo (2 weeks), followed by an escalating dose of pyridostigmine to the maximum tolerated dose (i.e., 180-540 mg daily) for 6 weeks. Symptoms and gastrointestinal transit were assessed at 2 and 8 weeks. The acute effects of neostigmine on colonic transit and motility were also assessed.

RESULTS

At baseline, 4, 6, and 3 patients had delayed gastric, small intestinal, and colonic transit respectively. Pyridostigmine was well tolerated in most patients, improved symptoms in 4 patients, and accelerated the geometric center for colonic transit at 24 h by > or =0.7 unit in 3 patients. The effects of i.v. neostigmine on colonic transit and compliance predicted (P < 0.05) the effects of pyridostigmine on colonic transit.

CONCLUSIONS

Pyridostigmine improves colonic transit and symptoms in some patients with autonomic neuropathy and constipation. The motor response to neostigmine predicted the response to oral pyridostigmine.

Effects of linearly polarized 0.6-1.6 microM irradiation on stellate ganglion function in normal subjects and people with complex regional pain (CRPS I)

BACKGROUND AND OBJECTIVES

Stellate ganglion blocks are an effective but invasive treatment of upper extremity pain. Linearly polarized red and near-infrared (IR) light is promoted as a safe alternative to this procedure, but its effects are poorly established. This study was designed to assess the physiological effects of this latter approach and to quantitate its benefits in people with upper extremity pain due to Complex Regional Pain Syndrome I (CRPS I, RSD).

STUDY DESIGN/MATERIALS AND METHODS

This was a two-part study. In the first phase, six adults (ages 18-60) with normal neurological examinations underwent transcutaneous irradiation of their right stellate ganglion with linearly polarized 0.6-1.6 microm light (0.92 W, 88.3 J). Phase two consisted of a double-blinded evaluation of active and placebo radiation in 12 subjects (ages 18-72) of which 6 had upper extremity CRPS I and 6 served as "normal" controls. Skin temperature, heart rate (HR), sudomotor function, and vasomotor tone were monitored before, during, and for 30 minutes following irradiation. Analgesic and sensory effects were assessed over the same period as well as 1 and 2 weeks later.

RESULTS

Three of six subjects with CRPS I and no control subjects experienced a sensation of warmth following active irradiation (P = 0.025). Two of the CRPS I subjects reported a >50% pain reduction. However, four noted minimal or no change and improvement did not reach statistical significance for the group as a whole. No statistically significant changes in autonomic function were noted. There were no adverse consequences.

CONCLUSIONS

Irradiation is well tolerated. There is a suggestion in this small study that treatment is beneficial and that its benefits are not dependent on changes in sympathetic tone. Further evaluation is warranted.