Assessment of sympathetic sudomotor function in amyotrophic lateral sclerosis with electrochemical skin conductance

Hyperhidrosis as the initial symptom in FUS mutation-associated amyotrophic lateral sclerosis: a case report and comprehensive literature review

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that is now recognized to involve autonomic dysfunction. The burden of autonomic dysfunction is an important factor in the quality of life and prognosis of ALS patients. This article presents the clinical characteristics of a young female ALS patient with a fused in sarcoma (FUS) gene mutation and notable hyperhidrosis.

METHOD

Detailed clinical characteristics of the patients were collected, and comprehensive examinations such as electrophysiological assessment, neuro-ultrasound, genetic testing, and relevant blood tests were conducted.

RESULT

A 24-year-old female experienced progressive weakness in both lower limbs for over 5 months, along with excessive sweating on both palms and feet. A positive skin iodine-starch test was observed. Electromyography revealed extensive neurogenic damage and prolonged sympathetic skin response (SSR) latency in both lower limbs. Full exon gene sequencing showed a heterozygous mutation c.1574C>T (p.Pro525Leu) in the FUS gene.

CONCLUSION

The pathogenesis of ALS remains unclear at present. This case underscores the presence of autonomic nervous symptoms in ALS associated with FUS mutation and highlights the importance of early diagnosis and timely treatment intervention to enhance patient prognosis.

Autonomic function in sporadic and familial ALS type 8

OBJECTIVE

To characterize and compare autonomic function in patients with sporadic (sALS) and familial ALS type 8 (fALS8).

METHODS

We selected 11 patients with sALS (7 men), 14 with fALS8 (8 men) and 26 controls (15 men). All groups were gender and age-matched. For each subject, Scale for Outcomes in Parkinson's Disease for Autonomic Symptoms (SCOPA-AUT) was applied and data from heart rate variability, Quantitative Sudomotor Axon Reflex Test (QSART) and skin sympathetic response (SSR) were collected. These data were compared across groups using nonparametric tests. P-values < 0.05 were considered significant.

RESULTS

SCOPA-AUT revealed predominant clinical complaints in thermoregulatory, pupillomotor and sexual domains in fALS8 relative to sALS as well as controls. Neurophysiological tests demonstrated significant differences in Valsalva ratio, Expiratory:Inspiratory index and RR minimum values in both ALS groups relative to controls. Sudomotor dysfunction was also observed in sALS and fALS8 groups, as shown by reduced medial forearm and foot QSART volumes and absence of SSR in lower limbs.

CONCLUSIONS

Dysautonomia - cardiac and sudomotor - is part of the phenotype in sALS and fALS8. The profile of autonomic symptoms, however, is different in each group.

SIGNIFICANCE

Patients with fALS8 and sALS have autonomic dysfunction involving both sympathetic and parasympathetic divisions.

Dysautonomia in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease, characterized in its typical presentation by a combination of lower and upper motor neuron symptoms, with a progressive course and fatal outcome. Due to increased recognition of the non-motor symptoms, it is currently considered a multisystem disorder with great heterogeneity, regarding genetical, clinical, and neuropathological features. Often underestimated, autonomic signs and symptoms have been described in patients with ALS, and various method analyses have been used to assess autonomic nervous system involvement. The aim of this paper is to offer a narrative literature review on autonomic disturbances in ALS, based on the scarce data available to date.

The value of electrochemical skin conductance measurement by Sudoscan® for assessing autonomic dysfunction in peripheral neuropathies beyond diabetes

The diagnosis and follow-up of peripheral neuropathies involving small-diameter nerve fibers require specific examinations beyond conventional nerve conduction studies which only concern large-diameter nerve fibers. Among these tests, some are dedicated to the investigation of cutaneous innervation by the autonomic nervous system, mainly by unmyelinated sympathetic C fibers. To this end, various laboratory tests have been proposed, but the measurement of electrochemical skin conductance (ESC) by Sudoscan® is increasingly becoming the most widely used technique, because it allows a quick and simple assessment of the sudomotor function of the limb extremities. This technique is based on the principles of reverse iontophoresis and chronoamperometry and since its introduction in 2010, has been the source of nearly 200 publications. In the clinical field, most of these publications concern the evaluation of diabetic polyneuropathy, for which the value of Sudoscan® no longer needs to be demonstrated. However, there is also evidence for a role for Sudoscan® in the testing of the autonomic nervous system in various peripheral neuropathies of other origins or diseases primarily affecting the central nervous system. In this article, a comprehensive review of the literature on the clinical value of Sudoscan® outside of diabetes is presented, detailing ESC changes in neuropathies associated with various clinical conditions, such as hereditary amyloidosis or other genetic pathologies, chemotherapy neurotoxicity, dysimmune or infectious disorders, fibromyalgia, parkinsonism or other neurodegenerative diseases.

Autonome Diagnostik bei der Amyotrophen Lateralsklerose

Bei der Amyotrophen Lateralsklerose (ALS) handelt sich um eine neurodegenerative Multisystemerkrankung. Diese äußert sich neben den motorischen Defiziten mit nicht-motorischen Symptomen. Hierzu zählen auch autonome Störungen, die von veränderter Schweißsekretion über Tachykardie bis zu gastrointestinalen Symptomen reichen. Autonome Störungen können mit verschiedenen Methoden, wie Selbsterhebungsfragebögen, Messung der Herzfrequenzvariabilität, QTc-Intervallmessung, Erhebung der sudomotorischen Funktion und Sonographie des Nervus vagus erfasst werden, die in diesem Artikel dargestellt werden. Die bislang bei der ALS eingesetzten Methoden der autonomen Diagnostik ergeben zum Teil deutlich divergierende Ergebnisse über die Aktivität des Sympathikus im Krankheitsverlauf. Relevante autonome Störungen scheinen zumeist erst im fortgeschrittenen Krankheitsstadium aufzutreten, wobei multizentrische Studien mit longitudinalem Ansatz ausstehen.

Stereological and electrophysiological evaluation of autonomic involvement in amyotrophic lateral sclerosis

OBJECTIVE

Previous studies have identified autonomic dysfunction in amyotrophic lateral sclerosis (ALS) using mostly neurophysiological techniques. In this study, stereological evaluation of autonomic fibers and sweat glands has been performed to identify structural evidence of autonomic denervation in patients with ALS.

METHODS

In this study, 29 ALS patients were compared to 29 controls using COMPASS-31 questionnaire, sympathetic skin response (SSR), and heart rate variability (HRV) at rest. From the same cohorts, 20 ALS patients and 15 controls were further evaluated using staining of autonomic nerve fibers and sweat glands in skin biopsies. SSR and resting HRV were repeated in the ALS patient cohort one year later.

RESULTS

COMPASS-31 total score, gastrointestinal- and urinary-sub scores were higher in ALS patients than controls (P = 0.004, P = 0.005, and P = 0.049, respectively). In the ALS patient cohort, SSR amplitudes in hands and feet were lower than in controls (P<0.0001 and P = 0.0009, respectively), but there was no difference in resting HRV (P>0.05). While there was no change in nerve fibers innervating sweat glands, their density was lower in ALS patients than controls, and semi-quantitative analysis also showed structural damage (P = 0.02 and P = 0.001, respectively). SSR and resting HRV of ALS patients remained stable during the one-year follow-up period (P>0.05).

DISCUSSION

Supporting abnormal neurophysiological tests, stereological analysis revealed direct evidence of autonomic denervation in ALS patients. However, the degenerative process in autonomic nerve fibers is relatively slow, compared to the rate of motor neuron degeneration in this condition.