Neuromyotonia

Distinct phenotypes in a cohort of anti-CASPR2 associated neurological syndromes

INTRODUCTION

Anti-contactin-associated protein-like 2 (CASPR2) is classically associated with limbic encephalitis (LE), Morvan syndrome and peripheral nerve hyperexcitability (PNH). Additional clinical features have been previously recognized.

OBJECTIVE

To describe a cohort of patients with anti-CASPR2-associated neurological syndromes from a tertiary referral centre.

METHODS

Retrospective analysis of patients with positive serum anti-CASPR2 antibodies in the period between 2014 and 2021.

RESULTS

Nineteen patients were identified, 11 (57.9%) male, with a median age at symptom onset of 49.0 (31.3-63.0) years and a median time to diagnosis of 1.0 (0.0-1.8) years. The most common clinical syndromes were LE (7 cases, 36.8%), Morvan syndrome (4, 21.1%) and PNH (2, 10.5%). Six patients presented with atypical phenotypes (31.6%), comprising dysautonomia (orthostatic hypotension and Adie's Pupil), motor tics/stereotypies, obsessive-compulsive disorder, and brainstem involvement. The most common presenting symptoms were seizures (31.6%), PNH (21.1%) and cognitive dysfunction (15.8%). One LE patient had a disease duration of 2,5 years and was initially diagnosed with dementia. CSF was normal in most cases. Brain MRI showed temporal lobe hyperintensities in 4 LE cases (57.1%). All PNH cases had myokymic discharges of fasciculations in the electromyography. Two patients had associated thymoma and 1 had lung adenocarcinoma. Eight patients (42.1%) received treatment during the acute phase and 26.3% maintenance treatment. Approximately half of the treated cases improved or stabilised, with 4 (21.1%) deaths in the whole cohort.

CONCLUSION

Anti-CASPR2-associated neurological disorders may present with isolated atypical phenotypes, a slowly progressive clinical course, and with normal CSF or imaging findings.

Childhood onset of acquired neuromyotonia: association with vitamin D deficiency

Purpose/Aim: Acquired neuromyotonia or Isaacs syndrome is a type of peripheral nerve hyperexcitability of autoimmune origin. It may occur as an isolated, paraneoplastic or accompanied with some autoimmune diseases. This report describes acquired neuromyotonia in a child with a new reported association with vitamin D deficiency. Case report: A 9-year-old child, in whom the diagnosis of acquired neuromyotonia was made by clinical and typical electromyographic findings. All paraneoplastic and autoimmune workup was normal, except for a vitamin D deficiency state. A dramatic improvement was recorded on both clinical and electrophysiological base after vitamin D replacement. Conclusion: An in-depth future analysis of vitamin D status in patients with neuromyotonia will help to establish whether the association of neuromyotonia with vitamin D deficiency is casual or whether these two conditions may be causally related.

Successful Improvement of Pain Symptomatology in a Suspected Case of Cramp-Fasciculation Syndrome via Interventional Pain Treatment

Peripheral nerve hyperexcitability (PNH) syndromes are a rare set of neuromuscular disorders that include cramp-fasciculation syndrome (CFS) and Isaacs syndrome (IS). Successful treatment of these diseases has been achieved with antiepileptic medications; however, chronic pain symptoms can persist. We provide a case report of a 25-year-old female who has suffered from painful severe muscle spasms and fasciculations since childhood. With CFS as our working diagnosis, a treatment regimen using interventional pain techniques, including sympathetic chain blocks, ketamine infusions, and trigger point injections, resulted in a significant decrease in the patient's chronic pain symptoms. This case offers a novel application of interventional pain procedures and may help further our understanding of PNH syndromes.

[Myasthenia, from the internist's point of view]

Myasthenia gravis is an autoimmune disease due to specific antibodies inducing a neuromuscular transmission defect causing muscle fatigability. If onset of the disease may be at any age, myasthenia gravis concerns mostly young adults, in majority females. The disease characteristic features are the following: ocular symptoms (ptosis or diplopia) as main initial manifestation, extension to other muscles in 80 % of the cases, variability of the deficit, effort induced worsening, successive periods of exacerbation during the disease course, severity depending on respiratory and swallowing impairment (if rapid worsening, a myasthenic crisis is to be suspected), association with thymoma in 20 % of patients and with other various autoimmune diseases, most commonly hyperthyroidism and Hashimoto's disease. Diagnosis relies on the clinical features, improvement with cholinesterase inhibitors, detection of specific autoantibodies (anti-AChR or anti-MuSK), and significant decrement evidenced by electrophysiological tests. The points concerning specifically the internist have been highlighted in this article: diagnostic traps, associated autoimmune diseases, including inflammatory myopathies that may mimic myasthenia gravis, adverse effects of medications commonly used in internal medicine, some of them inducing myasthenic syndromes. The treatment is well codified: the treatment is well codified: (1) respect of adverse drugs contra-indications, systematically use of cholinesterase inhibitors, (2) thymectomy if thymoma completed with radiotherapy if malignant, (3) corticosteroids or immunosuppressive agent in severe or disabling form, (4) intensive care unit monitoring, plasmapheresis or intravenous immunoglobulins for patients with myasthenic crisis.

Autoantibodies to neurotransmitter receptors and ion channels: from neuromuscular to neuropsychiatric disorders

Changes of voltage-gated ion channels and ligand-gated receptor channels caused by mutation or autoimmune attack are the cause of so-called channelopathies in the central and peripheral nervous system. We present the pathophysiology of channelopathies of the neuromuscular junction in terms of loss-of-function and gain-of-function principles. Autoantibodies generally have reduced access to the central nervous system, but in some cases this is enough to cause disease. A review is provided of recent findings implicating autoantibodies against ligand-activated receptor channels and potassium channels in psychiatric and neurological disorders, including schizophrenia and limbic encephalitis. The emergence of channelopathy-related neuropsychiatric disorders has implications for research and practice.

Autoimmune Processes in the Central Nervous System

In this chapter we discuss the factors that contribute to the unique immunological environment of the central nervous system and the mechanisms that may account for the development of autoimmunity within the CNS, including infectious agents as inducers of autoimmune disease. Consideration is given to a variety of human neurological diseases of autoimmune or presumed autoimmune etiology: autism, neuromyelitis optica, neuromyotonia, schizophrenia, lethargic encephalitis and stiff‐man syndrome. Also, we discuss autoimmunity as a possible mediator of CNS repair and examples of the protective effects of bacterial and helminth infections on CNS disease. Multiple sclerosis and models of multiple sclerosis are discussed with special attention given to the Theiler's virus‐induced demyelination model.

Stability studies of ionised and non-ionised 3,4-diaminopyridine: Hypothesis of degradation pathways and chemical structure of degradation products

3,4-Diaminopyridine is used to treat some symptoms met in Lambert-Eaton myasthenia syndrome. It was shown efficient to reduce a form of variable muscle weakness and fatigability typical of the disease and correlated to a block of acetylcholine release. In France, 3,4-diaminopyridine is nowadays given to patients under capsules form and the status of hospital preparation. Whatever the diluant used in the formulation, the stability period could not exceed 12 months. Preliminary studies were made on a salt form in order to test the influence of various stress factors and determine if there is interaction between them. From this study, the most influent stress condition, presence of hydrogen peroxide, was selected and a comparative study was performed to compare the stability of molecular and salt species. Solutions of each species were exposed to 5 or 15% of hydrogen peroxide and analyzed at 8, 24, 72 and 216 h of degradation by HPLC-UV. Fractions of detected impurities were purified and collected by semi-preparative HPLC-UV and analyzed by HPLC-UV-ESI-MS and IR spectroscopy in order to determine their structure hypotheses. Theses experiments demonstrate that the salt species were more stable under oxidative stress condition than molecular species. The two main degradation products were collected and identified as 4-amino, 3-nitropyridine and 3,4-diaminopyridine-N-oxide when the molecular form was degraded whereas only 4-amino, 3-nitropyridine was found in less quantity in the salt solutions. Nitrogen pyridine and pyridine amine could not easily be oxidized by hydrogen peroxide in salt comparatively to molecular species due to the lone pair of electron engaged in a bound with hydrogen in the first case and by resonance change of the pyridine in the second case. This modification of structure promoted different pathways of degradation for the salt form which are more dependent of energy. Owing to the better stability of the salt species, a new pharmaceutical form containing it was developed to assess its stability under ICH standard conditions allowing an industrial manufacture of this drug.

Myotonia congenita--a cause of muscle weakness and stiffness

BACKGROUND

A 56-year-old woman was referred to a neurogenetic clinic with a history of stiffness and transient weakness. A previous needle electromyogram had confirmed the presence of myotonia, but a muscle biopsy had revealed no evidence of dystrophy.

INVESTIGATIONS

Neurological examination, electrophysiological studies and genetic testing.

DIAGNOSIS

Recessive myotonia congenita (Becker's disease).

MANAGEMENT

Explanation of the nature of the disease and treatment with mexiletine 200 mg twice daily.

Oxaliplatin induces hyperexcitability at motor and autonomic neuromuscular junctions through effects on voltage-gated sodium channels

Oxaliplatin, an effective cytotoxic treatment in combination with 5-fluorouracil for colorectal cancer, is associated with sensory, motor and autonomic neurotoxicity. Motor symptoms include hyperexcitability while autonomic effects include urinary retention, but the cause of these side-effects is unknown. We examined the effects on motor nerve function in the mouse hemidiaphragm and on the autonomic system in the vas deferens. In the mouse diaphragm, oxaliplatin (0.5 mM) induced multiple endplate potentials (EPPs) following a single stimulus, and was associated with an increase in spontaneous miniature EPP frequency. In the vas deferens, spontaneous excitatory junction potential frequency was increased after 30 min exposure to oxaliplatin; no changes in resting Ca(2+) concentration in nerve terminal varicosities were observed, and recovery after stimuli trains was unaffected. In both tissues, an oxaliplatin-induced increase in spontaneous activity was prevented by the voltage-gated Na(+) channel blocker tetrodotoxin (TTX). Carbamazepine (0.3 mM) also prevented multiple EPPs and the increase in spontaneous activity in both tissues. In diaphragm, beta-pompilidotoxin (100 microM), which slows Na(+) channel inactivation, induced multiple EPPs similar to oxaliplatin's effect. By contrast, blockers of K(+) channels (4-aminopyridine and apamin) did not replicate oxaliplatin-induced hyperexcitability in the diaphragm. The prevention of hyperexcitability by TTX blockade implies that oxaliplatin acts on nerve conduction rather than by effecting repolarisation. The similarity between beta-pompilidotoxin and oxaliplatin suggests that alteration of voltage-gated Na(+) channel kinetics is likely to underlie the acute neurotoxic actions of oxaliplatin.