Small fiber involvement is independent from clinical pain in late-onset Pompe disease.

BACKGROUND: Pain occurs in the majority of patients with late onset Pompe disease (LOPD) and is associated with a reduced quality of life. The aim of this study was to analyse the pain characteristics and its relation to a small nerve fiber involvement in LOPD patients. METHODS: In 35 patients with LOPD under enzyme replacement therapy without clinical signs of polyneuropathy (19 females; 51 ± 15 years), pain characteristics as well as depressive and anxiety symptoms were assessed using the PainDetect questionnaire (PDQ) and the hospital anxiety and depression scale (HADS), respectively. Distal skin biopsies were analysed for intraepidermal nerve fiber density (IENFD) and compared to age- and gender-matched reference data. Skin biopsies from 20 healthy subjects served as controls to assure validity of the morphometric analysis. RESULTS: Pain was reported in 69% of the patients with an average intensity of 4.1 ± 1.1 on the numeric rating scale (NRS; anchors: 0-10). According to PDQ, neuropathic pain was likely in one patient, possible in 29%, and unlikely in 67%. Relevant depression and anxiety symptoms occurred in 31% and 23%, respectively, and correlated with pain intensity. Distal IENFD (3.98 ± 1.95 fibers/mm) was reduced in 57% of the patients. The degree of IENFD reduction did not correlate with the durations of symptoms to ERT or duration of ERT to biopsy. CONCLUSIONS: Pain is a frequent symptom in treated LOPD on ERT, though a screening questionnaire seldom indicated neuropathic pain. The high frequency of small nerve fiber pathology in a treated LOPD cohort was found regardless of the presence of pain or comorbid risk factors for SFN and needs further exploration in terms of clinical context, exact mechanisms and when developing novel therapeutic options for LOPD.

Neurological outcomes 1 year after COVID-19 diagnosis: A prospective longitudinal cohort study.

BACKGROUND AND PURPOSE: Neurological sequelae from coronavirus disease 2019 (COVID-19) may persist after recovery from acute infection. Here, the aim was to describe the natural history of neurological manifestations over 1 year after COVID-19. METHODS: A prospective, multicentre, longitudinal cohort study in COVID-19 survivors was performed. At a 3-month and 1-year follow-up, patients were assessed for neurological impairments by a neurological examination and a standardized test battery including the assessment of hyposmia (16-item Sniffin' Sticks test), cognitive deficits (Montreal Cognitive Assessment < 26) and mental health (Hospital Anxiety and Depression Scale and Post-traumatic Stress Disorder Checklist 5). RESULTS: Eighty-one patients were evaluated 1 year after COVID-19, out of which 76 (94%) patients completed a 3-month and 1-year follow-up. Patients were 54 (47-64) years old and 59% were male. New and persistent neurological disorders were found in 15% (3 months) and 12% (10/81; 1 year). Symptoms at 1-year follow-up were reported by 48/81 (59%) patients, including fatigue (38%), concentration difficulties (25%), forgetfulness (25%), sleep disturbances (22%), myalgia (17%), limb weakness (17%), headache (16%), impaired sensation (16%) and hyposmia (15%). Neurological examination revealed findings in 52/81 (64%) patients without improvement over time (3 months, 61%, p = 0.230) including objective hyposmia (Sniffin' Sticks test <13; 51%). Cognitive deficits were apparent in 18%, whereas signs of depression, anxiety and post-traumatic stress disorders were found in 6%, 29% and 10% respectively 1 year after infection. These mental and cognitive disorders had not improved after the 3-month follow-up (all p > 0.05). CONCLUSION: Our data indicate that a significant patient number still suffer from neurological sequelae including neuropsychiatric symptoms 1 year after COVID-19 calling for interdisciplinary management of these patients.

Signs of sympathetic and endothelial cell activation in the skin of patients with restless legs syndrome.

OBJECTIVES: To evaluate skin biopsies of patients with early- and late onset restless legs syndrome (RLS) for concomitant small fiber neuropathy (SFN) and to determine cutaneous sympathetic innervation and microvascularization in comparison to healthy individuals. METHODS: Density of intraepidermal nerve fibers (IENFD), adrenergic nerve fibers and dermal capillaries was analyzed by immunofluorescence for PGP9.5, tyrosine hydroxylase and endothelial markers CD31 and CD105 in skin biopsies of 11 individuals with RLS and 8 age- and sex-matched controls. RESULTS: IENFD did not differ between RLS and controls, but two RLS patients with comorbid impaired glucose metabolism fulfilled morphometric criteria of SFN according to published normative values. In contrast, dermal nerve bundles of RLS patients showed an increased density of tyrosine hydroxylase+ adrenergic nerve fibers (p < 0.005). Moreover, an increased ratio between immature CD105+ and mature CD31+ endothelial cells within dermal capillaries was observed in RLS (p < 0.02). CONCLUSIONS: SFN, as a potential contributing factor for RLS, should be considered in patients with predisposing comorbidities presenting with burning or shooting pain, dysesthesias and impaired sensory and temperature perception. Evidence of an increased adrenergic innervation of the skin in RLS patients is in accordance with sympathetic hyperactivity while signs of endothelial cell activation may reflect an adaptive response to tissue hypoxia.

Muscle involvement in SARS-CoV-2 infection.

BACKGROUND AND PURPOSE: Since the outbreak of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic, several reports indicated neurological involvement in COVID-19 disease. Muscle involvement has also been reported as evidenced by creatine kinase (CK) elevations and reports of myalgia. METHODS: Creatine kinase, markers of inflammation, pre-existing diseases and statin use were extracted from records of Austrian hospitalised COVID-19 patients. Disease severity was classified as severe in case of intensive care unit (ICU) admission or mortality. COVID-19 patients were additionally compared to an historical group of hospitalised influenza patients. RESULTS: Three hundred fifty-one patients with SARS-CoV-2 and 258 with influenza were included in the final analysis. CK was elevated in 27% of COVID-19 and in 28% of influenza patients. CK was higher in severe COVID-19 as were markers of inflammation. CK correlated significantly with inflammation markers, which had an independent impact on CK when adjusted for demographic variables and disease severity. Compared to influenza patients, COVID-19 patients were older, more frequently male, had more comorbidities, and more frequently had a severe disease course. Nevertheless, influenza patients had higher baseline CK than COVID-19, and 35.7% of intensive care unit (ICU)-admitted patients had CK levels >1,000 U/L compared to only 4.7% of ICU-admitted COVID-19 patients. CONCLUSIONS: HyperCKemia occurs in a similar frequency in COVID-19 and influenza infection. CK levels were lower in COVID-19 than in influenza in mild and severe disease. CK levels strongly correlate with disease severity and markers of inflammation. To date, it remains unclear whether hyperCKemia is due to a virus-triggered inflammatory response or direct muscle toxicity.

Laboratory Tests for Neuropathies: What to do and to Avoid.

OBJECTIVES: laboratory tests for work-up of hereditary and acquired neuropathies of peripheral nerves are frequently uncritically utilized. This overview focuses on the most common laboratory tests and investigations needed for diagnosing PNPs by the general neurologist. METHOD: Literature search. RESULTS: laboratory tests recommended for the work-up of hereditary and acquired neuropathies should be chosen according to the individual and family history, clinical presentation, and electrophysiological findings. Laboratory tests should be selected specifically according to the suspected type of neuropathy to avoid unnecessary tests and expenses. Work-up should include as few samples as necessary for uncovering the etiology and should consider the sensitivity/specificity of the tests applied.. Basic screening tests for neuropathies should include a blood cell count, thyroid, renal and liver function tests, blood glucose levels, HbA1c, vitamin-B12, and immunofixation. Other laboratory investigations should be carried out only if a specific phenotype is present or if unexpected changes of the disease course occur. In these cases referral to a neuromuscular center is recommended. CONCLUSIONS: Laboratory tests are helpful for the diagnosis of acquired and hereditary neuropathies but these tests should be ordered according to the history, clinical presentation and findings on electrophysiological investigations. If basic laboratory parameters fail to uncover the etiology, patients should be referred to a center specialized in neuromuscular disorders.

Pattern of myogenesis and vascular repair in early and advanced lesions of juvenile dermatomyositis.

Regenerative processes that counteract perifascicular muscle atrophy and capillary loss in juvenile dermatomyositis (JDM) are not well characterized. We aimed to analyze the pattern of myo-regeneration in relation to vascular damage and repair in muscle specimens from JDM patients. Myogenic regulatory factors that are sequentially expressed during myogenesis were studied by immunohistochemistry. Capillary density, numbers of CD34+ endothelial progenitor cells within the endomysium and molecules implicated in angiogenesis were evaluated by double-immunofluorescence techniques. Myogenic regulatory factors were significantly up-regulated in JDM muscle exhibiting a different pattern in early and advanced lesions. In early lesions Pax7+ satellite cells and both MyoD+ and Myogenin+ myogenic cells were moderately increased. In lesions with advanced perifascicular atrophy Pax7+ satellite cells were numerous, but absence of MyoD+ in the context of increased Myogenin+ expression suggested a dysregulation of the myogenic regenerative pathway. The overall capillary density in JDM was decreased, but regions of capillary loss in advanced lesions alternated with focal increase of hyperplastic endothelial cells in early lesions. Up-regulation of endoglin in hyperplastic endothelial cells in conjunction with overexpression of TGF-ß1 and VEGF suggested activation of neovascularization. Conversely, CD34+ endothelial progenitor cells were not increased arguing against relevant contribution to vascular repair. Our results demonstrate substantial induction of myogenesis in JDM. While the early phase of myogenesis appears to be associated with endothelial cell activation, an altered expression of MRFs in perifascicular regions with capillary depletion suggests an impairment of myogenic differentiation that may contribute to perifascicular muscle fiber atrophy in JDM.

De novo PMP2 mutations in families with type 1 Charcot-Marie-Tooth disease.

We performed whole exome sequencing on a patient with Charcot-Marie-Tooth disease type 1 and identified a de novo mutation in PMP2, the gene that encodes the myelin P2 protein. This mutation (p.Ile52Thr) was passed from the proband to his one affected son, and segregates with clinical and electrophysiological evidence of demyelinating neuropathy. We then screened a cohort of 136 European probands with uncharacterized genetic cause of Charcot-Marie-Tooth disease and identified another family with Charcot-Marie-Tooth disease type 1 that has a mutation affecting an adjacent amino acid (p.Thr51Pro), which segregates with disease. Our genetic and clinical findings in these kindred demonstrate that dominant PMP2 mutations cause Charcot-Marie-Tooth disease type 1.

Expression of myogenic regulatory factors and myo-endothelial remodeling in sporadic inclusion body myositis.

Muscle repair relies on coordinated activation and differentiation of satellite cells, a process that is unable to counterbalance progressive degeneration in sporadic inclusion body myositis (s-IBM). To explore features of myo regeneration, the expression of myogenic regulatory factors Pax7, MyoD and Myogenin and markers of regenerating fibers was analyzed by immunohistochemistry in s-IBM muscle compared with polymyositis, dermatomyositis, muscular dystrophy and age-matched controls. In addition, the capillary density and number of interstitial CD34(+) hematopoietic progenitor cells was determined by double-immunoflourescence staining. Satellite cells and regenerating fibers were significantly increased in s-IBM similar to other inflammatory myopathies and correlated with the intensity of inflammation (R>0.428). Expression of MyoD, visualizing activated satellite cells and proliferating myoblasts, was lower in s-IBM compared to polymyosits. In contrast, Myogenin a marker of myogenic cell differentiation was strongly up-regulated in s-IBM muscle. The microvascular architecture in s-IBM was distorted, although the capillary density was normal. Notably, CD34(+) hematopoietic cells were significantly increased in the interstitial compartment. Our findings indicate profound myo-endothelial remodeling of s-IBM muscle concomitant to inflammation. An altered expression of myogenic regulatory factors involved in satellite cell activation and differentiation, however, might reflect perturbations of muscle repair in s-IBM.

Endothelial and myogenic differentiation of hematopoietic progenitor cells in inflammatory myopathies.

Incorporation of circulating hematopoietic progenitor cells (HPCs) into damaged skeletal muscle has been proposed as a novel mechanism of tissue repair complementary to satellite cell-dependent regeneration. We studied the occurrence and myoendothelial differentiation of HPCs in muscle of patients with inflammatory myopathies. Muscle biopsies from untreated patients with dermatomyositis, polymyositis, inclusion body myositis, and controls were investigated for the expression of endothelial (CD31, von Willebrand factor, vascular endothelial growth factor receptor 2), hematopoietic (CD34, CD133, CD45), and myogenic (Pax7, MyoD) markers by immunohistochemistry and reverse-transcriptase-polymerase chain reaction. Confocal laser scanning microscopy was used to visualize coexpression of CD34, CD133, von Willebrand factor, or Pax7 on individual cells. Morphometric analysis revealed significantly increased numbers of CD133 cells per square millimeter in polymyositis and inclusion body myositis compared with controls (p < 0.001); this correlated with the density of CD45 infiltrates (p < 0.001). By confocal laser scanning microscopy, we detected several mononuclear cells that coexpressed either CD34/von Willebrand factor or CD133/Pax7 with or without CD34 reactivity, indicating endothelial or myogenic commitment of some HPCs in skeletal muscle. Rarely, CD133/CD34/Pax7 cells seemed to occupy satellite cell niches or to incorporate into preexisting myofibers. Our findings suggest that circulating HPCs colonize skeletal muscle in inflammatory conditions and provide evidence for in situ myoendothelial differentiation of some of these cells.

Clinical and electrophysiological features in Charcot-Marie-Tooth disease with mutations in the NEFL gene.

BACKGROUND: To date, 13 different neurofilament light-chain polypeptide gene (NEFL) mutations have been identified in 55 patients with Charcot-Marie-Tooth disease (CMT) from 16 families. NEFL mutations were found to be associated with axonal and demyelinating variants of CMT. OBJECTIVES: To describe the clinical features of 11 patients with CMT and NEFL mutations and to explore possible genotype-phenotype correlations. DESIGN: Standardized neuromuscular and nerve conduction studies were performed, and the coding regions of the peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ), gap junction beta-1 protein (GJB1), and NEFL genes were analyzed by direct DNA sequencing. SETTING: Two university hospitals in Austria (referral centers for neuromuscular disorders). Patients Eleven patients with CMT and NEFL mutations. Main Outcome Measure We genotyped NEFL in all of the patients and healthy relatives and correlated the genotype with the phenotype. RESULTS: A novel NEFL mutation (p.L93P) was detected in 1 family with 4 affected individuals exhibiting a severe CMT phenotype. Nerve conduction velocities were intermediately slowed to a range of 35 to 39 m/s. In a second family and in a sporadic patient, a p.P8R mutation was identified with intermediate and severe nerve conduction slowing. CONCLUSION: The results argue against an obvious genotype-phenotype correlation regarding disease onset, degree of muscle weakness, and nerve conduction slowing caused by NEFL mutations.