Genetic Determined Iron Starvation Signature in Friedreich's Ataxia.

BACKGROUND: Early studies in cellular models suggested an iron accumulation in Friedreich's ataxia (FA), yet findings from patients are lacking. OBJECTIVES: The objective is to characterize systemic iron metabolism, body iron storages, and intracellular iron regulation in FA patients. METHODS: In FA patients and matched healthy controls, we assessed serum iron parameters, regulatory hormones as well as the expression of regulatory proteins and iron distribution in peripheral blood mononuclear cells (PBMCs). We applied magnetic resonance imaging with R2*-relaxometry to quantify iron storages in the liver, spleen, and pancreas. Across all evaluations, we assessed the influence of the genetic severity as expressed by the length of the shorter GAA-expansion (GAA1). RESULTS: We recruited 40 FA patients (19 women). Compared to controls, FA patients displayed lower serum iron and transferrin saturation. Serum ferritin, hepcidin, mean corpuscular hemoglobin and mean corpuscular volume in FA inversely correlated with the GAA1-repeat length, indicating iron deficiency and restricted availability for erythropoiesis with increasing genetic severity. R2*-relaxometry revealed a reduction of splenic and hepatic iron stores in FA. Liver and spleen R2* values inversely correlated with the GAA1-repeat length. FA PBMCs displayed downregulation of ferritin and upregulation of transferrin receptor and divalent metal transporter-1 mRNA, particularly in patients with >500 GAA1-repeats. In FA PBMCs, intracellular iron was not increased, but shifted toward mitochondria. CONCLUSIONS: We provide evidence for a previously unrecognized iron starvation signature at systemic and cellular levels in FA patients, which is related to the underlying genetic severity. These findings challenge the use of systemic iron lowering therapies in FA. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Predictors of Survival in Friedreich's Ataxia: A Prospective Cohort Study.

BACKGROUND: Friedreich's ataxia (FA) is a rare multisystemic disorder which can cause premature death. OBJECTIVES: To investigate predictors of survival in FA. METHODS: Within a prospective registry established by the European Friedreich's Ataxia Consortium for Translational Studies (EFACTS; ClinicalTrials.gov identifier NCT02069509) we enrolled genetically confirmed FA patients at 11 tertiary centers and followed them in yearly intervals. We investigated overall survival applying the Kaplan-Meier method, life tables, and log-rank test. We explored prognostic factors applying Cox proportional hazards regression and subsequently built a risk score which was assessed for discrimination and calibration performance. RESULTS: Between September 2010 and March 2017, we enrolled 631 FA patients. Median age at inclusion was 31 (range, 6-76) years. Until December 2022, 44 patients died and 119 terminated the study for other reasons. The 10-year cumulative survival rate was 87%. In a multivariable analysis, the disability stage (hazard ratio [HR] 1.51, 95% CI 1.08-2.12, P = 0.02), history of arrhythmic disorder (HR 2.93, 95% CI 1.34-6.39, P = 0.007), and diabetes mellitus (HR 2.31, 95% CI 1.05-5.10, P = 0.04) were independent predictors of survival. GAA repeat lengths did not improve the survival model. A risk score built on the previously described factors plus the presence of left ventricular systolic dysfunction at echocardiography enabled identification of four trajectories to prognosticate up to 10-year survival (log-rank test P < 0.001). CONCLUSIONS: Arrhythmias, progressive neurological disability, and diabetes mellitus influence the overall survival in FA. We built a survival prognostic score which identifies patients meriting closer surveillance and who may benefit from early invasive cardiac monitoring and therapy. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Skeletal muscle proteome analysis underpins multifaceted mitochondrial dysfunction in Friedreich's ataxia.

Friedreich's ataxia (FRDA) is a severe multisystemic disorder caused by a deficiency of the mitochondrial protein frataxin. While some aspects of FRDA pathology are developmental, the causes underlying the steady progression are unclear. The inaccessibility of key affected tissues to sampling is a main hurdle. Skeletal muscle displays a disease phenotype and may be sampled in vivo to address open questions on FRDA pathophysiology. Thus, we performed a quantitative mass spectrometry-based proteomics analysis in gastrocnemius skeletal muscle biopsies from genetically confirmed FRDA patients (n = 5) and controls. Obtained data files were processed using Proteome Discoverer and searched by Sequest HT engine against a UniProt human reference proteome database. Comparing skeletal muscle proteomics profiles between FRDA and controls, we identified 228 significant differentially expressed (DE) proteins, of which 227 were downregulated in FRDA. Principal component analysis showed a clear separation between FRDA and control samples. Interactome analysis revealed clustering of DE proteins in oxidative phosphorylation, ribosomal elements, mitochondrial architecture control, and fission/fusion pathways. DE findings in the muscle-specific proteomics suggested a shift toward fast-twitching glycolytic fibers. Notably, most DE proteins (169/228, 74%) are target of the transcription factor nuclear factor-erythroid 2. Our data corroborate a mitochondrial biosignature of FRDA, which extends beyond a mere oxidative phosphorylation failure. Skeletal muscle proteomics highlighted a derangement of mitochondrial architecture and maintenance pathways and a likely adaptive metabolic shift of contractile proteins. The present findings are relevant for the design of future therapeutic strategies and highlight the value of skeletal muscle-omics as disease state readout in FRDA.

Extreme phenotypic heterogeneity in non-expansion spinocerebellar ataxias.

Although the best-known spinocerebellar ataxias (SCAs) are triplet repeat diseases, many SCAs are not caused by repeat expansions. The rarity of individual non-expansion SCAs, however, has made it difficult to discern genotype-phenotype correlations. We therefore screened individuals who had been found to bear variants in a non-expansion SCA-associated gene through genetic testing, and after we eliminated genetic groups that had fewer than 30 subjects, there were 756 subjects bearing single-nucleotide variants or deletions in one of seven genes: CACNA1A (239 subjects), PRKCG (175), AFG3L2 (101), ITPR1 (91), STUB1 (77), SPTBN2 (39), or KCNC3 (34). We compared age at onset, disease features, and progression by gene and variant. There were no features that reliably distinguished one of these SCAs from another, and several genes-CACNA1A, ITPR1, SPTBN2, and KCNC3-were associated with both adult-onset and infantile-onset forms of disease, which also differed in presentation. Nevertheless, progression was overall very slow, and STUB1-associated disease was the fastest. Several variants in CACNA1A showed particularly wide ranges in age at onset: one variant produced anything from infantile developmental delay to ataxia onset at 64 years of age within the same family. For CACNA1A, ITPR1, and SPTBN2, the type of variant and charge change on the protein greatly affected the phenotype, defying pathogenicity prediction algorithms. Even with next-generation sequencing, accurate diagnosis requires dialogue between the clinician and the geneticist.

Skeletal muscle transcriptomics dissects the pathogenesis of Friedreich's ataxia.

OBJECTIVE: In Friedreich's ataxia (FRDA), the most affected tissues are not accessible to sampling and available transcriptomic findings originate from blood-derived cells and animal models. Herein, we aimed at dissecting for the first time the pathophysiology of FRDA by means of RNA-sequencing in an affected tissue sampled in vivo. METHODS: Skeletal muscle biopsies were collected from seven FRDA patients before and after treatment with recombinant human Erythropoietin (rhuEPO) within a clinical trial. Total RNA extraction, 3'-mRNA library preparation and sequencing were performed according to standard procedures. We tested for differential gene expression with DESeq2 and performed gene set enrichment analysis with respect to control subjects. RESULTS: FRDA transcriptomes showed 1873 genes differentially expressed from controls. Two main signatures emerged: (1) a global downregulation of the mitochondrial transcriptome as well as of ribosome/translational machinery and (2) an upregulation of genes related to transcription and chromatin regulation, especially of repressor terms. Downregulation of the mitochondrial transcriptome was more profound than previously shown in other cellular systems. Furthermore, we observed in FRDA patients a marked upregulation of leptin, the master regulator of energy homeostasis. RhuEPO treatment further enhanced leptin expression. INTERPRETATION: Our findings reflect a double hit in the pathophysiology of FRDA: a transcriptional/translational issue and a profound mitochondrial failure downstream. Leptin upregulation in the skeletal muscle in FRDA may represent a compensatory mechanism of mitochondrial dysfunction, which is amenable to pharmacological boosting. Skeletal muscle transcriptomics is a valuable biomarker to monitor therapeutic interventions in FRDA.

Toward the Definition of Patient-Reported Outcome Measurements in Hereditary Spastic Paraplegia.

Background and Objectives: Hereditary spastic paraplegias (HSPs) are a heterogeneous group of rare neurodegenerative diseases, characterized by a progressive spastic paraparesis. Currently, there is a HSP-specific clinician-reported outcome measure (CROM) called Spastic Paraplegia Rating Scale (SPRS). There are, however, no specific patient-reported outcome measures (PROMs) for HSP. In the present cohort study, we prospectively follow up a well-examined Austrian HSP cohort using validated rating scales and compared PROM with disease-specific and non-disease-specific CROM. Methods: Patients were recruited and followed up at the Center for Rare Movement Disorders, Innsbruck, Austria. CROM included the SPRS, Scale for the Assessment and Rating of Ataxia (SARA), Barthel Index (BI), and Mini-Mental State Examination (MMSE). PROM included the EQ-5D questionnaire and the Patient Health Questionnaire 9 (PHQ-9). Standardized response means (SRMs) were calculated for all scales at follow-up (FU) after 1 year. Results: A total of 55 patients (36 males) with HSP were included in the study. FU was performed for 30 patients (21 males). Apart from females reporting more problems in the EQ-5D domain of anxiety and depression (p = 0.008), other clinician-reported outcomes (CROs) or patient-reported outcomes (PROs) did not differ significantly across sex. SPRS showed significant correlations with SARA (p < 0.001), mainly driven by the gait item, as well as the BI. Although SPRS did not correlate with EQ-5D visual analogue scale and PHQ-9 scores, several EQ-5D domains correlated significantly with SPRS. At FU, SPRS showed the highest responsiveness (SRM 1.11), followed by SARA (SRM 0.47). Neither MMSE nor PRO significantly increased at FU. Discussion: In this study, we present an Austrian cohort of patients with HSP and a prospective study evaluating correlations of CRO and PRO as well as their progression. Demographics from our cohort are comparable with several other European cohort studies. Our data highlight the capabilities of the SPRS to show clinical progression and warrant consideration of ataxia rating scales such as SARA in HSP cohorts. We also show that the generic PROMs are not suitable to detect change in HSP, and thus, we propose to create a disease-specific PROM fully depicting the effect of HSP on the patients' lives.

Untangling neurodevelopmental disorders in the adulthood: a movement disorder is the clue.

BACKGROUND: The genetic landscape of neurodevelopmental disorders is constantly expanding and children with early-onset neurological phenotypes increasingly receive a genetic diagnosis. Nonetheless, the awareness of the chronic course of these conditions, and consequently their recognition and management in the adult population, is still limited. RESULTS: Herein, we describe four patients with rare neurodevelopmental disorders (SON, ZMYND11, DNMT1 and YY1-related diseases), who received a genetic assignment only in the adulthood. All these patients had an early developmental delay and displayed a movement disorder (dystonia/ataxia/tremor) which manifested for the first time, or worsened, in the adulthood, prompting the referral to a neurologist. This phenotypic combination led eventually to the genetic testing. We report previously unrecognized features and highlight the peculiarities of the adult presentation of four neurodevelopmental disorders. CONCLUSIONS: This report expands the current knowledge on four rare neurodevelopmental disorders (SON, ZMYND11, DNMT1 and YY1), which was mainly based on reports from paediatric cases. This case series emphasize the importance of a tight neurological surveillance extending beyond the childhood.

Instrumented gait analysis defines the walking signature of CACNA1A disorders.

BACKGROUND: Gait disturbances are a frequent symptom in CACNA1A disorders. Even though, data about their severity and progression are lacking and no CACNA1A-specific scale or assessment for gait is available. METHODS: We applied a gait assessment protocol in 20 ambulatory patients with genetically confirmed CACNA1A disorders and 39 matched healthy controls. An instrumented gait analysis (IGA) was performed by means of wearable sensors in basal condition and after a treadmill/cycloergometer challenge in selected cases. RESULTS: CACNA1A patients displayed lower gait speed, shorter steps with increased step length variability, a reduced landing acceleration as well as a reduced range of ankle motion compared to controls. Furthermore, gait-width in patients with episodic CACNA1A disorders was narrower as compared to controls. In one patient experiencing mild episodic symptoms after the treadmill challenge, the IGA was able to detect a deterioration over all gait parameters. CONCLUSIONS: In CACNA1A patients, the IGA with wearable sensors unravels specific gait signatures which are not detectable at naked eye. These features (narrow-based gait, lower landing acceleration) distinguish these patients from other ataxic disorders and may be target of focused rehabilitative interventions. IGA can potentially be applied to monitor the neurological fluctuations associated with CACNA1A disorders.

The rare and the common: An Austrian DRPLA family harboring the European haplotype.

Dentatorubral-pallidoluysian atrophy (DRPLA) is a CAG trinucleotide repeat expansion disorder with an autosomal-dominant mode of inheritance and very low prevalence in Europe. We herein report the clinical characteristics of the first Austrian DRPLA family. Genetic analysis revealed the presence of a common European haplotype, suggesting a founder mutation in Europe.

The electrophysiological footprint of CACNA1A disorders.

OBJECTIVES: CACNA1A variants underlie three neurological disorders: familial hemiplegic migraine type 1 (FHM1), episodic ataxia type 2 (EA2) and spinocerebellar ataxia type 6 (SCA6). EEG is applied to study their episodic manifestations, but findings in the intervals did not gain attention up to date. METHODS: We analyzed repeated EEG recordings performed between 1994 and 2019 in a large cohort of genetically confirmed CACNA1A patients. EEG findings were compared with those of CACNA1A-negative phenocopies. A review of the related literature was performed. RESULTS: 85 EEG recordings from 38 patients (19 EA2, 14 FHM1, 5 SCA6) were analyzed. Baseline EEG was abnormal in 55% of cases (12 EA2, 9 FHM1). The most common finding was a lateralized intermittent slowing, mainly affecting the temporal region. Slowing was more pronounced after a recent attack but was consistently detected in the majority of patients also during the follow-up. Interictal epileptic discharges (IEDs) were detected in eight patients (7 EA2,1 FHM1). EEG abnormalities and especially IEDs were significantly associated with younger age at examination (16 ± 9 vs 43 ± 21 years in those without epileptic changes, p = 0.003) and with earlier onset of disease (1 (1-2) vs 12 (5-45) years, p = 0.0009). EEG findings in CACNA1A-negative phenocopies (n = 15) were largely unremarkable (p = 0.03 in the comparison with CACNA1A patients). CONCLUSIONS: EEG abnormalities between attacks are highly prevalent in episodic CACNA1A disorders and especially associated with younger age at examination and earlier disease onset. Our findings underpin an age-dependent effect of CACNA1A variants, with a more severe impairment when P/Q channel dysfunction manifests early in life.

Familial writer's cramp: a clinical clue for inherited coenzyme Q10 deficiency.

The spectrum of coenzyme Q10 (CoQ10) deficiency syndromes comprises a variety of disorders, including a form of autosomal recessive cerebellar ataxia (ARCA2) caused by mutations in the AarF domain-containing kinase 3 gene (ADCK3). Due to the potential response to CoQ10 supplementation, a timely diagnosis is crucial. Herein, we describe two siblings with a novel homozygous ADCK3 variant and an unusual presentation consisting of isolated writer's cramp with adult-onset. Cerebellar ataxia developed later in the disease course and remained stable during the follow-up. This report highlights that ARCA2 should be considered in the differential diagnosis of familial writer's cramp.

Mast Syndrome Outside the Amish Community: SPG21 in Europe.

BACKGROUND: Mast syndrome is a rare disorder belonging to the group of hereditary spastic paraplegias (HSPs). It is caused by bi-allelic mutations in the ACP33 gene, and is originally described in Old Order Amish. Outside this population, only one Japanese and one Italian family have been reported. Herein, we describe five subjects from the first three SPG21 families of German and Austrian descent. METHODS: Five subjects with complicated HSP were referred to our centers. The workup consisted of neurological examination, neurophysiological and neuropsychological assessments, MRI, and genetic testing. RESULTS: Onset varied from child- to adulthood. All patients exhibited predominant spastic para- or tetraparesis with positive pyramidal signs, pronounced cognitive impairment, ataxia, and extrapyramidal signs. Neurophysiological workup showed abnormal motor and sensory evoked potentials in all the patients. Sensorimotor axonal neuropathy was present in one patient. Imaging exhibited thin corpus callosum and global brain atrophy. Genetic testing revealed one heterozygous compound and two homozygous mutations in the ACP33 gene. CONCLUSION: Herein, we report the first three Austrian and two German patients with SPG21, presenting a detailed description of their clinical phenotype and disease course. Our report adds to the knowledge of this extremely rare disorder, and highlights that SPG21 must also be considered in the differential diagnosis of complicated HSP outside the Amish community.

Onset features and time to diagnosis in Friedreich's Ataxia.

BACKGROUND: In rare disorders diagnosis may be delayed due to limited awareness and unspecific presenting symptoms. Herein, we address the issue of diagnostic delay in Friedreich's Ataxia (FRDA), a genetic disorder usually caused by homozygous GAA-repeat expansions. METHODS: Six hundred eleven genetically confirmed FRDA patients were recruited within a multicentric natural history study conducted by the EFACTS (European FRDA Consortium for Translational Studies, ClinicalTrials.gov -Identifier NCT02069509). Age at first symptoms as well as age at first suspicion of FRDA by a physician were collected retrospectively at the baseline visit. RESULTS: In 554 of cases (90.7%), disease presented with gait or coordination disturbances. In the others (n = 57, 9.3%), non-neurological features such as scoliosis or cardiomyopathy predated ataxia. Before the discovery of the causal mutation in 1996, median time to diagnosis was 4(IQR = 2-9) years and it improved significantly after the introduction of genetic testing (2(IQR = 1-5) years, p < 0.001). Still, after 1996, time to diagnosis was longer in patients with a) non-neurological presentation (mean 6.7, 95%CI [5.5,7.9] vs 4.5, [4.2,5] years in those with neurological presentation, p = 0.001) as well as in b) patients with late-onset (3(IQR = 1-7) vs 2(IQR = 1-5) years compared to typical onset < 25 years of age, p = 0.03). Age at onset significantly correlated with the length of the shorter GAA repeat (GAA1) in case of neurological onset (r = - 0,6; p < 0,0001), but not in patients with non-neurological presentation (r = - 0,1; p = 0,4). Across 54 siblings' pairs, differences in age at onset did not correlate with differences in GAA-repeat length (r = - 0,14, p = 0,3). CONCLUSIONS: In the genetic era, presentation with non-neurological features or in the adulthood still leads to a significant diagnostic delay in FRDA. Well-known correlations between GAA1 repeat length and disease milestones are not valid in case of atypical presentations or positive family history.

Cardiovascular autonomic testing in the work-up of cerebellar ataxia: insight from an observational single center study.

BACKGROUND: Cerebellar ataxias are a heterogeneous group of disorders of both genetic and non-genetic origin. In sporadic cases, two entities are recognized: multiple system atrophy of cerebellar type (MSA-C) and SAOA (sporadic adult-onset ataxia). The presence of severe cardiovascular autonomic failure reliably distinguishes MSA-C from other ataxias, but it may appear only late in the disease course. OBJECTIVE: To evaluate the diagnostic yield of cardiovascular autonomic function tests in the work-up of cerebellar ataxia. METHODS: We applied a cardiovascular autonomic tests battery in consecutive patients with neurodegenerative cerebellar ataxia and matched healthy controls. We recorded the presence of both orthostatic hypotension (OH) and blood pressure falls non-fulfilling the criteria of OH (non-OH BP). Sporadic cases were followed-up for an eventual conversion to MSA-C. RESULTS: Forty-two patients were recruited, 19 of whom with sporadic disease (2 probable MSA-C, 6 possible MSA-C, 11 SAOA). Sporadic and hereditary cases showed no difference concerning ataxia severity at baseline. At head-up tilt, non-OH BP falls were detected in nine patients, but not in controls. This finding was significantly more frequent in sporadic cases (p = 0.006) and was detected in five out of seven patients that during follow-up converted to possible/probable MSA-C. Findings at standing test were normal in four out of nine cases with non-OH BP falls at head-up tilt. CONCLUSIONS: A complete cardiovascular autonomic battery with head-up tilt can detect early signs of BP dysregulation which may be missed at bed-side tests, thus warranting its application in the first line work-up of cerebellar ataxias.

Second language learning induces grey matter volume increase in people with multiple sclerosis.

BACKGROUND: Grey matter volume (GMV) decline is a frequent finding in multiple sclerosis (MS), the most common chronic neurological disease in young adults. Increases of GMV were detected in language related brain regions following second language (L2) learning in healthy adults. Effects of L2 learning in people with MS (pwMS) have not been investigated so far. METHODS: This study prospectively evaluated the potential of an eight-week L2 training on grey matter plasticity measured by 3T-MRI, L2 proficiency and health-related quality of life (HRQoL) in people with relapsing-remitting MS (pwMS, n = 11) and healthy, sex- and age-matched controls (HCs; n = 12). RESULTS: Categorical voxel-based analysis revealed significantly less GMV bilaterally of the insula extending to the temporal pole in pwMS at baseline. Following L2 training, significant increases of GMV were evident in the right hippocampus, parahippocampus and putamen of pwMS and in the left insula of HCs. L2 training resulted in significant improvements of listening comprehension, speaking fluency and vocabulary knowledge in both pwMS and HCs. GMV increases of right hippocampus and parahippocampus significantly correlated with vocabulary knowledge gain and L2 learning was associated with a significant increase of HRQoL in pwMS. CONCLUSION: Our findings demonstrate distinct patterns of GMV increases of language related brain regions in pwMS and HCs and indicate disease-related compensatory cortical and subcortical plasticity to acquire L2 proficiency in pwMS.

Change of olfactory function as a marker of inflammatory activity and disability progression in MS.

BACKGROUND: Impaired olfactory threshold has been reported in early inflammatory phases of MS, while impaired odor identification was associated with more widespread disability. OBJECTIVE: To prospectively assess the development of olfactory function and its correlation with relapse and disability progression. METHODS: In this prospective, 3-year longitudinal study on 151 MS patients and 30 healthy controls, three different qualities of olfactory function (threshold, discrimination, and identification) were quantified using the Sniffin' Sticks test. The influence of relapses and disability on olfactory function was analyzed at different time points and in a multivariate model. RESULTS: Discrimination and identification capability significantly worsened over 3 years, while threshold did not. Threshold was markedly impaired in patients with relapse activity within 12 months, recovered in the absence of relapse, and was associated with a 2.5-fold increased risk of relapse. Deterioration of discrimination and identification was irreversible and both strongly associated with and predictive of EDSS progression. CONCLUSION: Olfactory function changes over time in MS. Threshold impairment is transient and predicts inflammatory disease activity, while odor identification and discrimination are associated with disability progression. Olfactory dysfunction might be a useful and easily obtainable parameter to monitor patients with regard to inflammation and neurodegeneration in MS.

Peripapillary retinal nerve fibre layer as measured by optical coherence tomography is a prognostic biomarker not only for physical but also for cognitive disability progression in multiple sclerosis.

BACKGROUND: Peripapillary retinal nerve fibre layer (pRNFL) thickness is emerging as a marker of axonal degeneration in multiple sclerosis (MS). OBJECTIVE: We aimed to prospectively assess the predictive value of pRNFL for progression of physical and cognitive disability in relapsing-remitting MS (RRMS). METHODS: In this 3-year longitudinal study on 151 RRMS patients, pRNFL was measured by spectral-domain optical coherence tomography (OCT). We used proportional hazard models, correcting for age, sex, disease duration, Expanded Disability Status Scale (EDSS) and Symbol Digit Modalities Test (SDMT) at baseline, to test a pRNFL thickness ≤88 µm at baseline for prediction of EDSS progression and cognitive decline. We also evaluated the decrease in pRNFL thickness from baseline to year 3 in a multivariate linear regression model. RESULTS: pRNFL thickness ≤88 µm was independently associated with a threefold increased risk of EDSS progression ( p < 0.001) and a 2.7-fold increased risk of cognitive decline within the subsequent 3 years ( p < 0.001). Mean pRNFL delta was -5.3 µm (SD, 4.2). It was significantly negatively impacted by EDSS progression, cognitive decline, higher age and disease duration, while positively impacted by disease-modifying therapy (DMT). CONCLUSION: Cross-sectional and longitudinal monitoring of pRNFL is useful as a biomarker for prediction of physical and cognitive disability progression in patients with RRMS in everyday clinical practice.

Transient impairment of olfactory threshold in acute multiple sclerosis relapse.

BACKGROUND: Impairment of olfactory threshold is a feature of early and active relapsing remitting multiple sclerosis (RRMS). It predicts inflammatory disease activity and was reported to be transient. However, the timing of onset and resolve of olfactory threshold impairment remains unclear. OBJECTIVE: To prospectively assess the development of olfactory threshold in acute MS relapse over time in comparison to stable MS patients. METHODS: In a prospective observational design, we measured olfactory threshold by performing the Sniffin' Sticks test (minimum score 0, maximum score 16 reflecting optimal olfactory function) at baseline and after 4, 12 and 24 weeks. We included 30 RRMS patients with acute MS relapse and 30 clinically stable RRMS patients (defined as no relapse within the last 12 months) as a control group. RESULTS: Olfactory threshold was impaired in patients with acute MS relapse at baseline (median difference = -3.5; inter-quartile range [IQR] -4.5- - 2.5; p < 0.001), week 4 (-2.5; IQR -3.0 - -2.0; p < 0.001), week 12 (-1.5; IQR -2.0 - -0.5; p = 0.002) and week 24 (-0.5; IQR -1.0 - 0.0; p = 0.159) compared to stable MS patients. Of note, in relapsing patients in whom disease-modifying treatment was initiated or escalated after relapse, threshold did not differ anymore from stable patients at week 12 (-0.5; IQR -1.0 - 0.5; p = 0.247) and week 24 (0.0; IQR -1.0 - 1.0; p = 0.753). CONCLUSIONS: Olfactory threshold impairment seems to be a transient bystander feature of MS relapse. It may be correlated to the level of inflammation within the CNS and might be a useful biomarker in this regard.