Multifocal motor neuropathy as a mimic of amyotrophic lateral sclerosis: Serum neurofilament light chain as a reliable diagnostic biomarker

INTRODUCTION/AIMS

The clinical presentation of multifocal motor neuropathy (MMN) may mimic early amyotrophic lateral sclerosis (ALS) with predominant lower motor neuron (LMN) involvement, posing a diagnostic challenge. Both diseases have specific treatments and prognoses, highlighting the importance of early diagnosis. The aim of this study was to assess the diagnostic value of serum neurofilament light chain (NfL) in differentiating MMN from LMN dominant ALS.

METHODS

NfL was measured in serum in n = 37 patients with MMN and n = 37 age- and sex-matched patients with LMN dominant ALS, to determine the diagnostic accuracy. Clinical and demographic data were obtained at the time of NfL sampling.

RESULTS

Serum NfL concentration was significantly lower in MMN patients compared to ALS patients (mean 20.7 pg/mL vs. 59.4 pg/mL, p < .01). NfL demonstrated good diagnostic value in discriminating the two groups (AUC 0.985 [95% CI 0.963-1.000], sensitivity 94.6%, specificity 100%, cut-off 44.00 pg/mL).

DISCUSSION

NfL could be a helpful tool in differentiating MMN from LMN dominant ALS in those patients in whom electrophysiological and clinical examinations remain inconclusive early in the diagnostic process.

Frequency and Characterization of Movement Disorders in Anti-IgLON5 Disease

BACKGROUND AND OBJECTIVES

Anti-IgLON5 disease is a recently described neurologic disease that shares features of autoimmunity and neurodegeneration. Abnormal movements appear to be frequent and important but have not been characterized and are underreported. We describe the frequency and types of movement disorders in a series of consecutive patients with this disease.

METHODS

In this retrospective, observational study, the presence and phenomenology of movement disorders were assessed with a standardized clinical questionnaire. Available videos were centrally reviewed by 3 experts in movement disorders.

RESULTS

Seventy-two patients were included. In 41 (57%), the main reason for initial consultation was difficulty walking along with one or several concurrent movement disorders. At the time of anti-IgLON5 diagnosis, 63 (87%) patients had at least 1 movement disorder with a median of 3 per patient. The most frequent abnormal movements were gait and balance disturbances (52 patients [72%]), chorea (24 [33%]), bradykinesia (20 [28%]), dystonia (19 [26%]), abnormal body postures or rigidity (18 [25%]), and tremor (15 [21%]). Other hyperkinetic movements (myoclonus, akathisia, myorhythmia, myokymia, or abdominal dyskinesias) occurred in 26 (36%) patients. The craniofacial region was one of the most frequently affected by multiple concurrent movement disorders (23 patients [32%]) including dystonia (13), myorhythmia (6), chorea (4), or myokymia (4). Considering any body region, the most frequent combination of multiple movement disorders consisted of gait instability or ataxia associated with craniofacial dyskinesias or generalized chorea observed in 31 (43%) patients. In addition to abnormal movements, 87% of patients had sleep alterations, 74% bulbar dysfunction, and 53% cognitive impairment. Fifty-five (76%) patients were treated with immunotherapy, resulting in important and sustained improvement of the movement disorders in only 7 (13%) cases.

DISCUSSION

Movement disorders are a frequent and leading cause of initial neurologic consultation in patients with anti-IgLON5 disease. Although multiple types of abnormal movements can occur, the most prevalent are disorders of gait, generalized chorea, and dystonia and other dyskinesias that frequently affect craniofacial muscles. Overall, anti-IgLON5 disease should be considered in patients with multiple movement disorders, particularly if they occur in association with sleep alterations, bulbar dysfunction, or cognitive impairment.

Co-incidental C9orf72 expansion mutation-related frontotemporal lobar degeneration pathology and sporadic Creutzfeldt-Jakob disease

Background

The C9orf72 hexanucleotide expansion mutation is the most common cause of genetic frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS) and combined FTD‐ALS. Its underlying neuropathology combines TDP‐43 pathology and dipeptide repeat protein (DPR) deposits and may also associate with other neurodegeneration‐associated protein aggregates. Herein we present a unique combination of C9orf72 mutation with sporadic Creutzfeldt−Jakob disease (CJD) in a 74‐year‐old patient with rapidly progressive dementia.

Methods

Detailed neuropathological examination including immunohistochemistry for several proteinopathies. Genetic analysis was conducted by repeat primed polymerase chain reaction (PCR). Furthermore, we analyzed additional C9orf72 mutation carriers for prion−protein (PrP) deposits in brain tissue and screened the cerebellar cortex of other CJD cases for p62/DPR neuronal inclusions to assess the frequency of combined pathologies.

Results

Postmortem brain examination of a patient with a rapidly progressive neurological deterioration of 8 months’ duration confirmed the diagnosis of CJD. She harbored valine homozygosity at PRNP codon 129. In addition, a frontotemporal lobar degeneration (FTLD)‐pattern with TDP‐43 protein aggregates and p62+/C9RANT+ positive inclusions along with a high degree of Alzheimer‐related pathology (A3B3C3) were identified. The suspected C9orf72 expansion mutation was confirmed by repeat‐primed PCR. Screening of 13 C9orf72 cases showed no pathological PrP aggregates and screening of 100 CJD cases revealed no other C9orf72 expansion mutation carriers.

Conclusion

A combination of a C9orf72 expansion mutation‐related FTLD with sporadic CJD in the same patient is rare. While the rarity of both diseases makes this concurrence most likely to be coincidental, questions regarding a potential link between these two neurodegenerative pathologies deserve further studies.

Multifocal motor neuropathy in Austria: a nationwide survey of clinical features and response to treatment

BACKGROUND AND OBJECTIVES

Multifocal motor neuropathy (MMN) is a rare neuropathy and detailed descriptions of larger patient cohorts are scarce. The objective of this study was to evaluate epidemiological, clinical, and laboratory features of MMN patients and their response to treatment in Austria and to compare these data with those from the literature.

METHODS

Anonymized demographic and clinical data about MMN patients until 31.12.2017 were collected from registered Austrian neurologists. Exploratory statistics on clinical and laboratory features as well as treatment regimens and responses were performed.

RESULTS

57 Patients with MMN were identified, resulting in a prevalence of 0.65/100.000. Mean age of onset was 44.1 ± 13.1 years, the diagnostic delay 5.5 ± 8.4 years. In 77% of patients, symptom onset was in the upper limbs, and in 92%, it occurred in distal muscles. Proximal onset was never observed in the lower limbs. At the final follow-up, the majority of patients had atrophy (88%) in affected regions. Definite motor conduction blocks (CB) were found in 54 patients. Anti-GM1-IgM antibodies were present in 43%. Treatment with intravenous immunoglobulins improved muscle strength and INCAT score initially, but at last follow-up, both scores deteriorated to values before treatment.

DISCUSSION

The findings of the present study corroborate the previous findings in MMN. Onset typically occurs in the upper limbs and mostly distal, CBs are found in the majority of cases, while anti-GM1-IgM antibodies are detected in only approximately 40%. Our study underlines that the initial good response to treatment fades over time.

Epidemiology of amyotrophic lateral sclerosis and effect of riluzole on disease course

OBJECTIVES

To assess the epidemiology of ALS in Austria and to evaluate the long-term effect of riluzole treatment on survival.

METHODS

Hospital discharge and riluzole prescription databases were used to identify ALS cases from January 2008 to June 2012. Using the capture-recapture method we evaluated the incidence and prevalence of ALS and patients' survival in dependence of age, gender and riluzole treatment.

RESULTS

The corrected incidence and prevalence of ALS were 3.13/100,000 person-years (95% CI, 2.77 to 3.50) and 9.14/100,000 persons (95% CI, 8.53 to 9.79), respectively. Median survival from diagnosis was 676 days (95% CI, 591 to 761). A younger age at diagnosis was associated with a longer survival. Gender did not appear to affect survival time. Riluzole therapy was associated with a survival advantage only for the initial treatment period. The adjusted hazard ratio of mortality for using riluzole increased continually over time resulting in an apparent reversal of its beneficial effect after 6 months of therapy.

CONCLUSIONS

We report incidence and prevalence estimates that are on the upper end of the wide range discussed in literature. Riluzole seems to exert a beneficial effect only in the first 6 months of therapy.

Magnetoencephalography indicates finger motor somatotopy

The existence or non-existence of fine-scale motor somatotopy of the hand is a fundamental problem with regard to the functioning of the human brain. In contrast to seldom contradicted early twentieth century descriptions of activation overlap, descriptions of finger motor somatotopy faced disagreement. Recent blood-flow-related brain mapping data achieved with functional magnetic resonance imaging (fMRI) argue in favour of fine-scale somatotopy. However, considerable discrepancies between blood oxygen-level-dependent fMRI activations and intracortically recorded neuronal activity have been reported and it is unclear whether the blood flow results truly reflect the neuronal situation. We have used recent advances in magnetoencephalography to detect signals deriving directly from neuronal tissue. Besides replication of the overlap aspect, we found statistically significant evidence for the existence of a somatotopic aspect of human hand motor representation when comparing the fifth and first finger motor dipoles along the superior-inferior axis. The average location of the fifth finger was found to be 2.31 mm superior to the first finger.

Dissociation of supplementary motor area and primary motor cortex in human subjects when comparing index and little finger movements with functional magnetic resonance imaging

This study provides the first investigation of supplementary motor area (SMA) and primary motor cortex (MI) activation with similar movements differing only in subjective difficulty of motor control. Brain activation with simple tapping of the right index finger (well trained during daily life and easy to perform) was compared with tapping of the little finger (less trained and difficult to perform) using functional magnetic resonance imaging at 3 Tesla. Due to optimised movement standardisation, extrinsic influences on activation levels such as movement complexity, amplitude and frequency were minimised. Fifth finger tapping significantly increased the number of activated SMA voxels by 450% whereas MI activation showed no significant difference between fingers. We conclude that with similar movements the degree of subjective difficulty specifically modifies SMA but not MI activation.

Finger Somatotopy in Human Motor Cortex

Although qualitative reports about somatotopic representation of fingers in the human motor cortex exist, up to now no study could provide clear statistical evidence. The goal of the present study was to reinvestigate finger motor somatotopy by means of a thorough investigation of standardized movements of the index and little finger of the right hand. Using high resolution fMRI at 3 Tesla, blood oxygenation level-dependent (BOLD) responses in a group of 26 subjects were repeatedly measured to achieve reliable statistical results. The center of mass of all activated voxels within the primary motor cortex was calculated for each finger and each run. Results of all runs were averaged to yield an individual index and little finger representation for each subject. The mean center of mass localizations for all subjects were then submitted to a paired t test. Results show a highly significant though small scale somatotopy of fingerspecific activation patterns in the order indicated by Penfields motor homunculus. In addition, considerable overlap of finger specific BOLD responses was found. Comparing various methods of analysis, the mean center of mass distance for the two fingers was 2--3 mm with overlapping voxels included and 4--5 mm with overlapping voxels excluded. Our data may be best understood in the context of the work of Schieber (1999) who recently described overlapping somatotopic gradients in lesion studies with humans.

Quantification of fMRI artifact reduction by a novel plaster cast head holder

In light of artifact-induced high variability of activation in fMRI repeat studies, we developed and tested a clinically useful plaster cast head holder (PCH) with improved immobilization, repositioning, and comfort. With PCH, there were considerably lower levels of translational and rotational head motion components compared to head fixation with conventional restraining straps (CRS). Rotational components cannot be fully compensated by realignment and lead to "false activations." In addition, task-correlated head motion, which highly increases the risk of artifacts, was considerably reduced with PCH, especially in a motion prone subject. Compared with PCH, head motion was 133% larger with CRS in a highly cooperative subject. With a motion prone subject, head motion range was increased by 769% (PCH: 0.9 mm, CRS: 7.8 mm), which may indicate the usefulness of PCH for restless patients. In functional activation maps, PCH alone yielded fewer residual motion artifacts than CRS + image registration. Subject tolerance of the head holder during the long measurement times of up to 2.5 hr was good, and slice orientation on different days confirmed the quality of repositioning.

Improvement of presurgical patient evaluation by generation of functional magnetic resonance risk maps

Recent functional magnetic resonance imaging (FMRI) replication studies show a high variability of active voxels within subjects and across runs - a potentially harmful situation for clinical applications. We tried to reduce these uncertainties inherent in current presurgical FMRI. For this, a new high quality head fixation device was used to detect reliably activated voxels over repeated measurements. In addition high correlation thresholds were applied to define the areas with highest probability of activation. The results show a focussing of such functional high risk areas to only a few voxels which localized close to intraoperative cortical stimulation. The generation of such FMRI risk maps may improve validity of clinical localization and facilitate the development of currently missing standards for maximized but still safe tumor resection.

Supplementary motor area activation preceding voluntary movement is detectable with a whole-scalp magnetoencephalography system

Despite the fact that the knowledge about the structure and the function of the supplementary motor area (SMA) is steadily increasing, the role of the SMA in the human brain, e.g., the contribution of the SMA to the Bereitschaftspotential, still remains unclear and controversial. The goal of this study was to contribute further to this discussion by taking advantage of the increased spatial information of a whole-scalp magnetoencephalography (MEG) system enabling us to record the magnetic equivalent of the Bereitschaftspotential 1, the Bereitschaftsfeld 1 (BF 1) or readiness field 1. Five subjects performed a complex, and one subject a simple, finger-tapping task. It was possible to record the BF 1 for all subjects. The first appearance of the BF 1 was in the range of -1.9 to -1.7 s prior to movement onset, except for the subject performing the simple task (-1 s). Analysis of the development of the magnetic field distribution and the channel waveforms showed the beginning of the Bereitschaftsfeld 2 (BF 2) or readiness field 2 at about -0.5 s prior to movement onset. In the time range of BF 1, dipole source analysis localized the source in the SMA only, whereas dipole source analysis containing also the time range of BF 2 resulted in dipole models, including dipoles in the primary motor area. In summary, with a whole-head MEG system, it was possible for the first time to detect SMA activity in healthy subjects with MEG.

A marker for differentiation of capabilities for processing of musical harmonies as detected by magnetoencephalography in musicians

This investigation was designed to study the characteristics of a marker for harmonic processing and to test whether it could be used for differentiating harmonic processing capabilities. The first three chords of an ordinary musical cadenca were presented to the left ear to establish a harmonic context followed by a harmonic or non-harmonic target tone. Cadencas were presented rapidly and randomly in different keys to render the task difficult. Results showed a specific P3m (magnetic P300) effect to the non-harmonic targets which was only visible in subjects with low target recognition errors. Low resolution electro-magnetic tomography current density maps showed P3m sources in the right temporoparietal, left temporoparietal and frontocentral brain areas with right temporoparietal sources being strongest and most reliable. The results offer new possibilities to selectively study harmonic variables in music processing.

Magnetoencephalography may help to improve functional MRI brain mapping

The validity of functional magnetic resonance imaging (FMRI) brain maps with respect to the sites of neuronal activation is still unknown. One source of localization error may be pixels with large signal amplitudes, since such pixels may be expected to overlie large vessels, running remote from the centre of neuronal activation. In this study, magnetoencephalography was used to determine the centre of neuronal activation in a simple finger tapping task. The localization accuracy of conventional FMRI depending on FMRI signal enhancement was investigated relative to the magnetoencephalography reference. The results show a deterioration of FMRI localization with increasing signal amplitude related to increased contributions from large vessels. We conclude that FMRI data analysis should exclude large signal amplitudes and that magnetoencephalography may help to improve FMRI brain mapping results in a multimethod approach.

Comparing localization of conventional functional magnetic resonance imaging and magnetoencephalography

The technique of functional magnetic resonance imaging (FMRI) allows the measurement of functional cerebral blood flow changes occurring with specific tasks. However, the spatial relationship between neuronal activity and functional cerebral blood flow changes is not known yet. This study compares the centre of neuronal activation (measured by magnetoencephalography) with that of the blood flow response (measured by FMRI) to unilateral motor stimulation in eight subjects. The results show a mean localization difference of 1.6 cm and demand application of methodological improvements as recently suggested.

[Correlation of results of localization by functional magnetic resonance tomography with magnetoencephalography]

Functional magnetic resonance imaging (FMRI) allows the measurement of functional cerebral blood flow changes occurring with specific tasks. However, the spatial relationship between neuronal activity and functional cerebral blood flow changes is not yet known. This study compares the center of neuronal activation (measured by magnetoencephalography) with that of the blood-flow response (measured by FMRI) to unilateral motor stimulation in eight subjects. The results show a mean localization difference of 1.6 cm and demand application of methodological improvements as recently suggested.