Upper and lower limb tremor in Charcot-Marie-Tooth neuropathy type 1A and the implications for standing balance

BACKGROUND

Neuropathic tremor occurs in Charcot-Marie-Tooth neuropathy type 1A (CMT1A; hereditary motor and sensory neuropathy, HMSN), although the pathophysiological mechanisms remain to be elucidated. Separately, lower limb tremor has not been explored in CMT1A and could be associated with imbalance as in other neuropathies. The present study aimed to determine tremor characteristics in the upper and lower limbs in CMT1A and relate these findings to clinical disability, particularly imbalance.

METHODS

Tremor and posturography studies were undertaken in phenotyped and genotyped CMT1A patients. Participants underwent detailed clinical assessment, tremor study recordings, and nerve conduction studies. Tremor stability index was calculated for upper limb tremor and compared to essential tremor.

RESULTS

Seventeen patients were enrolled. Postural and kinetic upper limb tremors were evident in 65%, while postural and orthostatic lower limb tremors were seen in 35% of CMT1A patients. Peak upper limb frequencies were lower distally (~ 6 Hz) and higher proximally (~ 9 Hz), were unchanged by weight-loading, and not impacted by fatigue. The tremor stability index was significantly higher in CMT1A than in essential tremor. A 5-6 Hz lower limb tremor was recorded which did not vary along the limb and was unaffected by fatigue. Balance was impaired in patients with postural lower limb tremor. A high frequency peak on posturography was associated with 'good' balance.

CONCLUSIONS

Tremor is a common clinical feature in CMT1A, distinct from essential tremor, mediated by a complex interaction between peripheral and central mechanisms. Postural lower limb tremor is associated with imbalance; strategies aimed at tremor modulation could be of therapeutic utility.

Longitudinal enlargement of choroid plexus is associated with chronic lesion expansion and neurodegeneration in RRMS patients

BACKGROUND AND OBJECTIVE

We explored dynamic changes in the choroid plexus (CP) in patients with relapsing-remitting multiple sclerosis (RRMS) and assessed its relationship with chronic lesion expansion and atrophy in various brain compartments.

METHODS

Fifty-seven RRMS patients were annually assessed for a minimum of 48 months with 3D FLAIR, pre- and post-contrast 3D T1 and diffusion-weighted magnetic resonance imaging (MRI). The CP was manually segmented at baseline and last follow-up.

RESULTS

The volume of CP significantly increased by 1.4% annually. However, the extent of CP enlargement varied considerably among individuals (ranging from -3.6 to 150.8 mm3 or -0.2% to 6.3%). The magnitude of CP enlargement significantly correlated with central (r = 0.70, p < 0.001) and total brain atrophy (r = -0.57, p < 0.001), white (r = -0.61, p < 0.001) and deep grey matter atrophy (r = -0.60, p < 0.001). Progressive CP enlargement was significantly associated with the volume and extent of chronic lesion expansion (r = 0.60, p < 0.001), but not with the number or volume of new lesions.

CONCLUSION

This study provides evidence of progressive CP enlargement in patients with RRMS. Our findings also demonstrate that enlargement of the CP volume is linked to the expansion of chronic lesions and neurodegeneration of periventricular white and grey matter in RRMS patients.

Upper and lower limb tremor in inflammatory neuropathies

OBJECTIVE

The mechanisms underlying neuropathic tremor remain incompletely understood and a distinction has not been drawn between proximal and distal neuropathies. Lower limb tremor contributes to imbalance in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), but this is unexplored in other neuropathies. We characterized upper and lower limb tremor in chronic immune sensory polyradiculopathy (CISP) and distal acquired demyelinating neuropathy with anti-MAG antibodies (DADS-MAG), contrasted to CIDP.

METHODS

This was a cross-sectional study of 38 patients (CIDP [n = 25], CISP [n = 7], DADS-MAG [n = 6]). Clinical assessment, tremor study recordings, nerve conduction studies, and somatosensory evoked potentials were performed. Balance was measured by force platform.

RESULTS

Upper limb tremor was prevalent (CIDP 66%, CISP 70%, DADS-MAG 100%). Peak frequencies followed a gradient along the upper limb, unchanged by weight-loading. Lower limb tremor was also present (CIDP 32%, CISP 29%, DADS-MAG 66%) and associated with imbalance. Nerve conduction parameters correlated with upper limb tremor in DADS-MAG and CISP, and imbalance in CISP.

CONCLUSIONS

Upper limb tremor is mediated by peripheral and central mechanisms regardless of distal or proximal pathology. Lower limb tremor correlates with peripheral nerve function and contributes to imbalance.

SIGNIFICANCE

This study contributes to the understanding of neuropathic tremor. Addressing lower limb tremor may be of therapeutic importance for neuropathy-associated imbalance.

Imbalance and lower limb tremor in chronic inflammatory demyelinating polyradiculoneuropathy

BACKGROUND AND AIMS

Imbalance is a prominent symptom of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Although upper limb tremor in CIDP is described, lower limb tremor has not been assessed. The aim of this study was to determine whether lower limb tremor was present in CIDP and assess potential relationships with imbalance.

METHODS

This was a cross-sectional observational study of prospectively recruited consecutive patients with typical CIDP (N = 25). Clinical phenotyping, lower limb nerve conduction and tremor studies, and posturography analyses were performed. The Berg Balance Scale (BBS) divided CIDP patients into those with "good" and "poor" balance.

RESULTS

Lower limb tremor was evident in 32% of CIDP patients and associated with poor balance (BBSTremor 35 [23-46], BBSNo Tremor 52 [44-55], p = .035). Tremor frequency was 10.2-12.5 Hz with legs outstretched and on standing, apart from four patients with a lower frequency tremor (3.8-4.6 Hz) while standing. Posturography analysis revealed a high-frequency spectral peak in the vertical axis in 44% of CIDP patients (16.0 ± 0.4 Hz). This was more likely in those with "good" balance (40% vs. 4%, p = .013).

INTERPRETATION

Lower limb tremor is present in one third of CIDP patients and is associated with poor balance. A high-frequency peak on posturography is associated with better balance in CIDP. Lower limb tremor and posturography assessments could serve as important biomarkers of balance in a clinical setting.

Chronic inflammatory demyelinating polyradiculoneuropathy-associated tremor: Phenotype and pathogenesis

BACKGROUND AND PURPOSE

Tremor in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is underrecognized, and the pathophysiology remains incompletely understood. This study evaluated tremor in CIDP and tested the hypothesis, established in other demyelinating neuropathies, that tremor occurs due to mistimed peripheral inputs affecting central motor processing. Additionally, the tremor stability index (TSI) was calculated with the hypothesis that CIDP-related tremor is more variable than other tremor disorders.

METHODS

Consecutive patients with typical CIDP were prospectively recruited from neuromuscular clinics. Alternative causes of neuropathy and tremor were excluded. Cross-sectional clinical assessment and extensive tremor study recordings were undertaken. Pearson correlation coefficient was used to compare nerve conduction studies and tremor characteristics, and t-test was used for comparisons between groups.

RESULTS

Twenty-four patients with CIDP were included. Upper limb postural and action tremor was present in 66% and was mild according to the Essential Tremor Rating Assessment Scale. Tremor did not significantly impact disability. Surface electromyography (EMG) found high-frequency spectral peaks in deltoid (13.73 ± 0.66 Hz), biceps brachii (11.82 ± 0.91 Hz), and extensor carpi radialis (11.87 ± 0.91 Hz) muscles, with lower peaks in abductor pollicis brevis EMG (6.07 ± 0.45 Hz) and index finger accelerometry (6.53 ± 0.42 Hz). Tremor was unchanged by weight loading but correlated with ulnar nerve F-wave latency and median nerve sensory amplitude. TSI (2.3 ± 0.1) was significantly higher than essential tremor.

CONCLUSIONS

Postural tremor is a common feature in CIDP. Tremor was unaffected by weight loading, typical of centrally generated tremors, although there was a correlation with peripheral nerve abnormalities. The high beat-to-beat variability on TSI and gradation of peak frequencies further suggest a complex pathophysiology. These findings may assist clinicians with the diagnosis of neuropathic tremor.

Choroid plexus volume is enlarged in clinically isolated syndrome patients with optic neuritis

OBJECTIVES

We investigated choroid plexus (CP) volume in patients presenting with optic neuritis (ON) as a clinically isolated syndrome (CIS), compared to a cohort with established relapsing-remitting multiple sclerosis (RRMS) and healthy controls (HCs).

METHODS

Three-dimensional (3D) T1, T2-FLAIR and diffusion-weighted sequences were acquired from 44 ON CIS patients at baseline, 1, 3, 6 and 12 months after the onset of ON. Fifty RRMS patients and 50 HCs were also included for comparison.

RESULTS

CP volumes was larger in both ON CIS and RRMS groups compared to HCs, but not significantly different between ON CIS and RRMS patients (analysis of covariance (ANCOVA) adjusted for multiple comparisons). Twenty-three ON CIS patients who converted to clinically definite MS (MS) demonstrated CP volume similar to RRMS patients, but significantly larger compared to HCs. In this sub-group, CP volume was not associated with the severity of optic nerve inflammation or long-term axonal loss, not with brain lesion load. A transient increase of CP volume was observed following an occurrence of new MS lesions on brain magnetic resonance imaging (MRI).

INTERPRETATION

Enlarged CP can be observed very early in a disease. It transiently reacts to acute inflammation, but not associated with the degree of tissue destruction.

Progressive Camptocormia With Head Drop and Dysphagia

A 72-year-old man had mild proximal weakness that developed into progressive camptocormia, head drop, numbness, and significant muscle wasting. What is your diagnosis?

Effect of teriflunomide on Epstein-Barr virus shedding in relapsing-remitting multiple sclerosis patients: Outcomes from a real-world pilot cohort study

BACKGROUND

Given its potential antiviral activity, we investigated the effect of teriflunomide on EBV in patients with relapsing-remitting MS (RRMS).

METHODS

Saliva samples were collected at home and analysed for EBV DNA presence in patients with RRMS treated with teriflunomide for ≥3 months.

RESULTS

The proportion of patients with detectable EBV in the teriflunomide cohort was lower than in the reference cohorts. The proportion of samples with EBV DNA or shedding from teriflunomide-treated patients was reduced relative to each reference cohort (P<0.0001; >5.8 virus copies/µL cut-off).

CONCLUSION

This pilot study demonstrated the feasibility of at-home saliva sample collection and revealed a possible effect of teriflunomide on EBV shedding.

Choroid plexus volume in multiple sclerosis predicts expansion of chronic lesions and brain atrophy

Objectives

Recent studies suggested that the expansion of long‐standing multiple sclerosis (MS) lesions and an enlargement of choroid plexus may be linked to chronic inflammation and microglial activation. We investigated the potential association between plexus volume and subsequent lesion expansion in patients with relapsing‐remitting MS.

Methods

Pre‐ and post‐gadolinium 3D‐T1, 3D FLAIR and diffusion tensor images were acquired from 49 patients. Choroid plexus (CP) volume (normalised by Total Intracranial Volume, TIV) and lesion activity were analysed between baseline and 48 months. In addition, plexus volume was measured in 40 healthy controls of similar age and gender.

Results

Baseline CP/TIV ratio was significantly larger in RRMS patients compared to normal controls (p < 0.001). CP/TIV ratio remained stable in RRMS patients during follow‐up period. There was a strong correlation between baseline CP/TIV ratio and subsequent rate of chronic lesion expansion (p < 0.001), which was stronger in close proximity to CSF. A cut‐off of 98 × 10⁻⁵ CP/TIV ratio predicted future lesion expansion with a sensitivity of 85% and specificity of 76%. CP/TIV ratio larger than a cut‐off was associated with >8‐fold increased risk of chronic lesion expansion. Baseline CP/TIV ratio was also associated with change in Mean Diffusivity (MD) inside of chronic lesions. Furthermore, baseline CP/TIV ratio significantly correlated with central brain atrophy. There was, however, no correlation between CP/TIV ratio and volume of new lesions.

Interpretation

Our data demonstrate that baseline CP/TIV ratio predicts subsequent expansion of chronic periventricular MS lesions and associated tissue damage within and outside of chronic lesions.

Long-term Effect of Permanent Demyelination on Axonal Survival in Multiple Sclerosis

Background and Objectives

To investigate the long-term effect of permanent demyelination on axonal attrition by examining an association between intereye asymmetry of the multifocal visual evoked potential (mfVEP) latency delay and subsequent thinning of retinal ganglion cell axons in patients with a long-standing history of unilateral optic neuritis (ON).

Methods

Only patients with a significant degree of chronic demyelination (intereye latency asymmetry >5 ms) were included in this study. The level of optic nerve demyelination was estimated at baseline by the latency delay of mfVEP, while the degree of axonal loss was assessed by thinning of the retinal nerve fiber layer (RNFL) thickness between baseline and follow-up visits. Low-contrast visual acuity (LCVA) was also evaluated at baseline and follow-up. Patients were examined twice with an average interval of 6.1 ± 1.4 years.

Results

From 85 examined patients with multiple sclerosis, 28 satisfied inclusion criteria. Latency of the mfVEP was delayed, and RNFL thickness was reduced in ON eyes compared with fellow eyes at both visits. There was significant correlation between latency asymmetry and baseline or follow-up intereye RNFL thickness asymmetry. Intereye asymmetry of LCVA at baseline correlated with baseline latency asymmetry of mfVEP and baseline asymmetry of RNFL thickness. Latency of the mfVEP in ON eyes improved slightly during the follow-up period, whereas latency of the fellow eye remained stable. By contrast, RNFL thickness significantly declined in both ON and fellow eyes during the follow-up period. The rate of RNFL thinning in ON eyes, however, was more than 2 times faster compared with the fellow eyes (p < 0.001). Furthermore, baseline latency asymmetry significantly correlated with the rate of RNFL thinning in ON eyes during the follow-up (p < 0.001), explaining almost half of the variability of temporal RNFL progression. For each millisecond of latency delay (i.e., ∼0.5 mm of demyelination along the optic nerve), temporal RNFL thickness was annually reduced by 0.05%.

Discussion

Our study provides clear in vivo evidence that chronic demyelination significantly accelerates axonal loss. However, because this process is slow and its effect is mild, long-term monitoring is required to establish and confidently measure the neurodegenerative consequences of demyelination.

Structural and functional markers of optic nerve damage in myelin oligodendrocyte glycoprotein antibody-associated optic neuritis

Background

Optic neuritis (ON) occurs in immune-mediated disorders including multiple sclerosis (MS), aquaporin-4 antibody-positive (AQP4) neuromyelitis optica spectrum disorder (AQP4-NMOSD) and myelin oligodendrocyte glycoprotein (MOG) antibody-associated demyelination (MOGAD). Accurate determination of aetiology is critical for appropriate treatment and prognostication.

Objective

To evaluate demyelination and axonal loss in MOG-ON to facilitate differentiation from MS-ON and AQP4-ON.

Methods

15 MOGAD patients with previous ON (25 eyes) underwent multifocal visual evoked potential (mfVEP) recordings and optical coherence tomography scans. Comparison was made to previously reported MS patients (n = 67, 69 eyes) and AQP4-NMOSD patients (n = 15, 23 eyes) with prior ON and healthy controls (n = 37, 74 eyes).

Results

MOG-ON patients had less retinal nerve fibre layer (RNFL) loss than AQP4-ON patients (p < 0.05) and less mfVEP latency prolongation than MS-ON patients (p < 0.01). Number of ON episodes in MOGAD was associated with reduced RNFL thickness (global, p = 0.07; temporal, p < 0.001) and mfVEP amplitude (p < 0.001). There was no abnormality in non-ON eyes.

Conclusions

Our study demonstrated a distinct pattern of damage in MOG-ON compared to AQP4-ON and MS-ON. ON in MOGAD produces less axonal loss than AQP4-NMOSD. Damage accumulates with relapses, supporting the role of maintenance immunosuppression to induce remission. Compared to MS, MOGAD causes less demyelination.

Posturography as a biomarker of intravenous immunoglobulin efficacy in chronic inflammatory demyelinating polyradiculoneuropathy

INTRODUCTION/AIMS

Imbalance is a common feature of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Intravenous immunoglobulin (IVIg) exerts clinical benefit in CIDP, including improving balance, although objective markers of efficacy are lacking. Posturography is an established objective marker of balance; therefore, this study aimed to determine the utility of posturography as an objective marker of treatment efficacy in CIDP.

METHODS

Posturography was performed on 18 CIDP patients, established on IVIg infusions, and results were compared to age-matched healthy controls. CIDP patients were assessed just prior to IVIg infusion and at the mid-point of the cycle. Center of pressure (CoP) was measured and the total path traveled by CoP (Sway Path, SP) was calculated for five different conditions: feet placed in parallel 16 cm apart at the medial border with eyes open (16cmEO) and eyes closed (16cmEC); medial borders of the feet touching with eyes open (0cmEO) and eyes closed (0cmEC); and tandem stance.

RESULTS

The sway path (SP) was significantly increased in CIDP patients (mean SP 1191 ± 104 mm) when compared to healthy controls (mean SP 724 ± 26 mm, P < .001). The increase was most prominent during eyes closed and tandem stance conditions. Treatment with IVIg significantly reduced SP when assessing 0cmEC (1759 ± 324 mm vs. 1081 ± 134 mm, P = .019) and tandem stance (1775 ± 290 mm vs. 1152 ± 113 mm, P = .027).

DISCUSSION

Posturography detected significant improvements in balance following IVIg in CIDP patients established on maintenance therapy. As such, posturography may be considered an objective marker of treatment response in clinical management and therapeutic trials.

Expansion of chronic MS lesions is associated with an increase of radial diffusivity in periplaque white matter

BACKGROUND

Expansion of chronic multiple sclerosis (MS) lesion is associated with slow-burning inflammation at lesion rim. However, the underlying mechanisms leading to expansion are not fully understood.

OBJECTIVE

To investigate the relationship between diffusivity markers of demyelination and axonal loss in perilesional white matter and lesion expansion in relapsing-remitting MS (RRMS).

METHODS

T1, FLAIR and diffusion tensor images were acquired from 30 patients. Novel single-streamline technique was used to estimate diffusivity in lesions, perilesional white matter and normal-appearing white matter (NAWM).

RESULTS

Significant association was found between baseline periplaque radial diffusivity (RD) and subsequent lesion expansion. Conversely, periplaque axial diffusivity (AD) did not correlate with lesion growth. Baseline RD (but not AD) in periplaque white matter of expanding lesions was significantly higher compared with non-expanding lesions. Correlation between increase of both RD and AD in the periplaque area during follow-up period and lesion expansion was noticeably stronger for RD. Increase of RD in periplaque area was also much higher compared to AD. There was significant increase of AD and RD in the periplaque area of expanding, but not in non-expanding, lesions.

CONCLUSION

Periplaque demyelination is likely to be an initial step in a process of lesion expansion and, as such, potentially represents a suitable target for remyelinating therapies.

Proximal Median Neuropathy Following Anterior Shoulder Dislocation: The Use of Magnetic Resonance Neurography

Proximal median nerve injury is an uncommon consequence of anterior shoulder dislocation, especially occurring in isolation of other upper limb peripheral nerve injury. We report the case of an 82-year-old woman with a median nerve injury as detected by clinical and neurophysiological examination following a fall and anterior shoulder dislocation. Magnetic resonance neurography confirmed the diagnosis, but also detected asymptomatic brachial plexus and ulnar nerve involvement. Management was non-operative and there has been some improvement over several months. Our case expands the differential diagnosis for proximal median neuropathy and discusses the utility of neurography in cases of neural injury.

Interferon-β Is Less Effective Than Other Drugs in Controlling the Rate of Retinal Ganglion Cell Loss in MS

Objective

To investigate the association between disease-modifying therapies (DMTs) and the rate of progressive retinal ganglion cell (RGC) and nerve fiber loss in MS.

Methods

One hundred five relapsing-remitting patients with MS were followed annually for a median of 4.0 years using optical coherence tomography. Twenty-five healthy subjects were also included as normal controls. The rates of global peripapillary retinal nerve fiber layer (pRNFL), temporal RNFL (tRNFL), and ganglion cell inner plexiform layer (GCIPL) thinning were analyzed according to DMT type using a linear mixed-effects model. Optic radiation lesion volume was measured on brain MRI and included as a covariate to minimize the effects of retrograde transsynaptic degeneration.

Results

The annual rates of RNFL and GCIPL thinning were higher in patients treated with “platform” therapies (interferon-β and glatiramer acetate) compared with DMTs of higher clinical efficacy (including fingolimod, dimethyl fumarate, natalizumab, alemtuzumab, rituximab, and ocrelizumab) (difference = −0.22 μm/y, p = 0.02 for pRNFL; difference = −0.34 μm/y, p = 0.009 for tRNFL; and difference = −0.16 μm/y, p = 0.005 for GCIPL). Based on an analysis of individual treatments (interferon-β, glatiramer acetate, fingolimod, and natalizumab), interferon-β was associated with inferior RGC preservation, relative to the other drugs. No effect difference was found between glatiramer acetate, fingolimod, and natalizumab.

Conclusions

Progressive loss of RGCs in patients with MS is more pronounced in patients treated with interferon-β than other DMTs. This finding may have implications for DMT selection in MS.

Classification of Evidence

This study provides Class IV evidence that for patients with MS, treatment with interferon-β compared with other DMTs leads to a more pronounced rate of retinal ganglion cell loss.

Differentiating axonal loss and demyelination in chronic MS lesions: A novel approach using single streamline diffusivity analysis

We describe a new single-streamline based approach to analyse diffusivity within chronic MS lesions. We used the proposed method to examine diffusivity profiles in 30 patients with relapsing multiple sclerosis and observed a significant increase of both RD and AD within the lesion core (0.38+/-0.09 μm²/ms and 0.30+/-0.12 μm²/ms respectively, p<0.0001 for both) that gradually and symmetrically diminished away from the lesion. T1-hypointensity derived axonal loss correlated highly with ΔAD (r = 0.82, p<0.0001), but moderately with ΔRD (r = 0.60, p<0.0001). Furthermore, the trendline of the ΔAD vs axonal loss intersected both axes at zero indicating close agreement between two measures in assessing the degree of axonal loss. Conversely, the trendline of the ΔRD function demonstrated a high positive value at the zero level of axonal loss, suggesting that even lesions with preserved axonal content exhibit a significant increase of RD. There was also a significant negative correlation between the level of preferential RD increase (ΔRD-ΔAD) in the lesion core and the degree of axonal damage (r = -0.62, p<0.001), indicating that ΔRD dominates in cases with milder axonal loss. Modelling diffusivity changes in the core of chronic MS lesions based on the direct proportionality of ΔAD with axonal loss and the proposed dual nature of ΔRD yielded results that were strikingly similar to the experimental data. Evaluation of lesions in a sizable cohort of MS patients using the proposed method supports the use of ΔAD as a marker of axonal loss; and the notion that demyelination and axonal loss independently contribute to the increase of RD in chronic MS lesions. The work highlights the importance of selecting appropriate patient cohorts for clinical trials of pro-remyelinating and neuroprotective therapeutics.

Expansion of chronic lesions is linked to disease progression in relapsing-remitting multiple sclerosis patients

BACKGROUND

Slow-burning inflammation is putatively associated with lesion expansion and leads to progressive loss of axons and disability worsening.

OBJECTIVE

To investigate the incidence and extent of chronic white matter lesion expansion in relapsing-remitting multiple sclerosis (RRMS) patients and to evaluate its relationship with biomarkers of disease progression.

METHODS

Pre- and post-gadolinium T1, fluid-attenuated inversion recovery (FLAIR) and diffusion tensor images were acquired from 33 patients. Lesional activity were analysed between baseline and 48 months using custom-designed software.

RESULTS

A total of 569 lesions were identified as chronic at baseline, of which 261 were expanding, 236 were stable and 72 were shrinking. In addition, 139 new lesions (both confluent and free-standing) were observed. Chronic lesion expansion was associated with patient's age and accounted for the bulk (67.3%) of total brain lesion volume increase, while only 32.7% was attributable to new lesion formation. Change in chronic lesion volume correlated with the rate of brain atrophy (r = -0.57, p = 0.001), change of Expanded Disability Status Scale (EDSS; r = 0.38, p = 0.03) and an increase of isotropic diffusivity inside the lesions (r = 0.75, p < 0.001).

CONCLUSION

Expansion of chronic lesions in RRMS patients is the primary determinant of increased T2 total lesion load. It significantly contributes to disease progression and partially driving axonal loss inside the lesions and brain damage outside of lesional tissue.

Chronic demyelination exacerbates neuroaxonal loss in patients with MS with unilateral optic neuritis

Objective

To examine the effect of chronic demyelination in the optic nerve of patients with MS on progressive loss of retinal ganglion cell (RGC) axons.

Methods

Progressive retinal nerve fiber layer (RNFL) loss, as measured by optical coherence tomography, was longitudinally examined in 51 patients with MS with a history of unilateral optic neuritis (ON) and 25 normal controls. Patients were examined annually with a median of 4-year follow-up. Pairwise intereye comparison was performed between ON and fellow non-ON (NON) eyes of patients with MS using the linear mixed-effects model and survival analysis. The latency asymmetry of multifocal visual evoked potential (mfVEP) was used to determine the level of demyelination in the optic nerve.

Results

Although both ON and NON eyes demonstrate significantly faster loss of RGC axons compared with normal subjects, ON eyes with severe chronic demyelination show accelerated thinning in the RNFL in the temporal sector of the optic disc (temporal RNFL [tRNFL]) compared with fellow eyes (evidenced by both the linear mixed-effects model and survival analysis). Furthermore, progressive tRNFL thinning is associated with the degree of optic nerve demyelination and reflects the topography of pathology in the optic nerve. More rapid axonal loss in ON eyes is also functionally evidenced by mfVEP amplitude reduction, which correlates with the level of optic nerve demyelination.

Conclusions

Although the effect of demyelination on axonal survival has been demonstrated in experimental studies, our results provide first clinically meaningful evidence that chronic demyelination is associated with progressive axonal loss in human MS.

Association Between BDNF Val66Met Polymorphism and Optic Neuritis Damage in Neuromyelitis Optica Spectrum Disorder

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune inflammatory disease of the central nervous system (CNS). The purpose of the study was to examine the association between the brain-derived neurotrophic factor (BDNF) Val66Met genotype and structural and functional optic nerve damage in the eyes of NMOSD patients. A total of 17 NMOSD subjects (34 eyes) were included in the study and were divided into subgroups based on optic neuritis (ON) history and BDNF Val66Met polymorphisms. The mean (range) age was 47.8 (23–78) years, and the mean (SD) disease duration was 7.4 (2–39) years. All participants had undergone optical coherence tomography (OCT) scans for global retinal nerve fiber layer (gRNFL) and ganglion cell-inner plexiform layer (GCIPL) thickness and multifocal visual evoked potential (mfVEP) test for amplitude and latency. BDNF Val66Met polymorphisms were genotyped in all participants. OCT and mfVEP changes were compared between two genotype groups (Met carriers vs. Val homozygotes) by using the generalised estimating equation (GEE) models. The BDNF Val66Met polymorphism was significantly associated with more severe nerve fiber layer damage and axonal loss in ON eyes of NMOSD subjects. Met carriers had more significantly reduced GCIPL (P = 0.002) and gRNFL (P < 0.001) thickness as well as more delayed mfVEP latency (P = 0.008) in ON eyes. No association was found between Val66Met variants and non-ON (NON)-eye of the participants. These findings suggest that the BDNF Val66Met polymorphism may be associated with optic nerve damage caused by acute ON attacks in NMOSD patients.

Whole genome sequencing for the genetic diagnosis of heterogenous dystonia phenotypes

INTRODUCTION

Dystonia is a clinically and genetically heterogeneous disorder and a genetic cause is often difficult to elucidate. This is the first study to use whole genome sequencing (WGS) to investigate dystonia in a large sample of affected individuals.

METHODS

WGS was performed on 111 probands with heterogenous dystonia phenotypes. We performed analysis for coding and non-coding variants, copy number variants (CNVs), and structural variants (SVs). We assessed for an association between dystonia and 10 known dystonia risk variants.

RESULTS

A genetic diagnosis was obtained for 11.7% (13/111) of individuals. We found that a genetic diagnosis was more likely in those with an earlier age at onset, younger age at testing, and a combined dystonia phenotype. We identified pathogenic/likely-pathogenic variants in ADCY5 (n = 1), ATM (n = 1), GNAL (n = 2), GLB1 (n = 1), KMT2B (n = 2), PRKN (n = 2), PRRT2 (n = 1), SGCE (n = 2), and THAP1 (n = 1). CNVs were detected in 3 individuals. We found an association between the known risk variant ARSG rs11655081 and dystonia (p = 0.003).

CONCLUSION

A genetic diagnosis was found in 11.7% of individuals with dystonia. The diagnostic yield was higher in those with an earlier age of onset, younger age at testing, and a combined dystonia phenotype. WGS may be particularly relevant for dystonia given that it allows for the detection of CNVs, which accounted for 23% of the genetically diagnosed cases.

Regional motor cortex dysfunction in amyotrophic lateral sclerosis

OBJECTIVE

The pathophysiological processes underlying amyotrophic lateral sclerosis (ALS) need to be better understood, although cortical dysfunction has been implicated. Previous transcranial magnetic stimulation (TMS) studies have assessed cortical dysfunction from the hand. The aim of the present study was to determine whether cortical dysfunction was evident across representations of three body regions, and to relate these changes to clinical features of ALS.

METHODS

In this cross-sectional study, threshold tracking TMS was undertaken in 60 sporadic ALS patients, with motor evoked potential (MEP) responses recorded over the hand (abductor pollicis brevis), lower limb (tibialis anterior), and bulbar (trapezius) regions. The cross-sectional findings were compared to 28 age- and gender-matched controls.

RESULTS

Cortical dysfunction was evident across the representation of the three body regions, although the degree and nature of the dysfunction varied. Cortical hyperexcitability, as heralded by reduced short interval intracortical inhibition (SICI), was evident in all cortical regions (hand, P < 0.01; leg, P < 0.05; bulbar, P < 0.05) in ALS patients when compared with healthy control subjects. Importantly, features of cortical hyperexcitability seemed more prominent in clinically affected body regions and correlated with functional disability and muscle weakness. Cortical inexcitability was more prominent in the leg (P < 0.001) and bulbar regions (P < 0.01) when compared with controls.

INTERPRETATION

The nature of cortical dysfunction varied across the body regions in ALS, with cortical hyperexcitability being more prominent in the upper limbs while cortical inexcitability was more evident in the lower limbs and bulbar regions. The findings suggest a heterogeneity of cortical pathophysiological processes in ALS.

Lesion activity and chronic demyelination are the major determinants of brain atrophy in MS

Objective

To evaluate the combined effect of lesion activity and pathologic processes occurring in both chronically demyelinated lesions and normal-appearing white matter (NAWM) on brain atrophy in MS.

Methods

Pre- and post-gadolinium T1, fluid attenuation inversion recovery, and diffusion tensor imaging images were acquired from 50 consecutive patients with relapsing-remitting MS (all, but one, on disease-modifying therapy) at baseline and 5 years. Brain atrophy was measured using structural image evaluation, using normalization of atrophy percent brain volume change (PBVC) analysis.

Results

During follow-up, brain volume diminished by 2.0% ± 1.1%. PBVC was not associated with patient age, disease duration, sex, or type of treatment. PBVC moderately correlated with baseline lesion load (r = −0.38, p = 0.016), but demonstrated strong association with new lesion activity (r = −0.63, p < 0.001). Brain atrophy was also strongly linked to the increase of water diffusion within chronic MS lesions (r = −0.62, p < 0.001). In normal-appearing white matter (NAWM), PBVC demonstrated a significant correlation with both baseline and longitudinal increase of demyelination as measured by radial diffusivity (RD, r = −0.44, p = 0.005 and r = −0.35, p = 0.026, respectively). Linear regression analysis explained 62% of the variance in PBVC. It confirmed the major role of new lesion activity (p = 0.002, standardized beta-coefficient −0.42), whereas change in diffusivity inside chronic lesions and NAWM RD at baseline also contributed significantly (p = 0.04 and 0.02, standardized beta-coefficient −0.31 and −0.29, respectively), increasing predictive power of the model by 55%.

Conclusion

In addition to new lesion activity, progressive loss of demyelinated axons in chronic lesions and the degree of demyelination in NAWM significantly contribute to accelerated loss of brain tissue in patients with MS receiving immunomodulatory therapy.

Conduction block in immune-mediated neuropathy: paranodopathy versus axonopathy

BACKGROUND AND PURPOSE

Conduction block is a pathognomonic feature of immune-mediated neuropathies. The aim of this study was to advance understanding of pathophysiology and conduction block in chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN).

METHODS

A multimodal approach was used, incorporating clinical phenotyping, neurophysiology, immunohistochemistry and structural assessments.

RESULTS

Of 49 CIDP and 14 MMN patients, 25% and 79% had median nerve forearm block, respectively. Clinical scores were similar in CIDP patients with and without block. CIDP patients with median nerve block demonstrated markedly elevated thresholds and greater threshold changes in threshold electrotonus, whilst those without did not differ from healthy controls in electrotonus parameters. In contrast, MMN patients exhibited marked increases in superexcitability. Nerve size was similar in both CIDP groups at the site of axonal excitability. However, CIDP patients with block demonstrated more frequent paranodal serum binding to teased rat nerve fibres. In keeping with these findings, mathematical modelling of nerve excitability recordings in CIDP patients with block support the role of paranodal dysfunction and enhanced leakage of current between the node and internode. In contrast, changes in MMN probably resulted from a reduction in ion channel density along axons.

CONCLUSIONS

The underlying pathologies in CIDP and MMN are distinct. Conduction block in CIDP is associated with paranodal dysfunction which may be antibody-mediated in a subset of patients. In contrast, MMN is characterized by channel dysfunction downstream from the site of block.

Hereditary sensory and autonomic neuropathy type IC accompanied by upper motor neuron abnormalities and type II juxtafoveal retinal telangiectasias

Hereditary sensory and autonomic neuropathy type I (HSAN-1) is an autosomal dominant sensory neuropathy occurring secondary to mutations in the SPTLC1 and SPTLC2 genes. We present two generations of a single family with Ser384Phe mutation in the SPTLC2 gene located on chromosome 14q24 characterized by a typical HSAN-1c presentation, with additional findings upper motor neuron signs, early demyelinating features on nerve conduction studies, and type II juxtafoveal retinal telangiectasias also known as macular telangiectasias (MacTel II). Although HSAN1 is characterized as an axonal neuropathy, demyelinating features were identified in two subjects on serial nerve conduction studies comprising motor conduction block, temporal dispersion, and prolongation of F-waves. MacTell II is a rare syndrome characterized by bilateral macular depigmentation and Müller cell loss. It has a presumed genetic basis, and these cases suggest that the accumulation of toxic sphingoplipids may lead to Müller cell degeneration, subsequent neuronal loss, depigmentation, and progressive central macular thinning.

Evidence of Müller Glial Dysfunction in Patients with Aquaporin-4 Immunoglobulin G-Positive Neuromyelitis Optica Spectrum Disorder

PURPOSE

To compare functional and structural changes in the retina in patients with aquaporin-4 immunoglobulin G (AQP4-IgG)-positive neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS).

DESIGN

Cross-sectional study; biochemical study of human retinas.

PARTICIPANTS

A total of 181 participants, including 22 consecutive patients (44 eyes) with NMOSD, 131 patients (262 eyes) with multiple sclerosis (MS), and 28 normal subjects (56 eyes). In addition, 8 eyeballs from healthy donors were used for biochemical analysis.

METHODS

Full-field electroretinography (ERG) and spectral-domain OCT were performed in all the subjects. Topography of AQP4 expression and Müller glial distribution were analyzed using Western blotting and immunohistochemistry.

MAIN OUTCOME MEASURES

Full-field ERG parameters, including amplitudes and peak times. Tissue volume of each of the retinal layers at the fovea by OCT segmentation. Levels of AQP4 expression at different retinal regions.

RESULTS

The b-wave amplitude was significantly reduced in patients with AQP4-IgG+ NMOSD in scotopic ERGs (compared with AQP4-IgG- subjects, patients with MS, and normal controls) but not in photopic ERGs. Further analysis showed that this b-wave change was mainly caused by reduction of the slow PII component, suggesting specific Müller cell dysfunction. We also found thinning of specific retinal layers at the fovea in patients with AQP4-IgG+ NMOSD, in the Henle fiber outer nuclear layer (HFONL) and the inner segment (IS) layer, but not in the inner nuclear layer (INL), outer plexiform layer (OPL), or outer segment (OS) layer. Furthermore, there was a significant association between foveal HFONL-IS complex thinning and scotopic b-wave amplitude reduction (P = 0.005∼0.01, fixed-effects model). Western blotting demonstrated that Müller cell-specific AQP4 was expressed at a higher level at the fovea than the peripheral retina. Immunohistochemical studies revealed that the specific foveal thinning reflected the topography of AQP4 expression and Müller glial distribution in the human macula.

CONCLUSIONS

This study provides in vivo structural and functional evidence of Müller glial dysfunction in eyes of patients with AQP4-IgG+ NMOSD. Topography of retinal structural change is supported by distribution of Müller cells and patterns of AQP4 expression. The study suggests that visual electrophysiology and retinal imaging could be useful biomarkers to assess the potential retinal astrocytopathy in NMOSD.

A case of autoimmune myositis after treatment with alemtuzumab for multiple sclerosis

Alemtuzumab is a high-efficacy disease-modifying therapy for the treatment of relapsing forms of multiple sclerosis and is associated with secondary autoimmune adverse events. We report a novel case of secondary autoimmune myositis that occurred seven months after the initial treatment cycle and achieved full recovery with oral corticosteroids. This particular form of myositis appears to be unique, and is likely to be a distinct entity from the other four types of immune-mediated myositis.

Pathophysiological basis of low contrast visual acuity loss in multiple sclerosis

Objective

There is currently an urgent need for reliable clinical biomarkers of remyelination to be used in Phase 2 and Phase 3 clinical trials. Low contrast visual acuity (LCVA) has been suggested as a functional measure of the integrity of the visual pathway. Therefore, the aim of this study was to elucidate the potential contribution of axonal loss and demyelination to LCVA loss in MS patients.

Method

In this study, 50 consecutive relapsing remitting MS patients with a previous history of unilateral optic neuritis were enrolled. Using the linear regression model, we assessed the relative contribution of multifocal Visual Evoked Potentials (mfVEP) latency and Retinal Nerve Fiber Layer (RNFL) thickness to LCVA deficit.

Results

Intereye asymmetry of mfVEP latency and RNFL thickness correlated significantly with intereye asymmetry of LCVA (P < 0.001). A linear regression model demonstrated increased predictive power of LCVA when mfVEP latency and RNFL thinning were combined (reaching R ² = 0.67) and confirmed a higher predictive value of RNFL thinning compared to mfVEP latency delay for both contrast levels. However, elimination of subjects with severe axonal loss dramatically increased the relative contribution of mfVEP latency, with contribution of RNFL thickness losing significance for both 1.25% and 2.5% LCVA.

Interpretation

While retinal ganglion cell axonal loss is a superior predictor of LCVA, the degree of demyelination contributes significantly to worsening of LCVA, particularly when patients with severe axonal loss are excluded. These results support the feasibility of using LCVA as a functional biomarker in remyelination therapy trials, providing appropriate patient's selection criteria are implemented.

Comparison of cross-sectional areas and distal-proximal nerve ratios in amyotrophic lateral sclerosis

INTRODUCTION

This study explored potential diagnostic markers of nerve ultrasound in differentiating amyotrophic lateral sclerosis (ALS) from mimic disorders.

METHODS

Ultrasound of the median, ulnar, and tibial nerves was conducted in 53 patients with ALS, 32 patients with ALS-mimic disorders, and 30 controls. Nerve cross-sectional area (CSA) and distal-proximal ratios were calculated.

RESULTS

The median nerve CSA in the upper arm was decreased (7.9 ± 1.3 mm² vs. 9.0 ± 1.4 mm² , P < 0.05), and the median nerve wrist-upper arm ratio was increased in ALS patients compared with controls (1.3 ± 0.4 vs. 1.1 ± 0.2; P < 0.01). In differentiating ALS from mimic presentations, assessment of median nerve CSA in the upper arm and comparison of a median and ulnar nerve CSA distal-proximal ratio provide diagnostic potential.

DISCUSSION

Assessment of nerve CSA combined with calculation of nerve CSA distal-proximal ratio provides a useful marker to aid in the diagnosis of ALS. Muscle Nerve 58:777-783, 2018.

Anti-MAG neuropathy: Role of IgM antibodies, the paranodal junction and juxtaparanodal potassium channels

OBJECTIVE

To improve understanding of disease pathophysiology in anti-myelin-associated glycoprotein (anti-MAG) neuropathy to guide further treatment approaches.

METHODS

Anti-MAG neuropathy patients underwent clinical assessments, nerve conduction and excitability studies, and ultrasound assessment.

RESULTS

Patients demonstrated a distinctive axonal excitability profile characterised by a reduction in superexcitability [MAG: -14.2 ± 1.6% vs healthy controls (HC): -21.8 ± 1.2%; p < 0.01] without alterations in most other excitability parameters. Mathematical modelling of nerve excitability recordings suggested that changes in axonal function could be explained by a 72.5% increase in juxtaparanodal fast potassium channel activation and an accompanying hyperpolarization of resting membrane potential (by 0.3 mV) resulting in a 94.2% reduction in discrepancy between anti-MAG data and the healthy control model. Superexcitability changes correlated strongly with clinical and neurophysiological parameters. Furthermore, structural assessments demonstrated a proximal pattern of nerve enlargement (C6 nerve root cross-sectional area: 15.9 ± 8.1 mm² vs HC: 9.1 ± 2.3 mm²; p < 0.05).

CONCLUSIONS

The imaging and neurophysiological results support the pathogenicity of anti-MAG IgM. Widening between adjacent loops of paranodal myelin due to antibodies would expand the pathway from the node to the juxtaparanode, increasing activation of juxtaparanodal fast potassium channels, thereby impairing saltatory conduction.

SIGNIFICANCE

Potassium channel blockers may prove beneficial in restoring conduction closer to its normal state and improving nerve function in anti-MAG neuropathy.

Differing Structural and Functional Patterns of Optic Nerve Damage in Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorder

PURPOSE

To assess differential patterns of axonal loss and demyelination in the optic nerve in multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD).

DESIGN

Cross-sectional study.

PARTICIPANTS

One hundred ninety-two participants, including 136 MS patients (272 eyes), 19 NMOSD patients (38 eyes), and 37 healthy control participants (74 eyes).

METHODS

All participants underwent spectral-domain OCT scans and multifocal visual evoked potential (mfVEP) recordings. High-resolution magnetic resonance imaging (MRI) with the diffusion protocol also was performed in all patients.

MAIN OUTCOME MEASURES

Ganglion cell-inner plexiform layer (GCIPL) thickness and mfVEP amplitude and latency at 5 eccentricities; global and temporal retinal nerve fiber layer thickness.

RESULTS

In optic neuritis (ON) eyes, the NMOSD patients had more severe GCIPL loss (P < 0.001) and mfVEP amplitude reduction (P < 0.001) compared with MS patients, whereas in contrast, mfVEP latency delay was more evident in MS patients (P < 0.001). The NMOSD patients showed more morphologic and functional loss at the foveal to parafoveal region, whereas the MS patients showed evenly distributed damage at the macula. Correlation analysis demonstrated a strong structure-function (OCT-mfVEP) association in the NMOSD patients, which was only moderate in the MS patients. In non-ON (NON) eyes, the MS patients showed significantly thinner GCIPL than controls (P < 0.001), whereas no GCIPL loss was observed in NON eyes in NMOSD. In addition, a significant correlation was found between all OCT and mfVEP measures in MS patients, but not in NMOSD patients. MRI demonstrated significant lesional load in the optic radiation in MS compared to NMOSD eyes (P = 0.002), which was related to the above OCT and mfVEP changes in NON eyes.

CONCLUSIONS

Our study demonstrated different patterns of ON damage in NMOSD and MS. In MS, the ON damage was less severe, with demyelination as the main pathologic component, whereas in NMOSD, axonal loss was more severe compared with myelin loss. The disproportional mfVEP amplitude and latency changes suggested predominant axonal damage within the anterior visual pathway as the main clinical feature of NMOSD, in contrast to MS, where demyelination spreads along the entire visual pathway.

004 Mechanisms of nerve dysfunction in inflammatory neuropathies

Introduction

Immune-mediated neuropathies are a cause of disability and an immense cost to the healthcare system. They include chronic inflammatory demyelinating polyneuropathy (CIDP), multifocal motor neuropathy (MMN) and the neuropathy associated with IgM antibodies against myelin-associated glycoprotein (MAG). CIDP is extremely heterogeneous with marked variability in treatment responsiveness. Patients with MMN often respond to treatment but progressive weakness and wasting typically ensues over time. No therapy has consistently proven effective in anti-MAG neuropathy. The present series of studies were undertaken to improve understanding of disease mechanisms in these neuropathies, a critical step before targeted treatment approaches can be developed.

Methods

Patients fulfilling Peripheral Nerve Society criteria for CIDP or MMN and patients positive for anti-MAG IgM underwent comprehensive clinical assessments, neurophysiology, serological testing and structural assessments.

Results

The patient cohort consisted of 80 patients (51 CIDP, 14 MMN, 15 MAG). 6% of CIDP patients tested positive for anti-neurofascin 155 (NF155) and 4% for anti-contactin 1 IgG4. Anti-NF155 neuropathy was characterised by diffuse nerve enlargement and an axonal excitability profile consistent with severe disruption of the paranodal seal. CIDP patients testing negative for IgG4 antibodies also demonstrated significant nerve enlargement compared with healthy subjects. Axonal excitability profiles differed in those with and without median nerve conduction block. MMN was characterised by patchy nerve enlargement, marked increases in super-excitability and enlarged motor unit size. In contrast, anti-MAG neuropathy patients demonstrated a proximal pattern of nerve enlargement and an axonal excitability profile characterised by reduced super-excitability consistent with increased juxta-paranodal fast potassium channel conductance.

Conclusion

Patterns of nerve enlargement and neurophysiological profiles differ in the immune-mediated neuropathies providing insights into molecular mechanisms. These results provide templates that can guide treatment approaches. The combination of directed autoantibody assays and measures of axonal function can be used to monitor disease progression and therapeutic response.

Mechanism of delayed conduction of fellow eyes in patients with optic neuritis

To test the hypothesis that latency delay in the fellow eyes of optic neuritis (ON) patients and to compensate for delayed transmission of visual information, latency change of multi-focal visual evoked potential (mfVEP) traces in fellow eyes of 15 ON patients were analyzed. Patients with low risk (LR) for developing multiple sclerosis (MS) were examined separately from MS patients to isolate effect of cortical plasticity from potential pathological changes in disseminated disease. The small increase in latency in fellow eyes of LR group was statistically not significant. In MS patients, the latency was significantly delayed (P<0.02). The magnitude of the latency change in the fellow eyes did not correlate with the severity of latency delay in the affected eyes (R²<0.02, P=0.3). The differences between ON patients with and without MS, reported here, suggest that the presence of disseminated disease plays critical role in latency delay of the fellow eye.

Progressive inner nuclear layer dysfunction in non-optic neuritis eyes in MS

OBJECTIVE

To investigate primary retinal functional changes in non-optic neuritis (ON) eyes of patients with MS by full-field electroretinography (ERG).

METHODS

Seventy-seven patients with relapsing-remitting MS with no history of clinical ON in at least 1 eye and 30 healthy controls were recruited in the cohort study. Full-field ERGs were recorded, and retinal optical coherence tomography scans were performed to assess the thicknesses of peripapillary retinal nerve fiber layer (RNFL) and retinal ganglion cell layer-inner plexiform layer (GCL-IPL). Annual MRI scans were also carried out to evaluate the disease activity in the brain. Patients were followed up for 3 years.

RESULTS

At baseline, a delayed b-wave peak time was observed in the cone response (p < 0.001), which was associated with the thicknesses of RNFL and GCL-IPL. The peak time of the delayed b-wave also correlated with the Expanded Disability Status Scale, T2 lesion volume, and disease duration. During the 3-year follow-up, progressive ERG amplitude reduction was observed (both a- and b-waves, p < 0.05). There was a correlation between the b-wave amplitude reduction and longitudinal RNFL loss (p = 0.001). However, no correlation was found between longitudinal ERG changes and disease activity in the brain.

CONCLUSIONS

This study demonstrated progressive inner nuclear layer dysfunction in MS. The borderline a-wave changes suggested some outer retinal dysfunction as well. The correlation between full-field ERG changes and retinal ganglion cell loss suggested that there might be subclinical retinal pathology in MS affecting both outer and inner retinal layers.

Evidence of progressive tissue loss in the core of chronic MS lesions: A longitudinal DTI study

Objective

Using diffusion tensor imaging (DTI), we examined chronic stable MS lesions, peri-lesional white matter (PLWM) and normal appearing white matter (NAWM) in patients with relapsing-remitting multiple sclerosis (RRMS) for evidence of progressive tissue destruction and evaluated whether diffusivity change is associated with conventional MRI parameters and clinical findings.

Method

Pre- and post-gadolinium T1, T2 and DTI images were acquired from 55 consecutive RRMS patients at baseline and 42.3 ± 9.7 months later. Chronic stable T2 lesions of sufficient size were identified in 43 patients (total of 134 lesions). Diffusivity parameters such as axial diffusivity (AD), radial diffusivity (RD), mean diffusivity (MD) and fractional anisotropy (FA) were compared at baseline and follow-up. MRI was also performed in 20 normal subjects of similar age and gender.

Results

Within the core of chronic MS lesions the diffusion of water molecules significantly increased over the follow-up period, while in NAWM all diffusivity indices remained stable. Since increase of AD and RD in lesional core was highly concordant, indicating isotropic nature of diffusivity change, and considering potential effect of crossing fibers on directionally-selective indices, only MD, a directionally-independent measure, was used for further analysis. The significant increase of MD in the lesion core during the follow-up period (1.29 ± 0.19 μm2/ms and 1.34 ± 0.20 μm2/ms at baseline and follow-up respectively, P < 0.0001) was independent of age or disease duration, total brain lesion volume or new lesion activity, lesion size or location and baseline tissue damage (T1 hypointensity). Change of MD in the lesion core, however, was associated with progressive brain atrophy (r = 0.47, P = 0.002). A significant gender difference was also observed: the MD change in male patients was almost twice that of female patients (0.030 ± 0.04 μm2/ms and 0.058 ± 0.03 μm2/ms in female and male respectively, P = 0.01). Sub-analysis of lesions with lesion-free surrounding revealed the largest MD increase in the lesion core, while MD progression gradually declined towards PLWM. MD in NAWM remained stable over the follow-up period.

Conclusion

The significant increase of isotropic water diffusion in the core of chronic stable MS lesions likely reflects gradual, self-sustained tissue destruction in demyelinated white matter that is more aggressive in males.

Progression of retinal ganglion cell loss in multiple sclerosis is associated with new lesions in the optic radiations

BACKGROUND AND PURPOSE

The mechanism of retinal ganglion cell and retinal nerve fiber layer loss in multiple sclerosis (MS) remains unknown. This study aimed to investigate the association between temporal retinal nerve fiber layer (tRNFL) thinning and disease activity in the brain determined by T2 lesions on magnetic resonance imaging (MRI).

METHODS

Fifty-five consecutive patients with relapsing-remitting MS and 25 controls were enrolled. All patients underwent annual optical coherence tomography and high-resolution MRI scans for tRNFL thickness and brain lesion volume analysis, respectively.

RESULTS

Significant tRNFL thickness reduction was observed over the 3-year follow-up period at a relatively constant rate (1.02 μm/year). Thinning of tRNFL fibers was more prominent in younger patients (P = 0.01). The tRNFL loss was associated with new MRI lesions in the optic radiations (ORs). There was significantly greater tRNFL thinning in patients with new lesional activity in the ORs compared with patients with new lesions outside the ORs (P = 0.009).

CONCLUSIONS

This study supports the notion that retrograde transneuronal degeneration caused by OR lesions might play a role in progressive retinal nerve fiber layer loss. In addition, the results of the study also indicate that the disease-related neurodegenerative changes in the retina start much earlier than the clinical diagnosis of MS.

Differentiating lower motor neuron syndromes

Lower motor neuron (LMN) syndromes typically present with muscle wasting and weakness and may arise from pathology affecting the distal motor nerve up to the level of the anterior horn cell. A variety of hereditary causes are recognised, including spinal muscular atrophy, distal hereditary motor neuropathy and LMN variants of familial motor neuron disease. Recent genetic advances have resulted in the identification of a variety of disease-causing mutations. Immune-mediated disorders, including multifocal motor neuropathy and variants of chronic inflammatory demyelinating polyneuropathy, account for a proportion of LMN presentations and are important to recognise, as effective treatments are available. The present review will outline the spectrum of LMN syndromes that may develop in adulthood and provide a framework for the clinician assessing a patient presenting with predominantly LMN features.