Electrodiagnostic studies and new diagnostic modalities for evaluation of peripheral nerve disorders

Electrodiagnostic studies (EDx) are frequently performed in the diagnostic evaluation of peripheral nerve disorders. There is increasing interest in the use of newer, alternative diagnostic modalities, in particular imaging, either to complement or replace established EDx protocols. However, the evidence to support this approach has not been expansively reviewed. In this paper, diagnostic performance data from studies of EDx and other diagnostic modalities in common peripheral nerve disorders have been analyzed and described, with a focus on radiculopathy, plexopathy, compressive neuropathies, and the important neuropathy subtypes of Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), vasculitic neuropathy and diabetic neuropathy. Overall EDx retains its place as a primary diagnostic modality in the evaluated peripheral nerve disorders. Magnetic resonance imaging and ultrasound have developed important complementary diagnostic roles in compressive and traumatic neuropathies and atypical CIDP, but their value is more limited in other neuropathy subtypes. Identification of hourglass constriction in nerves of patients with neuralgic amyotrophy may have therapeutic implications. Investigation of radiculopathy is confounded by poor correlation between clinical features and imaging findings and the lack of a diagnostic gold standard. There is a need to enhance the literature on the utility of these newer diagnostic modalities.

Axonal excitability as an early biomarker of nerve involvement in hereditary transthyretin amyloidosis

OBJECTIVES

The treatment of hereditary transthyretin amyloidosis polyneuropathy (ATTRv-PN) has been revolutionised by genetic therapies, with dramatic improvements in patient outcomes. Whilst the optimal timing of treatment initiation remains unknown, early treatment is desirable. Consequently, the aim of the study was to develop biomarkers of early nerve dysfunction in ATTRv-PN.

METHODS

Ulnar motor and sensory axonal excitability studies were prospectively undertaken on 22 patients with pathogenic hereditary transthyretin amyloid (ATTRv) gene variants, 12 with large fibre neuropathy (LF+) and 10 without (LF-), with results compared to age- and sex-matched healthy controls.

RESULTS

In motor axons we identified a continuum of change from healthy controls, to LF- and LF+ ATTRv with progressive reduction in hyperpolarising threshold electrotonus (TEh40(10-20 ms): p = 0.04, TEh40(20-40 ms): p = 0.01 and TEh40(90-10 ms): p = 0.01), suggestive of membrane depolarisation. In sensory axons lower levels of subexcitability were observed on single (SubEx) and double pulse (SubEx2) recovery cycle testing in LF+ (SubEx: p = 0.015, SubEx2: p = 0.015, RC(2-1): p = 0.04) suggesting reduced nodal slow potassium conductance, which promotes sensory hyperexcitability, paraesthesia and pain. There were no differences in sensory or motor excitability parameters when comparing different ATTRv variants.

CONCLUSIONS

These progressive changes seen across the disease spectrum in ATTRv-PN suggest that axonal excitability has utility to identify early and progressive nerve dysfunction in ATTRv, regardless of genotype.

SIGNIFICANCE

Axonal excitability is a promising early biomarker of nerve dysfunction in ATTRv-PN.

Advances in diagnosis and management of distal sensory polyneuropathies

Distal sensory polyneuropathy (DSP) is characterised by length-dependent, sensory-predominant symptoms and signs, including potentially disabling symmetric chronic pain, tingling and poor balance. Some patients also have or develop dysautonomia or motor involvement depending on whether large myelinated or small fibres are predominantly affected. Although highly prevalent, diagnosis and management can be challenging. While classic diabetes and toxic causes are well-recognised, there are increasingly diverse associations, including with dysimmune, rheumatological and neurodegenerative conditions. Approximately half of cases are initially considered idiopathic despite thorough evaluation, but often, the causes emerge later as new symptoms develop or testing advances, for instance with genetic approaches. Improving and standardising DSP metrics, as already accomplished for motor neuropathies, would permit in-clinic longitudinal tracking of natural history and treatment responses. Standardising phenotyping could advance research and facilitate trials of potential therapies, which lag so far. This review updates on recent advances and summarises current evidence for specific treatments.

Muscle ultrasound in hereditary muscle disease

In this review we summarise the key techniques of muscle ultrasound as they apply to hereditary muscle disease. We review the diagnostic utility of muscle ultrasound including its role in guiding electromyography and muscle biopsy sampling. We summarize the different patterns of sonographic muscle involvement in the major categories of genetic muscle disorders and discuss the limitations of the technique. We hope to encourage others to adopt ultrasound in their care for patients with hereditary muscle diseases.

Neuromuscular ultrasound training courses in the post COVID-19 era: Is virtual training here to stay, and should the pre-pandemic training design be revised?

See article on pages 29–33 in this issue.

Review Article "Spotlight on Ultrasonography in the Diagnosis of Peripheral Nerve Disease: The Evidence to Date"

Neuromuscular ultrasound is rapidly becoming incorporated into clinical practice as a standard tool in the assessment of peripheral nerve diseases. Ultrasound complements clinical phenotyping and electrodiagnostic evaluation, providing critical structural anatomical information to enhance diagnosis and identify structural pathology. This review article examines the evidence supporting neuromuscular ultrasound in the diagnosis of compressive mononeuropathies, traumatic nerve injury, generalised peripheral neuropathy and motor neuron disease. Extending the sonographic evaluation of nerves beyond simple morphological measurements has the potential to improve diagnostics in peripheral neuropathy, as well as advancing the understanding of pathological mechanisms, which in turn will promote precise therapies and improve therapeutic outcomes.

Asymptomatic common extensor tendon pathology in patients with carpal tunnel syndrome

INTRODUCTION/AIMS

Carpal tunnel syndrome (CTS) and lateral epicondylitis are both highly prevalent conditions. Our objective was to determine the prevalence of B-mode ultrasound abnormalities of the common extensor tendon (CET) in patients with CTS and establish the relationship between CET stiffness, as measured by shear wave elastography (SWE) and CTS severity.

METHODS

Patients without symptoms or signs of lateral epicondylitis were recruited from referrals to a neurophysiology laboratory for possible CTS. These patients were examined for clinical features of CTS before undergoing electrodiagnostic testing followed by an ultrasound examination, consisting of B-mode, power Doppler, and SWE.

RESULTS

Thirty-nine limbs with clinically diagnosed CTS and 20 control limbs were included. Of the CTS limbs, 61.5% had sonographically abnormal CET compared with 35% of the controls. The mean CET sonographic abnormality score was higher in CTS patients compared with controls (P = .006). CTS patients with sonographically abnormal CET had more severe CTS by electrophysiological criteria. The mean CET stiffness in CTS patients was lower than in controls (P = .033).

DISCUSSION

Sonographic abnormalities of the CET are common in CTS patients with no clinical evidence of lateral epicondylitis and may relate to common pathogenetic mechanisms. These findings suggest that isolated ultrasound abnormalities in the CET are not diagnostically useful in patients presenting with upper limb pain unless there are clinical features of lateral epicondylitis.

Objectively Assessing Sports Concussion utilizing Visual Evoked Potentials

A portable system capable of measuring steady-state visual-evoked potentials (SSVEP) was developed to provide an objective, quantifiable method of electroencephalogram (EEG) testing following a traumatic event. In this study, the portable system was used on 65 healthy rugby players throughout a season to determine whether SSVEP are a reliable electrophysiological biomarker for concussion. Preceding the competition season, all players underwent a baseline SSVEP assessment. During the season, players were re-tested within 72 h of a match for either test-retest reliability or post-injury assessment. In the case of a medically diagnosed concussion, players were reassessed again once deemed recovered by a physician. The SSVEP system consisted of a smartphone housed in a VR-frame delivering a 15 Hz flicker stimulus, while a wireless EEG headset recorded occipital activity. Players were instructed to stare at the screen's fixation point while remaining seated and quiet. Electrodes were arranged according to the 10-20 EEG-positioning nomenclature, with O1-O2 being the recording channels while P1-P2 the references and bias, respectively. All EEG data was processed using a Butterworth bandpass filter, Fourier transformation, and normalization to convert data for frequency analysis. Players SSVEP responses were quantified into a signal-to-noise ratio (SNR), with 15 Hz being the desired signal, and summarized into respective study groups for comparison. Concussed players were seen to have a significantly lower SNR compared to their baseline; however, post-recovery, their SNR was not significantly different from the baseline. Test-retest indicated high device reliability for the portable system. An improved portable SSVEP system was also validated against an established EEG amplifier to ensure the investigative design is capable of obtaining research quality EEG measurements. This is the first study to identify differences in SSVEP responses in amateur athletes following a concussion and indicates the potential for SSVEP as an aid in concussion assessment and management.

Steady-State Visual-Evoked Potentials as a Biomarker for Concussion: A Pilot Study

Objective

This study aims to utilize a portable system capable of measuring steady-state visual evoked potentials (SSVEP) to investigate their use as an objective electrophysiologic biomarker for concussion.

Background

The most pressing issues in relation to sports related concussion (SRC) involves accurate and timely diagnosis, for a safe return to play criteria. Despite the vast range of tools available to help clinicians assess concussion, most are subjective, non-portable, and therefore non-ideal for unbiased application at the site and time of a suspected injury.

Design/Methods

This system applied a smartphone housed in a VR-frame delivering a 15-Hz flickering stimulus while a wireless electroencephalography (EEG) headset recorded EEG signals. Sixty-five male amateur rugby athletes (20.9 ± 2.3 years-old) were tested throughout a season and were stratified into healthy, concussed, and recovered groups based on clinical examinations pre- and post-competitive games. Players SSVEP responses was quantified into a signal-to-noise ratio (SNR) and summarized into respective study-groups for comparison of medians with 25th–75th interquartile range.

Results

All sixty-five participants completed a baseline evaluation preseason. Twelve participants sustained a diagnosed concussion during the season and were retested within 72 h of injury. Eight concussed players received additional SSVEP testing following a 2-week recovery period. Concussed participants had a significantly lower SNR [2.20 (2.04–2.38)] when compared to their baseline [4.54 (3.79–5.10)]. When clinically recovered, participant SNR [4.82 (4.13–5.18)] was not significantly different to their baseline. Baseline SNR of concussed and non-concussed participants [4.80 (4.07–5.68)] did not significantly differ.

Conclusions

This is the first study to show that SSVEPs are significantly attenuated in the presence of concussion in male athletes. Concussed individuals' ability to generate SSVEP appear to recover following clinical recovery. The observations of this study indicate SSVEP have the potential to be a supplemental aid for the assessment and management of concussion at point-of-care.

Cortical inexcitability defines an adverse clinical profile in amyotrophic lateral sclerosis

Background and purpose

In amyotrophic lateral sclerosis, studies using threshold‐tracking transcranial magnetic stimulation (TMS) have identified corticomotoneuronal dysfunction as a key pathogenic mechanism. Some patients, however, display no motor response at maximal TMS intensities, termed here an ‘inexcitable’ motor cortex. The extent to which this cortical difference impacts clinical outcomes remains unclear. The aim of this study was to determine the clinical profile of patients with inexcitability to TMS.

Methods

Motor cortex excitability was evaluated using TMS. Patients in whom a motor evoked potential could not be recorded in one or more limbs at maximal TMS intensities were classified as four‐limb or partially inexcitable. Demographic information, clinical variables and survival data were analysed.

Results

From 133 patients, 40 were identified with inexcitability. Patients with four‐limb inexcitability were younger (P = 0.03) and had lower‐limb disease onset (64%), greater functional disability (P < 0.001) and faster disease progression (P = 0.02), particularly if inexcitability developed within 1 year of symptoms (P < 0.01). Patients with partial inexcitability had higher resting motor thresholds compared to the excitable cohort (P < 0.01), but averaged short‐interval intracortical inhibition was similar (P = 0.5). Mean survival was reduced if inexcitability involved all limbs within 12 months of symptom onset (P = 0.04).

Conclusion

Amyotrophic lateral sclerosis patients with inexcitability of all four limbs to TMS have a distinct clinical profile of younger age and lower‐limb onset. Importantly, these patients display a more malignant disease trajectory, with faster progression, greater functional disability and reduced survival when occurring in early disease. This measure may provide an important prognostic marker in amyotrophic lateral sclerosis.

A prospective analysis of stroke recognition, stroke risk factors, thrombolysis rates and outcomes in Indigenous Australians from a large rural referral hospital

BACKGROUND

Cardiovascular disease is the most common cause of death and disability in Indigenous communities but limited prospective data exists about stroke.

AIM

To estimate the difference in stroke recognition, risk factors, treatment rates and outcomes between Indigenous and non-Indigenous peoples admitted to the Wagga Wagga Rural Referral Hospital (WWRRH) over a 5-year period with a suspected acute stroke.

METHODS

All suspected strokes presenting to the 33 peripheral hospitals within the Murrumbidgee local health district (MLHD) were transferred to the WWRRH and prospectively assessed over a 5-year period from 01/01/2012 to 31/12/2017. Actions at stroke onset, risks factors, stroke type, treatment and outcomes were analysed.

RESULTS

1843 patients were included. Of these, 45 patients (2.5%) were Indigenous. Only 26.6% of Indigenous and 34% of non-Indigenous patients knew of the fast acronym. Indigenous patients were younger (mean age 62.0 years versus 74.4 years) and more likely to have diabetes (RD 22.3% [95% CI: 3%,41.7%]), dyslipidaemia (RD 19.4% [95% CI: 21.%, 36.7%]), and be ever smokers (RD 24.9% [95% CI: 9.5%,40.3%]). Stroke types were similar except lacunar infarcts were more common (19.2% versus 8.4%). Treatment rates and outcomes were similar between the two groups.

CONCLUSIONS

Indigenous Australians with stroke are a decade younger and have a higher prevalence of important, modifiable stroke risk factors. Delayed presentation to hospital is more common, due in part to stroke symptoms being under recognized. When admitted to a specialized stroke unit, treatment rates and outcomes are comparable. This article is protected by copyright. All rights reserved.

Current and future applications of ultrasound imaging in peripheral nerve disorders

Neuromuscular ultrasound (NMUS) is a rapidly evolving technique used in neuromuscular medicine to provide complimentary information to standard electrodiagnostic studies. NMUS provides a dynamic, real time assessment of anatomy which can alter both diagnostic and management pathways in peripheral nerve disorders. This review describes the current and future techniques used in NMUS and details the applications and developments in the diagnosis and monitoring of compressive, hereditary, immune-mediated and axonal peripheral nerve disorders, and motor neuron diseases. Technological advances have allowed the increased utilisation of ultrasound for management of peripheral nerve disorders; however, several practical considerations need to be taken into account to facilitate the widespread uptake of this technique.

Steady-State Visual-Evoked Potentials as a Biomarker for Concussion: A Pilot Study

A variety of assessment tools are currently available to help clinicians assess Sports Related Concussion (SRC). Currently, the most widely available tools are neither objective nor portable, and are therefore not ideal for assessment at the site and time of a suspected injury. A portable system was developed to deliver a measurement of the steady-state visual-evoked potential (SSVEP). This system involved a smartphone housed in a Google Cardboard frame, which delivered a 15-Hz flicker visual stimulus while an electroencephalography (EEG) headset recorded EEG signals. Sixty-five rugby union players were tested during their regular season and were stratified into healthy, concussed, and recovered groups based on clinical examination. Their SSVEP response was quantified into a signal-to-noise ratio (SNR). The SNRs of players in each study group were summarized. Additionally, the SNRs of individual players who had baseline, post-injury, and post-recovery readings were analyzed. Sixty-five participants completed a baseline evaluation to measure their SSVEP. Twelve of these participants sustained a medically diagnosed concussion and completed SSVEP re-testing within 72 h. Eight concussed players received follow-up SSVEP testing after recovery. Concussed participants had a lower SNR [2.20 (2.04–2.38)] when compared to their baseline [4.54 (3.79–5.10)]. When clinically recovered, participant SNR was not significantly different to their baseline [4.82 (4.13–5.18)]. The baseline SNRs of the players who experienced a concussion during the season were not different to those of players who did not experience a concussion [4.80 (4.07–5.68)]. This is the first study to identify differences in SSVEP responses in male amateur rugby union players with and without concussion. It is also the first SSVEP demonstration for concussion evaluation at point-of-care. SSVEPs are significantly attenuated in the presence of concussion in these male athletes. Individuals returned to their baseline SSVEP following clinical recovery from the concussive injury. The use of SSVEPs has the potential to be a supplemental aid for the assessment and management of concussion.

Shearwave Elastography in the Differentiation of Carpal Tunnel Syndrome Severity

BACKGROUND

There is emerging evidence that ultrasound elastography may provide additional diagnostic information in peripheral neuropathies.

OBJECTIVE

To investigate the use of ultrasound elastography to evaluate median nerve stiffness in patients with carpal tunnel syndrome (CTS), as well as the relationship between the elastographic stiffness and electrophysiological severity.

DESIGN

Case control study.

SETTING

Tertiary hospital outpatient neurophysiology clinic.

PARTICIPANTS

Twenty eight patients (47 wrists) with CTS and 25 control patients (25 wrists).

INTERVENTIONS

None.

MAIN OUTCOME MEAURES

Ultrasound parameters (median nerve cross-sectional area [CSA] at carpal tunnel, ratio of median nerve CSA at carpal tunnel and forearm), shearwave elastography parameter (median nerve stiffness), and electrophysiological severity of carpal tunnel syndrome.

RESULTS

In patients with CTS, median nerve stiffness by ultrasound elastography was increased between the different severity groups (control 83.5 ± 24.8, EDx negative CTS 84.2 ± 46.4, mild 117.7 ± 79.3, moderate 144.0 ± 71.1, severe 196.6 ± 48.4). The control versus moderate and severe subgroup was statistically significant.

CONCLUSIONS

In total, this study has demonstrated that ultrasound elastography was able to discriminate the severity of CTS whereas conventional ultrasound parameters did not.

Sonographic assessment of nerve blood flow in diabetic neuropathy

AIMS

To undertake sonographic assessment of nerve blood flow in people with Type 2 diabetes and correlate the findings with neuropathy severity scores and electrophysiological measurements.

METHODS

Median and tibial nerve ultrasound scans were undertaken in 75 people with diabetes and 30 aged-matched controls without diabetes, using a high-resolution linear probe at non-entrapment sites. Nerve blood flow was quantified using power Doppler techniques to obtain the vessel score and the maximum perfusion intensity. Neuropathy severity was assessed using a total neuropathy score.

RESULTS

Diabetic nerves had higher rates of nerve blood flow detection (28%) compared to the control group (P < 0.0001). Significant correlations were found between nerve blood flow measurements and nerve size (P <0.001), reported sensory symptoms (P < 0.05) and neuropathy severity scores (P < 0.001). The cohort with diabetes had significantly larger median (8.5 ± 0.3 mm² vs 7.2 ± 0.1 mm² ; P < 0.05) and tibial nerves (18.0 ± 0.9 mm² vs 12.8 ± 0.5 mm² ; P < 0.05) compared with controls.

CONCLUSION

Peripheral nerve hypervascularity is detectable by ultrasonography in moderate to severe diabetic neuropathy with prominent sensory dysfunction.

Clinical and research applications of neuromuscular ultrasound in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder characterized by dysfunction at multiple levels of the neuraxis. It remains a clinical diagnosis without a definitive diagnostic investigation. Electrodiagnostic testing provides supportive information and, along with imaging and biochemical markers, can help exclude mimicking conditions. Neuromuscular ultrasound has a valuable role in the diagnosis and monitoring of ALS and provides complementary information to clinical assessment and electrodiagnostic testing as well as insights into the underlying pathophysiology of this disease. This review highlights the evidence for ultrasound in the evaluation of bulbar, limb and respiratory musculature and peripheral nerves in ALS. Further research in this evolving area is required.

Ultrasound elastography for the evaluation of peripheral nerves: A systematic review

Peripheral nerve disorders are commonly encountered in clinical practice. Electrodiagnostic studies remain the cornerstone of the evaluation of nerve disorders. More recently, ultrasound has played an increasing complementary role in the neuromuscular clinic. Ultrasound elastography is a technique that measures the elastic properties of tissues. Given the histological changes that occur in diseased peripheral nerves, nerve ultrasound elastography has been explored as a noninvasive way to evaluate changes in nerve tissue composition. Studies to date suggest that nerve stiffness tends to increase in the setting of peripheral neuropathy, regardless of etiology, consistent with loss of more compliant myelin, and replacement with connective tissue. The aim of this systematic review is to summarize the current literature on the use of ultrasound elastography in the evaluation of peripheral neuropathy. Limitations of ultrasound elastography and gaps in current literature are discussed, and prospects for future clinical and research applications are raised.

Correlation between markers of peripheral nerve function and structure in type 1 diabetes

BACKGROUND

Clinical and experimental studies in patients with type 1 and type 2 diabetes have demonstrated changes in ion channel function and nerve structure. In this study, we investigated the relationship between axonal dysfunction and morphological change in diabetic polyneuropathy by using neuromuscular ultrasound and nerve excitability techniques. We also explored possible differences in this relationship between type 1 and type 2 diabetes.

METHODS

Nerve ultrasound and corresponding motor excitability studies were undertaken in 110 diabetes patients (50 type 1; 60 type 2) and 60 age-matched controls (30 for each group). Neuropathy severity was assessed by using total neuropathy score. Median and tibial nerve cross-sectional areas were measured at nonentrapment sites by using high-resolution linear probe.

RESULTS

Median and tibial nerve cross-sectional areas were significantly higher in diabetes patients compared with controls: type 1 (median = 7.6 ± 0.2 mm² vs 6.3 ± 0.1 mm² ; tibial = 14.5 ± 0.7 mm² vs 10.8 ± 0.3 mm² , P < .05) and type 2 (median = 9.1 ± 0.3 mm² vs 7.2 ± 0.1 mm² ; tibial = 18.5 ± 1.0 mm² vs 12.8 ± 0.5 mm² , P < .05). In the type 1 cohort, significant correlations were found between nerve cross-sectional area and excitability parameters including resting current-threshold slope (median: r = 0.523, P < .0001; tibial: r = -0.571, P = .004) and depolarizing threshold electrotonus at 90 to 100 ms (median: 0.424, P < .01; tibial: r = 0.435, P = .030). In contrast, there was no relationship between excitability values and nerve cross-sectional area in the type 2 cohort.

CONCLUSIONS

This study has identified correlation between markers of axonal membrane function and structural abnormalities in peripheral nerves of type 1 diabetes patients. The differential relationship in nerve function and structure between type 1 and type 2 diabetes provides clinical evidence that different pathophysiological mechanisms underlie the development of neuropathy in these patient groups.

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.

021 Clinical implications of cortical dysfunction in motor neuron disease: a combined structural and functional approach

Introduction

Motor neuron disease (MND) is characterised by progressive failure of upper (UMN) and lower motor neurons (LMN). UMN dysfunction remains difficult to detect clinically, and the influence of cortical change on disease progression and prognosis remains unclarified. This study quantitatively assessed cortical dysfunction in vivo using a novel combined structural and functional approach.

Methods

Forty-one newly diagnosed MND patients and 30 controls prospectively underwent 3T diffusion tensor magnetic resonance imaging (DTI) to assess cerebral white matter structural integrity. DTI measures including apparent diffusion coefficient (ADC) and functional anisotropy (FA) were analysed using statistical parametric mapping. Threshold tracking transcranial magnetic stimulation (TT-TMS) studies were additionally performed across all four limbs to concurrently assess the functional integrity of the motor cortex. All patients underwent detailed clinical and cognitive assessment.

Results

Cortical abnormalities were prominent, with FA significantly reduced (p<0.01) and ADC enhanced (p<0.03) along the primary motor tracts in all MND patients, suggestive of primary axonal degeneration. These changes correlated with clinical function and disease duration. TT-TMS revealed evidence of cortical hyper-excitability over the motor cortex corresponding with clinical site-of-onset (p<0.05). Structural (FA) and functional (cortical hyper-excitability) changes correlated across all extremities. Patients without clinical UMN signs also showed evidence of UMN dysfunction, identifying subclinical change. Subgroup analysis identified the greatest changes in bulbar-onset patients (p<0.03).

Conclusion

This multimodal technique identified UMN dysfunction in patients prior to clinically detectable change, which may contribute to earlier diagnosis. More significant cortical involvement in bulbar-onset patients aligns with their poorer survival, highlighting the cortically driven determination of clinical progression and prognosis. Further clinical translation of such patterns may therefore lend insight into pathophysiological disease mechanisms and may influence stratification for clinical trials. Overall, this can serve as a robust biomarker for earlier diagnosis, disease progression and prognosis.

Effects of hemodialysis on intraneural blood flow in end-stage kidney disease

INTRODUCTION

We quantified intraneural blood flow (INBF) in 18 patients with end-stage kidney disease (ESKD) and examined its relationship with nerve size, neuropathy severity, and nerve excitability parameters.

METHODS

Sonographic measurements of the median nerve were performed at the same site before and after hemodialysis. INBF was quantified by analyzing power Doppler sonograms to obtain the vessel score (VSc) and maximum perfusion intensity (MPI). Corresponding median motor nerve excitability studies were performed. Neuropathy severity was assessed using Total Neuropathy Score.

RESULTS

A total of 39% of ESKD patients had detectable INBF compared with none in the control group (P < 0.0001). Patients with detectable INBF had larger nerves and more severe neuropathy (P < 0.01). INBF parameters were significantly reduced after a session of dialysis (VSc: P < 0.01; MPI: P < 0.01). A significant relationship was found between interdialytic change in INBF and changes in nerve excitability.

CONCLUSIONS

Increased INBF is a potential marker for neuropathy severity in ESKD patients. Muscle Nerve 57: 287-293, 2018.

The evolution of motor cortical dysfunction in amyotrophic lateral sclerosis

OBJECTIVE

The present study aimed to investigate alterations in cortical function in amyotrophic lateral sclerosis (ALS) related to disease progression.

METHODS

In total, clinical assessments were evaluated in 189 ALS patients, combined with assessment of cortical function utilising threshold tracking transcranial magnetic stimulation. Results were compared with disease stage. Disease stage was defined in three ways: (1) as a proportion of disease duration in deceased patients; (2) from the time of ALS onset; and (3) using the ALS rating scale-revised (ALSFRS-R).

RESULTS

Prospective studies in ALS patients demonstrated decreased neurophysiological index (p<0.0001) and decreased compound muscle action potential (CMAP) (p<0.0001), combined with abnormalities of central function including prolonged central motor conduction time (CMCT) (p<0.05), increased motor evoked potential/CMAP amplitude ratio (p<0.0001) and decreased short interval intracortical inhibition (SICI) (p<0.001). SICI at 3ms (p<0.05, β=-0.21) and averaged SICI (p<0.05, β=-0.21) decreased with disease progression, measured using proportion of disease duration. Alternatively, using time from disease onset, CMCT prolonged with disease progression (p<0.01, β=0.25), while ALSFRS-R decline correlated with decreased SICI at 3ms (p<0.01, β=0.20).

CONCLUSIONS

Clinical measures combined with assessment of cortical function established that SICI decreased with disease progression.

SIGNIFICANCE

These findings may suggest dysfunction of inhibitory interneurons with disease progression.

Peripheral nerve diffusion tensor imaging as a measure of disease progression in ALS

Clinical trial design in amyotrophic lateral sclerosis (ALS) remains hampered by a lack of reliable and sensitive biomarkers of disease progression. The present study evaluated peripheral nerve diffusion tensor imaging (DTI) as a surrogate marker of axonal degeneration in ALS. Longitudinal studies were undertaken in 21 ALS patients studied at 0 and 3 months, and 19 patients at 0, 3 and 6 months, with results compared to 13 age-matched controls. Imaging metrics were correlated across a range of functional assessments including amyotrophic lateral sclerosis functional rating scale revised (ALSFRS-R), lower limb muscle strength (Medical Research Council sum score, MRCSS-LL), compound muscle action potential amplitudes and motor unit number estimation (MUNE). Fractional anisotropy was reduced at baseline in ALS patients in the tibial (p < 0.05), and peroneal nerve (p < 0.05). Fractional anisotropy and axial diffusivity declined in the tibial nerve between baselines, 3- and 6-month scans (p < 0.01). From a functional perspective, ALSFRS-R correlated with fractional anisotropy values from tibial (R = 0.75, p < 0.001) and peroneal nerves (R = 0.52, p = 0.001). Similarly, peroneal nerve MUNE values correlated with fractional anisotropy values from the tibial (R = 0.48, p = 0.002) and peroneal nerve (R = 0.39, p = 0.01). There were correlations between the change in ALSFRS-R and tibial nerve axial diffusivity (R = 0.38, p = 0.02) and the change in MRCSS-LL and peroneal nerve fractional anisotropy (R = 0.44, p = 0.009). In conclusion, this study has demonstrated that some peripheral nerve DTI metrics are sensitive to axonal degeneration in ALS. Further, that DTI metrics correlated with measures of functional disability, strength and neurophysiological measures of lower motor neuron loss.

Quantitative muscle ultrasound as a biomarker in Charcot-Marie-Tooth neuropathy

OBJECTIVE

The utility of quantitative muscle ultrasound as a marker of disease severity in Charcot-Marie-Tooth (CMT) disease subtypes was investigated.

METHODS

Muscle ultrasound was prospectively performed on 252 individual muscles from 21 CMT patients (9 CMT1A, 8 CMTX1, 4 CMT2A) and compared to 120 muscles from 10 age and gender-matched controls. Muscle ultrasound recorded echogenicity and thickness in representative muscles including first dorsal interosseus (FDI) and tibialis anterior (TA).

RESULTS

Muscle volume of FDI and thickness of TA correlated with MRC strength. Muscle echogenicity was significantly increased in FDI (65.05 vs 47.09; p<0.0001) and TA (89.45 vs 66.30; p<0.0001) of CMT patients. In TA, there was significantly higher muscle thickness (23 vs 18 vs 16mm; p<0.0001) and lower muscle echogenicity (80 vs 95 vs 108; p<0.0001) in CMT1A compared to CMTX1 and CMT2A. This corresponded to disease severity based on muscle strength (MRC grading CMT1A vs CMTX1 vs CMT2A: 59 vs 48 vs 44; p=0.002).

CONCLUSION

In CMT, quantitative muscle ultrasound of FDI and TA is a useful marker of disease severity.

SIGNIFICANCE

The current findings suggest that quantitative muscle ultrasound has potential as a surrogate marker of disease progression in future interventional trials in CMT.

Utility of maximum perfusion intensity as an ultrasonographic marker of intraneural blood flow

We quantified intraneural blood flow (INBF) using perfusion measurement software (PixelFlux), and compared it with the qualitative method of counting blood vessels (vessel score) in a cohort of carpal tunnel syndrome (CTS) patients.

METHODS

Forty-seven patients (67 wrists) with a clinical and electrophysiological diagnosis of CTS, and 20 healthy controls (40 wrists) were enrolled. Median nerve ultrasound (US) was performed at the carpal tunnel inlet to measure the cross-sectional area (CSA) and vessel score. Power Doppler sonograms from nerves with detectable INBF were processed with PixelFlux to obtain the maximum perfusion intensity (MPI).

RESULTS

Forty-nine percent of CTS patients had detectable INBF compared with none in the control group (P < 0.0001). MPI correlated significantly with vessel score (r = 0.945, P < 0.0001), CSA (r = 0.613, P < 0.0001), and electrophysiological severity (r = 0.440, P < 0.0001). MPI had higher intra- or interobserver reliability compared with vessel score (0.95 vs. 0.47).

CONCLUSION

MPI is a better method for quantification of INBF. Muscle Nerve, 2016 Muscle Nerve 55: 77-83, 2017.

Skeletal muscle imaging in neuromuscular disease

Skeletal muscle imaging is increasingly used as a complement to clinical and electrophysiological examination in neuromuscular disease. Ultrasound and MRI have developed as the modalities of choice, each with strengths and limitations. Characteristic changes of muscle denervation and myopathy are seen on imaging which may delineate the nature of the disease process or help guide muscle biopsy. Identifying patterns of muscle involvement in hereditary myopathies may inform genetic testing. This review discusses skeletal muscle imaging in neuromuscular disease focusing on practical applications of current and emerging ultrasound and MRI techniques.

Ultrasound-guided percutaneous injection of methylene blue to identify nerve pathology and guide surgery

OBJECT The objective of this study was to provide a technique that could be used in the preoperative period to facilitate the surgical exploration of peripheral nerve pathology. METHODS The authors describe a technique in which 1) ultrasonography is used in the immediate preoperative period to identify target peripheral nerves, 2) an ultrasound-guided needle electrode is used to stimulate peripheral nerves to confirm their position, and then 3) a methylene blue (MB) injection is performed to mark the peripheral nerve pathology to facilitate surgical exploration. RESULTS A cohort of 13 patients with varying indications for peripheral nerve surgery is presented in which ultrasound guidance, stimulation, and MB were used to localize and create a road map for surgeries. CONCLUSIONS Preoperative ultrasound-guided MB administration is a promising technique that peripheral nerve surgeons could use to plan and execute surgery.

Advances in the neurological and neurosurgical management of peripheral nerve trauma

Peripheral nerve trauma frequently affects younger people and may result in significant and long-lasting functional disability. Currently, diagnosis and monitoring of peripheral nerve injury relies on clinical and electrodiagnostic information, supplemented by intraoperative electrophysiological studies. However, in a significant proportion of nerve injuries, the likelihood of spontaneous regeneration resulting in good functional outcome remains uncertain and unnecessary delays to treatment may be faced while monitoring for recovery. Advances in non-invasive imaging techniques to diagnose and monitor nerve injury and regeneration are being developed, and have the potential to streamline the decision-making process. In addition, advances in operative and non-operative treatment strategies may provide more effective ways to maximise functional outcomes following severe peripheral nerve trauma. This review discusses these advances in light of the current state of the art of management of peripheral nerve trauma.