Serial electrodiagnostic testing: Utility and indications in adult neurological disorders

Although existing guidelines address electrodiagnostic (EDX) testing in identifying neuromuscular conditions, guidance regarding the uses and limitations of serial (or repeat) EDX testing is limited. By assessing neurophysiological change longitudinally across time, serial electrodiagnosis can clarify a diagnosis and potentially provide valuable prognostic information. This monograph presents four broad indications for serial electrodiagnosis in adult peripheral neurological disorders. First, where clinical change has raised suspicion for a new or ongoing lesion, EDX reassessment for spatial spread of abnormality, involvement of previously normal muscle or nerve, and/or evolving pathophysiology can clarify a diagnosis. Second, where diagnosis of a progressive neuromuscular condition is uncertain, electrophysiological data from a second time point can confirm or refute suspicion. Third, to establish prognosis after a static nerve injury, a repeat study can assess the presence and extent of reinnervation. Finally, faced with a limited initial study (as when complicated by patient or environmental factors), a repeat EDX study can supplement missing or limited data to provide needed clarity. Repeat EDX studies carry certain limitations, however, such as with prognostication in the setting of remote or chronic lesions, sensory predominant fascicular injury, or mild axonal injury. Nevertheless, serial electrodiagnosis remains a valuable and underused tool in the diagnostic and prognostic evaluation of neuromuscular conditions.

Electrodiagnostic findings in amyotrophic lateral sclerosis: Variation with region of onset and utility of thoracic paraspinal muscle examination

INTRODUCTION/AIMS

Limited data exist regarding variation of electrodiagnostic (EDX) findings in amyotrophic lateral sclerosis (ALS) patients with different onset regions and specificity of thoracic paraspinal muscle (TPSP) examination for confirming a diagnosis of ALS. We aimed to demonstrate the variation of EDX features and characterize the utility of TPSP muscle examination in the electrodiagnosis of ALS.

METHODS

This is a retrospective study of a large cohort of ALS patients who had a comprehensive EDX evaluation.

RESULTS

The study included 448 patients; all fulfilled the Gold Coast criteria for ALS. The average age at the time of EDX study was 64 years, and 41.1% were women. The onset region was identified as follows: bulbar (N = 149), cervical (N = 127), lumbosacral (N = 162), and other (N = 10). In contrast to limb onset, bulbar-onset patients more frequently demonstrated a pattern of normal or near normal needle electromyography (EMG) (p < .0001) and less frequently had abnormalities on EMG of TPSP (p = .002). Clinical or EDX diagnosis of sensory polyneuropathy was present in 12.6% patients, more frequently in the lumbosacral onset subgroup (p < .03). EMG showed active denervation in 9.6% and chronic denervation in 59% of craniobulbar muscles examined, without observed difference among different onset regions. TPSP showed higher frequencies of active and chronic denervation in ALS than a group of patients with non-ALS neuromuscular disorders.

DISCUSSION

EDX features may differ among ALS patients of different onset regions. TPSP EMG is highly useful in differentiating ALS from non-ALS neuromuscular disorders while the yield of craniobulbar muscles, especially for active denervation, is low.

Needle electromyography abnormalities in the upper trapezius muscle in neuromuscular disorders

BACKGROUND

: Needle electromyography (EMG) abnormalities in the trapezius muscle (TM) can be seen in neuromuscular disorders. The aim was to determine the characteristics of needle EMG abnormalities observed in the TM in neuromuscular disorders.

METHODS

The data of patients who applied to the Clinical Neurophysiology Laboratory of University of Health Sciences Adana City Training and Research Hospital between December 2018 and October 2021 were reviewed. Polio survivors, amyotrophic lateral sclerosis (ALS) patients, patients with sensorimotor polyneuropathy, patients with spinal cord lesions involving C2/C3/C4 segments, patients with spinal accessory nerve (SAN) lesions, neuralgic amyotrophy (NA) patients, and patients with myopathy were included. Needle EMG findings of the upper TM of the patients were analyzed. Positive sharp waves, fibrillation potentials, fasciculation potentials, myotonic discharges, and motor unit action potential (MUAP) changes were considered needle EMG abnormalities.

RESULTS

Eighty-one polio survivors, 23 ALS patients, 39 patients with sensorimotor polyneuropathy, 10 patients with cervical spinal lesions, eight NA patients, seven patients with SAN lesions, and three patients with myopathy were included in the study. Fifteen (65.2%) ALS patients, 18 (22.2%) polio survivors, three (30%) patients with cervical spinal lesions, two (5.1%) patients with sensorimotor neuropathy, one (12.5%) NA patient, seven (100%) patients with SAN lesions, and two (66.7%) patients with myopathies had at least one needle EMG abnormality in the TM. Fasciculation potentials in the TM were seen in 10 (43.5%) ALS patients. In four patients with SAN lesions and one polio survivor, MUAP could not be obtained from the TM.

DISCUSSION

There may be more frequent needle EMG abnormalities, particularly in ALS patients and patients with SAN lesions. Since the number of patients with myopathy included in this study was low, it is difficult to comment on the needle EMG features of the TM for these patients. In addition, this study indicated that fasciculation potentials in the TM are typical in ALS patients and that MUAP may not be obtained from the TM in patients with SAN lesions.

Quantitative electrodiagnosis of the motor unit

Electromyography (EMG) focuses on assessment of the motor unit (MU), and a given muscle has several hundred MUs, each innervating hundreds of muscle fibers. Assessment is limited by the recording radius of electrodes, 1-2 fibers with single-fiber electrodes and 7-15 fibers with concentric or monopolar electrodes. Routine qualitative EMG studies rely on observing MUs in free-run mode and qualitatively estimating common metrics. In contrast, quantitative EMG (QEMG) applied to routine studies includes assessment of individual MUs by software available in modern EMG machines with extraction of discrete values for common metrics, and also derived metrics. This results in greater precision and statistical interpretation. Other QEMG techniques assess muscle fiber density within the MU and time variability at the neuromuscular junction. The interference pattern can also be assessed. The number of MUs innervating a muscle can be estimated. Advanced signal processing, called near-fiber EMG, allows for extraction of underlying muscle fiber contributions to MU waveforms. It is also possible to use QEMG to make statistical probabilities of the state of a muscle as to whether normal, myopathic, or neuropathic. Time to acquire QEMG data is minimal. QEMG is most useful in situations where pathology is uncertain.

Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a fatal CNS neurodegenerative disease. Despite intensive research, current management of amyotrophic lateral sclerosis remains suboptimal from diagnosis to prognosis. Recognition of the phenotypic heterogeneity of amyotrophic lateral sclerosis, global CNS dysfunction, genetic architecture, and development of novel diagnostic criteria is clarifying the spectrum of clinical presentation and facilitating diagnosis. Insights into the pathophysiology of amyotrophic lateral sclerosis, identification of disease biomarkers and modifiable risks, along with new predictive models, scales, and scoring systems, and a clinical trial pipeline of mechanism-based therapies, are changing the prognostic landscape. Although most recent advances have yet to translate into patient benefit, the idea of amyotrophic lateral sclerosis as a complex syndrome is already having tangible effects in the clinic. This Seminar will outline these insights and discuss the status of the management of amyotrophic lateral sclerosis for the general neurologist, along with future prospects that could improve care and outcomes for patients with amyotrophic lateral sclerosis.

Selective atrophy of the cervical enlargement in whole spinal cord MRI of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a deadly neurodegenerative disorder affecting motor neurons in the spinal cord and brain. Studies have reported on atrophy within segments of the cervical cord, but we are not aware of previous investigations of the whole spinal cord. Herein we present our findings from a 3T MRI study involving 32 subjects (15 ALS participants and 17 healthy controls) characterizing cross-sectional area along the entire cord. We report atrophy of the cervical enlargement in ALS participants, but no evidence of atrophy of the thoracolumbar enlargement. These results suggest that MR-based analyses of the cervical cord may be sufficient for in vivo investigations of spinal cord atrophy in ALS, and that atrophy of the cervical enlargement (C4-C7) is a potential imaging marker for quantifying lower motor neuron degradation.

ULTRASOUND IN THE DIAGNOSIS AND MONITORING OF AMYOTROPHIC LATERAL SCLEROSIS: A REVIEW

Neuromuscular ultrasound is complementary to electrodiagnostic (EDx) testing and is useful in enhancing the diagnosis of mononeuropathies, peripheral nerve trauma, and demyelinating polyneuropathies. There is increasing interest in using ultrasound both to aid in the diagnosis of amyotrophic lateral sclerosis (ALS) and to monitor its progression. In this article we review the relevant literature on ultrasound in ALS. Ultrasound is more sensitive than EDx in identifying fasciculations in patients with ALS. It can detect decreased muscle thickness, increased muscle echointensity and echovariance, and reduced peripheral nerve size in these patients. Ultrasound is also a helpful tool in assessment of diaphragm function. Although additional studies are required to define the exact role of ultrasound in the evaluation and monitoring of ALS, it can improve the diagnostic yield in patients when ALS is suspected, but insufficiently supported, by clinical and EDx examinations. Muscle Nerve 60: 114-123, 2019.

Steering Peripheral Neuropathy Workup

Learning to recognize the various clinical and electrodiagnostic patterns of peripheral neuropathy enables a targeted approach to etiologic investigation, and subsequently guides patient discussions of self-management, disease course, and prognosis. Moreover, as advancements in neuropathology and pharmacotherapy inform the many etiologies of polyneuropathy, it is imperative for clinicians to identify the underlying etiology to appropriately guide treatment options and prevent complications.

Electrodiagnostic Testing for the Diagnosis and Management of Amyotrophic Lateral Sclerosis

Electrodiagnostic testing provides insight into subclinical aspects of disease in amyotrophic lateral sclerosis and helps to diagnose and exclude other diagnoses. It may also help to manage or track disease progression. Mapping the extent of subclinical disease may guide the clinician to supportive interventions. There is considerable interest in establishing electrodiagnostic biomarkers to monitor disease progression. This article details the usefulness of electrodiagnostic testing across the disease spectrum. A review of clinical presentations and differential diagnoses, diagnostic evaluation, and emerging applications of electrodiagnostic studies to guide management and assess response to treatment interventions are presented with considerations for clinical practice.

New insights into the pathophysiology of fasciculations in amyotrophic lateral sclerosis: An ultrasound study

OBJECTIVE

To describe the fasciculation pattern in ALS and to analyse its clinical and pathophysiological significance.

METHODS

Ultrasound of 19 muscles was performed in 44 patients with a recent diagnosis (<90 days) of ALS. The number of fasciculations was recorded in each muscle and the muscle thickness and strength were additionally measured in limb muscles. A subgroup of patients were electromyographically assessed.

RESULTS

US was performed in 835 muscles and EMG was available in 263 muscles. US detected fasciculations more frequently than EMG. Fasciculations were widespread, especially in upper limbs onset patients and in the cervical region. Fasciculations' number inversely associated with ALSFR-R and body mass index (BMI) and directly with BMI loss and upper motor neuron (UMN) impairment. Our statistical model suggest that fasciculations increase with the initial lower motor neuron (LMN) degeneration, reach their peak when the muscle became mildly to moderately weak, decreasing afterwards with increasing muscle weakness and atrophy.

CONCLUSIONS

Our study suggests that both UMN and LMN degeneration trigger fasciculations causing BMI loss. The degree of LMN impairment could account for differences in fasciculations' rates within and between muscles.

SIGNIFICANCE

In ALS, fasciculations could explain the link between hyperexcitability and BMI loss.