Ultrasound in the Diagnosis and Monitoring of Amyotrophic Lateral Sclerosis: A Review

Abstract

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

Fasciculation frequency at the biceps brachii and brachialis muscles is associated with amyotrophic lateral sclerosis disease burden and activity

“…High fasciculation frequency at the BB muscles was associated with thicker BB muscles, as demonstrated by sonography, and stronger BB muscles on clinical examination. Moreover, our study results indicate that high fasciculation frequency at the BB muscles was associated with general indices of lesser disease severity, including higher sum thickness and higher sum MMT, thus serving as a biomarker for overall disease severity in line with previous studies 7,10,19 . Interestingly, we did not see the inverted U‐shaped association of fasciculation number with muscle strength and thickness, as shown by Vázquez‐Costa et al 10 This may be explained by our patient cohort having a longer mean disease duration and more advanced disease, as reflected by lower ALSFRS‐R scores, and therefore not representing earlier disease stages.…”

“…These findings are in line with the suggested pathophysiology of ALS. Fasciculations are more prominent at early stages of the disease 4,7,10 due to hyperexcitability, leading to aberrant firing of the damaged LMN 11 . Subsequently, fasciculation frequency decreases, as LMN degeneration occurs, leading to loss of muscle mass and strength 4,12,20 …”

“…Fasciculations, involuntary contractions of single motor units, represent one of the earliest characteristics of LMN involvement, and their detection by electromyography (EMG) allows earlier determination of an ALS diagnosis 1‐4 . Moreover, fasciculation assessment by muscle sonography showed increased sensitivity in ALS diagnosis compared with EMG 5‐7 . The biceps brachii muscle is the most common muscle showing fasciculations on ultrasonography, with the highest number of fasciculations 5,6,8‐10 …”

“…Better understanding about the role of fasciculations in ALS pathophysiology as an early sign of the hyperexcitable damaged LMN 4,7,10‐12 led to additional studies that investigated fasciculations not only as a diagnostic marker for ALS, but also as a marker for disease activity. Previous studies have shown that fasciculation frequency subsides with disease progression and is associated with faster decline of the ALS Functional Rating Score—Revised (ALSFRS‐R) at the time of their measurement 8,9 .…”

Textural markers of ultrasonographic nerve alterations in amyotrophic lateral sclerosis

“…A list containing all results of the correlation analysis is given in Table S3 online. Although most studies have focused on usage of CSA as a wellestablished nerve ultrasound biomarker in ALS, 1,6,26,27 our study has made the case that there is a significant amount of information hidden in the histogram and texture of the cross-sectional nerve image that is still underutilized if not neglected. Our findings point toward significant texture alterations in ALS that, interestingly, do not necessarily covary with the nerve CSA.…”