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Value of ultrasound assessment for traumatic nerve injury of the upper limb
Value of ultrasound assessment for traumatic nerve injury of the upper limb
REVIEWED BY Susan Diep | ASA SIG: Musculoskeletal
REFERENCE | Authors: Elshewi IE, Fatouh MM, Mohamed RNES, Basheer MA, Liethy NEE & Abbas HM
WHY THE STUDY WAS PERFORMED
Peripheral nerve trauma is rare; however, assessment and diagnosis of peripheral nerve injuries (PNI) can have significant effects on a patient’s prognosis. Peripheral nerve trauma contributes to 2–3% of patients who visit major trauma centres worldwide and equates to 13–23 per 100,000 patients annually. Causes of PNI can range from motor vehicle accidents, penetrating trauma, falls, and domestic and industrial accidents. Accurate and timely diagnosis of PNI can facilitate appropriate treatment and reduce disability for a patient.
Electrophysiological studies are considered the gold standard in assessing nerve injury. This study aimed to evaluate the use of ultrasound to assess upper limb traumatic nerve injuries and how it compares to electrophysiological studies.
HOW THE STUDY WAS PERFORMED
The study reviewed 69 adult participants with a total of 96 peripheral nerve injuries ranging from one month to three years in duration. All participants underwent both electrophysiological studies and high frequency ultrasound examinations.
Not only can ultrasound detect the type of injury and morphological abnormalities of the affected nerve but also allows for proper assessment of surrounding tissue.
WHAT THE STUDY FOUND
Although the gold standard is electrophysiological studies, the most accurate diagnostic information from these studies is accessible after 2 weeks when Wallerian degeneration has fully developed. It is not useful in the acute phases and has significant limitations when there is total loss of nerve conduction, whereby it has difficulty identifying the precise location of the lesion. Electrophysiological studies are also restricted in assessing the morphological changes with specific types of PNIs.
With ultrasound, it can be used during the acute phase of injury to diagnose PNI accurately and painlessly. Not only is it quick and affordable, but it also has the additional benefits of dynamic, real-time assessment and evaluation of the surrounding structures. The study also found that there was an increased echogenicity of the supplied muscle in 84.4% of the nerve injuries, with 71.9% in reduced muscle girth.
The study found there was no significant difference between ultrasound and electrophysiological studies for the diagnosis of nerve injuries.
RELEVANCE TO CLINICAL PRACTICE
The location of PNI can have major effects on a patient’s recovery and influence functionality. Most PNIs in the upper limb involve the ulnar, median and radial nerves. However, iatrogenic causes are also common. The specific mechanism of trauma increases the risk of specific nerve injury.
Ultrasound can effectively be used as a complementary diagnostic tool in the assessment of PNI. Not only can it detect the type of injury and assess morphological abnormalities, but it also allows for assessment of surrounding tissue including swelling, scar tissue and neuroma formation. Ultimately, proper assessment of nerve injuries can alter a patient’s management and treatment pathway.
When using US, it is essential to determine the following factors: whether the nerve is still continuous; the size and position of any gaps in the nerve course; the presence of any focal neuromas or extra nerve damage sites, such as tandem lesions; the presence of any foreign bodies; the degree of neighbouring scar tissue; and the condition of surrounding tissues and structures, such as tendons, arteries, and bones.
The key findings on ultrasound for PNI should assess and comment on:
Is the nerve continuous?
Is the nerve compressed/tethered/hypermobile to the adjacent structures?
The size and position of any gaps along the course of the nerve.
The presence of any focal neuromas or extra nerve damage sites (e.g. tandem lesions).
The presence of foreign bodies.
The degree of neighbouring scar tissue.
The condition of the surrounding tissues (e.g. tendon, artery, bones, etc.).
Finding the location of the peripheral nerve and applying pressure to the site and evaluating if this triggers the patient’s symptoms.
