Neurotmesis of Peripheral Nerves: Risk Factors for False-Negative Exams

When it comes to neurotmesis of peripheral nerves, early intervention tends to lead to better outcomes. But when many trauma patients are initially admitted to the emergency department, it isn’t always clear that they have a neurotmetic injury. A resulting false-negative initial nerve exam can then lead to a potentially worse outcome for the patient.

But are certain patients more susceptible to a false-negative exam than others?

In their 2021 study, Loewenstein et al. wanted to see if there are risk factors associated with initial false-negative nerve examinations for trauma patients with neurotmesis of an upper extremity nerve.

Causes of a False-Negative Exam

Looking at physician-, injury- and patient- related factors, Lowenstein et al. performed a retrospective chart review of 288 patients from one pediatric and two adult trauma centers from January 2013 to January 2017. All centers were located at one Midwestern city and all patients had confirmed upper extremity peripheral neurotmetic injuries.

Here’s what they found:

• • Site of Injury

The elbow was found to be the injury site most likely to receive a false-negative examination, with a significantly higher adjusted odds ratio than any other injury site. The study authors also noted that when it came to distracting vs. non-distracting injuries, the rate of false-negative and true-positive examinations were not significantly different.

• • Type of Injury

Gunshot wound injuries were found to have the highest adjusted odds ratio for a false-negative examination at the initial encounter. Loewenstein et al. believe that this could be attributed to the fact that they often cause an extensive zone of injury, which may result in a combination of injuries and mask the presence of peripheral upper extremity nerve injuries to physicians. For these patients, they note that initial nonoperative management with serial examinations to assess spontaneous recovery may be beneficial prior to exploration.

• • Patient Age

Patients in the study ranged in age from 0 to 80 years, with the greatest number of patients falling into the 21- to 30-year-old group. The adjusted odds ratio for the likelihood of a false-negative examination was highest in the 71– to 80-year-old group, with their odds being 216 times higher than the 10 years and younger group.

• • Physician Specialty

The most common initial providers were emergency medicine physicians (81.6%) followed by upper extremity specialists (12.8%) and trauma surgeons (5.6%). Upper extremity specialists were found to have the highest odds of correctly identifying a nerve laceration. Specialty-specific training and differences, the study authors surmise, may account for the higher false-negative examination rates among the other specialties.

After controlling for confounding, physician specialty and gunshot wound mechanism were found to be independent risk factors for false-negative nerve examinations. Conversely, the data showed that the likelihood for missed nerve injuries decreased four-fold between the initial and subsequent patient encounters.

The study authors note that current practice guidelines recommend repeat examinations in most trauma patients to identify injuries that were not clearly evident on the initial presentation, and this should be applied to patients who may have an upper extremity nerve injury as well.

Overall, given that their study showed that upper extremity specialists had the lowest false-negative examination rate, Loewenstein et al. recommend referring patients to a specialist as quickly as possible in order to prevent a delay in diagnosis and potentially improve their outcomes.

Patients Want Early Referral to Nerve Surgeon

Delays in diagnosis can also lead to delays in treatment, which can affect the degree of disability in peripheral nerve injury patients. A 2021 study published in the Journal of Plastic and Reconstructive Surgery focused on the connection between delays in surgical treatment and patients’ quality of life.

Researchers surveyed 209 nerve injury patients from a nerve surgeon’s referral-based practice who had been admitted between 2014 and 2019.  A large number of participants reported that surgery improved their quality of life to a moderate (76.6%) or significant (59.8%) degree.

However, 70% of participants felt as though they should have been referred earlier for surgery and 83% felt that having had an earlier referral would have improved their quality of life. The study authors noted that most of these patients had received multiple referrals before being evaluated by a nerve surgeon, and many patients experienced frustrations with delays during the referral process before meeting with a nerve surgeon. They recommend the need for interdisciplinary management of these patients and the creation of treatment algorithms that incorporate both medical and surgical input.