Modern MR-Diagnostics of upper extremity related nerve injuries – MODERN pilot study

Status:

completed 04/2023

Aims:

Traumatic nerve lesions of the upper extremity are most frequent seen in young males with devastating and potential life-long impairment for all activities of daily living. Currently diagnostic comprises clinical examinations and electroneurography monitoring the regain of function in the long-term process. Therefore, the aim of the present study was to evaluate the potential of magnetic resonance (MR) neurography for early visualization of the reinnervation process in order to accelerate clinical decision making. Since nerve lesions may also occur in patients after fractures fixated with metallic hardware, visualization of the nerve under this special condition were also evaluated in the present study.

Activities/Methods:

The study part with patients after acute traumatic nerve lesions was a clinical prospective cohort trail, undertaken at two centres (BG Klinik Ludwigshafen, BG Unfallklinik Frankfurt). Of the n=23 patients 78% are male on average 35 years old (SD=12.5). In total 33 nerves were affected (81% totally transected, 19% partly transected). MR neurography, electroneurography, assessment of sensoric function (WEST Test, 2PD) and motoric function (Grip strength) and questionnaires of function of upper extremity (DASH), quality of life (SF-36), pain (PainDetect) and psychological strain (IES-R, DASS) were measured immediately after operation (T1), 4 month post OP (T2), 12 month post (T3) and 18 month post (T4).

For the study part with patients after fractures of the upper extremity fixated by metallic hardware only a singular MR neurography was obtained. Of the n=16 included patients, 50% are female, on average 50 years (SD=15.1).

Results:

Patients after acute traumatic nerve injury of the upper extremity are showing for the most measurements a significant regain in function (DASH, p<0,001; WEST-Test, p<0.01, grip strength, p<0.001, pinch grip, p=0.109). Electroneurographic measurements are also showing this positive trend. At T4 44% of the patients are demonstrating mostly full reinnervation for the motoric measurements and 19% for the sensory measurements. Clinical relevant posttraumatic psychological strain was seen in 44% of the patients at T4 and 60% of the patients complain about neuropathic pain at this time point. Despite of the overall positive trend in all different clinical measurements, results on an individual level are heterogenic with no or minor correlation in-between. For MR neurography the fractional anisotropy values (FA) are reported. They are showing a significant U-shaped trend over the 4 time points. Increase in FA values after T2 were accompanied by the positive trend in functional measurements. However, data on individual level are heterogeneous and no stringent correlation was found. Therefore, we build an overall score, which comprises the DASH score, WEST Test, grip strength and sensory and motoric electroneurography results. For the overall score at T4 a significant correlation to FA Values at T2 could be demonstrated (r = 0.46, p=0.03).

In the study part regarding the visualization of the integrity of the nerve with present metallic hardware an indirect assessability of the integrity of the nerve is always possible and a direct assessability in most cases.

Conclusion: In the present study MR neurographic results after acute traumatic nerve lesions were systematically evaluated and correlated to clinical outcomes. Results are demonstrating a correlation between the FA values 4 month after operation with the final overall results after 18 month. Thus demonstrating an additionally value of MR neurography in prognosis of regeneration after nerve lesion. Further results of the present study are proofing, that the integrity of a nerve could be evaluated despite the presence of metallic hardware. The technical details developed in the present study to optimize the MR neurographic measurement can now be applied by other clinicians.

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