Paul D. L. Kuypers

Median, ulnar, and combined median-ulnar nerve injuries: functional outcome and return to productivity.

BACKGROUND Forearm and wrist injuries are a common cause of morbidity and are often associated with suboptimal recovery of hand function. This study describes and compares outcome after median, ulnar, or combined median-ulnar nerve injuries. METHODS Three hundred thirteen wrist and forearm nerve injuries operated on between 1980 and 1997 in a large university hospital were reviewed in relation to complications, return to work, and sensor and motor recovery. Of these 313 patients, 220 (age range, 5-73 years) met the inclusion criteria. RESULTS Motor recovery, progress of sensory reinnervation, and number of severed structures were related to the type of injury (p < 0.05). Multiple linear regression analysis revealed a relation between the appearance of sensory reinnervation and motor recovery (beta = 0.02; 95% confidence interval, 0.01-0.04; p = 0.01). A probability of 24% of work loss, after a mean follow-up of 17.7 months, was found. Poor sensory and motor recovery were associated with work disability (odds ratio [OR], 2.9; p = 0.002; and OR, 2.9; p = 0.007, respectively). No relationship was found between type of injury and return to work (p = 0.47). Level of injury (OR, 2.6; p = 0.01), type of work (OR, 3.1; p = 0.002), number of complications (p < 0.001), and hand-therapy (OR, 0.24; p = 0.001) were found to influence return to work. CONCLUSION It may be concluded that peripheral nerve injuries at the forearm level can result in substantial functional loss and have major social consequences. This study identified factors influencing return to work that can be used to optimize postoperative treatment strategy.

Early psychological stress after forearm nerve injuries: a predictor for long-term functional outcome and return to productivity.

Forearm and wrist injuries can result in a nonfunctional hand caused by loss of motor and sensory functions. Psychological stress is known to accompany traumatic hand injuries and may therefore affect functional outcome. The authors conducted a retrospective study of 107 patients diagnosed with a median, ulnar, or combined median-ulnar nerve injury (79% response rate) who completed a questionnaire package consisting of the Impact of Event Scale (IES); Disabilities of Arm, Shoulder, and Hand; and a questionnaire concerning return to work and time off work. In an outpatient setting, motor and sensory recovery were examined. Ninety-four percent of those studied experienced early psychological stress. Thirty-six percent of patients reported sufficient symptoms 1 month postoperatively to be classified as in need for psychological treatment (IES score > 30 points). Combined median-ulnar nerve injuries (mean, 35.0 ± 20.3 points [standard deviation]) were accompanied by a higher psychological stress compared with single nerve injuries (median injuries: mean, 24.2 ± 20.6 points; ulnar injuries: mean, 22.6 ± 19.5 points;p = 0.049 and p = 0.021 respectively). Multiple linear regression adjusting for age, gender, and severity of the trauma revealed an association between the IES score and the functional symptom score (&bgr; = 0.51; 95% confidence interval [CI], 0.35–0.65), mean time off work (&bgr; = 0.44; 95% CI, 0.25–0.75), and motor recovery (grip: &bgr; = 0.37; 95% CI, 0.09–0.65; tip-pinch: &bgr; = 0.46; 95% CI, 0.13–0.80). Patients with higher scores on the IES were found to be at increased risk for incapacity for work (odds ratio, 3.32; 95% CI, 1.60–6.91). Higher education was found to be a protecting variable for posttraumatic psychopathology (&bgr; = −0.23; 95% CI, −6.05–−0.246). This study demonstrated a high level of early posttraumatic psychological stress after forearm and wrist nerve injuries. These data provide evidence that functional outcome and work resumption are influenced negatively by early psychological stress, independent from severity of the somatic trauma. This indicates that outcome after upper extremity nerve injuries may be influenced positively by psychological intervention.

Loss of viable neuronal units in the proximal stump as possible cause for poor function recovery following nerve reconstructions

Function recovery after nerve reconstructions is often poor. Could this be caused by a loss of viable neuronal units proximal to the nerve reconstruction? The number of neuronal units (i.e., a motor or sensory neuron, including its axon and axonal branches) in the proximal segments of reconstructed peripheral nerves were studied using a novel magnetic recording technique. In five rabbits a common personal nerve was transected and microsurgically reconstructed. After 8 weeks regeneration time the nerve compound action signals were recorded magnetically from the reconstructed as well as from the healthy contralateral peroneal nerve and from peroneal nerves of five unoperated control animals. The amplitudes of the recorded signals were compared and the diameter distribution histograms were calculated. These calculations were based on the conduction distance between the stimulator and the sensor and the conduction velocities of 30 different axon diameter classes ranging from 3 to 18 microns. Our results indicate that there is a reduction of approximately 50% in the number of viable neuronal units at 10 mm proximal to a simple nerve reconstruction after 8 weeks regeneration time. The number of neuronal units innervating a hand is strongly correlated with clinical function in a healthy hand. The reduction in viable neuronal units after a reconstruction, demonstrated in our experiments, corresponds with a frequently clinically observed decrease in function after nerve reconstructions. Therefore, we suggest that the number of viable neuronal units may be a good indicator of final functional recovery.

Sequential MR Imaging of Denervated and Reinnervated Skeletal Muscle as Correlated to Functional Outcome

PURPOSE To prospectively assess the short inversion time inversion-recovery (STIR) magnetic resonance (MR) signal intensity changes of denervated and reinnervated skeletal muscle over time in clinical patients. MATERIALS AND METHODS This study was approved by the institutional review board, and informed consent was obtained from all patients. Twenty-three patients with complete traumatic transection of the median or ulnar nerve in the forearm were prospectively followed for 12 months after surgical nerve repair. STIR MR images of selected intrinsic hand muscles were obtained 1, 3, 6, 9, and 12 months after nerve repair, and signal intensities of denervated and reinnervated muscles were measured semiquantitatively. After 12 months, hand function was assessed. Signal intensity ratios were correlated to functional outcome with analysis of variance. RESULTS Of the 23 patients, 10 had good function recovery, while 13 had poor recovery. For the group with good function recovery, mean signal intensity ratios of 1.267 ± 0.060 (standard deviation), 1.357 ± 0.116, 1.297 ± 0.111, 1.205 ± 0.096, and 1.086 ± 0.104 were found at 1-, 3-, 6-, 9-, and 12-month follow-up, respectively. In the group with poor recovery, mean signal intensity ratios of 1.299 ± 0.056, 1.377 ± 0.094, 1.419 ± 0.117, 1.398 ± 0.111, and 1.342 ± 0.095 were found at 1-, 3-, 6-, 9-, and 12-month follow-up, respectively. Comparison of the group with poor function recovery and the group with good function recovery showed significant differences at 6-, 9-, and 12-month follow-up (P = .035, P = .001, and P < .001, respectively), with normalizing signal intensities in the group with good function recovery and sustained high signal intensity in the group with poor function recovery. CONCLUSION STIR MR imaging can be used to differentiate between denervated and reinnervated muscles for at least 12 months after nerve transection.

Nerve compound action current (NCAC) measurements and morphometric analysis in the proximal segment after nerve transection and repair in a rabbit model

Abstract  In the evaluation of nerve regeneration using magneto‐neurography (MNG), the proximal segment showed a reproducible decrease in peak–peak amplitude of the nerve compound action currents (NCAC) of 60%. To explain these changes, morphometry of myelinated axons in the proximal segment is compared to the MNG signals. A standardised nerve transection and reconstruction was performed in rabbits. NCACs were measured approximately 5 cm proximal to the lesion from operated and control nerves after 12 weeks. Histological samples were taken from the same area of the nerve where the NCACs were obtained. Results showed a decrease of the peak–peak amplitude of the NCAC of 57% compared to the control. Conduction velocity decreased 15%(not significant). Morphometry elicited a decrease in larger (10–15 μm) axons (284 ± 134 vs 82 ± 55) and an increase in smaller (2–5 μm) axons (1445 ± 360 vs 1921 ± 393). A strong correlation existed between the decrease in amplitude and the decrease in larger axons (0.85). Peak–peak amplitude varies approximately with the square of the diameter axon. Therefore, because peak–peak amplitude is mainly dependent on the larger‐diameter axons, the decrease in peak–peak amplitude of the NCACs may be explained by a decrease in numbers of 10–15‐μm axons.

A magnetic evaluation of peripheral nerve regeneration : II. The signal amplitude in the distal segment in relation to functional recovery

Motor and sensory function in a healthy nerve is strongly related to the number of neuronal units connecting to the distal target organs. In the regenerating nerve the amplitudes of magnetically recorded nerve compound action currents (NCACs) seem to relate to the number of functional neuronal units with larger diameters regenerating across the lesion. The goal of this experiment was to compare the signal amplitudes recorded from the distal segment of a reconstructed nerve to functional recovery. To this end, the peroneal nerves of 30 rabbits were unilaterally transected and reconstructed. After 6, 8, 12, 20, and 36 weeks of regeneration time the functional recovery was studied based on the toe‐spread test, and the nerve regeneration based on the magnetically recorded NCACs. The results demonstrate that the signal amplitudes recorded magnetically from the reconstructed nerves increase in the first 12 weeks from 0% to 21% of the amplitudes recorded from the control nerves and from 21% to 25% in the following 23 weeks. The functional recovery increases from absent to good between the 8th and the 20th week after the reconstruction. A statistically significant relation was demonstrated between the signal amplitude and the functional recovery (P < 0.001). It is concluded that the magnetic recording technique can be used to evaluate the quality of a peripheral nerve reconstruction and seems to be able to predict, shortly after the reconstruction, the eventual functional recovery.

Changes in the compound action current amplitudes in relation to the conduction velocity and functional recovery in the reconstructed peripheral nerve

The average axon diameter in the proximal segment of a transected and reconstructed peripheral nerve will decrease shortly after the transection and increase again when the regenerating axons make contact with their targets. The magnetically recorded nerve compound action current (NCAC) amplitude and the conduction velocity (CV) are directly related to the axon diameters. In this experiment, the peroneal nerve was unilaterally transected and reconstructed in 42 rabbits. After 3, 4.5, 6, 8, 12, 20, and 36 weeks of regeneration time, hind leg motor function recovery, NCAC amplitude, and CV1st peak were studied. Our results demonstrate a significant decrease in signal amplitude and CV in the first 8 weeks after reconstruction. These decreases are related (P < 0.05). After 8 weeks of regeneration time, motor function and the CV of the recorded signals start to recover, but the signal amplitudes do not. Based on the correlation of the CV and signal amplitude with axon diameter, they would both be expected to increase with recovering function. As an explanation for this lack of increase of signal amplitude, we suggest that, at the same time as some axons reach their target organs and start to mature, a number of the axons which have not reached a proper target organ will lose their signal‐conducting capability. This will cause a decrease in compound signal amplitude, which cancels out the expected increase in NCAC amplitude, due to axonal maturation.

A magnetic evaluation of peripheral nerve regeneration: I. The discrepancy between magnetic and histologic data from the proximal segment

Histologic techniques can quantify the number of axons in a nerve, but give no information about electrical conductibility. The number of functional myelinated neuronal units in a nerve can be quantified based on a magnetic recording technique. When studying reconstructed peripheral nerves a significant difference between the results found with these two techniques can be observed. A comparison was made between the long‐term changes in the number of histologically and magnetoneurophysiologically measured neuronal units proximal to a nerve reconstruction. This study was performed on 6 New Zealand White rabbits, 20 weeks after the peroneal nerve had been reconstructed. The contralateral nerves were used as a control. Histologic examination demonstrates a statistically significant decrease of approximately 5% in the number of myelinated fibers. The magnetoneurophysiological results demonstrate a decrease which is estimated to be caused by the loss of approximately 50% of the functional myelinated neuronal units in the nerve. Therefore we conclude that of the initially available myelinated neuronal units, 5% degenerate completely, 45% are vital but lose their signal conducting capability, and the remaining 50% are vital and continue to conduct signals. Apparently, only this latter group of 50% of the initially available functional neuronal units appears to remain available for functional recovery.

Long-term reproducibility of phantom signal intensities in nonuniformity corrected STIR-MRI examinations of skeletal muscle

ObjectNerve regeneration could be monitored by comparing MRI image intensities in time, as denervated muscles display increased signal intensity in STIR sequences. In this study long-term reproducibility of STIR image intensity was assessed under clinical conditions and the required image intensity nonuniformity correction was improved by using phantom scans obtained at multiple positions.MethodsThree-dimensional image intensity nonuniformity was investigated in phantom scans. Next, over a three-year period, 190 clinical STIR hand scans were obtained using a standardized acquisition protocol, and corrected for intensity nonuniformity by using the results of phantom scanning. The results of correction with 1, 3, and 11 phantom scans were compared. The image intensities in calibration tubes close to the hands were measured every time to determine the reproducibility of our method.ResultsWith calibration, the reproducibility of STIR image intensity improved from 7.8 to 6.4%. Image intensity nonuniformity correction with 11 phantom scans gave significantly better results than correction with 1 or 3 scans.ConclusionsThe image intensities in clinical STIR images acquired at different times can be compared directly, provided that the acquisition protocol is standardized and that nonuniformity correction is applied. Nonuniformity correction is preferably based on multiple phantom scans.

MR intensity measurements of nondenervated muscle in patients following severe forearm trauma

Fluid increases resulting in higher MRI signal intensities in T2‐weighted and short tau inversion recovery (STIR) sequences can be used to diagnose nerve injury. By comparing the signal intensities over time, MRI may become a new method for monitoring the healing process. Muscle edema is assessed by comparing the signal intensity of affected muscle with that of nonaffected muscle. However, in severe forearm trauma, the signal of nondenervated muscle may also be increased by wound edema, thus masking the effect of denervation. Hence, the purpose of this study was to investigate the influence of wound edema on muscle signal intensity in 29 consecutive patients examined on a 1.5‐T MRI scanner at 1, 3, 6, 9 and 12 months after severe forearm trauma. The long‐term course of wound edema and the influence of wound distance were thus investigated using a standardized imaging, calibration and post‐processing protocol. The signal intensities of nondenervated intrinsic hand muscles were measured in the affected and contralateral sides. Muscle signal intensities were increased on the trauma side at 1 and 3 months (18% and 7.4%, respectively; p < 0.001) and normalized thereafter. In the contralateral hand, no significant signal changes were seen. No relationship was found between wound distance and the severity of wound edema. This study shows that wound edema influences muscle signal intensity comparisons in patients with forearm trauma. When comparing denervated muscle with nondenervated muscle, an additional scan of the contralateral side is indicated during the first 6 months after trauma to assess the extent of wound edema. After 6 months, the ipsilateral side can be used for muscle signal intensity comparisons. Copyright