Quantitative STIR of muscle for monitoring nerve regeneration.

PURPOSE: To assess whether short tau inversion recovery (STIR) MRI sequences can provide a tool for monitoring peripheral nerve regeneration, by comparing signal intensity changes in reinnervated muscle over time, and to determine potential clinical time points for monitoring. MATERIALS AND METHODS: For this prospective study, 29 patients with complete traumatic transection of the ulnar or median nerves in the forearm were followed up to 45 months postsurgery. Standardized 1.5 Tesla STIR-MRI scans of hand muscles were obtained at fixed time intervals. Muscle signal intensities were measured semi-quantitatively and correlated to functional outcome. RESULTS: For the patients with good function recovery, mean signal intensity ratios of 1.179 ± 0.039, 1.304 ± 0.180, 1.154 ± 0.121, 1.105 ± 0.046 and 1.038 ± 0.047 were found at 1-, 3-, 6-, 9-, and 12-month follow-up, respectively. In the group with poor function recovery, ratios of 1.240 ± 0.069, 1.374 ± 0.144, 1.407 ± 0.127, 1.386 ± 0.128 and 1.316 ± 0.116 were found. Comparing the groups showed significant differences from 6 months onward (P < 0.001), with normalizing signal intensities in the group with good function recovery and sustained elevated signal intensity in the group with poor function recovery. CONCLUSION: MRI of muscle can be used as a tool for monitoring motor nerve regeneration, by comparing STIR muscle signal intensities over time. A decrease in signal intensity ratio of 50% (as compared to the initial increase) seems to predict good function recovery. Long-term follow-up shows that STIR MRI can be used for at least 15 months after nerve transection to differentiate between denervated and (re)innervated muscles. J. Magn. Reson. Imaging 2016;44:401-410.

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.

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

OBJECT: Nerve 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. METHODS: Three-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. RESULTS: With 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. CONCLUSIONS: The 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.

Spaghetti wrist trauma: functional recovery, return to work, and psychological effects.

BACKGROUND: Few studies on spaghetti wrist trauma have been published. The study populations have all consisted of small numbers of patients, and most studies have focused on functional recovery. In addition, different definitions of this injury have been used. The objective of this study was to assess outcome for a larger group of patients in terms of functional recovery, return to work potential, and psychological distress, and to compare outcomes between the two most commonly used definitions for spaghetti wrist injury. METHODS: The initial study-population consisted of 67 patients. Fifty patients completed a questionnaire package consisting of the Disabilities of Arm, Shoulder, and Hand questionnaire, including the Functional Symptom Score (range, 0 to 100), a questionnaire to evaluate return to work and time off work (range, 0 to 52), and the Impact of Event Scale (range, 0 to 75). Motor recovery and sensory recovery were assessed in an outpatient setting, on average, 10 years (range, 2 to 18) after the operation (n = 43). RESULTS: The mean Functional Symptom Score was 15.1 (SD, 16.1; range, 0 to 74) after a mean follow-up of 10.0 years (SD, 4.4; range, 2 to 18). Mean time off work was 34.7 weeks (SD, 17.9; range, 4 to 52), and 45.2 percent of the patients could not return to work within 1 year after the injury. Mean score on the Impact of Event Scale was 26.2 (SD, 19.7; range, 2 to 69). Compared with the unaffected hand, grip and tip pinch strength were decreased with means of 23.5 percent (SD, 22.4; range, 0 to 93) and 33.9 percent (SD, 23.7; range 0 to 83), respectively. Regarding sensory recovery, 12 patients (27.9 percent) had no protective sensation. No statistical differences were found between the two different definitions. CONCLUSIONS: This study demonstrated that spaghetti wrist injury can be placed among the severe disabling injuries. Comparison of the two definitions did not reveal any differences in outcome. To complete the evaluation of long-term outcome, a patient-derived assessment of function can be added to the clinical examination, and attention should be paid to psychological distress following the injury.

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

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 current's (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 microm) axons (284 +/- 134 vs 82 +/- 55) and an increase in smaller (2-5 microm) 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-microm axons.

Predictors for return to work in patients with median and ulnar nerve injuries.

PURPOSE: One of the consequences of median and ulnar nerve trauma is delayed return to work. The aim of this study was to determine return to work (RTW) and risk factors for delayed RTW in addition to time off work (TOW). Differences among median, ulnar, and combined median-ulnar nerve injuries were examined. METHOD: In this study 96 patients who were employed at the time of injury and who had undergone surgery for median, ulnar, or combined nerve injuries between 1990 and 1998 were evaluated. The response rate was 84% (n = 81). RESULTS: Within 1 year after injury, 59% (n = 48) returned to work. Mean TOW was 31.3 weeks. Return to work after combined nerve injuries was 24% versus after isolated median (80%) and ulnar (59%) nerve injuries. Level of education, type of job, and compliance to hand therapy were predictors for RTW. Furthermore, grip strength loss, tip pinch strength loss, and sensory recovery differed strongly between the RTW and no-RTW population. CONCLUSIONS: The predictors found in this study increase our understanding of delayed RTW after median and ulnar nerve injury and may be used to optimize postinjury rehabilitation.

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 (beta = 0.51; 95% confidence interval [CI], 0.35-0.65), mean time off work (beta = 0.44; 95% CI, 0.25-0.75), and motor recovery (grip: beta = 0.37; 95% CI, 0.09-0.65; tip-pinch: beta = 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 (beta = -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.