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Background: We compared rates of successful polyethylene glycol (PEG) nerve fusion between two epineural suture repairs (2SR) and five epineural suture repairs (5SR) in a rat sciatic nerve transection neurorrhaphy model. We hypothesise that the two and five epineural neural suture repair groups will achieve a similar rate of PEG fusion., Methods: Twenty-five Lewis rats underwent bilateral sciatic nerve transection. Primary neurorrhaphy (PN) consisting of 2SR in one hind limb and 5SR in the contralateral hind limb was performed utilizing PEG fusion. Successful PEG fusion was confirmed by a distal muscle twitch after nerve stimulation proximal to the nerve fusion site. Sciatic nerve conduction velocity (SNCV) across the repair site and the force generated by tibialis anterior muscle (TAM) contraction were also compared between the 2SR and 5SR groups., Results: Success rates were 100% for the 2SR and the 5SR groups. No statistically significant differences in SNCV ( P = 0.444) or isometric tetanic TAM contractile force ( P = 0.820) were observed between 2SR and 5SR in the setting of PEG fusion., Conclusion: These findings demonstrate no significant difference in successful PEG fusion between the 2SR and 5SR groups. In addition, the findings demonstrate no statistically significant differences in SNCV or isometric tetanic TAM contractile force following sciatic nerve transection when performing a 2SR or 5SR PN in the setting of PEG fusion. Successful PEG fusion can be achieved acutely with either a two or five-epineural suture repair in a rat model., Competing Interests: There are no conflicts of interest., (Copyright: © 2024 Surgical Neurology International.)

The United States continues to be impacted by decades of an opioid misuse epidemic, worsened by the COVID-19 pandemic and by the growing prevalence of highly potent synthetic opioids (HPSO) such as fentanyl. In instances of a toxicity event, first-response administration of reversal medications such as naloxone can be insufficient to fully counteract the effects of HPSO, particularly when there is co-occurring substance use. In an effort to characterize and study this multi-faceted problem, the Camden Opioid Research Initiative (CORI) has been formed. The CORI study has collected and analyzed post-mortem toxicology data from 42 cases of decedents who expired from opioid-related toxicity in the South New Jersey region to characterize substance use profiles. Co-occurring substance use, whether by intent or through possible contamination of the illicit opioid supply, is pervasive among deaths due to opioid toxicity, and evidence of medication-assisted treatment is scarce. Nearly all (98%) of the toxicology cases show the presence of the HPSO, fentanyl, and very few (7%) results detected evidence of medication-assisted treatment for opioid use disorder, such as buprenorphine or methadone, at the time of death. The opioid toxicity reversal drug, naloxone, was detected in 19% of cases, but 100% of cases expressed one or more stimulants, and sedatives including xylazine were detected in 48% of cases. These results showing complex substance use profiles indicate that efforts at mitigating the opioid misuse epidemic must address the complications presented by co-occurring stimulant and other substance use, and reduce barriers to and stigmas of seeking effective medication-assisted treatments., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Kusic et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Pharmacogenetics (PGx) has the potential to improve opioid medication management. Here, we present patient perception data, pharmacogenetic data and medication management trends in patients with chronic pain (arm 1) and opioid use disorder (arm 2) treated at Cooper University Health Care in Camden City, NJ. Our results demonstrate that the majority of patients in both arms of the study (55% and 65%, respectively) are open to pharmacogenetic testing, and most (66% and 69%, respectively) believe that genetic testing has the potential to improve their medical care. Our results further support the potential for CYP2D6 PGx testing to inform chronic pain medication management for poor metabolizers (PMs) and ultrarapid metabolizers (UMs). Future efforts to implement PGx testing in chronic pain management, however, must address patient concerns about genetic test result access and genetic discrimination.

Background: The opioid use disorder and overdose crisis in the United States affects public health as well as social and economic welfare. While several genetic and non-genetic risk factors for opioid use disorder have been identified, many of the genetic associations have not been independently replicated, and it is not well understood how these factors interact. This study is designed to evaluate relationships among these factors prospectively to develop future interventions to help prevent or treat opioid use disorder., Methods: The Genomics of Opioid Addiction Longitudinal Study (GOALS) is a prospective observational study assessing the interplay of genetic and non-genetic by collecting comprehensive genetic and non-genetic information on 400 participants receiving medication for opioid use disorder. Participants will be assessed at four time points over 1 year. A saliva sample will be collected for large-scale genetic data analyses. Non-genetic assessments include validated surveys measuring addiction severity, depression, anxiety, and adverse childhood experiences, as well as treatment outcomes such as urine toxicology results, visit frequency, and number of pre and post-treatment overdoses extracted from electronic medical records., Discussion: We will use these complex data to investigate the relative contributions of genetic and non-genetic risk factors to opioid use disorder and related treatment outcomes.

Background: Diagnosis of carpal tunnel syndrome is based on clinical symptoms, examination findings, and electrodiagnostic studies. For carpal tunnel syndrome, the most useful of these are nerve conduction studies. However, nerve conduction studie can result in ambiguous or false-negative results, particularly for mild carpal tunnel syndrome. Increasing the number of nerve conduction studie tests improves accuracy but also increases time, cost, and discomfort. To improve accuracy without additional testing, the terminal latency index and residual latency are additional calculations that can be performed using the minimum number of tests. Recently, the median sensory-ulnar motor latency difference was devised as another way to improve diagnostic accuracy for mild carpal tunnel syndrome., Aims: The median sensory-ulnar motor latency difference, terminal latency index, and residual latency were compared for diagnostic accuracy according to severity of carpal tunnel syndrome., Study Design: Diagnostic accuracy study., Methods: A total of 657 subjects were retrospectively enrolled. The carpal tunnel syndrome group consisted of 546 subjects with carpal tunnel syndrome according to nerve conduction studie (all severities). The control group consisted of 121 subjects with no hand symptoms and normal nerve conduction studie. All statistical analyses were performed using SAS v9.4. Means were compared using one-way ANOVA with the Bonferroni adjustment. Sensitivity, specificity, positive predictive value, and negative predictive value were compared, including receiver operating characteristic curve analysis., Results: For mild carpal tunnel syndrome, the median sensory-ulnar motor latency difference showed higher specificity and positive predictive value rates (0.967 and 0.957, respectively) than terminal latency index (0.603 and 0.769, respectively) and residual latency (0.818 and 0.858, respectively). The area under the receiver operating characteristic was highest for the median sensory-ulnar motor latency difference (0.889), followed by the residual latency (0.829), and lastly the terminal latency index (0.762). Differences were statistically significant (median sensory-ulnar motor latency difference being the most accurate). For moderate carpal tunnel syndrome, sensitivity and specificity rates of residual latency (0.989 and 1.000) and terminal latency index (0.983 and 0.975) were higher than those for median sensory-ulnar motor latency difference (0.866 and 0.958). Differences in area under the receiver operating characteristic curve were not significantly significant, but median sensory-ulnar motor latency difference sensitivity was lower. For severe carpal tunnel syndrome, residual latency yielded 1.000 sensitivity, specificity, positive predictive value, negative predictive value and area beneath the receiver operating characteristic curve. Differences in area under the receiver operating characteristic curve were not significantly different., Conclusion: The median sensory-ulnar motor latency difference is the best calculated parameter for diagnosing mild carpal tunnel syndrome. It requires only a simple calculation and no additional testing. Residual latency and the terminal latency index are also useful in diagnosing mild to moderate carpal tunnel syndrome.

Many studies have shown an inverse relationship between axon length (or height) and nerve conduction velocity. A linear relationship was assumed, but there is no physiologic indication the relationship is linear. Furthermore, a linear relationship between height and velocity leads to implausibly low velocities for very long nerves. We propose that power regression analysis would produce more accurate results, in line with physiology. In a power regression the goal is to determine exponent x that best fits the curve V = kLx where k is a constant and L is nerve length. In a previous study, the authors established that the product of conduction time T and energy E or TE = kL3. Mathematical derivation from this relationship yields V2/V1 = (L2/L1)(-0.5), or, velocity V is inversely proportional to the square root of length. Data from 22 normal Ulnar Motor Nerve Conductions showed a very high correlation with this formula (exponent x = -0.529 SE = 0.21, theoretical value -0.5). Data from other researchers also supports this relationship. Overall, Ulnar Motor Nerve Motor Conduction Velocity appears to be inversely proportional to the square root of height. We believe this relationship holds for all long nerves.

Numerous studies have shown that peripheral nerves conduct slower distally than proximally. This slowing is gradual at first, and more pronounced approaching the distal end of the nerve. At first glance, distal slowing appears not to make physiologic sense, as it slows reaction time and coordination compared with a hypothetical nerve that does not slow distally. However, distal slowing decreases energy consumption, crucial in a high energy system. A previous study had shown that exponential slowing correlated well with experimental data, and resulted in significant energy savings. In this study, a series of equations was created to determine the degree of slowing to minimize both conduction time and velocity. The solution, Latency L = kd(.785) where k is a constant and d is the distance from the distal end of the nerve, correlates extremely closely with experimental data. This equation can be easily used to accurately predict normal latencies at different points along a nerve, and to detect subtle distal nerve pathology.

Carpal Tunnel Syndrome (CTS) is easily the most common focal peripheral nerve compression. The primary diagnostic tool is electrodiagnosis, although 13-27% of patients with symptoms and signs of CTS have normal electrodiagnostic results. The goal of this study was to create a more sensitive and specific latency difference criteria without any additional testing beyond the minimum. Statistical theory indicates that this would occur by comparing the latency most sensitive to CTS to the least sensitive latency. Data was evaluated from 68 normal hands, 23 hands of patients with symptoms and signs of CTS but normal standard results, and 88 hands of patients with CTS symptoms and signs of CTS with the diagnosis confirmed with standard criteria. The Median Sensory latency was the most sensitive parameter, while the Ulnar Motor Latency varied least in the presence of CTS, making the (Median Sensory-Ulnar Motor) latency difference the criteria of choice. Setting a cutoff value of 0.8 msecs for this difference correctly classified all normals, and all hands with CTS by standard criteria, and classified as abnormal 19/23 (82%) of hands with symptoms and signs of CTS but negative results by standard criteria. Overall the (Median Sensory-Ulnar Motor) Latency difference is a simple, easy, sensitive and specific test for CTS.

Carpal Tunnel Syndrome (CTS) is the most common peripheral nerve entrapment. In the diagnosis of Carpal Tunnel Syndrome, velocity is determined by either measuring the average velocity over a segment by dividing the distance by the difference in latencies. Polynomial interpolation can determine the velocity at any point along a nerve. Applying interpolation techniques correctly classified 58/60 electrophysiologically proven CTS cases (96.7%) and 36/38 normals (94.7%). Of 7 cases with CTS by standard sensory criteria alone, 6 (86%) had abnormal motor conduction using the interpolation technique. This shows that interpolation techniques can improve diagnostic accuracy in CTS. It also indicates that there is motor involvement in most cases of CTS, including a majority of cases previously classified as only sensory involvement.

Several studies have shown an increased incidence of Carpal Tunnel Syndrome (CTS) with increasing age, as well as a longer Median sensory latency in older CTS patients. In this study, data was analyzed from 19 patients with bilaterally normal UE EMG/NCS and no symptoms of CTS (38 hands), as well as 18 patients with unilateral CTS and 21 with bilateral CTS (60 hands) to determine the effect of age on the severity of nerve conduction abnormalities associated with CTS. Most of these parameters showed increasing severity with age. Median motor latency rises sharply with age (r = .41, p = .001), and amplitude falls (r = .34, p = .008). Median sensory rises significantly with age in CTS patients (r = .42, p = .001) and amplitude falls (r = .29, p = .022). Furthermore, the (Median-Ulnar) motor and sensory latency differences both rise with age (r = .40, p = .001, and r = .35, p = .004 respectively). This is crucial, for an increase in Median motor or sensory latency with age could represent a similar degree of pathologic slowing superimposed on normally slower conduction with age. However, the sharp rise in the (Median-Ulnar) latency differences (from 2.2 msecs at age 40 to 3.8 msecs at age 70 for motor, and 1.6 msecs to 2.5 msecs for sensory) shows that the compression is more severe with age.

Objective: To derive a mathematical model for peripheral axon geometry, and apply it to the prediction of latencies along a nerve., Design: Retrospective review of data from individuals with bilaterally normal EMG/NCS, those with a diagnosis of carpal tunnel syndrome alone, and data from previous researchers., Setting: Electrodiagnostic laboratory at a teaching hospital., Subjects: Twenty-two (22) individuals with bilaterally normal EMG/NCS, and 61 hands from 40 individuals with carpal tunnel syndrome. Data from previous researchers was also utilized., Results: Applying an exponentially tapering axon model to normal data yielded a formula for latency (L = kd 0.775) where k is a constant, and d is the distance from the distal end of the nerve. This formula produced a correlation of 0.777 for predicting median distal motor latencies using the proximal latency, and 0.676 for the ulnar nerve. The largest difference between predicted and actual distal latency was 0.48 msecs for the median nerve and 0.60 msecs for the ulnar nerve. This formula correctly classified as abnormal 3 (37.5%) out of 8 carpal tunnel syndrome cases with completely normal motor studies by standard criteria. This formula also agreed well with the data of other researchers, predicting normal distal latencies, F wave latencies, and identifying abnormal data., Conclusions: A single model for axon geometry based on uniform exponential tapering accurately predicts latencies for many nerves, and can detect subtle neuropathology.

Objective: Carpal Tunnel Syndrome (CTS) is commonly bilateral, but symptoms and EMG/NCS abnormalities may be seen unilaterally. This study was designed to determine whether there are any subclinical nerve conduction abnormalities on the "uninvolved" side., Design: Statistical analysis of electrodiagnostic data., Setting: Outpatient academic electrodiagnostic laboratory., Patients: Twenty-two successive patients referred for bilateral upper extremity NCS/EMG with no symptoms or physical signs of CTS and totally normal results, and ten successive patients with an EMG/NCS diagnosis of CTS on one side, and completely normal EMG/NCS on the contralateral side., Results: The median motor and sensory latencies at the wrist were significantly longer in the contralateral "uninvolved" limb than normals (median motor latency 3.75 vs. 3.30 msecs, p = 0.0005, median sensory latency 3.40 vs 3.00 msecs, p = 0.0002). Median sensory amplitude was smaller in the contralateral limb (30.5 uV vs. 41.5 uV, p = 0.0062). The (median-radial) D1 sensory latency difference was greater in the contralateral wrist (0.2 vs. 0.0 msecs, p = 0.0217). The (median-ulnar) sensory latency difference was not significantly increased (0.15 vs. 0.10 msecs, p = 0.2020)., Conclusions: The contralateral limbs of patients with unilateral CTS show significant differences from normals in 4 out of 5 nerve conduction parameters. There is evidence of frequent subclinical median nerve compression in this group.

Objectives: To determine the reliability of contraction-induced upper extremity H reflexes; to calculate normal values for latency, amplitude, and side-to-side variation; and to correlate latency to arm length., Design: Case series., Setting: Electrophysiology laboratory of a tertiary care center., Participants: Twenty-three healthy volunteers (4 men, 19 women), aged 19 to 42., Intervention: Volunteers were tested bilaterally for H reflexes in four to six upper extremity muscles during an isometric contraction., Main Outcome Measures: H reflex onset latency, onset to negative peak amplitude, side-to-side variation, normal ranges, and latency versus arm-length correlation., Results: H reflexes were found at all 264 sites tested. Mean latencies varied from 9.5 to 27 msec. Maximum normal side-to-side variation was 1.5 to 2.7 msec. Maximum normal amplitude ratios (larger to smaller) ranged from 2.06 to 4.80. Abductor pollicis brevis (APB) and abductor digiti minimi (ADM) H reflex latencies were strongly correlated to arm length. Correlation for APB = .64 (p<.0001) and for ADM = .70 (p<.0001)., Conclusions: Contraction-induced upper extremity H reflexes occur consistently in healthy adults, with latencies, amplitudes, and side-to-side variation occurring in predictable ranges.