Afterdischarges in myotonic dystrophy type 1

OBJECTIVE

Electrodiagnostic testing is an important screening test for myotonic dystrophy type 1 (DM1). Although myotonic discharges are observed on electromyography in cases of DM1, it is difficult to distinguish DM1 from other myotonic disorders clinically. In the present study, afterdischarges, another type of pathological potential revealed by electrodiagnostic testing, were analyzed, and their role in distinguishing DM1 from other myotonic disorders was explored.

METHODS

Data from 33 patients with myotonic discharges on electromyography were analyzed retrospectively. According to gene testing, the patients were divided into DM1 (n = 20) and non-DM1 myotonia (n = 13) groups. Afterdischarges were investigated by retrospectively evaluating the electrodiagnostic findings of motor nerve conduction studies, F-waves, and repetitive nerve stimulations.

RESULTS

Afterdischarges were observed in 17 of the 20 patients with DM1, with an occurrence rate of approximately 85%. However, afterdischarges were absent in all patients with non-DM1 myotonia. There were significant differences in the occurrence rate between the two groups (P < 0.01).

CONCLUSION

Afterdischarges may serve as a suggestive role in clinical diagnosis of DM1. The discovery that DM1 can present with afterdischarges may pave a new way to study the pathogenesis of DM1.

Ulnar neuropathy

Ulnar neuropathy at the elbow is the second most common compressive neuropathy. Less common, although similarly disabling, are ulnar neuropathies above the elbow, at the forearm, and the wrist, which can present with different combinations of intrinsic hand muscle weakness and sensory loss. Electrodiagnostic studies are moderately sensitive in diagnosing ulnar neuropathy, although their ability to localize the site of nerve injury is often limited. Nerve imaging with ultrasound can provide greater localization of ulnar injury and identification of specific anatomical pathology causing nerve entrapment. Specifically, imaging can now reliably distinguish ulnar nerve entrapment under the humero-ulnar arcade (cubital tunnel) from nerve injury at the retro-epicondylar groove. Both these pathologies have historically been diagnosed as either "ulnar neuropathy at the elbow," which is non-specific, or "cubital tunnel syndrome," which is often erroneous. Natural history studies are few and limited, although many cases of mild-moderate ulnar neuropathy at the elbow appear to remit spontaneously. Conservative management, perineural steroid injections, and surgical release have all been studied in treating ulnar neuropathy at the elbow. Despite this, questions remain about the most appropriate management for many patients, which is reflected in the absence of management guidelines.

Carpal tunnel syndrome

Median neuropathy at the wrist, commonly referred to as carpal tunnel syndrome (CTS), is the most common entrapment neuropathy. It is caused by chronic compression of the median nerve at the wrist within the space-limited carpal tunnel. Risk factors that contribute to the etiology of compression include female gender, obesity, work-related factors, and underlying medical conditions, such as hypothyroidism, pregnancy, and amyloidosis. The diagnosis is made on clinical grounds, although these can be confounded by anatomical variations. Electrodiagnostic studies, which are specific and sensitive in diagnosing CTS, support the diagnosis; however, a subgroup may present with normal results. The advent of imaging techniques, including ultrasound and MRI, further assists the diagnostic process. The management of CTS is divided into the nonsurgical approaches that include hand therapy, splinting and corticosteroid injection, and surgical decompression of the carpal tunnel. Although several surgical techniques have been developed, no one method is more effective than the other. Each of these management approaches are effective at providing symptom relief and are utilized at different severities of the condition. There is, however, a lack of consensus on standardized diagnostic criteria, as well as when and to whom to refer patients for surgery.

Canine models of Charcot-Marie-Tooth: MTMR2, MPZ, and SH3TC2 variants in golden retrievers with congenital hypomyelinating polyneuropathy

Congenital hypomyelinating polyneuropathy (HPN) restricted to the peripheral nervous system was reported in 1989 in two Golden Retriever (GR) littermates. Recently, four additional cases of congenital HPN in young, unrelated GRs were diagnosed via neurological examination, electrodiagnostic evaluation, and peripheral nerve pathology. Whole-genome sequencing was performed on all four GRs, and variants from each dog were compared to variants found across >1,000 other dogs, all presumably unaffected with HPN. Likely causative variants were identified for each HPN-affected GR. Two cases shared a homozygous splice donor site variant in MTMR2, with a stop codon introduced within six codons following the inclusion of the intron. One case had a heterozygous MPZ isoleucine to threonine substitution. The last case had a homozygous SH3TC2 nonsense variant predicted to truncate approximately one-half of the protein. Haplotype analysis using 524 GR established the novelty of the identified variants. Each variant occurs within genes that are associated with the human Charcot-Marie-Tooth (CMT) group of heterogeneous diseases, affecting the peripheral nervous system. Testing a large GR population (n = >200) did not identify any dogs with these variants. Although these variants are rare within the general GR population, breeders should be cautious to avoid propagating these alleles.

Modern Treatment of Cubital Tunnel Syndrome: Evidence and Controversy

Cubital tunnel syndrome is the second most common peripheral mononeuropathy in the upper extremity. However, the diagnosis and treatment of cubital tunnel syndrome remains controversial without a standard algorithm. Although diagnosis can often be made from the patient's history and physical examination alone, electrodiagnostic studies, ultrasound, computed tomography (CT), and magnetic resonance image (MRI) can also be useful in diagnosing the disease and selecting the most appropriate treatment option. Treatment options include conservative nonoperative techniques as well as various surgical options, including in situ decompression with or without transposition, medial epicondylectomy, and nerve transfer in advanced disease. The purpose of this review is to summarize the most up-to-date literature regarding cubital tunnel syndrome and propose a treatment algorithm to provide clarity about the challenges of treating this complex patient population.

Electrodiagnostic Assessment of Myopathy

Electrodiagnostic testing is a useful tool in the evaluation of suspected myopathy and helps to confirm the presence of a myopathy and exclude disease mimickers. The electrodiagnostic pattern of findings during testing guides subsequent laboratory evaluation, genetic testing, and in identifying potential muscle biopsy targets. It also provides a baseline for subsequent assessment of disease progression or response to therapy. This article summarizes the approach to electrodiagnostic assessment in various myopathic disorders.

Expert consensus on the combined investigation of ulnar neuropathy at the elbow using electrodiagnostic tests and nerve ultrasound

The addition of ultrasound (US) to electrodiagnostic (EDX) tests can significantly enhance the accuracy of testing for ulnar neuropathy at the elbow (UNE). We aimed to obtain expert consensus to guide clinicians on the combined use of EDX and US in UNE investigation. Consensus was achieved using the Delphi method. Two consecutive anonymised questionnaires were submitted to 15 experts, who were asked to choose their level of agreement with each statement. Consensus was pre-defined as ≥ 80% rating agreement. The experts concluded that all investigations of UNE should include both nerve conduction studies and US. There was consensus that US should include cross-sectional area measurement and assessment of nerve mobility at the elbow, and that the entire ulnar nerve should be imaged. This study defined expert opinion on the 'core' techniques that should be used routinely in the UNE investigation using EDX and US. Areas with lack of consensus highlighted some controversial issues in the current use of these diagnostic modalities and the need for future research. This document is an initial step to guide clinicians on the combined investigation of UNE using EDX and US, to be regularly updated as new research emerges.

Average recovery time from delayed visual maturation

PURPOSE

The research aimed to investigate the average age of recovery in infants with delayed visual maturation (DVM). DVM is diagnosed retrospectively and there are currently no management guidelines. This study gives an evidence-based recovery time which can help clinicians to appropriately reassure anxious parents about DVM prognosis. This research is significant as this is the largest participant study about DVM to date.

METHOD

This is a retrospective service evaluation of 50 infants with DVM presenting to St James University Hospital between 2012 and 2017. The DVM was classified into either type I or type II. Several key variables were recorded including: patient gender, age at recovery, type of DVM and whether Electrodiagnostic testing was used.

RESULTS

STATA analysis showed that the average age of recovery for type I and type II DVM was 6.708 and 13.464 months, respectively. A multivariable linear regression adjusted for gender as a confounder. The average age of recovery was 6.179 months longer for infants with type II DVM which is a statistically significant difference (95% CI: 3.214-9.143, P value: < 0.001).

CONCLUSION

This research supports the hypothesis that the age of recovery in type I DVM is significantly shorter than type II when adjusted for gender. The main limitation is that recovery age is recorded from when the infants attended clinic, however; their vision could have recovered prior to this. In the future, additional multi-centre research needs to be conducted looking at larger patient samples to allow for further sub-categorisation of DVM types.

Evaluation for Late Nerve Transfer Surgery in Spinal Cord Injury: Predicting the Degree of Lower Motor Neuron Injury

PURPOSE

Nerve transfer surgery is used to restore upper extremity function following cervical spinal cord injury (SCI) with substantial variation in outcomes. The injury pattern in SCI is complex and can include isolated upper motor neuron (UMN) and combined UMN/lower motor neuron (LMN) dysfunction. The purpose of the study was to determine the most effective diagnostic technique for determining suitable candidates for nerve transfer surgery in SCI.

METHODS

Medical records were reviewed of patients who had nerve transfers to restore upper extremity function in SCI. Data collected included (1) preoperative clinical examination and electrodiagnostic testing; (2) intraoperative neuromuscular stimulation (NMS); and (3) nerve histopathology. Preoperative, intraoperative, and postoperative data were compared to identify predictors of isolated UMN versus combined UMN/LMN injury patterns.

RESULTS

The study sample included 22 patients with 50 nerve transfer surgeries and included patients ranging from less than 1 year to over a decade post-SCI. Normal recipient nerve conduction studies (NCS) before surgery corresponded to the intraoperative presence of recipient NMS and postoperative histopathology that showed normal nerve architecture. Conversely, abnormal recipient NCS before surgery corresponded with the absence of recipient NMS during surgery and patterns of denervation on postoperative histopathology. Normal donor preoperative manual muscle testing corresponded with the presence of donor NMS during surgery and normal nerve architecture on postoperative histopathology. An EMG of corresponding musculature did not correspond with intraoperative donor or recipient NMS or histopathological findings.

CONCLUSIONS

NCS better predict patterns of injury in SCI than EMG. This is important information for clinicians evaluating people for late nerve transfer surgery even years post-SCI.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Effectiveness of ultrasonography and nerve conduction studies in the diagnosing of carpal tunnel syndrome: clinical trial on accuracy

BACKGROUND

The aim of this study was to evaluate the effectiveness of two diagnostic tests routinely used for diagnosing carpal tunnel syndrome (CTS)-ultrasonography (US) and nerve conduction studies (NCS)-by comparing their accuracy based on surgical results, with the remission of paresthesia as the reference standard.

METHODS

We enrolled 115 patients, all of the female gender with a high probability of a clinical diagnosis of CTS. All patients underwent US and NCS for a diagnosis and subsequent surgical treatment. As a primary outcome, the accuracy of the US and NCS diagnoses was measured by comparing their diagnoses compared with those determined by the surgical outcomes. Their accuracy was secondarily evaluated based on before and after scores of the Boston Carpal Tunnel Questionnaire (BCTQ).

RESULTS

Overall, 104 patients (90.4%) were diagnosed with CTS by the surgical reference standard, 97 (84.3%) by NCS, and 90 (78.3%) by US. The concordance of NCS and surgical treatment (p < 0.001; kappa = 0.648) was superior to that of US and surgical treatment (p < 0.001; kappa = 0.423). The sensitivity and specificity of US and NCS were similar (p = 1.000 and p = 0.152, respectively: McNemar's test). The BCTQ scores were lower after surgery in patients diagnosed by both US and NCS (p < 0.001and p < 0.001, respectively: analysis of variance).

CONCLUSIONS

US and NCS effectively diagnosed CTS with good sensitivity but were not effective enough to rule out a suspicion of CTS.

TRIAL REGISTRATION

This study was registered at September, 10 th, 2015, and the registration number was NCT02553811 .

Ultrasound measurement of median nerve cross-sectional area at the inlet and outlet of carpal tunnel after carpal tunnel release compared to electrodiagnostic findings

INTRODUCTION

Ultrasound measurement of the cross-sectional area (CSA) of the median nerve can give information about regeneration of the nerve after carpal tunnel release (CTR), but the changes at selected follow-up points up to 1 year compared to electrodiagnostic findings are not known. We postoperatively measured the CSA of the median nerve with ultrasound and compared the measurements with electrophysiological findings over 12 months after open CTR.

MATERIALS AND METHODS

In 21 hands that underwent open CTR, the CSA of the median nerve was measured at the inlet (proximal CSA) and outlet (distal CSA) of the carpal tunnel at 3- 6- and 12-month follow-up. The respective ratios [(CSA postoperatively/CSA preoperatively) × 100] were calculated and correlated with distal motor latency (DML) and sensory nerve conduction velocity (SCV).

RESULTS

The proximal CSA ratio was 88.9, 84.5, and 78.4 % at 3-, 6-, and 12-month follow-up, respectively. Each value was significantly lower than that before surgery. The distal CSA ratio was 104.3, 99.1, and 91.8 % at 3-, 6-, and 12-month follow-up, respectively. The values were not significantly different compared to preoperative values.

CONCLUSIONS

The proximal CSA of the median nerve decreased continuously over the time after CTR while the distal CSA increased up to 3 months before it decreased continuously, too.

Evaluation of the adequacy of requests for electrodiagnostic examination in a tertiary referral center

OBJECTIVE

Diagnostic procedures are often overused in the attempt to substitute for the good clinical examination. The aim of this study was to evaluate the type and the accuracy of the referral diagnosis to our EMG lab, as well as the impact of electrodiagnostic (EDX) examination on the diagnosis of our patients.

METHODS

In this prospective study all patients examined in the six months period in a single tertiary referral EMG lab were analyzed. All patients were tested in a uniform fashion and by the same neurologist, according to the referral diagnosis.

RESULTS

EDX examination was performed in 570 patients. Most of the patients (43.9%) were referred with the diagnosis of polyneuropathy, lumbosacral (23.7%) or cervical (11.2%) radiculopathy and myasthenia gravis (11.6%). The outcome after EDX examination was: diagnosis confirmation in 49.6% of patients, new clinically relevant diagnosis in 16%, incidental diagnosis in 4% and normal EDX examination in 36.1% of patients. EDX examination confirmed referral diagnosis more often in patients referred by neuromuscular neurologists, while normal EDX finding was reported more often in patients referred by other neurologists.

CONCLUSION

This study has confirmed the inappropriateness of a large number of referrals to EDX testing, especially made by the non-neuromuscular neurologists.

Contralateral electrodiagnosis in patients with abnormal median distal sensory latency

BACKGROUND

We hypothesized that electrodiagnostic evidence of carpal tunnel syndrome (CTS) on the contralateral, less-severe side correlates with disease severity.

METHODS

We retrospectively reviewed 285 adults that had bilateral electrodiagnostic testing and a median distal sensory latency (DSL) greater than 3.6 ms on at least one side. Variables associated with abnormal contralateral median DSL were analyzed in bivariable and multivariable analysis.

RESULTS

Patients with a nonrecordable median DSL on the worst side were significantly more likely to have electrodiagnostic evidence of contralateral CTS compared to patients with a prolonged DSL on the worst side (90 versus 65 %, respectively; p < 0.001). Bilateral symptoms were reported by 75 % of patients. The best logistic regression model for electrodiagnostic evidence of contralateral CTS included nonrecordable median DSL of the worst side and polyneuropathy (p < 0.001 and p = 0.14, respectively).

CONCLUSIONS

The finding that disease severity relates to the probability of contralateral abnormalities is consistent with the concept that CTS is typically bilateral. Patients with CTS on one side should be advised of the likelihood that it can be present or may develop on the other side.

Clinical findings and electrodiagnostic testing in 108 consecutive cases of lumbosacral radiculopathy due to herniated disc. Neurophysiol Clin. 2013;43:205-215. [PMID: 24094906 DOI: 10.1016/j.neucli.2013.05.004]

STUDY AIM

This prospective study aim to examine whether clinical findings and electrodiagnostic testing (EDX) in patients with lumbosacral monoradiculopathy due to herniated disc (HD) differ as a function of root involvement level (L5 vs. S1) and HD zone (paramedian vs. intraforaminal).

PATIENTS AND METHODS

All patients with L4, L5 or S1 monoradiculopathy were prospectively enrolled at four electromyography (EMG) labs over a 2-year period. The diagnosis was based on a congruence between patient history and MRI evidence of HD. We compared the sensitivities of clinical findings and EDX with respect to both root involvement level and HD zone. Multivariate logistic regression was performed in order to verify the association between abnormal EMG, clinical, and neuroradiological findings.

RESULTS

One hundred and eight patients (mean age 47.7 years, 55% men) were consecutively enrolled. Sensory loss in the painful dermatome was the most frequent finding at physical examination (56% of cases). EMG was abnormal in at least one muscle supplied by femoral and sciatic nerves in 45 cases (42%). Inclusion of paraspinal muscles increased sensitivity to only 49% and that of proximal muscles was useless. Motor and sensory neurography was seldom abnormal. The most frequent motor neurographic abnormalities were a delay of F-wave minimum latency and decrease in the compound muscle action potential amplitude from extensor digitorum brevis and abductor hallucis in L5 and S1 radiculopathies, respectively. Sensory neurography was usually normal, the amplitude of sensory nerve action potential was seldom reduced when HD injured dorsal root ganglion or postganglionic root fibres. Multivariate logistic regression analysis showed that EMG abnormalities could be predicted by myotomal muscular weakness, abnormal deep reflexes, and paraesthesiae. The only clinical and electrophysiological differences with respect to root involvement level concerned deep reflexes and motor neurography of deep peroneal and tibial nerves.

CONCLUSIONS

Only some EDX parameters are helpful for the diagnosis of lumbosacral radiculopathy. EMG was abnormal in less than 50% of cases and its abnormalities could be predicted by some clinical findings. However, neurography is useful as a tool for differential diagnosis between radiculopathy and more diffuse disorders of the peripheral nervous system (polyneuropathy, plexopathy).