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Biomedical subjects

J Thomas Megerian

Publications and source records attributed to J Thomas Megerian.

9 recordsLinked to original sources
PubMed2006

Repeatability of nerve conduction measurements using automation.

OBJECTIVE: To quantify nerve conduction study (NCS) reproducibility utilizing an automated NCS system (NC-stat, NeuroMetrix, Inc.). METHOD: Healthy volunteers without neuropathic symptoms participated in the study. Their median, ulnar, peroneal, and tibial nerves were tested twice (7 days apart) by the same technician with an NC-stat instrument. Pre-fabricated electrode arrays specific to each nerve were used. Both motor responses (compound motor action potential [CMAP] and F-waves - all nerves) and sensory responses (sensory nerve action potentials [SNAP] - median and ulnar nerves only) were recorded following supramaximal stimuli. Automated algorithms determined all NCS parameters: distal motor latency (DML), mean F-wave latency (FWL), distal sensory latency (DSL), CMAP amplitude, and SNAP amplitude. Latency was adjusted for skin temperature deviation from reference. Pearson correlation coefficient (CC), intraclass correlation coefficient (ICC), coefficient of variance (CoV), and relative intertrial variation (RIV) were calculated. RESULTS: Fifteen subjects participated in either upper or lower extremity studies with nine participating in both. With the exception of CMAP amplitude, all parameters had CoV less than 0.06. Upper extremity amplitude parameters had CCs greater than 0.85. CCs for latencies were greater than 0.80 except for the median nerve FWL (CC = 0.69). For lower extremity nerves, ICCs were highest for mean FWL (>0.90), followed by DML (>0.82) and then CMAP (peroneal 0.33, tibial 0.73). The 10th to 90th RIV percentiles were bounded by +/-7% for F-wave latencies; +/- 9% for all DSLs; and +/- 11% for DML (except peroneal at 15%). CONCLUSIONS: The reproducibility of NCS parameters obtained with an automated NCS instrument compared favorably with traditional electromyography laboratories. F-wave latencies had the highest repeatability, followed by DML, DSL, SNAP and CMAP amplitude. Given their high reproducibility, automated NCS instrument may encourage wider utilization of NCS in clinical and research applications.

Action Potentials↗
PubMed2006

Diabetic nerve conduction abnormalities in the primary care setting.

BACKGROUND: Nerve conduction studies (NCS) are the most objective measure of nerve function, and their use is recommended in the clinical and epidemiological evaluation of diabetic polyneuropathy (DPN). The purpose of this study was to utilize automated NCS technology to characterize nerve conduction of patients with diabetes in primary care settings. METHODS: The Diabetes cohort was drawn from 28 community clinics. The Control cohort consisted of subjects without diabetes and without evidence of neuropathy. Bilateral peroneal NCS were performed with an automated NCS instrument (NC-stat, NeuroMetrix, Inc., Waltham, MA). Neuropathic symptoms were quantified using an abbreviated form of the NTSS-6 questionnaire. Risk factors for abnormal NCS were determined using multivariate regression modeling. RESULTS: Data were collected for 172 control subjects and 1,358 subjects with diabetes. Statistically significant differences in peroneal NCS were found. Of the Diabetes cohort, 75.1% had at least one NCS abnormality, and 53.2% had bilateral abnormalities. Of the asymptomatic patients, 45% had bilateral NCS abnormalities. By contrast, 40% of those with clinically significant symptoms lacked bilateral NCS abnormalities. Independent predictors for bilateral NCS abnormalities were age, height, weight, hemoglobin A1c (HbA1c), and duration of diabetes. Up to 16% of the variance in NCS measurements was explained by HbA1c, duration of diabetes, and several demographic variables. CONCLUSIONS: This study suggests that automated NCS can provide nerve conduction confirmation of DPN in primary care settings and has clinical utility. These findings have important implications for the clinical and epidemiological evaluation of DPN.

Adult↗
PubMed2004

Time course and predictors of median nerve conduction after carpal tunnel release.

PURPOSE: To identify predictors of outcome and of electrophysiologic recovery in patients with carpal tunnel syndrome (CTS) treated by endoscopic carpal tunnel release using a nerve conduction testing system (NC-Stat; NEUROMetrix, Inc, Waltham, MA). METHODS: Validity of the automated nerve conduction testing system was shown by comparing presurgical distal motor latencies (DMLs) against a reference obtained by referral to an electromyography laboratory. The DML was evaluated in 48 patients with CTS. Measurements were obtained within 1 hour of surgery and at 2 weeks, 6 weeks, 3 months, and 6 months after carpal tunnel release. Presurgical and postsurgical DMLs were then compared and correlated with variables and possible predictors of outcome including age, body mass index, gender, and presurgical DMLs. RESULTS: The automated nerve conduction testing system DMLs matched those of reference electromyography/nerve conduction study values with high correlation. Sensitivity of the automated nerve conduction testing system when compared with a standardized CTS case definition was 89%, with a specificity of 95%. A significant correlation was found between the DML before release and the DML 1 hour after release. Moreover, maximal postsurgical DML improvement was highly dependent on the presurgical DML, with no improvement shown for the <4-ms group, mild improvement for the 4-to-6-ms group, and maximal improvement in the >6-ms group. Among the clinical variables of age, gender, and body mass index only age was mildly predictive of postrelease DML changes at 6 months. No other correlations between clinical variables and postsurgical DMLs were significant. In addition the predictive value of age was lost when combined with the presurgical DML in a multivariate analysis. CONCLUSIONS: Postsurgical changes in the median nerve DML were highly dependent on the prerelease latency. The sensitivity and specificity of a nerve conduction monitoring system in detecting and aiding in the diagnosis of CTS is useful in the long-term management of patients with CTS and can aid in determining the level of improvement in median nerve function after endoscopic carpal tunnel release.

Adult↗
PubMed2004

Median and ulnar nerve conduction measurements in patients with symptoms of diabetic peripheral neuropathy using the NC-stat system.

BACKGROUND: Diabetic peripheral neuropathy (DPN) is a common, disabling, and costly complication of diabetes mellitus. Although there are multiple methods for detecting and monitoring DPN, nerve conduction studies (NCS) are generally considered to be the most sensitive and reproducible. However, utilization of NCS in patients with diabetes is low, presumably because of limited access and economic issues. Advanced point-of-service NCS systems, already widely used in the assessment of entrapment neuropathies, may address these issues in the arena of diabetes. METHODS: Seventeen patients with diabetes and clinical evidence of neuropathy were enrolled in the study. NCS were performed using the NC-stat nerve conduction testing system (NEUROMetrix, Inc., Waltham, MA) and compared against results from a neurologist-supervised study using a standard electromyography system, which was considered the reference method. Results for ulnar and median distal motor latencies (DMLs) and F-waves, obtained by both methods, were compared with each other. The NC-stat measurements were also compared with a historical control population. RESULTS: A high correlation between the two methods of NCS assessment was demonstrated. The Pearson correlation coefficients between the NC-stat system and the reference measurements were 0.96 (DML) and 0.89 (F-wave latency) for the median nerve and 0.70 (DML) and 0.78 (F-wave latency) for the ulnar nerve. Significant differences were observed between the NC-stat and reference median (P < 0.001, paired t test) and ulnar (P < 0.05, paired t test) nerve DMLs. F-wave latencies did not demonstrate significant differences (P > 0.05, paired t test). The rate of abnormalities ranged from 17.7% for the median nerve DML to 26.7% for the ulnar nerve F-wave latency. The rate of upper extremity nerve involvement in DPN according to a case definition requiring both median and ulnar nerve abnormalities was 25.0%. The rate of median neuropathy at the wrist, which is the second most common neuropathy in individuals with diabetes, was 17.6%. CONCLUSIONS: NC-stat-based NCS of the median and ulnar nerves provide results similar to those obtained with traditional neurologist-supervised NCS using a standard electromyography system. The number of subjects meeting electrophysiological criteria for DPN, affecting the upper extremities, is similar to prior studies. The widespread availability of the NC-stat system may provide a robust and objective method for identifying DPN and other neuropathies in patients with diabetes.

Biosensing Techniques↗
PubMed2002

Homocystinuria presenting as psychosis in an adolescent.

Homocystinuria usually presents with ectopia lentis, mental retardation, thromboembolic complications, and skeletal abnormalities. Whereas neuropsychiatric abnormalities are often recognized in untreated homocystinuria, initial presentation with acute psychosis has only rarely been reported. We describe a previously well 17-year-old adolescent with an acute psychosis characterized by auditory and visual hallucinations and marked paranoia who was found to have pyridoxine-responsive homocystinuria. His mental state normalized within several weeks of inception of pyridoxine and antipsychotic therapy. Pyridoxine-responsive homocystinuria is commonly missed on neonatal screens and should be recognized as a potentially treatable cause of acute psychosis in childhood and adolescence.

Acute Disease↗
PubMedDate not supplied

Utility of nerve conduction studies for carpal tunnel syndrome by family medicine, primary care, and internal medicine physicians.

INTRODUCTION: Nerve conduction studies (NCS) are increasingly being performed at the point-of-service by family medicine, primary care, and internal medicine (FM/PCP/IM) physicians. Carpal tunnel syndrome (CTS) is a common neuropathy often diagnosed with the aid of NCS. METHODS: A retrospective analysis of a point-of-service NCS data registry was conducted; 1190 patients who underwent NCS by 613 FM/PCP/IM physician practices, for evaluation of CTS were analyzed. Utility measures included demographic and electrophysiological characteristics of study population, adherence to evidence-based testing guidelines, and relevance of diagnostic outcomes. RESULTS: Tested patients tended to be over 40, female, and overweight or obese. The median nerve distal motor latency was 4.4 +/- 1.2 ms; 92.6% of studies met the testing guideline; 30.5% of tested limbs yielded normal results; 53.1% CTS; 5.4% ulnar neuropathy; and 11.0% nonspecific upper extremity neuropathy. DISCUSSION: This study demonstrated that point-of-service NCS by FM/PCP/IM physicians for CTS was applied to appropriate patient subpopulations, was performed in accordance with evidence-based testing parameters, and generated relevant diagnostic outcomes.

Adult↗