Reappraisal of the F/M amplitude ratio in carpal tunnel syndrome

The F-wave/M-wave amplitude (F/M-amp) ratio has been shown to be increased in peripheral neuropathies, provided the maximum M-wave is relatively preserved. Reduced M-wave amplitudes and central facilitation of antidromically-induced reactivation of the anterior horn cells' axon hillocks (F-wave) are believed to contribute to higher F/M-amp ratios. The present study was undertaken to re-evaluate mechanisms responsible for higher F/M-amp ratios in carpal tunnel syndrome (CTS). We enrolled 232 cases affected by CTS and 108 controls. Fand M-wave amplitudes and F-wave chronodispersion were analyzed for the median and ulnar nerves. The F/M-amp ratio of the median nerve in CTS subjects with moderate-severe nerve damage was significantly higher than that of mild CTS subjects and controls. Chronodispersion of the median nerve F-wave increased with increasing CTS severity. We conclude that the relative preservation of the median nerve F-wave is due to damage to the large diameter muscle afferent fibers responsible for the monosynaptic response. Absence of the monosynaptic response makes the small motoneurons, usually inaccessible to the antidromic volley because of its collision with the orthodromic reflex volley, able to fire in the F-wave.

Distal symmetric polyneuropathy in diabetes. Differences between patients with and without neuropathic pain

AIMS

To demonstrate whether in distal symmetric polyneuropathy (DSPN) in diabetes there are differences between patients with and without neuropathic pain and whether pain is associated with demographic, clinical and electrophysiological variables.

PATIENTS AND METHODS

We prospectively enrolled 154 consecutive patients (mean age 67 years, 64% men) in an electromyography (EMG) lab. The differences were calculated between DSPN patients with (no.78) and without neuropathic pain (no.76) relating to age, sex, BMI, type, duration, treatment and complications of diabetes, HbA1c, type and duration of DSPN symptoms, DSPN clinical severity score (with Diabetic Neuropathic Index-DNI), electrophysiological findings of lower limb muscles and nerves.

RESULTS

The differences between DSPN patients with and without pain included the presence of symptoms (burning and weakness), DNI score and neurographic findings of all nerves and neurogenic EMG. But in the logistic regression models enter only the following variables: DNI score, neurogenic EMG, and among symptoms "burning".

CONCLUSIONS

The presence of pain in DSPN is associated with DSPN clinical severity, neurogenic EMG and presence of "burning- symptom but not with demographic or neurographic findings, or diabetes related variables. Therefore, the neuropathic pain in DSPN does not associate with the degree of involvement of large diameter sensory fibres or diabetes severity.

Prevalent involvement of thenar motor fibres in vineyard workers with carpal tunnel syndrome

OBJECTIVE

Carpal tunnel syndrome (CTS) has a high prevalence in agricultural workers, especially those engaged in vineyards. We postulated that vineyard CTS was electrophysiologically different from CTS of other subjects. We performed a retrospective cross-sectional electrophysiological study of two cohorts of consecutive patients with CTS, the first consisting of vineyard workers and the second, of other unselected types of workers, housewives and pensioners.

METHODS

Thirty-three vineyard workers (mean age 46.8years, 42% women) and 205 patients with other occupations (mean age 53.7years; 66% women) were enrolled. All patients underwent sensory and motor neurography of the median and ulnar nerves. Differences in demographic and electrophysiological findings between groups were calculated and multiple linear regression analysis was performed to eliminate the influence of potential confounding factors (age, sex, BMI, clinical severity of CTS) on the results of univariate difference analysis.

RESULTS

Univariate analysis showed that DML was longer and compound muscle action potential amplitude of the median nerve, recorded from the abductor pollicis brevis muscle, was smaller in vineyard workers than in the other CTS patients. These differences remained significant after adjusting the results for confounding factors.

CONCLUSIONS

The vineyard workers showed a different pattern of CTS than the other patients: thenar motor fibres were more affected, presumably due to chronic compression on the thenar branch. This suggests an association between "common" CTS and thenar mononeuropathy.

SIGNIFICANCE

Occupational physiologists should clarify the mechanisms of neuromuscular engagement in particular jobs and ergonomists design suitable working tools, because many "individual" risk factors are difficult to change, but workplace-related risk factors can be modified.

Ultrasonography before and after surgery in carpal tunnel syndrome and relationship with clinical and electrophysiological findings. A new outcome predictor?

OBJECTIVE

To measure the cross-sectional area (CSA) of the median nerve by ultrasonography (US) before and after surgery in subjects with carpal tunnel syndrome (CTS), and to verify whether the normalization of presurgical parameters can be predicted by presurgical CSA values.

PATIENTS AND METHODS

Sixty-seven consecutive cases, mean age 60.5 years, underwent surgical decompression. Before surgery, clinical and electrophysiological severity and self-assessment of symptoms (using the Boston questionnaire, BQ) were recorded. CSAs were measured proximal to the carpal tunnel inlet (CSA-I), at mid-tunnel (CSA-M), and at the tunnel outlet (CSA-O). Follow-ups were performed 1 and 6 months after surgery. Logistic regressions were performed with normalization of CSA, clinical and electrophysiological parameters as independent variables, and presurgical findings as dependent variables.

RESULTS

Before and after surgery there were correlations between CSA-I and clinical and electrophysiological severity scales. After 1 and 6 months, the clinical, electrophysiological, and BQ findings improved. CSA-I reduced at the 1-month follow-up and CSA-O increased between the first and second follow-up. Presurgical values of CSA-I could predict the normalization of its postsurgical value, normalization of the clinical severity scale, BQ, and full patient satisfaction postsurgery.

CONCLUSIONS

CSA-I is the most sensitive US measurement before surgery. The presurgical value of CSA-I is a predictor of postsurgical normalization of clinical parameters and of its own value.

A novel mechanism of action for statins against diabetes-induced oxidative stress

AIMS/HYPOTHESIS

Atorvastatin exerts beneficial vascular effects in diabetes, but the underlying mechanisms are yet to be elucidated. The aim of the present study was to determine whether Rac-1 is involved in the effect of atorvastatin on oxidative stress and vascular dysfunction.

MATERIALS AND METHODS

Using human aortic endothelial cells (HAECs) we evaluated the effect of high glucose levels on peroxide production by dihydrodichlorofluorescein and on Rac-1 activity using immunocytochemistry to detect Rac-1 translocation to the membrane. We evaluated vascular function, peroxide production by dihydroethidium and NADPH oxidase activity in vessels from atorvastatin-treated mice. Rac-1 activity was also assessed, both by immunoprecipitation of the Rac-p21-activated kinase complex and by analysis of Rac-1 translocation to the membrane. These experiments were also conducted in vessels infected with an adenoviral vector carrying a constitutively active mutant of Rac-1.

RESULTS

In HAECs exposed to high glucose levels, atorvastatin prevented oxidative stress, and this protection was associated with impaired Rac-1 activation. This effect was also observed in a murine model of diabetes mellitus. More importantly, the addition of geranylgeranyl pyrophosphate (GGPP) blocked the effects of atorvastatin in both glucose-exposed HAECs and diabetic vessels. Atorvastatin failed to afford protection against vascular abnormalities in the presence of a constitutively active mutant of Rac-1.

CONCLUSIONS/INTERPRETATION

The results of this study demonstrate that the vascular antioxidant effect of atorvastatin in diabetes is mediated through inhibition of Rac-1 via a reduction in GGPP. Thus, selective Rac-1 inhibition should be considered in the design of novel pharmacological strategies to reduce the impact of diabetes mellitus on vascular function.

A common variant of endothelial nitric oxide synthase (Glu298Asp) is an independent risk factor for carotid atherosclerosis

BACKGROUND AND PURPOSE

Endothelium-derived NO is formed from L-arginine by endothelial NO synthase (eNOS) encoded by the NOS 3 gene on chromosome 7. Because several studies have indicated that NO plays a key role in the development of the atherosclerotic process, we investigated whether common variants in the eNOS gene are associated with an increased risk of plaque on carotid arteries.

METHODS

We studied 375 subjects attending the hypertension center of our institution to be screened for arterial hypertension. The examined subjects were classified according to the presence of carotid plaques (intima-media thickness >/=1.5 mm), and 2 intronic (CA and 27-bp repeats) polymorphisms and 1 exonic (Glu298Asp) polymorphism of the eNOS gene were explored.

RESULTS

Only the Glu298Asp polymorphism of eNOS was associated with the presence of carotid plaques (P:<0.05). In particular, there was an excess of homozygotes for the Asp298 variant among subjects with carotid plaques, whereas the number of subjects who had the Glu298 allele in exon 7 of the eNOS gene was equally distributed in both study groups. Interestingly, the risk of having carotid plaques was increased approximately 3 times in subjects who were homozygotic for the Asp298 variant compared with subjects who were homozygotic for the Glu298 variant and was independent of the other common risk factors (age, blood pressure, and smoking).

CONCLUSIONS

Homozygosity for Asp298, a common variant of the eNOS gene, is an independent risk factor for carotid atherosclerosis in this study population.