Transcarpal Motor Conduction Velocity: Repeatability and Application in Carpal Tunnel Syndrome.

Background: Conduction velocity of the short segment of the median motor nerve, across wrist (transcarpal motor conduction velocity (TCMCV)), has been used to increase diagnostic yield in carpal tunnel syndrome (CTS). However, repeatability of this parameter has not been studied till date. It has not been used as an indicator of response to treatment. Using surface stimulation techniques, it is difficult to localize the sites of stimulation of transcarpal segment of median nerve in palm. As a result, small errors in measurements of TCMCV can be magnified and variability of TCMCV may occur on successive measurements. Despite this possible variation, TCMCV can be a useful tool for assessing response to therapy, if its repeatability is assessed and a cut-off value determined for a significant change in nerve conduction velocity. Purpose: In this study, it was determined whether TCMCV is repeatable. If found to be repeatable, we show a method to determine the cut-off value of the change in this parameter for it to be considered significant. Methods: Difference between values of TCMCV on successive measurements was obtained in hands of 26 controls. Repeatability of this parameter was determined in this control population following criteria of British Standards Institution. In 19 patients of CTS, treated with intracarpal steroid injection, pre-treatment and post-treatment values of TCMCV, and of symptom severity scale (SSS) and functional status scale (FSS), were obtained at 1, 2, and 3 months after treatment. Results: Repeat measurements of TCMCV were made in each hand of all controls. After applying criteria of British Standards Institution, to such recordings, TCMCV was found to be repeatable and the cut-off value for significant change determined. According to this cut-off value, 4 patients of CTS showed improvement in TCMCV, with consistent improvement in SSS and FSS. Change in TCMCV corroborated qualitatively with changes in SSS and FSS. Conclusion: Repeatability of TCMCV can be assessed by criteria of British Standards Institution and a cut-off value determined to use it as an indicator of response to treatment in CTS.

PPARα-ATGL pathway improves muscle mitochondrial metabolism: implication in aging.

Adipose triglyceride lipase (ATGL) maintains an optimum mitochondrial function putatively by generating cognate ligands for peroxisome proliferator-activated receptor α (PPARα), which, together with PPARγ coactivator-1α (PGC1α), regulate muscle mitochondrial biogenesis. However, the cross-talk between ATGL and PPARα in skeletal muscle mitochondrial metabolism and its implication in chronological aging is poorly understood. The role of ATGL in muscle mitochondrial metabolism was studied by overexpressing and depleting the gene and studying its downstream effect in cultured myotubes and in murine skeletal muscle. We found that PPARα directly induces ATGL expression during myogenesis. Overexpression of ATGL significantly enhanced while depletion of ATGL attenuated mitochondrial oxidative phosphorylation and fatty acid oxidation without alteration in mitochondrial content, and it rendered PPARα and PGC1α redundant in promoting mitochondrial oxidative function. However, ATGL did not alter PPARα-dependent lipid accumulation and insulin sensitivity. In middle-aged rats, ATGL expression was higher and correlated with PPARα expression and sustained fatty acid oxidation in oxidative soleus muscle. Fenofibrate feeding further induced ATGL expression selectively in this muscle compartment. These findings illustrate that PPARα and ATGL constitute a regulatory pathway in skeletal muscle, suggesting their role as a mitochondrial metabolic reserve.-Biswas, D., Ghosh, M., Kumar, S., Chakrabarti, P. PPARα-ATGL pathway improves muscle mitochondrial metabolism: implication in aging.

Spinal motor neuron excitability in newborns following fetal distress: sub-clinical depression revealed by soleus H-reflex.

OBJECTIVE: To explore possible spinal cord dysfunction in clinically unaffected newborns emerging from fetal distress, using H-Reflex. METHODS: This cross-sectional study comprised 48 full-term newborn infants investigated between 8h and 10 days after birth. Twenty-one (21) had fetal distress defined by late-decelerations in fetal heart rate, out of which 11 had also meconium release in utero; 5 passed meconium in utero with normal FHR patterns; and 22 normal controls had uneventful birth. All had normal birth-weight and Apgar scores. All were found normal on neurological examination, except one showing hypotonia following fetal distress. Soleus H-reflex was studied in right lower limb. RESULTS: Newborns delivered with fetal distress showed significant reduction in H-reflex excitability (H/M ratio) within 2 days of birth. Tests performed closer to the birth event revealed more severe depression. Meconium did not contribute to this effect. CONCLUSIONS: Fetal distress can lead to transient, subclinical depression of spinal motoneurons in the newborn. SIGNIFICANCE: This neonatal H-reflex study focuses on excitability of a spinal motoneuron pool rather than conduction parameters (reflecting myelination) available in literature. It reveals excitability changes missed on clinical examination of newborns apparently unaffected by intrapartum hypoxic-ischemic spells. It also draws attention towards spinal cord dysfunction in birth-hypoxia.