Validity and reliability of nerve and muscle ultrasound

Introduction: Nerve and muscle ultrasound has been studied in several conditions, but validity and reliability have not been assessed systematically. Methods: Nerve cross‐sectional area and muscle thickness were measured ultrasonographically at several sites in 4 cadavers, which were then dissected, and actual measurements were obtained. To assess intrarater and interrater reliability, between 3 and 5 ultrasonographers, with varying experience levels, made repeated measurements on healthy volunteers. Results: Correlation coefficients for nerve and muscle validity were >0.968 (P < 0.001), and for intrarater reliability were >0.901 (P < 0.001) for still and real‐time images. Correlation coefficients for interrater reliability were more varied, but for still images they were all significant at the P < 0.001 (0.542–0.998) level, and for real‐time images they were significant at the P < 0.05 level for half the sites (0.243–0.981). Conclusion: Overall, nerve and muscle ultrasound is a valid and reliable diagnostic imaging technique. Muscle Nerve, 2013     

Oberlin transfer and partial radial to axillary nerve neurotization to repair an explosive traumatic injury to the Brachial Plexus in a child: Case report

Purpose

Explosive injuries to the pediatric brachial plexus are exceedingly rare and as such are poorly characterized in the medical literature.

Methods

Herein, we describe an 8-year-old who was struck in the neck by a piece of shrapnel and suffered multiple vascular injuries in addition to a suspected avulsion of the cervical 5 and 6 ventral rami. The patient had a complete upper brachial plexus palsy and failed to demonstrate any clinical improvement at 6-months follow-up. He was taken to the operating from for a partial ulnar to musculocutaneous nerve neurotization as well as a partial radial to axillary nerve neurotization.

Results

The patient’s motor exam improved from a Medical Research Council scale 1 to 4+ for biceps brachii and 0 to 4 deltoid function with greater than 90° of shoulder abduction.

Conclusions

This outcome supports complex neurotization techniques as viable treatment options for persistent motor deficits following an upper brachial plexus injury in older, non-infant age, children.     

In-vivo measurement of LDOPA uptake,dopamine reserve and turnover in the rat brain using [18F]FDOPA PET

Longitudinal measurements of dopamine (DA) uptake and turnover in transgenic rodents may be critical when developing disease-modifying therapies for Parkinson''s disease (PD). We demonstrate methodology for such measurements using [¹⁸F]fluoro-3,4-dihydroxyphenyl-L-alanine ([¹⁸F]FDOPA) positron emission tomography (PET). The method was applied to 6-hydroxydopamine lesioned rats, providing the first PET-derived estimates of DA turnover for this species. Control (n=4) and unilaterally lesioned (n=11) rats were imaged multiple times. Kinetic modeling was performed using extended Patlak, incorporating a k_loss term for metabolite washout, and modified Logan methods. Dopaminergic terminal loss was measured via [¹¹C]-(+)-dihydrotetrabenazine (DTBZ) PET. Clear striatal [¹⁸F]FDOPA uptake was observed. In the lesioned striatum the effective DA turnover increased, shown by a reduced effective distribution volume ratio (EDVR) for [¹⁸F]FDOPA. Effective distribution volume ratio correlated (r>0.9) with the [¹¹C]DTBZ binding potential (BP_ND). The uptake and trapping rate (k_ref) decreased after lesioning, but relatively less so than [¹¹C]DTBZ BP_ND. For normal controls, striatal estimates were k_ref=0.037±0.005 per minute, EDVR=1.07±0.22 and k_loss=0.024±0.003 per minute (30 minutes turnover half-time), with repeatability (coefficient of variation) ≤11%. [¹⁸F]fluoro-3,4-dihydroxyphenyl-L-alanine PET enables measurements of DA turnover in the rat, which is useful for developing novel therapies for PD.     

Neuropathy‐associated NaV1.7 variant I228M impairs integrity of dorsal root ganglion neuron axons

Small‐fiber neuropathy (SFN) is characterized by injury to small‐diameter peripheral nerve axons and intraepidermal nerve fibers (IENF). Although mechanisms underlying loss of IENF in SFN are poorly understood, available data suggest that it results from axonal degeneration and reduced regenerative capacity. Gain‐of‐function variants in sodium channel Na_V1.7 that increase firing frequency and spontaneous firing of dorsal root ganglion (DRG) neurons have recently been identified in ～30% of patients with idiopathic SFN. In the present study, to determine whether these channel variants can impair axonal integrity, we developed an in vitro assay of DRG neurite length, and examined the effect of 3 SFN‐associated variant Na_V1.7 channels, I228M, M932L/V991L (ML/VL), and I720K, on DRG neurites in vitro. At 3 days after culturing, DRG neurons transfected with I228M channels exhibited ～20% reduced neurite length compared to wild‐type channels; DRG neurons transfected with ML/VL and I720K variants displayed a trend toward reduced neurite length. I228M‐induced reduction in neurite length was ameliorated by the use‐dependent sodium channel blocker carbamazepine and by a blocker of reverse Na‐Ca exchange. These in vitro observations provide evidence supporting a contribution of the I228M variant Na_V1.7 channel to impaired regeneration and/or degeneration of sensory axons in idiopathic SFN, and suggest that enhanced sodium channel activity and reverse Na‐Ca exchange can contribute to a decrease in length of peripheral sensory axons. Ann Neurol 2012