Effect of weight-loss diets prior to elective surgery on postoperative outcomes in obesity: A systematic review and meta-analysis.

This systematic review investigated the effects of weight-loss diets before elective surgery on preoperative weight loss and postoperative outcomes in people with obesity. Electronic databases were searched from inception to May 2021. Inclusion criteria were prospective cohort or randomised controlled studies that compared effects of weight-loss diets to standard care on postoperative outcomes in adults with obesity awaiting surgery. Participants with cancer or undergoing bariatric surgery were excluded. Data on preoperative weight change, length of stay, postoperative complications and patient-reported outcome measures were extracted and synthesised in meta-analyses. One randomised controlled trial involving total knee arthroplasty and two that investigated general surgery were eligible that included 173 participants overall. Each study compared low-calorie diets using meal replacement formulas to usual care. There is very-low-quality evidence of a statistically significant difference favouring the intervention for preoperative weight loss (mean difference [MD] -6.67 kg, 95% confidence interval [CI] -12.09 to -1.26 kg; p = 0.02) and low-quality evidence that preoperative weight-loss diets do not reduce postoperative complications to 30 days (odds ratio [OR] 0.34, 95% CI 0.08-1.42; p = 0.14) or length of stay (MD -3.72 h, 95% CI -10.76 to 3.32; p = 0.30). From the limited data that is of low quality, weight loss diets before elective surgery do not reduce postoperative complications.

Nerve compression, membrane excitability, and symptoms of carpal tunnel syndrome.

INTRODUCTION: In this study we investigated the changes in axonal excitability and the generation of neurological symptoms in response to focal nerve compression (FNC) of the median nerve in carpal tunnel syndrome (CTS). METHODS: Sensory excitability recordings were undertaken in 11 CTS patients with FNC being applied at the wrist using a custom-designed electrode. RESULTS: During FNC, refractoriness increased significantly (62.4 ± 3.4%; P < 0.001), associated with a rapid reduction in superexcitability (16.9 ± 2.8%; P < 0.001) and sensory nerve action potential amplitude (SNAP) (32.4 ± 3.9%; P < 0.001), consistent with axonal depolarization. Associated with these changes, paresthesiae steadily increased throughout FNC, as did numbness. Reductions in SNAP amplitude and superexcitability developed more rapidly for CTS patients during FNC compared with controls, and these changes were associated with more marked symptoms. CONCLUSIONS: Axonal responses to compression are impaired in CTS. This may suggest a greater reliance on axonal membrane Na(+) /K(+) -ATPase function.

Reliability and concurrent validity of the perometer for measuring hand volume in women with and without lymphedema.

BACKGROUND: Lymphedema of hand after breast cancer treatment causes significant loss of hand function. Although there are several ways of assessing limb volume, measuring hand volume has been problematic due to technical difficulties associated with assessment of finger volumes. The aim of this study was to investigate the criterion validity and reliability of Perometer™ for measuring hand volume in woman with and without lymphedema. METHODS AND RESULTS: Hand volume of forty women with (n = 20) and without lymphedema (n = 20) was assessed twice by one rater and once by another rater using the Perometer, and once by one rater using the water volumetry method. Intra- and inter-rater reliability was determined from the intraclass correlation coefficients and Percent Close Agreement. Agreement between the Perometer and water volumetry was determined using a limit of agreement and Lin's concordance correlation. The Perometer had high intra [ICC(2,1) = 0.989 (95% CI: 0.98-0.99)] and inter-rater reliability [ICC(2,1) = 0.993 (95% CI: 0.99-1.0)]. Percent close agreement revealed that 80% of the measures were within 9 ml for inter-rater reliability and within 15 ml for intra-rater reliability. In addition, there was high concordance between hand volumes obtained with the Perometer and water volumetry method (R(c) = 0.88). However, the Perometer overestimated the volume of hand compared to water volumetry method (bias: 7.5%). CONCLUSIONS: The Perometer can be used with high reliability to measure hand volume but caution should be exercised when data are compared with measures derived from the water volumetry method.

Neurophysiological index as a biomarker for ALS progression: validity of mixed effects models.

Our objective was to evaluate the neurophysiological index (NI) as a biomarker for amyotrophic lateral sclerosis (ALS) and to assess the validity of linear mixed effects models for describing longitudinal changes. Functional assessment and nerve conduction studies were undertaken in 58 ALS patients. Neurophysiological data were collected on four occasions over 12 weeks (baseline, weeks 4, 8 and 12). The NI was calculated for the abductor digiti minimi and ulnar nerve at the wrist. NI declined at a rate of 0.04 per week (S.E. 0.006, p < 0.0001). Patients with bulbar-onset disease had 0.88 greater NI than patients with upper limb-onset disease over the follow-up period (S.E. 0.39, p = 0.03). There were no differences in the rates of decline among patients with different disease phenotypes. Rates of change in NI and functional impairment were weakly correlated (Spearman's p = 0.29, p = 0.03). Linear mixed effects models were appropriate for detailing the longitudinal changes in NI. The present findings support incorporation of NI as an outcome measure for ALS clinical trials conducted over short time periods.

Adaptation of motor function after spinal cord injury: novel insights into spinal shock.

The mechanisms underlying spinal shock have not been clearly defined. At present, clinical assessment remains the mainstay to describe progression through spinal shock following traumatic spinal cord injury. However, nerve excitability studies in combination with conventional nerve conduction and clinical assessments have the potential to investigate spinal shock at the level of the peripheral axon. Therefore, peripheral motor axon excitability was prospectively and systematically evaluated in more than 400 studies of 11 patients admitted to hospital after traumatic spinal cord injury, with cord lesions above T9 (nine cervical, two thoracic). Recordings commenced within 15 days of admission from the median nerve to abductor pollicis brevis in the upper limb and the common peroneal nerve to tibialis anterior in both lower limbs, and were continued until patient discharge from hospital. Excitability was assessed using threshold tracking techniques and recordings were compared with data from healthy controls. In addition, concurrent clinical measures of strength, serum electrolytes and nerve conduction were collected. High threshold stimulus-response relationships were apparent from the early phase of spinal shock that coincided with depolarization-like features that reached a peak on Day 16.9 (± 2.7 standard error) for the common peroneal nerve and Day 11.8 (± 2.0 standard error) for the median nerve. Overall, changes in the common peroneal nerve were of greater magnitude than for the median nerve. For both nerves, the most significant changes were in threshold electrotonus, which was 'fanned in', and during the recovery cycle superexcitability was reduced (P < 0.001). However, refractoriness was increased only for the common peroneal nerve (P < 0.05). Changes in the spinal injured cohort could not be explained on the basis of an isolated common peroneal nerve palsy. By the time patients with spinal injury were discharged from hospital between Days 68 and 215, excitability for upper and lower limbs had returned towards normative values, but not for all parameters. Electrolyte levels and results for nerve conduction studies remained within normal limits throughout the period of admission. Contrary to prevailing opinion, these data demonstrate that significant changes in peripheral motor axonal excitability occur early during spinal shock, with subsequent further deterioration in axonal function, before recovery ensues.

Changes in human sensory axonal excitability induced by focal nerve compression.

The aim of the present study was to establish the changes in nerve excitability and symptom generation associated with the application of focal nerve compression (FNC). FNC was applied at the wrist by means of a custom-designed electrode in 10 healthy subjects, and was maintained for 24 min. Symptoms of paraesthesiae and signs of numbness were recorded every 30 s. Despite apparently minimal changes in axonal threshold, FNC was associated with prolongation in latency by 14.5 +/- 2.1% (P < 0.001) and reduction in compound sensory action potential (CSAP) amplitude by 34.3 +/- 5.1% (P < 0.001), with two subjects developing conduction block. The reduction in CSAP was associated with abolition of superexcitability, and an increase in refractoriness of 295.2 +/- 55.5% (P < 0.005) and strength-duration time constant (SDTC) by 48.1 +/- 10.3% (P < 0.005), all consistent with axonal depolarization. With release of FNC, threshold rapidly increased above pre-compression levels (P < 0.01), consistent with the development of axonal hyperpolarization. Associated with these changes in axonal excitability, paraesthesiae and numbness steadily increased throughout FNC and reached a peak at the termination of FNC, followed by a gradual recovery on release of FNC. When compared to previous studies that utilised the effects of more generalised limb ischaemia, the changes in axonal excitability recorded during FNC were qualitatively and quantitatively alike, suggesting that similar biophysical mechanisms contributed to the changes observed with both manoeuvres.

INSPIRATIonAL--INSPIRAtory muscle training in amyotrophic lateral sclerosis.

Respiratory impairment, due to respiratory muscle weakness, is a major cause of morbidity and mortality in patients with amyotrophic lateral sclerosis/motor neuron disease (ALS/MND). Threshold loading may strengthen the inspiratory muscles and thereby improve patient prognosis. A phase II, double-blind, randomized-controlled trial was undertaken to determine whether a 12-week inspiratory muscle training programme attenuated the decline in respiratory function and inspiratory muscle strength in patients with ALS/MND. Nine patients were randomized to inspiratory muscle training and 10 to sham training. Primary endpoints were respiratory function (forced vital capacity, vital capacity), lung volumes and inspiratory muscle strength. Patients were assessed before, during and immediately after a 12-week training period, and at eight weeks follow-up. While improvements in inspiratory muscle strength were observed in both treatment arms, there was a non-significant increase in maximum inspiratory pressure of 6.1% in the experimental group compared to controls (standard error of mean, 6.93%; 95% confidence interval -8.58 -20.79; p=0.39). The gains in inspiratory muscle strength were partially reversed during a period of training cessation. In conclusion, inspiratory muscle training may potentially strengthen the inspiratory muscles and slow the decline in respiratory function in patients with ALS/MND.

Ischaemic sensitivity of axons in carpal tunnel syndrome.

Although carpal tunnel syndrome (CTS) is the most common human entrapment neuropathy characterized by paraesthesiae and numbness with nocturnal exacerbation, the mechanisms underlying the generation of these symptoms remain unclear. Consequently, the aim of the present study was to investigate the relationship between changes in axonal excitability and the development of neurological symptoms in response to an ischaemic insult in CTS patients. Sensory and motor excitability were measured in 10 CTS patients and compared with 10 healthy controls, with participants asked to report symptom generation and intensity during the development of limb ischaemia. To induce ischaemia, a sphygmomanometer was inflated above the elbow and maintained at 200 mmHg for 10 min. During ischaemia there were decreases in axonal threshold, with less overall reduction in CTS patients when compared with controls. Associated with these differences in threshold, both sensory (p < 0.001) and motor (p < 0.05) refractoriness increased dramatically in CTS patients. This prominent increase in refractoriness was accompanied by a significant reduction in compound sensory action potentials and compound motor action potentials amplitudes for CTS patients when compared with controls (p < 0.05). These changes in axonal excitability resulted in a higher intensity of numbness and paraesthesiae reported by CTS patients during ischaemia. The present study has established differences in the nerve excitability and symptom development during ischaemia for patients with mild and moderate CTS, and may suggest that axons in the median nerve of CTS patients have an altered functional capacity to respond to an ischaemic insult, further contributing to nocturnal exacerbation of their symptoms.

Assessing the accuracy of a combination of clinical tests for identifying carpal tunnel syndrome.

The aim of the study was to investigate whether a combination of selected provocative manoeuvres and sensory testing could improve the accuracy of clinical diagnosis of carpal tunnel syndrome (CTS). Prospective studies were undertaken in 43 of 296 consecutive patients who were referred with suspected CTS and had undergone nerve conduction studies (NCS). Responses to Phalen's test, a modified carpal compression test (MCCT), and sensory testing over the thenar eminence were assessed for each patient. For each test (Phalen's; MCCT), sensitivity (0.64; 0.14), specificity (0.75; 0.96), positive likelihood ratio (PLR) (2.54; 3.64) and negative likelihood ratio (NLR) (0.49; 0.89) were calculated. The inclusion of sensory testing did not improve sensitivity (0.55; 0.13), specificity (0.75; 0.96), PLR (2.22; 3.29) or NLR (0.60; 0.91). These data indicate that assessment of thenar sensation does not improve the diagnostic accuracy of CTS. However, a positive Phalen's test is more likely to be associated with NCS changes that are consistent with CTS.

Plasticity of lower limb motor axons after cervical cord injury.

OBJECTIVE: To assess changes in peripheral motor excitability after traumatic spinal cord injury (SCI). METHODS: Conventional nerve conduction and nerve excitability studies were longitudinally investigated in a patient diagnosed as C6 American Spinal Injury Association (ASIA) C incomplete. Recordings were undertaken from the peroneal nerve to tibialis anterior, and the median nerve to abductor pollicus brevis throughout the period of hospital admission. RESULTS: Recordings were acutely abnormal in common peroneal axons 6 days after injury. Threshold electrotonus was "fanned in"; during the recovery cycle superexcitability was abolished, and refractoriness at 2.5ms was increased (patient 152.84%; controls 37.13+/-3.83%). All parameters recovered briefly after surgical stabilization on day 9, before regressing by day 13. Excitability values recovered by day 68 when the patient was discharged ambulant as ASIA D. Recordings remained relatively unaffected in median axons throughout the admission period. CONCLUSIONS: Decentralisation after SCI had significant effects on lower limb axons, not attributable to direct trauma. Conversely, median axons remained spared. Modeling of the lower limb excitability changes suggested that interruption of energy-dependent processes contributed to the peripheral abnormalities, perhaps through involvement of upstream transynaptic processes. SIGNIFICANCE: These findings may suggest the potential for plasticity of peripheral axonal excitability in response to acute SCI.

Changes in human sensory axonal excitability induced by an ischaemic insult.

OBJECTIVE: To identify the sensitivity and the patterns of change in sensory excitability that accompany an ischaemic insult. METHODS: Sensory excitability studies were undertaken in 10 subjects (mean age 36), and monitored throughout ischaemia and following its release. Ischaemia was induced using a sphygmomanometer inflated to 200mm/Hg above the elbow. RESULTS: During ischaemia there was reduction in threshold (P<0.001), associated with a significant increase in refractoriness (106+/-6.62%; P<0.001), reduction in superexcitability (30.4+/-0.42%; P<0.001), and 'fanning in' of threshold electrotonus, all indicative of axonal depolarization. Paraesthesiae were minimal during ischaemia, but became severe on release, at which stage numbness was prominent. Late subexcitability in sensory axons was completely abolished by a relatively shorter period of ischaemia than previously observed in motor axons. CONCLUSIONS: The present study has successfully developed a template for changes in sensory axonal excitability parameters that accompany ischaemia, and established their relative sensitivity to an ischaemic change. Further, it is proposed that the inhibition of the Na+/K+ pump, in the setting of increased persistent Na+ currents and abolition of late subexcitability may underlie the development of paraesthesiae during ischaemia. SIGNIFICANCE: Changes in axonal excitability induced by ischaemia may serve as a tool to identify and interpret changes in axonal membrane potential recorded in neuropathic patients.

Riche-Cannieu anastomosis as an inherited trait.

OBJECTIVE: To explore the basis for the Riche-Cannieu anastomosis (RCA) and specifically whether this anomaly is an hereditary characteristic. METHODS: Three individuals from the same family were evaluated after initial studies in the index case indicated an RCA. Nerve conduction, needle electromyography (EMG), and axonal excitability studies of the median and ulnar nerves were undertaken in each case. RESULTS: In all subjects onset thresholds for CMAPs from abductor pollicis brevis (APB) were lower with ulnar nerve stimulation, but of similar latencies when compared with median nerve stimulation. Larger CMAP amplitudes were obtained with ulnar nerve stimulation, at lower stimulus intensities. No sensory anomalies were detected. Needle EMG confirmed dual innervation of APB by both median and ulnar nerves. Nerve excitability studies recorded from APB following ulnar nerve stimulation were within previously established normative limits for the median nerve. In the index case, no innervation anomaly was visible on magnetic resonance imaging from the forearm to hand. CONCLUSIONS: Dual innervation of APB by the median and ulnar nerves consistent with RCA was demonstrated in all 3 family members without co-existent sensory anomalies. SIGNIFICANCE: These findings infer an hereditary basis for RCA, consistent with an autosomal dominant pattern of inheritance.

Effects of forearm venous drainage on responses to the volume provocation test.

The volume provocation test (VPT) has been shown to induce a transitory increase of forearm and hand volume. Although these changes have been quantified in previous studies, the postulated mechanism underlying the VPT required further investigation. This study used a test-retest design in which the VPT was applied to 20 subjects before and during blood donation. During the standard VPT, the experimental arm was cuffed for 4 minutes at 15 mm Hg less than diastolic blood pressure, but a cannula siphoned blood from a superficial forearm vein during blood donation. Subjects rated the level of discomfort for each protocol, and reported data regarding symptom quality and location. Discomfort data during the VPT (1.95/10) was higher (p(1-tailed) < 0.005) than during blood donation (1.1/10), and subjects reported fewer volume-related symptoms during blood donation. These findings support the hypothesis that the VPT operates through a vascular mechanism, which is milder during blood donation.

Vascular factors in carpal tunnel syndrome.

An increase in hand and forearm volume was induced without hand movement in ten subjects who had carpal tunnel syndrome (CTS). A tester, unaware of sides affected by CTS, performed the Volume Provocation Test (VPT) by inflating a sphygmomanometer cuff around the upper arm to 15 mm Hg less than diastolic pressure for four minutes. Pre- and post-test volumes, intensity of discomfort, and quality and distribution of produced symptoms were recorded. The VPT induced significant increases of segment volumes bilaterally (P1 tailed <0.05), but not more on the side of strongest symptoms compared to the less affected, or asymptomatic side (P1 tailed = 0.07). Mean discomfort on the side of strongest symptoms (5.4/10) was significantly higher (P1 tailed <0.01) than on the contralateral side (2.4/10). In 44% of the affected arms, some or all of the subjects' nocturnal symptoms were reproduced after volume increase, suggesting that CTS is a vascular phenomenon in these patients.

Effects of ankle dorsiflexion on range and reliability of straight leg raising.

The effect of dorsiflexion was investigated on range of passive straight leg raising (SLR) and on inter-rater reliability with 35 patients reporting unilateral lumbar pain with or without ipsilateral leg symptoms. Ranges of SLR and SLR with dorsiflexion (SLR/DF) to onset of lumbar or leg symptoms (P1) were independently measured using a gravity goniometer by pairs of different physiotherapists at two clinics. Dorsiflexion significantly reduced SLR range by a mean of 9 degrees across both samples. Similar high inter-rater reliability was found for SLR and SLR/DF in both pairs of physiotherapists. These data show that SLR and SLR/DF are reliable procedures when measured to P1 in the clinical environment and support previous findings that dorsiflexion reduces range of SLR.