Ultrasonographic Evaluation of the Median and Sciatic Nerves in Hemiplegic Patients After Stroke

Adaptation in the spinal cord after stroke: Implications for restoring cortical control over the final common pathway

Control of voluntary movement is predicated on integration between circuits in the brain and spinal cord. Although damage is often restricted to supraspinal or spinal circuits in cases of neurological injury, both spinal motor neurons and axons linking these cells to the cortical origins of descending motor commands begin showing changes soon after the brain is injured by stroke. The concept of 'transneuronal degeneration' is not new and has been documented in histological, imaging and electrophysiological studies dating back over a century. Taken together, evidence from these studies comports more with a system attempting to survive rather than one passively surrendering to degeneration. There tends to be at least some preservation of fibres at the brainstem origin and along the spinal course of the descending white matter tracts, even in severe cases. Myelin-associated proteins are observed in the spinal cord years after stroke onset. Spinal motor neurons remain morphometrically unaltered. Skeletal muscle fibres once innervated by neurons that lose their source of trophic input receive collaterals from adjacent neurons, causing spinal motor units to consolidate and increase in size. Although some level of excitability within the distributed brain network mediating voluntary movement is needed to facilitate recovery, minimal structural connectivity between cortical and spinal motor neurons can support meaningful distal limb function. Restoring access to the final common pathway via the descending input that remains in the spinal cord therefore represents a viable target for directed plasticity, particularly in light of recent advances in rehabilitation medicine.

Sonographic peripheral nerve cross-sectional area in adults, excluding median and ulnar nerves: A systematic review and meta-analysis

INTRODUCTION/AIMS

Although electromyography remains the "gold standard" for assessing and diagnosing peripheral nerve disorders, ultrasound has emerged as a useful adjunct, providing valuable anatomic information. The objective of this study was to conduct a systematic review and meta-analysis evaluating the normative sonographic values for adult peripheral nerve cross-sectional area (CSA).

METHODS

Medline and Cochrane Library databases were systematically searched for healthy adult peripheral nerve CSA, excluding the median and ulnar nerves. Data were meta-analyzed, using a random-effects model, to calculate the mean nerve CSA and its 95% confidence interval (CI) for each nerve at a specific anatomical location (= group).

RESULTS

Thirty groups were identified and meta-analyzed, which comprised 16 from the upper extremity and 15 from the lower extremity. The tibial nerve (n = 2916 nerves) was reported most commonly, followed by the common fibular nerve (n = 2580 nerves) and the radial nerve (n = 2326 nerves). Means and 95% confidence interval (CIs) of nerve CSA for the largest number of combined nerves were: radial nerve assessed at the spiral groove (n = 1810; mean, 5.14 mm2 ; 95% CI, 4.33 to 5.96); common fibular nerve assessed at the fibular head (n = 1460; mean, 10.18 mm2 ; 95% CI, 8.91 to 11.45); and common fibular nerve assessed at the popliteal fossa (n = 1120; mean, 12.90 mm2 ; 95% CI, 9.12 to 16.68). Publication bias was suspected, but its influence on the results was minimal.

DISCUSSION

Two hundred thirty mean CSAs from 15 857 adult nerves are included in the meta-analysis. These are further categorized into 30 groups, based on anatomical location, providing a comprehensive reference for the clinician and researcher investigating adult peripheral nerve anatomy.

Impact of shoulder subluxation on peripheral nerve conduction and function of hemiplegic upper extremity in stroke patients: A retrospective, matched-pair study

Purpose: To investigate the impact of shoulder subluxation (SS) on peripheral nerve conduction and function of the hemiplegic upper extremity (HUE) in poststroke patients.Methods: Thirty post-stroke patients were selected (SS group: 15 patients, non-SS group: 15 patients, respectively). Evaluation of nerve conduction in upper limbs: the compound muscle action potential (CMAP) amplitude and latency of suprascapular, axillary, musculocutaneous, radial, median, and ulnar nerves; the motor and sensory conduction velocity and the sensory nerve action potential (SNAP) amplitude of median, ulnar, and radial nerves. The Brunnstrom stage scale was used to evaluate the HUE motor function.Results: Compared with the healthy side, the CMAP and SNAP amplitudes of tested nerves on the HUE in both groups were lower, and the CMAP latency of the suprascapular, axillary and musculocutaneous nerves on the HUE in the SS group was longer (P < 0.05). Compared with the HUE in non-SS group, the CMAP amplitude of tested nerves (except ulnar) was decreased more (P < 0.05), the motor conduction velocity of the median nerve was lower (P < 0.05), and the Brunnstrom stage of the HUE was lower in SS group (P < 0.05).Conclusions: Stroke may lead to extensive abnormal nerve conduction on the HUE, and SS may aggravate the abnormality, which may disturb the recovery of upper limb function.

Peripheral axonal excitability in hemiplegia related to subacute stroke

Background/aim

This study aims to investigate peripheral nerve excitability in patients with subacute stroke.

Materials and methods

The study was performed in 29 stroke patients within the subacute period and 29 healthy controls using QTRAC software and TRONDNF protocol. The threshold electrotonus, recovery cycle, stimulus-response, strength-duration, and current-threshold relationships were recorded.

Results

The membrane was more hyperpolarized, and excitability was decreased in the hemiplegic side. The impairment of inward rectifying channel function, degree of hyperpolarization, and decrease of excitability were directly related to the Brunnstrom stages, which were more pronounced in lower stages.

Conclusion

The lower motor neurons were affected at the level of axonal channels as a result of upper motor neuron lesions. It can be due to dying back neuropathy, homeostasis, and neurovascular regulation changes in the axonal environment, activity-dependent plastic changes, loss of drive coming from the central nervous system, or a combination of these factors.

Ultrasound and magnetic resonance imaging evaluation of the femoral and sciatic nerves. A study of healthy volunteers

Background and aims

The study describes the femoral (FN) and sciatic nerves (SN), explored using ultrasound (US) and magnetic resonance imaging (MRI). The aims of the study are: to establish US/MRI correlations and define reference values: for the anteroposterior (AP) and mediolateral (ML) diameters and cross-sectional area (CSA) of the two nerves respectively, in well-defined anatomical measuring sites; to analyze the intraobserver variation; to define the value with least variability; to determine differences between the right-left and male-female reference values.

Methods

A prospective study was carried out on 24 healthy volunteers (11 men and 13 women). MRI scans were performed using a 1.5T system. To visualize both nerves (FN and SN), a single 3D T2 weighted acquisition was performed, in the coronal plane, with a wide FOV. For ultrasonographic examinations, a Hitachi EUB-8500 ultrasound machine, equipped with a 13 MHz linear transducer was used. The measurements were performed at well-defined anatomical locations. The mean reference values of the AP, ML diameters and CSA were calculated for femoral and sciatic nerves, both on MRI and US. The correlations between the values determined by the two techniques were analyzed. The intra-observer variation was calculated by measuring the nerves at the same anatomical location at two separate time points.

Results

Wilcoxon matched-pairs signed rank test indicated a non-significant difference (p> 0.05) for the femoral and sciatic nerves, on both sides, except the femoral nerve ML diameter on MRI (p=0.014). The mean MRI and US reference values for the femoral nerve were calculated between the psoas and iliac muscles: FNAPMRI 4.533 ± 0.486, FNAPUS 4.800 ± 1.237, FNMLMRI 6.172 ± 1.203, FNMLUS 7.685 ± 3.338, FNCSAMRI 24.811 ± 3.394, FNCSAUS 26.285 ± 17.608. The mean MRI and US measurements for the sciatic nerve were determined under the buttock, at the level of the ischial tuberosity: SNAPMRI 5.500 ± 1.201, SNAPUS 5.975 ± 1.312, SNMLMRI 10.375 ± 2.272, SNMLUS 13.500 ± 1.661, SNCSAMRI 50.625 ± 15.373, SNCSAUS 53.631 ± 15.847. The MRI and US differences between right and left sides, both for the femoral and sciatic nerves were insignificant. In selected cases, Wilcoxon paired test indicated differences between subjects, according to their gender, both on MRI and US.

Conclusion

Reference values for the femoral and sciatic nerves at specific anatomical sites were identified. Side to side variation and gender related differences add to current knowledge on nerve size in young Caucasian population.

Effects of spasticity and hemiplegic posture on median nerve and carpal tunnel in stroke patients: Electrophysiological and ultrasonographic evaluation

This study aims to evaluate whether the upper extremity spasticity and hemiplegic posture have any effect on the morphology of the carpal tunnel and median nerve in stroke patients. Nerve conduction studies (NCS) were performed in 46 stroke patients and compared to those of 30 healthy controls. The cross-sectional area (CSA) of the carpal tunnel (CT) and median nerve (wrist/mid-forearm levels) was assessed by ultrasonography. The mean ages of the stroke and control group were 55.6 ± 13.5 and 56 ± 12.1 years, respectively. The median spasticity score of the forearm pronators and wrist flexor muscles was 2 (0-4) according to the Modified Ashworth Scale (MAS). The compound muscle action potential (CMAP) of the median nerve was reduced (10,093 ± 4,451 mV) when compared to non-paretic side (11,615 ± 4,397 mV) (p:0.02) and the CSA of the CT was thinner on the paretic side (1.9 ± 0.3 cm² vs 2.08 ± 0.2 cm²) (p:0.03). Pronator spasticity had no significant effect on the CSA of the median nerve and NCS at the forearm level. The CSA of the median nerve at the wrist was significantly thicker in patients with the wrist flexor spasticity graded II (MAS) and above compared to those with spasticity graded I and below (9.5 ± 1.7 mm² and 8.7 ± 1.7 mm² respectively) (p:0.03). However, the thickening of the median nerve didn't cause significant abnormalities in NCS. This study shows that in stroke patients, wrist flexor spasticity and hemiplegic wrist posture can cause explicit morphological changes in the CT and median nerve albeit normal findings on NCS.

Ultrasound measurements of the median nerve at the carpal tunnel in ambulant chronic stroke patients: comparison between paretic and non-paretic sides

[Purpose] The purpose of this study was to examine the cross-sectional area (CSA) and longitudinal sliding length (LSL) of the median nerve bilaterally in patients with ambulant chronic hemiplegia and to compare these measurements with those in healthy controls using ultrasound. [Participants and Methods] Forty patients with hemiplegia who developed a non-functional hand on the paretic side after one year or more of stroke and 25 asymptomatic controls were included. To obtain the CSA of the median nerve at the wrist in the neutral position and the LSL of the median nerve during wrist extension, the participants underwent bilateral ultrasound examination. [Results] The non-paretic side of stroke patients had the largest median nerve CSA, followed by the paretic side and then the controls; the median nerve CSA in the non-paretic side and the controls differed significantly. The CSA of the median nerve was significantly larger in the non-paretic sides of patients, evaluated at more than 5.5 years post-stroke relative to those evaluated at less than 5.5 years. The LSL of the paretic side was significantly shorter than the non-paretic side and the controls. [Conclusion] Compared to the controls, the CSA of the median nerve was enlarged in the non-paretic hand of ambulant chronic stroke patients and the LSL were identical. As such, entrapment neuropathy of the median nerve may follow long-term chronic stroke due to overuse. This study indicates the usefulness of ultrasound in the potential identification of such cases.

Sonoelastographic evaluation of the sciatic nerve in patients with unilateral lumbar disc herniation

OBJECTIVE

The aim of this study was to compare strain elastography (SE) and shear wave elastography (SWE) findings of the sciatic nerve in patients with unilateral lumbar disc herniation (LDH) and healthy control subjects.

MATERIALS AND METHODS

The study group included patients with complaints of unilateral sciatica for 3-12 months, with foraminal stenosis due to one level of LDH (L4-L5 or L5-S1). An age- and gender-matched control group was formed of healthy subjects. Evaluations were performed on both the axial and longitudinal planes from the bilateral gluteal region using a 5-9 MHz multifrequency convex probe.

RESULTS

There were 40 patients (20 male, 20 female) with a mean age of 43.1 ± 12.7 years in the study group, and 40 healthy subjects (22 male, 18 female) with a mean age of 42.9 ± 10.7 years in the control group (p > 0.05). The sciatic nerve stiffness assessed on both the axial (12.3 ± 3.7 kPA) and longitudinal (14.3 ± 3.8 kPA) planes of the involved side was significantly higher than non-involved side (axial: 6.8 ± 2.1 and longitudinal: 8.3 ± 2.3 kPA) in the patient group (p < 0.001).

CONCLUSIONS

Patients with unilateral LDH have increased stiffness of the sciatic nerve compared to healthy control subjects. Although the findings in this preliminary study show that shear wave elastography can detect a change in sciatic nerve stiffness in patients with unilateral LDH, larger studies are required to determine the clinical utility of this technique.

Investigation of the Effect of Cervical Radiculopathy on Peripheral Nerves of the Upper Extremity With High-Resolution Ultrasonography

STUDY DESIGN

Prospective, cross-sectional observational study.

OBJECTIVE

We aimed to investigate the effects of chronic cervical radiculopathy (CR) on the cross-sectional area (CSA) values of the cervical nerve roots (CNRs), median, ulnar, and radial nerves with high-resolution ultrasonography.

SUMMARY OF BACKGROUND DATA

Symptomatic nerve roots are wider than asymptomatic nerve roots due to the presence of edema. Peripheral nerves have also been shown to develop edema, fibrosis, and changes distal to the affected nerve as a result of mechanical compression. In addition according to "double-crush syndrome" hypothesis, the peripheral nerves are more sensitive to pressure, and a proximal nerve lesion makes the distal segment of the nerve more susceptible to anatomic deterioration by causing interruption in the axoplasmic conduction due to compression.

METHODS

Forty patients with chronic CR were included to the study. Both affected CNRs and the contralateral nerve roots (control group) were evaluated with high-resolution ultrasonography. Ulnar and median nerve CSA measurements were performed at four measurement points and radial nerve measurements at a single measurement point.

RESULTS

CSA measurements were statistically significantly higher at the CNR of the affected side compared to the unaffected side. There was no statistically significant difference when affected and unaffected sides were compared in terms of measurements performed from median, ulnar, and radial nerves at all measurement points.

CONCLUSION

The results of the present study indicate that the changes in the CNR caused by CR do not have any effect on the peripheral nerves. We did not find any affection in peripheral nerve CSA that might have been suggestive of double-crush syndrome in CR.

LEVEL OF EVIDENCE

2.

Dynamic secondary degeneration in the spinal cord and ventral root after a focal cerebral infarction among hypertensive rats

Cerebral infarction can cause secondary damage to nonischemic brain regions. However, whether this phenomenon will appear in central nervous system regions outside the brain remains unclear. Here we investigated pathological changes in the spinal cord and ventral root after ischemic stroke. All rats exhibited apparent neurological deficits post-MCAO, which improved gradually but could still be detected 12-weeks. Neuronal filaments in the corticospinal tract (CST) and neurons in the ventral horn were significantly declined in the contralateral cervical and lumbar enlargement 1-week post-MCAO. These decreases remained stable until 12-weeks, accompanied by progressively increased glial activation in the ventral horn. Axonal degeneration and structural derangement were evident in the contralateral cervical and lumbar ventral root 1-week post-MCAO; these changes spontaneously attenuated over time, but abnormalities could still be observed 12-weeks. The number of neural fibers in the contralateral CST and neurons in the contralateral ventral horn were positively correlated with neurological scores 12-weeks post-MCAO. Additionally, GFAP⁺cell density in the contralateral CST and ventral horn was negatively correlated with neurological scores. Our results suggest that cerebral infarction can elicit secondary degeneration in the cervical and lumbar spinal cord, as well as the projecting ventral root, which may hamper functional recovery after stroke.