1,721,006 research outputs found
Relation between isometric muscle force and surface EMG in intrinsic hand muscles as function of the arm geometry
No full textEvidence exists that shoulder joint geometry influences recruitment efficiency and force-generating capacity of hand muscles [Ginanneschi, F., Del Santo, F., Dominici, F., Gelli, F., Mazzocchio, R., Rossi, A., 2005. Changes in corticomotor excitability of hand muscles in relation to static shoulder positions. Exp. Brain Res. 161 (3), 374-382; Dominici, F., Popa, T., Ginanneschi, F., Mazzocchio, R., Rossi, A., 2005. Cortico-motoneural output to intrinsic hand muscles is differentially influenced by static changes in shoulder positions. Exp. Brain Res. 164 (4), 500-504]. The present study was designed to examine the impact of changing shoulder joint position on the relation between surface EMG amplitude and isometric force production of the abductor digiti minimi muscle (ADM). EMG-force relation of ADM was examined in two shoulder positions: 30 degrees adduction (ANT) and 30 degrees abduction (POST) on the horizontal plane, i.e. under higher and lower force-generating capacity, respectively. The relation was studied over the full range isometric force (10-100% of maximum force in 10% increments, 3 s duration) by analysing root mean square (RMS), median frequency (Mf) of the power spectrum and non-linear recurrence quantification analysis (percentage of determinism: ÞT) of the surface EMG signals. We found that in POST, the slope of the RMS-force relation was significantly higher than in ANT, while its general shape (strictly linear) was preserved. Averaged Mf of the EMG power spectrum was significantly higher in POST that in ANT, while no difference in ÞT was observed between the two shoulder positions. The higher slope of the EMG-force relation in POST than in ANT is interpreted in terms of increased gain of the excitatory drive-firing rate relation. It is concluded that discharge from sensory receptors signalling shoulder position may act to regulate the gain of the excitatory drive-firing rate relation of motoneurones in order to compensate for reduced recruitment efficienc
Anomalies of ulnar nerve conduction in different carpal tunnel syndrome stages
No full textImpairment of ulnar sensory fibers at the wrist has recently been documented in moderate/severe carpal tunnel syndrome (CTS). This has been interpreted as a consequence of compressive forces transmitted to Guyon's canal by high pressure in the carpal tunnel or comorbidity between ulnar neuropathy and CTS. The main aim of the present study was to identify any ulnar nerve conduction impairment in the early stages of CTS. The relation between ulnar and median nerve conduction in all CTS severity stages was also assessed. Ulnar nerve sensory conduction at the wrist was investigated in 580 hands with CTS. Significant changes in ulnar nerve conduction were present even in the early stages of CTS. A significant, positive correlation was also found between CTS severity and conduction abnormalities of ulnar sensory fibers. These findings make the hypothesis of comorbidity weak. Based on the above results and on reports of high pressure in Guyon's canal in CTS, ulnar nerve conduction abnormalities may be caused in part by compressive forces progressively transmitted to the canal by increasing pressure in the carpal tunnel with increasing CTS severity. This does not exclude other causative factors such as subclinical traumatic damage acting on median and ulnar fiber
Arachnoid cyst and arachnoiditis following idiopathic spinal subarachnoid haemorrhage.
No full textWe describe 8 years follow-up of a case of arachnoid cyst developing after spinal subarachnoid haemorrhage. The cyst was removed by hemilaminectomy; an arachnoid cyst of the same size was again observed by MRI 2 weeks later. We suggest that conservative approach could be the best choice
Evidence of improvement in distal conduction of ulnar nerve sensory fibers after carpal tunnel release
No full textOBJECTIVE:
The aim of this study was to verify any effect of carpal tunnel release (CTR) on distal ulnar nerve conduction findings, using the database of a previous study performed to establish a protocol for CTR outcome.
METHODS:
The motor and sensory ulnar distal conduction findings of 251 consecutive hands belonging to 217 patients (175 women and 42 men; mean age, 55.6 years) with idiopathic carpal tunnel syndrome (CTS) were reanalyzed before and 1 and 6 months after CTR.
RESULTS:
Before surgery, 115 hands (45.8%) showed reduction of ulnar nerve sensory action potential (SAP) amplitude; this number was reduced significantly to 85 (33.9%) after CTR. The SAP amplitude and sensory conduction velocity values of the ulnar nerve showed significant improvement 1 month after CTR; SAP amplitude values showed further significant improvement 6 months after CTR. Patients' ages and occupations were independent predictors of reduced baseline SAP amplitudes of the ulnar nerve in CTS.
CONCLUSION:
These results demonstrate an improvement in conduction values in sensory ulnar fibers in a percentage of patients with CTS after CTR, providing further support for the conclusion that in CTS ulnar fibers may be subject to compressive forces in the Guyon canal as a consequence of high pressure in the carpal tunne
Sensory neuropathy may cause central neuronal reorganization but does not respecify perceptual quality or localization of sensation
No full textOBJECTIVES:
Functional reorganization in the somatosensory network after peripheral nerve lesions has been suspected to modify the clinical expression of symptoms. However, no conclusive evidence exists to support this notion. We addressed this question by investigating the topographic distribution of the subjective sensory report in various chronic human mononeuropathies.
METHODS:
We report the clinical results of 86 patients who were diagnosed with meralgia paresthetica, 86 patients with ulnar neuropathy at the elbow, and 203 patients with carpal tunnel syndrome.
RESULTS:
In the carpal tunnel syndrome group, 10% of the patients exhibited a spread of sensory symptoms beyond the innervation territory of the median nerve. As previously reported, this spread was contingent upon an indirect compressive lesion of the ulnar nerve at the wrist. In all of the patients who were affected with meralgia paresthetica or ulnar neuropathy at the elbow, the peripheral referral of sensation was always within the anatomic distribution of the affected nerve.
DISCUSSION:
In human neuropathies, the projected sensory symptoms are restricted to the innervation territories of the affected nerves, with no extraterritorial spread. Thus, the somatosensory localization function remains accurate, despite the central reorganization that presumably occurs after nerve injury. We conclude that reorganization of the sensory connections within the central nervous system after peripheral nerve injury in humans is a clinically silent adaptive phenomenon.
PMID: 22699137 [PubMed - indexed for MEDLINE
Changes in motor axon recruitment in the median nerve in mild carpal tunnel syndrome
No full textOBJECTIVE:
To determine whether patients with mild carpal tunnel syndrome (CTS) and conventional electrodiagnostic evidence of selective involvement of sensory conduction show changes in motor axon recruitment in the median nerve.
METHODS:
Wrist-to-abductor pollicis brevis (APB) motor axon conduction was studied by analysing the relationship between the intensity of electrical stimulation and the size of motor response (input-output curve) in 30 CTS patients with conventional electrodiagnostic evidence of selective involvement of sensory conduction. Parameters (threshold, slope and plateau) of input-output curves were compared with those obtained in 30 controls.
RESULTS:
The slope of the input-output curve of CTS patients was less steep than that of controls. For stimulus intensity above M-wave threshold (MTh), fewer motor axons were recruited in patients than controls.
CONCLUSIONS:
Motor fibres are affected in CTS when conventional electrodiagnostic tests show normal motor conduction. Altered recruitment of motor axons could mainly be due to impairment of energy-dependent processes which affect temporal dispersion of the compound volley or axonal conduction block.
SIGNIFICANCE:
In mild CTS, motor fibres are more often affected than was originally thought. The sensitivity of wrist-to-APB motor conduction studies may be increased by using submaximal stimulus intensities
Effects of gonadal steroids on the input-output relationship of the corticospinal pathway in humans
No full textMost of our knowledge about gonadal steroid effects on the nervous system come from studies of limbic structures, while virtually nothing is known about the action of these hormones on the motor system.We carried out experiments on six healthy volunteer males to determine the threshold and gain of the input–output relationship (i.e. stimulus intensity vs. response size) of the corticospinal motoneurones in relation to the transient increase of gonadal steroids induced by a single intramuscular injection of human chorionic gonadotropin (hCG). The motor cortex was excited by focal transcranial magnetic stimuli and the evoked responses from the first dorsal interosseous (FDI) were recorded with surface electromyographic electrodes. In some experiments, the threshold and recruitment curve of the soleus H reflex were determined to assess the gonadal steroid effects on spinal motoneurones. All the subjects showed a significant decrease of cortical motor threshold concomitant with a significant increase of testosterone and oestradiol plasma concentrations. By contrast, there was no significant change of the slope of the curve expressing the relationship between the intensity of magnetic stimulation and the size of the muscle response. Both the threshold and slope of the H reflex were unaffected by the gonadal steroid levels. Latencies of the maximal FDI response to cortical and cervical magnetic stimulation were also unmodified. We conclude that gonadal steroids are involved in regulating the threshold of corticospinal motoneurones in humans. Our observations confirm that the threshold and gain of corticospinal motoneurones are determined by different neural mechanisms
Ulnar nerve compression neuropathy at Guyon's canal due to crutch-walking: case report with ultrasonographic nerve imaging
No full textThis report is the first account of Guyon's syndrome after the bilateral use of forearm crutches. Crutch palsy is usually neuropraxic in nature and associated with clinical and electrophysiologic recovery of nerve function, especially if patients are instructed to not bear excessive weight on the wrist. The present case history follows this pattern. In establishing the diagnosis of a focal compression neuropathy, a combination of clinical assessment and neurophysiologic studies are typically used. This report describes the additional application of ultrasound imaging to verify the diagnosis and to track changes in the appearance of the nerve during follow-up
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