Presynaptic inhibition and homosynaptic depression: a comparison between lower and upper limbs in normal human subjects and patients with hemiplegia.
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Presynaptic inhibition of Ia terminals and postactivation depression at the Ia fibre-motor neuron (MN) synapses were compared in the upper and lower limbs of both sides in subjects from different populations: 49 spastic patients with hemiplegia [mainly with a lesion in the middle cerebral artery (MCA) area], two tetraplegics and 35 healthy subjects. Presynaptic inhibition was assessed using D1 inhibition of the soleus and the flexor carpi radialis (FCR) H reflexes elicited by electrical stimuli applied to the nerve supplying antagonistic muscles, and postactivation depression was explored by varying the time interval between two consecutive H reflexes. In normal subjects no right-left asymmetry was found in the amount of presynaptic Ia inhibition, homosynaptic depression or the H(max)/M(max) ratio. In the hemiplegic side of patients with MCA area lesions, the H(max)/M(max) ratio was significantly increased in the soleus but not in the FCR. Presynaptic inhibition of Ia terminals, which was significantly reduced at the cervical level on the hemiplegic side (and also, but to a lesser extent, on the unaffected side), was unchanged at the lumbar level. Homosynaptic depression was similarly reduced at the cervical and lumbar levels on the hemiplegic side but not modified on the unaffected side. It is argued that the decrease in presynaptic inhibition of Ia terminals is more a correlate of spasticity than a mechanism underlying it. The decrease in postactivation depression, which very probably contributes to the exaggeration of the stretch reflex characterizing spasticity, might be a consequence of the changes in the pattern of activation of Ia afferents and MNs following the motor impairment. (+info)
The usefulness of minimal F-wave latency and sural/radial amplitude ratio in diabetic polyneuropathy.
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The possibility of whether minimal F-wave latency and a simple ratio between the sural and superficial radial sensory response amplitudes may provide a useful electrodiagnostic test in diabetic patients was investigated in this report. To evaluate the diagnostic sensitivity of minimal F-wave latency, the Z-scores of the minimal F-wave latency, motor nerve conduction velocity (MCV), amplitude of compound muscle action potentials (CMAP), and distal latency (DL) of the median, ulnar, tibial, and peroneal nerve were compared in 37 diabetic patients. For the median, ulnar, and tibial nerves, the Z scores of the minimal F-wave latency were significantly larger than those of the MCV. In addition for all four motor nerves, the Z scores of the minimal F-wave latency were significantly larger than those for the CMAP amplitude. Furthermore, 19 subjects showing abnormal results in the standard sensory nerve conduction study had a significantly lower sural/radial amplitude ratio (SRAR), and 84% of them had an SRAR of less than 0.5. In conclusion, minimal F-wave latency and the ratio between the amplitudes of the sural and superficial radial sensory nerve action potential are sensitive measures for the detection of nerve pathology and should be considered in electrophysiologic studies of diabetic polyneuropathy. (+info)
Prosthetic ambulation in a paraplegic patient with a transfemoral amputation and radial nerve palsy.
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Great importance and caution should be placed on prosthetic fitting for a paraplegic patient with an anesthetic residual limb if functional ambulation is to be achieved. The combination of paraplegia with a transfemoral amputation and radial nerve palsy is a complex injury that makes the rehabilitation process difficult. This article describes a case of L2 paraplegia with a transfemoral amputation and radial nerve palsy on the right side. Following the rehabilitation course, the patient independently walked using a walker at indoor level with a transfemoral prosthesis with ischial containment socket, polycentric knee assembly, endoskeletal shank and multiaxis foot assembly and a knee ankle foot orthosis on the sound side. The difficulties of fitting a functional prosthesis to an insensate limb and the rehabilitation stages leading to functional ambulation are reviewed. (+info)
Occupational risk factors for radial tunnel syndrome in industrial workers.
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OBJECTIVES: The aim of the study was to evaluate both nonoccupational and occupational factors associated with radial tunnel syndrome (RTS) among industrial workers in 3 large plants. METHODS: Twenty-one cases of RTS were compared with 21 referents matched for gender, age, and plant. RTS was associated with carpal tunnel syndrome (CTS) in 9 cases. Past medical history, household activities, and ergonomic and organizational characteristics of the job were analyzed. RESULTS: The study found 3 occupational risk factors for RTS. Exertion of force of over 1 kg [odds ratio (OR) 9.1, 95% confidence interval (95% CI) 1.4-56.9] more than 10 times per hour was the main biomechanical risk factor. Prolonged static load applied to the hand during work was strongly associated with RTS (OR 5.9, 95% CI 1.2-29.9). Work posture with the elbow fully extended (0-45 degrees) was associated with RTS (OR 4.9, 95% CI 1.0-25.0). Full extension of the elbow, associated with a twisted posture of the forearm, stressed the radial nerve at the elbow. However, personal activities, household chores, and sport and leisure activities were not associated with RTS. CONCLUSIONS: The study confirms that RTS occurs in workers performing hard manual labor that requires forceful and repetitive movements involving elbow extension and forearm prosupination. (+info)
Entrapment of the sensory branch of the radial nerve (Wartenberg's syndrome): an unusual cause.
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Isolated neuropathy of the cutaneous branch of the radial nerve is a rarely recognized pathology. It was described in 1932 by Wartenberg, who suggested the name cheiralgia paraesthetica. The syndrome is described as known the entrapment of the superficial branch of the radial nerve. Many different etiologic factors for chronic nerve entrapment have been described, however our case has an unusual cause. A 52 year old man had pain and paresthesia in the area over the lateral aspect of the wrist, thumb and first web six months after Colles' fracture. The patient underwent bony spike resection after five months with ineffective conservative treatment. He has satisfied after this operation. The case was presented because of disappearing his preoperative complaints after the operation with respect to Wartenberg's syndrome constituted a rare cause of bone spike which has not been mentioned in the literature. (+info)
The effects of graded forelimb afferent volleys on acetylcholine release from cat sensorimotor cortex.
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1. The acetylcholine (ACh)-releasing system in the cerebral cortex of pentobarbital anaesthetized cats was investigated by examining the effect of graded afferent volleys in forelimb nerves on ACh release from the sensorimotor cortices contralateral and ipsilateral to the site of stimulation. 2. Cortical ACh release was determined by bio-assay of neostigmine-containing perfusates which had been in contact with the cortical surfaces for 5-10 min periods. 3. Afferent volleys, generated by stimuli that were effective in activating as many fibres of a fibre group as possible without stimulating fibres in the group with the next highest threshold for activation, were monitored from dorsal roots C7 or C8 before entering the spinal cord. 4. Stimulation of the deep (DR) and superficial (SR) radial nerves and the radial (R) nerve proximal to the junction of the DR and SR were effective in enhancing ACh release only when either group III or groups III and IV fibres were included in the afferent volley. 5. The rates of ACh release from the primary receiving area of the sensorimotor cortex contralateral to the site of stimulation did not differ from those from the same area of the ipsilateral sensorimotor cortex. 6. The pertinence of this data to the various hypotheses concerning the nature of the ACh-releasing pathways to the cerebral cortex is discussed. (+info)
Resetting of sympathetic rhythm by somatic afferents causes post-reflex coordination of sympathetic activity in rat.
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1. We have proposed previously that graded synchronous activity is produced by periodic inputs acting on weakly coupled or uncoupled oscillators influencing the discharges of a population of cutaneous vasoconstrictor sympathetic postganglionic neurones (PGNs) in anaesthetized rats. 2. Here we investigated the effects of somatic afferent (superficial radial nerve, RaN) stimulation, on the rhythmic discharges of this population. We recorded (1) at the population level from the ventral collector nerve and (2) from single PGNs focally from the caudal ventral artery of the tail. 3. Following RaN stimulation we observed an excitatory response followed by a period of reduced discharge and subsequent rhythmical discharges seemingly phase-locked to the stimulus. 4. We suggest that the rhythmical discharges following the initial excitatory response (conventional reflex) result from a resetting of sympathetic rhythm generators such that rhythmic PGN activity is synchronized transiently. We also demonstrate that a natural mechanical stimulus can produce a similar pattern of response. 5. Our results support the idea that in sympathetic control, resetting of multiple oscillators driving the rhythmic discharges of a population of PGNs may provide a mechanism for producing a sustained and coordinated response to somatic input. (+info)
Organization of climbing fibre projections to the cerebellar cortex from trigeminal cutaneous afferents and from the SI face area of the cerebral cortex in the cat.
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1. In cats anaesthetized with pentobarbitone, the projection of climbing fibres (CFs) to the cerebellar cortex from trigeminal cutaneous branches and from the face area of the sensorimotor (SI) cortex was mapped, using the technique of laminar field potential analysis. 2. The CF projections from both the trigeminal nerve and the SI face area were found to be localized to the same cerebellar folia, viz. chiefly the ipsilateral lobule HVI, with a small overlap on to the adjacent folia of lobule V and crus Ia of HVIIA. Frequently a projection from the superficial radial nerve to part or all of this area, was also found. 3. A correspondence in the distribution and amplitudes of CF potentials evoked at most points by stimulation of the trigeminal nerve and the SI cortex was found. This implies a convergence of afferents from these two sources at or before the inferior olive. 4. In more than half of the cats, a small area of the cerebellar hemisphere was found, in which contralateral as well as ipsilateral trigeminal stimulation would evoke CF potentials. Usually inputs from the superficial radial nerve and the SI cortex also converged upon this area. 5. The organization of CF projections from trigeminal and superficial radial nerve afferents to the cerebellar hemisphere was found to occur in the same 'patchy' pattern of somatotopy that has been described for spinal nerve inputs to the anterior lobe. 6. One constant factor was found in the pattern of organization of CF projections to this area from cutaneous afferent nerves. That is, only the afferents from overlapping areas of skin projected to a given recording point: no instance of CF projections from trigeminal branches innervating discontinuous skin areas was observed. (+info)