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Biomedical subjects

E Favale

Publications and source records attributed to E Favale.

At least 55 records · Page 3Linked to original sources
PubMed1987

Further evidence for focal effect of right hemisphere damage on simple reaction time.

Changes of simple visual reaction time were analyzed in two groups of unilateral brain damaged patients in order to evaluate to what extent intrahemispheric localization of lesions affects performance. Possible interactions with size were avoided by selecting a localization criterion, i.e. the median section of lesion, uncorrelated with size of damage. By preliminarly establishing that the distribution of lesions in our hemispheric groups did not differ, we were enabled to confirm that intrahemispheric localization of damage has a different bearing on performance depending on side of lesion. In the right hemisphere group slower performances were generally associated with frontal damage whereas in the left hemisphere group localization did not influence the performance. The use of independent indexes for size and locus of lesion proved the existence of an interaction between these parameters in the right hemisphere group.

Brain Damage, Chronic↗
PubMed1987

Electrophysiological detection of "silent" plaques in the optic pathways.

The incidence of a delayed P100 component of the VEP after checkerboard stimulation in probable or possible multiple sclerosis (MS) without history, signs or symptoms of optic neuritis is not significantly different from that found in other neurological disorders in which the visual system is unaffected. This reduces the diagnostic validity of a delayed P100 as evidence of "silent" plaques in the optic pathway, at least in suspected MS. The use of grating increases the VEP sensitivity in the MS group, but it still leaves more than a 30% chance of error in attributing a delayed P100 to a demyelinating disorder. In this respect the discordant behaviour of checkerboard and grating responses may represent a useful clue.

Adult↗
PubMed1987

Parietal and prerolandic somatosensory evoked responses in carotid artery reversible ischemic attacks (RIA).

Somatosensory potentials evoked by median nerve stimulation were recorded bilaterally from the prerolandic and parietal scalp in 36 patients with reversible ischemic attacks in one carotid artery distribution. Responses recorded from the affected and unaffected hemisphere were compared. SEP abnormalities were observed over the affected hemisphere in 22 subjects (61.1%), irrespective of number and/or duration of episodes, and appeared selectively correlated to their clinical features. SEP studies proved to be more sensitive than conventional EEG recordings and are suitable for evaluation of the functional impairment of specific cerebral areas following transient cerebral ischemia. The occurrence of SEP abnormalities in RIA may represent an unfavourable sign, being more frequent in patients with evidence of internal carotid artery disease.

Adult↗
PubMed1986

Facilitation and inhibition of synaptic transmission in the spinal cord: an electroneurographic study in humans.

The neurographic activity evoked either by stimulation of the tibial nerve at the popliteal fossa or by percussion of the Achilles tendon has been recorded at lumbar and thigh levels, in order to find out whether conduction time, temporal dispersion and central delay of the neural volleys underlying the monosynaptic reflex (H or T) may change as a function of stimulus intensity; under facilitatory or inhibitory experimental conditions; "spontaneously", i.e. during the steady state. The reflexly evoked ventral root discharge (VRD) decreases in latency with increasing stimulus intensity up to the maximum reflex response in the absence of changes in afferent (thigh to spine) or efferent (spine to thigh) conduction times. Reduction of the central delay was greater with mechanical than electrical stimulation, probably due to the combined effect of spatial and temporal summation under the former experimental condition. The latency of the VRD related to the maximal H response was not further modified by supramaximal stimulus strengths. The Jendrassik manoeuvre caused a significant decrease in latency of the VRD, the opposite effect being observed during calf muscle vibration. A significant relationship between amplitude and latency of single VRDs could be demonstrated during the "steady state". Our data point to the existence of a positive correlation between the size of the motoneuronal pool activated by an afferent volley and speed of transmission in the reflex pathway, both during the "steady state" and under either facilitatory or inhibitory experimental conditions, provided that the test stimulus strength does not exceed the maximum reflex response (H or T). No detectable signs of peripheral dispersion of the VRD could be demonstrated, irrespective of the stimulus employed: this suggests that the axon diameters of the motoneurones contributing to the monosynaptic reflex fall within a fairly narrow distribution.

Adolescent↗
PubMed1986

Simple reaction-time changes in patients with unilateral brain damage.

Changes of simple visual reaction time were analysed in two groups of unilateral brain-damaged patients in order to evaluate to what extent properties of lesions, clinical parameters and experimental variables might influence speed of motor response. The results confirmed that brain damage, independent of its side, produces a retardation of speed. However, the two hemispheric groups differed in so far as volume of damage had a different bearing depending on side of lesion. In spite of such a difference the presence of a general interaction between size of damage and rate of progression of lesion was noted in both the hemispheres, reminiscent of Jackson's concept of 'lesion momentum'. Aphasia was related to a significant retardation of speed in left-hemisphere-diseased patients, although a specific effect of the disturbance of language could not be demonstrated. Experimental variables such as warned vs unwarned stimulation did not affect significantly the performance of brain-damaged patients.

Aged↗
PubMed1985

Assessment of motor neuron excitability in parkinsonian rigidity by the F wave.

F-wave responses from abductor pollicis brevis muscle occurred more frequently, with a larger amplitude and longer duration in rigid parkinsonian patients than in age-matched normal controls. F-wave potentiation during voluntary contraction was impaired in parkinsonian patients. These findings suggest that spinal motor neuron excitability is enhanced in rigidity. F-wave amplitude was significantly correlated to the clinical evaluation of motor disability, so that the F wave may be regarded as a useful approach to quantitative evaluation of rigidity.

Aged↗
PubMed1985

Early evoked potentials detected from the scalp of man following infraorbital nerve stimulation.

Stimulation of the infraorbital nerve evoked a short latency scalp response characterized by a large amplitude triphasic potential (W1), followed by two smaller negative deflections (W2 and W3). All these waves were presynaptic in origin (as shown by double pulse stimulation), but appeared to be generated by separate dipoles. Short distance bipolar recording showed that W1 travelled from the zygoma to the mastoid. This wave was thought to be generated in a nearby neural structure, presumably the proximal part of the maxillary nerve, the gasserian ganglion and possibly even the trigeminal root. W2 and W3 components were probably generated by the trigeminal root fibres running through the brain-stem. Their origin from slowly conducting trigeminal fibres was ruled out by their absence in short distance bipolar records along the line from the zygomatic bone to the mastoid process, and by studies on their thresholds, which were shown to be identical to those of W1. Control experiments with concurrent facial muscle recording excluded any possible contamination of the scalp response to infraorbital nerve stimulation by electromyographic activity, and demonstrated gross muscular artefacts, picked up as far-field activity by scalp electrodes, following electrical stimulation of the upper lip.

Adult↗
PubMed1985

Electroneurographic correlates of the monosynaptic reflex: experimental studies and normative data.

The neurographic concomitants of the monosynaptic reflex, evoked either by electrical stimulation of the tibial nerve at the popliteal fossa or by percussion of the Achilles tendon, have been recorded from the sciatic nerve in the lower and middle thigh. Neurographic recordings were characterised by two travelling waves (P1 and P2), respectively increasing and decreasing in latency in the proximal direction, that showed the same chronological trend of the propagated action potentials concurrently recorded in the dorsal and ventral spinal roots at the lumbar level. At variance with P2, the speed of propagation of the P1 volley was stimulus-related, being faster on mechanical than on electrical stimulation, probably because in the latter case the latency of the fastest afferents is overestimated. The P2 volley is subserved by alpha-efferent fibres in either case as suggested, inter alia, by the strict parallelism between the P2 volley and the monosynaptic reflex under appropriate experimental conditions. Simultaneous recordings of spinal root and sciatic nerve action potentials allowed the direct assessment of afferent and efferent conduction velocities, both in the proximal (that is from the middle thigh to the spinal recording site and vice-versa) and in the distal (that is from the lower to the middle thigh recording site and vice versa) segments of the reflex arc. As expected, the speed of propagation of impulses was significantly higher in the proximal than in the distal segments, as well as in the afferent than in efferent limb of the monosynaptic pathway. The P1-P2 time interval was longer on mechanical than on electrical stimulation, probably due to the increased spinal delay of the T versus the H reflex. The present study provides a reliable method for the direct assessment of alpha-efferent as well as of Ia afferent group fibres conduction velocity, provided that in the latter case mechanical stimuli be used.

Adult↗
PubMed1984

VEP changes in Parkinson's disease are stimulus dependent.

Two stimulus configurations (gratings and checkerboards) have been presented to a series of consecutive patients with the aim of exploring VEP changes in Parkinson's disease. The outcome turned out to be quite different according to the stimulus employed. Specifically, grating pattern produced a high diagnostic yield as opposite to checkerboard, which did not reveal substantial modifications of the latency of the VEP major positive peak with respect to a control group. This finding raises problems as to the characteristics of visual changes associated with Parkinson's disease.

Aged↗
PubMed1984

Short-latency somatosensory evoked potentials in degenerative and vascular dementia.

Short-latency somatosensory evoked potentials (SEPs) were recorded from 54 patients with dementia as compared to 32 age-matched controls. SEPs were generally normal in patients with senile dementia of Alzheimer type, while patients with multi-infarct dementia showed a prolonged central conduction time, an increased latency of both N13 and N20 and a reduction of the primary cortical response amplitude. These findings suggest that recording SEPs may be useful in the differential diagnosis between degenerative dementia and multi-infarct dementia.

Adult↗
PubMed1983

Further evidence for asymmetry of point localization in normals and unilateral brain damaged patients.

The properties of errors made by normals and unilateral brain damaged patients in localizing points in each half of a plane have been further investigated. A lesion of either hemisphere affects specifically the performance in the left half of the plane, where controls attain the highest degree of constancy. Consideration of the orientation of pathologic vectors may contribute to differentiation between damage of the two hemispheres.

Brain Damage, Chronic↗
PubMed1983

Surface recording of the spinal ventral root discharge in man. An experimental study.

The response evoked by stimulation of the tibial nerve was recorded by surface electrodes over the lumbosacral spine at multiple levels with both monopolar and bipolar recordings. When the stimulus strength was adjusted to elicit a maximal H reflex, bipolar recordings showed a negative-positive deflection (W1), increasing in latency in the rostral direction and classically attributed to the propagated action potentials in the dorsal roots, followed by a previously unreported positive-negative deflection (W3) showing the opposite sequence, namely, with latency decreasing in the rostral direction. A similar pattern was found in monopolar recordings in which, however, the peak corresponding in time to W3 was partially obscured by a fixed latency component (W2), particularly prominent over the upper lumbar vertebrae. When an intensity corresponding to the maximal M wave was employed, W2 showed a remarkable increase in amplitude, while both W3 and the H reflex disappeared. Several experimental techniques, either suppressing or enhancing the H response, confirmed the strict parallelism existing between this reflex and the W3 component. These findings suggest that W3 represents the reflexly evoked ventral root discharge. This was confirmed by concurrent intrathecal and surface recordings of the lumbosacral spinal evoked activity. W2 is probably generated by the postsynaptic activation of spinal neurons located in segments receiving the tibial nerve afferents, the motoneuronal contribution to this fixed latency component being slight or absent.

Adult↗
PubMed1982

Contribution of tonic vibration reflex to the evaluation and diagnosis of cerebellar disorders.

Biceps brachii tonic vibration reflexes were elicited in patients with either focal or diffuse cerebellar damage and spino-cerebellar degenerations. As compared to normal controls, tonic vibration reflex amplitude was reduced in cerebellar patients, particularly in cases with unilateral hemispheric lesion, who exhibited a clear cut tonic vibration reflex asymmetry even when clinical symptoms were mild. These reflexes were absent or very weak in patients with spino-cerebellar degenerations. Muscle vibration induced in most of the patients an enhancement of mild or latent clinical symptoms such as intention tremor, difficulty in muscle relaxation or motor incoordination.

Adolescent↗
PubMed1982

Investigations on the nervous mechanisms underlying the somatosensory cervical response in man.

The main features (amplitude, latency and shape) of the cervical activity evoked by stimulation of the median nerve, recorded throughout the cervical spine, have been concurrently investigated by monopolar, bipolar longitudinal and bipolar transverse recordings. In some subjects the derivation C7-Sn (suprasternal notch) has been employed as well. A comparative evaluation of the refractory period of each component of the cervical responses under investigation has been performed to differentiate presynaptic from postsynaptic events. Additional information has been obtained by cervical activity recorded by longitudinal and transverse bipolar derivations upon stimulation of the lower limb. It was thus demonstrated that both presynaptic and postsynaptic events were responsible for the cervical sensory evoked potential, as appearing when recorded against a cranial reference (that is the upper midfrontal region). The structures involved were the brachial plexus (N9), the cervical roots (P10 and a minor part of N11a), the dorsal columns both at caudal (N11a) and rostral (N11b) cervical levels, and the dorsal column nuclei (N13). However a contribution of the spinal segmental activity to the postsynaptic portion of the cervical response, more specifically to N13, should be considered as well, though direct evidence is still inadequate.

Adult↗
PubMed1981

Point localisation in patients with unilateral brain damage.

The ability to reproduce the position of points in a plane was examined by a copying test in a control group and in unilaterally brain damaged patients. The procedure was designed to minimise the influence of visual field defects and of spatial hemi-inattention on performance. Accuracy of of localisation and direction of errors were studied in each half of the plane. Analysis showed a greater impairment of localisation ability in the patients with right hemisphere disease; however, the performance of both hemispheric groups was characterised by a reduction of accuracy in half of the plane contralateral to the side of the lesion. Both hemispheric groups showed an abnormal direction of errors in the left half of the plane, but the two groups presented a different pattern of errors.

Analysis of Variance↗
PubMed1981

Proprioceptive modulation of somatosensory evoked potentials during active or passive finger movements in man.

The effects of active and passive finger movements on somatosensory potentials evoked by stimulation of the median nerve at the wrist or of finger I were investigated in 15 healthy volunteers. As compared to the resting condition, both active and passive movements of the stimulated hand fingers induced a marked reduction in the amplitude of the primary cerebral response (N20-P25 complex) as well as of the N17 SEP component, which is supposed to reflect the activity of the thalamo-cortical radiation. The following cerebral SEP components, within 100 ms after the stimulus, were also depressed during motor activity. Neither N11 nor N13 components of the cervical response, reflecting the activation of dorsal columns and dorsal column nuclei respectively, were modified. The SEP changes induced by active or passive movements were absent after ischaemic block of large group I afferent fibers from the hand, thus suggesting the relevance of the feedback generated by such peripheral afferents during movement. The results indicate that the activation of peripheral receptors (probably muscle spindle endings) during both active and passive finger movement would induce a gating effect at both cortical and subcortical (thalamic) level, which might modulate selectively the different sensory inputs to the cortex.

Adult↗
PubMed1981

A reassessment of sensory evoked potential parameters in multiple sclerosis: a discriminant analysis approach.

The sensitivity of the different parameters (absolute latency, interwave latency, latency asymmetry, amplitude) of both cervical and cerebral responses evoked by stimulation of the median nerve at the wrist was assessed in patients with multiple sclerosis by discriminant analysis. The peak latency of N13 or N20 SEP components or both was found to be more sensitive than their amplitude, provided that a preliminary covariation with the height of the subjects was performed. The measurement of latency asymmetry between the two sides increased the test's sensitivity, while amplitude asymmetry turned out to be of little diagnostic value. A linear discriminant function with four variates (that is mean amplitude, mean latency, latency asymmetry and height of the subject) was computed to summarise the information provided by the different parameters to give a rapid and exact method for the assessment of SEP abnormalities in multiple sclerosis patients.

Adolescent↗