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Biomedical subjects

R Agostino

Publications and source records attributed to R Agostino.

At least 37 records · Page 2Linked to original sources
PubMed1993

Blink reflex and the masseter inhibitory reflex in patients with dystonia.

The excitatory and inhibitory interneuronal pathways in the brainstem are tested by examining the blink reflex and the masseter inhibitory reflex, respectively. We studied the R2 component of the blink reflex and the SP2 component of the masseter inhibitory reflex and their recovery cycle in 56 patients with various forms of dystonia. In patients with cranial, cervical, and generalized dystonia, but not in patients with extracranial segmental dystonia, the recovery cycle of both reflexes was enhanced. The recovery cycle of R2 and SP2 can demonstrate subclinical changes in excitability of brainstem interneurons. The degree of enhancement of the recovery cycles did not correlate, however, with the severity of clinical facial muscle impairment. In addition, the recovery cycles correlated positively with each other, showing that excitatory as well as inhibitory interneuronal pathways in the brainstem are perturbed in dystonia. Study of the trigemino-facial and trigemino-trigeminal reflexes provides an objective tool for assessing functional abnormalities in dystonia.

Adult↗
PubMed1993

Botulinum toxin treatment in patients with focal dystonia and hemifacial spasm. A multicenter study of the Italian Movement Disorder Group.

In six Centers belonging to the Italian Movement Disorder Study Group, the efficacy of botulinum toxin treatment was evaluated in an open collaborative study in 251 patients with focal dystonia and hemifacial spasm. The percentage of functional improvement ranged from 66% to 81% in patients with blepharospasm, from 40% to 51% in patients with spasmodic torticollis and from 73% to 81% in those with hemifacial spasm. Good results were also obtained in patients with oromandibular dystonia, laryngeal dystonia and writer's cramp. Side effects were mild and transient. Local botulinum toxin injection is the first choice symptomatic treatment in focal dystonia and hemifacial spasm.

Adult↗
PubMed1992

Antagonist muscle inhibition before rapid voluntary movements of the human wrist.

When a fast voluntary movement is performed from a background condition of sustained antagonist muscle activation, there is often a decrease in antagonist muscle activity before the onset of the first agonist muscle burst (AG1) that continues until the onset of the antagonist muscle burst (ANT). We studied how controlling the peak velocity, movement size, and the magnitude of antagonist muscle loading affected antagonist muscle inhibition (AntI). AntI was more pronounced during movements with lower velocity and greater size, and when performed in the direction of heavier background loads, but its variation could not be related to any single kinematic or kinetic variable in all circumstances. When AntI was larger, ANT was smaller, suggesting that AntI does not play a role similar to the premotor silence of the agonist seen before AG1 when the movement is made from a background of sustained agonist contraction. When AntI was larger, the size of AG1 was also smaller, showing that, according to the motor task, different levels of reciprocal inhibition and coactivation occur at the onset of the movement. Both AG1 and AntI produce force in the direction of the desired movement, and the central nervous system selects an appropriate balance between the two, using AntI when possible.

Adult↗
PubMed1992

Sequential arm movements in patients with Parkinson's disease, Huntington's disease and dystonia.

We studied the performance of sequential arm movements in 14 patients with Parkinson's disease, nine patients with Huntington's disease and seven patients with arm dystonia. The results were compared with those from normal subjects. Subjects had to perform each movement of the sequence as fast as possible, stopping as briefly as possible between two successive movements. In one set of experiments, patients with Parkinson's disease drew four different geometrical patterns in a counter-clockwise direction. The patterns consisted of two, three, four and five segments of identical length. In a second set, the subjects drew a pentagon in a counter-clockwise and a clockwise direction and each side of the pentagon singly in a counter-clockwise direction. All three groups of patients were slow in executing movements and in switching from one movement to the next. Only patients with Parkinson's disease took longer to perform the segments at the end of a sequence. In other words, their movement times lengthened progressively as the sequence progressed. This phenomenon could still be recognized when the direction and position of the segments were changed (pentagon drawn in the counter-clockwise and the clockwise direction) and when the extra-time needed, mainly due to the sequential nature of the task, was considered by computing the differences between movement times obtained during drawing of the pentagon and those obtained when each segment was traced singly. This study demonstrates that sequential movements are abnormal in Parkinson's disease, Huntington's disease and dystonia and that in the performance of long motor sequences, the deficit in sequencing movements is exacerbated only in patients with Parkinson's disease.

Adult↗
PubMed1991

Spinal motor neuron excitability during the silent period after cortical stimulation.

During tonic voluntary muscle contraction, a period of electromyographic silence follows the motor evoked potential produced by transcranial stimulation of the contralateral motor cortex. We studied the silent period in the wrist flexors of 3 normal volunteers and a deafferented patient during 20% of maximal contraction. To test the excitability of the spinal motor neuron pool during the period of silence, the H-reflex was evoked in the normal subjects at different intervals after cortical stimulation. The amplitude of the H-reflex in the silent period was expressed as a percentage of the amplitude during complete muscle relaxation. The H-reflex was profoundly depressed at the beginning of the silent period (13.5-27% of the control measurement), but showed a clear tendency to recover toward the end of the silent period despite continued absence of muscle activation (71-84% of the control). Moreover, the silent period in the deafferented patient was of longer duration than can be accounted for by segmental mechanisms. These findings imply, at least in the late part of the silent period, that a reduction in the excitability of the spinal motor neuron pool plays only a minor role in determining the phenomenon and that it is probably caused by lack of cortical drive.

Adult↗
PubMed1991

Masseter inhibitory reflex in movement disorders. Huntington's chorea, Parkinson's disease, dystonia, and unilateral masticatory spasm.

Evoked by electrical stimulation of the mental nerve, the masseter inhibitory reflex consists of an early and a late silent period (SP1 and SP2), which interrupt the voluntary electromyographic (EMG) activity in the masseter muscle. We recorded the masseter inhibitory reflex and measured its latency, depth of suppression, duration and recovery cycle to paired stimuli, in patients with Huntington's chorea. Parkinson's disease, dystonia, or unilateral masticatory spasm. In patients with Huntington's chorea the reflex data and recovery cycle were normal. In patients with Parkinson's disease or dystonia, although the reflex data were normal, SP2 recovered far more rapidly than it did in control subjects. This is possibly due to hypoactivity of an inhibitory control of the polysynaptic chain of ponto-medullary interneurons that mediate SP2. In patients with unilateral masticatory spasm, both SP1 and SP2 were absent. Suppression is probably absent because this involuntary movement originates at a point along the peripheral course of the nerve.

Adolescent↗
PubMed1990

[Composites for anterior restoration. Clinical report].

The Authors, after a short description of the characteristics of composite materials used for restoration of anterior teeth, present clinical cases to demonstrate the improvement of such filling materials. The use of composite is increased even if the dentists should proceed with caution in order to obtain good and lasting results.

Adolescent↗
PubMed1990

[Clinical cases of keratinized fibromucous free autografts].

In this work the problems due to shortage of proper or adherent gum have been analyzed, further has been referred the clinical cases corresponding to the periodontal indications, which foresee the reconstruction of an insufficient superficial periodontium. Moreover have been described the surgical techniques of the free graft.

Adult↗
PubMed1990

[Restoration of a fractured incisor with recovery of the fragment].

The Authors propose the functional and estetical maintenance of a maxillary incisor, which presents a third class traumatic break, as Ellis opinion. After the positive exit, offered by the partial pulpotomy intervent, effected in order to keep on saving the vitality of the element, the same one was built again, putting on the original incisor fragment, recuperated by the restaurating operation, concerning on composed materials. After twenty-four months the Authors present the clinic control.

Adolescent↗
PubMed1990

The blink reflex in patients with idiopathic torsion dystonia.

The blink reflex and its recovery cycle were examined in 57 patients with idiopathic dystonia affecting different parts of the body. The group comprised 9 patients with generalized and 15 with segmental forms, 19 with torticollis, and 14 with focal arm dystonia. None had blepharospasm. The duration and amplitude of the R2 component of the blink reflex showed only minor changes. However, its recovery cycle to paired supraorbital nerve stimuli was abnormal in all groups of patients, except those with focal arm dystonia. These findings may be interpreted as showing abnormal control of the interneuronal networks mediating the blink reflex in patients with dystonia affecting sites other than the facial muscles. The fact that the principal changes were seen in patients with torticollis, and generalized or segmental dystonia, suggests that the extent of dystonia (rather than the severity) and, therefore, the close proximity to the cranial muscles was important in determining the extent of the abnormal interneuron function.

Arm↗
PubMed1989

The masseter inhibitory reflex is evoked by innocuous stimuli and mediated by A beta afferent fibres.

Mechanical or electrical stimulations in the area of the mouth evoke two phases of inhibition in the masseter muscle (early and late inhibitory reflex, also called masseter silent periods). The question whether the afferents of the human masseter inhibitory reflex are nociceptive or non-nociceptive has not yet been settled. We showed that an innocuous stimulus, such as a fine jet of saline directed to the lips of healthy humans, evokes an early and a late masseter inhibitory reflex, similar to those following electrical stimulation. We measured the efferent and afferent delay of the masseter early inhibitory reflex in patients submitted to intracranial stimulation of the motor and sensory trigeminal root, and found that the reflex afferents belong to the intermediately-fast conducting fibre group.

Afferent Pathways↗
PubMed1989

Blink reflex excitability recovery curves in patients with spasmodic dysphonia.

We studied 12 patients with spasmodic dysphonia (SD) and 12 healthy control subjects. The patients, who had no symptomatic involvement of the eyes, were evaluated for increased excitability of blink reflexes, which is characteristic of blepharospasm and generalized dystonia. We measured symptom severity from sound spectrograms of five sentences, including sentence production time, number of pitch phonatory breaks, and percentage of aperiodic phonation. We evoked blink reflexes by electrical and mechanical stimulation, and assessed excitability by obtaining excitability recovery curves and responses to trains of stimuli. Patients and controls differed from each other in test R2 amplitude attenuation across all intervals from 150 to 1,000 msec to electrical and mechanical stimulation. Our results indicate that patients with SD have increased excitability of blink reflexes, which suggests that the dystonia involves not only the larynx but also other anatomical structures.

Adult↗
PubMed1988

Correlation between facial involuntary movements and abnormalities of blink and corneal reflexes in Huntington's chorea.

Blink and corneal reflexes were studied in 11 patients with Huntington's chorea and the results compared with the severity of the disease. The latency of the R2 component of the blink reflex was delayed and the duration of R2 and of the corneal reflex (CR) prolonged. A greater habituation of the R2 component was found in the patients with involuntary movements in the face, and in some patients a long-lasting depression of R2 was present. A correlation was found between: (a) severity of involuntary face movements and R2 and CR latency and (b) severity of involuntary movements in the neck and latency of R2.

Adolescent↗
PubMed1987

Corneal and blink reflexes in Parkinson's disease with "on-off" fluctuations.

In 13 patients with Parkinson's disease and "on-off" fluctuations and in a control group, the electrically evoked blink (R1 and R2 component) and corneal reflexes (CR), the habituation of the glabellar reflex, and the blink rate were studied. Latency, amplitude, and recovery cycle of R1 was normal. CR latency, but not R2 latency, was significantly shorter in patients than in normal subjects. R2 recovery cycle, but not CR recovery cycle, was facilitated in "off" patients in comparison to normal subjects. CR and R2 duration was longer in "off" than in "on" patients. R2 recovery cycle became similar to that of normal subjects after fluctuation from "off" to "on" period, but CR recovery cycle varied only slightly. The habituation of the glabellar reflex and the blink rate were decreased in "off" patients. These findings indicate that the enhanced excitability of R2 is related to the central dopamine activity levels. The differences between the recovery cycles of CR and R2 may be explained with the smaller number of interneurons subserving CR than R2 circuit. The shorter latency of CR, but not of R2, both in "on" and "off" patients, may suggest that in Parkinson's disease basal ganglia exert a different control of incoming sensory input transmitted via beta and delta fibers.

Adult↗
PubMed1986

Inhibition of jaw-closing muscles by electrical stimulation of the ophthalmic division in man.

High-intensity stimulation of the supraorbital region elicits, together with a blink reflex, a reflex inhibition of the jaw-closing muscles in normal man. The response differs from the well known inhibition obtained by intra- and perioral stimulation in two main features. Firstly, it consists of a single late silent period (SP), only occasionally preceded by a short and partial decrease of the background EMG activity; secondly, the inhibitory response appears at a rather high threshold, requiring a stimulus intensity which is 4-fold the sensory perception threshold and 3-fold that required to evoke the blink reflex. Electrical and mechanical stimulation of the cornea failed to evoke a significant inhibitory reflex. The silent period and the blink reflex were similarly affected by local anaesthetic infiltration of the supraorbital skin, suggesting that the afferents subserving the two reflexes belong to the same fibre group; the higher threshold of the supraorbital inhibitory response may be explained by the need for a larger spatial summation. The considerable latency gain and relatively rapid habituation shown by the supraorbital inhibitory response imply a multisynaptic circuit, similar to that responsible for the second silent period which occurs following 'oral' stimulation. A common interneuronal net for these two reflexes is suggested by the results of interaction experiments employing combined supra- and infraorbital stimulation.

Adult↗
PubMed1986

Excitability of the corneal reflex in man.

The corneal reflex evoked by electrical stimulation of the corneal mucosa and the blink reflex evoked by electrical stimulation of the supraorbital nerve were recorded in 8 normal subjects. Habituation to repetitive stimulation and the recovery cycle to double shock were studied. The corneal reflex habituated significantly to repetitive stimulations at a rate of 0.2-1 Hz but was more resistant than the late component of the blink reflex (R2). There was a clear dissociation between the recovery of the corneal reflex and that of R2; the corneal reflex was again less affected by the proceeding impulse. These results suggest that the corneal reflex is relayed through fewer intramedullary synapses than R2.

Adult↗