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Biomedical subjects

G Cruccu

Publications and source records attributed to G Cruccu.

At least 127 records · Page 7Linked to original sources
PubMed1985

The corneal reflex and the R2 component of the blink reflex.

A reflex contraction of the human orbicularis oculi muscles can be evoked by stimulation of either the supraorbital region ("blink reflex") or the cornea ("corneal reflex"). We found that the latency of the corneal reflex was longer, and the duration was longer than the R2 component of the blink reflex. The absolute refractory period of the R2 component of the blink reflex was longer after supraorbital than after corneal conditioning stimulation. When the R2 component of the blink reflex was habituated by repetitive stimuli, stimulation of the cornea still evoked a reflex, but supraorbital stimulation produced only a depressed R2 response. These findings suggest that the two reflexes do not have identical neural connections.

Adult↗
PubMed1985

[Corneal reflex in normal and pathological subjects].

The orbicularis oculi response can be evoked both by mechanical stimulation of the cornea (corneal reflex) and by electrical stimulation of the skin overlying the supraorbital nerve (blink reflex). Mechanical stimuli to the cornea activate A delta and C free nerve endings of the corneal mucosa. Electrical stimuli to the supraorbital nerve activate A beta, A delta and C fibers of the nerve trunk. Both reflexes present a bilateral late response, but the blink reflex shows in addition an early ipsilateral component (R1), which has never been observed with the corneal stimulation in man. We have developed a simple technique of electrical stimulation of the cornea which provides stable responses and allows precise measurements of threshold and latency of the reflex. In normal subjects, the threshold ranged from 50 to 350 microA, and the maximal stimulus that the subject could bear (tolerance level) ranged from 1000 to 2500 microA. The minimal latency to tolerance level stimuli was 39 +/- 3 msec. The latency difference between the direct responses evoked from the two opposite corneas never exceeded 8 msec and the difference between the direct and consensual responses elicited from the same cornea never exceeded 5 msec. An early ipsilateral component similar to the R1 response of the blink reflex was not observed, even with supramaximal stimulation. The electrically evoked corneal reflex was normal in 10 cases of essential trigeminal neuralgia, while the responses showed significant abnormalities in 18 subjects submitted to thermocoagulation of the Gasserian ganglion as a treatment of neuralgic pain, as well as in 2 cases of symptomatic neuralgia.(ABSTRACT TRUNCATED AT 250 WORDS)

Blinking↗
PubMed1984

Recovery cycle of the masseter inhibitory reflex in man.

The masseter inhibitory reflex from stimulation of the mental nerve has been recorded electromyographically in 10 healthy subjects. The recovery cycle of the two silent periods interrupting the tonic contraction of the masseter muscles have been studied with the paired shock technique. There was a clear dissociation between the recovery of early and late inhibition, the latter being far more affected by a preceding impulse. It is concluded that the two silent periods are mediated by separate neural nets. The differences with the recovery curves of the two components of the blink reflex are discussed.

Adult↗
PubMed1984

Computerized video screen perimetry.

A low-cost microcomputer with standard peripheral is used to examine the central visual field up to 20 degrees. The test is executed in five to eight minutes, and the map is displayed on a television screen or printed out to quantitative analysis. A very simple training is required for the technician and patient.

Computers↗
PubMed1983

Reflex and cortical responses to dental stimuli.

Tooth pulp stimulation may evoke reflex responses in the orbicularis oculi, temporal, masseter and retronuchal muscles, which may to a varying degree contaminate the cortical evoked responses. The use of repetitive stimulation reduces the amplitude of the cortical responses but avoids the onset of the majority of the muscle reflexes. The appearance of a silent period in the temporal muscle is hard to avoid and it alters the signal recorded from S1 for the first 60-70 msec. In the center-posterior leads, more protected from the EMG signal of the temporal muscle, a first negative deflection is recorded at 43 msec in 60% of subjects.

Cerebral Cortex↗
PubMed1983

The limits of tooth pulp evoked potentials for pain quantitation.

Tooth pulp evoked potentials (TPEPs) and subjective evaluation of painful dental stimuli have been recorded in healthy volunteers. The amplitude of TPEPs late components and the subjective rating have been studied in different psychological states, by the expectancy of pain with a placebo and by providing foreknowledge of stimulus timing with self-stimulation. The placebo induced a significant depression of TPEPs and pain sensation. The amplitude of TPEPs evoked by self-delivered stimuli was reduced but the subjective report remained unchanged. These results demonstrate that TPEPs are not a stable correlate of the pain perceived or of the painful input.

Dental Pulp↗
PubMed1983

The orbicularis oculi response after hemispheral damage.

The corneal and blink reflexes were evaluated in 20 normal subjects and in 30 patients with motor deficits secondary to unilateral hemispheral lesions of vascular origin. In the normal population there were no differences between subjects below and subjects above 50 years of age. In the patients the reflex evoked by electrical stimulation of the cornea of the clinically affected side was depressed in 24 out of 30 cases. The depression mainly affected the afferent branch of the circuit, which triggers both homolateral and contralateral orbicularis oculi discharge (afferent abnormality). In three cases the depression was exerted concomitantly on the efferent branch (afferent and efferent abnormality) and only in one case was it limited to the efferent branch (efferent abnormality). The late R2 component of the blink reflex was depressed in 15 out of 30 patients. The early R1 component was slightly facilitated on the affected side. The changes of the corneal reflex and of the R2 component of blink reflex were similar, but the blink reflex had a greater safety factor. The patients with an abnormal corneal reflex had more extensive damage than had the patients with normal corneal response, as shown by computer tomography, but the site of the lesion was comparable in the two groups. Conduction through the brain stem circuits mediating the orbicularis oculi response is normally under pyramidal facilitatory influences while facial motoneurons are subjected to pyramidal inhibition. After pyramidal damage the transmission of impulses in the brain stem was slowed down, ultimately to a degree that abolished the reflex. Removal of pyramidal inhibition on facial motoneurons is probably the basis of the slight facilitation of the R1 component of the blink reflex.

Adult↗
PubMed1982

[Effect of high-frequency percutaneous stimulation on experimental pain].

Ten healthy volunteers were submitted to an experimental pain test performed by electrical stimulation of one tooth, before and after 20 min high-frequency (300 Hz) electrical stimulation, for the purpose of relieving pain, delivered to the lip or to three other somatotopically non related areas. The stimulation of the lip only showed a statistically significant analgesic action. The effect was remarkable (31% of total pain relief) and of the same order of magnitude at any intensity level of the tooth stimulation, the threshold being affected too. It is concluded that a central inhibitory mechanism, activated by large afferents input, should subserve this kind of analgetic procedure.

Adult↗
PubMed1982

Analgesic activity of carprofen on human experimental dental pain.

1. The effects of an orally administered single dose of placebo, acetylsalicyclic acid (ASA) and (d,1)-6-chloro-a-methyl carbazole-2-acetic acid (carprofen) have been evaluated on an experimental pain model by electrical stimulation of dental pulp in man. 2. ASA and carprofen showed a significant analgesic action, while placebo was ineffective. 3. Analgesic activity of ASA and carprofen was similar. The two drugs were ineffective in modifying the pain threshold; on the contrary, the tolerance to the strongest painful sensation was significantly increased.

Adult↗
PubMed1981

Congenital absence of pain.

A 16-year-old boy had congenital absence of pain sensitivity and no impairment of other sensory modalities. Routine electrophysiologic investigation showed no abnormalities. The threshold and latency of electrically elicited corneal reflex and cortical potentials evoked by tooth pulp stimulation were normal, but suprathreshold electric stimulation of corneal mucosa and dental pulp, as well as electric stimulation of dorsal roots, did not elicit pain. The total CSF opioid activity was raised. However, naloxone hydrochloride administration failed to reverse the analgesia. The axon reflex to intradermal injection of histamine dihydrochloride was absent. Cutaneous nerve branches showed unspecific changes affecting part of unmyelinated axons. most of the unmyelinated as well as the myelinated axons were normal. We consider the case an example of congenital indifference to pain.

Adolescent↗
PubMed1981

Acute experimental dental pain: a technique for evaluating pain modulating procedures.

A simple method for bipolar electrical stimulation of the tooth pulp for evaluating pain modulating procedures is described. Stimulation selectivity has been studied by means of cortical evoked potentials before and after gum anaesthesia. Results obtained by constant current and constant voltage stimulation have been compared. Constant voltage stimulation has proved to be more stable in time. This technique is able to differentiate the analgesic effect of a single dose of i.v. lysine acetylsalicylate from saline. Threshold sensation was judged as painful by about half of the subjects.

Adult↗
PubMed1980

Star-like display of EEG spectral values.

A new method of displaying the results of EEG spectral analysis is described. By means of Kiviat graphs some variables of two homologous derivations are represented by coplanar vectors beginning from a common centre. A symmetrical good system appears star-shaped. Successive evaluations are superimposed on the first one. The method allows a string right-left correlation and is particularly suitable for long term evaluations.

Data Display↗
PubMed1980

Corneal reflex elicited by electrical stimulation of the human cornea.

The corneal reflex can be elicited in humans by electrical stimulation of the cornea. This method is harmless and allows precise quantification of the reflex response. In 18 patients with trigeminal lesions, the reflex was abolished or significantly altered on the diseased side in all cases. Measurement of the threshold is the most significant characteristic.

Adult↗
PubMed1979

[Multielectronic computerized EMG: technical notes on the recording and parallel off-line elaboration].

A Multielectrodic EMG analysis program is developing. The purpose is to get as short as possible the main EMG parameters (amplitude, duration, frequency) of most motor units, and to reach an estimation of the anatomical extent of single units. According to the muscle extent a variable number of electrodes are inserted crosswise the fibers. EMG signals are simultaneously recorded on a multichannel AMPEX FR1300 and then off-line processed by a 21MX HP minicomputer connected with a 5Mbytes disc drive. Some technical problems had to be solved:channel amplification adjustment to avoid any difference among preamplifiers calibration and filtering, severe hum filtering of main power that is specially strong in nultielectrodic recording systems, the need of sampling at the same Nyquist time the signals of different channels. The computer is instructed to identify the "sinchronous" units i.e. the motor units recorded from more than one channel. These motor units are detected, counted and deleted from all the channels, except the one where they show the maximum amplitude. The percentage of these sinchronous units depends upon the interelectrodic distance and their anatomical area, thus it can support an evaluation of motor unit anatomical spread.

Computers↗