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At least 757 records · Page 42Linked to original sources
PubMed1995

Blink reflex with stimulation of the mental nerve. Methodology, reference values, and some clinical vignettes.

INTRODUCTION: In order to develop an objective electrophysiological method for detecting and grading lesions in the inferior alveolar nerve (IAN) and its terminal branch, the mental nerve (MN), the normal physiology of the blink reflex (BR) with stimulation of the distribution of the MN was evaluated and reference values for the MN BR test obtained. MATERIAL AND METHODS: The BR responses to electrical stimulation of the distribution of the MN on each side were recorded in all 44 healthy adults. The onset latencies and peak-to-peak amplitudes were measured and analysed. The effects of the stimulation site, the size of the stimulating electrode, and facilitation by eye closure and mathematical task on the MN BR responses were tested. RESULTS: A small paediatric stimulating electrode was found to be efficient for dermatomal stimulation of the MN distribution. The MN BR responses consisted of an ipsilateral late component (R2i) on the side of the stimulation and a contralateral component (R2c) with similar latency. The latencies were longer and the stimulation thresholds needed to evoke a reflex response were higher with stimulation of the MN, when compared with the BRs with supraorbital nerve stimulation. Eye closure resulted in facilitation of the MN BR in the form of latency shortening, while mathematical task did not have any significant effect on the responses. In addition, the test was found useful in the diagnosis of iatrogenic IAN lesions after extraction of third molars in two patients, and after an orthognathic operation in one patient. CONCLUSION: Contrary to some previous reports, constant MN BR responses can be elicited in healthy adults, which enables further clinical application of this test.

Adolescent↗
PubMed1990

Corneal oxygenation: blink frequency as a variable in rigid contact lens wear.

Using a micropolarographic system, we measured the responses of six human corneas to nine oxygen exposure conditions: to air (continuous open-eye) with no contact lens in place, and to eight interblink intervals (1, 2, 3, 4, 5, 6, 7, and 300 s durations) with an oxygen impermeable lens in place. The corneal oxygen uptake rates immediately following each of those conditions were direct indices of tear bulk-flow exchange under a rigid contact lens as an oxygen route. Greatest efficiencies in reducing corneal oxygen demand were associated with the two highest blink frequencies examined (namely, for interblink intervals of 2 s or less). Even at those frequencies oxygen demands ranging from 4 to 6 times the open-eye, non-wearing, baseline rate for each eye typically occurred, clearly justifying the need for a supplementary oxygenation route, for example, directly through rigid contact lens materials having inherently high oxygen permeabilities.

Adult↗
PubMed2004

Blink reflex in primary lateral sclerosis.

OBJECTIVE: To investigate the underlying pathophysiology of primary lateral sclerosis (PLS) regarding possible changes in blink reflex (BR) circuit. METHODS: BR was studied in 10 patients in whom diagnosis of PLS was established by comparing them to two control groups: ten patients with amyotrophic lateral sclerosis (ALS) and 30 healthy volunteers. All patients were followed up annually for a 5 year period. A typical evoked potential study of the BR was employed. RESULTS: Significantly lower values of R(2) and R(2)' amplitude were found both in the PLS and ALS groups compared with the healthy control group. All these differences were highly significant (p<0.001). R(1) amplitude and latency, as well as R(2) and R(2)' latencies, were normal in all patients. Annually recorded follow up data revealed no significant changes in BR values for PLS patients. In contrast, for ALS patients, BR progressively disappeared following clinical impairment. CONCLUSIONS: The study suggests that BR is abnormal in PLS. It also adds some clues regarding PLS pathophysiology and can be helpful as a marker of ALS progression.

Aged↗
PubMed1995

Electromyography and recovery of the blink reflex in involuntary eyelid closure: a comparative study.

Electromyographic (EMG) activity of orbicularis oculi and levator palpebrae muscles was recorded to study the origin of involuntary eyelid closure in 33 patients. The evoked blink reflex in all patients and in 23 controls was also studied. To examine the excitability of facial motoneurons and bulbar interneurons in individual patients and to compare the results with EMG findings, R1 and R2 recovery indices were calculated in all subjects, as the average of recovery values at 0.5, 0.3, and 0.21 second interstimulus intervals. Based on EMG patterns, the patients were divided into three subclasses: EMG subclass 1, 10 patients with involuntary discharges solely in orbicularis oculi muscle; EMG subclass 2, 20 patients with involuntary discharges in orbicularis oculi and either involuntary levator palpebrae inhibition or a disturbed reciprocal innervation between orbicularis oculi and levator palpebrae; EMG subclass 3, three patients who did not have blepharospasm, but had involuntary levator palpebrae inhibition in association with a basal ganglia disease. The total patient group showed an enhanced recovery of both R1 and R2 components compared with controls. Although 30 out of 33 patients had blepharospasm (EMG subclasses 1 and 2), R1 recovery index was normal in 64% and R2 recovery index was normal in 54%. Patients with an abnormal R2 recovery index had an abnormal R1 recovery index significantly more often. All patients from EMG subclass 1 had an abnormal R2 recovery index, whereas all patients from EMG subclass 3 had normal recovery indices for both R1 and R2 responses. Seventy five per cent of the patients from EMG subclass 2 had normal recovery indices. The results provide further evidence that physiologically blepharospasm is not a homogeneous disease entity, and indicate that different pathophysiological mechanisms at the suprasegmental, or segmental level, or both are involved.

Adult↗
PubMed2000

Blink reflexes and lateral spreading in patients with synkinesia after Bell's palsy and in hemifacial spasm.

We compared various electrodiagnostical tests in patients with hemifacial spasm and in patients who developed synkinesia after Bell's palsy. We examined the evoked blink reflexes in the orbicularis oculi (o. oculi) and orbicularis oris (o. oris) muscles in 23 patients with hemifacial spasm (HFS), in 10 patients with synkinesia after Bell's palsy (BPS) and in 22 control subjects. In the patient groups, we recorded synkinesia, latency and amplitude of compound muscle action potential (CMAP) in the mental muscle after stimulation of the facial nerve and we examined electromyographic activity of the o. oculi and mental muscles synchronously. Furthermore, we studied the phenomenon of lateral spreading, also known as ephaptic transmission, between the different facial nerve branches. Patients with BPS had a prolonged R1 latency on the affected side in o. oculi and smaller mental CMAP amplitude as an indication of facial nerve damage and nerve fiber loss. This was not found in patients with HFS, who showed an increased amplitude of the R1 and R2 responses in o. oris. Patients with BPS showed only an increased R1 amplitude in o. oris. All patients had signs of synkinesia. Lateral spreading with different patterns was present in all patients with HFS and in half of the patients with BPS. Latencies of early and late responses showed no differences between HFS and BPS. In addition to alterations in facial nucleus excitability in both conditions, ectopic re-excitation of facial nerve axons in HFS may explain the differences in neurophysiological findings between HFS and BPS patients. A loss of control following synaptic stripping may also be a contributing factor.

Adolescent↗
PubMedDate not supplied

Blink reflex excitability recovery curves in patients with dysfunctions after facial nerve palsy.

The blink reflex excitability recovery curves were studied in 12 patients with postparalytic facial dysfunctions (PPFD) and 12 healthy control subjects. The inhibitory effects of the conditioning stimuli on the ipsilateral R2 and contralateral R2 responses observed in control subjects were significantly less in patients with PPFD. The enhanced recovery of the R2 responses was similar on the affected side and unaffected side in the patients. These results indicate that patients with PPFD have an increased excitability of central interneurons which mediate the R2 pathway. It is suggested that not only changes in the peripheral facial nerve but also changes in the central nervous system may contribute to the onset of PPFD.

Adult↗
PubMedDate not supplied

Determining the pathway of the blink reflex through transcutaneous electrical stimulation of the facial nerve over the stylomastoid foramen.

The afferent pathway of the late response (R2 component) of the blink reflex in response to transcutaneous electrical stimulation of the facial nerve over the stylomastoid foramen remains uncertain. The two major hypotheses regarding the afferent pathway of R2 are that it may consist of either the trigemino-facial or the facio-facial reflex. This study was performed to determine the afferent pathway of R2. Ninety-one patients with acute unilateral peripheral facial palsy and 21 controls were studied. The degree of facial nerve damage was classified into three groups: mild, moderate, and severe according to their electroneurographic value. In each group, the appearance rate, latency, and area under the curve of contralateral R2 elicited by electrical stimulation of the injured facial nerve over the stylomastoid foramen were measured and compared with those of controls. The contralateral R2 parameters did not differ between the patient groups and the controls. The results indicate that the afferent pathway of R2 is mediated not only through the facial nerve. We conclude that the auriculotemporal nerve (V3) and the great auricular nerve (C2, C3) may also contribute to the afferent pathway of R2.

Blinking↗
PubMed2005

On the waveform of the acoustic startle blink in the paradigm of prepulse inhibition - methodological and physiological aspects.

Recent studies suggest that the eye blink response to intense acoustic stimuli consists of two components that may occasionally result in waveforms with two peaks. In the present study, the prevalence, peak latencies, and peak magnitudes in responses exhibiting one or two peaks were investigated in healthy subjects in 25 pulse-alone and 25 prepulse-pulse trials using an interstimulus interval of 60 ms. Electromyographic activity was recorded simultaneously from the orbicularis oculi muscle (OOM) and from the sternocleidomastoid muscle (SCM) to explore the temporal relationship of the peaks to the generalized startle reaction. Responses in the OOM occurred with shorter onset and peak latencies than the responses in the SCM. In about 30% of pulse-alone trials, OOM responses exhibited two peaks that showed similar prepulse inhibition. These findings support the view that both components of the acoustically evoked OOM response exhibit similar plasticity in the paradigm of prepulse inhibition.

Acoustic Stimulation↗
PubMed1982

Blink reflexes elicited by electrical, acoustic and visual stimuli. I. Normal values and possible anatomical pathways.

Blink reflexes elicited by electrical stimulation of the supraorbital nerves, by monoaurally presented 1 kHz sine wave bursts of 20-ms duration, and by flashes of light presented monocularly were investigated in 32 healthy controls. Absolute latencies of the individual components and side differences were measured. An outline of possible anatomical pathways which might be involved in the transmission of these reflexes is given.

Acoustic Stimulation↗
PubMed1984

Maturation of the blink reflex in infants.

The blink reflex was elicited in 50 children from birth to 3 years of age. In the awake state, the R1 response was always obtained; R2 responses, especially contralateral ones, were more difficult to elicit under 9 months of age. R1 latency and VIIth motor nerve conduction variations were a good witness of the peripheral nervous system maturation. The influence of the different states of waking and sleeping on these reflex responses was studied. These results and some of the mechanisms that underlie these changes are discussed.

Blinking↗
PubMed1988

Blink reflex in stroke: follow-up and correlation with function and CT parameters.

Blink reflex (BR) was examined serially in patients 1, 2 and 3 months after unilateral hemispheric cerebrovascular accident and compared with functional state and CT findings of lesion extent and location. BR R2 components were depressed and correlated with lesion size. Initial walking ability was correlated with latency and amplitude of both direct and consensual R2 elicited by stimulation of the paretic side. No correlation was found between BR and arm function or the final ambulatory ability. A model suggesting a close association between BR projection-facilitating fibers and those mediating facial movements is presented.

Blinking↗
PubMed1989

Blink reflex in dyskinetic and nondyskinetic patients with Parkinson's disease.

An electrophysiological study of the blink Reflex was undertaken in 40 dyskinetic and 20 nondyskinetic patients with Parkinson's disease, who were matched for age, stage of disease, duration of illness and amount and nature of antiparkinsonian medication. We found that latencies of R2 responses (both ipsilateral and contralateral) were prolonged in the dyskinetic group compared to the nondyskinetic group. Moreover, the late response was more easily inhibited by conditioning stimulation in dyskinetic patients. This behavior of late response in dyskinetic parkinsonians may be attributed to the reinstatement of dopaminergic suppressive control over the segmental multisynaptic systems belonging to the reflex.

Adult↗
PubMed1989

Paroxysmal blinking provoked by head movements.

Since the age of 2, a 16-year-old mentally retarded epileptic girl has had sudden bursts of rapid blinking associated with upward eye deviation and triggered by active or passive head movements. Video EEG monitoring excluded an epileptic origin. Of several hypotheses (brainstem or basal ganglia dysfunction, vestibular origin, and tics), none fully explains this peculiar movement disorder, the origin of which remains unclear.

Adolescent↗
PubMed1990

Tap-induced blink reflex and central nervous system dysfunction in diabetics with hyperosmolality.

We studied the effect of hyperosmolality on the tap-induced blink reflex (TBR) in patients with diabetes. The TBR, consisting of R1 and R2 components, was either absent or delayed in patients compared to controls. The abnormalities correlated better with the degree of hyperosmolality than with the level of blood glucose. TBR was usually absent in unconscious patients with greatly elevated serum osmolality. In some patients with similar elevations in serum osmolality the R2' component was absent at a time when consciousness was preserved. Hence, TBR may be useful in monitoring CNS dysfunction in diabetics with hyperosmolality.

Adult↗
PubMed1990

Blink reflex: prognostic value in acute peripheral facial palsy.

The blink reflex (BR) has been studied during the first 2 weeks in 122 patients with Bell's palsy and Ramsay Hunt's syndrome. According to early BR (R1), the patients were divided into 3 groups: R1 less than or equal to 13 ms (16 cases); R1 greater than 13 ms (54 cases), and absent BR (52 cases). There was a remarkable tendency towards a satisfactory recovery from paralysis if BR occurred during the first 2 weeks from onset (p less than 0.001). In patients with normal BR, 93.7% had a satisfactory recovery, and in patients with delayed R1, the prognosis was still good: 86.8% had a satisfactory recovery. When the reflex was absent a bad prognosis was given in 55.8% of the patients. The BR and the severity of the lesions according to electroneurograms was tested in 111 patients and found to be significantly correlated (p less than 0.001). BR seems to be a useful index for predicting the prognosis in an early stage of the paralysis, however, more than one test should be performed at the same time to accurately establish the prognosis.

Adult↗
PubMed2005

Phase synchronization analysis of EEG during attentional blink.

The attentional blink (AB) phenomenon occurs when perceivers must report two targets embedded in a sequence of distracters; if the first target precedes the second by 200-600 msec, the second one is often missed. We investigated AB by measuring dynamic cross-lag phase synchronization for 565 electrode pairs in 40-Hz-range EEG. Phase synchrony, on average, was higher in experimental conditions, where two targets are reported, than in control conditions, where only the second target is reported. The effect occurred in electrode pairs covering the whole head. Timing of the synchrony was crucial: Brief episodes of enhanced synchrony occurred 100-500 msec before expected target onset in AB conditions where the second target was correctly reported. These results show that intrinsic brain dynamics produce anticipatory synchronization in transient assemblies of cortical areas. Enhanced levels of anticipatory synchronization occur in response to the demands of the task in conditions where the system's limited capacity is under strain.

Adolescent↗
PubMed2005

Blinking and schizotypal thinking.

Spontaneous eye blink rate (SBR) is thought to be a biological marker for cerebral dopamine (DA) activity. Accordingly, positive psychotic symptoms have been found to be associated with an increased SBR and negative psychotic symptoms with a decreased SBR. However, modulations of the DA system in patient populations also result from prior neuroleptic treatment. Here, we tested the possible relationship between SBR and positive and negative schizotypal thought. To test the direct influence of DA on SBR in general and as a function of schizotypy, half of a sample of 40 healthy men received levodopa and the other half placebo in a double-blind procedure. SBR did not differ between substance groups suggesting that a pharmacologically induced DA increase in healthy individuals does not generally increase SBR. However, in the levodopa group, increasing SBR correlated with increasing negative schizotypy scores, while no relationship was found between SBR and (1) negative schizotypy in the placebo group, or (2) positive schizotypy in either substance group. We conjecture that a pre-existing hypodopaminergic state in high negative schizotypy scorers, made these individuals susceptible to an increased DA concentration, as it has been observed in Parkinson's disease. Furthermore, the absence of any relationship in the placebo group might suggest that variations in DA concentration as a function of schizotypy are too subtle to influence SBR. Finally, the lack of any association of SBR with positive schizotypy might indicate that SBR and positive schizotypy are mediated by functionally distinct neural circuits.

Adult↗
PubMed2002

The roles of blink reflex and sympathetic skin response in multiple sclerosis diagnosis.

The neurological history and examination are important in multiple sclerosis (MS) diagnosis, but early and accurate diagnosis of MS often requires judicious use of paraclinical information. Electrophysiologic techniques have an important role in demonstrating lesions that are clincally silent but magnetic resonance imaging (MRI) is accepted as the most sensitive paraclincal test for detecting asymptomatic dissemination in space for MS patients. In order to test the sensitivity of electrophysiologic techniques in diagnosing asymptomatic MS lesions, we performed blink reflex (BR) and sympathetic skin response (SSR) studies on 13 female (mean age 39 -/+ 9 years) and 8 male (mean age 35 -/+ 14 years) patients with a diagnosis of definite MS who do not have any clinical symptoms nor signs referable to brainstem or autonomic system dysfunction. Forty three percent of patients on SSR testing and 40% of patients on BR testing demonstrated abnormal results. In countries with unfavorable economic conditions, diagnosis, especially the follow-up evaluation of MS patients, poses a major dilemma. The role of diagnostic techniques in MS diagnosis when MRI is available is an economic problem. Diagnostic evaluation adds to the cost of health expenses. We usually choose to perform MRI only at the initial diagnosis of MS and perform follow-up evaluations during remissions and exacerbations with the aid of electrophysiologic techniques. We stress the importance of electrophysiologic screenings in MS patients because they provide data that cannot be obtained through clinical evaluations only with a little cost.

Adult↗