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An epileptic girl with Lennox-Gastaut syndrome had seizures triggered specifically by blinking, but not by other eye movements or by photic stimulation. Electrographic and clinical seizures were most reliably precipitated by repetitive blinking produced voluntarily on command, by reflex blinking on corneal stimulation, or by psychogenic triggers of blinking such as social stress or cognitive effort.
Gaze-evoked blinks are contractions of the orbicularis oculi (OO)-the lid closing muscle-occurring during rapid movements of the head and eyes and result from a common drive to the gaze and blink motor systems. However, blinks occurring during shifts of gaze are often suppressed when the gaze shift is made to an important visual stimulus, suggesting that the visual system can modulate the occurrence of these blinks. In head-stabilized, human subjects, we tested the hypothesis that the presence of a visual stimulus was sufficient, but not necessary, to modulate OO EMG (OOemg) activity during saccadic eye movements. Rapid, reorienting movements of the eyes (saccades) were made to visual targets that remained illuminated (visually guided trials) or were briefly flashed (memory-guided trials) at different amplitudes along the horizontal meridian. We measured OOemg activity and found that the magnitude and probability of OOemg activity occurrence was reduced when a saccade was made to the memory of the spatial location as well as to the actual visual stimulus. The reduced OOemg activity occurred only when the location of the target was previously cued. OOemg activity occurred reliably with spontaneous saccades that were made to locations with no explicit visual stimulus, generally, back to the fixation location. Thus the modulation of gaze-evoked OOemg activity does not depend on the presence of visual information per se, but rather, results from an extraretinal signal.
Eye movements associated with eyelid closure were recorded in human subjects with search coils, embedded in self-adhering scleral annuli, in a magnetic field. In contrast to classical notions, voluntary as well as reflex blinks were consistently accompanied by transient downward and nasalward movements of both eyes with amplitudes 1-5 degrees. These eye movements had a shorter duration than the upper lid movements, and the shapes of the spatial trajectories of eye and lid movements were not similar. The trajectory of the eye movements was only modestly affected by gaze eccentricities up to 15 degrees; there was a tendency for the downward component to be enhanced by looking upward, and vice versa. Restraining of the lids of one eye in the open or closed position did not significantly alter the eye movements during (attempted) blinks. Velocity-amplitude-duration relations of the down- and upward components were similar for the same eye before and after closure and for the closed eye and the contralateral unrestrained eye. The velocity-amplitude-duration characteristics of saccades were also unaffected by prolonged closure of the lids of one eye. Prolonged, voluntary closure of the lids was followed by a slow, tonic ocular deviation, which was consistently upward in half of the subjects and consistently downward in the other half. Additional horizontal components were highly variable even within subjects. In one subject the downward deviation was converted into upward deviation when lid closure was mechanically impeded. We conclude that elevation of the eye ball (Bell's phenomenon) does not occur during short blinks and only in about half of the subjects during voluntary unrestrained prolonged lid closure. Our evidence does not support the possibility that the transient eye movements during blinks are caused primarily by a mechanical interaction between the lids and the eye (or the scleral annulus). More likely, they are a secondary effect of an active cocontraction of extraocular muscles that primarily results in retraction of the eye.
PURPOSE: The aim of the present study was to evaluate the efficacy of blink reflex as a method for obtaining early diagnosis of cranial nerve involvement in alcoholic patients. MATERIALS AND METHODS: The study was conducted on 30 male alcoholics with a mean age of 43 years. They had histories of alcohol abuse for at least 6 years (mean: 25). At the time of recording, they had undergone detoxification treatment for a mean of 27 days. RESULTS: R1 (early response), R2Y (second ipsilateral response), and R2C (second contralateral response) latencies in alcoholics were prolonged relative to controls and the differences were statistically significant (p < 0.02, p < 0.001, p < 0.001, respectively). According to the defined criteria, 40% of the patients had abnormal responses, and the most common abnormality was the unilateral prolongation of R1 (13%). CONCLUSION: Finding abnormal blink reflex responses in alcoholic patients has suggested that blink reflex testing is a useful method for the evaluation of subclinical cranial nerve involvement in alcoholic patients. Blink reflex testing may be useful in detecting early changes and in the follow-up of alcoholic disorder.
PURPOSE: The reproducibility of keratometry measurements was investigated in relation to the elapsed time after blinking. METHODS: Thirty ophthalmologically healthy subjects were examined, using a standard corneal topographic instrument (17 women, 13 men, age 25.7+/-5.6 years). Photographs were taken in series of four: at 5, 15, 30, and 60 seconds after a complete blink. The series was repeated three times in each individual. The main outcome measures were the mean values, the standard deviation, and the reproducibility error of the simulated keratometric values (K1, K2), the surface regularity index (SRI), and the surface asymmetry index (SAI). RESULTS: The mean of K 1 and K 2 values did not change (p=0.684 and p=0.982); however, the measurement error increased significantly for K1 (p=0.007) and for K2 (p=0.038). The mean values of SRI changed significantly (p=0.034) during the 1-minute pause in blinking together with a non-significant change in the standard deviation (p=0.106), without elevation of the measurement error (p=0.619). The elevation of SAI with time was not significant (p=0.093). CONCLUSIONS: The break-up phenomenon of the tear film at the ocular surface induces significant deterioration of the reliability of keratometric measurements on prolonged gaze without blinking. The created error can exceed 0.6 D, which is unacceptably high in practice. Therefore care should be taken to avoid such circumstances during the examination.
Blink rate, a putative noninvasive marker of central dopamine activity, was assessed in medication-free patients with Parkinson's disease, progressive supranuclear palsy, Huntington's disease, and dystonia. The normal control rate of 24 blinks per minute was significantly higher than the rate of 12 and 4 blinks per minute recorded for patients with Parkinson's disease and progressive supranuclear palsy, respectively. The rates for patients with Huntington's disease and dystonia did not differ significantly from those of controls (36 and 26 blinks per minute, respectively).
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.
Because of an incidental observation that the blink reflex was normal in paraneoplastic sensory neuronopathy (SN) and frequently abnormal in nonparaneoplastic SN, the authors reviewed the electromyographic records of patients with SN in whom blink reflex studies were performed. The blink reflex was normal in all 17 patients with paraneoplastic SN and abnormal in 20 of 43 patients with nonparaneoplastic SN. Although it does not exclude paraneoplastic SN, an abnormal blink reflex favors a nonparaneoplastic etiology.
Blinking is a normal human phenomenon involving trigeminal and facial pathways. To gain understanding on the neurobiology of blinking, five normal subjects were investigated before and after application of transdermal capsaicin at the forehead for two weeks. No effects of topical capsaicin were detected in eye blink rates. However, when capsaicin was applied to a female subject with blepharospasm, she showed a dramatic restoration of her vision subsequent to blinking modification. Deactivation of abnormal A-to-C fibers cross talks at the trigeminal-facial pathways seems to be the most likely mechanism of such improvement.
Electrophysiologic assessment of the blink reflex test and the muscle-evoked potentials evoked by stimulation of the facial nerve were performed in 15 healthy adult Beagles before and after supraorbital (trigeminal) and facial anesthetic nerve blocks performed by lidocaine injections. Unilateral electrical stimulation of the supraorbital nerve elicited 2 ipsilateral (R1 and R2) and a contralateral (Rc) reflex muscle potential in orbicularis oculi muscles. Electrical stimulation of the facial nerve elicited 2 muscle potentials (a direct response [D] and a reflex faciofacial response [RF]) in the ipsilateral orbicularis oculi muscle. Anesthetic block of the left supraorbital nerve resulted in bilateral lack of responses upon left supraorbital nerve stimulation, but normal responses in right and left orbicularis oculi muscles upon right supraorbital stimulation. Right facial anesthetic block produced lack of responses in the right orbicularis oculi muscle regardless the side of supraorbital nerve stimulation. Results of this study demonstrate that the blink reflex can be electrically elicited and assessed in dogs. Reference values for the blink reflex responses and for the muscle potentials evoked by direct facial nerve stimulation in dogs are provided. The potential usefulness of the electrically elicited blink reflex test in the diagnosis of peripheral facial and trigeminal dysfunction in dogs was demonstrated.
This study tested the hypothesis that individual differences in generalized control perception for 43 undergraduate adults may be reflected in Spontaneous Eye Blink Rates during conversation in an interview. Control perception was assessed by means of Rotter's internal-external Locus of Control questionnaires, while Spontaneous Eye Blink Rates were computed from filmed videos of interviews consisting of a series of questions which could presumably have triggered different mental states. Pearson correlations and linear regression analyses indicated that the individual differences in Spontaneous Eye Blink Rates did not differ significantly across different questions, but that Spontaneous Eye Blink Rates measured over the entire interview correlated positively and significantly with an internal Locus of Control (r = .26). This could be interpreted as modest but corroborative evidence that a personality trait reflecting control perception may have a biological component. The possible roles of dopamine neurotransmission and frontal cortex involvement in higher cognition and Locus of Control are discussed.
Three experiments were conducted to examine eye-blink activity during the hypnotic state. The results were as follows: (1) eye-blink rate was dramatically reduced during the hypnotic as compared to the nonhypnotic state, (2) blink-rate variability between events (for example, the task and rest period) was smaller under the hypnotic than under the nonhypnotic state, (3) decrements, after induction of hypnosis, were observed in all aspects of blink-wave attributes (amplitude, duration, slope, and area). These findings can be interpreted in terms of the facilitation of motor inhibition by hypnosis.
In order to gain an early estimate of a prognosis for facial paralysis, the vertical eye movements associated with eyeblinks (Bell's phenomenon) in 39 patients with acute unilateral Bell's paralysis and Hunt's syndrome and of 21 normal subjects were recorded by electronystagmography. These data were then analysed with a small digital computer (PDP 11/34). The results were compared with electroneurography (ENoG) and nerve excitability test (NET) results and can be summarized as follows: 1. Difference in velocity and amplitude between left and right eye movement during eyeblink (called blink index), diminished in inverse proportion to any improvement of lagophthalmos. 2. All the 5 patients showing more than 80% in maximum blink index (MBI) proved to have a poor prognosis, whereas 18 of 19 patients having a MBI of 40% or less proved to have a good prognosis. The blink test was deemed to be of equal clinical significance to ENoG and NET for predicting facial paralysis. 3. The blink test does not require needle electrodes for electrical stimulus, nor any special equipment other than electronystagmography, and yet this test can provide a quantitative analysis of a degeneration profile in facial paralysis.
Evoked visual responses that were triggered by spontaneous blinking were recorded from the human subject. Although their waveform resembled that of conventionally recorded responses, two differences were noted: there was an early potential that was seen only with blink responses, and the late negative potential was smaller than that seen with conventional recording. Off- and on-components were seen in the blink responses, and these were compared with those produced by switching the stimulus off and on. The amplitudes of all of the components increased with stimulus intensity. The results suggest that blinking may play a role in vision, per se, as well as acting to protect the cornea.
We examined the accuracy of electroneuronography (ENoG) and blink reflex as prognostic indicators in four patients with bilateral facial palsy. Electrophysiological investigation consisted of the recording of ENoG amplitude and R1 amplitude of blink reflex elicited by the peripheral nerve stimulation. Examinations were performed at the first visit, after 10 days, 2, 4 and 6 weeks. ENoG amplitude was less reliable for the neurological evaluation of bilateral facial palsy, because in three cases amplitude ratio of affected side to the other side was more than 100%. R1 amplitude of blink reflex recovered satisfactorily in two cases of good outcome. In other two cases of poor outcome, R1 amplitude was absent during the examination period. These findings suggest that analysis of blink reflex provides valuable information for evaluation of the prognosis of patients with bilateral facial palsy.
In a study of spontaneous blinks, both electromyographic (EMG) activities from m. orbicularis oculi which is responsible for initiating closure of the eyelid and electro-oculogram (EOG) of vertical direction to the movement of the eyelid were measured in ten patients with Parkinson's disease and in thirty normal subjects. The aim of this study was to evaluate the generative mechanism of the spontaneous blinks by comparison of both the EMG and the EOG waveforms in the patients with Parkinson's disease and those in the normal subjects. The mean duration and the amplitude of both the EMG and the EOG were evaluated by the averaging of ten waveforms for the spontaneous blinks. The time lag between the onset of the generation of the EMG and the onset of the EOG signal was analyzed. The mean duration of the EMG and the mean amplitude of both the EMG and the EOG in the patients with Parkinson's disease were shorter and smaller than those in the normal subjects by the significant level of 1%, respectively. There was no difference of the time lag between the subject groups. These results suggest that the function of m. orbicularis oculi for the spontaneous blinks is reduced in patients with Parkinson's disease, because the motoneurones of the facial nucleus innervating the m. orbicularis oculi becomes hypoactive due to abnormal output of basal ganglia.
INTRODUCTION: Brainstem is the most frequently affected structure in neurobehçet disease. Brainstem auditory evoked responses (BAER) and magnetic resonance imaging (MRI) have been employed in early diagnosis of the disease. We present here a case of neurobehçet disease which brainstem lesion was suspected by blink reflex and corroborated by MRI. BAER were normal in this case. CLINICAL CASE: The patient was a woman, 49 years old, diagnosed from Behçet's disease. Clinical symptoms consisted of dizziness, headache, nausea, vomiting and bilateral tinnitus preceded by fever in the previous days. Neurological examination showed increased tendon reflexes and adiadochokinesis. Cerebrospinal fluid was inflammatory but aseptic. Computerised tomography and BAER were normal. Blink reflex recording showed abnormalities after the stimulation of the right supraorbital nerve in R2 component, ipsilateral and contralateral, the remainder components being normal. This finding was compatible with a lesion in the spinal tract-nucleus of the right trigeminal nerve. Cranial MRI showed several areas of high signal intensity in protuberancial calotte and spinal tract-nucleus of the trigeminal nerve. The patient improved after prednisone and chlorambucil combined therapy. Serial blink reflex studies were normal, while the patient was asymptomatic. CONCLUSION: These results indicate that determination of blink reflex together with BAER may be of help in the evaluation of a more extensive area of the brainstem in neurobehçet's disease, even in absence of trigemino-facial symptomatology. Early diagnosis is important because of neurobehçet's morbi-mortality.
PURPOSE: Most studies on blink-induced eye movements have been restricted to rotations about the horizontal and vertical axes. By additionally measuring rotation about the torsional axis, the authors investigated whether the three-dimensional rotation of the eye during the early phase of eyelid closure could be assigned to the action of a single extraocular muscle. METHODS: In five healthy human subjects, eye movements about all principal axes of rotation (horizontal, vertical, and torsional) were recorded during voluntary blinks of different durations (as short as possible, 0.83 seconds, and 1.67 seconds) in straight-ahead gaze. Original dual search coils frequently rotate about the line of sight, because the upper eyelid touches the nasally exiting wire leads. Therefore, the search coils were modified so that the wires left the silicon annulus from its inner border at 6 o'clock. RESULTS: The earliest eye movement during blinks consisted of a pulselike trajectory in a direction that was always extorsional, downward, and inward, regardless of the duration of eyelid closure. The beginning of all three movement components preceded the beginning of eyelid movement; thus, a coil artifact is unlikely. On eyelid opening, a consistent pulselike movement in the intorsional, upward, and outward direction occurred. CONCLUSIONS: During the initial phase of voluntary eyelid closure, the eyes move in a three-dimensional direction that is consistent with a pulselike innervation of the inferior rectus muscle. To obtain reliable measurement of torsional eye movements with dual search coils during blinks, modification of the annulus is indispensable.