Electrically and mechanically elicited blink reflexes in infants and children--maturation and recovery curves of blink reflex.

We studied the electrically and mechanically elicited blink reflexes in 2 groups of subjects, i.e., 237 newborn infants, 25-41 weeks of conceptional age, and 74 children, 1 month-12 years of age. In infants after 25 weeks of conceptional age we could usually induce the early response (R1) and ipsilateral late response (R2), while the contralateral late response (R2') of the electrical blink reflex became apparent after 33 weeks of conceptional age and the frequency of the appearance of R2' reached more than 60% after 38 weeks of conceptional age. After 7 months of age, R2' was usually observed. The R1 latency in full-term newborns was close to adult values, while the R2 and R2' latencies reached adult values at 7-12 years. After 1 year of age the latency of the R2 mechanical blink reflex had a tendency to be shorter than that of the electrical blink reflex. Under 35 weeks of conceptional age, the recovery curves of the blink reflex were considerably different from those of full-term infants, and premature infants showed little or no evidence of inhibition. These results indicate the absence of inhibitory interneurones in premature infants.     

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)     

Intracranial stimulation of the trigeminal nerve in man. II. Reflex responses.

The reflex responses evoked by direct electrical stimulation of the intracranial portion of the trigeminal nerve have been studied in 16 subjects undergoing percutaneous retrogasserian thermocoagulation for the treatment of trigeminal neuralgia affecting the second or third division. In the obicularis oculi muscle, early and late responses similar to the R1 and R2 components of the blink reflex were recorded. The former could be evoked only by stimulation of the second division and its latency was consistent with intermediately fast afferents. A late reflex (50-70 ms) was occasionally recorded from the anterior belly of the digastric muscle. The response was sometimes followed by a later activity and showed the features of a polysynaptic reflex. No response was obtained in the jaw elevators when fully relaxed. With the subject voluntarily clenching his teeth, both an early "H-like" response and two silent periods in the background EMG were obtained. The second silent period was similar in the muscles ipsi- and contralateral to intracranial stimulation, while the first silent period was longer in the ipsilateral muscles. Possible mechanisms contributing to the inhibition following stimulation of the mixed portion of the nerve are discussed.     

Development of the blink reflex during the 1st 3 years of a child's life

The blink reflex was elicited in 42 awake and quiet children from birth to 3 years of age. The R1 ipsilateral reflex response was always recorded. Its latency decreased significantly during the first 6 months of life whereas the VIIth nerve motor conduction velocity increased markedly; its threshold stimulus was lower in children after 1 year of age. R2 responses, especially contralateral ones, were sometimes absent in infants under 9 months of age; beyond that age, they were constant and bilateral. The ipsilateral R2 latency response diminished during the first 6 months of life, and the R2 reflex threshold became lower in infants above 1 year of age. When elicited after crying, in 22 children, the reflex components were facilitated; R1 response occasionally appeared bilaterally, its amplitude increased and its threshold was lower. During REM sleep, in 12 children, the reflex responses were similar to those recorded during quiet wakefulness. On the contrary, non-REM sleep recorded in 12 children markedly depressed the reflex responses; this inhibition was more pronounced for R2 responses.     

Blink reflex in hemiplegia

Data about the influence of hemispheric lesions on the blink reflex are conflicting. 21 hemiplegic patients and 11 control subjects were investigated. The duration, latency and electric area of electrically evoked blink reflex responses were evaluated by common electromyographic techniques. A depression of the ipsilateral and the consensual late response after stimulation of the paretic side was the most evident finding. However, also a certain increase of the early response and a depression of the late response of the paretic side independent of the side of stimulation emerged. Concerning the parameters taken into account, the evaluation of the latency period seems to be the most significant and reliable. Determination of the electric area provides additional useful data which, however, may easily lead to mistakes.     

Unusual blink reflex with four components in a patient with periodic ataxia

Summary Characteristic findings in blink reflex are reported in a 55-year-old female with periodic ataxia. The blink reflexes on the side ipsilateral to the stimulation consisted of four components with latencies of 11, 21, 35 and 47 ms, instead of the usual two components seen in normal subjects. On the contralateral side, the last three components were also present. The second component was different from the normal R2 response in that its latency was shorter than normal and it did not habituate by stimulation at a rate of 10 Hz. In addition, it was more affected by diazepam than the third or fourth components. It is considered that R2 may have consisted of three components and that a shorter latency of the second component could be explained by facilitation.     

Blink reflex in young children with medullary kink in Chiari malformation.

We studied the blink reflex (especially the late components ipsi- and contralateral to stimulation site, R2 and R2') in 17 patients under 6 years of age; 12 with Chiari malformation, 1 with Dandy-Walker syndrome and 4 with brainstem tumor. We investigated the correlation between the R2 or R2' and neuro-image findings. Out of various features of the brainstem lesion revealed by MRI or CT examinations, the medullary kink characteristic in Chiari malformation was most responsible for abnormality of R2 and R2'. In addition, the fact that the disturbance of R2 and R2' in patients with Chiari malformation was more apparent in younger children than older ones confirms the intrinsic vulnerability of the blink reflex in the younger age groups as noted in normal children.     

BLINK REFLEX IN HUNTINGTON''S CHOREA AND PARKINSON''S DISEASE

The electrically-evoked late response (R2) of the blink reflex has been determined in 8 well-documented cases of Huntington's chorea and in 19 Parkinsonian patients. The results obtained from the two groups are compared with those from 10 normal subjects. A statistically significant difference of some components of the blink reflex was obtained when the three groups were compared. In both pathological conditions, the habituation index, latency and differential latency can be considered to represent the opposite extremes from the same scale, providing further evidence of the neurophysiological antagonism between the two disease states. The blink reflex pattern in Huntington's chorea probably reflects a diminished brain-stem interneurone basal activity through an over-inhibition of dopaminergic receptors in the striatum. The electrophysiological analysis of the blink reflex in incipient Huntington's chorea can provide an objective diagnostic assessment. It might be an effective method of detection for dopaminergic-activated carriers asking for genetic counseling.     

Blink reflex in 57 parkinsonian patients with correlation between the clinical and electrophysiological parameters

An electrophysiological study of the blink reflex was undertaken in 25 control subjects and in 57 patients with Parkinson's disease. An increase in the ipsilateral and contralateral late response was the most evident finding. The excitability cycle of recovery of the R2 component of the blink reflex after a prior conditioning shock was enhanced in the patients. A statistically significant correlation was established between the increase in the late response and the severity of akinesia and rigidity.     

Further evidence for a central reorganisation of synaptic connectivity in patients with hypoglossal-facial anastomosis in man

In normal subjects, electrical stimulation of trigeminal mucosal afferents (lingual nerve - V3) can elicit a short latency (12.5+/-0. 3 ms; mean+/-S.D.) reflex response in the ipsilateral genioglossus muscle (Maisonobe et al., Reflexes elicited from cutaneous and mucosal trigeminal afferents in normal human subjects. Brain Res. 1998;810:220-228). In the present study on patients with hypoglossal-facial (XII-VII) nerve anastomoses, we were able to record similar R1-type blink reflex responses in the orbicularis oculi muscles, following stimulation of either supraorbital nerve (V1) or lingual nerve (V3) afferents. However, these responses were not present in normal control subjects. Voluntary swallowing movements produced clear-cut facilitations of the R1 blink reflex response elicited by stimulation of V1 afferents. In a conditioning-test procedure with a variable inter-stimulus interval, the R1 blink reflex response elicited by supraorbital nerve stimulation was facilitated by an ipsilateral mucosal conditioning stimulus in the V3 region. This facilitatory effect was maximal when the two stimuli (conditioning and test) were applied simultaneously. This effect was not observed on the R1 component of the blink reflex in the normal control subjects. These data strongly suggest that in patients with XII-VII anastomoses, but not in normal subjects, both cutaneous (V1) and mucosal (V3) trigeminal afferents project onto the same interneurones in the trigeminal principal sensory nucleus. This clearly supports the idea that peripheral manipulation of the VIIth and the XIIth nerves induces a plastic change within this nucleus.     

A study of blink reflex in person with severely handicapped]

1) We evaluated blink reflex from 50 cases of severe handicapped. 7 cases (14%) had normal blink reflex. Abnormality of prolonged latency or no response of blink reflex was much more easily seen on R2 and R2' than R1, and dysfunction of spinal trigeminal complex or bulbar reticular formation might be existed in those cases. 2) We found abnormal blink reflex had some relationship with mental disturbance or bulbar function. Result of ABR and head CT also suggested that some kinds of cerebral factors might influenced to blink reflex of severe handicapped cases. 3) Blink reflex was one of the useful records for severe handicapped patients to evaluated underline pathogenesis of brain stem function.     

Blink reflex abnormalities in children with Tourette syndrome

Tourette syndrome (TS) is a common disorder which typically occurs during childhood or early adolescence. There is no definitive diagnostic test for TS. The objective of this study was to demonstrate whether neurophysiological abnormalities of the blink reflex can be observed in children with TS. We enrolled 15 children with TS, diagnosed according to DSM IV Diagnostic Criteria, and 15 controls. The blink reflex was elicited by stimulating the supraorbital nerve in order to measure the early response (R1), homolateral and contralateral R2 (late) responses, amplitude of R1 and duration of R2. The mean duration of R2 was significantly longer in TS patients than in the controls ( P  < 0.001, Student's t -test). An abnormal pattern of the blink reflex can be, even in childhood, an early neurophysiologic marker of TS, which is not related to the duration of TS or to the age of onset.     

Prognostic value of electrically elicited blink reflex in neonates

The electrically elicited blink reflex (BR) was evaluated in 80 normal neonates and 12 neonates with neurologic abnormalities. In normal subjects, R1 and bilateral R2 responses were elicited both while awake and in a quiet sleep state. Whereas the R1 response was consistently elicited in the active sleep state, as well as while awake, the ipsilateral R2 response was markedly suppressed and the contralateral R2 response was almost absent. The BR in neonates with neurologic abnormalities showed the following variable results: normal, prolonged latency, or suppressed response at initial recording. Abnormal BRs were detected in most neonates with respiratory or sucking problems. While neonates in whom a suppressed response or prolonged latency persisted for over three months had a poor prognosis, those with normal BRs or early correction of the BR abnormality had almost normal development. The BR appears to be useful not only to evaluate brain-stem function in the neonatal period but also to predict subsequent outcome.     

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.     

Blink reflex abnormalities in chronic alcoholics

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.     

Unmasking of the trigemino-accessory reflex in accessory facial anastomosis

OBJECTIVE: To evaluate the possible blink reflex responses in facial muscles reinnervated by the accessory nerve. METHOD: Eleven patients with a complete facial palsy were submitted to a surgical repair by an accessory facial nerve anastomosis (AFA). In this pathological group, blink reflex was studied by means of percutaneous electrical stimulation of the supraorbital nerve and recording from the orbicularis oculi muscle. A control group comprised seven normal people and seven patients with a complete Bell's facial palsy; in this group, responses on the sternocleidomastoideus (SCM) muscles were studied after supraorbital nerve stimulation. RESULTS: All the patients with AFA showed a consistent degree of facial reinnervation. Ten out of the 11 patients with AFA showed reflex responses; in six, responses were configured by a double component pattern, resembling the R1 and R2 components of the blink reflex; three patients had an R1-like response and one patient showed a unique R2 component. Mean values of latencies were 15.2 (SD 4.6) ms for the R1 and 85.3 (SD 9.6) ms for the R2. In the control group, eight out of 14 people had evidence of reflex responses in the SCM muscles; these were almost exclusively configured by a bilateral late component (mean latency 63.5 (SD15.9) ms) and only one of the subjects showed an early response at 11 ms. CONCLUSION: The trigemino-accessory reflex response in the pathological group was more complex and of a significantly higher incidence than in the control group. These differences could be tentatively explained by a mechanism of synaptic plasticity induced by the impairment of the efferent portion of the reflex. This could unmask the central linking between the trigeminal and the accessory limbs of the reflex. The findings described could be a demonstration of neurobionomic function in the repairing process of the nervous system.     

Blink reflex in hemiplegia.

An electrophysiological study of the blink reflex was undertaken in 20 normal subjects and in 28 patients complaining of central facial palsy caused by unilateral hemispheral damage. In normal subjects, the latency, amplitude and organization of R1 and R2 responses are well known. Habituation of R2 responses occurred between 1 and 2 c/sec stimulation rate. R1 responses habituated at a higher stimulation rate (5 c/sec). In patients with unilateral hemispheral lesion, our results showed that changes in the blink reflex responses were bilateral. On the hemiplegic side the responses showed a decreased amplitude, while they were facilitated on the "normal" side. However, there was no change in latency of the two components of the reflex, on both sides. On the other hand, habituation of the late component occurred on the hemiplegic side for low stimulation rates: (0.5--1 c/sec), while on the "normal" side there was less habituation (3--4 c/sec), as compared with normal subjects. These results agree with those of experimental studies on cortical modulatory influences on brain-stem nuclei. They suggest a tactile origin of the two components of the blink reflex.     

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.     

Cyclic alterations of blink reflexes: an EEG and EMG study during wakefulness and sleep.

Studies of the blink reflex were undertaken in twelve normal subjects during wakefulness and different sleep stages. The early R1 and the late R2 components of the reflex were analyzed. R1 was present in only one subject during stage I sleep and subsequently disappeared in stage II to IV. In all subjects, R2 was gradually diminished and totally disappeared during stage IV. During the REM stage, R1 was seen in only four-out-of-twelve subjects but all R2 returned. Alterations of R1 and R2 of the blink reflex during different sleep stages suggest that the underlying mechanism includes both supranuclear and infranuclear activities. Our finding strengthens further the notion of dual hyponogenic mechanisms for sleep.     

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.