Absence of tonic electromyographic activity during sleep in normal and spastic nonmimetic skeletal muscles in man

An electromyographic study of nonmimetic skeletal muscles was carried out in 8 normal adults and 4 patients with spastic hemiparesis during all stages of sleep for a total of 21 nights. All normal subjects showed absence of tonic electromyographic activity in all nonmimetic skeletal muscles in all stages of sleep. Also, during quiet, relaxed wakefulness, tonic muscle discharges disappeared in the normal subjects. Three patients with upper motor neuron spasticity demonstrated results during sleep similar to those obtained in the normal subjects. In the fourth patient, tonic muscle discharges persisted into stage 2 non-REM sleep, disappeared within 30 to 240 seconds following the onset of stage 2 sleep, and were absent during stages 3 and 4 sleep and REM sleep.     

Developmental changes in electrically elicited blink reflex in infancy and childhood

Developmental changes in electrically elicited blink reflex (BR) in 118 normal subjects, aged from 32 weeks of conceptional age to 14 years of age. During the waking state, R1 and bilateral R2 responses were always elicited. The latency of R1 shortened rapidly during the neonatal period, reaching the adult value at 3 months of age. The latency of R2 and contralateral R2 (CR2), which were elicited synchronously after 3 years of age, shortened slowly during childhood and reached the adult value at 6 years of age. The conduction indexes of R1, R2 and CR2, which were calculated as head circumference/latency (m/sec), increased rapidly during the neonatal period and reached the adult values at 6 years of age. The influence of NREM sleep on BR in neonates was different from those in infants and children. While BR of neonates in NREM sleep showed similar to that seen in wakefulness, BR of infants and children after one month of age was suppressed during NREM sleep. BR pattern in NREM sleep in infants and children after 6 months of age was similar to that seen in adults.     

The blink reflex in "chronic migraine".

OBJECTIVES: Activation of the trigeminovascular system and sensitisation of brainstem trigeminal nuclei are thought to play an important role in migraine. The aim of this study was to investigate the blink reflex and its habituation in patients with "chronic migraine". METHODS: We studied 35 patients suffering from "chronic migraine" (IHS classification criteria) outside and during a spontaneous attack, and 35 control subjects. An EMG device with a specific habituation test program was used to elicit and record blink reflex responses and to randomly repeat stimulations at different time intervals so as to induce habituation. RESULTS: The R(1) and R(2) latencies, amplitudes and areas of the basal blink reflex were similar in patients studied both outside and during an attack as well as in control subjects, whereas the blink reflex habituation responses were markedly reduced in patients studied outside an attack. The percent changes in the R(2) areas from the baseline values, obtained when stimuli were delivered at time intervals of 10, 5, 4, 3, 2 and 1s, were statistically different (p<0.01-p<0.001) from those of the same patients studied during a migraine attack and of those of control subjects. There was a significant correlation between decreased habituation of the blink reflex and a higher frequency of attacks. The stimulus intensities of the blink reflex (multiples of the detection threshold intensities) were significantly lower (p<0.001) on the side affected, or more severely affected, by headache in patients studied during a migraine attack. CONCLUSIONS: The decreased habituation of the blink reflex outside an attack reflects abnormal excitability in "chronic migraine", which normalizes during the attacks. The inverse correlation between the frequency of attacks and habituation responses confirms the abnormal excitability induced by the high frequency of attacks. Central sensitisation mechanisms (allodynia) may explain the lower detection thresholds observed on the side affected by headache in patients during the attacks. SIGNIFICANCE: The blink reflex and its habituation may help shed light on the subtle neurophysiological changes that occur in migraine patients between and during attacks.     

Maturation of blink reflex in children

The blink reflex was examined in 57 subjects aged from neonate to adult in the alert state. The ipsilateral late response (R2) was elicited in all subjects and considered most suitable to evaluate maturational changes of the blink reflex. In a few subjects older than 3 years and of adults, the ipsilateral early response (R1) was difficult to observe. The contralateral late response (R2') could not be obtained in 32% of neonates and infants. From the observation about developmental change of an interference pattern, a latency shortening of R2 and a latency difference between R2' and R2, the blink reflex in children may be considered as mature at no later than 5 years of age. In addition, the R2 latency tended to increase temporarily through 1 or 2 years from late infancy. The reflex circuit evaluated by the blink reflex in children may partially change its makeup after the early infantile period and is almost fully mature at no later than 5 years.     

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.     

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.     

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.     

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.     

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 significance of the electrically elicited blink reflex in neonates

The electrically elicited blink reflex was examined in ten normal neonates, 11 postasphyxial neonates, and 3 congenital hydrocephalus cases. The blink reflex was elicited in all cases. In normal neonates, the latencies and amplitudes were 10.9 +/- 0.7 msec and 159 +/- 62 microV at R1, 34.3 +/- 1.4 msec and 123 +/- 30 microV at R2, and 40.7 +/- 2.3 msec and 84 +/- 25 microV at R'2 respectively. Ischemic-hypoxic brain damage during the neonatal period mainly influenced the late components of the blink reflex. The blink reflex of the postasphyxial neonates showed significantly prolonged latencies of R2 and R'2. The amplitudes were increased in cases with a fair prognosis and decreased in cases with a poor prognosis. A case of congenital hydrocephalus with mental retardation also showed the prolonged latencies of R2 and R'2 in neonatal period. The blink reflex in neonates appears to be useful in predicting the outcome in cases of neonatal asphyxia and congenital hydrocephalus.     

Reflexes elicited from cutaneous and mucosal trigeminal afferents in normal human subjects

It has been shown that in patients in whom the central stump of the hypoglossal nerve has been anastomosed to the peripheral stump of a lesioned facial nerve, supraorbital nerve stimulation can elicit a short-latency reflex (12.5±0.6 ms; mean±S.D.) in facial muscles similar to the R1 disynaptic blink reflex response, but not followed by an R2 blink reflex component⁴⁶. Thus in addition to replacing the facial neurons at peripheral synapses, these hypoglossal nerves contribute to a trigemino-hypoglossal reflex. The aim of this work was to study the type of reflex activities which can be elicited in both facial and tongue muscles by electrical stimulation of cutaneous (supraorbital nerve) or mucosal (lingual nerve) trigeminal (V) afferents in normal subjects. The results show that although stimulation of cutaneous V1 afferents elicits the well-known double component (R1–R2) blink reflex response in the orbicularis oculi muscles, it does not produce any detectable reflex response in the genioglossus muscle, even during experimental paradigms designed to facilitate the reflex activity. Conversely, stimulation of mucosal V3 afferents can elicit a single reflex response of the R1 type in the genioglossus muscle but not in the orbicularis oculi muscles, even during experimental paradigms designed to facilitate the reflex activity. These data are discussed in terms of two similar but separate circuits for the R1 responses of cutaneous (blink reflex) and mucosal (tongue reflex) origins. They suggest that in patients with hypoglossal-facial (XII–VII) nerve anastomosis, the short-latency trigemino-‘hypoglossal-facial' reflex of the R1 blink reflex type observed in facial muscles following supraorbital nerve stimulation could be due to changes in synaptic effectiveness of the central connectivity within the principal trigeminal nucleus where both cutaneous and mucosal trigeminal afferents project.     

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.     

Decreased habituation of the R2 component of the blink reflex in migraine patients.

OBJECTIVE: Activation of the trigemino-vascular system as well as of brainstem trigeminal nuclei are thought to play an important role in migraine. The aim of this study was to investigate the habituation phenomenon of the blink reflex in 30 headache-free migraine patients and 30 control subjects. METHODS: An electromyographic device with a specific habituation test program was used to elicit and record blink reflex responses on both the right and left sides, and to randomly repeat the stimulations at different time intervals in order to induce habituation. RESULTS: Whereas the R1 and R2 latencies, amplitudes and areas in the basal assessment were similar in patients and control subjects, the blink reflex habituation responses were markedly reduced in migraine patients who had a migraine attack within 72 h after testing (group A). In these patients, the differences between the R2 areas, obtained when stimuli were delivered at subsequent time intervals ranging between 10-5, 5-4, 4-3 and 3-2 s, were statistically different (P<0.001) from those of the patients who had a migraine attack after a longer time interval (group B) and control subjects. CONCLUSIONS: Our data suggest that the brainstem pathways involved in the blink reflex may be activated in the premonitory phase of migraine attacks, probably through mechanisms that involve dopaminergic function.     

Effect of partial sleep deprivation on sleep stages and EEG power spectra: evidence for non-REM and REM sleep homeostasis.

The effect of repeated partial sleep deprivation on sleep stages and sleep EEG parameters was investigated in young subjects. After 2 baseline nights (B1, B2) of 7.5 h, sleep was restricted for 2 nights (D1, D2) to the first 4 h of the habitual bedtime period. Two recovery nights (R1, R2) with 7.5 h sleep followed. During the deprivation nights, stages 1 and 2 and REM sleep were reduced, while slow wave sleep (SWS; stages 3 and 4) was not significantly affected. However, the time integral of EEG power density in the range of 0.75-4.5 Hz (slow wave energy) was reduced. In the recovery period, SWS showed an enhancement in R1, and REM sleep showed a rebound in R1 and R2. An increase of REM sleep in the early part of the sleep period was evident in R1. Sleep latency was reduced in D2, R1 and R2. In accordance with the 2-process model of sleep regulation, EEG power density in non-REM sleep in the range of 0.75-4.5 Hz (slow wave activity) was only slightly higher in D2 and R1 than in baseline. An enhancement of slow wave activity in REM sleep was present in D2. Power density in the frequency range of 13-16 Hz was reduced in non-REM sleep (R1), SWS (R2) and stage 2 (R1). The results show (1) that the moderate reduction of slow wave energy in the deprivation nights induces only a minor enhancement of slow wave activity during recovery sleep; and (2) that a REM sleep deficit gives rise to an immediate rebound when 'slow wave pressure' is low.(ABSTRACT TRUNCATED AT 250 WORDS)     

Voluntary eyelid contraction modifies the blink reflex recovery cycle

In order to determine the extent to which the recovery cycle of the blink reflex is modified by voluntary contraction of the eyelids we investigated the electrically elicited blink reflex with paired stimuli of identical intensity in 9 healthy subjects. We pseudorandomly administered two interstimulus intervals (150 ms and 250 ms) in three different conditions of voluntary contraction of the orbicularis oculi muscle (relaxed, mild lid closure and strong lid closure). Our results show that inhibition of the R2 response following the second stimulus is significantly reduced with voluntary contraction. In addition, we found significantly larger amplitudes and shorter latencies of R1 and R2 with voluntary contraction. We conclude that in healthy subjects, voluntary eyelid contraction causes facilitation or disinhibition not only in the nuclei of the seventh cranial nerve, but also in the polysynaptic pathway of the R2. The possible implications on the interpretation of clinical data are discussed.     

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.     

Nocturnal cardiac autonomic regulation in Parkinson’s disease

Abstract. Diminished heart rate (HR) variability has been reported in patients with early phase Parkinsons disease (PD) using standardized cardiovascular reflex tests. However, limited data exist on HR variability during sleep; thus the present study was performed to investigate the characteristics of HR variability during different sleep stages. The HR variability of 21 newly diagnosed and untreated PD patients and of 22 control subjects was evaluated by using time domain, frequency domain and non-linear methods and by analyzing HR reactions to body movements during the different sleep stages (non-REM stages S1–4 and the REM stage). The nocturnal cardiac autonomic control was disturbed in PD patients compared to controls both during sleep and waking. HR reactions to body movements were decreased especially during REM sleep referring to defective sympathetic cardiovascular control. High frequency spectral power of HR variability was attenuated in the patients in waking and during non-REM sleep but not during REM sleep suggesting that parasympathetic cardiovascular control is also affected in early PD. However, the variance of R-R intervals during non-REM sleep was significantly increased in PD patients. Especially during this sleep stage the patients also moved more than the controls. HR variability is decreased not only in waking but also during sleep in PD patients. However, the increased variance of HR during non-REM sleep refers that in early phase of PD cardiovascular system is still able to react to changing body circumstances. Furthermore, our findings suggest that the indicators measuring the dominant sympathetic or parasympathetic activity of each given sleep stage are the most sensitive measures in revealing disturbed nocturnal ANS function.     

Long‐term depression‐like plasticity of the blink reflex for the treatment of blepharospasm

Our previous work showed a beneficial therapeutic effect on blepharospasm using slow repetitive transcranial magnetic stimulation, which produces a long‐term depression (LTD)‐like effect. High‐frequency supraorbital electrical stimulation, asynchronous with the R2 component of the blink reflex, can also induce LTD‐like effects on the blink reflex circuit in healthy subjects. Patients with blepharospasm have reduced inhibition of their blink recovery curves; therefore, a LTD‐like intervention might normalize the blink reflex recovery (BRR) and have a favorable therapeutic effect. This is a randomized, sham‐controlled, observer‐blinded prospective study. In 14 blepharospasm patients, we evaluated the effects of high‐frequency supraorbital stimulation on three separate treatment days. We applied 28 trains of nine stimuli, 400 Hz, either before or after the R2 or used sham stimulation. The primary outcome was the blink rate, number of spasms rated by a blinded physician and patient rating before, immediately after and 1 hour after stimulation while resting, reading, and talking; secondary outcome was the BRR. Stimulation “before” and “after” the R2 both showed a similar improvement as sham stimulation in physician rating, but patients felt significantly better with the before condition. Improvement in recovery of the blink reflex was noted only in the before condition. Clinical symptoms differed in the three baseline conditions (resting, reading, and talking). Stimulation before R2 increased inhibition in trigeminal blink reflex circuits in blepharospasm toward normal values and produced subjective, but not objective, improvement. Inhibition of the blink reflex pathway by itself appeared to be insufficient for a useful therapeutic effect. © 2013 Movement Disorder Society     

Electrophysiological study of the snout reflex in normal subjects and in parkinsonian and pseudobulbar patients

The snout reflex appeared to be electrophysiologically present in a great majority of normal subjects. Nevertheless, a facilitation of the R2 responses of the snout reflex was found in parkinsonian patients while in pseudobulbar patients an augmentation of the R1 took place. The snout reflex, therefore, seemed to behave in a similar way as the blink reflex. In order to explain the reported findings the authors took into account the different effects of the lesions of the lateral and ventral motor system upon the oligo- and multisynaptic reflexes.     

Early detection of Huntington''s disease. Blink reflex and levodopa load in presymptomatic and incipient subjects.

The R2 response on the blink reflex was found to be abnormal in seven out of 17 Huntington's disease descendants. Such abnormalities were present in four untreated subjects and in three further subjects after administration of a single oral dose of levodopa-carbidopa. An increase in latency and differential latency (four cases), or in a single one of these parameters (three cases) were the abnormalities found, resembling findings in four incipient cases detected during routine family surveys. Continuous administration of levodopa-carbidopa over a 10-20 day period did not induce new characteristics in the blink reflex, nor increase those detected previously, and no case developed chorea. We suggest that the analysis of the blink reflex after a single oral levodopa-carbidopa dosage could provide an objective and quantifiable method for the detection of individuals at risk for Huntington's disease.