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.     

MATURATION OF CUTANEOUS REFLEX RESPONSES RECORDED IN THE LOWER LIMB IN MAN

Cutaneous reflex responses from tibialis anterior muscle following electrical stimulation were recorded for 39 normal children between the ages of one and 16 years. In the first year of life stimulation produces a monophasic excitatory reflex response at short latency; in the second year it produces long- as well as short-latency increases in activity. Maturation of reflex function continues during the school years, with progressive emphasis on long- rather than short-latency components. These results are discussed in relation to mechanisms underlying the acquisition of motor skills during childhood.     

Cutanecmuscular Reflexes Recorded from the First Dorsal Interosseous Muscle of Children with Cerebral Palsy

Cutaneomuscular reflexes were recorded from the first dorsal interosseous muscles of 21 children with spastic cerebral palsy. The reflex responses in children with cerebral palsy were consistent with dysfunction of the pyramidal system, but differed from those seen in adults with central nervous lesions. This provides further evidence that the effect of a central nervous lesion on the reflex control of movement is dependent on whether it occurs in early or adult life.     

Electrophysiological recording of deep tendon reflexes: normative data in children and in adults.

OBJECTIVE: Latency measurement of myoelectric deep tendon (T) reflex responses is not usually performed in EMG laboratories. We investigated the optimal conditions of reliable recording of T reflex in children and adults. METHODS: Two hundred and sixty-eight normal subjects (139 males, 129 females, age rank 2 days-80 years) were studied. T reflexes were recorded from soleus and rectus femoris muscles (children and adults) and from triceps brachialis, biceps brachialis and flexor carpi radialis (adults). Specially devised hammers were used. They were fitted with a spring switch system in order to trigger the trace display on the EMG machine. Distinct technical options for the synchronisation delay assessment were tested. The nerve conduction velocities along reflex pathways were computed by referring the T wave latencies to subject's height. RESULTS: Reliable recordings could be obtained in all cases, with a strong linear correlation of the response latency with height. T reflex conduction velocities increased as the log value of subject age. Normative data from birth to 80 years are provided. CONCLUSION: T reflex recording represents a painless and easily performed technique. It may be helpful for the assessment of proximal conduction velocities, especially in children during maturation of the peripheral nervous system.     

Cutaneomuscular reflex responses recorded from the lower limb in children and adolescents with cerebral palsy

Cutaneomuscular reflex (CMR) responses were recorded from lower-limb and trunk muscles in 27 subjects with cerebral palsy (CP) (spastic, 21; athetoid, six) and in neurologically healthy (control) subjects, aged 3 to 15 years, while standing. In the 21 subjects with spastic CP, but not in the six subjects with athetoid CP, CMR responses were more widely distributed between ipsilateral lower-limb and trunk muscles compared with age-matched control children. CMR responses in older subjects with CP were similar to younger control subjects, lacking supraspinally mediated, long-latency components. Short-latency, spinally-mediated, excitatory CMR components were seen simultaneously in pairs of distal, antagonistic lower-limb muscles in half of the subjects with spastic CP, but in none of the control children. In subjects with spastic-type CP, the abnormal reflex responses indicate disordered spinal and supraspinal inputs to motor neurones, although there was no convincing correlation between these responses and the severity of spasticity.     

Different responses to auditory and somaesthetic stimulation in patients with an excessive startle: a report of pediatric experience.

OBJECTIVES: Children with cerebral injury often exhibit brief muscle contraction to a variety of stimuli. However, it remains to be determined whether or not the pattern of the reaction is stereotypical irrespective of the site stimulated. To answer this question, we studied electromyographic (EMG) responses to three types of stimuli in children. METHODS: The EMG responses of cranial and limb muscles were recorded after acoustic or somaesthetic stimulation in 6 patients and 23 control subjects. RESULTS: Acoustic stimuli evoked patterned motor activity with a rostrocaudal progression. Nose-tapping stimuli elicited reflex EMG activity in the VIIth cranial muscles that was similar to the R1 component of the electrical blink reflex. Sternum-tap stimuli evoked motor activity in the sternocleidomastoid and arm muscles, and this reflex was probably mediated through the cervical cord (H-reflex). Moreover, late reflexes were evoked following these early reflexes in the patients. In particular, atypical forms of myoclonic jerks were evoked on sternum-tap stimuli. CONCLUSIONS: Many types of primitive reflexes were evoked following three types of stimuli. These reflexes included startle reflex, trigeminomotor reflex, H-reflex and atypical forms of myoclonus, and they were enhanced in the patient group. There are many startle-mimicking reflexes.     

Masseter reflex in childhood and adolescence

We report normative data of masseter reflex from a group of 54 children 2-16 years of age. For statistical analysis, the patients were divided into five age groups: 2-4, 5-7, 8-10, 11-13, and 14-16 years of age. A tap to the chin, using a hammer with a trigger device, elicited the masseter reflex. The response was recorded by surface electrodes. The onset latency and peak-to-peak amplitude of the averaged curve of eight reflex responses were measured. The reflex response could be recorded in all children and adolescents of all groups. The mean latency shortened from age 2 to 7 and was stable at the age of 8 years. As a sign of maturation, the increase of amplitude corresponded to the shortening of latency and was also stable at the age of 8 years. Abnormal side differences in latency of 0.9 ms (age group 2-4 years), 1.1 ms (age group 5-7 years), and 0.8 ms (age group 8-16 years) were evaluated. An amplitude ratio (lower amplitude divided by higher one) above 0.33 was calculated as normal.     

Nissen-type fundoplication and its effects on the emetic reflex and gastric motility in the ferret

Recurrent vomiting with failure to thrive is a common problem in neurologically impaired children. Many undergo fundoplication to control the underlying gastro-oesophageal reflux. The results of surgery are not always satisfactory and post-operative retching may be a major problem - a symptom indicative of activation of the emetic reflex. An animal model of antireflux surgery has been developed and used to investigate the effects of such surgery upon the emetic reflex and vagal influences on gastric motility. Following surgery, animals responded to a previously subemetic dose of a centrally acting opiate receptor agonist (loperamide), suggesting that fundoplication may sensitize the emetic reflex. A gastric vago-vagal reflex (tonic inhibition of corpus tone) and responses to direct stimulation of vagal motor efferents (both cholinergic and nonadrenergic noncholinergic responses) were not significantly affected by antireflux surgery. Mechanisms by which neural damage may sensitize the emetic reflex are discussed, together with the possible clinical implications for the management of post-operative symptoms in neurologically impaired children.     

Orbicularis oculi and orbicularis oris reflexes in blepharospasm and torticollis spasmodica during spasm-free intervals

To investigate possible abnormalities of the blink reflex pathways, we analyzed the latencies and amplitudes of the blink reflex responses in the orbicularis oculi (Ooculi) muscle, following supraorbital nerve stimulation, in 19 patients with blepharospasm, 16 patients with torticollis spasmodica and 22 control subjects. Furthermore, in order to examine the suprasegmental control of the responses, the reflex responses were also evoked in the orbicularis oris (Ooris) muscle after stimulation of the ipsilateral supraorbital nerve. The responses were recorded only when subjects had no contractions of the eyelid muscles, either involuntarily, voluntarily or spontaneously; this could be controlled by a sound signal. The metrics of the reflex responses in the Ooculi and Ooris muscles in patient groups were comparable to those in controls. Our data indicate that the afferent and efferent pathways of the reflex arc and the suprasegmental control of the reflex are intact in patients with blepharospasm and torticollis spasmodica, at least during spasm-free intervals. Alterations of responses may occur during spasms due to either segmental or suprasegmental changes.     

Long-lasting modification of reflexes after neonatal nerve injury in the rat

The reflex activity of motoneurones to the extensor digitorum longus (EDL) muscle following sciatic nerve crush during the first 5 days after birth (neonatal crush) or in the adult (adult crush) was studied 3-6 months later, when the axons had reinnervated their target muscles. Electromyograms (EMG) and muscle tension were recorded from the EDL muscle (a physiological flexor) on the injured and uninjured sides. Reflex responses were evoked by stimulation of the common peroneal (CP), the tibial (T) and the sural (S) nerves, ipsilateral and contralateral to the side of injury. In animals which had sustained a neonatal crush, stimulation of branches of the injured sciatic nerve elicited ipsilateral reflex responses that were about 3 times larger than those recorded from the uninjured side or in normal animals. Stimulation of the CP nerve on the uninjured side invariably elicited a contralateral reflex response from the reinnervated muscles, while stimulation of the CP nerve on the injured side either failed to produce a response or produced a very weak reflex response from the control muscles. Reflexes recorded from the reinnervated muscles by stimulation of the tibial and sural branches of the uninjured sciatic nerve were 3-7 times greater than those recorded from the uninjured side or in normal animals. The reflex responses obtained from reinnervated muscles of animals with nerve injury in adulthood were similar to those obtained from control, unoperated adult rats. These results indicate that sciatic nerve injury during a critical development period leads to a permanent enhancement of reflex responses from reinnervated fast flexor muscles not seen after similar injury in adults.     

The trigemino-cervical reflex in normal subjects

There are only few reports on the trigemino-cervical reflex in humans and there is debate over the best method of reflex examination. The aim of this study was, comparing different methods, to provide a reproducible method for evaluating the trigemino-cervical reflex. The trigemino-cervical reflex was studied in 32 healthy volunteers. The stimulation was applied to the supraorbital, infraorbital or mental nerve. Recordings were performed bilaterally from the sternocleidomastoid and trapezius muscles at rest. The reflex was also examined during maximal voluntary contraction of the sternocleidomastoid muscle after supraorbital nerve stimulation. It presented as a two-component reflex if recorded from a tonically active muscle and as a one-component reflex if recorded from a relaxed muscle. The most reproducible reflex responses were obtained from the resting sternocleidomastoid muscle after stimulation of the supraorbital nerve. In conclusion, the trigemino-cervical reflex may be most easily obtained from the relaxed sternocleidomastoid muscle after supraorbital nerve stimulation.     

Analysis of the corneal reflex with air puff: normal controls and patient groups.

Though there are several reports published about the corneal reflex elicited by different methods, a standardized electrophysiologic study with air puff in man has not been published. The aim of this study is to standardize the corneal reflex elicited by air puff to cornea. The authors studied the corneal reflex with air puff and direct touch by using a standardized method in patients with thalamic hemorrhage (n = 15), hemispheric infarction (n = 9), brainstem infarction (n = 9), multiple sclerosis (n = 12), and Bell's palsy (n = 12) and in normal control subjects (n = 21). The conventional blink reflex (BR) was also studied. The reflex responses were recorded from both orbicularis oculi muscles by air puff and direct touch to cornea in addition to the electrical stimulation of the supraorbital nerve. No statistical difference could be detected between the responses elicited by air puff or direct touch to cornea (P > 0.05). Corneal reflex responses were statistically different from the R2 response of the BR (P < 0.005). Because the responses elicited by direct touch and air puff to cornea are identical, air puff to cornea can be used confidently to study the corneal reflex.     

Direct and reflex responses in perineal muscles on electrical stimulation.

Responses in the external anal and urethral sphincters as well as in the bulbocavernosus muscle have been evoked by supramaximal electrical stimulation of the penis (or clitoris), perineum and the peri-anal region and recorded electromyographically in 82 male subjects 5 to 73 years old and in nine female subjects 18 to 55 years old, who had no systemic diseases or demonstrable sacral nervous system lesion. On perineal stimulation (including the penis or clitoris) reflex responses with a typical latency of 33 ms and which exhibit no habituation were obtained in all muscles examined. Stimulation of the peri-anal region gave habituating reflex responses with a typical latency of 55 ms in all muscles examined. On perineal, and sometimes also peri-anal stimulation, stable short latency responses with typical latencies of 5 and 13 ms were recorded; both were considered to be direct responses. The different evoked muscle responses obtained by stimulation in the perineal and peri-anal region have to be distinguished when the bulbocavernosus and anal reflexes are recorded for evaluation of sacral nervous system lesions.     

Trigeminally induced startle in children with hyperekplexia.

To determine the physiological features of startle reactions in children with hereditary hyperekplexia, motor responses to auditory and trigeminal stimulation were investigated in 2 patients and 3 control subjects by means of multiple surface electromyographic recordings. The pattern of motor activation in auditory startle was similar in the two groups, although the responses in the patients were increased in terms of the extent of the responses. In the patients, nose taps elicited two separate responses in various muscles. The initial, short-latency response was often elicited in all the muscles examined. This reflex was similar to the R1 component of the electrical blink reflex. In addition, the early reflex was immediately followed by the second response, which also appeared widely and was similar to R2 of the blink reflex. Taps on the supraorbital nerve elicited multiple startle patterns consisting of these two responses, although generalization was infrequent. In the control subjects, these responses were elicited in a few muscles. In the hyperekplectic children, both the early and second responses to trigeminal stimulation were increased, in addition to the audiogenic reflex. It was suggested that enhancement of these responses occurred due to hyperexcitability in the brainstem reticular formation in our patients.     

Effect of contraction level and magnitude of stretch on tonic stretch reflex transmission characteristics.

Electromyogram tonic stretch reflex responses were recorded from biceps brachii muscles in normal and cerebral palsied subjects sustaining either 10% or 20% of maximum voluntary contraction and attempting to keep the elbow stiff in a fixed position. The muscle was stretch by a sinusoidal perturbation applied by the experimenter to the elbow angle. Five different amplitudes of stretch were employed ranging 1.67 to 10.0 degrees peak to peak variation of elbow angle. Spectral analysis of the rectified and filtered electromyogram revealed "noisy" sinusoidal reflex responses with negligible harmonic distortion but the amplitude of the reflex responses did not increase linearly with the amplitude of stretch. An analysis of variance showed that for both groups of subjects the gain of the tonic stretch reflex increased significantly (p less than 0.001) with contraction level and decreased significantly (p less than 0.001) with magnitude of stretch. This finding illustrates that both magnitude of stretch and level of contraction need to be carefully controlled when measures of tonic stretch reflex responses are used to assess changes of muscle tone.     

Developmental and age-related changes in reflexes of the human jaw-closing system.

Reflex responses of the jaw-closing system to innocuous mechanical stimulation of the tongue and palate were examined in a group of 25 girls aged 7-8 years and in a group of 25 women aged 70-80 years. Responses were measured both as changes in background biting force and from bilateral recordings of masseter EMGs. For comparative purposes, results from an earlier study of 35 young adult women (aged 18-25 years) were available. Compared to younger groups of subjects, reflex responses of the elderly were reduced in numbers and amplitude, were characterized by fewer initial excitatory component responses, and had longer latency to onset. Analyses of responses of the children indicated that age 7-8 years is a transitional period. Some children show adult-like responses, while others display responses that appear to represent earlier forms or transitional responses. These results suggest that oral-motor reflexes are not fixed response patterns upon which more complex motor skills, such as speech, are built. Rather, oral reflex development appears to occur in concert with the acquisition of complex motor skills. Systematic changes in reflex responses also occur in the period from young adulthood to seventh decade of life. This result indicates a continuous evolution of oral sensorimotor systems throughout the human life span.     

The tibialis anterior reflex in healthy subjects and in L5 radicular compression.

Phasic stretch reflexes were evoked in the tibialis anterior (TA) muscle, by tapping the dorsal side of the foot with a hand-held reflex hammer. The responses were recorded by means of surface electrodes. The TA reflex was examined in 70 healthy subjects and in 18 patients with L5 radicular compression. In 58 (83%) of the healthy subjects the reflex could be recorded bilaterally, in eight (11%) subjects no reflex was found on either side, and in four (6%) it was absent in one leg. Simultaneous recordings from the gastrocnemius-soleus showed that TA responses were not caused by volume conduction from that muscle. In the 18 patients with L5 radicular compression the TA reflex was absent on the affected side 13 times (72%) and present bilaterally in the other five cases. If asymmetry of the reflex (unilateral absence) is considered as a test for the presence of L5 radicular compression, the likelihood ratio for a positive test is 12.0, and for a negative test 0.3. The examination of the TA reflex is easily performed and can be useful in the diagnosis of L5 radicular compression.     

Analysis of reflex activity in cardiac sympathetic nerve induced by myelinated phrenic nerve afferents

Electrical stimulation of the phrenic nerve afferents evoked excitatory responses in the right inferior cardiac sympathetic nerve in chloralose-anaesthetized cats. The reflex was recorded in intact and spinal cats. The latency and threshold of the volley recorded from the phrenic nerve as well as of the cord dorsum potentials evoked by electrical stimulation of the phrenic nerve indicated that group III afferents were responsible for this reflex. The phrenicocardiac sympathetic reflex recorded in intact cats was followed by a silent period. The maximum amplitude of the reflex discharges was 800 microV, the latency was 83 ms and the central transmission time 53 ms. Duration of the silent period lasted up to 0.83 s. In spinal cats the reflex was recorded 5.5-8 h after spinalization. The maximum amplitude of the spinal reflex discharges ranged from 22 to 91 microV and the latency from 36 to 66 ms.     

Long latency response of the mentalis muscle following transcranial magnetic stimulation with a circular coil in normal subjects

Short latency response (SLR), middle latency response and long latency response (LLR) are elicited in facial muscles by transcranial magnetic stimulation. Although it has been said that the LLRs are elicited by the trigeminal nerve stimulation, a trigeminofacial reflex is recorded easily in normal subjects by the electrical stimulation in orbicularis oculi muscles as a blind reflex, but a trigeminal-facial reflex recorded in orbicularis oris, namely a snout reflex, is more difficult to record in normal subjects. The aim of this study is to demonstrate the LLR of lower facial muscles (mentalis muscle) by the transcranial magnetic stimulation, using a circular coil. The transcranial magnetic stimulations were performed over parieto-occipital scalp with frequencies of random and 0.3 Hz in 11 normal subjects and the responses in the mentalis muscle were recorded. The LLR of the mentalis muscle was recorded in all 11 subjects following SLRs. The latency, duration and LLR/SLR ratio were 37.4 msec, 20.3 msec and 9.1%, respectively. The waveform of the LLR varied trial to trial showing habituation with a stimulation of 0.3 Hz. At this time the LLR of the masseter muscle was not recorded following this transmagnetic stimulation. It was suggested that the LLR of the mentalis muscle is recorded by the transcranial magnetic stimulation of the trigeminal nerve with a circular coil. The ease and reliability of their recording make it possible to apply this LLR clinically as well as a blink reflex.     

Optimal stimulus duration for the H reflex

Authorities advocate different stimulus durations to produce an H reflex. In order to find the optimal stimulus duration for recording H reflexes, the recruitment curves for H reflexes and M responses were studied in 10 healthy subjects. The H reflex was recorded in the upper and lower extremities, and the durations of the electrical stimulus used ranged from 0.1 to 3 msec. The amplitude of the H reflex and the relation between the H reflex and M response changed with stimulus duration. H reflexes are brought out to advantage using a stimulus duration between 0.5 and 1 msec.