Prognostic significance of the electrically elicited blink reflex in neonates

Brainstem dysfunction in alternating hemiplegia of childhood: a neurophysiological study

Six patients with alternating hemiplegia of childhood (AHC) underwent motor evoked potentials (MEPs), somatosensory evoked potentials (SEPs) and blink reflex recording. No SEP abnormality was found. As for MEP recording, central conduction time did not differ between patients studied during either interictal or ictal phase, and normal subjects, suggesting that the pyramidal system function is spared. In blink reflex recording, the latencies of both the ipsilateral (iR2) and contralateral (cR2) R2 components were significantly longer (P<0.01) in patients during the interictal phase than in normal subjects. Moreover, the iR2 and cR2 areas were significantly reduced (P<0.01) in patients during the interictal phase, compared with normal subjects. During the ictal phase, the ipsilateral R2 latency was significantly decreased after stimulation of the hemiplegic side, compared with the interictal phase (P<0.05). The blink reflex abnormalities suggest a brainstem dysfunction, which may be linked to the pathophysiological mechanisms of the disease.

Morphometric evaluation of neonatal brainstem development by means of the ultrasonographic method

Development of the midbrain in 260 newborn infants was studied by means of the ultrasonographic method. The 260 infants were divided into four groups; 211 appropriate-for-date (AFD) infants without intracranial abnormalities or chromosomal disorders, 41 light-for-date (LFD) infants without intracranial abnormalities or chromosomal disorders, 5 cases of Down syndrome and 3 cases of trisomy 18. The midbrain area (MBA) was measured in transverse sections using a Sonos 1000 (YHP) within 24 h of birth. MBA of the 211 AFD infants was correlated with gestational age (GA), the standard curve being -0.0029(GA)2 + 0.2611(GA) -3.335 (r = 0.87, P < 0.0001). MBA of the other three groups were compared with this standard curve. Thirty-seven of the 41 LFD cases and all the Down syndrome infants showed MBA within 1.5 S.D. of the standard curve. However, all the infants with trisomy 18 had smaller MBA than -1.5 S.D. of the standard curve. The standard curve should be useful for assessing the gestational age of newborn infants and for detecting abnormal development of the brainstem in developmental disorders.

The blink reflex in neonates with a subsequent poor outcome

We examined maturational changes in the electrical blink reflex in 11 handicapped children, i.e., 4 cases of developmental delay, 4 of cerebral palsy, 2 of congenital hydrocephalus, and 1 of congenital cytomegalovirus infection. The developmental delay and cerebral palsy cases were all born at 25-36 weeks' gestation. In all cases, prolonged latency, low amplitude, or the absence of the late component of the blink reflex was observed in the follow-up study. These results indicate that prematurity and some congenital impairment mainly influence the maturation of the long-loop reflex arc in the blink reflex.

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.

Prediction of the prognosis in neonatal asphyxia by photo-evoked eyelid microvibration

Neonatal asphyxia causes hypoxic-ischemic encephalopathy and may damage the central nervous system. We studied neonatal asphyxia with photo-evoked eyelid microvibration (PEMV) which is a blink reflex elicited by photic stimuli. The latency of PEMV changed according to the severity of encephalopathy and the degree of unconsciousness. All of the neonate who had showed disappearance of PEMV died. When the prolonged latency persisted, the infant had a strong probability of sustaining neurological sequelae. PEMV provides useful information for predicting the outcome of neonatal asphyxia.

Auditory brain stem response and electrically elicited blink reflex in handicapped children

The auditory brain stem response and the blink reflex were studied in 35 handicapped children in order to evaluate brain stem function. The auditory brain stem response and the blink reflex were abnormal in 20 and 16 cases, respectively. Of these, 14 had both auditory brain stem response and blink reflex abnormalities. The prevalence of auditory brain stem response and blink reflex abnormalities was high in severely handicapped children with difficulty in chewing or swallowing. The blink reflex was abnormal in four of 32 sides with a normal auditory brain stem response and 15 of 23 sides with an abnormal auditory brain stem response threshold, which reflects hearing loss or brain stem dysfunction. We conclude that the combined application of these two noninvasive tests is useful not only to delineate the extent of brain stem lesions but also to determine whether or not patients with an abnormal auditory brain stem response threshold have brain stem dysfunction.

An electrophysiologically defined trigemino-reticulo-facial pathway related to the blink reflex in the cat

This study examines the direct projection of neurons in the pontomedullary reticular formation (RF) to the dorsal division of the facial nucleus (FN), where the orbicularis oculi motoneuron pool is located, and the nature of synaptic inputs to the RF neurons from the supraorbital branch of the trigeminal nerve (SON), using electrophysiological techniques in anesthetized cats. A large number of the RF neurons directly projected to the ipsilateral FN dorsal division, and some of these neurons issued axon branches probably terminating on motoneurons in the division. Many of the RF neurons projecting to the dorsal division were synaptically activated by ipsilateral SON stimulation. Most latencies of their activation were between the latencies of the early and late blink reflex responses, and the remaining latencies were shorter than those of the early response. These results suggest that the RF neurons mediate both the early and the late blink reflex responses, but mainly the late response, as premotor relay neurons.

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.