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At least 451 records · Page 25Linked to original sources
PubMed2001

Polychlorinated biphenyls (PCBs) and neurological development in children: a systematic review.

BACKGROUND: Polychlorinated biphenyls (PCBs) are complex mixtures of persistent contaminants that are widespread in the environment. Newborns are exposed across the placenta and through breast feeding. Experimental animal studies have indicated that PCBs are neurotoxic. The neurological effects of these compounds on children are not clear. METHODS: A systematic review of literature on the relation between neurological development in children and exposure to polychlorinated biphenyls. RESULTS: Seven follow up studies evaluated the effect of prenatal exposure to PCBs. Two of these studies evaluated highly exposed children. In newborns, an increase of the abnormal reflexes was observed in all four studies evaluating it. During the first months of life, a decrease in motor skills was observed in four of the five studies that investigated psychomotor development; deficits in the acquisition of cognitive skills were observed only in one study assessing non-highly exposed populations. At 4 years of age, an effect on the cognitive areas was observed in four of the five studies that evaluated it. Postnatal exposure to PCBs through breast feeding was not clearly related to any effect on neurological development. CONCLUSIONS: These studies suggest a subtle adverse effect of prenatal PCBs exposure on child neurodevelopment. Differences in study design, inconsistency in some of the results, and the lack of adequate quantitative exposure data, do not allow the derivation of the degree of risk associated with neurodevelopmental effects at current levels of exposure.

Breast Feeding↗
PubMed1975

Babinski response: stimulus and effector.

This is an electromyographic study of the activity in flexor and extensor muscles of the big toe in 22 patients with a Babinski sign and 49 controls, after mechanical or electrical stimulation of the sole. The results indicate: (1) the Babinski sign is mediated by the extensor hallucis longus (EHL), and not by the extensor hallucis brevis; (2) electrical stimuli may fail to activate the EHL in these patients, and conversely may evoke EHL reflexes in control subjects; (3) in skin reflexes, electrical and mechanical stimuli are not freely interchangeable.

Electric Stimulation↗
PubMed1976

Mechanism of the inverted supinator reflex. A clinical and neurophysiological study.

The inverted supinator reflex sign was analysed in two patients by recording the response of the finger flexor muscles of the forearm to tapping of the styloid process of the radius before and after procain infiltration of these muscles. It was found that the response persisted despite the block. The findings support the concept that the underlying mechanism is increased alpha motoneurone excitability below the level of the lesion; however, a possible contribution of the dynamic muscle spindles could not be excluded.

Evoked Potentials↗
PubMed1977

Interpretation of plantar reflexes: biasing effect of other signs and symptoms.

Twenty neurologists were asked to judge a number of plantar responses on film. Each film was preceded by a slide with a fictitious abstract of history and examination (minus the plantar reflex). The main part of the presentation only served to disguise the fact that two films, both showing equivocal toe movements, were presented twice at the same sitting, but with opposing information as to the probability of a Babinski sign. Interpretation of these identical pictures differed significantly (P less than 0.01), conforming to the information given. Thirty other neurologists who rated the films without previous data showed no such change of opinion.

Diagnostic Errors↗
PubMed1978

The Babinski sign and the pyramidal syndrome.

The presence or absence of a Babinski sign can be puzzling, but in the light of existing pathological studies it is more fruitful to consider which pyramidal tract fibres release it than whether they release it. This was investigated clinically, by looking for correlations with other reflex changes and with motor deficits in the leg. A survey of 50 patients with a unilateral Babinski sign and six patients who lacked it in spite of other pyramidal tract signs was supplemented with follow-up of the patients who had acute lesions. Appearance of the Bibinski sign proved to depend on the interaction of two factors: (1) activity (not necessarily hyperactivity) in the segmental pathways of the flexion synergy; (2) a motor deficit of the foot, in some cases consisting only in an impairment of rapid foot movements, and probably representing a disturbance of direct pyramidal tract projections to distal motoneurones.

Female↗
PubMed1979

Tonic vibration reflex in Holmes-Adie syndrome: an electrophysiological study.

The pathophysiological mechanisms underlying benign areflexia were studied in six patients with Holmes-Adie syndrome. No impairment of sensory conduction velocity of sural nerve was found. A normal tonic vibration reflex was obtained in all patients. H reflex was absent in five patients, but responses like F waves were recorded in three subjects. These findings suggest that muscle spindles are not affected and that spinal motoneurone excitability is normal.

Adie Syndrome↗
PubMed1979

Inverted knee jerk: a neglected localising sign in spinal cord disease.

Two cases are described in which inversion of the quadriceps jerk was observed. It is suggested that the finding of an inverted quadriceps jerk is evidence of a spinal cord lesion at 12, 3, 4 segmental level and has for the lumbar cord the same localising value as the inverted supinator jerk for the cervical cord.

Adult↗
PubMed1981

Myotatic reflexes and the on-off effect in patients with Parkinson's disease.

Reflex activity in the biceps and triceps muscles evoked by applied torque perturbations was studied in patients with Parkinson's disease. The perturbations consisted of single pulses or of pseudo-random sequences of pulses of torque. The patients were treated with levodopa and some exhibited marked fluctuations in their clinical disabilities ("on-off" effect). The study was undertaken to see if reflex activity changed in parallel with the fluctuations of their clinical symptoms. It was found that the reflex activity in these patients could be classified into two types, a Type I response differing little from normal and a Type II response exhibiting marked high-frequency (8-14 Hz) oscillations in EMG activity. Both Type I and Type II responses were virtually the same in the "on" as in the "off" state.

Adult↗
PubMed1982

Dysaesthesias and dysautonomia: a self-limited syndrome of painful dysaesthesias and autonomic dysfunction in childhood.

Three children with an acute self-limited syndrome characterised by painful dysaethesias, hypertension, and autonomic dysfunction, in the absence of motor and reflex abnormalities, are presented. They appear to have had a variant of acute polyneuritis involving sensory and autonomic systems. The pathophysiology of hypertension in the Guillain-Barré syndrome and of acute pandysautonomia is discussed. Excessive adrenergic function is considered as a cause of the pain component of the syndrome.

Autonomic Nervous System Diseases↗
PubMed1983

Temporal course of the threshold and size of the receptive field of the Babinski sign.

The changes of threshold and receptive field of the Babinski reflex, with time, were assessed in ten patients with acute cerebrovascular lesions. It was found that the threshold of the reflex decreased gradually and the size of the cutaneous afferent reflex field enlarged with the passage of time. These findings suggest that there is a gradual release or organisation of the reflex flexor synergy of which the Babinski sign is a modified part.

Afferent Pathways↗
PubMed1987

Familial congenital vestibular areflexia.

Three cases in one family are presented with oscillopsia due to vestibular areflexia, but without hearing loss. There was no history of other neurological or otological diseases (including infectious diseases) or use of neuro-ototoxic drugs. Laboratory tests, including tests for autoimmune diseases, were undisturbed. Petrosal radiographs and brain CT scans were normal. The pedigree suggested autosomal recessive inheritance.

Adult↗
PubMed1989

Hand muscle reflexes following electrical stimulation in choreatic movement disorders.

Thenar reflexes following electrical stimulation of the median nerve (containing proprioceptive and cutaneous afferents) and the radial superficial nerve (cutaneous afferents only) were investigated in 23 patients with manifest Huntington's disease (HD) at an early stage, in 17 clinically healthy descendants of HD-patients and in 18 patients with choreatic hyperkinesia due to various aetiologies other than HD. In 61% of the patients with early HD the long-latency reflexes (LLR) were uni- or bilaterally absent in response to both median nerve and radial superficial nerve stimulation. The remaining patients had a diminished mean amplitude and mean duration of their LLR. In contrast, offspring and patients with symptomatic chorea had preserved LLR which did not differ in amplitude or duration from normal controls. Additionally, the mean amplitude and mean duration of the Hoffmaan-reflex (HR) was found to be increased in patients with HD and their offspring but not in patients with other aetiologies. It is concluded (1) that the loss of LLR is not related to the choreatic hyperkinesia itself but to the degeneration of a hitherto poorly defined neuronal circuit in HD; (2) that among a variety of diseases presenting with chorea, the loss of LLR seems to be specific for HD; (3) that the testing of hand muscle reflexes in choreatic movement disorders is helpful for the differential diagnosis of early HD but not for the detection of gene carriers among offspring of patients with HD.

Afferent Pathways↗
PubMed1990

Pathological stretch reflexes on the "good" side of hemiparetic patients.

The reflex EMG responses from a tendon tap or an imposed, medium amplitude (30 degrees), stretch at a range of stretch velocities have been recorded from the triceps and biceps muscles of normal human subjects and in both the affected and "unaffected" arms of hemiparetic patients under relaxed conditions. In the hemiparetic arm, exaggerated tendon jerks were, as expected, observed in both muscles. The response of the biceps to elbow extension was also exaggerated compared with normal values and displayed both an additional earlier component and a much reduced velocity threshold. The triceps, in contrast, showed depressed responses to elbow flexion, with a much higher velocity threshold than normal subjects. Furthermore, on the supposedly "unaffected" side of the hemiparetic subjects, the reciprocal pattern was seen, with depression of the biceps response and a raising of its threshold, along with considerably exaggerated responses in the triceps including earlier components not seen in the normal subjects. The increased excitability of the flexor musculature on the spastic side may be paralleled by increases in activity in the segmental pathways responsible for modulation of agonist/antagonist activity in the ipsi and contralateral limb, leading to an inhibition of the ipsilateral extensors and contralateral flexors and excitatory input to the contralateral extensors. Thus the "good" side of hemiparetic patients also receives pathological changes, and studies of the mechanisms of spasticity should avoid the use of the "unaffected" side of hemiparetic subjects as a control for monitoring pathological reflexes.

Adult↗
PubMed1990

Observations on the reflex effects seen in Parkinson's disease on terminating a period of tendon vibration.

Vibration was applied to the tendon of flexor carpi radialis while recording the EMG of the wrist flexors in 29 Parkinsonian patients. Cessation of the vibration led to a small short-latency (approximately 25 ms) reduction in the level of activity which did not differ in magnitude from the normal. Moreover, there was no sign of any subsequent long-latency reduction of activity. Thus the maintained tonic activity of Parkinsonian muscles seems unlikely to be due to an enhancement of the tonic reflex actions of the Ia afferents, especially via the short-latency pathway. In addition, the findings argue against reduction of either Ia or Ib firing being responsible for the delayed excitatory "Westphal" (or "shortening") response that may occur in parkinsonism on allowing a muscle to shorten; this was never found on terminating vibration, even when present on muscle release.

Afferent Pathways↗
PubMed1998

Hyperekplexia and trismus due to brainstem encephalopathy.

The brainstem is said to be the generator of pathological startle responses due to reticular reflex myoclonus or hyperekplexia. A patient with facial weakness, nystagmus, and pyramidal tract signs had generalised reflex spasms in response to auditory, visual and tactile stimuli which clinically and neurophysiologically resembled hyperekplexia. The case is unusual because as well as hyperekplexia, the patient's initial presentation was with an equally rare manifestation of brainstem pathology-brainstem mediated trismus. The causes of brainstem trismus and exaggerated startle responses are discussed with respect to their underlying mechanisms.

Brain Diseases↗