Mise en évidence et mesure d'une activité antiréserpine au niveau central au moyen du réflexe de clignement à la lumière

Reserpine induces an important enhancement of the light blink reflex in rabbits, which results from a central action. Psychotropic drugs (tricyclic antidepressant agents, amphetamine, chlorpromazine, chlorprothixene ) were administered by slow intravenous infusion to reserpinized rabbits (0.1 mg/kg, i.v., 2 h previously) until the blink reflex had disappeared. The proposed method does not display particular specificity but is suitable for measurement of antireserpine activity at the central level.

     

Clinical symptoms of bilateral anterior cerebral artery territory infarction

Bilateral anterior cerebral artery (ACA) territory infarction is rare and its associated symptoms are still not well understood. We evaluated the clinical symptoms of four patients with bilateral ACA infarction. The common clinical features were various primitive reflexes and parkinsonian symptoms including akinesia, rigidity and hypophonia. Frontal release signs were present in all patients with ACA infarction even without direct involvement of the prefrontal cortex. Enhanced glabellar tap response, previously not reported in patients with ACA infarction, was the most consistent finding, and electrophysiological studies confirmed hyperexcitability of the late component of the blink reflex. The bilateral lesions in the deep white matter may be associated with the observed symptoms, reflecting functional disconnection of the medial prefrontal-subcortical circuitry.     

Dynamic eyelid reconstruction in facial nerve palsy

The consequences of facial nerve palsy and the secondary inability of eyelid closure and blink may lead to devastating complications for the patient, including blindness. Reconstruction techniques to improve eyelid position and function can be broadly classified into ‘static’ and ‘dynamic’ techniques. Generally, ophthalmologists have been familiar with static procedures such as upper eyelid loading, tarsorrhaphy, canthoplasty, and lower eyelid suspension. Recently, dynamic techniques are being increasingly described for patients who require definitive strategies to improve eyelid function, once the initial critical goals of corneal protection and vision preservation have been achieved. The choice of technique(s) is dependent upon the status of the main protractor of the eyelid region, as well as the age of the patient, the patient’s morbidities and expectations, and surgeon preference. This review shall first describe the clinical and surgical anatomy relevant to the ophthalmic consequences of facial paralysis and discuss methods of defining function and outcomes. A comprehensive review of dynamic eyelid reconstruction is then presented with a discussion of the literature. These various techniques may not be familiar to all clinicians. It is important that ophthalmic surgeons are aware of all options available for their patients. Furthermore, eye care providers must have an understanding of when referral may be appropriate to provide timely intervention and optimal chances of recovery.     

Blink reflex recovery cycle distinguishes essential tremor with resting tremor from de novo Parkinson's disease: An exploratory study

An increased R2 recovery component of the blink reflex (R2-BRrc) has been observed in Parkinson's disease (PD), cranio-cervical dystonia, dystonic tremor and essential tremor with associated resting tremor (rET), while the BRrc was reported normal in patients with essential tremor (ET). Distinguishing rET from tremor dominant PD (tPD) may be challenging especially in the first stages of the diseases, in the absence of DAT-SPECT investigation. We evaluated the possible usefulness of BRrc for differentiating subjects with de novo tPD from those with rET. We investigated R2-BRrc at interstimulus intervals (ISI) of 100, 150, 200, 300, 400, 500 and 750 ms in 11 participants with tPD, 10 with rET and 20 healthy controls. All participants underwent DAT-SPECT and cardiac MIBG scintigraphy.R2 recovery was significantly enhanced in tPD compared to controls at all investigated ISIs (p < 0.001), while in subjects with rET patients BRrc was significantly increased compared to controls at ISI 150, 200, 300, 400, 500 and 750 ms (p < 0.001).At ISI 100 R2-BRrc distinguished patients participants with de novo tPD from those with rET with a sensitivity, specificity and accuracy of 100%. Our findings demonstrate the usefulness of BRrc for differentiating de novo tPD from rET.     

The distribution of primary afferent terminals from the eyelids of macaque monkeys

 Trigeminal sensory afferents from the eyelids convey two types of information that are important for the blink reflex. Movement of the lashes activates low-threshold mechanoreceptors which evoke protective blinks. Information about eyelid position is also transmitted centrally and is used to adapt the metrics of the blink reflex to changing conditions over time. This study employed transganglionic transport of horseradish peroxidase conjugated to choleratoxin-B subunit or wheat-germ agglutinin to investigate trigeminal afferents supplying the eyelids of macaque monkeys. Ganglion cells labeled from upper- and lower-lid injections were located in the ophthalmic and maxillary portions of the trigeminal ganglion, respectively. In both cases, labeled terminals were observed ipsilateral to the injected eyelid in the principal and spinal trigeminal nuclei. However, only a few labeled terminals were present in the principal nucleus, and very sparse terminal labeling was confined to a few locations along the ventral border of the pars oralis and interpolaris of the spinal trigeminal nucleus. The main concentration of label was found in the pars caudalis at and immediately below the spinomedullary junction. The terminal field from the upper eyelid was located ventrally in the pars caudalis, and that from the lower eyelid was located more dorsally. In both cases, the labeled terminal field was densest within lamina II of the spinal trigeminal nucleus. The heavy concentration of eyelid central terminals at the spinomedullary junction is surprising in light of physiological studies indicating representation of all parts of the face throughout the trigeminal nucleus. The distribution of eyelid afferent terminals in the macaque is caudal to the main concentration of corneal afferent terminals at the pars interpolaris/caudalis border. This may be a basis for differences seen in blinks produced by corneal as opposed to supraorbital stimulation. The presence of a single major site of eyelid primary afferent terminals suggests that sensory input for both eyelid proprioception and blink-reflex activation passes through this segment of the spinal trigeminal nucleus. These results provide a basis for investigation of the central connections of pars caudalis neurons in order to better establish the pathways producing trigeminally evoked blinks and blink adaptation. Received: 6 April 1998 / Accepted: 9 June 1998     

Counteracting driver sleepiness: Effects of napping, caffeine, and placebo

Sleepy drivers should “take a break,” but the efficacy of feasible additional countermeasures that can be used during the break is unknown. We examined a shorter than 15 min nap, 150 mg of caffeine in coffee, and a coffee plalcebo, each given randomly across test sessions to 10 sleepy subjects during a 30-min rest period between two 1-hr monotonous early afternoon drives in a car simulator. Caffeine and nap significantly reduced driving impairments, subjective sleepiness, and electroencephalographic (EEG) activity indicating drowsiness. Blink rate was unaffected. Sleep during naps varied, whereas caffeine produced more consistent effects. Subjects acknowledged sleepiness when the EEG indicated drowsiness, and driving impairments were preceded by self-knowledge of sleepiness. Taking just a break proved ineffective.     

Speaking,thinking, and blinking

The effect of several mental tasks on the spontaneous eye blink rate in 36 normals was examined. The blink rate during silence was 19.0 blinks/ minute. This was significantly lower than the mean blink rate during speech (24.7 blinks/minute) and while listening to a paragraph to be memorized (27.6 blinks/ minute). Reading reduced the blink rate to 12.3 blinks/ minute. Men were more able to suppress and speed up blinking than women.     

Blink reflex elicited by auditory stimulation: clinical study in newborn infants

Blink reflex can be elicited by sudden strong auditory stimulation. Using a special transducer wer recorded this reflex which appears as a microvibration of the eyelid, and named it auditory-evoked eyelid microvibration (AMV). As the reflex pathway of AMV exists in the brainstem, AMV is an easy and useful way of knowing the function of the brainstem, especially in newborn periods. AMV was studied in infants from 25 to 43 weeks in conceptional age, to establish the normal value and to analyse the change of AMV in cases of neonatal asphyxia and intracranial hemorrhage. The mean latency of AMV in full-term infants was 31.0 +/- 67. msec. After 33 weeks in conceptional age, AMV was observed constantly with almost the same latency and amplitude as adult values. AMV appeared during both waking and sleep stages, except in active sleep. Marked change in AMV was noted such as delayed latency or disappearance of the response in neonatal asphyxia or intracranial hemorrhage. Infants who continued to have these abnormalities for a certain period, died or exhibited neurological sequelae.