Postural Tone Research Articles

Contribuição dos grandes vasos arteriais na adaptação cardiovascular a ortostase

The capacity of adopting an orthostatic posture is, undoubtedly, a milestone in the evolution of the human species and has motivated extensive research in the physiological and anthropological areas. The physiological mechanisms involved in adopting and maintaining an orthostatic posture and its complications have been investigated through the centuries. The anatomists do not consider the postural adaptation of the human being a peculiar transformation that occurred to mankind, but the culmination of a series of evolutionary phases that might have started in the body of the primate ancestors 1 . It is believed that the human cardiovascular system is adapted to maintain cerebral perfusion during the orthostatic posture. Although the gravitational force creates a gradient of pressure at the level of the circulatory system, the human being is capable of maintaining an upright posture because the gravitational pressure is partially neutralized by mechanisms that prevent the accumulation of flin the lower limbs 2 . Despite that, syncope, defi ned as a transient loss of consciousness and postural tonus due to cerebral hypoperfusion, has a considerable medical, social and economical impact. This clinical syndrome can be the consequence of not only refl ex mechanisms3, but also a clinical manifestation of a broad range of distinct clinical conditions 4 . A perspective of the cardiovascular adaptation to orthostatism is presented herein, in an attempt to assess evolutionary and physiological issues regarding the maintenance of circulatory homeostasis during orthostasis, stressing the role of the great arteries.

Postural Muscle Tone in the Body Axis of Healthy Humans

Across the entire human body, postural tone might play its most critical role in the body's axis because the axis joins the four limbs and head into a single functioning unit during complex motor tasks as well as in static postures. Although postural tone is commonly viewed as low-level, tonic motor activity, we hypothesized that postural tone is both tonically and dynamically regulated in the human axis even during quiet stance. Our results describe the vertical distribution of postural muscle tone in the neck, trunk, and hips of standing human adults. Each subject stood blindfolded on a platform that axially rotated the neck, trunk, or pelvis at 1 degrees /s and +/-10 degrees relative to the neutral position (i.e., facing forward). The measured resistance to axial rotation was highest in the trunk and lowest in the neck and was characterized by several nonlinear features including short-range stiffness and hysteresis. In half of the subjects, axial muscle activity was relatively constant during axial rotation, and in the other half, muscle activity was modulated by lengthening and shortening reactions, i.e., decreasing activity in lengthening muscles and increasing activity in shortening muscles, respectively. Axial resistance to rotation was reduced in subjects whose muscle activity was modulated. The results indicate that axial tone is modulated sensitively and dynamically, this control originates, at least in part, from tonic lengthening and shortening reactions, and a similar type of control appears to exist for postural tone in the proximal muscles of the arm.

An investigation of flumazenil to antagonize gamma-hydroxybutyrate intoxication in a murine model

Prior animal studies have suggested that flumazenil may blunt GHB's sedative-hypnotic affects. We hypothesized that flumazenil would decrease the affects of GHB in a murine model of intoxication. We performed a controlled, pilot experiment using 32 mice divided into 3 groups. All mice received intraperitoneal injections of GHB (1.5 g/kg). Group I received sham injections at time 0, and then GHB at 5 minutes. Group II received flumazenil (0.3 mg/kg) at time 0, and then GHB at 5 minutes. Group III received sham injection at time 0, then GHB at 5 minutes, and then 4 escalating flumazenil doses administered at 3-minute intervals (0.003 to 1 mg/kg). We measured certain functions: time to loss/recovery of righting reflexes (RR), time to sprawl/recovery of sprawl (postural tone [PT]), and death. There were statistically significant delays in the loss of PT and shortened recovery time to RR in pre-treated mice (group II) versus controls (group I). There were no differences in group III versus group I for any outcome parameters. In this model, pre-dosing flumazenil prior to GHB administration delayed clinical intoxication.

Psychogenic pseudosyncope: An underestimated and provable diagnosis

Objective The goal of this study was to estimate the frequency of psychogenic pseudosyncope in patients with “syncope of unknown origin.” Twenty to thirty percent of patients referred to epilepsy centers for refractory seizures have psychogenic seizures. With syncope, about 20–30% of the cases remain unexplained after a complete evaluation, but, unlike in seizures, a psychogenic etiology is not usually investigated. Methods We prospectively evaluated patients referred to our epilepsy center for evaluation of recurrent syncope-like episodes, that is, limp, motionless fainting. All patients had a negative syncope workup. We performed EEG-video monitoring with activation by suggestion (“induction”), similar to what is used for diagnosis of psychogenic seizures. Activation was performed with patients standing or sitting up. The diagnosis of psychogenic pseudosyncope required: (1) an activation procedure that triggered the habitual event; (2) a clinical event of loss of postural tone and limp, motionless unresponsiveness with eyes closed; (3) normal EEG before, during, and after the clinical event, that is, no epileptiform abnormalities, a normal α rhythm during unresponsiveness, and no suppression of background or slowing as is typically seen in syncope. Results Ten patients were recruited over an 18-month period. Habitual syncope-like episodes were triggered in 9 of 10 (90%) patients, and all 9 were shown to have psychogenic pseudosyncope (eyes closed, motionless, unresponsive with normal EEG including normal α rhythm). In one patient, no episode was triggered, so a diagnosis could not be made. Among the 9 patients for whom episodes were recorded, age ranged from 21 to 60 (mean = 36). Five were women. Duration of symptoms ranged from 6 months to 15 years (mean = 4.2 years). Event frequency ranged from four per day to two per month. Prior evaluations for syncope included ECG in all patients, two-dimensional echocardiogram in three, Holter monitoring in two, and tilt-table test in five. Four patients had undergone cardiac catheterization, and one had received a pacemaker. Neurologic tests included CT of the head in seven and MRI of the brain in eight. Conclusion Many patients with “syncope of unknown origin” may have psychogenic pseudosyncope, but most such patients do not undergo EEG-video monitoring, which is the only way to demonstrate a psychogenic etiology. Psychogenic pseudosyncope is not simply a diagnosis of exclusion, and can be firmly diagnosed. As is usually recommended for seizure-like events, patients with syncope-like events and a negative evaluation should undergo EEG-video monitoring with induction, specifically looking for a possible psychogenic etiology.

Management of Syncope Following Immunization

Mary S. Hayney lowing immunization.1 From 1990 to 1995, a total of 697 reports of syncope were made (Table 2). Of particular note is the timing of the episodes. This timing may guide immunizers to ask their patients to remain seated and under observation for 15 minutes following immunization. Although nearly one fourth of the VAERS reports included a mention of rhythmic movements with loss of consciousness, none of the reports noted that a new seizure diagnosis was made. The authors speculated that since the tonic or clonic jerking movements were more likely to be reported for syncopal episodes within 15 minutes of immunization, these are more likely to be vasovagal responses rather than seizures. Most episodes of syncope are harmless, and the real issue is the fall associated with the loss of consciousness and postural tone. Six individuals in the Braun et al. study sustained serious head injuries during the syncopal episode.1 The affected individuals were older (aged 12 to 28 years) than the group overall, and they were therefore heavier than a young child—giving credence to the saying, “The bigger they are the harder they fall.” Also, of particular importance to immunizers is that five of the six fainters were adolescent boys and men. Because fainting is perceived as less acceptable for men in our society, they may be less likely to admit to presyncopal signs (see below). They may even Syncope occurs in a situation the patient perceives as distressing. Although no data are available, one could reasonably assume that known fainters are unlikely to seek immunization services in a pharmacy. The key issue though is that fainting can be unpredictable. Syncope with immunization has not been systematically studied, but it occurs, and individuals with a fear of needles sometimes selfdefer immunization.1,2

Helmet and Gloves

Helmet and Gloves

Neurocardiogenic Syncope: Mechanisms, Evaluation and Treatment

Syncope is the abrupt and transient loss of consciousness due to a temporary reduction in cerebral blood flow, associated with an absence of postural tone, followed by a rapid and usually complete recovery. It may result from several possible etiologies, ranging from the benign to the potentially fatal. Neurocardiogenic (vasovagal) syncope is the most common of a group of neurally mediated syncopes, characterized by a sudden failure of autonomic regulatory mechanisms to maintain adequate blood pressure and, occasionally, heart rate, to sustain cerebral perfusion and consciousness. The diagnosis may be suggested by a characteristic history and by exclusion of other causes of syncope; however, in some cases, upright tilt table testing may be required to provoke typical hemodynamic responses. Cardiologists and cardiac electrophysiologists are frequently expected to manage patients with suspected neurocardiogenic syncope. The following review aims to provide a basic framework for understanding its pathophysiology, clinical presentations, diagnosis and treatment.

Isolated paroxysmal arousals as focal epilepsy

ABSTRACT Paroxysmal motor phenomena and arousals during sleep are frequent. The differential diagnoses between benign hypnic transient events, epileptic and non‐epileptic seizures represent a common clinical problem. Video‐EEG monitoring during sleep, recording several episodes in the same patient, is essential in order to characterize these phenomena. It offers the possibility to compare electro‐clinical data, to demonstrate the eventual stereotyped pattern of motor phenomena and their progression in time, and to study EEG‐polygraphic correlates. The recently described double split‐screen synchronized display (DSSSD) technique represents a useful tool for comparing particular clinical patterns of epileptic seizures when dealing with complex, hypermotor phenomena observed in frontal lobe epilepsy. We reviewed the data of 24 patients admitted during a two‐year period (2002‐2003) to our epilepsy sleep unit for isolated paroxysmal sleep motor events. Four patients presented with very brief paroxysmal arousals without daytime fits. Three of our patients presented isolated paroxysmal arousals, whereas in one, the events were associated with hypermotor seizures. We present a simplified variant of the DSSSD method (modified DSSSD) that can be used to study episodes of paroxysmal arousals in order to confirm their stereotyped motor pattern. The clinical aspects and the EEG‐polygraphy patterns were informative, with the absence of asymmetrical tonic or dystonic posturing of the limbs. Scalp EEG alone does not usually provide much information in patients with isolated paroxysmal arousals. Coupled to the modified DSSSD technique, it may allow confirmation of the diagnosis of frontal epilepsy, as was the case in our four patients. [Published with video sequences]

Utilidad de la tizanidina. Seguimiento de un año en el tratamiento de la espasticidad en la parálisis cerebral infantil

The cerebral palsy has the first place of physical handicap in children (type spastic, 88%). Tizanidine imidazole derivative is centrally acting as a a2-adrenergic agonist. To demonstrate clinically the effectiveness of tizanidine in the decrease of the spasticity. We assigned randomly in a double blind study 10 children treated with tizanidine (0.05 mg/kg/day) and 30 with placebo for a 6-month period, after which they were unified in the group of tizanidine. The dependent variables were spasticity, Ashworth scale, posture tone scale, reflex scale and liver function test. The spasticity and the reflex decreased in the group of tizanidine an 78.85% in comparison with a 7.64% in the group of placebo (p = 0.0001); in the monitoring of 6 months 35 patients reduced this to 78.2% (p= 0.0001). The duration of effectiveness of tizanidine in four patients was two months and they never returned to their appraisal basal. Without reported adverse effects, the liver function test remains normal. Tizanidine produces a significant reduction of the spasticity in children without adverse effects, having a high percentage of acceptance to the prescribe dose.

Orexinergic projections to the cat midbrain mediate alternation of emotional behavioural states from locomotion to cataplexy

Orexinergic neurones in the perifornical lateral hypothalamus project to structures of the midbrain, including the substantia nigra and the mesopontine tegmentum. These areas contain the mesencephalic locomotor region (MLR), and the pedunculopontine and laterodorsal tegmental nuclei (PPN/LDT), which regulate atonia during rapid eye movement (REM) sleep. Deficiencies of the orexinergic system result in narcolepsy, suggesting that these projections are concerned with switching between locomotor movements and muscular atonia. The present study characterizes the role of these orexinergic projections to the midbrain. In decerebrate cats, injecting orexin-A (60 microm to 1.0 mm, 0.20-0.25 microl) into the MLR reduced the intensity of the electrical stimulation required to induce locomotion on a treadmill (4 cats) or even elicit locomotor movements without electrical stimulation (2 cats). On the other hand, when orexin was injected into either the PPN (8 cats) or the substantia nigra pars reticulata (SNr, 4 cats), an increased stimulus intensity at the PPN was required to induce muscle atonia. The effects of orexin on the PPN and the SNr were reversed by subsequently injecting bicuculline (5 mm, 0.20-0.25 microl), a GABA(A) receptor antagonist, into the PPN. These findings indicate that excitatory orexinergic drive could maintain a higher level of locomotor activity by increasing the excitability of neurones in the MLR, while enhancing GABAergic effects on presumably cholinergic PPN neurones, to suppress muscle atonia. We conclude that orexinergic projections from the hypothalamus to the midbrain play an important role in regulating motor behaviour and controlling postural muscle tone and locomotor movements when awake and during sleep. Furthermore, as the excitability is attenuated in the absence of orexin, signals to the midbrain may induce locomotor behaviour when the orexinergic system functions normally but elicit atonia or narcolepsy when the orexinergic function is disturbed.

Clinical Neurophysiology: EEG–Video Monitoring

Clinical Neurophysiology: EEG–Video Monitoring

Understanding and Managing Neurally Mediated Syncope in the Adolescent

Syncope and near-syncopal symptoms are common events in the adolescent population. Syncope is defined as the transient loss of postural tone and consciousness with spontaneous recovery. Although most syncopal events are benign, they can generate extreme anxiety in the adolescent and his or her family. The re-occurrence of these events can have a negative impact on an adolescent's participation in daily activities. Understanding the process of assessment, diagnosis, and management of these teens can enable the school nurse to augment initial assessment and to support the prescribed treatment plan. This knowledge then can be used to help allay the adolescent's anxiety and to support efforts at self-management. This article explores current literature in regards to etiology, diagnosis, and medical treatment, and advocates a self-management protocol for neurally mediated syncope in the adolescent population with support of that plan by the school nurse.

Discharge of identified orexin/hypocretin neurons across the sleep-waking cycle.

Although maintained by multiple arousal systems, wakefulness falters if orexin (hypocretin), orexin receptors, or orexin neurons are deficient; narcolepsy results with hypersomnolence or sudden onset of rapid eye movement sleep [or paradoxical sleep (PS)] and loss of muscle tonus. To learn how orexin neurons maintain wakefulness, we recorded neurons in head-fixed rats across the sleep-waking cycle and then labeled them with Neurobiotin to identify them by immunohistochemistry. We show that identified orexin neurons discharge during active waking, when postural muscle tone is high in association with movement, decrease discharge during quiet waking in absence of movement, and virtually cease firing during sleep, when postural muscle tone is low or absent. During PS, they remain relatively silent in association with postural muscle atonia and most often despite phasic muscular twitches. They increase firing before the end of PS and thereby herald by several seconds the return of waking and muscle tone. The orexin neurons would thus stimulate arousal, while antagonizing sleep and muscle atonia.

Neonatal seizures with tonic clonic sequences and poor developmental outcome

Seizures consisting of a tonic followed by a clonic phase have rarely been described in neonates and are not included in the current classifications of neonatal seizures. Our video archive of 105 neonates with seizures or suspected seizures revealed six neonates with such tonic clonic or tonic myoclonic sequences. Two of those neonates had pyridoxine dependent seizures. The other four neonates had drug refractory seizures and demonstrated similarities in electro-clinical pattern, clinical course and outcome. Their seizures started with tonic posturing and after 10–20 s tonic posturing was superimposed by focal or multifocal cloni or myocloni. Ictal EEG started with voltage attenuation followed by bilateral or alternating focal epileptic discharges. The interictal EEG was abnormal. One child died, while the other three children became seizure free but had severe motor delay and mental retardation. In one of those three children, a de novo missense mutation was detected in the voltage gated potassium channel gene KCNQ2, indicating a genetic relationship between drug refractory neonatal seizures of unknown etiology with tonic clonic or myoclonic sequences and the well-known syndrome of benign familial neonatal convulsions (BFNC).

Differential effect of sleep-wake states on lingual and dorsal neck muscle activity in rats

Postural tone is reduced during slow-wave sleep (SWS) and absent during rapid eye movement sleep (REMS). In obstructive sleep apnea subjects, upper airway dilating muscles, including those of the tongue, show a similar pattern; this contributes to sleep-related airway obstructions. However, in healthy subjects, state-dependent changes in the activity of pharyngeal muscles are variable. In seven chronically instrumented Sprague-Dawley rats, an animal model used to study sleep and sleep-disordered breathing, we quantified lingual and postural muscle activity across the sleep-wake states by measuring the root mean square levels of the electromyograms (EMG) in successive 10s intervals collected during 2h of recording at a constant circadian time (1-3p.m.). The nuchal EMG was low and steady during SWS and further reduced with occasional twitches during REMS. In contrast, the mean lingual EMG during SWS was only 5.9+/-1.6% (S.E.) of its mean in wakefulness, and during REMS, it increased to 46+/-15% (S.E.) (p<0.03) due to the appearance of phasic bursts, the intensity of which progressively increased. The lingual and nuchal activities also had different time courses during state transitions. In obstructive sleep apnea subjects, the sleep-wake changes in the activity of pharyngeal muscles may become similar to those in postural muscles as a result of pharyngeal tone adaptations to the disorder.

Neurocardiogenic Syncope and Related Disorders of Orthostatic Intolerance

Received September 14, 2004; revision received January 31, 2005; accepted March 9, 2005. “We shall not cease from exploration and the end of all our exploring will be to arrive where we started and know the place for the first time” — —T.S. Eliot, Four Quartets Syncope, defined as transient loss of consciousness and postural tone with spontaneous recovery, has both challenged and perplexed physicians since the dawn of recorded time. The earliest written accounts come from Hippocrates, and the word syncope itself is derived from an old Greek term meaning “to cut short” or “interrupt.” Recurrent episodes of syncope may result from a large number of different disorders, all of which cause a transitory reduction in cerebral blood flow sufficient to disturb the normal functions of the brain. Over the last 2 decades, considerable attention has been given to types of syncope that occur due to a centrally mediated (or “reflex”) fall in systemic blood pressure, a condition that has been referred to as vasovagal (and later neurocardiogenic) syncope. However, research into the nature of this disorder revealed that it is but one aspect of a broad and varied group of disturbances in the normal functioning of the autonomic nervous system (ANS), each of which may result in orthostatic intolerance, hypotension, and ultimately syncope. Continued investigations into the nature of these similar yet different disorders has led to the development of a system of classification that attempts to more accurately reflect our understanding of these conditions and their interrelationships.1 The present system of classification has proven both functional and clinically relevant and includes a group of disorders that most investigators have thought to be principally autonomic in nature. Because both the cardiologist and the cardiac electrophysiologist frequently are expected to both diagnose and treat these conditions, the following …

18.21 Backward disequilibrium in elderly who fall: Exaggerated postural tone of the extensor muscles or tilted biological vertical?

18.21 Backward disequilibrium in elderly who fall: Exaggerated postural tone of the extensor muscles or tilted biological vertical?

Free Communications: Surgery

Abstract Ictal SPECT in Supplementary Motor Area Seizure. 1 Masafumi Fukuda, 2 Hiroshi Masuda, 2 Junpei Honma, 2 Ayataka Fujimoto, 2 Shigeki Kameyama, and 1 Ryuichi Tanaka ( 1 Department of Neurosurgery, Brain Research Institute, University of Niigata 2 Department of Neurosurgery, Epilepsy Center, Nishi-Niigata-Chuo National Hospital, Niigata, Japan ). Purpose: The clinical semiology of supplementary motor area (SMA) seizures is characterized by abrupt, bilateral, tonic posturing of the extremities, vocalization, mostly preserved consciousness, and short duration. The SMA has multiple reciprocal connections with the primary sensorimotor cortex (SMC), anterior cingulate cortex (ACC), and various parietal somatosensory areas. Therefore, the epileptic discharges from SMA can rapidly propagate to these structures. In the present study, we used ictal SPECT to clarify the propagation pathways of epileptic discharges in patients with SMA seizures who were evaluated with chronic subdural electrodes for a definite localization of the seizure onset zone. Methods: We studied four patients (four males; age range, 18–27 years) with SMA seizures. The seizures occurred 1–10 times per day and lasted for 10–15 seconds. In two patients, proton magnetic resonance (MR) imaging revealed a hyperintense lesion indicative of focal cortical dysplasia (FCD) in the right SMA, where subdural electrode monitoring also localized the ictal onset. After complete resection of the FCD including the epileptic foci, these patients remained seizure free. In the other two patients, MR images were normal, but subdural electrode monitoring permitted verification of ictal onset in the left SMA. After partial resection of the SMA, including the epileptic foci, these patients experienced a significant (>90%) reduction of seizure frequency and were classified as class IIB outcome according to Engel's classification. SPECT studies were performed in all patients as a preoperative evaluation. Ictal SPECT was performed during seizures that occurred while the patients were undergoing inpatient video-EEG monitoring. The radioisotope 99mTc-ECD was injected immediately after seizure onset. The interval from seizure onset to the time of injection was no more than 3 seconds. Ictal and interictal SPECT images were acquired within 30 minutes after radioisotope injections. Regional cerebral blood flow (rCBF) measurements obtained under ictal and interictal conditions were compared on a voxel-by-voxel basis using the paired t-test option in SPM99. Images from the two patients with no lesions on MR images were reversed such that the hemisphere having epileptic foci appeared on the right. The changes were considered significant when the p-value was less than 0.001, uncorrected for multiple independent comparisons. Results: SPM analysis revealed significant increases of rCBF in bilateral ACC (x= 10, y=–6, z= 44 mm; Zmax= 4.97 and x=–18, y=–20, z= 42; Zmax= 4.49), the right globus pallidus (x= 20, y=–2, z= 2; Zmax= 4.23), and the cerebellar hemisphere (x=–26, y=–48, z=–38; Zmax= 4.22) in ictal condition. The right ACC contained a cluster with a submaximum in the right primary SMC (x= 36, y=–18, z= 46; Z= 4.35). No reduction in rCBF was observed in ictal condition. Conclusions: In patients with SMA seizures, hyperperfusion areas depicted on ictal SPECT did not localize within the SMA but spread to the adjacent cortex such as ACC and SMC ipsilateral to the epileptic foci. Additionally, epileptic discharges propagated to remote areas such as the globus pallidus and cerebellum that have direct or indirect reciprocal connections with the SMA. We caution that in patients with SMA seizures, ictal SPECT localization is not always concordant with epileptogenic foci but reveals already spread seizure activities.

Summary and Agreement Statement of the 2nd International Conference on Concussion in Sport, Prague 2004

In November 2001, the 1st International Symposium on Concussion in Sport was held in Vienna, Austria to provide recommendations for the improvement of safety and health of athletes who suffer concussive injuries in ice hockey, football (soccer), and other sports. The 2nd International Symposium on Concussion in Sport was organised by the same group and held in Prague, Czech Republic in November 2004. It resulted in a revision and update of the Vienna consensus recommendations, which are presented here.

Tratamiento fisioterapéutico en esclerosis múltiple: a propósito de un caso clínico

The goal of this article is to present an alternative for the Physical Therapy treatment, based on the Bobath Concept, of a young pacient who is afected with Multiple Sclerosis. For that, the treatment was developed in 30 to 40 minute sessions, three to four times a week during six months. As many of the problems that the patients with Multiple Sclerosis have a postural tonus disfunction as well as the reciprocal inervation, balance and righting reactions and so on, the therapeutical approach is based on the Bobath Concept, since this approach can offer many therapeutical tools for reeducating these simptoms. After six months, the patient experiments either a qualitative increase in the postural tonus and sensibility, and a quantitative in the balance reactions (14 points in the Tinetti Scale), and in the daily living activities that were measured with the Katz Index (B) and the Barthel Index (80 points). Analizing the results, we can conclude that from the caracteristics and the problems present by the Multiple Sclerosis patients, the Bobath Concept is a good approach for the Physical Therapy treatment in these patients.