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PubMed1984

Impairment of cardiovascular autonomic reflexes in multiple symmetric lipomatosis.

Cardiovascular autonomic reflexes were evaluated in 13 male subjects affected by Multiple Symmetric Lipomatosis (MSL) and the results were compared with those obtained in 13 age-matched male controls and in 16 male heavy drinkers matched with the MSL group for age and alcohol intake. Valsalva Manoeuvre (VR), Heart Rate variations on Deep Breathing (DB) and R-R intervals 30/15 ratio during Lying-to-Standing (LS) (tilting), were used as primarily parasympathetic tests. As primarily sympathetic tests, we assessed the increment of diastolic blood pressure in Sustained Handgrip (SHG) and the fall of systolic blood pressure on standing (Postural Hypotension = PH). Mean values of VR and DB were significantly (P less than 0.001) lower in MSL subjects than in controls and heavy drinkers. Mean LS values were significantly lower in MSL subjects (P less than 0.001) and in heavy drinkers (P less than 0.01) in relation to controls. No significant differences were observed in the 3 groups of subjects regarding the mean values of PH and SHG. The results suggest that MSL is characterized by an impairment of autonomic function. This impairment seems to be prevalently parasympathetic and not related to a high alcohol intake.

Adult↗
PubMed1987

Maintenance of constant arm position or force: reflex and volitional components in man.

1. Normal subjects, with closed eyes, attempted to keep constant either the force exerted at the wrist or the position of the wrist against an elastic load. The load was attached to the wrist 275 mm from the axis of rotation of the elbow joint. During recording, the far end of the elastic load was displaced slowly enough that it was not immediately perceived but far enough for perception to occur before its completion. 2. The over-all relation between wrist force and position for the two conditions was approximately linear and could be described in terms of effective stiffness. The effective stiffness for the constant-position task averaged 2.8 N/mm (210 N m/rad), while for the constant-force task the mean effective stiffness was -0.028 N/mm (-2.1 N m/rad), indicative of slight over-compensation. 3. Averaging the performance at the onset of the imposed disturbance indicated that the subjects' behaviour consisted of two parts: an initial, small-range response followed by a second phase over the remainder of the displacement. The transition corresponded to the subjects' threshold for detection of the disturbance. 4. The stiffness measured for the response prior to perception was taken as a measure which included the tonic stretch reflex. The stiffness was altered appropriately for the two tasks, being lower when the subjects tried to maintain the force exerted constant (average 1.1 N/mm, 83 N m/rad) than when they attempted to keep the position constant (average 2.3 N/mm, 170 N m/rad). A small degree of co-contraction occurred but could be dissociated from the stiffness changes. 5. Scaling the results allowed comparison of the initial stiffness with values for the decerebrate cat. When analysed in this way, the values recorded in man during the constant-position task were similar to those reported for short-range stiffness in the decerebrate cat. 6. The thresholds for detection of the disturbance were much lower than those reported for subjects with relaxed muscles. 7. The stretch reflex in man has a direct role in compensating for small disturbances during motor tasks. It may also function to improve detection of applied disturbances by magnifying the corresponding force change. Once the stimulus is perceived and voluntary intervention is possible, a greater contrast is seen between the subjects' performance of the two tasks.

Arm↗
PubMedDate not supplied

Treatment of PAT. Bradycardiac reflexes induced by dive vs. body-tilt.

It has been suggested that the dive reflex (elicited by face immersion in water with breath-hold) may be employed to induce vagally-mediated bradycardia in individuals with paroxysmal atrial tachycardia. However, in several cases the use of this reflex is reported to have led to exacerbation of the cardiac dysfunction. Examination of heart-rate and EKG T-wave amplitude changes during the dive in healthy, college-aged individuals indicated that warming the water (10 degrees through 20 degrees C to 40 degrees C) decreased the bradycardia, but did not alter the attenuation (approximately 100 mu v) of the T-wave. The latter effect was taken to indicate that sympathetic activity, as indexed by T-wave amplitude, was not reduced by increases in water temperature. On the other hand, a 90 degrees head-up to head-down body tilt produced a bradycardia response of some 30 bpm as well as a T-wave amplitude increase (sympathetic withdrawal) in the order of 100 mu v. These data suggest that individuals who exhibit symptoms of ventricular sympathetic irritability may be adversely affected by the dive maneuver, regardless of water temperature. The body-tilt induced reflex in such individuals may thus be more appropriate given the large-magnitude bradycardia and absence of T-wave attenuation. At the present, however, the body-tilt preparation has been used only with healthy normal subjects, so this suggestion remains to be directly tested.

Adolescent↗
PubMed1994

Differential diagnosis of neuropathic lesions in diabetic and alcoholic patients.

Cardiovascular reflex tests are used extensively to screen diabetic patients for autonomic cardiac neuropathy. Since alcohol abuse must often be considered the cause of nerve damage in internally ill patients, we examined 66 nonalcoholic type 1 (insulin-dependent) diabetics and 63 nondiabetic alcoholics matched for age, weight, and duration of disease to determine whether specific patterns of complaints, symptoms, signs, and results of the cardiovascular reflex tests can differentiate between alcoholic and diabetic nerve damages. In these carefully selected diabetic and alcoholic patients the medical history, clinical neurological assessment, and reflex test results all showed significant differences, resulting in different patterns which allow the correct allocation of nerve damage to either diabetic or alcoholic origin with easily available clinical means.

Adolescent↗
PubMed2005

Do predictive mechanisms improve the angular vestibulo-ocular reflex in vestibular neuritis?

Recovery from vestibular neuritis (VN) is often incomplete which leads to persistent vestibular imbalance during rapid head movements. Patients with unilateral vestibular lesions have a larger gain of the horizontal vestibulo-ocular reflex during active compared to passive head movements. To test whether this gain increase is related to predictive mechanisms we studied 15 patients with VN and 14 control subjects during predictable and unpredictable passive horizontal head impulses in the light and darkness. The vestibulo-ocular reflex showed a significantly shorter latency and higher gain in the light for predictable head impulses towards the ipsilesional side. However, this effect is small and might contribute but cannot exclusively account for the gain increase during active head movements.

Adult↗
PubMed1983

An asymmetrical tonic neck reflex rating scale.

Although the asymmetrical tonic neck reflex (ATNR) is commonly used as one clinical assessment when evaluating children with suspected sensory integration deficits, maturational lags, or behavioral dysfunctions, observations are limited on the degree of this reflex in normal children at different age levels. A quantitative rating scale that indicates the degree of integration of the ATNR in normal first and third grade children is presented for purposes of comparison with the "suspect" child. A procedure for testing this reflex is described using the quadrupedal position, four sequences of lateral head rotation, and a rating scale consisting of four components. Using this ATNR rating scale, scores can be derived that could serve as a guide in determining whether the residual ATNR is comparable to that of normal subjects of the same age.

Child↗
PubMed1993

Level of arterial obstruction in patients with peripheral arterial occlusive disease (PAOD) determined by laser Doppler fluxmetry.

AIM: To evaluate the laser Doppler fluxmeter as a non-invasive screening method to determine the level of peripheral arterial occlusive disease (PAOD) in the lower limb. DESIGN: Open study of the veno-arterial reflex (VAR) during a shift in body position using a laser Doppler fluxmeter at five probe positions distal to the knee, compared with the occlusion level determined by arteriography and segmental plethysmography. MATERIALS: 50 legs comprising 10 normal controls, 20 legs with suprainguinal obstructions (10 claudication and 10 critical ischaemia) and 20 legs with infrainguinal obstructions (10 claudication and 10 critical ischaemia). RESULTS: Controls had normal VAR (mean flux reductions of 38% during dependency) at all probe positions. Legs with infrainguinal disease had normal reflexes proximally but significantly disturbed reflexes distally, whereas suprainguinal disease showed alterations at all sites. Claudicants had diminished flux reduction (mean 12%) whilst those with critical ischaemia increased the flux (mean 32%). CONCLUSION: This simple, non-invasive technique may be of use in determining the level of obstruction in PAOD.

Aged↗
PubMed1997

Sympathetic vasoconstrictor reflexes in Parkinson's disease with autonomic dysfunction.

Centrally and locally elicited sympathetic vasoconstrictor responses were examined in 12 patients with symptoms and signs of cardiovascular autonomic dysfunction due to Parkinson's disease. The sympathetic reflex mechanisms were measured in skeletal muscle and subcutaneous tissue of the arm and leg using the 133-Xenon washout technique. This method allows differentiation between local and central sympathetic reflexes in different tissues. The results indicate an abolished centrally mediated vasoconstrictor response in skeletal muscle in the arm and a decreased response in skeletal muscle in the leg and in subcutaneous tissue. This is in agreement with an autonomic dysfunction located in the central nervous system. A possible spinal sympathetic reflex controlling blood flow in subcutaneous tissue and leg muscles is considered. The sympathetic vasoconstrictor responses in parkinsonian patients without autonomic failure were of normal magnitude and the responses were not affected by long-term levodopa treatment.

Adult↗
PubMed2001

Voluntary and reflex influences on the initiation of swallowing reflex in man.

The electrophysiological features of voluntarily induced and reflexive/spontaneous swallows were investigated. In normal subjects, swallows were elicited by infusing water either into the mouth (1-3 ml) or directly into the oropharyngeal region through a nasopharyngeal cannula (0.3-1 ml). For water infused orally, subjects were either requested to swallow voluntarily or instructed to resist swallowing and maintain the horizontal head position until swallowing occurred reflexively. Spontaneous saliva swallowing was investigated in patients with severe dysphagia who had a prominent clinical picture of suprabulbar palsy. Comparisons between different swallowing types were made by measuring the time interval between the onset of submental electromyographic activity (SM-EMG) and the onset of the upward movement of the larynx recorded by a movement sensor. This interval was less than 100 ms, even frequently less than 50 ms, in reflexive/spontaneous swallows, while in voluntarily induced swallows it was substantially longer. The rising time of submental muscle's excitation was also shorter in reflexive/spontaneous swallows. It was suggested that the triggering of voluntarily induced swallows commences more than 100 ms before the onset of swallowing reflex and that this mechanism is under the control of corticobulbar-pyramidal pathways. If the swallowing reflex is triggered within such a short period of time following the onset of SM-EMG, the central control by the bulbar swallowing center should be effective until the end of oropharyngeal swallowing.

Adult↗
PubMed1985

Otoneurological examination in panic disorder and agoraphobia with panic attacks: a pilot study.

A battery of vestibular and audiological tests was administered to eight patients with panic disorder and 13 patients with agoraphobia and panic attacks, all of whom experienced dizziness during their panic attacks. Positional or spontaneous nystagmus was present in 67% of the subjects. Abnormal responses were found in caloric testing (56%), rotational testing (35%), and posturography (32%). Pure tone audiograms were abnormal in 26% of the subjects and acoustic reflexes were abnormal in 44% of the subjects. Six of eight patients tested had an abnormal brainstem auditory evoked potential. The possible importance of the findings and their implications for further research are discussed.

Adult↗
PubMed1991

Test for otolith organs with barbecue rotation.

In the sitting position, vertical axis head rotation stimulates only the horizontal canal. In the supine position, horizontal axis rotation, so-called barbecue rotation, is a stimulus to both the horizontal canal and otolith organs. We compared dynamic otolith response to these two types of harmonic rotations in 15 normal subjects. The subjects' heads were rotated, passively with eyes open but covered, at the following frequencies: 0.17, 0.33, 0.50, 0.67 and 1.00 Hz. Head movement and eye movement were recorded by scleral search coil technique. Compensatory eye movements were present on each record. Vestibulo-ocular reflex (VOR) gain was calculated using peak-to-peak velocity of the eye and head. At all frequencies the VOR gain of horizontal axis rotation was larger than that of vertical axis rotation. This difference was maximal at the lowest frequency, 0.17 Hz, suggesting that dynamic otolith stimulus improves VOR at low frequencies.

Adult↗
PubMed1994

Symptomatic and essential palatal tremor. 1. Clinical, physiological and MRI analysis.

Palatal tremor (brief, rhythmic involuntary movements of the soft palate) apparently comprises two different nosological entities: essential palatal tremor (EPT) and symptomatic palatal tremor (SPT). The site of the abnormality in EPT is unknown, whereas SPT is believed to arise from a lesion of the brainstem or cerebellum (within the Guillain-Mollaret triangle). The clinical and physiological properties of these conditions were studied in four patients with EPT and six patients with SPT. Patients with EPT had normal cerebellar function, but those with SPT had clinical signs of cerebellar dysfunction. The palatal movements were consistent with activation of the tensor veli palatini muscle in EPT and of the levator veli palatini muscle in SPT. During sleep, EPT stopped, whereas SPT continued with only slight variations in the tremor rate. The cycle of palatal tremor could not be reset by stimulation of trigeminal afferents in either EPT or SPT patients, and Valsalva's manoeuvre did not consistently affect the rhythm of the tremor in either group. The palatal tremor cycle exerted remote effects on the tonic electromyographic activity of the upper and lower extremities only in patients with SPT. These effects were present only on the side of the cerebellar signs (opposite the side with the enlarged inferior olive) in patients with a unilateral syndrome. Essential palatal tremor patients had only polysynaptic brainstem reflex abnormalities, whereas SPT patients had abnormalities of monosynaptic, oligosynaptic and polysynaptic brainstem reflexes. Magnetic resonance imaging showed no evidence of structural abnormalities in EPT patients, but SPT patients had a hyperdense signal of the ventral upper medulla (the region of the inferior olive) on T2-weighted images. These observations support the hypothesis that EPT and SPT are two different diseases. In SPT, cerebellar dysfunction ipsilateral to the palatal tremor may be due, in part, to abnormal function of the contralateral hypertrophic inferior olive. The proposed basis of SPT is a disturbance of electrotonic coupling between the cells of the inferior olive induced by a lesion of the dentato-olivary pathway. Similar mechanisms could be responsible for postural tremors in general. The pathophysiological basis of EPT remains unknown.

Adult↗
PubMed1978

Semicircular canal stimulation in cerebral palsied children.

Twelve cerebral palsied children were exposed to 16 sessions of horizontal and vertical semicircular canal stimulation over a four-week period in order to determine the effectiveness of this form of stimulation as a therapeutic procedure. A control group of 11 cerebral palsied children was included. A quantitative evaluation of a series of reflexes and of gross motor skills showed a highly significant degree of improvement following the four weeks of treatment. A qualitative evaluation of each subject corroborated these findings and suggested improvements in fine motor control and in social/emotional behavior. A possible central nervous system mechanism underlying the improvement in motor skills is discussed.

Cerebral Palsy↗
PubMed1999

Abolished tilt suppression of the vestibulo-ocular reflex caused by a selective uvulo-nodular lesion.

Within the cerebellum several structures are considered to modulate the function of the vestibulo-ocular reflex (VOR). The nodulus and uvula have been implicated with the low-frequency components of the VOR, which are mediated by the velocity storage system. We report a patient with a selective lesion of the nodulus and ventral uvula. The findings suggest that nodulus and uvula normally exert an inhibitory effect on the velocity storage mechanism.

Cerebellum↗
PubMed1978

Muscle spindle responses in man to changes in load during accurate position maintenance.

1. Single unit and multi-unit recordings of muscle spindle activity were made from the peroneal nerves of human subjects. While the subjects attempted to maintain a constant ankle joint position, an external load on the receptor-bearing muscle was altered unexpectedly. 2. The spindle discharge produced by a sudden increase in load was of similar strength when the receptor-bearing muscle was relaxed as when it was contracting at the moment of the impact. A motor response at a latency consistent with a spinal reflex mechanism occurred only when the muscle was contracting. It is concluded that the potentiation of the reflex mechanism during contraction was not due primarily to a fusimotor action. 3. Sudden decrease in load produced a pause in spindle discharge followed by a pause in on-going e.m.g. activity at a latency consistent with spinal reflex mechanisms. 4. Slow changes in load produced parallel changes in e.m.g. and spindle discharge. It is suggested that the voluntary effort involved in maintaining joint position in the face of gradually changing loads results in corticospinal activity adjusted in strength to the opposing torque and operating on alpha and gamma motoneurones in parallel.

Action Potentials↗
PubMed1995

[A transient sinus arrest after right stellate ganglion block--assessment of autonomic function by heart rate spectral analysis].

We experienced a case of sinus arrest probably induced by right stellate ganglion block (SGB). A healthy medical student volunteered in our study of the cardiac autonomic nervous system and received the SGB. After the Holter ECG had been attached, the SGB was performed with mepivacaine 8 ml. Horner's sign was observed after about 3 minutes. A transient (15 s) sinus arrest occurred suddenly after about 6 minutes of the tilt test probably due to a vasovagal reflex, and the subject lost consciousness. From spectral analysis of the Holter ECG recording, the right SGB may be closely involved in the induction of the sinus arrest. Our present case suggests that sinus arrest may occur if a patient stands up after right SGB.

Adult↗
PubMedDate not supplied

[Study of the vestibulospinal reflex. Clinical applications of posturography].

The vestibulo-spinal reflex is of great importance in maintaining balance--hence the interest in evaluating it objectively in patients suffering from vertigo. A review is made of the objective exploratory methods currently available, i.e., static posturography, stimulation posturography, dynamic posturography and craneocorpography. The clinical applications of posturographyare discussed, fundamentally as applied to the diagnosis of central vestibular pathology, treatment planning and evolutive monitoriacion of the patient with vertigo.

Humans↗
PubMed2005

Increase in group II excitation from ankle muscles to thigh motoneurones during human standing.

In standing subjects, we investigated the excitation of quadriceps (Q) motoneurones by muscle afferents from tibialis anterior (TA) and the excitation of semitendinosus (ST) motoneurones by muscle afferents from gastrocnemius medialis (GM). Standing with a backward lean stretches the anterior muscle pair (TA and Q) and they must be co-contracted to maintain balance. Equally, forward lean stretches the posterior muscle pair (GM and ST) and they must be co-contracted. We used these conditions of enhanced lean to increase the influence of gamma static motoneurones on muscle spindle afferents, which enhances the background input from these afferents to extrafusal motoneurones. The effects of the conditioning volleys on motoneurone excitability was estimated using the modulation of the on-going rectified EMG and of the H reflex. Stimulation of afferents from TA in the deep peroneal nerve at 1.5-2 x MT (motor threshold) evoked early group I and late group II excitation of Q motoneurones. Stimulation of afferents in the GM nerve at 1.3-1.8 MT evoked only late group II excitation of ST motoneurones. The late excitation produced by the group II afferents was significantly greater when subjects were standing and leaning than when they voluntarily co-contracted the same muscle pairs at the same levels of activation. The early effect produced by the group I afferents was unchanged. We propose that this increase in excitation by group II afferents reflects a posture-related withdrawal of a tonic inhibition that is exerted by descending noradrenergic control and is specific to the synaptic actions of group II afferents.

Adaptation, Physiological↗