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At least 649 records · Page 36Linked to original sources
PubMed1991

Tremor in reflex sympathetic dystrophy.

Postural hand tremor was quantitatively investigated on both sides in 21 patients suffering from unilateral reflex sympathetic dystrophy of the upper extremity. On the affected side, enhanced tremor amplitude, with a mean tremor frequency of 7.2 Hz, was found in 57% of the patients. The appearance of tremor did not correlate to the occurrence of a single clinical symptom of reflex sympathetic dystrophy. On loading with increasing weight, the frequency of this pathological tremor shifted toward lower values, as it is found in physiological tremor. However, the peak frequencies of the electromyogram remained more or less stable. On recovery from this condition, the reflex sympathetic dystrophy tremor disappeared. Acute sympatholytic intervention could normalize reflex sympathetic dystrophy tremor. This would suggest that the sympathetic supply of the affected extremity contributes to the tremor in reflex sympathetic dystrophy. In conclusion, it is suggested that reflex sympathetic dystrophy should be included among the causes of tremor. According to our findings, tremor in reflex sympathetic dystrophy should be regarded as an enhanced physiological tremor.

Electromyography↗
PubMed1985

Determination of excitability in human proprioceptive reflexes: analysis and characteristics of EMG thresholds of postural muscle.

In order to derive indirect indices of reflex excitability, human soleus (Sol) H reflex and direct M response threshold intensities (HT, MT) were determined by probit analysis of quantal responses elicited in the surface electromyogram (EMG). Within sessions, HT and MT co-varied with respect to time along a logarithmic time-course, both attaining effectively stable levels after 40-60 min of recording. The pattern of this co-variation was imposed by non-reflex factors, primarily the electrode system employed. Sampling distributions of stable thresholds were positively skewed (median values: HT, 5.20 mA, MT, 6.83 mA), and concurrently determined values were strongly correlated (r = 0.965). The Sol threshold ratio (HT/MT) was largely unaffected by non-reflex factors and was therefore stable within subjects, both within sessions (with respect to time) and between sessions. This ratio was normally distributed (mean = 0.753 +/- 0.079 S.D.). Criteria of indirect indices of reflex excitability are proposed: HT satisfies the criteria applicable to a relative index. However, the characteristics of the threshold ratio permit its use as a powerful absolute index of proprioceptive reflex excitability.

Adolescent↗
PubMed1977

Excitability of lower limb myotatic reflex arcs under the influence of caloric labyrinthine stimulation. Analysis of the postural effects in man.

The excitability changes of myotatic reflex arcs have been investigated in 36 volunteers by two methods (tendon reflex and tonic vibration reflex) in a bilateral invertigation of soleus, quadriceps, biceps femoris, and tibialis anterior after caloric stimulation of the labyrinth. The extensor myotatic reflexes are facilated during the irrigation and the nystagmus phases. Contrary to the soleus, quadriceps facilitation is not symmetrical during the phase of nystagmus but predominates on the side opposite to the expected axial deviation. The short biceps femoris reflexes are slightly facilitated. The postural modifications arise from differences in the degree of bilateral facilitation of the extensors.

Adolescent↗
PubMed1989

[The vestibulospinal reflex and its tests].

Examination of vestibulospinal reflexes is an integral part of investigation of the balance apparatus activity. Four tests were selected to verify its utility and reliability, i.e. Romberg (stand II) and Hautant's tests for examining tonic reflexes, Fukuda's stepping test and writing test to monitor how the vestibular apparatus affects coordinated movement. The latter was, however, eliminated from clinical usage due to its unreliability. The final assessment of vestibulospinal reflexes is made more precise by simultaneous evaluation of the three remaining tests.

Humans↗
PubMed2004

Postural effects on pharyngeal protective reflex mechanisms.

STUDY OBJECTIVES: Pharyngeal muscle dilators are important in obstructive sleep apnea pathogenesis because the failure of protective reflexes involving these muscles yields pharyngeal collapse. Conflicting results exist in the literature regarding the responsiveness of these muscles during stable non-rapid eye movement sleep. However, variations in posture in previous studies may have influenced these findings. We hypothesized that tongue protruder muscles are maximally responsive to negative pressure pulses during supine sleep, when posterior tongue displacement yields pharyngeal occlusion. DESIGN: We studied all subjects in the supine and lateral postures during wakefulness and stable non-rapid eye movement sleep by measuring genioglossus and tensor palatini electromyograms during basal breathing and following negative pressure pulses. SETTING: Upper-airway physiology laboratory of Sleep Medicine Division, Brigham and Women's Hospital. SUBJECTS/PARTICIPANTS: 17 normal subjects. MEASUREMENTS AND RESULTS: We observed an increase in genioglossal responsiveness to negative pressure pulses in sleep as compared to wakefulness in supine subjects (3.9 percentage of maximum [%max] +/- 1.1 vs 4.4 %max +/- 1.0) but a decrease in the lateral decubitus position (4.1 %max +/- 1.0 vs 1.5 %max +/- 0.4), the interaction effect being significant. Despite this augmented reflex, collapsibility, as measured during negative pressure pulses, increased more while subjects were in the supine position as compared with the lateral decubitus position. While the interaction between wake-sleep state and position was also significant for the tensor palatini, the effect was weaker than for genioglossus, although, for tensor palatini, baseline activity was markedly reduced during non-rapid eye movement sleep as compared with wakefulness. CONCLUSION: We conclude that body posture does have an important impact on genioglossal responsiveness to negative pressure pulses during non-rapid eye movement sleep. We speculate that this mechanism works to prevent pharyngeal occlusion when the upper airway is most vulnerable to collapse eg, during supine sleep.

Adult↗