Proprioception more impaired distally than proximally in subjects with hemispheric dysfunction

The relations between cognitive and motivational components of anosognosia for left-sided hemiplegia and the right hemisphere dominance for emotions: A historical survey

Since the description of anosognosia for hemiplegia by Babinski (who also stressed the links between anosognosia and right hemisphere damage) both motivational and cognitive mechanisms have been advanced to explain this awareness disorder. In this review I will discuss first the neurophysiological mechanisms that can impede the discovery of the motor deficits contralateral to the brain lesion and then suggest that some instances of anosognosia for left-sided hemiplegia may also be due to motivational mechanisms of denial. Among the cognitive mechanisms, sensory feedback and intentional feed-forward disorders can lead to a poor awareness of the motor defects, whereas denial mechanisms could result from an interaction between the right hemisphere dominance for emotions and the anxiety raised by the catastrophic consequences of the brain damage. In particular, a maladaptive reaction to the personal implications of the brain lesion could be revealed by the presence of an implicit acknowledgement of the motor defect.

Multiple Concussions Increase Odds and Rate of Lower Extremity Injury in National Collegiate Athletic Association Athletes After Return to Play

BACKGROUND

Concussion in collegiate athletics is one of the most prevalent sport-related injuries in the United States, with recent studies suggesting persistent deficits in neuromuscular control after a concussion and an associated increase in risk of lower extremity injury.

PURPOSE

To expand on the relationship between concussion and lower extremity injury by examining the effect of multiple concussions (MC) on rate and odds of future lower extremity injury in collegiate athletes after return to play (RTP) compared with matched controls.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

From 2001 to 2016, 48 National Collegiate Athletic Association Division I athletes sustaining multiple concussions at a single institution were identified. Athletes with multiple concussions (MC) were matched directly to athletes with a single concussion (SC) and to athletes with no concussion history (NC) by sex, sport, position, and games played. Incidence of, time to, and location of lower extremity injury were recorded for each group after RTP from their first reported concussion until completion of their collegiate career. Logistic regression was used to analyze odds ratios (ORs) for sustaining lower extremity injury, whereas time to injury was summarized by use of Kaplan-Meier curves and log rank test analysis.

RESULTS

The incidence of lower extremity injury after RTP was significantly greater (P = .049) in the MC cohort (36/48, 75%) than in SC athletes (25/48 = 52%) and NC athletes (27/48 = 56%). Similarly, odds of lower extremity injury were significantly greater in the MC cohort than in SC athletes (OR, 3.00; 95% CI, 1.26-7.12; P = .01) and NC athletes (OR, 1.66; 95% CI, 1.07-2.56; P = .02). Time to lower extremity injury was significantly shorter in the MC group compared with matched controls (P = .01). No difference was found in odds of lower extremity injury or time to lower extremity injury between SC and NC athletes.

CONCLUSION

Collegiate athletes with MC were more likely to sustain a lower extremity injury after RTP in a shorter time frame than were the matched SC and NC athletes. This may suggest the presence of a cohort more susceptible to neuromuscular deficits after concussion or more injury prone due to player behavior, and it may imply the need for more stringent RTP protocols for athletes experiencing MC.

Neglect and extinction in kinesthesia and thesesthesia: understanding proprioceptive inattention

This paper describes a new observation of neglect and extinction of kinesthesia and thesesthesia (movement and position imperception), jointly reflecting proprioceptive inattention, in a series of patients with parietal lesions. A prototypical case is discussed in detail and unaddressed aspects of proprioceptive inattention are discussed through findings from four additional cases. Thesesthetic and kinesthetic extinction were tested through simultaneous antidromic vertical displacement of index fingers, while having patients report on finger proprioceptive perception with eyes closed. Patients had variable degrees of proprioceptive inattention affecting a specific limb, but without pallesthetic inattention or somatoagnosia, whereas symptoms often resolved with visual feedback or active limb movements. Findings support that kinesthesia and thesesthesia (a) are subserved by near-identical brain networks, (b) relate more to tactile perception than pallesthesia in higher order cortical areas, and (c) have a somatotopic cortical organization even in association brain areas. Furthermore, proprioceptive extinction and neglect involve (i) "attention network" structures, (ii) either hemisphere, (iii) gray or subcortical white matter damage, (iv) defective vigilance mechanisms possibly through premature habituation of spatiotemporally saturated neural capacitor circuits, and (v) are not the result of somatoagnosia, while (vi) their resolution is observed through reafferent motor-sensory or visual feedback.

Proximodistal gradient in the perception of delayed stiffness

Proximal and distal muscles are different in size, maximum force, mechanical action, and neuromuscular control. In the current study we explore the perception of delayed stiffness when probing is executed using movement of different joints. We found a proximodistal gradient in the amount of underestimation of delayed stiffness in the transition between probing with shoulder, elbow, and wrist joints. Moreover, there was a similar gradient in the optimal weighting between estimation of stiffness and the inverse of estimation of compliance that predicted the perception of the subjects. These gradients could not be ascribed to differences in movement amplitude, duration, velocity, and force amplitude because these variables were not significantly modulated by the joint used for probing. Mean force did not follow a similar gradient either. Therefore we suggest that the observed gradient in perception reveals a proximodistal gradient in control, such that proximal joints are dominated by force control, whereas distal joints are dominated by position control.

Ipsilesional and contralesional sensorimotor function after hemispherectomy: differences between distal and proximal function

Previous studies have reported mainly on contralesional somatosensory and motor function after hemispherectomy. So far, ipsilesional impairments have received little attention even though these have been reported in patients with less extensive lesions. In the current study we assessed ipsilesional and contralesional sensorimotor function in a group of 12 patients with hemispherectomy. In addition, we focused on differences between distal and proximal function and investigated several factors that may have contributed to individual differences between patients. The tests included tapping, force production, tactile double simultaneous stimulation, pressure sensitivity, passive joint movement sense and sensitivity to hot and cold. Ipsilesional impairments were found on all tests, except passive joint movement sense. Unexpectedly, no significant ipsilateral distal-proximal gradient was found for any of the measures. Both the removal of the diseased cerebral hemisphere and possible changes to the remaining brain structures may have affected ipsilesional sensorimotor function. Contralesional performance was impaired on all tests except for passive joint movement in the shoulder. The contralesional impairments were characterized by a distal-proximal gradient measured on all tests, except that of sensitivity to hot and cold. Distal function was always most impaired. The difference between distal and proximal motor function is in agreement with the established concepts of the motor pathways, with the motoneurons innervating proximal muscles receiving bilateral cortical and subcortical input. Age at onset of original brain damage correlated significantly with passive joint movement sense. Patients with known abnormalities to the remaining brain structures performed inferior on the tapping test only. No effect was found of the hemispheric side of removal.