Romildo Don

Gait pattern in inherited cerebellar ataxias

Our aim was to perform a comprehensive analysis of the global and segmental features of gait in patients with genetically confirmed inherited ataxias. Sixteen patients with autosomal dominant (spinocerebellar ataxia, SCA1 or 2) or recessive (Friedreich’s ataxia, FRDA) ataxia were studied. We used a motion analysis system to record gait kinematic and kinetic data. We measured the mean values of global (time–distance parameters, COM displacement, support moment) and segmental gait parameters (joint displacement and inter-joint coordination), as both discrete and continuous variables, and their variability and correlations with International Cooperative Ataxia Rating Scale (ICARS) scores. We found a marked difference in all global gait parameters between the ataxic patients and the controls and close correlations between longer stride and stance duration and lower gait, posture and total ICARS scores. The only difference between the two patient groups was a shorter step length in the FRDA patients. As regards the segmental features, we found a significantly different waveform shape for all continuous kinematic and kinetic measures between the ataxic patients and the healthy controls, but only minor differences for the discrete measures. Intersegmental coordination evaluated using the continuous relative phase method revealed an irregular alternating joint behaviour without clear evidence of the synchronous pattern of alternating proximal/distal joint seen in healthy subjects. For almost all gait parameters we observed a markedly higher intra-subject variability in the ataxic patients versus the controls, which was strongly related to the clinical ICARS scores. Patients with chronic, progressive inherited ataxias lose the ability to “stabilize” a walking pattern that can be repeated over time. The most peculiar aspect of the gait of inherited ataxia patients, regardless the different genetic forms, seems to be the presence of increased variability of all global and segmental parameters rather than an invariant abnormal gait pattern.

Long-term effects on motor cortical excitability induced by repeated muscle vibration during contraction in healthy subjects

OBJECTIVE The effects of a novel repeated muscle vibration intervention (rMV; 100 Hz, 90 min over 3 consecutive days) on corticomotor excitability were studied in healthy subjects. METHODS rMV was applied over the flexor carpi radialis (FCR) during voluntary contraction (experiment 1), during relaxation and during contraction without vibration (experiment 2). Focal transcranial magnetic stimulation (TMS) was applied before rMV and one hour, and one, two and three weeks after the last muscle vibration intervention. At each of these time points, we assessed the motor map area and volume in the FCR, extensor digitorum communis (EDC) and abductor digiti minimi (ADM). Short-interval intracortical inhibition (SICI) and facilitation (ICF) were tested for the flexor/extensor muscles alone. RESULTS Following rMV under voluntary contraction, we observed a significant reduction in the FCR map volumes and an enhancement in the EDC. SICI was increased in the FCR and reduced in the EDC. These changes persisted for up to two weeks and occurred at the cortical level in the hemisphere contralateral to the side of the intervention. CONCLUSION We conclude that rMV, applied during a voluntary contraction, may induce prolonged changes in the excitatory/inhibitory state of the primary motor cortex. These findings may represent an important advance in motor disorder rehabilitation.

Four‐week trunk‐specific rehabilitation treatment improves lateral trunk flexion in Parkinson's disease

People with Parkinsons disease (PD) often have a posture characterized by lateral trunk flexion poorly responsive to antiparkinsonian drugs. To examine the effects of a rehabilitation programme (daily individual 90‐minute‐sessions, 5‐days‐a‐week for 4‐consecutive weeks) on lateral trunk flexion and mobility, 22 PD patients with mild to severe lateral trunk flexion, and 22 PD patients without trunk flexion were studied. Patients were evaluated using the Unified Parkinsons Disease Rating Scale motor subscale (UPDRS‐III) score, and the kinematic behavior of the trunk was recorded by means of an optoelectronic system to determine: a) trunk flexion, inclination and rotation values in the erect standing posture; b) ranges of trunk flexion and inclination during trunk movements. After the treatment, significant decreases in trunk flexion [24°(4) vs. 14°(3), P < 0.001] and inclination in the static condition [23°(5) vs. 12°(4), P < 0.001)] were observed, both of which were maintained at the 6‐month follow up. During the trunk flexion task, a significantly increased range of trunk flexion [64°(15) vs. 83°(15), P < 0.001] was observed; similarly, during the lateral bending task, the range of trunk inclination was found to be significantly increased, both toward the side of the trunk deviation [29°(8) vs. 42°(13), P < 0.01] and toward the contralateral side [14°(6) vs 29°(11), P < 0.01]. No further significant changes were observed at the 6‐month follow‐up. Trunk flexion and inclination values in the upright standing posture correlated slightly with the UPDRS‐III score. Our findings show that significant improvements in axial posture and trunk mobility can be obtained through the 4‐week rehabilitation programme described, with a parallel improvement in clinical status.

Kinematic and Electromyographic Study of the Nociceptive Withdrawal Reflex in the Upper Limbs during Rest and Movement

This study set out to evaluate nociceptive withdrawal reflex (NWR) excitability and the corresponding mechanical response in the upper limbs during rest and movement. We used a three-dimensional motion analysis system and a surface EMG system to record, in 10 healthy subjects, the NWR in eight upper limb muscles and the corresponding mechanical response in two experimental conditions: rest and movement (reaching for, picking up, and moving a cylinder). The NWR was elicited through stimulation of the index finger with trains of pulses delivered at multiples of the pain threshold (PT). We correlated movement types (reach-to-grasp, grasp-and-lift), movement phases (acceleration, deceleration), and muscle activity types (shortening, lengthening, isometric) with the presence/absence of the NWR (reflex-muscle pattern), with NWR size values, and with the mechanical responses. At rest, when the stimulus was delivered at 4× PT, the NWR was present, in all muscles, in >90% of trials, and the mechanical response consisted of wrist adduction, elbow flexion, and shoulder anteflexion. At this stimulus intensity, during movement, the reflex-muscle pattern, reflex size, and mechanical responses were closely modulated by movement type and phase and by muscle activity type. We did not find, during movement, significant correlations with the level of EMG background activity. Our findings suggest that a complex functional adaptation of the spinal cord plays a role in modulating the NWR in the transition from rest to movement and during voluntary arm movement freely performed in three-dimensional space. Study of the upper limb NWR may provide a window onto the spinal neural control mechanisms operating during movement.

Modulation of spinal inhibitory reflex responses to cutaneous nociceptive stimuli during upper limb movement

In the present study we investigated the probability, latency and duration of the inhibitory component of the withdrawal reflex elicited by painful electrical stimulation of the index finger in humans. The stimulus consisted of a train of high‐intensity pulses. The investigation was carried out in several upper limb muscles during isometric contractions of different strengths and during a motor sequence consisting of reaching, picking up and transporting an object. We used a new algorithm to detect and characterize the inhibitory reflex. The reflex was found in all muscles except the brachioradialis at all the isometric contraction strengths, and showed a distal‐to‐proximal gradient of latency and duration. Conversely, during movement the reflex probability was high (> 80%) in the anterior deltoid and triceps muscles during reaching, in the extensor carpi radialis muscle during transporting of the object, and in the first interosseous muscle during both picking up and transporting of the object. This modulation of inhibitory reflex transmission in the upper limb muscles suggests that the motor response is organized in such a way as to inhibit the overall ongoing motor task by interrupting motion during reaching and by releasing the object during transporting. This pattern of modulation appears to differ markedly from that previously reported for the excitatory component of the withdrawal reflex. Study of the nociceptive inhibitory reflexes during movement offers new and more profound insights into the functional anatomical organization of the spinal interneuronal network mediating sensory–motor integration.

Modelling the spine as a deformable body: Feasibility of reconstruction using an optoelectronic system

The aims of this study were to develop a kinematic model of the spine, seen as a continuous deformable body and to identify the smallest set of surface markers allowing adequate measurements of spine motion. The spine is widely considered as a rigid body or as a kinematic chain made up of a smaller number of segments, thereby introducing an approximation. It would be useful to have at our disposal a technique ensuring accurate and repeatable measurement of the shape of the whole spine. Ten healthy subjects underwent a whole-spine radiographic assessment and, simultaneously, an optoelectronic recording. Polynomial interpolations of the vertebral centroids, of the whole set of markers were performed. The similarity of the resulting curves was assessed. Our findings indicate that spine shape can be reproduced by 5th order polynomial interpolation. The best approximating curves are obtained from either 10- or 9-marker sets. Sagittal angles are systematically underestimated.

Adaptive behaviour of the spinal cord in the transition from quiet stance to walking

BackgroundModulation of nociceptive withdrawal reflex (NWR) excitability was evaluated during gait initiation in 10 healthy subjects to investigate how load- and movement-related joint inputs activate lower spinal centres in the transition from quiet stance to walking. A motion analysis system integrated with a surface EMG device was used to acquire kinematic, kinetic and EMG variables. Starting from a quiet stance, subjects were asked to walk forward, at their natural speed. The sural nerve was stimulated and EMG responses were recorded from major hip, knee and ankle muscles. Gait initiation was divided into four subphases based on centre of pressure and centre of mass behaviours, while joint displacements were used to categorise joint motion as flexion or extension. The reflex parameters were measured and compared between subphases and in relation to the joint kinematics.ResultsThe NWR was found to be subphase-dependent. NWR excitability was increased in the hip and knee flexor muscles of the starting leg, just prior to the occurrence of any movement, and in the knee flexor muscles of the same leg as soon as it was unloaded. The NWR was hip joint kinematics-dependent in a crossed manner. The excitability of the reflex was enhanced in the extensor muscles of the standing leg during the hip flexion of the starting leg, and in the hip flexors of the standing leg during the hip extension of the starting leg. No notable reflex modulation was observed in the ankle muscles.ConclusionsOur findings show that the NWR is modulated during the gait initiation phase. Leg unloading and hip joint motion are the main sources of the observed modulation and work in concert to prepare and assist the starting leg in the first step while supporting the contralateral leg, thereby possibly predisposing the lower limbs to the cyclical pattern of walking.

Reorganization of multi-muscle and joint withdrawal reflex during arm movements in post-stroke hemiparetic patients

OBJECTIVES To investigate the behavior of the nociceptive withdrawal reflex (NWR) in the upper limb during reaching and grasping movements in post-stroke hemiparetic patients. METHODS Eight patients with chronic stroke and moderate motor deficits were included. An optoelectronic motion analysis system integrated with a surface EMG machine was used to record the kinematic and EMG data. The NWR was evoked through a painful electrical stimulation of the index finger during a movement which consisted of reaching out, picking up a cylinder, and returning it to the starting position. RESULTS We found that: (i) the NWR is extensively rearranged in hemiparetic patients, who were found to present different kinematic and EMG reflex patterns with respect to controls; (ii) patients partially lose the ability to modulate the reflex in the different movement phases; (iii) the impairment of the reflex modulation occurs at single-muscle, single-joint and multi-joint level. CONCLUSIONS Patients with chronic and mild-moderate post-stroke motor deficits lose the ability to modulate the NWR dynamically according to the movement variables at individual as well as at multi-muscle and joint levels. SIGNIFICANCE The central nervous system is unable to use the NWR substrate dynamically and flexibly in order to select the muscle synergies needed to govern the spatio-temporal interaction among joints.

KINEMATIC AND NEUROPHYSIOLOGICAL MODELS: FUTURE APPLICATIONS IN NEUROREHABILITATION

This paper emphasizes the importance of developing kinematic and neurophysiological methods for evaluating motor and functional recovery in the field of neurorehabilitation. From a review of the literature, it is concluded that optoelectronic motion analysis and neurophysiological techniques, such as the study of nociceptive withdrawal reflex, might constitute useful applications for future research.