Biomedical subjects

Antonio Nardone

Publications and source records attributed to Antonio Nardone.

9 recordsLinked to original sources

PubMed2007

Balance control in Sensory Neuron Disease.

OBJECTIVE: Balance control under static and dynamic conditions was assessed in patients with Sensory Neuron Disease (SND) in order to shed further light on the pathophysiology of ataxia. METHODS: Fourteen patients with diabetic polyneuropathy and 11 with SND underwent clinical and neurophysiological evaluation, stabilometric recording of body sway during quiet stance with and without vision, stereometric analysis of body segment displacement while riding a platform translating in anterior-posterior direction with and without vision (dynamic condition), and EMG recording of leg muscle responses to abrupt stance perturbation produced by rotation of a supporting platform. The findings were compared to those of age matched normal subjects. RESULTS: Clinical and neurophysiological evaluation revealed a more severe motor impairment in patients with diabetes than SND, while sensory impairment was superimposable. Some patients with SND had vestibular dysfunction of diverse severity. Body sway during stance was larger in patients with SND than diabetes with and without vision. In the stance perturbation condition, the latency of the long-loop EMG response to platform rotation was disproportionately increased with respect to the spinal response in the SND but not in diabetic patients. Under dynamic condition, patients with SND oscillated more than diabetic patients and several of them easily lost balance with eyes closed. CONCLUSIONS: Patients with SND show severe unsteadiness under both static and dynamic conditions, particularly with eyes closed. The patchy sensory loss of SND, disrupting sensation from territories other than the lower limbs and possibly including the vestibular nerve, could be responsible for this instability. Ataxia is correlated to the abnormal latency of the muscle responses to stance perturbation. Since increased response latencies cannot be attributed to a vestibular deficit, the deterioration of equilibrium control would be ascribed mainly to the degeneration of the central branch of the afferent fibres. SIGNIFICANCE: Measures of body balance under quiet stance and dynamic conditions can provide relevant diagnostic information as to the pathophysiology and severity of ataxia and viability of the central branch of the sensory fibres, and help in separating patients with peripheral neuropathy from patients with loss of sensory neurones.

Aged↗

PubMed2006

Balance in Parkinson's disease under static and dynamic conditions.

We tested balance performance in 15 on phase Parkinson's disease (PD) patients (8 nonfallers, PD-NF; 7 fallers, PD-F) during quiet stance (stabilometry) and on a platform continuously moving in the anteroposterior direction (dynamic test). Neither stabilometry (eyes open or closed) nor the dynamic test (eyes open) separated PD-F from PD-NF. With the dynamic test, eyes closed, PD-F with respect to PD-NF showed larger head oscillations, smaller cross-correlation between head and malleolus motion (more so in patients with low Unified Parkinson's Disease Rating Scale, or UPDRS), and larger delays of head with respect to platform motion. Further, across all PD patients, head displacement increased with the equivalent levodopa dose, indicating a trend for medication to worsen balancing capacity while improving UPDRS. The dynamic test is a sensitive tool for detecting instability in PD-F since absence of visual flow selectively impairs both association between body segment movements and anticipatory adjustments.

Accidental Falls↗

PubMed2006

Balance control in peripheral neuropathy: are patients equally unstable under static and dynamic conditions?

The aim of this investigation was to assess the potentially different effects of impaired proprioceptive input in balance control under static and dynamic conditions in neuropathic patients. We recruited 20 normal subjects and 27 patients affected by neuropathies known to affect to a different extent large and medium size afferent fibres. The patients comprised 5 with Charcot-Marie-Tooth disease type 1A (CMT1A), 8 with CMT type 2 (CMT2) and 14 with Diabetes polyneuropathy (Diabetics). Measurement of balance during quiet stance on a stabilometric platform showed that sway area (SA) was larger in the CMT2 and Diabetics than normal subjects or in CMT1A, under both eyes open and closed conditions. The estimated conduction velocity (CV) of the group II afferent fibres was lower in CMT2 and Diabetics than in normal subjects and CMT1A. Across all patients, SA increased as a function of the slowing of group II CV. During a dynamic balance task the head A-P displacement was only slightly increased in the patient groups with respect to normals, despite the increased delay at which the head followed displacement of the feet. The unpredictably good performance of all patient groups under dynamic condition, which was at variance with their imbalance during quiet stance, may indicate that these patients learnt to exploit anticipatory postural strategies.

Adult↗

PubMed2005

Head stabilization on a continuously oscillating platform: the effect of a proprioceptive disturbance on the balancing strategy.

When standing and balancing on a continuously and predictably moving platform, body equilibrium relies on both anticipatory control and proprioceptive feedback. We have vibrated different postural muscles of the body to assess any effect of confounding the proprioceptive input on balance during such unstable conditions. Low and high platform oscillation frequencies were used, because different strategies are used to withstand the two perturbations. Eyes open (EO) and closed (EC) conditions were also tested, to assess whether the stabilizing effect of vision is independent from the proprioceptive disturbance. Subjects (n = 14) performed two series of trials, EO and EC: (1) quiet erect stance, (2) stance on the platform translating at 0.2 or 0.6 Hz sinusoidally in the anteroposterior (A-P) direction (dynamic conditions). Continuous bilateral vibration (90 Hz) was produced by two vibrators fixed to the following homonymous muscles: dorsal neck, quadriceps, biceps femoris, tibialis anterior, and triceps surae. Acquisition of body segments' displacement began 10 s after the start of platform translation. From markers fixed to head, hip, and malleolus, we computed the A-P oscillation of head and hip, body orientation in space, and cross-correlation (CC) and time-delay between malleolus and head trajectories. The results were (a) the head A-P oscillation was smaller with EO than EC, under both quiet stance and dynamic conditions; (b) vibration of tibialis and triceps surae, but not of other muscles, slightly increased head and body A-P oscillation with EC under dynamic conditions; (c) at 0.2 Hz but not at 0.6 Hz, for all visual and vibration conditions, there was a significant association between head and feet; (d) at 0.2 Hz, EC, neck muscle vibration increased this association, whereas vibration of the other muscles induced a major time delay in the oscillation of head compared with feet; (e) vibration of either neck or tibialis induced forward body leaning, while vibration of either triceps surae or biceps femoris induced backward leaning, with both EO and EC, under both static and dynamic conditions; (f) the head A-P oscillation, however, under dynamic conditions was not dependent on body leaning. The relatively scarce effects of proprioceptive disturbance on head stabilization and multijoint coordination (in spite of effects on body orientation similar to those observed during stance) speak for a major role of anticipatory control in the dynamic equilibrium task. However, the significant vibration-induced time delay in segments' coordination at low translation frequency, EC, suggests that the normally patterned Ia input promotes continuous adjustments of the feed-forward control mode.

Adaptation, Physiological↗

PubMed2005

Reflex contribution of spindle group Ia and II afferent input to leg muscle spasticity as revealed by tendon vibration in hemiparesis.

OBJECTIVE: Foot dorsiflexion evokes a short- (SLR) and a medium-latency EMG response (MLR) in the soleus of standing subjects. SLR is mediated by spindle group Ia, while group II fibres contribute to MLR through an oligosynaptic circuit. We studied the effects of Achilles' tendon vibration on both responses in spastic patients to disclose any abnormal excitability of these pathways. METHODS: SLR and MLR were evoked in 11 hemiparetics and 11 normals. The vibration-induced changes in both responses were correlated to the Ashworth score of the affected leg. RESULTS: There were no differences between normals and patients in the size of control SLR or MLR. Vibration decreased SLR to 70% in normal subjects, but increased it to 110% in patients, in both affected and unaffected leg. Vibration did not affect MLR in normals, but increased it to 165% on the affected and 120% on the unaffected side of patients. Ashworth score was solely correlated with the degree of vibration-induced increase of MLR. CONCLUSIONS: While the lack of inhibitory effect of vibration on SLR confirms a reduced inhibitibility of the monosynaptic reflex, the increased MLR indicates a disinhibition of group II pathway in patients, connected to the loss of descending control on group II interneurones. Spastic hypertonia depends on release of group II rather than group Ia reflex pathways. SIGNIFICANCE: These findings give a neurophysiological support for the pharmacological treatment of spastic hypertonia and suggest a method for the assessment of its effects.

Adult↗

PubMed2004

Group II spindle fibres and afferent control of stance. Clues from diabetic neuropathy.

OBJECTIVE: Since patients with large-fibre neuropathy do not show abnormal body sway during stance, the hypothesis was tested that postural control is not impaired until myelinated fibres of medium size are affected. METHODS: In 22 diabetic neuropathic patients and 13 normals, we recorded: (1) body sway area (SA), (2) stretch responses of soleus (Sol) and flexor digitorum brevis (FDB) to toe-up rotation of a platform, (3) Sol and FDB H reflex and FDB F wave, (4) conduction velocity (CV) of tibial, deep peroneal and sural nerve. In patients, detection thresholds for vibration, cooling (CDT), warming and heat-pain (HPDT) were assessed. RESULTS: Body SA was increased in patients with respect to normals. Toe-up rotation elicited short- (SLR) and medium-latency (MLR) responses in Sol and FDB in all normals. In patients, SLR was absent in FDB and reduced in Sol, and MLR was delayed in both muscles; the FDB H reflex was absent. The CV of tibial nerve group II afferent fibres, as estimated from the afferent time of FDB MLR, was reduced in patients. All sensory detection thresholds were increased. Stepwise multiple regression showed that increased SA was explained by increased latency of MLR, decreased CV of group II fibres and augmented CDT and HPDT. CONCLUSIONS: Unsteadiness in diabetic neuropathy is related to alterations in medium-size myelinated afferent fibres, possibly originating from spindle secondary terminations.

Aged↗

PubMed2003

Effects of leg muscle tendon vibration on group Ia and group II reflex responses to stance perturbation in humans.

Stretching the soleus (Sol) muscle during sudden toe-up rotations of the supporting platform in a standing subject evokes a short-latency response (SLR) and a medium-latency response (MLR). The aim of the present investigation was to further explore the afferent and spinal pathways mediating the SLR and MLR in lower limb muscles by means of tendon vibration. In seven subjects, toe-up or toe-down rotations were performed under: (1) control, (2) continuous bilateral vibration at 90 Hz of Achilles' tendon or tibialis anterior (TA) tendon, and (3) post-vibration conditions. Sol and TA background EMG activity and reflex responses were bilaterally recorded and analysed. Toe-up rotations induced SLRs and MLRs in Sol at average latencies of 40 and 66 ms, respectively. During vibration, the latency of both responses increased by about 2 ms. The area of the SLR significantly decreased during vibration, regardless of the underlying background activity, and almost returned to control value post-vibration. The area of Sol MLR was less influenced by vibration than SLR, the reduction being negligible with relatively high background activity. However, contrary to SLR, MLR was even more reduced post-vibration. Toe-down rotations induced no SLR in the TA, while a MLR was evoked at about 81 ms. The area of TA MLR decreased slightly during vibration but much more post-vibration. SLRs and MLRs were differently affected by changing the vibration frequency to 30 Hz: vibration had a negligible effect on the SLR, but still produced a significant effect on the MLR. The independence from the background EMG of the inhibitory effect of vibration upon the SLR suggests that vibration removes a constant amount of the Ia afferent input. This can be accounted for by either presynaptic inhibition of group Ia fibres or a 'busy-line' phenomenon. The differential effect of vibration on SLRs and MLRs is compatible with the notions that spindle primaries have a higher sensitivity to vibration than secondaries, and that group II afferent fibres are responsible for the production of the MLR. The decrease of MLRs but not SLRs after vibration is discussed in terms of an interaction between peripheral and central drive on group II interneurones in order to produce sufficient EMG activity to maintain a given postural set.

Achilles Tendon↗

PubMed2003

Comparison of Cawthorne-Cooksey exercises and sinusoidal support surface translations to improve balance in patients with unilateral vestibular deficit.

OBJECTIVE: To compare the effectiveness of vestibular rehabilitation by using Cawthorne-Cooksey exercises with that of instrumental rehabilitation. DESIGN: The main study (n=32) used a pre-post rehabilitation (A-B) design; the ancillary studies used a subset of 11 patients 1 month before rehabilitation versus pre-post rehabilitation (A-A-B design) and 9 patients pre-post rehabilitation versus 1 month after (A-B-B design). SETTING: Division of physical therapy and rehabilitation at a scientific institute in Italy. PARTICIPANTS: Patients (Cawthorne-Cooksey, n=17; instrumental rehabilitation, n=15) with a complete or incomplete unilateral vestibular lesion due to ischemic, inflammatory, cranial nerve VIII sectioning, or unknown cause. INTERVENTIONS: Cawthorne-Cooksey exercises or instrumental rehabilitation training consisting of standing with eyes open (EO) or closed (EC) on a platform moving, relative to the subjects, in the anteroposterior (AP) or mediolateral direction, at a sinusoidal translation frequency of 0.2 or 0.6Hz; training sessions for both interventions were twice daily, 30 minutes per session, for 5 days. MAIN OUTCOME MEASURES: Body sway and subjective score of sway during quiet stance with EO or EC, with feet 10cm apart (FA) or together (FT); the standard deviation of the AP displacement of the malleolus, hip, and head during AP platform translations; the Dizziness Handicap Inventory (DHI); and performance-oriented evaluation of balance and gait (according to Tinetti). RESULTS: Both interventions improved patients' balance. Under each postural and visual condition, both groups showed reduction in body sway, and the post rehabilitation sway values approached those observed in normal subjects; improvement was significantly better for instrumental rehabilitation under FA EO, FA EC, and FT EC conditions. All patients reported a subjective feeling of increased steadiness. Sway recorded 1 month before treatment did not differ from that at the start of treatment. The follow-up evaluation showed persistence of effect. Parallel to the improved stability, a decrease in the SD of the displacement of hip and head in balancing on the movable platform was present in both groups; improvement was better in the instrumental rehabilitation group than the Cawthorne-Cooksey group under the EC condition. Balance and gait assessment improved to the same extent in both groups. Scores on the physical, functional, and emotional questions of the DHI improved significantly in both groups after treatment, but to a larger extent in the instrumental rehabilitation patients. CONCLUSIONS: Both Cawthorne-Cooksey and instrumental rehabilitation are effective for treating balance disorders of vestibular origin. Improvement affects both control of body balance and performance of activities of daily living. The larger decrease in body sway and greater improvement of DHI after instrumental rehabilitation suggests that it is more effective than Cawthorne-Cooksey exercises in improving balance control.

Activities of Daily Living↗

PubMed2002

Variability in a dynamic postural task attests ample flexibility in balance control mechanisms.

When humans stand upright on a platform that sinusoidally translates in the anterior-posterior direction, the movements of upper and lower body segments are appropriately coordinated, in order to keep the body within its limits of stability. A significant fluctuation in this behaviour is evident across subjects and perturbation conditions. The inter- and intrasubject variability in the body segment kinematics, as occurs during repeated trials across different conditions, is quantitatively described here. Twenty normal subjects stood upright with eyes open (EO) or eyes closed (EC) on a platform moving to-and-fro in the horizontal plane for 30 s, at a frequency of 0.2 and 0.6 Hz, with a peak-to-peak amplitude of 6 cm. Each subject made two trial repetitions for each visual and frequency condition. The last 20 s of each trial was acquired. The displacement of markers fixed on the lateral malleolus, hip and head was sampled at a frequency of 50 Hz. An index of the 'average' displacement of each marker during the trial was the standard deviation (SD) of its anterior-posterior displacements, calculated across the acquired trial cycles. The cross-correlation (CC) between pairs of marker displacement traces gave an indication of the degree of coupling of the body segments. All subjects showed two basic modes of coping with the perturbation, depending on the availability of the visual input: with EO, they tended to stabilize the head in space; with EC, the head oscillated in the anterior-posterior direction more than hip and platform. Within this general behaviour, the values of the SD of horizontal displacement of head and hip marker traces varied within an ample range during different trials of the same perturbation condition. Even within a single trial there was an ample variability of the body segments' position. In spite of this, neither head nor hip ever bypassed the anterior or posterior limits of stability. Remarkably, the range of variability of the whole population of normal subjects, both across and within trials, was analogous to the range of variability of single subjects across numerous trials. This large variability notwithstanding, it appeared that the relationship of head to hip SD across trials was almost constant, independent of visual and perturbation frequency condition. The results show that there exist a large variety of dynamic postures, rather than one particular configuration, which assure stability. The findings also suggest a neural or biomechanical constraint underlying the operations of the equilibrium control strategy.

Adolescent↗