Guido Maria Filippi

Botulinum A toxin effects on rat jaw muscle spindles

Botulinum A toxin (Botox) is used for the treatment of many muscular dystonias. However, the relief of the sustained and abnormal postures induced by Botox administration is not fully explained. In this work the possibility was considered that Botox can produce a block not only at the alpha motor endings, but also at the gamma motor endings, consequently reducing the spindle inflow to the alpha motoneurons, which have a great role in maintaining the tonic myotatic reflex. Jaw muscle spindle discharge was recorded before and after Botox injection in the deep masseter muscle. The drug consistently reduced the spindle afferent discharge. Such an effect is suggested to be direct on gamma endings as: i) muscle tension was not modified by Botox during the recording time; ii) saline administration never changed the spindle discharge. The Botox effect on muscle spindles suggests that the relief from dystonias could be due not only to a partial motor paralysis, but also to a decrease of the reflex muscular tone.

Long-term effects on cortical excitability and motor recovery induced by repeated muscle vibration in chronic stroke patients.

Background. Muscle vibration modifies corticomotor excitability in healthy subjects and reduces muscle tonus in stroke patients. Objective. This study examined whether repeated muscle vibration (rMV) applied over the flexor carpi radialis (FCR) and biceps brachii (BB) can induce long-lasting changes, using transcranial magnetic stimulation (TMS), in patients with chronic stroke. Methods. Thirty hemiparetic patients who offered at least minimal wrist and elbow isometric voluntary contractions were randomly assigned to either an experimental group, which received rMV in addition to physiotherapy (rMV + PT), or a control group that underwent PT alone. The following parameters of the FCR, BB, and extensor digitorum communis (EDC) were measured through TMS before, and 1 hour, 1 week, and 2 weeks after the end of intervention: resting motor threshold (RMT), map area, map volume, short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF). Muscle tonus and motor function were assessed on the same day as TMS. Results. Pre–post analysis revealed a reduction in RMT and an increase in motor map areas occurred in the vibrated muscles only in the rMV + PT group, with an increase in map volumes of all muscles. Moreover, SICI increased in the flexors and decreased in the extensor. These neurophysiological changes lasted for at least 2 weeks after the end of rMV + PT and paralleled the reduction in spasticity and increase in motor function. A significant correlation was found between the degree of spasticity and the amount of intracortical inhibition. Conclusion. rMV with PT may be used as a nonpharmacological intervention in the neurorehabilitation of mild to moderate hemiparesis.

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.

Sympathetically-induced development of tension in jaw muscles: the possible contraction of intrafusal muscle fibres.

In rabbits, cats and rats anaesthetized, curarized, with the skull fixed in a stereotaxic apparatus, the peripheral stump of the cervical sympathetic nerve (c.s.n.) was electrically stimulated at frequencies within the physiological range and the isometric tension was recorded at the lower jaw. In a group of experiments the afferent discharges from the jaw elevator muscle spindles was also recorded, in the mesencephalic nucleus of the fifth cranial nerve.Unilateral stimulation of the c.s.n. induced in jaw elevator muscles of rabbits an increase of tension of 5.5±0.5 g (latency: 0.5–2 s, time constant: 2.5–5 s) maintained with little or no decrement until the end of stimulation. This response proved not to be secondary to vasomotor changes since: i) approximately half of it was mediated by the fastest conducting component of the c.s.n. fibres, ii) it was not mimicked by a sudden reduction of blood supply to the muscles, iii) it was unaffected by 10 min bilateral occlusion of both the external and the internal carotid arteries. During c.s.n. stimulation the afferent discharge from spindles belonging to jaw elevator muscles exhibited an increase of firing (often preceded by a transient decrease) lasting throughout the stimulation. Also, the position sensitivity of all the spindle afferents tested was modified by the sympathetic stimulation.The results presented are interpreted to suggest that the sympathetic system may induce an intrafusal muscle fibre contraction in jaw elevator muscles. The possible functional implications are also discussed.

Improvement of Stance Control and Muscle Performance Induced by Focal Muscle Vibration in Young-Elderly Women: A Randomized Controlled Trial

UNLABELLED Filippi GM, Brunetti O, Botti FM, Panichi R, Roscini M, Camerota F, Cesari M, Pettorossi VE. Improvement of stance control and muscle performance induced by focal muscle vibration in young-elderly women: a randomized controlled trial. OBJECTIVE To determine the effect of a particular protocol of mechanical vibration, applied focally and repeatedly (repeated muscle vibration [rMV]) on the quadriceps muscles, on stance and lower-extremity muscle power of young-elderly women. DESIGN Double-blind randomized controlled trial; 3-month follow-up after intervention. SETTING Human Physiology Laboratories, University of Perugia, Italy. PARTICIPANTS Sedentary women volunteers (N=60), randomized in 3 groups (mean age +/- SD, 65.3+/-4.2y; range, 60-72). INTERVENTION rMV (100Hz, 300-500microm, in three 10-minute sessions a day for 3 consecutive days) was applied to voluntary contracted quadriceps (vibrated and contracted group) and relaxed quadriceps (vibrated and relaxed group). A third group received placebo stimulation (nonvibrated group). MAIN OUTCOME MEASURES Area of sway of the center of pressure, vertical jump height, and leg power. RESULTS Twenty-four hours after the end of the complete series of applications, the area of sway of the center of pressure decreased significantly by approximately 20%, vertical jump increased by approximately 55%, and leg power increased by approximately 35%. These effects were maintained for at least 90 days after treatment. CONCLUSIONS rMV is a short-lasting and noninvasive protocol that can significantly and persistently improve muscle performance in sedentary young-elderly women.

Area postrema and the mesencephalic trigeminal nucleus

Abstract The ultrastructural morphology of the area postrema (AP) was investigated in the guinea pig: no peculiar features differentiate it from the AP of other vomiting and nonvomiting species. After discrete chronic lesion of the AP, electron micrographs showed clear signs of axonal terminal degeneration on some cells of the ipsilateral mesencephalic trigeminal nucleus (MTN). A direct AP-MTN connection was supported also by electrophysiological investigations. Electrical stimulation of the AP, using liminal or just supraliminal stimuli (4 to 10 μA),—to avoid a simultaneous antidromic activation of Probsts tract—elicited evoked potentials in the ipsilateral MTN with a latency as short as 0.2 to 0.3 ms in both the guinea pig and the rabbit. The same microstimulation of the AP inhibited about the 50% of the ipsilateral MTN units and decreased the excitability of the ipsilateral MTN in the curarized rabbit. In agreement with such findings, AP microstimulation inhibited the jaw movements elicited by MTN stimulation in the noncurarized rabbit. We conclude that the AP exerts an inhibitory influence on the afferent limb of the monosynaptic masseteric reflex.

Quantitative Effects of Repeated Muscle Vibrations on Gait Pattern in a 5-Year-Old Child with Cerebral Palsy

Objective. To investigate quantitatively and objectively the effects of repeated muscle vibration (rMV) of triceps surae on the gait pattern in a 5-year-old patient with Cerebral Palsy with equinus foot deformity due to calf spasticity. Methods. The patient was assessed before and one month after the rMV treatment using Gait Analysis. Results. rMV had positive effects on the patients gait pattern, as for spatio-temporal parameters (the stance duration and the step length increased their values after the treatment) and kinematics. The pelvic tilt reduced its anteversion and the hip reduced the high flexion evidenced at baseline; the knee and the ankle gained a more physiological pattern bilaterally. The Gillette Gait Index showed a significant reduction of its value bilaterally, representing a global improvement of the childs gait pattern. Conclusions. The rMV technique seems to be an effective option for the gait pattern improvement in CP, which can be used also in very young patient. Significant improvements were displayed in terms of kinematics at all lower limb joints, not only at the joint directly involved by the treatment (i.e., ankle and knee joints) but also at proximal joints (i.e., pelvis and hip joint).

Relations among motor unit types, generated forces and muscle length in single motor units of anaesthetized cat peroneus longus muscle

The active length-tension curves of identified single motor units (MUs) belonging to peroneus longus muscle (PL) of anaesthetized adult cats were obtained by eliciting isometric single twitches and tetani. The recorded responses were evaluated by measuring the peak tension amplitude and the tension-time area at muscle lengths extending throughout the physiological length range of the muscle (mean 5.5 mm, standard deviation ±0.8). The muscle lengths at which each tested MU developed its maximal twitch (Ltw) and tetanic (Lte) tensions were determined and compared with the muscle length (Lo) at which the stimulation of all the α-axons, innervating PL and contained in L7 ventral root, developed their maximal twitch tension. The mean of single MU Ltw values was at Lo+1.08±1.1 mm. Slow MUs showed the longest values of Ltw(Lo+1.6±1.0 mm). Single MUs stimulated at tetanic frequencies presented their Lte at values shorter than Lo (Lo−2.8±1.7 mm). Slow MUs had the shortest Lte (Lo−3.4±1.5 mm). For all the units Lte was shorter than Ltw. Ltw and Lte were, respectively, negatively and positively correlated with the developed tension. Optimal length values also appeared to be related to the MU types. The possibility is discussed that the muscle and tendon compliances and the high non-linearities to the applied forces are the main factors which can determine the differences among Lo, Ltw and Lte values. The relationships between MU type and optimal length values are suggested to be, at least partly, an epiphenomenon due to the different contraction strengths of the various MU types. However, the heterogeneous distribution of the MU types is brought into account to explain the dependence of Ltw and Lte values on MU type.

A dual effect of sympathetic nerve stimulation on jaw muscle spindles

In anaesthetized and paralyzed rabbits, electrical stimulation of the cervical sympathetic nerve at physiological frequencies induces in jaw muscle spindle afferents a short-latency decrease or suppression of discharge. This effect is very stereotyped in pattern and is attributed to direct sympathetic innervation of spindles. It is mediated by preganglionic S1-S2 sympathetic fiber groups. A longer-latency facilitatory effect follows, probably vasomotor in origin and mediated by S3-S4 groups. Both responses are eliminated by administration of alpha-adrenergic blocking agents. The latencies, patterns, thresholds, durations and reproducibility of these responses have been studied and the mechanisms possibly involved are discussed.

Cervical sympathetic nerve stimulation can induce an intrafusal muscle fibre contraction in the rabbit

Recent data by Ballard (1978) and by Barker and Saito (1981) about the innervation of muscle spindles by sympathetic nerve fibres (cf. Santini and Ibata, 1971) pose most crucially the problem of the effect and mechanisms of the sympathetic action on muscle spindle behaviour (Hunt et al., 1982; Passatore and Filippi, 1982; further ref. in Staderini and Ambrogi Lorenzini, 1969). In particular, sympathetic terminals were found to be located adjacent to the sensory endings and also in neuroeffective association with both bag and chain intrafusal fibres (Barker and Saito). Consequently the following questions can be posed: 1) is the sympathetic system capable of affecting the activity of the intrafusal muscle fibres? 2) if so, is the effect on spindle output compatible with, and thus presumably secondary to, the action exerted upon intrafusal muscle fibres? 3) what kind of transmitter and receptor are involved? The main results of a series of investigations addressed to answer these questions will be summarized below.