Three-dimensional motion analysis of the effects of auditory cueing on gait pattern in patients with Parkinson's disease: a preliminary investigation.

Auditory cueing enhances gait in parkinsonian patients. Our aim was to evaluate its effects on spatiotemporal (stride length, stride time, cadence, gait speed, single and double support duration) kinematic (range of amplitude of the hip, knee and ankle joint angles registered in the sagittal plane) and kinetic (maximal values of the hip and ankle joint power) gait parameters using three-dimensional motion analysis. Eight parkinsonian patients performed 12 walking tests: 3 repetitions of 4 conditions (normal walking, 90, 100, and 110% of the mean cadence at preferred pace cued walking). Subjects were asked to uniform their cadence to the cueing rhythm. In the presence of auditory cues stride length, cadence, gait speed and ratio single/double support duration increased. Range of motion of the ankle joint decreased and the maximal values within the pull-off phase of the hip joint power increased. Thus, auditory cues could improve gait modifying motor strategy in parkinsonian patients.

Learning potentiates neurophysiological and behavioral placebo analgesic responses.

Expectation and conditioning are supposed to be the two main psychological mechanisms for inducing a placebo response. Here, we further investigate the effects of both expectation, which was induced by verbal suggestion alone, and conditioning at the level of N1 and N2-P2 components of CO2 laser-evoked potentials (LEPs) and subjective pain reports. Forty-four healthy volunteers were pseudorandomly assigned to one of three experimental groups: Group 1 was tested with verbal suggestion alone, Group 2 was tested with a conditioning procedure, whereby the intensity of painful stimulation was reduced surreptitiously, so as to make the volunteers believe that the treatment was effective, Group 3 was a control group that allowed us to rule out phenomena of sensitization and/or habituation. Pain perception was assessed according to a Numerical Rating Scale (NRS) ranging from 0=no pain sensation to 10=maximum imaginable pain. Both verbal suggestions (Group 1) and conditioning (Group 2) modified the N2-P2 complex, but not the N1 component of LEPs. However, the suggestion-induced LEP changes occurred without subjective perception of pain decrease. Conversely, the N2-P2 amplitude changes that were induced by the conditioning procedure were associated with the subjective perception of pain reduction. Compared to natural history, conditioning produced more robust reductions of LEP amplitudes than verbal suggestions alone. Overall, these findings indicate that prior positive experience plays a key role in maximizing both behavioral and neurophysiological placebo responses, emphasizing that the placebo effect is a learning phenomenon which affects the early central nociceptive processing.

Effects of transcutaneous electrical nerve stimulation on motor cortex excitability in writer's cramp: neurophysiological and clinical correlations.

We recently reported that transcutaneous electrical nerve stimulation (TENS) applied over forearm flexor muscles, a paradigm producing in physiological conditions transient changes in corticomotoneuronal excitability of forearm muscles, may improve motor symptoms in writer's cramp (WC). In the present study, we explored the possibility that one or repeated sessions of TENS might have beneficial effects on handwriting in WC by remodulating cortical excitability of forearm agonist and antagonist muscles. Motor evoked potentials (MEPs) after transcranial magnetic stimulation of the left motor cortex were recorded from the right flexor carpi radialis (FCR) and extensor carpi radialis (ECR) muscles, before and after 1 and 15 sessions of TENS applied over flexor muscles in patients and in a control group. One session of TENS induced a significant smaller reduction of MEPs from the FCR and a smaller increase of the MEPs from the ECR in patients than in normal subjects. In WC, repeated sessions of TENS had the effect to decrease MEP amplitude in the FCR and to increase it in the ECR. This modulation was paralleled by a handwriting improvement. In conclusion, repeated TENS sessions may have the effect to re-modulate excitability of the motor cortex in WC and this modulation might partially play a role in temporarily improving the handwriting.

Long-lasting modulation of human motor cortex following prolonged transcutaneous electrical nerve stimulation (TENS) of forearm muscles: evidence of reciprocal inhibition and facilitation.

Several lines of evidence indicate that motor cortex excitability can be modulated by manipulation of afferent inputs, like peripheral electrical stimulation. Most studies in humans mainly dealt with the effects of prolonged low-frequency peripheral nerve stimulation on motor cortical excitability, despite its being known from animal studies that high-frequency stimulation can also result in changes of the cortical excitability. To investigate the possible effects of high-frequency peripheral stimulation on motor cortical excitability we recorded motor-evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) of the left motor cortex from the right flexor carpi radialis (FCR), extensor carpi radialis (ECR), and first dorsal interosseous (FDI) in normal subjects, before and after transcutaneous electrical nerve stimulation (TENS) of 30 min duration applied over the FCR. The amplitude of MEPs from the FRC was significantly reduced from 10 to 35 min after TENS while the amplitude of MEPs from ECR was increased. No effects were observed in the FDI muscle. Indices of peripheral nerve (M-wave) and spinal cord excitability (H waves) did not change throughout the experiment. Electrical stimulation of the lateral antebrachial cutaneous nerve has no significant effect on motor cortex excitability. These findings suggest that TENS of forearm muscles can induce transient reciprocal inhibitory and facilitatory changes in corticomotoneuronal excitability of forearm flexor and extensor muscles lasting several minutes. These changes probably may occur at cortical site and seem to be mainly dependent on stimulation of muscle afferents. These findings might eventually lead to practical applications in rehabilitation, especially in those syndromes in which the excitatory and inhibitory balance between agonist and antagonist is severely impaired, such as spasticity and dystonia.

Enhanced intracortical inhibition in cerebellar patients.

OBJECTIVE: The aim of the study was to examine intracortical excitability in cerebellar patients. METHODS: Short-latency intracortical inhibition (SICI), long-latency intracortical inhibition (LICI) and intracortical facilitation (ICF) to paired transcranial magnetic stimulation (TMS) were investigated in 8 patients with 'pure' cerebellar syndromes and in 14 age-matched normal controls. The conditioning stimulus for short-latency intracortical inhibition and intracortical facilitation was set at 70% of the resting motor threshold (RMT) and preceded the test stimulus (110-120% of the resting motor threshold) by interstimulus intervals (ISIs) of 1-30 ms. For the long-latency intracortical inhibition determinations, the conditioning stimulus was set at 120% of the resting motor threshold and preceded the test stimulus (also 120% of the resting motor threshold) by interstimulus intervals of 30-500 ms. RESULTS: No statistically significant differences were found between patients and controls as regards either short-latency intracortical inhibition or intracortical facilitation. A significant prevalence of long-latency intracortical inhibition was present in cerebellar patients at interstimulus intervals of 200-500 ms (conditioned MEP amplitude=29-41% of test MEP) as compared to controls (71-96% of test MEP). The amplitude of conditioned MEPs was persistently less than 45% of the test MEP in six patients, who were studied at interstimulus intervals up to 1000 ms. CONCLUSIONS: Long-latency intracortical inhibition was prevalent and abnormally longer-lasting in patients. Tonic hyperactivation of a subpopulation of GABAergic interneurons in the motor cortex of patients may be the mechanism responsible for this abnormality. Our findings seem to be specific to cerebellar diseases and are the opposite of those found in movement disorders such as dystonia and Parkinson's disease. These data suggest that the cerebellum and the basal ganglia may have opposite influences in tuning the excitability of the motor cortex.

Short-term plastic changes of the human nociceptive system following acute pain induced by capsaicin.

OBJECTIVE: To investigate possible neuroplastic changes induced by pain in cerebral areas devoted to nociceptive input processing. METHODS: CO(2) laser-evoked potentials (LEPs) were recorded from 10 healthy subjects after stimulation of the right and left hand dorsum. Acute pain was obtained by topical application of capsaicin on the skin of right hand dorsum. LEPs were recorded after right and left hand stimulation before capsaicin, at the peak pain and 10-20 min after capsaicin removal. Right hand LEPs were evoked by laser stimuli delivered over the zone of secondary hyperalgesia during capsaicin and on both the zones of primary and secondary hyperalgesia after capsaicin removal. RESULTS: After right hand stimulation, the vertex LEPs, which are generated in the cingulate cortex, were significantly decreased in amplitude during capsaicin application and after capsaicin removal. Moreover, the topography of these potentials was modified after capsaicin removal, shifting from the central toward the parietal region. Dipolar modelling showed that the dipolar source in the anterior cingulate cortex moved backward after capsaicin removal. All these changes were not observed after stimulation of the left hand, contralateral to the application of capsaicin, thus suggesting that functional changes are selective for the painful skin and the adjacent territories. CONCLUSIONS: Our results suggest that acute cutaneous pain may inhibit the neural activity in regions of central nervous system processing nociceptive inputs and cortical representation of these inputs can be rapidly modified in presence of acute pain.

Therapeutic effects of peripheral repetitive magnetic stimulation on myofascial pain syndrome.

OBJECTIVE: To evaluate short- and medium-term effects of peripheral repetitive magnetic stimulation (rMS) on myofascial pain. METHODS: Eighteen patients who presented with myofascial trigger points (TPs) at the level of the superior trapezius were separated into two groups according to a restricted randomization scheme. Group 1 (n=9) underwent treatment with rMS that consisted of a total of 10 sessions, each lasting 20min, in which 4000 magnetic stimuli were administered in 5s trains at 20Hz at the TP. Group 2 (n=9) received a placebo treatment that consisted of the application of a non-functioning ultrasound therapy device to the TP. Patients were evaluated before treatment, at the end of treatment, and again 1 week and 1 month after the conclusion of the treatment. Clinical evaluation included parameters for measuring pain levels (VAS, NPDVAS and algometry), the myofascial TP characteristics and the range of cervical movement (ROM). RESULTS: The rMS group showed a significant improvement in VAS, NPDVAS, algometry, as well as in the characteristics of the TP after conclusion of treatment. Improvements in the ROM were also present in rotation and controlateral bending. This improvement persisted after 1 month. On the other hand, the placebo group did not show any significant improvement in the tests considered. CONCLUSIONS: The results of this study show that peripheral rMS may have positive short- and medium-term therapeutic effects on myofascial pain.

The effect of two different rehabilitation treatments in cervical dystonia: preliminary results in four patients.

The most widespread approach to rehabilitation of cervical dystonia is electromyographic (EMG) biofeedback. However, consensus is lacking regarding the true effectiveness of this technique. The aim of this study was to evaluate how cervical dystonia was influenced by two rehabilitative treatments, namely a standard biofeedback program and a novel physiotherapy program consisting of postural reeducation exercises and passive elongation of myofascial cervical structures. Both programs were consecutively administered to 4 patients with cervical dystonia. The study design was a behavioral analysis of single cases. The main outcome measures were a head realignment test, a disability questionnaire and a pain visual analogue scale (VAS). Each patient's performance was evaluated before the study and after the first and second program. Furthermore, the disability questionnaire and the pain VAS were administered 3, 6, and 9 months after the end of the treatments. The physiotherapy program showed therapeutic effects comparable to those of EMG biofeedback. Reductions of disability and of pain were still present 3-9 months after the end of the treatments. These preliminary results suggest that the physiotherapy program proposed in the present study may be a promising method for rehabilitation of cervical dystonia.

Deficits of temporal discrimination in dystonia are independent from the spatial distance between the loci of tactile stimulation.

To assess whether spatial variables influence deficits of temporal somesthetic discrimination in dystonic patients, 10 patients with idiopathic dystonia and 12 healthy controls were tested with pairs of non-noxious electrical stimuli separated by different time intervals. Stimuli were delivered: (1) to the pad of the index finger (same-point condition), (2) to the pad and to the base of the index finger (same-finger condition), and (3) to the pad of the index and ring fingers (different-finger condition). Subjects were asked to report whether they perceived single or double stimuli in the first condition and synchronous or asynchronous stimuli in the second and third conditions. Somesthetic temporal discrimination thresholds (STDTs) were obtained by computing the shortest time interval at which stimuli, applied to the left or the right hand, were perceived as separate in the first condition or asynchronous in the second and third conditions. STDTs were significantly higher in dystonic patients than controls in all three conditions. In both dystonia patients and controls, STDTs resulted highest in conditions whereby stimuli were maximally separated in space. Results extend current knowledge of deficits of somesthetic temporal discrimination in dystonia by showing that temporal deficits are not influenced by spatial variables.