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A Quartarone

Publications and source records attributed to A Quartarone.

At least 19 recordsLinked to original sources
PubMed2006

The basal ganglia are hyperactive during the discrimination of tactile stimuli in writer's cramp.

Writer's cramp is a focal hand dystonia that specifically affects handwriting. Though writer's cramp has been attributed to a dysfunction of the basal ganglia, the role of the basal ganglia in the pathogenesis of writer's cramp remains to be determined. Seventeen patients with writer's cramp (nine females; age range: 24-71 years) and 17 healthy individuals (six females; age range: 27-68 years) underwent functional MRI (fMRI) while they discriminated the orientation of gratings delivered to the tip of the right index finger. Statistical parametric mapping was used to analyse the fMRI data. The significance level was set at a corrected P-value of 0.05. Relative to healthy controls, patients with writer's cramp showed a widespread bilateral increase in task-related activity in the putamen, caudate nucleus, internal globus pallidus and lateral thalamus. In these areas, hyperactivity was more pronounced in patients who had recently developed writer's cramp. The enhanced response of the basal ganglia to tactile input from the affected hand is compatible with the concept of impaired centre-surround inhibition within the basal ganglia-thalamic circuit and may lead to an excessive activation of sensorimotor cortical areas during skilled movements affected by dystonia. Outside the basal ganglia, dystonic patients showed task-related overactivity in visual cortical areas, left anterior insula and right intraparietal sulcus, but not in the primary or secondary sensory cortex. In addition, task-related activity in the cerebellar nuclei, posterior vermis, right paramedian cerebellar hemisphere and dorsal pons was inversely related with the severity of hand dystonia. Regional activity in these areas may reflect secondary adaptive reorganization at the systems level to compensate for the dysfunction in the basal ganglia-thalamic loop.

Adult↗
PubMed2005

Transcranial magnetic stimulation as trigger of dystonic attacks in a patient affected by paroxysmal kinesigenic dyskinesia.

A 22-year-old patient presented with attacks of paroxysmal dystonia characterised by involuntary and uncontrollable movements affecting lower and upper limbs with sustained turning or twisting of the trunk. These motor paroxysms were induced by voluntary movements and lasted between 10 and 15 s with a frequency of 1-5 attacks per day. Transcranial magnetic stimulation of the motor cortex was found to induce motor paroxysms very similar to the spontaneous attacks. To evaluate motor cortex and brainstem excitability immediately after and between the attacks, a neurophysiological study was performed.

Adult↗
PubMed2004

One-hertz subthreshold rTMS increases the threshold for evoking inhibition in the human motor cortex.

Despite indisputable evidence that repetitive transcranial magnetic stimulation (rTMS) modulates motor cortical excitability, the effects of subthreshold low-frequency rTMS on intracortical inhibition (ICI) are controversial. In this paper we investigated whether increasing the level of baseline ICI increases the sensitivity of ICI for disclosing the after-effects of rTMS on cortical excitability. In experiment 1, we studied changes in ICI, tested at two different baseline levels, after a train of 900 subthreshold rTMS pulses delivered at 1 Hz. In experiment 2, we studied whether the same conditioning rTMS train changed the ICI threshold, and in experiment 3 whether it changed the facilitatory I-wave interaction. Conditioning rTMS reduced ICI tested at a baseline level of 75% but left ICI tested at a baseline level of 50% unchanged. It also increased the ICI threshold but left the facilitatory I-wave interaction unchanged. These findings suggest that conditioning rTMS selectively reduced ICI tested at a baseline level of 75% by increasing the threshold for evoking inhibition in the motor cortex. The inhibitory system mediating ICI may therefore be more efficient than other motor cortical systems in reducing high cortical excitability after external intervention. Hence studies investigating the after-effects of rTMS should standardize ICI levels at baseline.

Adult↗
PubMed2002

Different patterns of I-waves summation in ALS patients according to the central conduction time.

OBJECTIVES: To study facilitatory I-waves interaction, using two near threshold stimuli, to test both excitability and conductivity changes related to cortico-motoneuronal involvement in amyotrophic lateral sclerosis (ALS) patients in different stages of the disease. METHODS: Pairs of threshold magnetic stimuli were applied over the motor cortex at inter-stimulus intervals (ISI) ranging from 1-1.5 to 2.5-3 ms and from 4 to 4.5ms. The electromyogram responses were recorded from relaxed first dorsal interosseus (FDI). RESULTS: The data of I-waves summation were distributed according to the central conduction time (CCT) and all 3 peaks of facilitation were considered for statistical analysis. Patients with normal CCT showed a normal I-waves summation for the first peak, whilst patients with abnormal CCT had a significant reduction in facilitation (P<0.02). Six out of 11 patients with normal CCT had facilitation in the first peak, which exceeded 2 SD of normal values. CONCLUSIONS: In conclusion ALS patients showed two different and opposite patterns of I-waves summation which could be related to different stages of the disease.

Adolescent↗
PubMed2001

Modification of cortical excitability induced by gabapentin: a study by transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) was employed before and after a single dose of gabapentin to evaluate how this drug affects the activity of excitatory and inhibitory circuits within the motor cortex. Eleven healthy volunteers were studied. For the evaluation of cortical excitability, the following parameters were taken into account: resting and active motor threshold (RMT, AMT); cortical silent period (CSP); and intracortical inhibition (ICI) and facilitation (ICF). Peripheral silent period (PSP) was also detected. All parameters were measured before and 3 and 24 hours after 800 mg gabapentin was administered in a single oral dose. Gabapentin deepened the ICI and suppressed the ICF at 3 h but not at 5 h after dosing. We conclude that, in the normal human brain, gabapentin may act on intracortical excitability by shifting the balance towards less excitation and more inhibition.

Acetates↗
PubMed2001

Segmental myoclonus in a patient affected by syringomyelia.

We describe a patient who has been complaining of brief jerk-like, rhythmic, involuntary movements involving the second digit of the left hand for the last three months. These involuntary jerks produced an adduction movement of the second digit and were unaffected by peripheral sensory stimuli. In addition, the patient experienced loss of dexterity in the left hand. On examination the patient showed hypotrophy of the first dorsal interosseous (FDI) muscle of the left hand and a dissociated sensory loss involving the C8-T1 dermatomes. Magnetic resonance imaging of the brain and spinal cord revealed a tonsilar hemiation characteristic of the Chiari I malformation associated with a syrinx extending from C4 to D5 that did not communicate with the fourth ventricle. The electrophysiological evaluation indicated the presence of a focal myoclonus of spinal origin that is likely to be caused by the syrinx.

Arnold-Chiari Malformation↗
PubMed2000

Changes in spinal cord excitability in patients affected by ulnar neuropathy.

OBJECTIVE: To evaluate whether ulnar neuropathy could induce changes in spinal cord and motor cortex excitability and therefore predispose to development of focal dystonia. BACKGROUND: A high incidence of ulnar neuropathy has been observed in patients with musician's cramp. Polygraphic electromyograph recordings in patients with entrapment of the ulnar nerve at the elbow have demonstrated long-duration bursts of co-contraction in antagonistic muscles, similar to those observed in focal dystonia. METHODS: All control subjects and 12 patients with ulnar neuropathy underwent an electrophysiologic protocol consisting of polygraphic recordings of a repetitive tapping task of the fourth finger, assessment of reciprocal inhibition in forearm muscles, and investigation of motor cortex excitability after paired transcranial magnetic stimulation. RESULTS: Eleven of 12 patients with ulnar neuropathy showed a loss of alternation and of well-formed bursts in both flexor and extensor muscles. Evaluation of reciprocal inhibition in these patients revealed a reduction in the amount of inhibition in the disynaptic and presynaptic phases. None of the patients presented with a clinically evident dystonia of the upper limb. The study of intracortical excitability after paired shocks did not reveal any difference in the amount of intracortical inhibition and facilitation compared with the control group. CONCLUSIONS: A peripheral nerve injury can induce a rearrangement of reciprocal inhibition circuits at the spinal cord level. These changes might predispose to the development of a focal dystonia. However, it is likely that another, yet unknown, factor is required to alter the intracortical circuits and produce a clinically evident dystonia.

Adult↗
PubMed2000

Interhemispheric threshold differences in idiopathic generalized epilepsies with versive or circling seizures determined with focal magnetic transcranial stimulation.

The interhemispheric difference of the motor-cortical threshold (IDMT) was studied with focal magnetic transcranial stimulation (TCS) in ten patients with idiopathic generalized epilepsy (IGE) who also displayed versive or circling seizures (IGEvc). The data were compared with those obtained from two control groups; 13 patients with IGE without asymmetrical motor seizures, and 25 normal volunteer subjects. The IDMT, referred to as the percentage of maximum stimulator output, was assessed by focal TCS applied to the hand areas. Seven patients with IGEvc and only one patient with IGE had an interhemispheric motor threshold beyond the normal range. The IDMT in IGEvc patients was significantly higher compared to that of IGE patients and normal individuals. An interhemispheric imbalance of cortical excitability may explain lateralized ictal motor manifestations in patients with IGEvc.

Adolescent↗
PubMed2000

Short latency trigemino-sternocleidomastoid response in muscles in patients with spasmodic torticollis and blepharospasm.

OBJECTIVES: To further elucidate the pathogenesis of focal dystonias. METHODS: Short latency responses can be recorded in tonically active sternocleidomastoid muscles after stimulation of the infraorbital branch of the trigeminal nerve. Such trigemino-sternocleidomastoid response consists of a bilateral positive/negative wave in the average of unrectified surface EMG, corresponding to a short period of inhibition of motor unit firing. This brain stem reflex was investigated in 10 normal subjects, in 16 patients affected by spasmodic torticollis (ST) and in 10 patients with blepharospasm (BSP). RESULTS: All ST patients presented abnormalities of SCM responses after infraorbital nerve stimulation. The abnormalities were bilateral in all but one of the patients and were independent from previous treatment with botulinum toxin. No BSP patients showed alterations of this reflex. CONCLUSIONS: Abnormalities of brain stem interneurons which are responsible for oligosynaptic exteroceptive suppression reflexes occur specifically in ST. These findings further support the relevance of sensory inputs in the determinism of focal dystonias.

Adult↗
PubMed1999

Electrophysiological study of neuromuscular system involvement in mitochondrial cytopathy.

OBJECTIVES: To define the neuromuscular involvement in 'mitochondrial' patients with clinical evidence of a neuromuscular disorder, and to evaluate if the proposed electrophysiological protocol was suitable to reveal a subclinical neuropathy or myopathy in 'mitochondrial' patients with no clinical sign of a neuromuscular disturbance. METHODS: Quantitative concentric needle electromyography (CNEMG), single fiber electromyography (SFEMG) and nerve conduction studies (NCS) were performed in 33 patients with mitochondrial cytopathies. Lastly, we studied 9 clinically unaffected relatives. RESULTS: NCS were abnormal in 18% of patients, with CNEMG and SFEMG in 58% of cases, but there was not a complete overlapping of the positivity of the different techniques. No asymptomatic relatives showed abnormalities of the electrophysiological studies. CONCLUSIONS: Electrophysiological findings did not correlate with any specific biochemical or genetic defect, but were consistent with clinical diagnosis in almost all of the patients with clinical signs of myopathy and/or neuropathy. Increase of both SFEMG jitter and fiber density was significantly tied to a neuropathic process. CNEMG and SFEMG were altered in about 30% of subjects without clinical signs of myopathy or neuropathy and were therefore able to reveal a subclinical involvement of neuromuscular system in some patients who had external ophthalmoplegia or retinitis only.

Adolescent↗
PubMed1998

Electrophysiological studies in mild idiopathic carpal tunnel syndrome.

Many techniques have been reported to improve the diagnosis of carpal tunnel syndrome (CTS), but there is no agreement on the diagnostic yield of these different methods. We used an electrophysiological protocol including the assessment of the orthodromic sensory conduction velocity of the median nerve along the carpal tunnel, comparison of median and ulnar sensory conduction between the ring finger and wrist, short segment incremental median sensory nerve conduction across the carpal tunnel recording from the III digit ('inching test'), the study of the refractory period of transmission (RPT) and calculation of the distoproximal ratio obtained by dividing the nerve conduction velocity in the median nerve between the third digit and the palm and between the palm and wrist in 41 patients with mild CTS (75 symptomatic hands) and in 45 control subjects. The distoproximal ratio calculation was the most sensitive technique (81%), but was also the least specific. The 'inching test', even though less sensitive, had the advantage of localising focal abnormalities of the median nerve along the carpal tunnel. RPT was abnormal in patients with recent symptoms. Combining the different techniques, an overall sensitivity of 92% was reached, 11% higher than the yield of the single best test suggesting that a multimodal approach could be useful. The best procedure for electrodiagnosis of mild CTS was to combine the median/ulnar comparison test with calculation of the disto-proximal ratio.

Adult↗
PubMed1998

Focal hand dystonia in a patient with thoracic outlet syndrome.

A patient affected by thoracic outlet syndrome, with an involvement of the left lower primary trunk due to a rudimentary cervical rib, developed a severe hand dystonia on the same side. The dystonic posture was characterised by a flexion of the wrist with the fingers curled into the palm. Polygraphic recordings performed on the left flexor digitorum superficialis (FDS4) and extensor digitorum superficialis (EDC4) muscles, during a repetitive tapping task of the fourth digit, showed a loss of well formed bursts without a clear silent period along with long duration bursts of cocontraction in antagonistic muscles. The study of reciprocal inhibition between forearm flexor and extensor muscles showed a reduced amount of inhibition in both the disynaptic and the later presynaptic phase of inhibition. The patient underwent an operation with resection of the cervical rib. Twelve hours after the operation the patient experienced a significant improvement of the hand dystonia; the distonia had disappeared completely by two months with a progressive normalisation of reciprocal inhibition.

Adult↗
PubMed1997

Botulinum toxin in upper limb spasticity: study of reciprocal inhibition between forearm muscles.

To establish whether botulinum A toxin (BTX-A) acts on modifying reciprocal inhibition between forearm muscles in spasticity, 20 patients with post-stroke upper limb spasticity lasting for more than 1 year were studied. Clinical examination, physiotherapeutic evaluation, standardized video-tape assessment and electrophysiological testing (flexor carpi radialis muscle M and H responses with study of reciprocal inhibition) were performed at baseline and 2 weeks, 1, 2, 3, 4 months after BTX-A treatment. BTX-A induced a significant decrease of tone and an improvement of motility and functional status, with a significant decrease of the M wave and the H reflex. The reduction in both inhibitory phases of reciprocal inhibition did not change after BTX-A treatment differently from that reported in upper limb dystonia. These findings indicate that the efficacy of BTX-A in upper limb spasticity is mainly due to peripheral effects.

Aged↗
PubMed1997

Extra-muscle involvement in dystrophinopathies: an electroretinography and evoked potential study.

Dystrophin is present in various tissues other than skeletal and cardiac muscles, including the central nervous system (CNS) and the outer plexiform layer of the retina. Therefore lack of dystrophin might be related to mental retardation or to changes in electrophysiological tests exploring retina and CNS. We performed electroretinography, VEPs, BAEPs, SEPs and MEPs in 18 patients with Duchenne muscular dystrophy (DMD), 18 with Becker muscular dystrophy (BMD) and 12 obligate carriers. We observed a marked reduction of the b-wave amplitude in the scotopic ERG, mainly in DMD patients. Oscillatory potentials were altered in all groups, even in carriers, suggesting that dystrophin may be also involved in retinal circulation. VEPs changes confirmed the role of dystrophin in visual function. The other evoked potentials were altered only in a small percentage of subjects but changes of different tests did not overlap in individual subjects. Neurophysiological abnormalities did not correlate with type, site and size of alteration in the dystrophin gene.

Adolescent↗
PubMed1996

Unilateral injection of botulinum toxin in blepharospasm: single fiber electromyography and blink reflex study.

We studied six patients affected with blepharospasm (BSP). We injected botulinum toxin (BTX) around only one eye and saline solution around the other. Clinical rating of BSP was performed. Single fiber electromyography (SFEMG), compound motor action potential (cMAP) at the orbicularis oculi muscle by stimulation of the facial nerve, blink reflex, and blink reflex recovery curve were recorded. All clinical and electrophysiological investigations were carried out before, and 1, 2, and 4 weeks after treatment. Evidence of bilateral clinical benefit was provided. Following therapy, facial cMAP decreased bilaterally and SFEMG revealed statistically significant changes on both sides while the excitability curve of blink reflex remained unmodified. The results confirm that BTX affects merely the neuromuscular junctions. The clinical and neurophysiological effects are present on both sides also for unilateral injection probably because of toxin spreading.

Aged↗
PubMed1996

Preliminary clinical observations on a new trigeminal reflex: the trigemino-cervical reflex.

Short latency trigemino-cervical reflexes can be recorded from sternocleidomastoid muscle after stimulation of the infraorbital branch of the trigeminal nerve. We studied the trigemino-cervical reflexes and the conventional blink reflex in three patients with an isolated lesion in the medulla oblongata, eight patients with multiple sclerosis, and two patients with supratentorial ischemic lesion. The trigemino-cervical response was abnormal in the patients with an isolated lesion in the medulla oblongata and in all multiple sclerosis patients, whereas both components of the blink reflex were preserved in the patients with a lesion in the medulla oblongata and in half of the patients with multiple sclerosis. The trigemino-cervical reflex was preserved in patients with supratentorial lesions, whereas the late component of the blink reflex was abnormal. These findings suggest that central pathways generating the trigemino-cervical reflex are confined to the medulla oblongata and that they are independent from those generating the long latency (R2) component of the blink reflex. The trigemino-cervical reflex may help in disclosing and localizing brainstem lesions.

Adult↗
PubMed1995

Click-evoked vestibulocollic reflexes in torticollis.

A total of 26 patients with torticollis were studied using a recently developed technique for recording vestibulocollic reflexes from the sternocleidomastoid muscles in addition to conventional caloric tests of vestibular function. Previous reports of abnormalities of vestibulo-ocular reflexes in these patients were confirmed with just fewer than half having significant canal pareses or directional preponderances (nine of 20 tested). In addition, there was a high incidence of abnormal click-evoked vestibulocollic reflexes (17 of 26 tested), which were not simply the result of prior treatment with botulinum toxin, nor due to unequal levels of muscle activation. In patients never previously treated with botulinum toxin (14 patients), the effect almost always consisted of suppressed responses in the sternocleidomastoid muscle ipsilateral to the direction of head turning. Because responses were not abnormal in all patients tested, and more commonly so in those with a history of torticollis of > or = 5 years (eight of nine patients) than in de novo patients, we suggest that the changes are more likely to be compensatory than causal.

Acoustic Stimulation↗