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Biomedical subjects

P A Tonali

Publications and source records attributed to P A Tonali.

At least 19 recordsLinked to original sources
PubMed2006

Origin of facilitation of motor-evoked potentials after paired magnetic stimulation: direct recording of epidural activity in conscious humans.

A magnetic transcranial conditioning stimulus given over the motor cortex at intensities below active threshold for obtaining motor-evoked potentials (MEPs) facilitates EMG responses evoked at rest in hand muscles by a suprathreshold magnetic stimulus given 10-25 ms later. This is known as intracortical facilitation (ICF). We recorded descending volleys produced by single and paired magnetic motor cortex stimulation through high cervical epidural electrodes implanted for pain relief in six conscious patients. At interstimulus intervals (ISIs) of 10 and 15 ms, although MEP was facilitated, there was no change in the amplitude or number of descending volleys. An additional I wave sometimes was observed at 25 ms ISI. In one subject, we also evaluated the effects of reversing the direction of the induced current in the brain. At 10 ms ISI, the facilitation of the MEPs disappeared and was replaced by slight suppression; at 2 ms ISI, there was a pronounced facilitation of epidural volleys. Subsequent experiments on healthy subjects showed that a conditioning stimulus capable of producing ICF of MEPs had no effect on the EMG response evoked by transmastoidal electrical stimulation of corticospinal tract. We conclude that ICF occurs because either 1) the conditioning stimulus has a (thus far undetected) effect on spinal cord excitability that increases its response to the same amplitude test volley or 2) that it can alter the composition (but not the amplitude) of the descending volleys set up by the test stimulus such that a larger proportion of the activity is destined for the target muscle.

Adult↗
PubMed2006

In vivo cholinergic circuit evaluation in frontotemporal and Alzheimer dementias.

The test of short latency afferent inhibition (SAI) of the motor cortex is helpful in demonstrating dysfunction of central cholinergic circuits in Alzheimer disease (AD). The authors evaluated SAI in 20 patients with frontotemporal dementia (FTD) and compared data with those from 20 patients with AD and 20 controls. SAI was normal in FTD, whereas it was reduced in AD. SAI may represent an additional tool to discriminate FTD from AD.

Afferent Pathways↗
PubMed2006

Effects of aging on motor cortex excitability.

To determine whether aging is associated with changes in excitability of the cerebral cortex, we evaluated the excitability of the motor cortex with transcranial magnetic stimulation (TMS). We compared TMS related measures obtained in a group of young people with those of a group of old people. Motor evoked potential (MEP) amplitude was significantly smaller in older than in younger controls (1.3+/-0.8 mV versus 2.7+/-1.1 mV; p<0.0071). Mean cortical silent period (CSP) duration was shorter in older than in younger controls (87+/-29 ms versus 147+/-39 ms; p<0.0071). SP duration/MEP amplitude ratios were similar in both groups. Our results are consistent with an impaired efficiency of some intracortical circuits in old age.

Adult↗
PubMed2006

NCAM is hyposialylated in hereditary inclusion body myopathy due to GNE mutations.

The authors found that the neural cell adhesion molecule (NCAM) is hyposialylated in hereditary inclusion body myopathy (HIBM) muscle, as suggested by its decreased molecular weight by Western blot. This abnormality represented the only pathologic feature differentiating HIBM due to GNE mutations from other myopathies with similar clinical and pathologic characteristics. If further confirmed in larger series of patients, this may be a useful diagnostic marker of GNE-related HIBM.

Adult↗
PubMed2006

Dysfunction of arousal systems in sleep-related migraine without aura.

Primary headaches are closely related to sleep. Modifications in the patterns of arousal during sleep have been reported in migraine, especially in the nights preceding a headache attack. We aimed at evaluating the pattern of arousal from sleep in a group of patients affected by sleep-related migraine. We enrolled 10 consecutive patients, three males and seven females, aged between 20 and 62 years, who presented frequent attacks of migraine without aura (more than five per month), closely related to sleep (more than one-half of the attacks occurred during sleep, causing an awakening). A control group was studied, matched for age and sex. Patients and controls underwent a full-night polysomnographic study, following adaptation; arousal pattern was studied by the scoring of the high-frequency EEG arousal and by the cyclic alternating pattern (CAP). Migraineurs showed a lower CAP rate in non-rapid eye movement (NREM) sleep and, in particular, a lower number of A1 phases (low-frequency, high-amplitude EEG bursts) compared with the controls. Migraineurs also showed a lower index of high-frequency EEG arousals during rapid eye movement (REM) sleep. The reduction in the CAP rate indicates a lower level of arousal fluctuation in NREM sleep. The reduced arousal index in REM suggests a dysfunction in neural structures involved in both the control of REM sleep and the pathophysiology of migraine, such as the hypothalamus and the brainstem.

Adult↗
PubMed2005

Theta-burst repetitive transcranial magnetic stimulation suppresses specific excitatory circuits in the human motor cortex.

In four conscious patients who had electrodes implanted in the cervical epidural space for the control of pain, we recorded corticospinal volleys evoked by single-pulse transcranial magnetic stimulation (TMS) over the motor cortex before and after a 20 s period of continuous theta-burst stimulation (cTBS). It has previously been reported that this form of repetitive TMS reduces the amplitude of motor-evoked potentials (MEPs), with the maximum effect occurring at 5-10 min after the end of stimulation. The present results show that cTBS preferentially decreases the amplitude of the corticospinal I1 wave, with approximately the same time course. This is consistent with a cortical origin of the effect on the MEP. However, other protocols that lead to MEP suppression, such as short-interval intracortical inhibition, are characterized by reduced excitability of late I waves (particularly I3), suggesting that cTBS suppresses MEPs through different mechanisms, such as long-term depression in excitatory synaptic connections.

Aged↗
PubMed2005

Multicenter study on carpal tunnel syndrome and pregnancy incidence and natural course.

OBJECTIVE: To evaluate the incidence of carpal tunnel syndrome (CTS) in pregnancy through a validated and multiperspective assessment of CTS and to assess the course of carpal tunnel syndrome after pregnancy. METHODS: During 2000-2001, the Italian CTS study group in 7 Italian centers studied the occurrence of CTS in women during the last period of pregnancy. The group enrolled and followed-up (10-15 months) 63 women during and after pregnancy with multiple measurements of CTS. In addition to the physician-centered and neurophysiologic traditional evaluations, a validated patient-oriented measurement to obtain more comprehensive and consistent data for severity of symptoms and functional impairment was adopted. RESULTS: CTS was clinically diagnosed in more than half of women (62%). Neurophysiological evaluation provided diagnosis of CTS in around half of women (43% were positive in one hand at least). Comparison of baseline and follow-up data showed a significant spontaneous improvement of patient-oriented and neurophysiologic measurements. Nevertheless, about half of women with CTS during pregnancy still complained of CTS symptoms one year after delivery. CONCLUSIONS: Our observations confirmed the frequent occurrence of CTS in pregnancy. At follow-up we observed that most CTS cases improve spontaneously without treatment but only in half of women CTS symptoms disappeared one year after delivery.

Adult↗
PubMed2005

Functional involvement of cerebral cortex in human narcolepsy.

The pathophysiology of human narcolepsy is still poorly understood. The hypoactivity of some neurotransmitter systems has been hypothesised on the basis of the canine model. To determine whether narcolepsy is associated with changes in excitability of the cerebral cortex, we assessed the excitability of the motor cortex with transcranial magnetic stimulation (TMS) in 13 patients with narcolepsy and in 12 control subjects. We used several TMS paradigms that can provide information on the excitability of the motor cortex. Resting and active motor thresholds were higher in narcoleptic patients than in controls and intracortical inhibition was more pronounced in narcoleptic patients. No changes in the other evaluated measures were detected. These results are consistent with an impaired balance between excitatory and inhibitory intracortical circuits in narcolepsy that leads to cortical hypoexcitability. We hypothesise that the deficiency of the excitatory hypocretin/orexin-neurotransmitter-system in narcolepsy is reflected in changes of cortical excitability since circuits originating in the lateral hypothalamus and in the basal forebrain project widely to the neocortex, including motor cortex. This abnormal excitability of cortical networks could be the physiological correlate of excessive daytime sleepiness and it could be the substrate for allowing dissociated states of wakefulness and sleep to emerge suddenly while patients are awake, which constitute the symptoms of narcolepsy.

Adult↗
PubMed2005

Clinical characteristics, course and prognosis of spinal multiple sclerosis.

STUDY DESIGN: Retrospective examination. OBJECTIVE: To define the clinical characteristics and response to therapy of spinal multiple sclerosis (MS). SETTING: Italy. METHODS: Retrospective review was performed on 563 patients with clinical definite MS. Selection criteria were two or more spinal cord lesions in the presence of normal magnetic resonance imaging of the brain. RESULTS: Spinal MS was diagnosed in 13 patients (2.3%) out of 563 with clinical definite MS. There were seven female and six male patients; nine had a relapsing-remitting (RR) and four, a primary progressive (PP) course. All patients were treated with immunosoppressive or immunomodulatory therapy. Mean disease duration in patients with RR-MS was 13.1+/-10.1 years with a mean age at onset of 29.5+/-14.3 years; the mean Expanded Disability Status Scale (EDSS) at the time of the study was 3.5+/-2.5 with a progression index of 0.28. Mean disease duration in patients with PP course was 7+/-6.2 years with a mean age at onset of 56.7+/-10.4 years; the mean EDSS at the time of the study was 6.2+/-2.0 with a progression index of 1.48. CONCLUSIONS: Patients with spinal RR-MS are characterised by an early disease onset with minimal or moderate disability progression; patients with spinal PP-MS show a late disease onset and more rapid disability progression. In our series of spinal MS patients, disability progression seems to be mainly due to the disease course and age at onset rather than to the site of lesion.

Adolescent↗