Biomedical subjects

B Fierro

Publications and source records attributed to B Fierro.

At least 19 recordsLinked to original sources

PubMed2005

Hypo-excitability of cortical areas in patients affected by Friedreich ataxia: a TMS study.

The aim of the study was to explore excitability of a motor and a non-motor (visual) area in patients affected by Friedreich ataxia and to correlate neurophysiological data with clinical parameters. Seven patients (3M/4F) and ten healthy controls (5M/5F) participated in the study. The hot-spot for activation of right abductor pollicis brevis was checked by means of a figure-of-eight coil and the motor threshold (MT) on this point was recorded. The phosphene threshold (PT) was measured by means of a focal coil over the occipital cortex as the lower intensity of magnetic stimulation able to induce the perception of phosphenes. The patients showed a significantly higher mean PT (p<.03) and MT values (p<.001) than controls. In all but one patient unable to perceive phosphenes (42% vs. 50% of controls), TMS at 100% intensity did not elicit motor response at rest. The difference in percentage of patients (57.1%) and controls (100%) with motor responses was nearly significant. The size of GAA1 expansion showed significant correlations with PT and MT values. The results of our study showed that FA patients had reduced cortical activation, involving both the motor and the visual cortex. The cortical involvement in these patients seems to be mainly genetically determined. The study provides the first evidence of cortical dysfunction in patients with genetically defined Friedreich ataxia.

Adolescent↗

PubMed2003

1 Hz rTMS enhances extrastriate cortex activity in migraine: evidence of a reduced inhibition?

We recently reported a paradoxical facilitatory effect of 1 Hz repetitive TMS (rTMS) on the primary visual cortex in migraine possibly due to the failure of inhibitory circuits, unable to be upregulated by low frequency rTMS. To investigate if inhibitory circuit dysfunction extends beyond striate cortex in migraine with aura, we studied the effects of 1 Hz rTMS over the right extrastriate cortex on perception of illusory contours in these patients. Low-frequency rTMS enhanced activity of extrastriate cortex in migraineurs, speeding up reaction times on illusory contour perception. This finding supports the view of a failure of inhibitory circuits also involving the extrastriate cortex in migraine with aura.

Adult↗

PubMed2003

1 Hz repetitive transcranial magnetic stimulation of the unaffected hemisphere ameliorates contralesional visuospatial neglect in humans.

The aim of the study was to investigate whether low-frequency repetitive transcranial magnetic stimulation (rTMS) over the unaffected hemisphere can ameliorate visuospatial neglect. We treated three right brain damaged patients with left neglect. 900 pulses (1 Hz frequency) were given over left posterior parietal cortex every other day for 2 weeks. Patients performed a computerized task requiring length judgement of prebisected lines, tachistoscopically presented for 150 ms. With respect to rTMS the task was given 15 days before, at the beginning, at the end and 15 days after. At these times patients performed also line bisection and clock drawing tasks. rTMS induced a significant improvement of visuo-spatial performance that remained quite unchanged 15 days after. Patients performance at Time 3 and 4 improved also as concerns line bisection and clock drawing tasks.

Aged↗

PubMed2003

Illusory contours and specific regions of human extrastriate cortex: evidence from rTMS.

Functional magnetic resonance imaging studies showed that perception of illusory contours is associated with extrastriate cortex activation prevailing on the right side. 1 Hz repetitive transcranial magnetic stimulation (rTMS) is able to induce lasting inhibition of cortical activity. The objective of the study was to investigate the role of extrastriate cortex in illusory contour perception inducing 1 Hz rTMS interference in healthy subjects. Eight healthy subjects underwent 1 Hz rTMS (600 pulses) through a figure-of-eight coil over right and left occipital cortex (O1 and O2 of 10/20 EEG system); sham magnetic stimulation on the same sites and right motor cortex rTMS (in three subjects) were given as control. Subjects performed a computerized task requiring perception of illusory and real contours of Kanizsa squares in baseline and after rTMS. After stimulus presentation the subject made a forced-choice decision about the regularity or irregularity of stimulus contour, by hitting as fast as possible one of two keys on the computer keyboard. Reaction times (RT) were measured. Right occipital stimulation significantly increased RT for illusory contour perception (vs. baseline, P < 0.05). No significant RT changes were observed in the other experimental conditions with respect to the baseline condition. It is concluded that 1Hz rTMS of right extrastriate cortex can disrupt perception of illusory contours and the effect appears to be side-specific, being evident only after right occipital stimulation. This study supports the critical role of right extrastriate cortex in illusory contour perception.

Adult↗

PubMed2002

A transcranial magnetic stimulation study evaluating methylprednisolone treatment in multiple sclerosis.

OBJECTIVE: To investigate the efficacy of two different high doses of intravenous methylprednisolone (IVMP) during Multiple Sclerosis (MS) relapses. BACKGROUND: Transcranial Magnetic Stimulation (TMS) is the most sensitive neurophysiological ascertainment to quantify motor disability, to follow the recovery from an MS relapse, and to detect the response to treatment. DESIGN AND METHOD: Twenty-four clinically definite relapsing - remitting MS patients presenting a relapse were randomly assigned to a treatment for 5 days with IVMP 1 or 2 g/day. The response to treatment of each patient was evaluated through Expanded Disability Status Scale (EDSS), Medical Research Council (MRC) score, and TMS by means of motor evoked potential (MEP) parameters. RESULTS: Motor threshold (MT), central motor conduction time (CMCT) and MRC showed a higher improvement with the highest dose of IVMP. Silent period and EDSS improved with both treatments. CONCLUSION: The dose of 2 g/day of IVMP is more effective in MS relapse.

Adult↗

PubMed2001

rTMS of the unaffected hemisphere transiently reduces contralesional visuospatial hemineglect.

To verify the role of interhemispheric influences on manifestations of neglect, the authors investigated the effects of a transient repetitive transcranial magnetic stimulation (rTMS)-induced disruption of the unaffected hemisphere on contralesional visuospatial neglect in two left- and five right-brain-damaged patients. Parietal rTMS of the unaffected hemisphere during the execution of a computerized task of bisected line's length judgment transiently decreased the magnitude of neglect as expressed in the number of errors.

Aged↗

PubMed2001

Timing of right parietal and frontal cortex activity in visuo-spatial perception: a TMS study in normal individuals.

In a recent study we showed that repetitive transcranial magnetic stimulation (rTMS) with train duration of 400 ms over right frontal and right posterior parietal cortices gives rise to transitory contralateral visuo-spatial neglect in normal subjects. In the present experiment we investigated whether using single-pulse TMS it is possible to obtain information about the timing of cortical activity related to spatial cognition. Nine healthy subjects performed in baseline condition and during TMS a tachistoscopic task, requiring a forced-choice estimation of the length of the two segments of prebisected horizontal lines. Single-pulse TMS was triggered at various time intervals (150 ms, 225 ms, 300 ms) after visual stimulus onset with a focal coil over P6 and F4 (according to 10/20 EEG system). Relative transitory rightward bias was observed only when parietal TMS was delivered 150 ms after visual stimulus presentation. Frontal stimulation induced no effect on visuo-spatial perception with the time intervals explored.

Adult↗

PubMed2001

Modulation of intracortical inhibition induced by low- and high-frequency repetitive transcranial magnetic stimulation.

We studied the changes of duration of subsequent silent periods (SPs) during repetitive magnetic stimulation (rTMS) trains of ten stimuli delivered at low (1 Hz) and high (7 Hz) frequencies. The effects at different intensities of stimulation (motor threshold, MT, 115% and 130% above the MT) were also evaluated. rTMS was performed in eight healthy subjects with a figure-of-eight coil placed over the hand motor area. The SP was recorded from abductor pollicis brevis (APB) muscle during a voluntary contraction of 30% of maximum effort. rTMS at 1-Hz frequency progressively decreased the duration of SP, whereas an alternating pattern of smaller and larger values was observed during trains at 7-Hz frequency and higher stimulus intensity. The findings show that rTMS changes the duration of cortical SPs; the effect is probably due to the modulation of intracortical inhibitory interneurons depending on the frequency and intensity of stimulation.

Adult↗

PubMed2001

Auditory event-related potentials (P300) in epileptic patients.

Auditory event-related potentials (AERPs) were recorded during an auditory oddball paradigm in 108 epileptics and in 32 healthy controls. P300 latency varied in relationship with age only in controls. Symptomatic epileptics had significantly prolonged P300 mean latency compared to those without detectable brain lesion(s) on MR scan. Moreover, these latter patients were compared on the basis of epilepsy duration, type of seizure, seizure frequency and antiepileptic treatment; the application of a multiple regression model showed a significant relationship between P300 latency prolongation and epilepsy duration, seizure frequency and polytherapy.

Adolescent↗

PubMed2000

Contralateral neglect induced by right posterior parietal rTMS in healthy subjects.

We applied repetitive transcranial magnetic stimulation (rTMS) in order to induce interference on visuo-spatial perception in 11 healthy subjects. Subjects performed a visuo-spatial task requiring judgements about the symmetry of prebisected lines. Visual stimuli consisted of symmetrically or asymmetrically transected lines, tachystoscopically presented for 50 ms on a computer-monitor. Performance was examined in basal condition and during rTMS trains of 10 stimuli at 25 Hz, delivered through a focal coil over right or left posterior parietal cortex (P5 and P6 sites) and triggered synchronously with visual stimulus. Randomly intermixed sham rTMS trains were employed to control for non-specific effects. Right parietal rTMS induced a significant rightward bias in symmetry judgements as compared with basal and sham rTMS conditions. No differences emerged between other conditions.

Adult↗

PubMed2000

Magnetic stimulation study during observation of motor tasks.

The aim of the study was to assess if the observation of single or more complex muscle movements activates the premotor cortex in man. We stimulated by transcranial magnetic stimulation the right and left motor cortex recording from the abductor pollicis brevis of eight normal subjects, during observation of different movements performed by the examiner: (1) single movements: thumb abduction, arm elevation; (2) motor sequences: finger opposing movements performed in an ordinate sequence: 1-2, 1-3, 1-4, 1-5, 1-2ellipsis, and in a non-consecutive non-repetitive order: 1-3, 1-5, 1-4, 1-2, 1-5, 1-2ellipsis We found an increased excitability of the right cortex during observation of isolated muscle movement regardless of which muscle is moved. At the stimulation of the left cortex, MEPs were significantly increased during observation of complex muscular synergies.

Adult↗

PubMed1999

Reorganization of cortical motor area in prior polio patients.

OBJECTIVE: Focal transcranial magnetic stimulation (TMS) was used to study the motor maps of upper limb muscles in 7 adult patients with a history of paralytic poliomyelitis. The aim of the study was to verify the potential for long-term cortical reorganization of a selective peripheral motor neuron lesion suffered early in life. METHODS: Patient selection was based on the prevalent involvement of proximal muscles in only one of the upper limbs. Motor evoked potentials (MEPs) were recorded from deltoid and abductor pollicis brevis (APB) muscles. Each muscle map was characterized by area (no. of excitable positions), volume (the sum of MEP amplitudes at all scalp positions), maximal amplitude (the highest MEP recorded). RESULTS: In the patients, the mean area, volume and maximal amplitude were significantly greater in affected vs. contralateral deltoid (P<0.05) and vs. controls (P<0.01). No significant differences were found in APB map parameters. The APB/deltoid ratio for area was lower in the affected compared with the unaffected side and controls (P = 0.06). Cortical reorganization was not significantly correlated with motor performance. CONCLUSION: These findings are consistent with a rearrangement in human motor pathways targeting muscles affected by a lower motor neuron lesion.

Adult↗

PubMed1999

Multievoked potentials in type I diabetic patients: one year follow-up study.

A neurophysiological (SEP, VEP) follow-up study was carried out in 30 diabetic patients with type I diabetes mellitus of ten or more years duration. This in order to investigate whether one year of improved glucoregulation may influence the progression of central damage. In our series, patients showed a significant decrement of HbA1C levels (p < 0.05) in the one-year follow-up. In the same period the frequency of SEP and VEP abnormalities varied from 10/30 (33%) to 16/30 (53%) and from 8/30 (26%) to 5/30 (16%) respectively. This finding would suggest that prevailing glycaemic control would be a major determinant for the outcome of VEP measurements. SEP alterations, in contrast, tend to progress in a 12 months period despite a considerable improvement in glycaemic control. However, by dividing patients in two groups according mean one year HbA1C less than 8% and more than 8%, the latter group only showed a significant increasing of absolute latencies of each median and tibial SEP components. Our results suggest that VEP abnormalities are still reversible in diabetic patients with improved metabolic control. The acquired abnormalities of somatosensory pathways persist longer, but a strict glycaemic control may influence and retard the progression of central conduction involvement.

Adolescent↗

PubMed1998

Neurophysiological and radiological findings in myotonic dystrophy patients.

Somatosensory evoked potentials (SEPs) and brainstem auditory evoked potentials (BAEPs) were recorded in 10 patients with myotonic dystrophy and in 20 sex and age-matched healthy controls. In all patients a brain MRI examination was also performed. In our results, the significantly longer absolute peak latencies of the SEPs and the abnormal increasing of the later components of the BAEPs suggest an involvement of the afferent sensory and central auditory pathways. Brain MRI showed white matter hyperintense lesions (WMHL) in eight patients (80%). No correlations were found between individual abnormal electrophysiological parameters or severity of WMHL and age, age at onset, disease duration or muscular impairment. The total number (SEP + BAEP) of electrophysiological abnormalities significantly correlated with muscular impairment (p < 0.05) and MRI changes (p < 0.005), suggesting a strict pathogenetic linkage between muscular and nervous system alterations in this disease.

Journal Article↗

PubMed1997

Magnetic stimulation study in patients with myotonic dystrophy.

To further define motor nervous system alterations in myotonic dystrophy (MD), motor potentials to transcranial and cervical magnetic stimulation (MEPs) were recorded from the right abductor pollicis brevis muscle in 10 patients with MD and in 10 healthy controls. Cortical and cervical latencies, central motor conduction time (CMCT), stimulus threshold intensity and cortical MEP amplitudes expressed both as absolute values and as %M were analysed. MEP cervical latency, absolute or relative amplitude and excitability threshold did not significantly differ in patients and controls. The mean cortical motor latency and CMCT were significantly prolonged in MD patients with respect to normal subjects. Moreover, CMCTs were found to be significantly related to stimulus threshold intensity (P = 0.03) and only marginally related to absolute cortical amplitude (P = 0.06). These findings are indicative of a central motor delay, also related to decreased excitability of motor neurons, in patients with MD. No correlations were found between individual neurophysiological parameters and age, duration of disease and clinical impairment. Our results suggest that magnetic stimulation studies can detect subclinical dysfunctions of the central motor system in MD patients, as one of the multisystemic manifestations of the disease, rather independent of the primitive muscle damage.

Adolescent↗

PubMed1997

Evoked potential study in facio-scapulo-humeral muscular dystrophy.

Nerve conduction velocities (NCVs), somatosensory (SEPs) and auditory evoked potentials (BAEPs) were recorded in 9 patients with facio-scapulo-humeral dystrophy (FSHD) and in 20 age-matched controls. In FSHD patients a significant increase of the nerve distal sensory latencies and of the absolute SEP latencies revealed a subclinical involvement of the afferent sensory pathways, as well as the abnormal slowing of the later components of the BAEPs, pointed to a central auditory dysfunction. Moreover all patients underwent brain MRI that showed the presence of white matter hyperintense lesions in 4 of them (44%). No correlations were found between individual or total number of SEP and BAEP abnormal electrophysiological parameters and severity of WMHL, age, age at onset, duration of the disease or muscular impairment. These findings make the interpretation and pathophysiology of the nervous damage in FSHD rather uncertain. More studies are required to better define the aspects of neurogenic involvement in this type of muscular dystrophy.

Adult↗

PubMed1996

Somatosensory and visual evoked potentials study in young insulin-dependent diabetic patients.

To evaluate central nervous system involvement in diabetes, somatosensory (SEPs) and visual (VEPs) evoked potentials were investigated in a group of 35 patients and 20 sex, age-matched controls. In order to avoid methodological biases due to different type and duration of disease, we studied an omogeneous group of young insulin-dependent diabetics with ten or more year duration of disease. In our results VEP and SEP parameters were found abnormal in 10 (28%) patients, all of whom presenting clear signs of peripheral neuropathy. In diabetic patients median and tibial SEPs showed significant increase in absolute latency mean values of several components except interpeak intervals, as well as mean P 100 latencies were significantly increased in both eyes at 15' check size stimulation pattern. VEP and SEP components were not generally significantly associated with the indices of peripheral function. In contrast, in diabetics significant correlations were found between P 100 latencies and median SEP parameters including interpeak intervals. No major associations related VEP and SEP latencies to duration of diabetes and prevailing glycaemic control. In conclusion the central nervous system involvement in young insulin-dependent diabetics, even though diffusely present, seems unequivocally concomitant to peripheral conduction impairment.

Adolescent↗

PubMed1994

Basal ganglia calcifications and ALS syndrome.

We report the case of a patient with idiopathic hypoparathyroidism and unusually large symmetrical calcifications in the basal ganglia, thalami, cerebellar hemispheres and brainstem, who clinically presented an ALS-like syndrome. We discuss the possible role of abnormal calcium metabolism in the pathogenesis of motoneuron disease.

Amyotrophic Lateral Sclerosis↗