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C Toro

Publications and source records attributed to C Toro.

At least 37 records · Page 2Linked to original sources
PubMed1994

Symptomatic and essential palatal tremor. 2. Differences of palatal movements.

Palatal tremor, a rhythmic movement disorder of the soft palate, may be described as two separate entities: symptomatic palatal tremor (SPT) and essential palatal tremor (EPT). The symptomatic form is associated with brain stem or cerebellar disease, whereas the essential form has no known etiology. A cardinal symptom of EPT is the presence of ear clicks, which do not occur in SPT. Visual observation of the movements in the two disorders suggests that the difference in symptoms is due to the activation of different palatal muscles, the levator veli palatini in SPT and the tensor veli palatini in EPT. Electromyographic recording from the levator veli palatini muscle showed abnormal bursting activity time locked to the palatal movements in patients with SPT, but not in those with EPT. Because the two palatal muscles are innervated by different cranial nerves, SPT and EPT are likely to have separate origins.

Adult↗
PubMed1994

Resetting of essential tremor and postural tremor in Parkinson's disease with transcranial magnetic stimulation.

We studied the effects of transcranial motor cortex stimulation on the electromyographic characteristics of tremor in 9 patients with familial essential tremor and in 12 patients with postural tremor associated with Parkinson's disease. Transcranial magnetic stimulation reset both types of tremor equally. The resetting depended on the stimulus intensity, but was most closely correlated with the duration of the electromyographic silent period that followed the stimulus-induced motor evoked potential. Tremor resetting was present bilaterally even after focal, unilateral stimulation. Transcranial electrical stimulation failed to reset the tremor in either patient group. These results emphasize the role of central, intracortical structures in the generation of essential tremor and postural tremor in Parkinson's disease.

Adult↗
PubMed1994

Cortical magnetic and electric fields associated with voluntary finger movements.

Multichannel recordings of both movement-related magnetic fields (MRMFs) and movement-related cortical potentials (MRCPs) were simultaneously recorded in association with voluntary unilateral self-paced index finger abduction movement in two normal volunteers. 1) Slow magnetic field (readiness field; RF) can be detected several hundred msec before the movement onset, and its field distribution indicates the existence of the largest generator source over the contralateral primary motor area. Taken together with the vertex-maximal Bereitschaftspotential which corresponds to the earlier part of the RF, the complexity of this magnetic field suggested by relatively low correlation value in single dipole model indicates the co-activation of other underlying generators besides this largest dipole. 2) The utilization of MRMF with MRCP facilitates the separation of two distinct electrophysiological events in proximity to the movement onset, which are difficult to be determined by the technique of MRCP only. Those are the motor field (MF) and the movement evoked field I (MEFI) in MRMF, and the parietal peak motor potential (ppMP) and the frontal peak motor potential (fpMP) in MRCP, which occur approximately 20 and 100 msec after EMG onset, respectively. These two subcomponents may imply the culmination of motor cortex and sensory feedback activation, respectively. Combined study of MRMF and MRCP will provide better definition of cortical events related to voluntary movement than the study of either modality alone.

Adult↗
PubMed1994

Head surface digitization and registration: a method for mapping positions on the head onto magnetic resonance images.

We have developed a method for mapping positions on the head, such as anatomical landmarks, electrode locations, and stimulation sites, onto magnetic resonance (MR) images of the head. This method is based on the registration of two representations of the head surface: a series of contours obtained from MR images and a set of points measured from the head. The three-dimensional coordinates of each head point were acquired with the use of a magnetic digitizer, whose source was removed from the equipment and mounted on top of the subject's head. This arrangement seemed less uncomfortable for the subject than head immobilization and allowed the acquisition of many points without compromising the precision of the measurements. The digitized head surface was registered to MR image head contours using a surface registration algorithm. The registration provided the rotation and translation parameters needed for mapping head positions onto MR images. The precision of this mapping method has been estimated to be in the range of 3 to 8 mm. This method has been used to map dipole sources in electroencephalography and magneto-encephalography and to impose maps of scalp sites used in transcranial magnetic stimulation onto MR and PET images of the brain.

Adult↗
PubMed1994

Event-related desynchronization and movement-related cortical potentials on the ECoG and EEG.

Event-related desynchronization (ERD) 2.0 sec before and 1.0 sec after movement in the frequency bands of 8-10, 10-12, 12-20 and 20-30 Hz and movement-related cortical potentials (MRCPs) to self-paced movements were studied from subdural recordings over the central region in 3 patients, and from scalp-recorded EEGs in 20 normal volunteers. In direct cortical recordings, the peak ERD response and peak MRCP amplitude to self-paced finger movements were maximal over recording sites in the contralateral hand motor representations. The topography and time of onset of the ERD response to finger and foot movements suggest that the ERD responses in the 8-10 Hz and 10-12 Hz bands are more somatotopically restricted than the responses in the higher frequency bands. The power recovery and subsequent overshoot in the different frequency bands occurred in an orderly fashion with the faster frequencies recovering earlier. The ERD responses on the scalp-recorded EEGs were of lower magnitude and more widely distributed than those occurring on the subdural recordings. Across the population, there was no relation between the magnitude of the ERD response in any of the frequency bands studied and the peak amplitude of the negative slope (pNS') and the frontal peak of the motor potential (fpMP) of the MRCPs. MRCPs and ERD responses originate in similar cortical regions and share some common timing features, but the magnitude and spatial distribution of the two responses appear to be independent of each other, which suggests that the physiological mechanisms governing these two events are different and may represent different aspects of motor cortex activation. Differences in the timing and topographical features of the ERD responses in the various frequency bands also suggest a distinct functional significance for the various spectral components of the electrical activity in the motor cortex.

Adult↗
PubMed1994

8-12 Hz rhythmic oscillations in human motor cortex during two-dimensional arm movements: evidence for representation of kinematic parameters.

Direct cortical recordings were taken from 12 patients with implanted subdural electrode arrays during performance of a 2-dimensional, multi-joint, visually guided arm movement task. Task-related changes in the amplitude of the motor cortex 8-12 Hz surface local field oscillations were evaluated for the encoding of direction and amplitude of movement in the 6 patients in whom no epileptogenic or ECoG background abnormalities were detected over the motor-sensory cortical areas under the recording electrode array. The topography, time of onset and duration of these responses were evaluated in the context of motor cortex somatotopy, as defined by cortical stimulation delivered through the electrode array. Multi-joint arm movements were accompanied by a decrease in the power of the 8-12 Hz frequency components of the ECoG signal. These power changes were spatially distributed over the upper extremity, motor-sensory representation. Movement amplitude influenced the magnitude, duration, and extent of the spatial distribution of ECoG power changes in the 8-12 Hz band. These effects occurred predominantly over cortical areas corresponding to the upper extremity motor-sensory representations. Direction of movement had a weaker influence on the 8-12 Hz frequency components of the ECoG over the upper extremity motor-sensory representations, but influenced the patterns of 8-12 Hz ECoG response on adjacent cortical regions. These results show that the amplitude of surface electrical oscillations generated over the rolandic cortex are correlated with the kinematics of multi-joint arm movements. These changes in the ECoG signal appear to reflect shifts in the functional state of neuronal ensembles involved in the initiation and execution of motor tasks.

Adult↗
PubMed1994

Stiff-man syndrome.

Explore the source record for details and available documents.

Combined Modality Therapy↗
PubMed1994

Symptomatic and essential palatal tremor. 1. Clinical, physiological and MRI analysis.

Palatal tremor (brief, rhythmic involuntary movements of the soft palate) apparently comprises two different nosological entities: essential palatal tremor (EPT) and symptomatic palatal tremor (SPT). The site of the abnormality in EPT is unknown, whereas SPT is believed to arise from a lesion of the brainstem or cerebellum (within the Guillain-Mollaret triangle). The clinical and physiological properties of these conditions were studied in four patients with EPT and six patients with SPT. Patients with EPT had normal cerebellar function, but those with SPT had clinical signs of cerebellar dysfunction. The palatal movements were consistent with activation of the tensor veli palatini muscle in EPT and of the levator veli palatini muscle in SPT. During sleep, EPT stopped, whereas SPT continued with only slight variations in the tremor rate. The cycle of palatal tremor could not be reset by stimulation of trigeminal afferents in either EPT or SPT patients, and Valsalva's manoeuvre did not consistently affect the rhythm of the tremor in either group. The palatal tremor cycle exerted remote effects on the tonic electromyographic activity of the upper and lower extremities only in patients with SPT. These effects were present only on the side of the cerebellar signs (opposite the side with the enlarged inferior olive) in patients with a unilateral syndrome. Essential palatal tremor patients had only polysynaptic brainstem reflex abnormalities, whereas SPT patients had abnormalities of monosynaptic, oligosynaptic and polysynaptic brainstem reflexes. Magnetic resonance imaging showed no evidence of structural abnormalities in EPT patients, but SPT patients had a hyperdense signal of the ventral upper medulla (the region of the inferior olive) on T2-weighted images. These observations support the hypothesis that EPT and SPT are two different diseases. In SPT, cerebellar dysfunction ipsilateral to the palatal tremor may be due, in part, to abnormal function of the contralateral hypertrophic inferior olive. The proposed basis of SPT is a disturbance of electrotonic coupling between the cells of the inferior olive induced by a lesion of the dentato-olivary pathway. Similar mechanisms could be responsible for postural tremors in general. The pathophysiological basis of EPT remains unknown.

Adult↗
PubMed1993

Source analysis of scalp-recorded movement-related electrical potentials.

We used brain electric source analysis to study the sources generating the movement-related cortical potentials during the interval from 200 msec before to 200 msec after the movement onset. Dipole solutions were obtained for the peak of the negative slope (pNS') and the frontal peak of the motor potential (fpMP) on scalp-recorded movement-related electrical potentials elicited by self-paced, repetitive unilateral finger movements in 10 normal volunteers. Two sources in homologous areas on each side of a spherical head model provided a satisfactory solution for the activity occurring at the instant of the pNS' in all subjects. The fpMP was modeled by a contralateral source and a midline source in 6 subjects and by a single contralateral source in the remaining 4 subjects. The percentage of the residual variance, or goodness-of-fit, over the interval from -200 to 200 msec, using the derived at pNS' and fpMP, was low. The results support the hypothesis that the NS' originates from the activity of bilateral generators in the sensorimotor cortex, and the motor potential arises from the combined activity of sources in the contralateral postcentral regions and the supplementary motor area.

Adult↗
PubMed1993

Topography of the inhibitory and excitatory responses to transcranial magnetic stimulation in a hand muscle.

We studied the excitatory motor evoked potentials (MEPs) and the inhibitory (silent period) responses to focal transcranial magnetic stimulation (TMS) in the abductor pollicis brevis (APB) of 5 normal subjects to learn whether the scalp topography of the two responses differed. At the scalp location where stimulation produced the highest-amplitude MEP in the voluntarily activated APB, stimulus intensities below the MEP threshold produced silent periods with little or no preceding facilitation. The silent periods had a mean duration of 26.8 +/- 6.8 msec and a mean onset latency of 27.6 +/- 3.6 msec, which was 7.2 +/- 2.3 msec longer than the latency of MEPs produced in the APB by higher stimulus intensities. A period of excitation, with an onset latency of 50-80 msec, often followed the silent period. On averaged trials, a stimulus intensity just above the threshold of the MEP at its optimal position produced MEPs followed by silent periods at a cluster of scalp locations 1 cm apart on the central scalp (medial area) and silent periods with very slight or no preceding facilitation in 3-9 locations lateral to the MEP area (lateral area). This finding was confirmed in 3 subjects with maps constructed from statistical analysis of multiple trials. These maps also showed that MEPs produced from the medial area occurred 4-6 msec earlier than those produced from the lateral area. The integral of the silent period tended to be larger in the lateral area. The motor representation of APB, as defined by TMS, is not homogeneous but rather contains at least two components that differ physiologically and topographically.

Adult↗
PubMed1993

Cortical tremor. A common manifestation of cortical myoclonus.

Ten patients, three with postural tremor and seven with action myoclonus, had stereotyped involuntary rhythmic movements when attempting to execute a sustained isometric muscle contraction. The movements were characterized by rhythmic EMG bursts lasting less than 50 msec and appearing synchronously in agonist and antagonist muscles at a rate of 9 to 18 Hz. Backaveraging of the EEG activity related to the onset of the rhythmic EMG bursts identified a cortical potential preceding the EMG bursts in all patients. These symptoms and signs fit the description of "cortical tremor," a variant of cortical reflex myoclonus. Cortical tremor is common in patients with cortical myoclonus and may be a source of functional disability. In two patients in whom we studied the effects of graded levels of isometric force, force recruitment modulated the abnormal EMG bursting frequency, amplitude, and spatial distribution of the myoclonic jerks in the activated limb. Transcranial magnetic and electrical stimulation, but not peripheral nerve stimulation, influenced the abnormal EMG bursting pattern, implying a greater dependence of this rhythmic phenomenon on a central generator than on peripheral feedback loops.

Adolescent↗
PubMed1992

Longitudinal neurophysiologic studies in a patient with metachromatic leukodystrophy following bone marrow transplantation.

We describe a girl with late infantile metachromatic leukodystrophy. The patient has been followed up with serial neurologic and neurophysiologic examinations for 8 years following bone marrow transplantation, which she underwent when she was 4 3/4 years old. Her older sister died from metachromatic leukodystrophy at the age of 8 years, whereas our patient has retained significant cognitive and motor skills. Serial neurophysiologic studies initially demonstrated continued deterioration after the bone marrow transplantation, but since then, most results have remained stable or improved. Although, to our knowledge, there have been no previous serial studies of metachromatic leukodystrophy, individual case studies suggest that these findings in our patient are very unusual. With the advent of possible treatment for this condition, there is a need for further serial neurophysiologic studies to characterize the natural progression and the possible detection of progression or reversal with treatment.

Action Potentials↗
PubMed1987

Emergency carotid artery thrombectomy for postpartum hemiplegia.

The case of a 22-year-old patient who suffered from postpartum hemiplegia due to thrombosis of the internal carotid artery is reported. She was treated aggressively with pentobarbital coma, angiography, and thrombectomy and recovered with minimal deficit.

Adult↗
PubMed1986

Electrophysiological correlates of a paroxysmal movement disorder.

Averaged electroencephalographic activity related to rhythmic jerking movements was recorded in a patient with a complex neurological symptomatology. The diagnosis of a functional disorder was strongly suggested by his clinical course, inconsistent findings from physical examination, and negative workup. His abnormal movements were associated with the same electrophysiological correlates as normal willed motion, suggesting that averaged movement potentials may provide useful information in the study of patients with suspected functional movement disorders.

Adult↗
PubMed1980

Effectiveness of urine surveillance as an adjunct to outpatient psychotherapy for drug abusers.

Twenty-nine polydrug abusers were randomly assigned to three out-patient treatment groups after inpatient detoxification. The groups were outpatient psychotherapy (1) with urine surveillance, (2) without surveillance, and (3) waiting list control. Tests were administered before and 3 months after outpatient treatment began. All groups made positive changes during treatment including significant reduction in drugs abused and numbers of subjects reporting less time spent in illegal activity. Notable significant differences were Group 3's reduction in social introversion vs Groups 1 and 2, and Group 1's retaining fewer drug-using friends and showing greatest reduction in barbiturate use frequency vs Groups 2 and 3. Experimenters concluded urine surveillance was somewhat helpful as an adjunct to outpatient psychotherapy but suggested its effect could be amplified by employing more rigorous surveillance procedures, especially if contingency contracting were utilized.

Adolescent↗