RESUMO
Previous data indicate that in healthy subjects, there is a connectivity between cortical areas for hand movement and language on the left hemisphere. This link is possibly mediated by the so-called mirror neuron system. The present study investigated the functional relationship between linguistic and hand movement processing in patients who were recovering from post-stroke aphasia. The excitability of the right- and left-hand motor cortex during language production in patients who were recovering from post-stroke aphasia and age-matched controls was investigated. As control, phonation was investigated. Hand motor cortex excitability was assessed with Motor Evoked Potentials which were elicited by Transcranial Magnetic Stimulation (TMS). In patients, reading aloud enhanced the excitability of the right hemispheric hand motor cortex, whereas phonation had no effect on hand motor cortex excitability. In the control group, an increased excitability of the left hemispheric hand motor system was found during reading aloud in accordance with previous data. The present data suggest a functional connectivity between regions mediating hand movements and reading. This may indicate that the right hemisphere participates in language processing as far as involved in single word reading in patients recovering from aphasia. The coactivation between cerebral representations of hand movements and language may be used therapeutically for aphasia rehabilitation.
Assuntos
Afasia/fisiopatologia , Mãos/inervação , Idioma , Córtex Motor/fisiopatologia , Desempenho Psicomotor/fisiologia , Recuperação de Função Fisiológica/fisiologia , Adulto , Análise de Variância , Afasia/patologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estimulação Magnética Transcraniana/métodosRESUMO
We report on a patient who suffered sudden diplopia after heart surgery. Computed tomography of the orbita revealed a subperiosteal hemorrhage as the underlying cause. We discuss possible mechanisms that may have led to the bleeding as well as therapeutic options.
Assuntos
Procedimentos Cirúrgicos Cardíacos/efeitos adversos , Diplopia/etiologia , Exoftalmia/etiologia , Doenças Orbitárias/etiologia , Hemorragia Pós-Operatória , Anticoagulantes/uso terapêutico , Seguimentos , Humanos , Pressão Intraocular , Masculino , Pessoa de Meia-Idade , Doenças Orbitárias/diagnóstico por imagem , Doenças Orbitárias/tratamento farmacológico , Hemorragia Pós-Operatória/tratamento farmacológico , Fatores de Tempo , Tomografia Computadorizada por Raios XRESUMO
Reading of musical notes and playing piano is a very complex motor task which requires years of practice. In addition to motor skills, rapid and effective visuomotor transformation as well as processing of the different components of music like pitch, rhythm and musical texture are involved. The aim of the present study was the investigation of the cortical network which mediates music performance compared to music imagery in 12 music academy students playing the right hand part of a Bartok piece using functional magnetic resonance imaging (fMRI). In both conditions, fMRI activations of a bilateral frontoparietal network comprising the premotor areas, the precuneus and the medial part of Brodmann Area 40 were found. During music performance but not during imagery the contralateral primary motor cortex and posterior parietal cortex (PPC) bilaterally was active. This reflects the role of primary motor cortex for motor execution but not imagery and the higher visuomotor integration requirements during music performance compared to simulation. The notion that the same areas are involved in visuomotor transformation/motor planning and music processing emphasizes the multimodal properties of cortical areas involved in music and motor imagery in musicians.
Assuntos
Encéfalo/fisiologia , Imaginação/fisiologia , Imageamento por Ressonância Magnética/métodos , Música , Desempenho Psicomotor/fisiologia , Adulto , Feminino , Humanos , Masculino , Rede Nervosa/fisiologiaRESUMO
Fusobacterium necrophorum, an anaerobic, gram-negative rod, belongs to the physiological flora of the oropharynx. It causes Lemierre's syndrome characterized by oropharyngeal infection, septic thrombophlebitis of the neck, in particular of the internal jugular vein, and metastatic abscesses, predominantly in the lungs. Rarely, and mainly in children, it causes meningitis. Here we report the clinical course of a 25-year-old woman with F. necrophorum meningitis. She presented with incomplete, right third nerve palsy. Within a few days, she developed fever, meningism and progressive reduction of vigilance. Cerebrospinal fluid analysis showed typical signs of bacterial meningitis. After the identification of F. necrophorum, the antibiotic treatment was changed to meropenem, which led to continuous improvement of the clinical symptoms. Due to persistent signs of inflammation in the CSF, metronidazole was added to the antibiotic regime. This case report demonstrates that F. necrophorum should always be considered in the diagnostic workup of bacterial meningitis in adults.
Assuntos
Fusobacterium necrophorum , Meningites Bacterianas/diagnóstico , Otite Média/diagnóstico , Faringite/diagnóstico , Sepse/diagnóstico , Adulto , Antibacterianos , Glicemia/metabolismo , Proteínas do Líquido Cefalorraquidiano/líquido cefalorraquidiano , Diagnóstico Diferencial , Quimioterapia Combinada/uso terapêutico , Feminino , Humanos , Ácido Láctico/líquido cefalorraquidiano , Contagem de Leucócitos , Abscesso Pulmonar/líquido cefalorraquidiano , Abscesso Pulmonar/diagnóstico , Abscesso Pulmonar/tratamento farmacológico , Meningites Bacterianas/líquido cefalorraquidiano , Meningites Bacterianas/tratamento farmacológico , Meropeném , Metronidazol/uso terapêutico , Doenças do Nervo Oculomotor/líquido cefalorraquidiano , Doenças do Nervo Oculomotor/diagnóstico , Doenças do Nervo Oculomotor/tratamento farmacológico , Otite Média/líquido cefalorraquidiano , Otite Média/tratamento farmacológico , Faringite/líquido cefalorraquidiano , Faringite/tratamento farmacológico , Sepse/líquido cefalorraquidiano , Sepse/tratamento farmacológico , Síndrome , Tienamicinas/uso terapêuticoRESUMO
We report on an 82-year-old woman who suffered a sudden loss of consciousness, right-sided hemiparesis, and aphasia during a coronary angiographic procedure. Computed tomography (CT) of the brain performed immediately revealed an edema and extravascularly localized contrast media in the left hemisphere. Within 6 h, neurological symptoms had disappeared, and a second CT after 48 h revealed normal results. Usually, extravasation of contrast media affects the posterior circulation with cortical blindness. This case demonstrates that contrast media may affect the blood-brain barrier also outside the posterior circulation. If neurological symptoms occur during angiography, contrast media extravasation must be distinguished from embolism or vasospasm induced by the angiographic procedure.
Assuntos
Barreira Hematoencefálica/efeitos dos fármacos , Edema Encefálico/induzido quimicamente , Meios de Contraste/efeitos adversos , Angiografia Coronária/efeitos adversos , Extravasamento de Materiais Terapêuticos e Diagnósticos/diagnóstico por imagem , Iohexol/análogos & derivados , Iohexol/efeitos adversos , Idoso , Idoso de 80 Anos ou mais , Afasia/induzido quimicamente , Afasia/diagnóstico por imagem , Edema Encefálico/diagnóstico por imagem , Meios de Contraste/farmacocinética , Dominância Cerebral/efeitos dos fármacos , Feminino , Hemiplegia/induzido quimicamente , Hemiplegia/diagnóstico por imagem , Humanos , Iohexol/farmacocinética , Taxa de Depuração Metabólica/fisiologia , Exame Neurológico/efeitos dos fármacos , Tomografia Computadorizada por Raios XRESUMO
The clinical and magnetic resonance (MR) features of hypertrophic olivary degeneration are described, along with a rare but treatable cause of this entity-pontine cavernous haemangioma. Hypertrophic olivary degeneration occurs after focal lesions to the dentato-rubro-olivary pathway, typically following a pontine haemorrhage involving the ipsilateral central tegmental tract, the contralateral superior cerebellar peduncle, or the dentate nucleus. Clinically, there is palatal myoclonus and an uncontrollable tremor, presumably caused by loss of inhibitory control. On MR imaging, hypertrophic olivary degeneration is characterised by a non-enhancing T1 isointense, T2 hyperintense enlargement confined to the olivary nucleus. Typically, haemorrhages following a hypertensive crisis are responsible for hypertrophic olivary degeneration. However, in the three reported cases, imaging findings within the former bleeding cavity suggested a cavernous haemangioma as the source of the haemorrhage.
Assuntos
Hemorragia Cerebral/etiologia , Hemorragia Cerebral/patologia , Hemangioma Cavernoso do Sistema Nervoso Central/complicações , Hemangioma Cavernoso do Sistema Nervoso Central/patologia , Hipertensão/complicações , Hipertensão/diagnóstico , Degeneração Neural/patologia , Núcleo Olivar/patologia , Ponte/patologia , Diagnóstico Diferencial , Seguimentos , Humanos , Hipertrofia/etiologia , Hipertrofia/patologia , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Fatores de TempoRESUMO
OBJECTIVES: Although functional MRI is widely used for preoperative planning and intraoperative neuronavigation, its accuracy to depict the site of neuronal activity is not exactly known. Experience with methods that may validate fMRI data and the results obtained when coregistering fMRI with different preoperative and intraoperative mapping modalities including metabolically based (18)F-fluorodeoxyglucose PET, electrophysiologcally based transcranial magnetic stimulation (TMS), and direct electrical cortical stimulation (DECS) are described. METHODS: Fifty patients were included. PET was performed in 30, TMS in 10, and DECS in 41 patients. After coregistration using a frameless stereotactic system, results were grouped into overlapping (<1 cm distance), neighbouring (<2 cm), or contradictory (>2 cm). RESULTS: Comparing fMRI with PET, 18 overlapping, seven neighbouring, and one contradictory result were obtained. In four patients no comparison was possible (because of motion artefacts, low signal to noise ratio, and unusual high tumour metabolism in PET). The comparison of TMS and fMRI showed seven overlapping and three neighbouring results. In three patients no DECS results could be obtained. Of the remaining 38 patients, fMRI hand motor tasks were compared with DECS results of the upper limb muscles in 36 patients, and fMRI foot motor tasks were compared with DECS results of the lower limb on 13 occasions. Of those 49 studies, overlapping results were obtained in 31 patients, and neighbouring in 14. On four occasions fMRI did not show functional information (because of motion artefacts and low signal to noise). CONCLUSIONS: All validation techniques have intrinsic limitations that restrict their spatial resolution. However, of 50 investigated patients, there was only one in whom results contradictory to fMRI were obtained. Although it is not thought that fMRI can replace the intraoperatively updated functional information (DECS), it is concluded that fMRI is an important adjunct in the preoperative assessment of patients with tumours in the vicinity of the central region.
Assuntos
Mapeamento Encefálico/métodos , Neoplasias Encefálicas/diagnóstico , Eletrodiagnóstico/métodos , Eletrodiagnóstico/normas , Eletrofisiologia/métodos , Eletrofisiologia/normas , Fluordesoxiglucose F18 , Imageamento por Ressonância Magnética/métodos , Imageamento por Ressonância Magnética/normas , Magnetismo , Compostos Radiofarmacêuticos , Tomografia Computadorizada de Emissão/métodos , Tomografia Computadorizada de Emissão/normas , Adulto , Idoso , Artefatos , Viés , Mapeamento Encefálico/instrumentação , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/fisiopatologia , Neoplasias Encefálicas/cirurgia , Eletrodiagnóstico/instrumentação , Eletrofisiologia/instrumentação , Feminino , Humanos , Imageamento por Ressonância Magnética/instrumentação , Magnetismo/instrumentação , Masculino , Pessoa de Meia-Idade , Cuidados Pré-Operatórios , Desempenho Psicomotor , Sensibilidade e Especificidade , Processamento de Sinais Assistido por Computador , Técnicas Estereotáxicas/instrumentação , Técnicas Estereotáxicas/normas , Tomografia Computadorizada de Emissão/instrumentaçãoRESUMO
In previous studies it has been shown that picture-naming latencies can be facilitated with both suprathreshold single and repetitive transcranial magnetic stimulation (TMS/rTMS) over Wernicke's area. The aim of this study was to investigate whether low-frequency rTMS (1 Hz) or high-frequency rTMS (20 Hz) at subthreshold intensities is also capable of influencing picture naming. In 16 healthy right-hand male subjects, trains of 1 Hz or 20 Hz were applied over either Wernicke's area, Broca's area, or the primary visual cortex. The subjects had to name 20 black-and-white line drawings, which were shown immediately after rTMS and again 2 minutes later. Naming latency could be facilitated only immediately after Wernicke's area stimulation at a frequency of 20 Hz and at an intensity of 55% of the maximal stimulator output, which was more than the motor threshold. All other stimulation procedures failed to influence naming latencies. These results indicate that language functions can be facilitated in healthy subjects only by high-frequency rTMS with intensities at or above the motor threshold.
Assuntos
Encéfalo/fisiologia , Idioma , Adulto , Limiar Diferencial , Estimulação Elétrica/métodos , Humanos , Masculino , Músculo Esquelético/fisiologia , Nomes , Tempo de Reação/fisiologia , Estimulação Magnética TranscranianaRESUMO
OBJECTIVE: Simple reaction time (RT) can be influenced by transcranial magnetic stimulation (TMS) to the motor cortex. Since TMS differentially affects RT of ipsilateral and contralateral muscles a combined RT and TMS investigation sheds light on cortical motor control of bimanual movements. METHODS: Ten normal subjects and one subject with congenital mirror movements (MM) were investigated with a RT paradigm in which they had to move one or both hands in response to a visual go-signal. Suprathreshold TMS was applied to the motor cortex ipsilateral or contralateral to the moving hand at various interstimulus intervals (ISIs) after presentation of the go-signal. EMG recordings from the thenar muscles of both hands were used to determine the RT. RESULTS: TMS applied to the ipsilateral motor cortex shortened RT when TMS was delivered simultaneously with the go-signal. With increasing ISI between TMS and go-signal the RT was progressively delayed. This delay was more pronounced if TMS was applied contralateral to the moving hand. When normal subjects performed bimanual movements the TMS-induced changes in RT were essentially the same as if they had used the hand in an unimanual task. In the subject with MM, TMS given at the time of the go-signal facilitated both the voluntary and the MM. With increasing ISI, however, RT for voluntary movements and MM increased in parallel. CONCLUSIONS: Ipsilateral TMS affects the timing of hand movements to the same extent regardless of whether the hand is engaged in an unimanual or a bimanual movement. It can be concluded, therefore, that in normal subjects simple bimanual movements are controlled by each motor cortex independently. The results obtained in the subject with MM are consistent with the hypothesis that mirror movements originate from uncrossed corticospinal fibres. The alternative hypothesis that a deficit in transcallosal inhibition leads to MM in the contralateral motor cortex is not compatible with the presented data, because TMS applied to the motor cortex ipsilateral to a voluntary moved hand affected voluntary movements and MM to the same extent.
Assuntos
Mãos/fisiologia , Córtex Motor/fisiologia , Movimento/fisiologia , Adulto , Eletromiografia , Humanos , Transtornos dos Movimentos/congênito , Transtornos dos Movimentos/fisiopatologia , Músculo Esquelético/fisiologia , Estimulação Física , Tempo de Reação/fisiologia , Valores de Referência , Polegar , Estimulação Magnética TranscranianaRESUMO
A major intrinsic limitation of transcranial magnetic stimulation (TMS) to map the human brain lies in the unclear relationship between the position of the stimulating coil on the scalp and the underlying stimulated cortex. The relationship between structure and function as the major feature constituting a brain mapping modality can therefore not be established. Recent advances in image processing allowed us to refine TMS by combining magnetic resonance imaging (MRI) modalities with TMS using a neuronavigation system to measure the position of the stimulating coil and map this position onto a MRI data set. This technique has several advantages over recent TMS mapping strategies. The position of the coil on the scalp can be held constant as verified by real time visual guidance. When evaluating higher cortical functions, the relationship between underlying cortical anatomy and the scalp stimulation site can be accurately assessed. Cortical motor output maps can be easily obtained for preoperative planning and decision making for mass lesions near rolandic cortex in patients. In conclusion, navigated TMS is a reliable alternative for localizing cortical functions and therefore may be a useful adjunct or in selected patients even a helpful alternative to other functional neuroimaging methods.
Assuntos
Encefalopatias/patologia , Encefalopatias/fisiopatologia , Mapeamento Encefálico/métodos , Encéfalo/patologia , Encéfalo/fisiopatologia , Estimulação Elétrica , Humanos , Imageamento por Ressonância Magnética , Terapia Assistida por Computador/métodosRESUMO
This manuscript reviews the current stance and the pertinent problems of transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) as brain mapping methodologies. The missing structure-function relation limits the use of TMS, whereas the uncertainty about the functional significance of activated cortical regions might render interpretation of fMRI studies difficult. Advances in image processing, however, allowed for 3- dimensional real-time visual guidance of TMS and integration with fMRI data. We describe the method used to coregister TMS and fMRI and present examples where a multimodality neuroimaging approach might add to our understanding of normal and pathological brain function.
Assuntos
Mapeamento Encefálico/métodos , Neoplasias Encefálicas/diagnóstico , Estimulação Elétrica/instrumentação , Campos Eletromagnéticos , Imageamento por Ressonância Magnética/métodos , Meningioma/diagnóstico , Mapeamento Encefálico/instrumentação , Humanos , Aumento da Imagem , Imageamento por Ressonância Magnética/instrumentação , MagnetismoRESUMO
PURPOSE: This paper describes the potential of navigated transcranial magnetic stimulation to map the motor cortex in patients with mass lesions near the primary motor cortex by comparing the results of this technique to those of functional MRI. MATERIAL AND METHODS: Ten patients with mass lesions near the central sulcus were studied preoperatively using a figure-of-eight transcranial magnetic stimulator attached to a neuronavigation system to allow for direct visualization of the stimulated brain region. Subsequently, in all patients a blood oxygenation level dependent 2D multislice multishot T2*-weighted gradient echo EPI sequence on a 1.5 T Philips Gyroscan during motor activation was performed. Results of both methods were coregistered and compared. RESULTS: The distances between the peak parenchymal fMRI activation and the cortical area where TMS elicited the maximum MEPs ranged between 0 and 1.2 cm (mean 0.6 cm, SD 0.4 cm). CONCLUSION: We conclude that navigated TMS is a reliable alternative for localizing the motor-related areas in the human brain preoperatively and therefore may be a useful adjunct or, in selected patients, even a helpful alternative to functional MRI.
Assuntos
Neoplasias Encefálicas/cirurgia , Imageamento por Ressonância Magnética/métodos , Córtex Motor/patologia , Estimulação Magnética Transcraniana , Adulto , Neoplasias Encefálicas/patologia , Estimulação Elétrica , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Córtex Motor/fisiologia , Oxigênio/sangue , Planejamento de Assistência ao Paciente , Valor Preditivo dos Testes , Cuidados Pré-OperatóriosRESUMO
We performed functional magnetic resonance imaging (MRI) in professional piano players and control subjects during an overtrained complex finger movement task using a blood oxygenation level dependent echo-planar gradient echo sequence. Activation clusters were seen in primary motor cortex, supplementary motor area, premotor cortex and superior parietal lobule. We found significant differences in the extent of cerebral activation between both groups with piano players having a smaller number of activated voxels. We conclude that, due to long-term motor practice a different cortical activation pattern can be visualized in piano players. For the same movements lesser neurons need to be recruited. The different volume of the activated ortical areas might therefore reflect the different effort necessary for motor performance in both groups.
Assuntos
Córtex Cerebral/fisiologia , Mãos/fisiologia , Imageamento por Ressonância Magnética , Atividade Motora/fisiologia , Destreza Motora/fisiologia , Música , Adulto , Circulação Cerebrovascular/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Córtex Motor/fisiologia , Plasticidade Neuronal/fisiologia , Oxigênio/sangue , Lobo Parietal/fisiologia , Valores de ReferênciaRESUMO
TMS mapping and fMRI were used to investigate changes in the motor cortex representation of the hand in a patient with complete loss of right hand function following traumatic avulsion of the cervical roots C7 and C8. Both TMS and fMRI demonstrated an expansion of the motor representation of the forearm into the hand area contralateral to the injured side. fMRI of the hand area, however, revealed that this area could still be activated when the patient was instructed to imagine finger tapping with his plegic hand. These results indicate that the plegic hand is still represented in the motor cortex, despite the fact that the same cortical area is also now active during movements involving forearm muscles.
Assuntos
Mãos/fisiologia , Córtex Motor/fisiopatologia , Paralisia/fisiopatologia , Idoso , Mapeamento Encefálico , Potencial Evocado Motor/fisiologia , Mãos/inervação , Humanos , Processamento de Imagem Assistida por Computador , Imaginação/fisiologia , Imageamento por Ressonância Magnética , Magnetoencefalografia , Masculino , Movimento/fisiologia , Atrofia Muscular/fisiopatologia , Oxigênio/sangueRESUMO
We performed functional MRI (fMRI) on a patient with a mass lesion while she happened to experience a simple partial seizure. We used regional T2* signal changes to localize seizure-related hemodynamic changes. Seizure activity was associated with changes in MR signal in different regions that showed sequential activation and deactivation. Our study has shown that epileptic activity leads to changes in cerebral hemodynamics. In selected patients, therefore, it might be possible to use fMRI as a noninvasive tool to detect and investigate cortical patterns of activation associated with seizure activity.
Assuntos
Córtex Cerebral/irrigação sanguínea , Circulação Cerebrovascular , Epilepsias Parciais/diagnóstico , Epilepsias Parciais/fisiopatologia , Imageamento por Ressonância Magnética , Neoplasias Encefálicas/complicações , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/fisiopatologia , Córtex Cerebral/fisiopatologia , Epilepsias Parciais/etiologia , Feminino , Glioblastoma/complicações , Glioblastoma/diagnóstico , Glioblastoma/fisiopatologia , Humanos , Pessoa de Meia-IdadeRESUMO
OBJECTIVE: To investigate the effect of repetitive transcranial magnetic stimulation (rTMS) on picture naming. BACKGROUND: Previous studies have shown that rTMS disrupts ongoing speech processes when delivered over frontal or parietal areas of the dominant hemisphere. METHODS: In 15 healthy right-handed male individuals, rTMS trains of 20 Hz with a duration of 2 seconds and an intensity of 55% of maximum stimulator output were delivered either to Wernicke's area, to the right-hemisphere homologue of Wernicke's area, to Broca's area, or to the primary visual cortex. Twenty black-and-white line drawings, which the individuals had to name as quickly as possible, were shown immediately after the completion of rTMS and again 2 minutes later. RESULTS: Immediately after the end of a train over Wernicke's area a shortening of naming latency was observed compared with naming without rTMS (p < 0.001). No significant effects on picture naming were observed 2 minutes later or at any time after stimulation of the right-hemisphere homologues of Wernicke's area, Broca's area, or the visual cortex. CONCLUSION: Repetitive transcranial magnetic stimulation over Wernicke's area leads to a brief facilitation of picture naming by shortening linguistic processing time.
Assuntos
Encéfalo/fisiologia , Idioma , Processos Mentais/fisiologia , Adulto , Lobo Frontal/fisiologia , Humanos , Masculino , Estimulação Física , Tempo de Reação/fisiologia , Lobo Temporal/fisiologia , Estimulação Magnética Transcraniana , Córtex Visual/fisiologiaRESUMO
OBJECTIVE: The anatomical location of the motor area of the hand may be revealed using functional magnetic resonance imaging (fMRI). The motor cortex representation of the intrinsic hand muscles consists of a knob-like structure. This is omega- or epsilon-shaped in the axial plane and hook-shaped in the sagittal plane. As this knob lies on the surface of the brain, it can be stimulated non-invasively by transcranial magnetic stimulation (TMS). It was the aim of our study to identify the hand knob using fMRI and to reveal if the anatomical hand knob corresponds to the hand area of the motor cortex, as identified by TMS, by means of a frameless MRI-based neuronavigation system. METHODS: Suprathreshold transcranial magnetic stimuli were applied over a grid on the left side of the scalp of 4 healthy volunteers. The motor evoked potentials (MEPs) were recorded from the contralateral small hand muscles, and the centers of gravity (CoG) of the MEPs were calculated. The exact anatomical localization of each point on the grid was determined using a frameless MRI-based neuronavigation system. In each subject, the hand area of the motor cortex was visualized using fMRI during sensorimotor activation achieved by clenching the right hand. RESULTS: In all 4 subjects, the activated precentral site in the fMRI and the CoG of the MEP of all investigated muscles lay within the predicted anatomical area, the so-called hand knob. This knob had the form of an omega in two subjects and an epsilon in the other two subjects. CONCLUSIONS: TMS is a reliable method for mapping the motor cortex. The CoG calculated from the motor output maps may be used as an accurate estimation of the location of the represented muscle in the motor cortex.
Assuntos
Mãos/anatomia & histologia , Córtex Motor/anatomia & histologia , Córtex Motor/fisiologia , Estimulação Magnética Transcraniana , Adulto , Mapeamento Encefálico , Humanos , Imageamento por Ressonância MagnéticaRESUMO
OBJECTIVES: Orthostatic tremor was first described by Heilman in 1984. It usually occurs in the legs during stance and decreases markedly during sitting or walking. The aim of this study was to determine if orthostatic tremor is invariably associated with the orthostatic and weight bearing conditions in the arms and legs, and to investigate the features of orthostatic tremor under different levels of peripheral loading. METHODS: Multichannel surface EMG recordings were obtained under different conditions (body posture and peripheral loading) from the proximal arm and leg muscles of seven patients fulfilling the clinical and electrophysiological criteria of orthostatic tremor. RESULTS: In weight bearing positions (stance; weight bearing on the hands on all fours), all patients showed 13 Hz-16 Hz tremor activity, predominantly in the active limb. No tremor activity could be found in a supine position with muscles at rest. Isometric contraction of the limbs in the supine position led to synchronous 13 Hz-16 Hz rhythmic activity in five patients. No tremor was seen when the subjects were suspended in a harness with relaxed legs. Isometric contraction of the legs in this position produced tremor in two patients. A stepwise reduction of the body weight by a harness reduced the tremor activity. Additional loading (10 kg-20 kg) during stance led to an increase in tremor amplitude, but tremor frequency remained unchanged. CONCLUSIONS: Orthostatic tremor is invariably present during stance or other weight bearing positions. It is not, however, always associated with orthostasis. In at least some patients it can be classified as an orthostasis independent action tremor. The failure of peripheral loading to modify tremor frequency indicates that orthostatic tremor may have a central, rather than a peripheral, origin.
Assuntos
Músculos/fisiopatologia , Postura/fisiologia , Tremor/fisiopatologia , Idoso , Peso Corporal/fisiologia , Eletromiografia , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Transcranial magnetic stimulation of the motor cortex may not only elicit excitatory responses in hand muscles contralateral to the stimulated hemisphere, but may also suppress tonic voluntary electromyogram activity in muscles ipsilateral to the stimulation. This inhibition is mediated between the motor cortices via the corpus callosum. AIMS: To investigate motor excitability and interhemispheric (transcallosal) connections in patients with schizophrenia. METHOD: Transcallosal inhibition and motor conduction parameters were investigated in ten patients with schizophrenia and in ten age- and gender-matched healthy subjects. RESULTS: Transcallosal conduction time (TCT) and duration of the inhibition were significantly longer in patients with schizophrenia (mean (s.d.)): TCT, 12.4 (2.9) ms in normal subjects and 15.3 (2.6) ms in patients (P = 0.03); mean duration, 34.1 (4.9) ms in normal subjects and 51.9 (16.8) ms in patients (P = 0.01). CONCLUSIONS: Magnetic motor conduction parameters are unaltered in schizophrenia, but transcallosal inhibition is significantly delayed and prolonged. This may indicate abnormal function of the corpus callosum in these patients.