RESUMO
A 22-year-old man had leg weakness and decreased hearing. A diagnosis of neurosarcoidosis was made, based on neuroimaging studies and lymph node biopsy. Post-treatment neuroimaging, in particular magnetic resonance imaging along with clinical course, is useful in monitoring response to therapy.
Assuntos
Doenças do Sistema Nervoso/diagnóstico , Sarcoidose/diagnóstico , Adulto , Humanos , Perna (Membro) , Masculino , Debilidade Muscular/etiologia , Doenças do Sistema Nervoso/complicações , Sarcoidose/complicaçõesRESUMO
An important goal of EEG research is to obtain practical methods to improve the spatial resolution of scalp-recorded potentials, i.e., to make surface data more accurately represent local underlying brain sources. This goal may be somewhat different from that of "localizing brain activity with EEG," since the latter approach often involves prior assumptions about the nature of sources. In this paper, we demonstrate that spline-Laplacian, a relatively new approach that can yield dramatic improvement in spatial resolution when average electrode spacing is less than about 3 cm. This approach is mostly independent of assumptions about sources and models of the head. The demonstration involves computer simulations, evoked potentials, normal spontaneous EEG, and epileptic spikes.
Assuntos
Encéfalo/fisiopatologia , Simulação por Computador , Eletroencefalografia/instrumentação , Modelos Neurológicos , Modelos Teóricos , Processamento de Sinais Assistido por Computador/instrumentação , Nível de Alerta/fisiologia , Eletroencefalografia/estatística & dados numéricos , Epilepsia/fisiopatologia , Potenciais Evocados/fisiologia , Humanos , Tempo de Reação/fisiologiaRESUMO
A "picture book" of surface potentials, Laplacians, and magnetic fields due to distributed, neocortical sources is presented. The mathematically simulated data is based on 4200 current sources at the macrocolumn scale. Estimated scalp surface maps are based on the three-concentic spheres model of the head. Emphasis is placed on the effects of sampling with a limited number of electrodes, the choice of reference electrode, and the use of the spline Laplacian to improve spatial resolution. The spline Laplacian is applied to median and ulnar nerve somatosensory evoked potentials and to auditory evoked potentials including P300. Substantial improvement in spatial resolution over conventional methods is obtained. The implementation of practical high resolution EEG systems based on the spline Laplacian is considered.
Assuntos
Mapeamento Encefálico , Encéfalo/fisiologia , Simulação por Computador , Potenciais Evocados Auditivos/fisiologia , Potenciais Somatossensoriais Evocados/fisiologia , Modelos Neurológicos , Algoritmos , Eletrodos , Eletroencefalografia , Humanos , Magnetoencefalografia , Tempo de Reação , Valores de ReferênciaRESUMO
Two patients with unusual central nervous system sarcoid were investigated using computed tomography and magnetic resonance imaging, as well as other x-ray studies. A patient with intramedullary involvement of the spinal cord as well as nerve root involvement was examined. Follow-up examination after treatment with steroids showed a return to normal. The second patient had optic nerve involvement as well as two intracranial parenchymal lesions and granulomatous arachnoiditis. In this patient magnetic resonance imaging offered no advantages over computed tomography in the orbit but was significantly more accurate intracranially.
