Alexander Thiel

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Management of low-grade gliomas continues to be a challenging task, because CT and MRI do not always differentiate from nontumoral lesions. Furthermore, tumor extent and aggressiveness often remain unclear because of a lack of contrast enhancement. Previous studies indicated that large neutral amino acid tracers accumulate in most brain tumors, including(More)
The brain may use two strategies to recover from poststroke aphasia: the structural repair of primarily speech-relevant regions or the activation of compensatory areas. We studied the cortical metabolic recovery in aphasic stroke patients with positron emission tomography (PET) at rest and during word repetition. The left supplementary motor area (SMA)(More)
Activation studies in patients with aphasia due to stroke or tumours in the dominant hemisphere have revealed effects of disinhibition in ipsilateral perilesional and in contralateral homotopic cortical regions, referred to as collateral and transcallosal disinhibition. These findings were supported by studies with selective disturbance of cortical areas by(More)
BACKGROUND AND PURPOSE Functional neuroimaging studies have demonstrated right inferior frontal gyrus (IFG) activation in poststroke aphasia. It remains unclear whether this activation is essential for language performance. We tested this hypothesis in a positron emission tomography (PET) activation study during a semantic task with repetitive transcranial(More)
BACKGROUND AND PURPOSE In a prospective, double-blind, placebo-controlled study, it was investigated whether piracetam improves language recovery in poststroke aphasia assessed by neuropsychological tests and activation PET measurement of cerebral blood flow. METHODS Twenty-four stroke patients with aphasia were randomly allocated to 2 groups: 12 patients(More)
As previous functional neuroimaging studies could not settle the controversy regarding the contribution of dominant and subdominant hemisphere to recovery from poststroke aphasia, language performance was related to H2(15)O-positron emission tomographic activation patterns in 23 right-handed aphasic patients 2 and 8 weeks after stroke. In patients(More)
Disturbance of neurologic function in disorders of the central nervous system is expressed as an altered activation pattern in functional networks employed by specific tasks and can be studied by functional imaging modalities, e.g., positron emission tomography. Language, a complex brain function, is based on the interplay of a distributed network in which(More)
We investigated plasticity of language networks exposed to slowly evolving brain damage. Single subject 0-15-water language activation positron emission tomography studies were analyzed in 61 right-handed patients with brain tumors of the left hemisphere, and 12 normal controls. In controls, activations were found in left Brodmann's Area (BA)44 and BA45,(More)
OBJECTIVE Evaluation of the accuracy of preoperative localization of language-related cortex by magnetic resonance imaging-guided positron emission tomography. METHODS Patients with gliomas in the left dominant hemisphere were examined preoperatively with magnetic resonance imaging-guided positron emission tomography and intraoperatively by electrical(More)
BACKGROUND AND PURPOSE Modulation of activity in language networks using repetitive transcranial magnetic stimulation (rTMS) may possibly support recovery from poststroke aphasia. Case series and feasibility studies seem to indicate a therapeutic effect; however, randomized sham-controlled, proof-of-principle studies relating clinical effects to activation(More)