Based on the ratio-based method, a statistically significant difference was found between LG and HG gliomas. Due to the interindividual variability, however, no reliable individual grading was possible. In contrast, dynamic evaluation allowed LG and HG gliomas to be differentiated with high diagnostic power and, thus, should supplement the conventional method.

We used functional magnetic resonance imaging (FMRI) to study possible cerebral activation patterns associated with unilateral postural tremor in 12 patients with essential tremor (ET), with mimicked postural tremor in 15 control subjects, and with passive wrist oscillation in both groups. During essential tremor, patients showed mainly contralateral activation of the primary motor and primary sensory areas, the globus pallidus, and the thalamus, but bilateral activation of the nucleus dentatus, the cerebellar hemispheres, and the red nucleus. Only 2 patients presented with activity in the medulla close to the olivary nucleus. Unilateral passive wrist oscillation of ET patients resulted in only unilateral activation of the cerebellum, nuclei dentati, and red nuclei. In contrast to the involuntary tremor condition of ET patients, the mimicked tremor condition of the control subjects was not associated with bilateral activity in the cerebellum, nuclei dentati, or red nuclei. Involuntary tremor of ET patients was associated with a significantly larger extent of activation in the cerebellar hemispheres and the red nucleus (p < 0.003) compared with mimicked tremor in the control group. Our FMRI study indicates that ET is mainly associated with an additional contralateral cerebellar pathway activation and overactivity in the cerebellum, red nucleus, and globus pallidus without significant intrinsic olivary activation.

The differential effects of optokinetic stimulation with and without fixation suppression were analysed in an fMRI study in 10 right-handed healthy subjects. Horizontal and vertical small-field optokinetic stimulation activated the same multiple visual, ocular motor and vestibular cortical and subcortical areas in both hemispheres. The extent of activation in each hemisphere was independent of the stimulus direction. All activated areas representing cortical (occipitotemporal cortex, posterior parietal cortex, precentral and posterior median frontal gyrus, prefrontal cortex, medial part of the superior frontal gyrus) and subcortical (caudate nucleus, putamen, globus pallidus and paramedian thalamus) ocular motor structures were activated during optokinetic stimulation as well as during fixation suppression of optokinetic nystagmus. However, the activation was significantly stronger with optokinetc nystagmus compared with fixation suppression. The only relatively increased activity during fixation suppression was seen in the medial part of the superior frontal gyrus (supplementary eye field) and the anterior cingulate gyrus. The anterior insula and the posterior insula (human homologue of the parieto-insular vestibular cortex) were activated during optokinetic nystagmus but not during fixation suppression. A significant right hemispheric predominance (regardless of stimulus direction) was found under both conditions in the visual motion-sensitive and ocular motor areas of the cortex, except the supplementary eye field and anterior cingulate gyrus. This was most prominent in the occipitotemporal cortex, but did not occur in the primary visual cortex and in subcortical ocular motor structures (putamen, globus pallidus and caudate nucleus). Thus, cortical and subcortical activation patterns did not differ for horizontal and vertical optokinetic stimulation, and there was distinct right-hemisphere dominance for visual motion-sensitive and cortical ocular motor areas and the thalamus. Fixation suppression of optokinetic nystagmus yielded four different results: (i) increased activation in the supplementary eye field and anterior cingulate gyrus; (ii) unchanged activation in the visual cortex; (iii) decreased activation in most of the ocular motor areas; and (iv) suppressed activation in the anterior and posterior insula and the thalamus. Activation of the parieto-insular vestibular cortex may be related to ocular motor function rather than self-motion perception.

Single subject and group analyses (n ϭ 12) showed that the eyes-open and eyes-closed states in complete darkness considerably and consistently differ in the patterns of associated brain activation in fMRI. During nonchanging external stimulation, ocular motor and attentional systems were activated when the eyes were open; the visual, somatosensory, vestibular, and auditory systems were activated when the eyes were closed. These data suggest that there are two different states of mental activity: with the eyes closed, an "interoceptive" state characterized by imagination and multisensory activity and with the eyes open, an "exteroceptive" state characterized by attention and ocular motor activity. Our study also shows that the chosen baseline condition may have a considerable impact on activation patterns and on the interpretation of brain activation studies.

The pathophysiology of periodic limb movements and sensory leg discomfort in the restless legs syndrome is unknown. With high-resolution functional magnetic resonance imaging, we localized for the first time cerebral generators associated with sensory leg discomfort and periodic limb movements in 19 patients with restless legs syndrome. During sensory leg discomfort there was mainly bilateral activation of the cerebellum and contralateral activation of the thalamus. During the combined periodic limb movement and sensory leg discomfort conditions, patients also showed activity in the cerebellum and thalamus. In contrast to the sensory leg discomfort condition alone, the combined condition was associated with additional activation in the red nuclei and brainstem close to the reticular formation. Voluntary imitation of periodic limb movements by patients and control subjects was not associated with brainstem activity, but with additional activation in the globus pallidus and motor cortex. These findings indicate that cerebellar and thalamic activation may occur because of sensory leg discomfort and that the red nucleus and brainstem are involved in the generation of periodic limb movements in patients with restless legs syndrome.