HYPERGLYCAEMIC HEMIBALLISMUS: IMPLICATIONS FROM CONNECTIVITY ANALYSIS FOR COGNITIVE IMPAIRMENTS.

Hyperglycaemia induced movement disorders, such as hemiballism are rare disorders. The syndrome is characterised by the triad of hemiballism, contralateral T1-hyperintense striatal lesion and non-ketotic hyperglycaemia. Here we report a patient with untreated diabetes presenting with acute onset of hemiballism. MRI revealed T1 hyperintensity of the head of the caudate nucleus and the anterior putamen. The patient also had acantocytosis. Based on the detailed examination of the neuroradiological results and earlier findings we will discuss the pathomechanism. Based on previous findings microhemorrhages, extensive mineralisation, gemistocytic astrocytosis might play a role in the development of the imaging signs. The connectivity pattern of the striatal lesion showed extensive connections to the frontal cortex. In coexistence with that the most severe impairment was found on the phonemic verbal fluency task measuring frontal executive functions.

The role of probabilistic tractography in the surgical treatment of thalamic gliomas.

BACKGROUND: Thalamic gliomas represent a great challenge for neurosurgeons because of the high surgical risk of damaging the surrounding anatomy. Preoperative planning may considerably help the surgeon find the most ideal operative trajectory, avoiding thalamic nuclei and important white matter pathways adjacent to the tumor tissue. Thalamic segmentation is a promising imaging tool based on diffusion tensor magnetic resonance imaging. It provides the possibility to predict the relationship of the tumor to thalamic nuclei. OBJECTIVE: To propose a new tool in thalamic glioma surgery that may help to differentiate between normal thalamus and tumor tissue, making preoperative planning possible and facilitating the choice of the optimal surgical approach and trajectory for neuronavigation-assisted surgery. METHODS: Four patients with thalamic gliomas preoperatively underwent conventional and diffusion-weighted magnetic resonance imaging conducted on 1.5 T. Subsequently, probabilistic tractography and thalamic segmentation were performed with the FSL Software as preoperative planning. We also present a case when thalamic segmentation was applied retrospectively using preoperative images. All patients went through neuronavigation-assisted surgery (1 partial, 4 subtotal resections). RESULTS: Surgery performed based on the output of thalamic segmentation caused no deterioration in the neurological symptoms of our patients. Indeed, we noticed improvement in the neurological condition in 3 cases; furthermore, in 2 patients, a concern-free state was achieved. CONCLUSION: We suggest that thalamic segmentation may be applied successfully and routinely in the surgical treatment of thalamic gliomas.

Target identification for stereotactic thalamotomy using diffusion tractography.

BACKGROUND: Stereotactic targets for thalamotomy are usually derived from population-based coordinates. Individual anatomy is used only to scale the coordinates based on the location of some internal guide points. While on conventional MR imaging the thalamic nuclei are indistinguishable, recently it has become possible to identify individual thalamic nuclei using different connectivity profiles, as defined by MR diffusion tractography. METHODOLOGY AND PRINCIPAL FINDINGS: Here we investigated the inter-individual variation of the location of target nuclei for thalamotomy: the putative ventralis oralis posterior (Vop) and the ventral intermedius (Vim) nucleus as defined by probabilistic tractography. We showed that the mean inter-individual distance of the peak Vop location is 7.33 mm and 7.42 mm for Vim. The mean overlap between individual Vop nuclei was 40.2% and it was 31.8% for Vim nuclei. As a proof of concept, we also present a patient who underwent Vop thalamotomy for untreatable tremor caused by traumatic brain injury and another patient who underwent Vim thalamotomy for essential tremor. The probabilistic tractography indicated that the successful tremor control was achieved with lesions in the Vop and Vim respectively. CONCLUSIONS: Our data call attention to the need for a better appreciation of the individual anatomy when planning stereotactic functional neurosurgery.

The enhancement of cortical excitability over the DLPFC before and during training impairs categorization in the prototype distortion task.

The present study investigated the effects of transcranial weak electrical stimulation techniques applied to the right and left dorsolateral prefrontal cortex (DLPFC) on categorization learning measured using a variant of the prototype distortion task. During the training phase of this task subjects saw low- and high distortions of a prototype dot-pattern. 60 participants received 10min of either anodal or cathodal transcranial direct current (tDCS), transcranial random noise (tRNS) or sham stimulation before and during the training. We have assessed the effects of the intervention during a test phase, where the subjects had to decide whether the consecutive high- and low-distortion versions of the prototype or random patterns that were presented belonged to the category established in the training phase. Our results show that the categorization of prototypes is significantly impaired by the application of anodal tDCS and tRNS to the DLPFC. The prototype-effect, observable in the case of the sham stimulation group, was severed in all active stimulation conditions.