Thalamic ventral-Oralis complex/rostral zona incerta deep brain stimulation for midline tremor.

BACKGROUND: Midline Tremor is defined as an isolated or combined tremor that affects the neck, trunk, jaw, tongue, and/or voice and could be part of Essential Tremor (ET), or dystonic tremor. The clinical efficacy of deep brain stimulation for Midline Tremor has been rarely reported. The Ventral Intermediate Nucleus and Globus Pallidus Internus are the preferred targets, but with variable outcomes. Thalamic Ventral-Oralis (VO) complex and Zona Incerta (ZI) are emerging targets for tremor control in various etiologies. OBJECTIVE: To report on neuroradiological, neurophysiological targeting and long-term efficacy of thalamic Ventral-Oralis complex and Zona Incerta deep brain stimulation in Midline Tremor. METHODS: Three patients (two males and one female) with Midline Tremor in dystonic syndromes were recruited for this open-label study. Clinical, surgical, neurophysiological intraoperative testing and long-term follow-up data are reported. RESULTS: Intraoperative testing and reconstruction of volume of tissue activated confirmed the position of the electrodes in the area stimulated between the thalamic Ventral-Oralis complex and Zona Incerta in all patients. All three patients showed optimal control of both tremor and dystonic features at short-term (6 months) and long-term follow-up (up to 6 years). No adverse events occurred. CONCLUSION: In the syndromes of Midline Tremor of various origins, the best target for DBS might be difficult to identify. Our results showed that thalamic Ventral-Oralis complex/Zona Incerta may be a viable and safe option even in specific forms of tremor with axial distribution.

A new perspective on positive symptoms: expression of damage or self-defence mechanism of the brain?

Usually, positive neurological symptoms are considered as the consequence of a mere, afinalistic and abnormal increase in function of specific brain areas. However, according to the Theory of Active Inference, which argues that action and perception constitute a loop that updates expectations according to a Bayesian model, the brain is rather an explorer that formulates hypotheses and tests them to assess the correspondence between internal models and reality. Moreover, the cerebral cortex is characterised by a continuous "conflict" between different brain areas, which constantly attempt to expand in order to acquire more of the limited available computational resources, by means of their dopamine-induced neuroplasticity. Thus, it has recently been suggested that dreams, during rapid eye movement sleep (REMS), protect visual brain areas (deprived of their stimuli during rest) from being conquered by other normally stimulated ones. It is therefore conceivable that positive symptoms also have a functional importance for the brain. We evaluate supporting literature data of a 'defensive' role of positive symptoms and the relevance of dopamine-induced neuroplasticity in the context of neurodegenerative and psychiatric diseases. Furthermore, the possible functional significance of idiopathic REMS-related behavioural disorder as well as phantom limb syndrome is examined. We suggest that positive neurological symptoms are not merely a passive expression of a damage, but active efforts, related to dopamine-induced plasticity, to maintain a correct relationship between the external world and its brain representation, thus preventing healthy cortical areas from ousting injured ones.