LAUSR

Dear Editor, Thalamic stroke is associated with a number of sequelae (disabilities and pain syndromes) and in particular is known to cause a range of movement disorders including dystoniachoreoathetosis, pseudoathetosis and tremor [1]. Hemiataxia and myoclonic jerks have also been reported. Furthermore, these complex disorders are often associated with a proprioceptive sensory loss adding to the impairment [1]. They are thought to result from lateral posterior thalamic strokes that damage the lemniscal sensory pathways, the cerebellar rubrothalamic tract and the pyramidal tracts [1, 2]. The tremor component of lateral thalamic strokes is a severe, often proximal slow tremor. When the so-called myorhythmic tremor is present at rest and associated with a larger amplitude postural tremor and an intention/goal directed tremor, it is termed Holmes’ tremor (HT) [1, 2]. This is usually associated with midbrain lesions/damage. When associated with dystonia, HT is reported to result from thalamic lesions [1–3]. Post-thalamic complex movement disorders can be challenging in clinical practice as they are particularly disabling and difficult to treat with current pharmacological therapies. This may be in part related to the presence of different abnormal components of movements. Consequently, it is important to explore alternative therapeutic options that can improve more than a component of the abnormal movements. Deep brain stimulation (DBS) targeting the ventral intermediate (VIM) thalamic nucleus is an established effective treatment for various tremors [4]. However, globus pallidum internal (GPi) has been also explored as a DBS target to treat complex tremor [5]. Furthermore, Kobayashi et al. successfully treated four patients affected by severe HT with dual targeting VIM and STN DBS [6]. However, there is not a consensus regarding the most effective target of DBS to treat complex tremor cases. A peculiar region labelled zona incerta (ZI) has been investigated as a target for DBS in tremor cases due to Parkinson’s disease. The ZI is a region lying ventral to the thalamus and dorsomedial to subthalamic nucleus (STN). The posterior region of ZI, called the caudal zona incerta (cZI), is close to the dorsum of STN and it is considered as the motor part [7]. Stimulation of cZI has been recently shown to be more effective in the treatment of tremor [7]. Here, we aim to describe the outcome of successful DBS in two cases of complex movement disorders associated with thalamic infarcts due to different aetiologies (Table 1). One case was treated with unilateral dual targeting GPi/cZI DBS. We believe that this type of dual targeting DBS might be an effective alternative to treat complex cases of tremor associated to other disorders of movement. The second case was treated with bilateral VIM. We aim to highlight that the target selection should be based on individual cases.Written consent form was obtained from each participant.