Dystonia pathogenesis remains unclear; however, findings from basic and clinical research suggest the importance of the interaction between the basal ganglia and cerebellum. After the discovery of disynaptic pathways between the two, much attention has been paid to the cerebellum. Basic research using various dystonia rodent models and clinical studies in dystonia patients continues to provide new pieces of knowledge regarding the role of the cerebellum in dystonia genesis. Herein, we review basic and clinical articles related to dystonia focusing on the cerebellum, and clarify the current understanding of the role of the cerebellum in dystonia pathogenesis. Given the recent evidence providing new hypotheses regarding dystonia pathogenesis, we discuss how the current evidence answers the unsolved clinical questions.

The STA and STV typically are grossly dilated and tortuous, resembling a varix which presented a pulsating mass. AVF of the STA was usually noticed as a small, subcutaneous lump, which, over time, evolves into a painless, swollen, continuous palpable thrill, pulsation, and deforming mass (1). He had presented several clinics due to common medical problems including common cold and hypertension ; however, the mass had not been pointed out. Sometimes, it can be underdiagnosed, because AVF of the STA may be covered by hair. Thus, careful observation of the head especially during the first visit is essential even in patients with no complaints on the head, and physician should be aware that spontaneous AVF of the STA is a differential diagnosis of head mass. The pathogenetic mechanisms have not been fully elucidated. A literature review revealed that 21.9% of AVF patients had hypertension, while others had history of hypertension-related disease including abdominal aortic aneurysm, angina, and cerebral infarction (3). Pathological studies of spontaneous AVF of the STA revealed hyperplasia of the intima-media complex and adventitia as well as partial indistinctness of the internal elastic lamina, mimicking atherosclerotic vascular disease (3). Thus, acquired factors such as hypertension and arteriosclerosis may be attributed to AVF development. Although AVF of the STA is not life-threatening and AVF rupture has not been reported, subsequent head injury may cause AVF rupture (4). Thus, surgical resection or endovascular occlusion should be recommended in high risk patients with growing mass (1). The patient chose follow-up rather than surgical treatment ; thus head injury should be avoided as it may lead to AVF rupture.

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The diagnosis and treatment of functional movement disorders are challenging for clinicians who manage patients with movement disorders. The borderline between functional and organic dystonia is often ambiguous. Patients with functional dystonia are poor responders to pallidal deep brain stimulation (DBS) and are not good candidates for DBS surgery. Thus, if patients with medically refractory dystonia have functional features, they are usually left untreated with DBS surgery. In order to investigate the outcome of functional dystonia in response to pallidal DBS surgery, we retrospectively included five patients with this condition. Their dystonia was diagnosed as organic by dystonia specialists and also as functional according to the Fahn and Williams criteria or the Gupta and Lang Proposed Revisions. Microelectrode recordings in the globus pallidus internus of all patients showed a cell-firing pattern of bursting with interburst intervals, which is considered typical of organic dystonia. Although their clinical course after DBS surgery was incongruent to organic dystonia, the outcome was good. Our results question the possibility to clearly differentiate functional dystonia from organic dystonia. We hypothesized that functional dystonia can coexist with organic dystonia, and that medically intractable dystonia with combined functional and organic features can be successfully treated by DBS surgery.