dystonias are a heterogeneous group of movement disorders defined by involuntary muscle contractions causing repetitive and twisting movements or abnormal postures ( 1,2 ) . depending on etiology , dystonia can be primary ( without a known cause ) or secondary to acquired brain lesions ( 3 ) . primary or hereditary dystonias are classified by their heterogeneous genetic background into 20 different genetic forms ( dyt1 to dyt20 ) ( 4 ) . however , a few genes ( tor1a/ dyt1 , gtpch/ dyt5 , thap1/ dyt6 , sarcoglycan/ dyt11 , na / k atpase 3 subunit/ dyt12 ) for primary dystonia have been identified so far ( 5 ) . the pharmacologic treatment for primary generalized dystonia including a combination of anticholinergics , dopamine agonists and antagonists , and benzodiazepines , are usually unsatisfactory with transient effects ( 3 ) . therefore , surgical interventions have been suggested to relieve symptoms of patients with medically refractory disease ( 6,7 ) . in recent years , pallidal deep brain stimulation ( dbs ) has been used as a safe and effective method to treat advanced , disabling primary dystonia , especially dyt1 form and secondary dystonia such as tardive dystonia ( 3,8 ) . however , due to existence of clinically and genetically diverse forms of primary dystonia , little is known about the results of bilateral pallidal stimulation in other types such as dyt6 dystonia ( 7 ) . dyt6 gene has been recently identified and there have been few studies exploring its treatment results with dbs ( 9 ) . 
 
 in this study , we present a case of primary dyt6 dystonia and describe his clinical features , in addition to his initial response to bilateral dbs . this would be the first report of dyt6 dystonia treated with pallidal dbs in iran . a 21 years old boy presented to our clinic with dystonic movements in his right hand since the age of 8 , gradually had progressed to other body regions . at the time of our first visit ( 11 years after the disease onset ) , the patient s bfmdrs ( burke - fahn - marsden dystonia rating scale ) score was 32 ( table 1 ) . genetic assessment for the patient using dna from peripheral blood leukocytes and pcr amplification revealed mutation in thap1 by sequence analysis . the patient had used trihexyphenidyl 10 - 15 mg and clonazepam 2 - 3 mg daily . the patient underwent bilateral deep brain stimulation in the sensorimotor region of the posteroventral gpi . dbs parameters set on amplitude of 2.5 v , frequency 145 hz , pulse duration 90 s after surgery . according to clinical effects , after one year follow - up the parameters were adjusted to an amplitude of 2.7 v , frequency of 160 hz , and pulse width of 90 s . bfmdrs score of the patient reduced to 7 one year after surgery ( total 78% improvement ) . dyt6 dystonia is associated with mutation of the gene encoding thanatos - associated protein ( thap1 ) ( 10 ) and first has been described by almasy et al . in 1997 ( 2 ) . the disease mainly involves upper limbs , cervical or cranial muscles and it may be characterized by early onset cervico - laryngeal dystonia ( 2,4,11 ) . medically refractory cases of dyt1 dystonia are considered for surgical treatments such as dbs ( 8) . however , there is little experience with dbs in the treatment of dyt6 dystonia . to date , only 6 studies ( including 12 patients ) have been presented in the literature to demonstrate result of dbs in this specific group of dystonia patients ( table 2 ) . zittel et al . reported two dyt6 dystonia patients who treated with bilateral pallidal deep brain stimulation . these patients experienced moderate symptoms improvement and also no improvement in their oromandibular or laryngeal dystonia was observed even seven years after surgery ( 4 ) . excellent effects of gpi - dbs in dyt6 dystonia was only reported by jeck et al . they argue that this favorable result from dbs is due to a specific thap1 mutation in their patient ( 10 ) . in another report by franca et al . , satisfactory results were obtained from dbs of a portuguese dyt6 patient 2 months after surgery ( 59% improvement of bfmdrs score ) and cervical and oromandibular dystonia improvement was remarkable ( 12 ) . 
 
 finally , in a recent study on three patients with dyt6 dystonia , pallidal dbs had a modest effect on symptoms improvement during the first two years after surgery and even some symptom regression he experienced near significant resolution of dystonic movements on extremities and mouth during a 12-month follow up after surgery . we suggest gpi dbs as a usefull and effective treatment for dyt6 positive patients .
little is known about the results of pallidal deep brain stimulation ( dbs ) in dyt6 dystonia . 
 this will be the first report of dyt6 dystonia treated with pallidal dbs from iran . a 21 years old male patient with dyt6 dystonia underwent bilateral deep brain stimulation . 
 the target of dbs was the sensorimotor region of the posteroventral globus pallidus internus ( gpi ) . 
 dbs parameters included an amplitude of 2.7 v , frequency of 160 hz , and pulse width of 90 s which were adjusted according to the patient 's response 12 months after surgery . 
 treatment outcome was measured by the patient s burke - fahn - marsden dystonia rating scale ( bfmdrs ) score . before surgery , 
 the patient 's bfmdrs score was 32 . 
 however , bfmdrs score reduced to 7 at one year follow up after surgery ( 78% improvement of total score ) . 
 dystonic symptoms of extremities and mouth completely resolved . also speech and swallowing function 
 significantly improved . 
 although previous observations reported a poor to moderate response in speech , we found dbs as an effective treatment not only for dystonic features , but also for speech improvement of dyt6 dystonia .