abnormal involuntary movements may appear in any part of the body , and can be embarrassing , distressing , disfiguring or dangerous .
tremor is an involuntary rhythmic oscillation of one or more parts of body about a fixed plane in space .
tremors are observed with the use of various drugs , including tricyclic antidepressants , monoaminooxidase inhibitors , antipsychotics , lithium , valproate , lamotrigine , antihistamines , thyroxine and nicotine .
these tremors tend to disappear after withdrawal of the offending drug . in a young person receiving psychotropic medication , appearance of unilateral tremor
is unusual and various diagnostic possibilities need to be kept in mind . in this report
a 26-year - old young male , employed as a tailor , from rural background , presented with 6 months duration of symptoms suggestive of mania . at the time of admission , detailed clinical examination including bedside neurological examination revealed no abnormalities .
he was prescribed risperidone 2 mg / day and diazepam 30 mg / day on the first day of admission . as he remained aggressive even after this sodium valproate 500 mg / day
it was observed that he developed regular rhythmic movements of his neck and right hand , with no other extrapyramidal symptoms . for optimal control of his manic symptoms the dose of risperidone
was increased to a maximum of 8 mg and valproate to 1400 mg on day 46 of his admission .
trihexyphenidyl 2 mg / day was also added to his ongoing therapy , in view of tremors . however
, these movements became more prominent involving the neck along with head and right upper limb .
they were rhythmic and regular with 3 - 4 hz , and present at rest .
the tremor used to disappear as the target was approached , thus did not cause any difficulty in eating or writing .
as this symptom caused significant distress to the patient , valproate was stopped on day 60
. however , there was no improvement even after one week of this , and hence risperidone was also stopped .
two weeks after stopping risperidone , there were no visible tremor at rest , but it would appear when he became emotionally disturbed .
he was discharged on olanzepine ( 10 mg / day ) , which he tolerated well , and remitted completely from mania .
the liver function tests showed raised liver enzyme -sgot which was 93iu ( 0 - 25 ) in the first week which returned to baseline subsequently .
investigations for complete blood count , wilson 's disease , thyroid abnormalities and folic acid levels were normal . low serum vitamin b12 levels ( 41 pg / ml ; normal > 201 pg / ml ) and serum ceruloplasmin on lower side of normal range ( 25 microg / dl , normal range 25 - 63 microg/ dl ) were detected .
the common causes for unilateral tremor include parkinson 's disease , wilson 's disease , neuropathic , familial essential tremor syndrome , holmes tremor and psychogenic tremor .
rubral tremor is a special type of visible tremor appearing as flexion - extension movement at wrist and fingers present at rest and during action , not associated with bradykinesia or cogwheel rigidity and considered as a separate entity compared to holmes tremor .
thus our patient had rubral tremor of right upper limb associated with tremor of the neck .
cases of rubral tremor developing following exposure to fluphenazine and risperidone have been reported . however , both these cases had symptom or sign suggesting of structural brain damage , unlike in our case .
the clinical examination and laboratory investigations ruled out other causes for the tremor and suggested a possibility of drug - induced tremor in this case .
causality analysis using the naranjo algorithm suggested that risperidone was scored to be the probable causal agent .
however , other contributory factors could have been vitamin b12 deficiency and the concurrent use of valproate .
there is a suggestion that bipolar illness itself may increase risk for antipsychotic - induced movement disorder .
furthermore , this patient 's nicotine use may have suppressed features of drug induced parkinsonism , causing tremors to dominate the clinical presentation .
in a young person with a unilateral tremor of acute onset , drug - induced movement disorder must be considered among the diagnostic possibilities . the role of concurrent valproate therapy and vitamin b12 deficiency as suggested in this atypical case presentation require further elucidation .
this case highlights the complexities involved in identifying drug induced movement disorders in patients receiving multiple psychotropic medications .
 identification and management of drug - induced movement disorders is a clinical challenge , more so when the clinical presentation is atypical . 
 a young male with acute mania was under treatment with sodium valproate and risperidone . 
 he developed tremors of right hand and neck . 
 these were present at rest and exacerbated by mental activity , when under observation and during voluntarily initiated activity . 
 there were no associated extra pyramidal symptoms or cerebellar signs . 
 investigations for other common causes of tremors did not reveal any evidence except for low value of serum vitamin b12 levels . 
 the tremors persisted after the withdrawal of valproate , but resolved following the withdrawal of risperidone . 
 it is a common dictum that drug - induced tremors are bilateral . 
 this may not be true always as we found out in our case . 
 these movements were probably induced by risperidone . 
 this atypical presentation could be due to concurrent use of valproate and low serum vitamin b12 levels . 
Introduction
Case Report
Discussion
Conclusion