huntington 's disease ( hd ) is a dominantly inherited neurodegenerative disease caused by mutations in the it-15 gene on chromosome 4 , which was subsequently renamed htt . more specifically , the disease is linked to expansion of the cag repeat tract of this gene , which codes for polyglutamine repeats in the huntingtin protein . george huntington provided the classic description of the disorder in 1872 from cases in the east hampton area of long island , n.y . the best known manifestation is chorea , which consists of random , fluid involuntary hyperkinetic movements . the term is derived from the greek word o , meaning a traditional circle dance . it is important to note that , while movements in chorea may resemble a dance , they are not rhythmic or repetitive . psychiatric manifestations may include irritability , anxiety , obsessive compulsive disorder , paranoid ideation , and psychosis . depression is the most common psychiatric feature of hd and suicidal ideation occurs in 510% of hd patients . other neurologic manifestations include eye movement abnormalities , cognitive disturbance , pendular knee reflexes , motor impersistence , and postural instability . we describe a mild case of adult onset hd early in the disease course along with mri and diffusion tensor imaging ( dti ) features . increased fractional anisotropy ( fa ) of striatum the patient is a 50-year - old right - handed caucasian male who was diagnosed with hd at age 47 by an outside movement disorders specialist . the patient received a clinical diagnosis of hd given mild neurological findings in the context of genetically confirmed family history . there is a history of depression since his diagnosis , which has become worse over the past week . he was admitted for psychiatric evaluation due to suicidal ideation with plans to overdose on sleeping pills . in addition , he complains of mild cognitive disturbance for at least one year , with difficulty processing information in distracting environments . he has a history of alcohol abuse and quit alcoholics anonymous about six months ago . his medications include paroxetine 30 mg q.h.s . , aripiprazole 5 mg q.a.m . , naltrexone 50 mg q.a.m . , memantine 10 mg b.i.d . , and trazodone 200 mg q.h.s . upon examination , he was alert and oriented to person , place , and time . speech was fluent . cranial nerve examination was significant for saccadic pursuit , slow saccade initiation and velocity in the horizontal and vertical directions , and motor impersistence exhibited by inability to fully protrude the tongue for five seconds . there was only mild intermittent chorea in the fingertips bilaterally and rare lower facial chorea . he improved after one week of inpatient psychotherapy and was released for outpatient psychiatric and neurologic follow - up . images were obtained on a 3.0-tesla phillips achieva mri system . bicaudate ratio ( bcr ) , an imaging measure that correlates with caudate atrophy in hd , was obtained by measuring the shortest inter - caudate distance ( seen as indentation of the frontal horns ) on axial slice and dividing it by the distance between the outer tables of the skull along the same line , multiplied by 100 . phillips fibertrak software was used to analyze dti values on regions of interest which were defined as caudate head bilaterally and putamen bilaterally on axial slices . 1 ) . axial bcr in the patient was increased compared to control at 16 versus 12 , respectively . 2 ) was increased in the bilateral caudate and putamen versus control ( table 1 ) . depression and suicidality were managed with inpatient psychiatry admission and psychotherapy , followed by outpatient therapy . subtle neurologic manifestations included slowing of saccade imitation and velocity , saccadic pursuit , difficulty with tongue protrusion due to motor impersistence , pendular knee reflexes , and postural instability demonstrated by the inability to maintain tandem stance . tetrabenazine is fda approved for the treatment of hd chorea and its efficacy is supported by clinical evidence . caudate atrophy and ex vacuo dilatation of the frontal horns , which is typical for hd , was visualized . increase in fa in white matter is linked to more coherent fiber orientation and normal structure , but in striatal grey matter increased fa is due to neurodegeneration . propose that increased fa in striatal grey matter structures is due to the loss of efferent fibers which in turn leads to increased coherence . for example , in hd there is preferential loss of putamino - pallidal connections that are oriented mediolaterally as relative preservation of anterior - posterior and dorsal - ventral cortical - putaminal fibers . hence , loss of these mediolateral fibers may lead to more uniform fiber orientation and higher fa values . in conclusion , we have presented a patient who is early in the course of huntington 's disease and who already exhibits basal ganglia neurodegeneration with atrophy and changes in fa . dr . fekete received honoraria from medlink , inc . , and serves as a consultant for teva neuroscience , inc . , and lundbeck , llc .
huntington 's disease ( hd ) is a dominantly inherited neurodegenerative disease best known for chorea . 
 the disorder includes numerous other clinical features including mood disorder , eye movement abnormalities , cognitive disturbance , pendular knee reflexes , motor impersistence , and postural instability . 
 we describe a mild case of hd early in the disease course with depression and subtle neurological manifestations . 
 in addition , we review mri and diffusion tensor imaging features in this patient . the bicaudate ratio , a measure of caudate atrophy , was increased . 
 fractional anisotropy values of the bilateral caudate and putamen were increased , signifying neurodegeneration of these structures in hd .