Website Edition: August/September 2010

An Approach to the Patient with Chorea

By Ruth H. Walker, MB, ChB, PhD
James J. Peters Veterans' Affairs Medical Center
Bronx, New York USA
Special to The Movement Disorder Society

Introduction

The term chorea is derived from the Greek term for dance (choros, in fact, a particular type of circle dance), and suggests the fluidity of the movements, but not their arrhythmicity. The movements can involve any body part - limbs, trunk, neck or face - and typically flit rapidly from region to region in an irregular, unpredictable, manner. The underlying pathophysiology is likely to be due to a delicate balance of activity of the direct and indirect basal ganglia pathways, and the multitude of possible causes of chorea may be indicative of the vulnerability of this balance to disruption. Chorea may be a feature both of metabolic disturbances and of structural lesions, which appear to affect neurotransmission in an apparently identical manner to that seen in neurodegenerative diseases.

A large number of neurological disorders can cause chorea and diagnosis can be challenging (Click here to view flow chart). Chorea can be present in a number of well-characterized genetic disorders, but also may occur as a rarer phenotypic variation in others. Despite extensive work-up some patients inevitably remain undiagnosed. Clues to the diagnosis of chorea may be found in features of the family and medical history and with careful clinical examination.

Family history

Inheritance

If present, a positive, or even suggestive, family history can indicate a disorder with autosomal dominant (AD), autosomal recessive (AR), or X-linked recessive, inheritance, and limits the number of disorders which needs to be considered for a particular patient.

However, the absence of a family history of neurological disease does not exclude a genetic disorder for many possible reasons. A parent carrying a causative mutation might have died before the disease manifested, especially in the case of disorders in which there is anticipation, i.e. earlier disease onset with successive generations. Partial penetrance can be seen, for example, in Huntington's disease (HD) when the trinucleotide repeat expansion is in the intermediate range. Other possible explanations are that phenotypic variation might result in the disorder not being recognized in other family members. Significant psychiatric features, as often seen in basal ganglia disorders, may have resulted in long term care in a setting in which other neurological features were not recognized, or were attributed to medications, i.e. tardive dyskinesia.

Involvement of multiple siblings in one generation indicates AR inheritance, but might not be evident in a small sibship. The possibility that non-paternity might be unmasked by genetic testing should always be addressed. Lastly, de novo mutations may arise and be the explanation for the absence of a family history.

Autosomal dominant inheritance

The prototypical AD chorea is HD, and historically this was assumed to be the diagnosis in any patient with an AD pattern of inheritance and chorea. However, now that genetic confirmation is available it has become apparent that a number of patients with this phenotype have another disease. Several disorders are now described as being "HD-like (HDL)". Of these, HDL1 (a prion disorder), HDL2 (see below), and HDL4 (spinocerebellar ataxia [SCA] 17) show AD inheritance.

In addition to SCA17 (Schneider et al., 2006), several other AD spinocerebellar ataxias (SCAs) can cause movement disorders. The size of the trinucleotide repeat expansion does not in general appear to correlate with the phenotype. Movement disorders are most commonly seen in SCAs 1,2, 3 (Machado-Joseph disease), often, but not invariably, in addition to cerebellar findings. Dentatorubropallidoluysian atrophy (DRPLA) is also a trinucleotide repeat expansion disorder, and may present with movement disorders, including chorea and myoclonus, although more usual features are ataxia and dementia (Tsuji, 2010).

Neuroferritinopathy is the one AD inherited disorder (to date) associated with brain iron accumulation, and can be diagnosed by low serum ferritin (Curtis et al., 2001) (see accompanying article by Kruer and Hayflick). AD inheritance of chorea which does not progress and which is not associated with other neuropsychiatric features suggests benign hereditary chorea (Kleiner-Fisman and Lang, 2007).

Autosomal recessive inheritance

In geographically or socially isolated communities, or where familial intermarriage is traditional, there is an increased likelihood of known or possible consanguinity, increasing the chances of an AR disorder. AR inheritance is characteristic of the majority of the inherited pediatric metabolic disorders. Clinical presentation is dependent upon the stage of brain maturation and myelination. Later presentation and atypical phenotypes may be seen when the causative mutations result in partial residual enzyme activity.

Most NBIA disorders have AR inheritance (see accompanying article by Kruer and Hayflick).

Chorea has been occasionally reported in Niemann-Pick C, chronic GM2 and late-onset GM1 gangliosidoses, neuronal intranuclear inclusion disease, and metachromatic leukodystrophy.

The autosomal recessive ataxias, including Friedreich's ataxia, ataxia-telangiectasia and the ataxias with oculomotor apraxia (AOA) 1 and 2 can occasionally result in chorea.

X-linked inheritance

There are relatively few causes of X-linked causes of chorea, in which inheritance is characterized by the presence of affected maternal male relatives, and the absence of male-male transmission. These include McLeod neuroacanthocytosis syndrome (Danek et al., 2001) (see accompanying article by Riccioppo Rodrigues) and Lesch-Nyhan syndrome. These should be clearly distinguished from each other by the age of onset and additional neurological features. Rarely, X-linked Filipino parkinsonism-dystonia (Lubag; DYT3) can present with chorea (Evidente et al., 2002).

Mitochondrial disorders

Chorea and dystonia are features of Leigh's syndrome, which can be caused by a number of different mitochondrial mutations. It typically presents in early childhood, but may occasionally present in adulthood. Acute encephalopathy, seizures, psychomotor retardation, hypotonia, spasticity, myopathy, and dysarthria may also be seen. In some cases there may be an overlap with mitochondrial encephalopathy with stroke-like episodes (MELAS). Other mitochondrial disorders may also present with chorea.

Ethnic background

In a small number of disorders the patient's racial and ethnic background can be informative and even diagnostic. Lubag (X-linked parkinsonism-dystonia; DYT3) is found solely amongst Filipinos from province of Capiz on the island of Panay. Although not typical, chorea can occasionally be seen. Males are usually affected, but occasionally affected carrier females have been reported, one of whom had chorea. This diagnosis should be considered in any Filipino with any movement disorder to facilitate genetic testing and appropriate counseling (Evidente et al., 2002). Huntington's disease-like 2 (HDL2) has been reported to date only in people of black African ancestry. As with HD, this is an AD-inherited trinucleotide expansion disease which presents with chorea and other movement disorders, and cognitive impairment (Holmes et al., 2001). Acanthocytosis can be seen in approximately 10% of cases.

Features of medical history

Age of onset

Infancy/childhood onset

The commonest cause of acute chorea in childhood is Sydenham's chorea, following beta-hemolytic streptococcal group A infection (Gilbert, 2009). A more insidious onset, especially where there are other neurological abnormalities, suggests a pediatric metabolic disorder. Dystonia appears to be more common than chorea for the disorders with early onset, probably related to the degree of long-tract myelination.

The commonest etiology of chronic movement disorders in this population is cerebral palsy (CP). Spasticity may evolve to a hyperkinetic disorder with age. The history of the disorder should be diagnostic. Dystonia is more commonly seen, but chorea can also occur, and in some cases can be quite violent, being precipitated, for example by metabolic stress such as infection. Severe cases may require general anesthesia or neurosurgical intervention.

Adult onset

Adult onset, often following the reproductive years, is typical for the AD disorders. For the trinucleotide repeat expansion, the age of onset is inversely related to the size of the trinucleotide repeat disorders. However, young-onset forms are not uncommon, particularly with paternal inheritance.

Atypical forms of AR disorders can present during adulthood, for example, when the causative mutations result in only partial enzyme deficiency. This can be seen with pantothenate kinase-associated neurodegeneration (PKAN) (see accompanying article by Kruer and Hayflick) and ataxia-telangiectasia (Verhagen et al., 2009). Other AR disorders, such as chorea-acanthocytosis (ChAc) (Danek and Walker, 2005) (see accompanying article by Riccioppo Rodrigues), present later, for reasons which are unclear. In ChAc subtle psychiatric signs of basal ganglia dysfunction may be present during adolescence. In other disorders, such as aceruloplasminemia, it is likely that symptoms emerge once a critical amount of substrate, e.g. iron in the case of aceruloplasminemia, has accumulated in the target organs (McNeill et al., 2008).

The X-linked McLeod neuroacanthocytosis syndrome may be detected prior to neuropsychiatric manifestations if blood-typing is performed, or if serological tests demonstrate elevated levels of creatine kinase or liver enzymes; however, symptoms typically emerge in middle-age (Danek et al., 2001; Jung et al., 2001) (see accompanying article by Riccioppo Rodrigues).

Late adult onset

The entity of "senile chorea" is obsolete as these cases are now recognized as most probably being due to late onset of genetic disorders, including HD. Elderly patients who develop chorea should be thoroughly evaluated for a paraneoplastic syndrome or for an autoimmune disorder, especially if female. Late onset of HD may be seen with CAG repeats in the borderline range. As the trinucleotide repeat will most likely expand with inheritance, genetic counseling issues in this age group may potentially involve several younger generations.

Disease progression

As with many other neurological and medical disorders, the characteristics of disease onset and progression can narrow the differential diagnosis. Sudden onset of chorea which does not progress indicates a stroke, either ischemic or hemorrhagic. Acute onset of chorea in childhood is most often due to Sydenham's chorea.

Acute or subacute onset of chorea related to a medical illness suggests a common underlying metabolic, post-infectious, or autoimmune process. Examples of these include non-ketotic hyperglycemia in a non-insulin-dependent diabetic patient, and other metabolic disorders such as hyper-and hyponatremia, hyper- and hypocalcemia, hypomagnesemia, hyperthyroidism, hypo- and hyperparathyroidism. A variety of autoimmune diseases have been associated with movement disorders, including chorea; these include systemic lupus erythematosus (SLE), Sjögren's syndrome, and anti-phospholipid antibody syndrome.

A sub-acute presentation may be seen with prion diseases, specifically new variant Creutzfeldt-Jakob disease (Bowen et al., 2000) or with slowly growing mass lesions. Paraneoplastic syndromes can present similarly, and have been reported to occur with a variety of tumors, including renal, small cell lung, breast, Hodgkins and non-Hodgkins lymphoma. The causative auto-antibodies include anti-CRMP-5/CV2, anti-Hu, anti-Yo, and others. Bizarre movements can be seen in anti-NMDA-receptor antibody syndrome, which may be choreiform in nature, although are typically more complex (Dalmau et al., 2007).

A chronic, progressive disease course is likely to indicate a neurodegenerative process, for example due to HD, the AD ataxias, a neuroacanthocytosis syndrome, or a neurodegeneration with iron accumulation (NBIA) syndrome. The appearance and progression of neurological, cognitive or psychiatric findings due to more widespread neurodegeneration can be informative.

Stable, chronic chorea which develops gradually, but does not progress, may be attributed to a medication, either as a direct side-effect, or as a tardive syndrome. A detailed medication history should reveal this diagnosis. Benign hereditary chorea should be considered in the setting of childhood onset and an AD family history.

Episodic chorea may be due to one of the paroxysmal hyperkinetic disorders, although these are more typically dystonic and are classified with the genetic dystonias. The diagnosis of these disorders was previously based upon their phenomenology and precipitating factors, but this is being replaced by molecular identification (Mink, 2007). These include paroxysmal non-kinesigenic dyskinesia (paroxysmal dystonic choreoathetosis; DYT8), which is precipitated by alcohol, caffeine, stress, extremes of temperature, fatigue, or fasting; paroxysmal choreoathetosis with spasticity (DYT9), which is brought on by exercise, stress, alcohol consumption and sleep deprivation; paroxysmal kinesigenic dyskinesia (PKD; paroxysmal kinesigenic dystonia; DYT10), characterized by very frequent, brief, episodes of limb dystonia following movement; paroxysmal exertional dyskinesia (DYT18) develops following more prolonged exertion than PKD, and is due to mutations of the glucose transporter GLUT1. Many of these disorders appear to be due to mutations of ion channels and respond to anticonvulsants. Rarely, episodic chorea may be psychogenic in etiology.

Medical history

The medical history may reveal potential causes or associations of chorea. Non-neurological features can be very useful in indicating a specific inherited metabolic disorder in pediatric cases (Gilbert, 2009).

In addition to the endocrine disorders mentioned above, changes in levels of reproductive hormones can be responsible, including pregnancy (chorea gravidarum) and estrogen/progesterone-containing medications (Caviness and Muenter, 1991; Suchowersky and Muthipeedika, 2005) used either as contraceptive or as hormone replacement therapy. Alternatively, suppression of estrogen with LHRH may cause chorea.

Any history of an auto-immune disorder should be evaluated as a possible cause of chorea. Polycythemia vera may cause or present with chorea, possibly due to hyperviscosity resulting in basal ganglia ischemia (Kumar et al., 2009).

Celiac disease has been associated with a number of neurologic complications, including chorea, most likely due to an auto-immune mechanism, and may respond to a gluten-free diet.

Liver disease and chorea may co-occur in several conditions. The most important disorder to exclude is Wilson's disease, as therapeutic intervention is possible. However, chorea is rare, and not typically seen on presentation (Machado et al., 2006). Slit-lamp examination should be performed, and serum ceruloplasmin levels and 24 hour copper excretion measured. Once Wilson's disease has been excluded, a neuroacanthocytosis syndrome should be considered, either ChAc or McLeod syndrome. Liver disease due to a variety of etiologies may also cause acquired hepatocerebral degeneration which causes various movement disorders, likely due to manganese deposition in the basal ganglia which may be seen in brain MRI.

Cardiac disease, specifically cardiomyopathy, is frequently found in Friedreich's ataxia. Cardiomyopathy and arrhythmias, are seen in McLeod syndrome, and are a potentially treatable cause of morbidity and mortality. A history of a recent infection may be related to chorea, most apparently in children with Sydenham's chorea. Chorea may also be a consequence of striatal necrosis following encephalitic illness.

Patients should be thoroughly evaluated for any systemic findings which might be suggestive of cancer, such as weight loss, lymphadenopathy, chronic cough, change in bowel habit, etc. However, absence of these does not rule out a paraneoplastic syndrome, as tumor growth may be suppressed by the auto-antibodies which are responsible for the neurological findings, and tumors can be notoriously hard to detect in these circumstances.

Medication and drug use

Chorea can be caused by a variety of medications, and can be either as a direct, and often predictable, effect, as with dopaminergic agents in Parkinson's disease.

The movements of tardive dyskinesia (TD) are more accurately described as chorea, although dystonia can also be seen, and is more disabling. Although much less common than with typical neuroleptics, TD has been reported with many of the newer atypical antipsychotics. Other dopaminergic antagonists, such as those used for nausea, specifically compazine and metoclopromide, may also cause TD.

It may be hard to confirm or refute the association of other medications with TD, as the movements may get worse, rather than resolving, when the offending agent is stopped. Other classes of medications have also been implicated including selective serotonin re-uptake inhibitors (SSRIs), lithium, and anticonvulsant medications.

Chorea may be seen as a direct side-effect of other medications, including dilantin, gabapentin, lamotrigine, and lithium. This may be seen particularly when there is an underlying structural brain lesion, as in CP. Stimulants which release catecholamines can be causative, whether used therapeutically, or recreationally, such as amphetamine and cocaine. The timing and the resolution of the movements with discontinuation of the offending agent makes the diagnosis and treatment straightforward.

Practitioners should be alert to the appearance of atypical neurologic and cognitive features in patients who have been diagnosed with TD following neuroleptic use for psychiatric disease, as these may be indicative of a neurodegenerative basal ganglia disorder.

Associated neurological features

Distribution of chorea

The appearance of chorea is not typically helpful in elucidating the diagnosis. The exceptions to this are when there is prominent orofacial involvement, or markedly asymmetric involvement of the limbs.

In neuroleptic-induced tardive dyskinesia facial muscles alone are most commonly affected. Prominent and severe orofacial and lingual involvement can be seen in ChAc and PKAN. In ChAc the tongue movements are dystonic, and specifically induced by eating.

Unilateral chorea in adults is often due to structural lesions. These are most commonly due to focal lesions of the basal ganglia, but may be seen with lesions in other locations, for reasons which are unclear.

Peripheral neuropathy

Peripheral neuropathy, as demonstrated by hyporeflexia and peripheral sensory changes is characteristic of the two core neuroacanthocytosis syndromes, ChAc and McLeod syndrome, and of some of the inherited ataxias, both AR (Friedreich's ataxia, AOA1and AOA2) and AD (SCA 1, 2, 3).

Hyperreflexia

Upper motor neuron signs can be seen with disorders in which there is involvement of the cortex, e.g. HD, HDL2, and the SCAs. Asymmetric hyperreflexia may indicate a focal lesion.

Ataxia

The inherited ataxias, both AD and AR, typically cause ataxia and eye movement abnormalities, however, occasionally these may be absent.

Cognitive and psychiatric symptoms

Changes in personality, frontal or subcortical dementia, and psychiatric disease can be seen in a number of the neurodegenerative causes of chorea, and are most likely due to involvement of the frontal cortex and caudate nucleus. (see accompanying article by Walterfang) Subtle changes in cognition can be detected by neuropsychological testing, for example, in pre-symptomatic carriers of the HD mutation.

Ophthalmologic findings

Analogous to the fragments of movements intruding into voluntary limb movements, intrusions of square-wave jerks can interfere with fixation of gaze. These are best documented in HD, but can be seen also in chorea of other etiologies. Impaired smooth pursuit and saccadic gaze, or ophthalmoplegia, may suggest a cerebellar disorder.

Pigmentary retinopathy is indicative of PKAN and is an invariable feature of typical (young-onset) disease.

The characteristic telangiectactic blood vessels seen in the conjunctivae of the eye may be helpful in making the diagnosis of ataxia-telangiectasia but may be absent in atypical, late-onset disease.

Other local ophthalmological findings may indicate autoimmune disease.

Seizures

Seizures are seen in approximately 50% of patients with a neuroacanthocytosis syndrome. These can predate the appearance of the movement disorder by several years. Seizures can also be present in young-onset HD, although these patients tend to have an akinetic-rigid phenotype rather than chorea. Younger onset patients with DRPLA tend to present with seizures, although in these cases chorea is less prominent than ataxia. Older onset patients with chorea may develop seizures later in the disease course.

Myoclonus

Myoclonus is a frequent finding in prion diseases, and in younger patients with DRPLA.

Diagnostic tests

Neuroimaging

Neuroimaging should be performed in all patients with undiagnosed chorea. Ideally this should be brain MRI with contrast to exclude a space-occupying lesion, and with sequences sensitive to iron deposition. In addition to tumors, benign or malignant, causative lesions may be vascular, most commonly stroke, but also vasculitis, moya-moya disease, cavernous angioma, or arteriovenous malformation. Multiple sclerosis is a rare cause of chorea.

In the neurodegenerative disorders the head of the caudate nucleus is typically atrophic, and may be interpreted as being consistent with a diagnosis of HD.

Mineral deposition can be seen particularly in the basal ganglia, especially the globus pallidus, probably due to high metabolic demands. CT scan may be necessary to distinguish calcium from iron deposition. "Fahr's disease" refers to the non-specific neuroradiological finding of intra-cranial deposition of calcium, which may be associated with a variety of neurologic features, including chorea, dystonia, parkinsonism. The structural lesion due to calcium deposition in the putamen may be the direct cause of chorea, but this could also be attributable to effects upon neurotransmission. Intra-cranial calcium deposition may be due to a number of different disorders, including those involving calcium and mitochondrial metabolism.

Neurodegeneration with brain iron accumulation (NBIA) refers to several distinct genetic disorders (see accompanying article by Kruer and Hayflick). These include neuroferritinopathy, aceruloplasminemia, and mutations of PLA2G6. The classical MRI finding is the "eye-of-the-tiger", due to basal ganglia iron deposition and central edema, although there may be some variation in the different disorders.

Cases of reversible chorea associated with herniated cervical discs have been reported, although the pathophysiology of chorea originating outside the basal ganglia is obscure.

Serological tests

Sydenham's chorea can be diagnosed by the presence of anti-streptolysin O and anti-DNAse B antibodies (Gilbert,2009). Testing for appropriate autoantibodies should be performed to evaluate for autoimmune diseases including SLE, antiphospholipid antibody syndrome and Sjögren's syndrome.

If indicated, serum and cerebrospinal fluid can be tested for the presence of autoantibodies due to a paraneoplastic syndrome. If these are found, or if there is a high degree of suspicion for a neoplasm, patients should undergo neuroimaging of the thorax, abdomen and pelvis. Sometimes, for example with ovarian teratomas, neoplasms are only detected following exploratory surgery.

The finding of elevated levels of serum liver enzymes raises the suspicion of Wilson's disease (Machado et al., 2006) or a neuroacanthocytosis syndrome (Rampoldi et al., 2002). Elevated creatine kinase is typical of either of the NA syndromes due to myopathy, especially in McLeod syndrome.

In addition to Wilson's disease, markedly reduced ceruloplasmin may be found in aceruloplasminemia. Low ferritin can be indicative of neuroferritinopathy.

Serum alpha-fetoprotein (AFP) may be elevated in ataxia-telangiectasia (AT) and help distinguish this disorder from other childhood-onset ataxias. However, atypical forms have recently been reported, thus this may be a useful screening test for adults with unusual movement disorders.

Hypoalbuminemia and elevated cholesterol can be seen in AOAI. Findings of elevated cholesterol, creatine kinase, and AFP support the diagnosis, although AFP levels are typically lower than those seen in AT (Le Ber et al., 2004; Moreira et al., 2004).

Peripheral blood smear

Acanthocytosis refers to the finding of contracted thorny erythrocytes on peripheral blood smear. The presence of acanthocytes suggests, but is not necessary for the diagnosis of, one of the core neuroacanthocytosis syndromes. Acanthocytes can be found in approximately 10% of cases of PKAN and HDL2. The presence of acanthocytosis may vary over time for reasons which are not understood, and may not be detected even with repeated testing, despite utilization of a sensitive protocol (Storch et al., 2005). In this circumstance the serum enzymes mentioned above may be more informative.

Erythrocyte phenotyping

Erythrocyte antigen phenotyping should be performed if the diagnosis of McLeod syndrome is suspected (Russo et al., 1998). Testing for these antigens requires a panel of anti-Kx and anti-Kell antibodies, and is usually performed at regional blood banks, which should be asked explicitly to exclude McLeod phenotype.

Electroencephalography

EEG may be informative in identifying disorders in which myoclonus and seizures co-occur with chorea. These include prion diseases, DRPLA, and the core neuroacanthocytosis syndromes.

Conclusion

Chorea can be due to a multitude of disorders with a wide variety of pathophysiologies. In addition to metabolic and structural causes, the list of potential investigations continues to grow as more potentially causative genes are discovered. Although treatments for genetic causes are not yet possible, correct diagnosis is essential for appropriate genetic counseling.

References

  • Bowen J, Mitchell T, Pearce R et al. (2000). Chorea in new variant Creutzfeldt-Jacob disease. Mov Disord. 15:1284-1285.
  • Caviness JN, Muenter MD. (1991). An unusual cause of recurrent chorea. Mov Disord. 6:355-357.
  • Curtis AR, Fey C, Morris CM et al. (2001). Mutation in the gene encoding ferritin light polypeptide causes dominant adult-onset basal ganglia disease. Nat.Genet. 28:350-354.
  • Dalmau J, Tuzun E, Wu HY et al. (2007). Paraneoplastic anti-N-methyl-D-aspartate receptor encephalitis associated with ovarian teratoma. Ann.Neurol. 61:25-36.
  • Danek A, Rubio JP, Rampoldi L et al. (2001). McLeod neuroacanthocytosis: genotype and phenotype. Ann Neurol 50:755-764.
    Danek A, Walker RH. (2005). Neuroacanthocytosis. Curr.Opin.Neurol. 18:386-392.
  • Evidente VG, Advincula J, Esteban R et al. (2002). Phenomenology of "Lubag" or X-linked dystonia-parkinsonism. Mov Disord. 17:1271-1277.
  • Gilbert DL. (2009). Acute and chronic chorea in childhood. Semin.Pediatr.Neurol. 16:71-76.
  • Holmes SE, O'Hearn E, Rosenblatt A et al. (2001). A repeat expansion in the gene encoding junctophilin-3 is associated with Huntington disease-like 2. Nat.Genet. 29:377-378.
  • Jung HH, Hergersberg M, Kneifel S et al. (2001). McLeod syndrome: a novel mutation, predominant psychiatric manifestations, and distinct striatal imaging findings. Ann Neurol 49:384-392.
  • Kleiner-Fisman G, Lang AE. (2007). Benign hereditary chorea revisited: A journey to understanding. Mov Disord. 22:2297-2305.
  • Kumar H, Masiowski P, Jog M. (2009). Chorea in the elderly with mutation positive polycythemia vera: a case report. Can.J.Neurol.Sci. 36:370-372.
  • Le Ber I, Bouslam N, Rivaud-Pechoux S et al. (2004). Frequency and phenotypic spectrum of ataxia with oculomotor apraxia 2: a clinical and genetic study in 18 patients. Brain. 127:759-767.
  • Machado A, Fen CH, Mitiko DM et al. (2006). Neurological manifestations in Wilson's disease: Report of 119 cases. Mov Disord. 21:2192-2196.
  • McNeill A, Pandolfo M, Kuhn J et al. (2008). The neurological presentation of ceruloplasmin gene mutations. Eur.Neurol. 60:200-205.
  • Mink JW. (2007). Paroxysmal dyskinesias. Curr.Opin.Pediatr. 19:652-656.
  • Moreira MC, Klur S, Watanabe M et al. (2004). Senataxin, the ortholog of a yeast RNA helicase, is mutant in ataxia-ocular apraxia 2. Nat.Genet. 36:225-227.
  • Rampoldi L, Danek A, Monaco AP. (2002). Clinical features and molecular bases of neuroacanthocytosis. J.Mol.Med. 80:475-491.
  • Russo D, Redman C, Lee S. (1998). Association of XK and Kell blood group proteins. J.Biol.Chem. 273:13950-13956.
  • Schneider SA, van de Warrenburg BP, Hughes TD et al. (2006). Phenotypic homogeneity of the Huntington disease-like presentation in a SCA17 family. Neurology. 67:1701-1703.
  • Storch A, Kornhass M, Schwarz J. (2005). Testing for acanthocytosis - A prospective reader-blinded study in movement disorder patients. J.Neurol. 252:84-90.
  • Suchowersky O, Muthipeedika J. (2005). A case of late-onset chorea. Nat.Clin.Pract.Neurol. 1:113-116.
  • Tsuji, S, (2010) DRPLA. GeneReviews (accessed July 6th 2010)
  • Verhagen MMM, Abdo WF, Willemsen MAAP et al. (2009). Clinical spectrum of ataxia-telangiectasia in adulthood. Neurology 73:430-437.
     
Ruth H. WalkerAbout Dr. Ruth H. Walker

Ruth H. Walker obtained her medical degree from the University of Edinburgh. Scotland, and went on to complete a PhD in basal ganglia neuroanatomy at the University of Edinburgh and MIT (USA). Following a neurology residency at New York University School of Medicine, she completed a fellowship in Movement Disorders at Mount Sinai School of Medicine.

She joined the James J. Peters Veterans' Affairs Medical Center (Bronx) as a staff neurologist and Director of the Movement Disorders Clinic, and is Associate Professor in the Department of Neurology at Mount Sinai School of Medicine, New York.

Dr. Walker's research focuses on the functional neuroanatomy of the basal ganglia and clinicopathologic correlations of neurogenetic disorders. She has a particular interest in rare causes of neurodegenerative chorea, and is the editor of a forthcoming book which comprehensively addresses the diagnostic and therapeutic aspects of this common movement disorder, "The Differential Diagnosis of Chorea" and the organizer of an NIH- and MDS-sponsored meeting entitled "Brain, Blood and Iron: Joint International Symposium on Neuroacanthocytosis and Neurodegeneration with Brain Iron Accumulation." Visit the website www.naadvocacy.org/ for more information. Dr. Walker may be reached by e-mail at ruth.walker@mssm.edu.

***

Visit the MDS E-Store at www.movementdisorders.org/publications/reading_list.php to purchase Dr. Walker's latest books, The Differential Diagnosis of Chorea (Oxford University Press, USA; 1 edition (September 30, 2010) and Neuroacanthocytosis Syndromes II (v. 2) (Springer; 1 edition (January 8, 2008).