Cerebral hypoperfusion and hypometabolism with altered striatal signal intensity in chorea-acanthocytosis: a combined PET and MRI study

Novel Imaging Biomarkers for Huntington's Disease and Other Hereditary Choreas

PURPOSE OF THE REVIEW

Imaging biomarkers for neurodegenerative disorders are primarily developed with the goal to aid diagnosis, to monitor disease progression, and to assess the efficacy of disease-modifying therapies in support to clinical outcomes that may either show limited sensitivity or need extended time for their evaluation. This article will review the most recent concepts and findings in the field of neuroimaging applied to Huntington's disease and Huntington-like syndromes. Emphasis will be given to the discussion of potential pharmacodynamic biomarkers for clinical trials in Huntington's disease (HD) and of neuroimaging tools that can be used as diagnostic biomarkers in HD-like syndromes.

RECENT FINDINGS

Several magnetic resonance (MR) and positron emission tomography (PET) molecular imaging tools have been identified as potential pharmacodynamic biomarkers and others are in the pipeline after preclinical validation. MRI and 18F-fluorodeoxyglucose PET can be considered useful supportive diagnostic tools for the differentiation of other HD-like syndromes. New trials in HD have the primary goal to lower mutant huntingtin (mHTT) protein levels in the brain in order to reduce or alter the progression of the disease. MR and PET molecular imaging markers have been developed as tools to monitor disease progression and to evaluate treatment outcomes of disease-modifying trials in HD. These markers could be used alone or in combination for detecting structural and pharmacodynamic changes potentially associated with the lowering of mHTT.

Spinocerebellar Ataxia Type 17 (SCA17)

In 1999, a polyglutamine expansion was identified in the transcription factor TATA-binding protein (TBP) in a patient with ataxia with negative family history. Subsequently, CAG/CAA repeat expansions in the TBP gene were identified in families with spinocerebellar ataxia (SCA), establishing this repeat expansion as the underlying mutation in SCA type 17 (SCA17). There are several characteristic differences between SCA17 and other polyglutamine diseases. First, SCA17 shows a complex and variable clinical phenotype, in some cases overlapping that of Huntington's disease. Second, compared to the other SCA subtypes caused by expanded trinucleotide repeats, anticipation in SCA17 kindreds is rare because of the characteristic structure of the TBP gene. And thirdly, SCA17 patients often have diagnostic problems that may arise from non-penetrance. Because the gap between normal and abnormal repeat numbers is very narrow, it is difficult to determine a cutoff value for pathologic CAG repeat number in SCA17. Herein, we review the clinical, genetic and pathologic features of SCA17.

Functional neuroimaging and chorea: a systematic review

Chorea is a hyperkinetic movement disorder consisting of involuntary irregular, flowing movements of the trunk, neck or face. Although Huntington’s disease is the most common cause of chorea in adults, chorea can also result from many other neurodegenerative, metabolic, and autoimmune conditions. While the pathophysiology of these different conditions is quite variable, recent advances in functional imaging have enabled the development of new methods for analysis of brain activity and neuronal dysfunction. In this paper we review the growing body of functional imaging data that has been performed in chorea syndromes and identify particular trends, which can be used to better understand the underlying network changes within the basal ganglia. While it can be challenging to identify whether changes are primary, secondary, or compensatory, identification of these trends can ultimately be useful in diagnostic testing and treatment in many of the conditions that cause chorea.

Chorea-acanthocytosis in monozygotic twins: clinical findings and neuropathological changes as detected by diffusion tensor imaging, FDG-PET and 123I-β-CIT-SPECT

We report on two 33 years old monozygotic twins with chorea-acanthocytosis (ChAc) misdiagnosed as schizophrenia and Tourette syndrome, respectively. Although the patients shared several clinical similarities, there were also some clear differences: twin 1 presented initially with an acute episode of a paranoid schizophrenia, while twin 2 suffered from generalized epileptic seizures. In both twins, MRI demonstrated caudate nucleus atrophy and an increased apparent diffusion coefficient (ADC) in the striatum bilaterally with right sided predominance. (18)F-FDG PET showed bilaterally reduced glucose utilization in the striatum with clearly pronounced reduction on the right side compared to the left and in twin 1 compared to twin 2. Ratios of binding to striatal dopamine transporters (DAT) and serotonin transporters in the hypothalamus midbrain area as determined using (123)I-beta-CIT-SPECT fell within the normal ranges. However, in twin 1 a significant difference in binding to presynaptic DAT with marked reduction on the right hemisphere was observed. Right hemispheric accentuated changes measured by MRI, FDG-PET, and (123)I-beta-CITSPECT correspond to more severe hyperkinetic movements on the left part of the body in both twins. Different neuro-psychiatric features in this monocygotic twin pair suggest that not only genetic but also environmental factors contribute to the clinical symptomatology. Our findings suggest that the main neuropathological process in ChAc is located in the striatum, involving microstructural alterations, and disturbance of metabolism and dopaminergic neurotransmission.

Chorea-acanthocytosis: A Mimicker of Huntington Disease Case Report and Review of the Literature

BACKGROUND

Neuroacanthocytosis consists of a group of rare heterogeneous neurodegenerative disorders associated with acanthocytosis. Chorea-acanthocytosis, a variety of neuroacanthocytosis, is an autosomal recessive condition with clinical and radiologic features similar to Huntington disease. Although difficult, distinguishing between these entities is crucial as the implications for genetic counseling are significant.

REVIEW SUMMARY

We report the case of a 33-year-old female who presented to our institution with a 3-year history of chorea. The patient's prominent orofacial symptoms and the presence of acanthocytes on peripheral blood smear led to the correct diagnosis of chorea-acanthocytosis.

CONCLUSIONS

The significant similarities between chorea-acanthocytosis and Huntington disease at the clinical and radiologic levels can lead to an initial misdiagnosis. Clinical clues suggestive of chorea-acanthocytosis include prominent orofacial dyskinesias, often causing dysarthria and dysphagia. Acanthocytosis, when present on peripheral blood smear, can confirm the diagnosis.

Spinocerebellar ataxia type 17: extension of phenotype with putaminal rim hyperintensity on magnetic resonance imaging

We report on a 50-year-old woman who presented with an 8-year history of involuntary movements, unsteadiness, and cognitive decline. Examination revealed multidomain cognitive deficits, jerky ocular pursuit movements, hypometric saccades, gaze impersistence, dysarthria, upper limb dystonia, and widespread chorea. TATA-binding protein gene test revealed trinucleotide expansion allele sizes of 47 and 39 repeats, confirming the diagnosis of spinocerebellar ataxia type 17 (SCA-17). Magnetic resonance imaging (MRI) showed marked cerebellar atrophy and putaminal rim hyperintensity. This is the first case of SCA-17 reported to show MRI signal change in the basal ganglia, and extends the phenotypic manifestation of SCA-17.

Neuropsychologische Störungen bei einem monozygoten Zwillingspaar mit Chorea-Akanthozytose

Zusammenfassung: Chorea-Akanthozytose (ChAc) ist eine seltene, genetisch bedingte Erkrankung, welche durch charakteristische neurologische und psychiatrische Symptome gekennzeichnet ist. In der vorliegenden Fallbeschreibung wird ein männliches monozygotes Zwillingspaar vorgestellt, das aufgrund ähnlicher Kombinationen komplexer Bewegungsstörungen (choreatische und parkinsonähnliche Bewegungen), Dystonien und Vokalisationen sowie Verhaltensauffälligkeiten und kognitive Beeinträchtigungen als Tourette-Syndrom fehldiagnostiziert wurde. Eine ausführliche neuropsychologische Untersuchung deutete auf eine fronto-subkortikale Demenz, wobei einige Befunde zwischen den Brüdern diskrepant waren. Die unterschiedlichen Ergebnisse der neurologischen, neuropsychologischen und psychiatrischen Untersuchung lassen annehmen, dass neben genetischen auch nicht-genetische Faktoren die klinische Symptomatik der ChAc Patienten beeinflussen. Darüber hinaus verdeutlicht der Fallbericht, dass eine detaillierte neuropsychologische Untersuchung einen wesentlichen Beitrag zur Diagnosesicherung der ChAc leisten kann.

Chorea-acanthocytosis associated with tourettism

We report on a case of Chorea-acanthocytosis (ChAc) in association with Tourettism that consisted of motor and vocal tics, attention deficit-hyperactivity disorder, and obsessive-compulsive disorder in addition to the typical symptoms of ChAc. The subject was compared with his elder sister who had the same disease but milder clinical profile and neuroradiological findings. The [(18)F]-2-fluoro-2-deoxyglucose positron emission tomography (FDG-PET) findings did not explain the differences in symptomatology between the patient and his sister, although they may have correlated with severity.

Benign hereditary chorea: clinical, genetic, and pathological findings

Benign hereditary chorea is an autosomal dominant disorder presenting with childhood-onset chorea, no dementia, and little or no progression. We present a family with typical clinical features of benign hereditary chorea. Pathological investigation of the brain of an affected family member who died of an unrelated condition showed no significant gross or histological abnormalities. Genetic evaluation showed a novel single nucleotide substitution of intron 2 of the TITF-1 gene (also referred to as TTF, NKX2.1, and T/ebp) on chromosome 14 which is predicted to have drastic consequences on the maturation processes of TITF-1.

The chorea of McLeod syndrome

Among the movement disorders associated with acanthocytosis, McLeod syndrome (McKusick 314850) is the one that is best characterized on the molecular level. Its defining feature is low reactivity of Kell erythrocyte antigens. This is due to absence of membrane protein KX that forms a complex with the Kell protein. KX is coded for by the XK gene on the X-chromosome. We present six males (aged 29 to 60 years), with proven XK mutations, to discuss the chorea associated with McLeod syndrome. The movement disorder commonly develops in the fifth decade and is progressive. It affects the limbs, the trunk and the face. In addition to facial grimacing, involuntary vocalization can be present. In early stages there may only be some restlessness or slight involuntary distal movements of ankles and fingers. Lip-biting and facial tics seem more common in autosomal recessive choreoacanthocytosis linked to chromosome 9. This, together with the absence of dysphagia in McLeod syndrome, may help in differential diagnosis. Recent findings suggest a role for the endothelin system of the striatum in the pathogenesis of McLeod syndrome.

Striatal and pontocerebellar hypoperfusion in Hallervorden-Spatz syndrome

Hallervorden-Spatz syndrome is a group of rare and severe disorders marked by extrapyramidal symptoms and iron accumulation in the globi pallidi, usually visible by magnetic resonance imaging. To assist in determining the functional correlates of these structural abnormalities, positron emission tomography was used to measure regional cerebral blood flows and dopaminergic function in a patient with Hallervorden-Spatz syndrome that manifested as progressive generalized dystonia, optic atrophy, and bilateral pallidal "eye of the tiger" sign. Voxel-by-voxel analysis of positron emission tomography images revealed no pallidal abnormalities but demonstrated significant hypoperfusion of the head of the right caudate nucleus, pons, and cerebellar vermis. Dopaminergic function of the basal ganglia, which was assessed based on visual- analysis of fixation of 18F-labeled fluoro-levodopa, was normal. These data suggest that Hallervorden-Spatz syndrome pathogenesis is not confined to the globi pallidi, and these data also may help to generate new pathogenic hypothesis.

Neuroacanthocytosis masquerading as Huntington's disease: CT/MRI findings

Neuroacanthocytosis (NA) is a rare, degenerative, presumably autosomal-recessive disorder of the nervous system presenting in adulthood and is associated with acanthocytosis of the peripheral blood. The clinical spectrum of NA shares similarities with Huntington's disease (HD), including dyskinetic choreiform movements and degeneration of the caudate nucleus. A woman presented with choreiform movements and was given a presumed diagnosis of HD. Neuroimaging studies were consistent with HD. She lacked the genetic marker for HD, and further evaluation revealed acanthocytosis of the peripheral blood. The case illustrates the similarities and differences in the clinical presentations and neuroimaging studies of these two disease entities, emphasizing the need for a careful clinical evaluation.