Magnetic resonance imaging and spectroscopic changes in brains of patients with cerebrotendinous xanthomatosis

Spectrum of clinical neuroimaging in mitochondrial disorders: a neuroanatomical approach

Mitochondrial disorders are a highly heterogeneous group of genetic diseases that impact pathways associated with the structure and function of the mitochondrion. Clinical presentations of mitochondrial disorders include a wide range of onset, progression, and spectrum of neurological symptoms - ranging from episodic, focal neurological deficits to gradual onset of developmental delays, sensorineural hearing loss, visual impairment, or ataxia. This variability provides clinicians with a diagnostic challenge in identifying suspicion of a mitochondrial disorder and prioritizing specific mitochondrial disorders within their differential. While next-generation sequencing of both the nuclear and mitochondrial genomes has aided identification of mitochondrial disorders, testing results are typically not available for weeks to months, and CSF and biochemical studies indicating possible mitochondrial disorder, such as elevated lactate, are nonspecific in differentiating between mitochondrial disorders and other neurogenetic diseases. Neuroimaging can serve as an early tool to help identify specific mitochondrial disorders; however, there are additional variability and overlap between disorders and other non-mitochondrial diseases. This review provides a framework in narrowing the mitochondrial differential by neuroanatomical localization on neuroimaging studies. We will highlight established neuroimaging patterns associated with mitochondrial disorders, review the role of MRS, and discuss the alternative non-mitochondrial etiologies associated with these findings.

Clinicogenetic characterization of cerebrotendinous xanthomatosis in Brazil

There are few cerebrotendineous xanthomatosis (CTX) case series and observational studies including a significant number of Latin American patients. We describe a multicenter Brazilian cohort of patients with CTX highlighting their clinical phenotype, recurrent variants and assessing possible genotype-phenotype correlations. We analyzed data from all patients with clinical and molecular or biochemical diagnosis of CTX regularly followed at six genetics reference centers in Brazil between March 2020 and August 2023. We evaluated 38 CTX patients from 26 families, originating from 4 different geographical regions in Brazil. Genetic analysis identified 13 variants in the CYP27A1 gene within our population, including 3 variants that had not been previously described. The most frequent initial symptom of CTX in Brazil was cataract (27%), followed by xanthomas (24%), chronic diarrhea (13.5%), and developmental delay (13.5%). We observed that the median age at loss of ambulation correlates with the age of onset of neurological symptoms, with an average interval of 10 years (interquartile range 6.9 to 11 years). This study represents the largest CTX case series ever reported in South America. We describe phenotypic characteristics and report three new pathogenic or likely pathogenic variants.

Frontier and hotspot evolution in cerebrotendinous xanthomatosis: a bibliometric analysis from 1993 to 2023

Background

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive disease associated with lipid metabolic disorders. Because of its clinical diversity and rarity, the diagnosis is often unclear. However, there is still a lack of reports on bibliometric analysis of CTX. The aim of this study was to assess the progress and research developments of CTX over the past three decades, identify emerging trends, and establish novel directions for future research.

Methods

The eligible literature were screened from the Web of Science Core Collection (WoSCC) database. The annual publication, countries, institutions, authors, journals, keywords and references were visually analyzed by Microsoft Excel 2019, CiteSpace 6.2.R4, VOSviewer 1.6.18 and online bibliometrics website (https://bibliometric.com/).

Results

A total of 561 publications from WoSCC were included in this study. The United States is the country with the largest number of publications, and Karolinska Institutet is the institution with the largest number of publications. Björkhem I. ranks as the most published and cited author in the last three decades. Journal of Lipid Research is the most widely published and cited journal. The strongest burst of keywords is "diagnosis."

Conclusion

Unraveling the pathogenesis of CTX and improving its diagnosis and treatment continue to be critical challenges that require urgent attention. Future research endeavors will be centered on enhancing the efficiency and accuracy of early diagnosis and intervention.

Cerebrotendinous xanthomatosis with tremor as the main manifestation: A case report

INTRODUCTION

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive lipid metabolism disorder. It is caused by a defect in the sterol-27-hydroxylase gene, leading to the deposition of cholesteryl and bile alcohol in large amounts, causing a variety of clinical manifestations; however, tremor as the main manifestation of CTX has not been reported.

PATIENTS CONCERNS AND CLINICAL FINDINGS

Herein, we report a 27-year-old woman, who developed head and body tremors at the age of 12 years. Many hospitals misdiagnosed her condition as idiopathic tremor and Parkinson disease, with a poor curative effect.

PRIMARY DIAGNOSIS AND INTERVENTION

We diagnosed her with CTX and treated with chenodeoxycholic acid and clonazepam.

CONCLUSION

The patient's condition considerably improved. This case could help avoid misdiagnosis and mistreatment in clinical practice.

Disorders with prominent posterior fossa involvement

Inherited white matter disorders include a wide range of disorders of various origins with distinct genetic, pathophysiologic, and metabolic backgrounds. Although most of these diseases have nonspecific clinical and radiologic features, some display distinct clinical and/or imaging (magnetic resonance imaging, MRI) characteristics that might suggest the causative gene. Recent advances in genetic testing allow assessing gene panels that include several hundred genes; however, an MRI-based diagnostic approach is important to narrow the choice of candidate genes, particularly in countries where these techniques are not available. Indeed, white matter disorders with prominent posterior fossa involvement present specific MRI (and clinical) phenotypes that can directly orient the diagnosis. This chapter describes the main genetic disorders with posterior fossa involvement and discusses diagnostic strategies.

Cerebrotendinous xanthomatosis without neurological involvement

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessively inherited inborn error of metabolism. Neurological symptoms are considered to be a clinical hallmark of untreated adult patients. We describe a 'milder CTX phenotype', without neurological involvement.

METHODS

We performed a retrospective patient file study in 79 genetically confirmed Dutch patients with CTX (55 patients aged ≥ 21 years) to study the clinical heterogeneity of CTX. We studied the frequency of adult patients with CTX without neurological involvement at diagnosis, in our Dutch cohort, and included a family from South Africa and patients from Italy, USA, Chile and Asia from the literature.

RESULTS

In total, we describe 19 adult patients with CTX from 16 independent families, without neurological symptoms at diagnosis. A relatively small percentage (21%, n = 4) had a history of cataract. The majority, 84% (n = 16), presented with tendon xanthomas as the sole or predominant feature. The majority of patients showed increased plasma cholesterol levels. No correlation was found between this 'milder phenotype', the cholestanol levels and the CYP27A1 genotype. In addition, we describe three novel mutations in the CYP27A1 gene.

CONCLUSIONS

This study shows the clinical heterogeneity of CTX, highlighting the existence of a 'milder phenotype', that is without neurological involvement at diagnosis. Adult patients with CTX may present with tendon xanthomas as the sole or predominant feature, mimicking familial hypercholesterolemia. It is important to realize that the absence of neurological symptoms does not rule out the development of future neurological symptoms. As CTX is a treatable disorder, early diagnosis and initiation of treatment when additional clinical signs occur is therefore essential.

Cerebrotendinous Xanthomatosis: Molecular Pathogenesis, Clinical Spectrum, Diagnosis, and Disease-Modifying Treatments

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive lipid storage disorder caused by mutations in the CYP27A1 gene, which encodes the mitochondrial enzyme sterol 27-hydroxylase. Decreased sterol 27-hydroxylase activity results in impaired bile acid synthesis, leading to reduced production of bile acids, especially chenodeoxycholic acid (CDCA), as well as elevated serum cholestanol and urine bile alcohols. The accumulation of cholestanol and cholesterol mainly in the brain, lenses, and tendons results in the characteristic clinical manifestations of CTX. Clinical presentation is characterized by systemic symptoms including neonatal jaundice or cholestasis, refractory diarrhea, juvenile cataracts, tendon xanthomas, osteoporosis, coronary heart disease, and a broad range of neuropsychiatric manifestations. The combinations of symptoms vary from patient to patient and the presenting symptoms, especially in the early disease phase, may be nonspecific, which leads to a substantial diagnostic delay or underdiagnosis. Replacement of CDCA has been approved as a first-line treatment for CTX, and can lead to biochemical and clinical improvements. However, the effect of CDCA treatment is limited once significant neuropsychiatric manifestations are established. The age at diagnosis and initiation of CDCA treatment correlate with the prognosis of patients with CTX. Therefore, early diagnosis and subsequent treatment initiation are essential.

Double trouble: a case of an ataxic young man with coeliac disease and cerebrotendinous xanthomatosis

We present the case of a 29-year-old south Asian man born of consanguineous marriage, presenting with ataxia, peripheral neuropathy and cognitive impairment. An initial diagnosis of coeliac disease was thought to explain the pertinent clinical features; however, further investigation led to an additional diagnosis of the rare yet treatable autosomal recessive condition, cerebrotendinous xanthomatosis. With both conditions employing highly diverse and overlapping clinical phenotypes, this contributed to a delay in diagnosis. Our report highlights the importance of paying close attention to both the clinical phenotype and family history.

Chinese patient with cerebrotendinous xanthomatosis confirmed by genetic testing: A case report and literature review

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is a treatable autosomal recessive inherited metabolic disorder. It results from a deficiency of sterol 27-hydroxylase (CYP27A1), which is a mitochondrial cytochrome P450 enzyme that catalyzes the hydroxylation of cholesterol and modulates cholesterol homeostasis. Patients with CYP27A1 deficiency show symptoms related to excessive accumulation of cholesterol and cholestanol in lipophilic tissues such as the brain, eyes, tendons, and vessels, resulting in juvenile cataracts, tendon xanthoma, chronic diarrhea, cognitive impairment, ataxia, spastic paraplegia, and peripheral neuropathy. CTX is underdiagnosed as knowledge of the disorder is mainly based on case reports.

CASE SUMMARY

A Chinese family with CTX consisting of one patient and four heterozygous carriers was studied. The patient is a 47-year-old male, who mainly had psychiatric signs but without some cardinal features of CTX such as cataracts, cerebellar ataxia, pyramidal signs and chronic diarrhea. There was a significant increase in the concentration of free fatty acid compared to normal range. Doppler ultrasound of the urinary system showed multiple left kidney stones, a right kidney cyst, and a hypoechoic area in the bladder, which could move with body position. Sagittal and axial magnetic resonance imaging (MRI) of the right ankle joint showed apparent enlargement of the right Achilles tendon and upper medial malleolus flexor tendon, abnormal thickening of the plantar fat, and a small amount of exudation around the fascia in front of the Achilles tendon. Cerebral MRI suggested white matter (WM) demyelination and slight cerebral atrophy. The diagnosis was confirmed by targeted sequencing, which identified compound heterozygous mutations in exon 2 and intron 7 of the CYP27A1 gene (c.435G>T, c.1263+1G>A). Treatment for 3 wk with a combination of lipid-lowering and antipsychotic therapy improved his psychiatric symptoms and normalized the levels of serum free fatty acid. Sediments in the bladder disappeared after therapy.

CONCLUSION

CYP27A1 genetic analysis should be the definitive method for CTX diagnosis. This case suggests that urinary system diseases may be neglected in CTX patients. The clinical, biological, radiological, and genetic characteristics of CTX are summarized to promote early diagnosis and treatment of this disease.

The "crab sign": an imaging feature of spinocerebellar ataxia type 48

PURPOSE

A new form of autosomal dominant hereditary spinocerebellar ataxia (SCA) has been recently described (SCA48), and here we investigate its conventional MRI findings to identify the presence of a possible imaging feature of this condition.

METHODS

In this retrospective observational study, we evaluated conventional MRI scans from 10 SCA48 patients (M/F = 5/5; 44.7 ± 7.8 years). For all subjects, atrophy of both supratentorial and infratentorial compartments were recorded, as well as the presence of possible T2-weighted imaging (T2WI) signal alterations.

RESULTS

In SCA48 patients, no meaningful supratentorial changes were found, both in terms of volume loss or MRI signal changes. Atrophy of the cerebellum was present in all cases, involving both the vermis and the hemispheres, but particularly affecting the postero-lateral portions of the cerebellar hemispheres. In all patients, with the exception of only one subject (90.0% of the cases), a T2WI hyperintensity of both dentate nuclei was found. The association of such signal alteration with the pattern of cerebellar atrophy resembled the appearance of a crab ("crab sign").

CONCLUSION

Our findings suggest that SCA48 patients are characterized by cerebellar atrophy, mainly involving the postero-lateral hemisphere areas, along with a T2WI hyperintensity of dentate nuclei. We propose that the association of such signal change, along with the atrophy of the lateral portion of the cerebellar hemispheres, resembled the appearance of a crab, and therefore, we propose the "crab sign" as a neuroradiological sign present in SCA48 patients.

A clinical diagnostic algorithm for early onset cerebellar ataxia

Early onset cerebellar Ataxia (EOAc) comprises a large group of rare heterogeneous disorders. Determination of the underlying etiology can be difficult given the broad differential diagnosis and the complexity of the genotype-phenotype relationships. This may change the diagnostic work-up into a time-consuming, costly and not always rewarding task. In this overview, the Childhood Ataxia and Cerebellar Group of the European Pediatric Neurology Society (CACG-EPNS) presents a diagnostic algorithm for EOAc patients. In seven consecutive steps, the algorithm leads the clinician through the diagnostic process, including EOA identification, application of the Inventory of Non-Ataxic Signs (INAS), consideration of the family history, neuro-imaging, laboratory investigations, genetic testing by array CGH and Next Generation Sequencing (NGS). In children with EOAc, this algorithm is intended to contribute to the diagnostic process and to allow uniform data entry in EOAc databases.

Optic Neuropathy with Features Suggestive of Optic Neuritis in Cerebrotendinous Xanthomatosis

We describe our encounter with a 39-year-old man who exhibited acute painless visual loss and progressive gait disturbance. He had tendinous xanthoma and several neuroophthalmological findings indicative of optic neuropathy in the right eye, including afferent pupillary defect, cecocentral scotoma, and optic disc swelling. Neurological examination showed cerebellar ataxia and pyramidal weakness. Brain magnetic resonance imaging revealed bilateral swelling in the optic nerves with gadolinium-enhancement suggesting optic neuritis, an enlarged fourth ventricle, atrophy of the cerebellum, and hyperintensities in the bilateral dentate nuclei. The patient was diagnosed with cerebrotendinous xanthomatosis (CTX) based on an elevated serum cholestanol level and a homozygous missense mutation in CYP27A1. CTX is a genetic lipid storage disease caused by dysfunction of the mitochondrial enzyme sterol 27-hydroxylase. With respect to ophthalmological manifestations, juvenile cataracts and optic neuropathy are common findings in patients with CTX, but there have been no reports of optic neuropathy with features suggestive of optic neuritis. Thus, this case illustrates that clinicians should consider a diagnosis of CTX in patients with cardinal features of CTX even if the patients show signs indicative of optic neuritis.

Neuroimaging in Hereditary Spastic Paraplegias: Current Use and Future Perspectives

Hereditary spastic paraplegias (HSP) are a large group of genetic diseases characterized by progressive degeneration of the long tracts of the spinal cord, namely the corticospinal tracts and dorsal columns. Genotypic and phenotypic heterogeneity is a hallmark of this group of diseases, which makes proper diagnosis and management often challenging. In this scenario, magnetic resonance imaging (MRI) emerges as a valuable tool to assist in the exclusion of mimicking disorders and in the detailed phenotypic characterization. Some neuroradiological signs have been reported in specific subtypes of HSP and are therefore helpful to guide genetic testing/interpretation. In addition, advanced MRI techniques enable detection of subtle structural abnormalities not visible on routine scans in the spinal cord and brain of subjects with HSP. In particular, quantitative spinal cord morphometry and diffusion tensor imaging look promising tools to uncover the pathophysiology and to track progression of these diseases. In the current review article, we discuss the current use and future perspectives of MRI in the context of HSP.

Conventional MRI

Conventional magnetic resonance imaging (MRI) allows for a detailed noninvasive visualization/examination of posterior fossa structures and represents a fundamental step in the diagnostic workup of many cerebellar disorders. In the first part of this chapter methodologic issues, like the correct choice of hardware (magnets, coils), pro and cons of the different MRI sequences, and patient management during the examination are discussed. In the second part, the MRI anatomy of the cerebellum, as noted on the various conventional MRI sequences, as well as a detailed description of cerebellar maturational processes from birth to childhood and into adulthood, are reported. Volumetric studies on the cerebellar growth based on three-dimensional MRI sequences are also presented. Moreover, we briefly discuss two main topics regarding conventional MRI of the cerebellum that have generated some debate in recent years: the differentiation between cerebellar atrophy, hypoplasia, and pontocerebellar hypoplasia, and signal changes of dentate nuclei after repetitive gadolinium-based contrast injections. The advantages and benefits of advanced neuroimaging techniques, including ¹H magnetic resonance spectroscopy, diffusion-weighted imaging, diffusion tensor imaging, and perfusion-weighted imaging are discussed in the last section of the chapter.

Brain diffusion tensor imaging changes in cerebrotendinous xanthomatosis reversed with treatment

Cerebrotendinous xanthomatosis (CTX, MIM 213700) is a rare autosomal recessive lipid storage disorder caused by CYP27A1 mutations. Treatment with chenodeoxycholic acid (CDCA) may slow the progression of the disease and reverse some symptoms in a proportion of patients. In a non-consanguineous Caucasian family, two siblings with CTX were evaluated before treatment and prospectively followed-up every 6 months after starting CDCA therapy, using systematic clinical examination, neuropsychological tests, laboratory tests, electroencephalography (EEG) and brain MRI, diffusion tensor imaging (DTI) and tractography. A 30-year-old patient and her 27-year-old brother were referred for progressive spastic paraparesis. Both had epilepsy, learning difficulties, chronic diarrhoea and juvenile-onset cataracts. CTX was diagnosed by increased cholestanol levels and compound heterozygosity for CYP27A1 mutations. Therapy with CDCA led to resolution of chronic diarrhoea, normalisation of serum cholestanol and EEG, and a progressive improvement in gait, cognition and seizure control. Before treatment, conventional brain MRI showed no CTX-related abnormalities for the proband and no cerebellar abnormalities for the brother, while DTI showed reduced fractional anisotropy (FA) and tract-density in the cerebellum and widespread cerebral reductions of FA in both patients, compared to a group of 35 healthy controls. Repeated DTI after starting therapy showed progressive increases of cerebellar tract density and of cerebral FA. In patients with CTX, therapy with CDCA may lead to significant clinical improvement, with normalisation of biochemical and electrophysiological biomarkers. DTI and tractography may detect changes when the conventional MRI is unremarkable and may provide potential neuroimaging biomarkers for monitoring treatment response in CTX, while the conventional MRI remains unchanged.

Brain diffusion tensor imaging changes in cerebrotendinous xanthomatosis reversed with treatment

Cerebrotendinous xanthomatosis (CTX, MIM 213700) is a rare autosomal recessive lipid storage disorder caused by CYP27A1 mutations. Treatment with chenodeoxycholic acid (CDCA) may slow the progression of the disease and reverse some symptoms in a proportion of patients. In a non-consanguineous Caucasian family, two siblings with CTX were evaluated before treatment and prospectively followed-up every 6 months after starting CDCA therapy, using systematic clinical examination, neuropsychological tests, laboratory tests, electroencephalography (EEG) and brain MRI, diffusion tensor imaging (DTI) and tractography. A 30-year-old patient and her 27-year-old brother were referred for progressive spastic paraparesis. Both had epilepsy, learning difficulties, chronic diarrhoea and juvenile-onset cataracts. CTX was diagnosed by increased cholestanol levels and compound heterozygosity for CYP27A1 mutations. Therapy with CDCA led to resolution of chronic diarrhoea, normalisation of serum cholestanol and EEG, and a progressive improvement in gait, cognition and seizure control. Before treatment, conventional brain MRI showed no CTX-related abnormalities for the proband and no cerebellar abnormalities for the brother, while DTI showed reduced fractional anisotropy (FA) and tract-density in the cerebellum and widespread cerebral reductions of FA in both patients, compared to a group of 35 healthy controls. Repeated DTI after starting therapy showed progressive increases of cerebellar tract density and of cerebral FA. In patients with CTX, therapy with CDCA may lead to significant clinical improvement, with normalisation of biochemical and electrophysiological biomarkers. DTI and tractography may detect changes when the conventional MRI is unremarkable and may provide potential neuroimaging biomarkers for monitoring treatment response in CTX, while the conventional MRI remains unchanged.

Epidemiology, diagnosis, and treatment of cerebrotendinous xanthomatosis (CTX)

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive disorder of bile acid synthesis caused by mutations in the cytochrome P450 CYP27A1 gene that result in production of a defective sterol 27-hydroxylase enzyme. CTX is associated with abnormally high levels of cholestanol in the blood and accumulation of cholestanol and cholesterol in the brain, tendon xanthomas, and bile. Hallmark clinical manifestations of CTX include chronic diarrhea, bilateral cataracts, tendon xanthomas, and neurologic dysfunction. Although CTX is a rare disorder, it is thought to be underdiagnosed, as presenting signs and symptoms may be nonspecific with significant overlap with other more common conditions. There is marked variability in signs and symptoms, severity, and age of onset between patients. The disease course is progressive and potentially debilitating or fatal, particularly with respect to neurologic presentations that can include intellectual disability, autism, behavioral and psychiatric problems, and dementia, among others. Treatment with chenodeoxycholic acid (CDCA; chenodiol) is the current standard of care. CDCA can help restore normal sterol, bile acid, bile alcohol, and cholestanol levels. CDCA also appears to be generally effective in preventing adverse clinical manifestations of the disease from occurring or progressing if administered early enough. Improved screening and awareness of the condition may help facilitate early diagnosis and treatment.

Peripheral neuropathy in complex inherited diseases: an approach to diagnosis

Peripheral neuropathy is a common finding in patients with complex inherited neurological diseases and may be subclinical or a major component of the phenotype. This review aims to provide a clinical approach to the diagnosis of this complex group of patients by addressing key questions including the predominant neurological syndrome associated with the neuropathy, for example, spasticity, the type of neuropathy and the other neurological and non-neurological features of the syndrome. Priority is given to the diagnosis of treatable conditions. Using this approach, we associated neuropathy with one of three major syndromic categories: (1) ataxia, (2) spasticity and (3) global neurodevelopmental impairment. Syndromes that do not fall easily into one of these three categories can be grouped according to the predominant system involved in addition to the neuropathy, for example, cardiomyopathy and neuropathy. We also include a separate category of complex inherited relapsing neuropathy syndromes, some of which may mimic Guillain-Barré syndrome, as many will have a metabolic aetiology and be potentially treatable.

The spectrum of magnetic resonance findings in cerebrotendinous xanthomatosis: redefinition and evidence of new markers of disease progression

Cerebrotendinous xanthomatosis (CTX) is a metabolic disease characterized by systemic signs and neurological impairment, which can be prevented if chenodeoxycholic acid (CDCA) treatment is started early. Despite brain MRI represents an essential diagnostic tool, the spectrum of findings is worth to be reappraised, and follow-up data are needed. We performed clinical evaluation and brain MRI in 38 CTX patients. Sixteen of them who were untreated at baseline examination underwent clinical and MRI follow-up after long-term treatment with CDCA. Brain MRI abnormalities included cortical and cerebellar atrophy, and T2W/FLAIR hyperintensity involving subcortical, periventricular, and cerebellar white matter, the brainstem and the dentate nuclei. Regarding the dentate nuclei, we also observed T1W/FLAIR hypointensity consistent with cerebellar vacuolation and T1W/FLAIR/SW hypointense alterations compatibly with calcification in a subgroup of patients. Long-term follow-up showed that clinical and neuroradiological stability or progression were almost invariably associated. In patients with cerebellar vacuolation at baseline, a worsening over time was observed, while subjects lacking vacuoles were clinically and neuroradiologically stable at follow-up. The brains of CTX patients very often show both supratentorial and infratentorial abnormalities at MRI, the latter being related to clinical disability and including a wide spectrum of dentate nuclei alterations. The presence of cerebellar vacuolation may be regarded as a useful biomarker of disease progression and unsatisfactory response to therapy. On the other hand, the absence of dentate nuclei signal alteration should be considered an indicator of better prognosis.

The spectrum of magnetic resonance findings in cerebrotendinous xanthomatosis: redefinition and evidence of new markers of disease progression

Cerebrotendinous xanthomatosis (CTX) is a metabolic disease characterized by systemic signs and neurological impairment, which can be prevented if chenodeoxycholic acid (CDCA) treatment is started early. Despite brain MRI represents an essential diagnostic tool, the spectrum of findings is worth to be reappraised, and follow-up data are needed. We performed clinical evaluation and brain MRI in 38 CTX patients. Sixteen of them who were untreated at baseline examination underwent clinical and MRI follow-up after long-term treatment with CDCA. Brain MRI abnormalities included cortical and cerebellar atrophy, and T2W/FLAIR hyperintensity involving subcortical, periventricular, and cerebellar white matter, the brainstem and the dentate nuclei. Regarding the dentate nuclei, we also observed T1W/FLAIR hypointensity consistent with cerebellar vacuolation and T1W/FLAIR/SW hypointense alterations compatibly with calcification in a subgroup of patients. Long-term follow-up showed that clinical and neuroradiological stability or progression were almost invariably associated. In patients with cerebellar vacuolation at baseline, a worsening over time was observed, while subjects lacking vacuoles were clinically and neuroradiologically stable at follow-up. The brains of CTX patients very often show both supratentorial and infratentorial abnormalities at MRI, the latter being related to clinical disability and including a wide spectrum of dentate nuclei alterations. The presence of cerebellar vacuolation may be regarded as a useful biomarker of disease progression and unsatisfactory response to therapy. On the other hand, the absence of dentate nuclei signal alteration should be considered an indicator of better prognosis.

Pathophysiology of cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal-recessive lipid storage disease caused by mutations in the CYP27A1 gene, which lead to deficiency of the mitochondrial enzyme, sterol 27-hydroxylase, resulting in the accumulation of cholestanol in the serum and many affected lesions. To date, more than 50 different CYP27A1 mutations, including missense mutations, frameshifts, and splice site mutations, have been reported worldwide in patients with CTX. Clinical presentation is characterized by neonatal jaundice or cholestasis, refractory diarrhea, juvenile cataracts, tendon xanthomas, osteoporosis, coronary heart disease, and progressive neuropsychiatric disturbances; however, combinations of symptoms vary from patient to patient. Neuropsychiatric abnormalities include mental retardation or dementia, psychiatric symptoms, cerebellar signs, pyramidal signs, progressive myelopathy, peripheral neuropathy, extrapyramidal manifestations, and seizures. Replacement treatment with chenodeoxycholic acid in the early stage of the disease has been reported to improve or even prevent clinical symptoms of CTX. After significant neurological pathology is established, the effect of the treatment is limited and the deterioration of clinical manifestations may continue; therefore, early diagnosis of CTX is crucial.

Inherited or acquired metabolic disorders

This chapter starts with a description of imaging of inherited metabolic disorders, followed by a discussion on imaging of acquired toxic-metabolic disorders of the adult brain. Neuroimaging is crucial for the diagnosis and management of a number of inherited metabolic disorders. Among these, inherited white-matter disorders commonly affect both the nervous system and endocrine organs. Magnetic resonance imaging (MRI) has enabled new classifications of these disorders that have greatly enhanced both our diagnostic ability and our understanding of these complex disorders. Beyond the classic leukodystrophies, we are increasingly recognizing new hereditary leukoencephalopathies such as the hypomyelinating disorders. Conventional imaging can be unrevealing in some metabolic disorders, but proton magnetic resonance spectroscopy (MRS) may be able to directly visualize the metabolic abnormality in certain disorders. Hence, neuroimaging can enhance our understanding of pathogenesis, even in the absence of a pathologic specimen. This review aims to present pathognomonic brain MRI lesion patterns, the diagnostic capacity of proton MRS, and information from clinical and laboratory testing that can aid diagnosis. We demonstrate that applying an advanced neuroimaging approach enhances current diagnostics and management. Additional information on inherited and metabolic disorders of the brain can be found in Chapter 63 in the second volume of this series.

Evaluation of cholesterol metabolism in cerebrotendinous xanthomatosis

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is a treatable bile acid disorder caused by mutations of CYP27A1. The pathogenesis of neurological damage has not been completely explained. Oral chenodeoxycholic acid (CDCA) can lead to clinical stabilization, but in a subgroup of patients the disease progresses despite treatment. In the present study, we aimed at clarifying cholesterol metabolism abnormalities and their response to CDCA treatment, in order to identify reliable diagnostic and prognostic markers and understand if differences exist between stable patients and those with neurological progression.

METHODS

We enrolled 19 untreated CTX patients and assessed serum profile of bile acids intermediates, oxysterols, cholesterol, lathosterol, and plant sterols. Then we performed a long-term follow up during CDCA therapy, and compared biochemical data with neurological outcome.

RESULTS

We observed increase of cholestanol, 7α-hydroxy-4-cholesten-3-one (7αC4), lathosterol, and plant sterols, whereas 27-hydroxycholesterol (27-OHC) was extremely low or absent. CDCA treatment at a daily dose of 750 mg normalized all biochemical parameters except for 7αC4 which persisted slightly higher than normal in most patients, and 27-OHC which was not modified by therapy. Biochemical evaluation did not reveal significant differences between stable and worsening patients.

DISCUSSION

Cholestanol and 7αC4 represent important markers for CTX diagnosis and monitoring of therapy. Treatment with CDCA should aim at normalizing serum 7αC4 as well as cholestanol, since 7αC4 better mirrors 7α-hydroxylation rate and is thought to be correlated with cholestanol accumulation in the brain. Assessment of serum 27-OHC is a very good tool for biochemical diagnosis at any stage of disease. Lathosterol and plant sterols should be considered as additional markers for diagnosis and monitoring of therapy. Further studies including long-term assessment of bile acid intermediates in cerebrospinal fluid are needed in patients who show clinical progression despite treatment.

Consensus paper: radiological biomarkers of cerebellar diseases

Hereditary and sporadic cerebellar ataxias represent a vast and still growing group of diseases whose diagnosis and differentiation cannot only rely on clinical evaluation. Brain imaging including magnetic resonance (MR) and nuclear medicine techniques allows for characterization of structural and functional abnormalities underlying symptomatic ataxias. These methods thus constitute a potential source of radiological biomarkers, which could be used to identify these diseases and differentiate subgroups of them, and to assess their severity and their evolution. Such biomarkers mainly comprise qualitative and quantitative data obtained from MR including proton spectroscopy, diffusion imaging, tractography, voxel-based morphometry, functional imaging during task execution or in a resting state, and from SPETC and PET with several radiotracers. In the current article, we aim to illustrate briefly some applications of these neuroimaging tools to evaluation of cerebellar disorders such as inherited cerebellar ataxia, fetal developmental malformations, and immune-mediated cerebellar diseases and of neurodegenerative or early-developing diseases, such as dementia and autism in which cerebellar involvement is an emerging feature. Although these radiological biomarkers appear promising and helpful to better understand ataxia-related anatomical and physiological impairments, to date, very few of them have turned out to be specific for a given ataxia with atrophy of the cerebellar system being the main and the most usual alteration being observed. Consequently, much remains to be done to establish sensitivity, specificity, and reproducibility of available MR and nuclear medicine features as diagnostic, progression and surrogate biomarkers in clinical routine.

A practical approach to diseases affecting dentate nuclei

A wide variety of diseases affect the dentate nuclei. When faced with the radiological demonstration of signal changes in the dentate nuclei, radiologists and clinical neurologists have to sieve through the many possibilities, which they do not encounter on a regular basis. This task can be challenging, and therefore, developing a clinical, radiological, and laboratory approach is important. Information on the topic is scattered and the subject has not yet been reviewed. In this review, a combined clinicoradiological approach is presented. The signal changes in T1, T2, fluid-attenuated inversion recovery (FLAIR), diffusion, susceptibility weighted, and gadolinium-enhanced images can give specific or highly suggestive patterns, which are illustrated. The role of computed tomography (CT) in the diagnostic process is discussed. Specific radiological patterns do not exist in a significant proportion of patients where the clinical and laboratory analysis becomes important. In this review, we group the clinical constellations to narrow down the differential diagnosis and highlight the diagnostic clinical signs, such as tendon xanthomas and Kayser-Fleischer rings. As will be seen, a number of these conditions are potentially reversible, and hence, their early diagnosis is desirable. Finally, key diagnostic tests and available therapies are outlined. The practical approach thus begins with the radiologist and winds its way through the clinician, towards carefully selected diagnostic tests defining the therapy options.

Differential diagnosis of Mendelian and mitochondrial disorders in patients with suspected multiple sclerosis

Several single gene disorders share clinical and radiologic characteristics with multiple sclerosis and have the potential to be overlooked in the differential diagnostic evaluation of both adult and paediatric patients with multiple sclerosis. This group includes lysosomal storage disorders, various mitochondrial diseases, other neurometabolic disorders, and several other miscellaneous disorders. Recognition of a single-gene disorder as causal for a patient's 'multiple sclerosis-like' phenotype is critically important for accurate direction of patient management, and evokes broader genetic counselling implications for affected families. Here we review single gene disorders that have the potential to mimic multiple sclerosis, provide an overview of clinical and investigational characteristics of each disorder, and present guidelines for when clinicians should suspect an underlying heritable disorder that requires diagnostic confirmation in a patient with a definite or probable diagnosis of multiple sclerosis.

Cerebrotendinous xanthomatosis: a comprehensive review of pathogenesis, clinical manifestations, diagnosis, and management

Cerebrotendinous xanthomatosis (CTX) OMIM#213700 is a rare autosomal-recessive lipid storage disease caused by mutations in the CYP27A1 gene; this gene codes for the mitochondrial enzyme sterol 27-hydroxylase, which is involved in bile acid synthesis. The CYP27A1 gene is located on chromosome 2q33-qter and contains nine exons. A CYP27A1 mutation leads to decreased synthesis of bile acid, excess production of cholestanol, and consequent accumulation of cholestanol in tissues. Currently there is no consensus on the prevalence of CTX, one estimate being <5/100,000 worldwide. The prevalence of CTX due to the CYP27A1 mutation R362C alone is approximately 1/50,000 in Caucasians. Patients with CTX have an average age of 35 years at the time of diagnosis and a diagnostic delay of 16 years. Clinical signs and symptoms include adult-onset progressive neurological dysfunction (i.e., ataxia, dystonia, dementia, epilepsy, psychiatric disorders,peripheral neuropathy, and myopathy) and premature non-neurologic manifestations (i.e., tendon xanthomas, childhood-onset cataracts, infantile-onset diarrhea, premature atherosclerosis, osteoporosis, and respiratory insufficiency). Juvenile cataracts, progressive neurologic dysfunction, and mild pulmonary insufficiency are unique symptoms that distinguish CTX from other lipid storage disorders including familial dysbetalipoproteinemia, homozygous familial hypercholesterolemia, and sitosterolemia, all of which might also present with xanthomas and cardiovascular diseases. Brain magnetic resonance imaging (MRI) shows bilateral lesions in the dentate nucleus of the cerebellum and mild white matter lesions. The classical symptoms and signs, namely elevated levels of cholestanol and bile alcohols in serum and urine, brain MRI, and the mutation in the CYP27A1 gene confirm the diagnosis of CTX. Early diagnosis and long-term treatment with chenodeoxycholic acid (750 mg/d) improve neurological symptoms and contribute to a better prognosis.

A suspicion index for early diagnosis and treatment of cerebrotendinous xanthomatosis

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive lipid storage disorder characterized by a heterogeneous presentation and a broad spectrum of clinical manifestations. Since early diagnosis and replacement therapy with chenodeoxycholic acid can prevent clinical deterioration, our aim was to develop a diagnostic tool to identify and treat CTX patients at an initial stage of the disease.

METHODS

We devised a suspicion index, composed of weighted scores assigned to indicators such as family history characteristics and common systemic and neurological features, on the basis of a pooled analysis of selected international CTX series. The indicators were classified as very strong (score 100), strong (50) or moderate (25). The suspicion index was then applied retrospectively to our CTX population.

RESULTS

Early systemic signs such as cataract, diarrhea and neonatal cholestatic jaundice were considered strong indicators, together with neurological features such as intellectual impairment, psychiatric disturbances, ataxia, spastic paraparesis and dentate nuclei abnormalities at MRI. Tendon xanthomas were regarded as very strong indicators, as was an affected sibling. A total score ≥ 100 warranted serum cholestanol assessment. Elevated cholestanol or a total score ≥ 200, with one very strong or four strong indicators, warranted CYP27A1 gene analysis. In our patients, age at diagnosis was 35.5 ± 11.8 years (mean ± standard deviation), whereas with the diagnostic tool it became 10.6 ± 9.8 years (p < 0.01).

CONCLUSIONS

Our suspicion index provides a simple and inexpensive diagnostic tool allowing diagnosis and treatment of CTX before neurological disability occurs.

[Cerebrotendinous xanthomatosis: a multicentric retrospective study of 15 adults, clinical and paraclinical typical and atypical aspects]

INTRODUCTION

Cerebrotendinous xanthomatosis, a metabolic leukodystrophy with an autosomal recessive inheritance, is secondary to deficiency of sterol 27-hydroxylase, an enzyme involved in cholesterol catabolism. Classical symptoms include clinical or infraclinical xanthomas affecting the skin and tendons, early cataracts, neurological signs and diarrhea. Brain imaging reveals involvement of the dentate nuclei and periventricular white matter hyperintensities. The diagnosis is based on an increased cholestanol level in serum, confirmed by the presence of a mutation in the CYP27A1 gene. Treatment is based on chenodeoxycholic acid.

METHOD

We report a retrospective multicentric study of 15 cases of cerebrotendinous xanthomatosis diagnosed in French adults. Clinical, molecular and MRI findings were recorded in all patients.

RESULTS

The average age at diagnosis was 39years (range 27-65). Disease onset occurred in childhood in 73% of patients and in adulthood in 27%. All patients with a pediatric onset were diagnosed during adulthood (age range 28-65years). Clinical symptoms variably associated cerebellar syndrome, pyramidal syndrome, cognitive decline, epilepsy, neuropathy (sought in 10 of our patients, present in forms in 8), psychiatric disorders, cataract and xanthomas. One patient had an atypical presentation: monoparesis associated with xanthomas. Brain MRI was abnormal in all: findings consisted in T2-weighted hyperintensity of the dentate nuclei (47%), periventricular leuoencephalopathy (73%) which preferentially involved the posterior cerebral part (60%), leucoencephalopathy with a vascular pattern (7%), hyperintensity of the cortico-spinal tracts (53%), globi pallidi, corpus callosum and cerebral atrophy (33%). Serum cholestanol was elevated in 93% of patients. The most frequent mutation was 1183C>T (n=5/15). Under treatment with chenodeoxycholic acid, eight patients improved initially, followed by stabilization in five of them, and worsening in the others. Four patients died.

CONCLUSION

Patients with the xanthoma-neurological disorder association should be tested for cerebrotendinous xanthomatosis. The disease often begins in childhood with a diagnostic delay but also in adulthood. Involvement of the dentate nuclei is specific but not sensitive and the supratentorial leucoencephalopathy is not specific but with an antero-posterior gradient. A vascular distribution and involvement of the corpus callosum are possible. Serum cholestanol assay is very reliable: an elevated level provides the diagnosis, which must nevertheless be confirmed by molecular biology.

Neuroimaging of lipid storage disorders

Lipid storage diseases, also known as the lipidoses, are a group of inherited metabolic disorders in which there is lipid accumulation in various cell types, including the central nervous system, because of the deficiency of a variety of enzymes. Over time, excessive storage can cause permanent cellular and tissue damage. The brain is particularly sensitive to lipid storage as the contents of the central nervous system must occupy uniform volume, and any increases in fluids or deposits will lead to pressure changes and interference with normal neurological function. In addition to primary lipid storage diseases, lysosomal storage diseases include the mucolipidoses (in which excessive amounts of lipids and carbohydrates are stored in the cells and tissues) and the mucopolysaccharidoses (in which abnormal glycosylated proteins cannot be broken down because of enzyme deficiency). Neurological dysfunction can be a manifestation of these conditions due to substrate deposition as well. This review will explore the modalities of neuroimaging that may have particular relevance to the study of the lipid storage disorder and their impact on elucidating aspects of brain function. First, the techniques will be reviewed. Next, the neuropathology of a few selected lipid storage disorders will be reviewed and the use of neuroimaging to define disease characteristics discussed in further detail. Examples of studies using these techniques will be discussed in the text.

Clinical course of two Italian siblings with ataxia-telangiectasia-like disorder

Ataxia-telangiectasia-like disorder (ATLD) due to mutations in the MRE11 gene is a very rare autosomal recessive disease, described so far in only 20 patients. Little is known about the onset of the first symptoms or the clinical course of the disease. The present report contributes to the diagnosis of ATLD and its prognosis at onset. We report 30 years of clinical and ophthalmic observations and the results of quantitative magnetic resonance (MR), MR spectroscopy (proton magnetic resonance spectroscopic imaging) and neuropsychological assessment in the first Italian siblings identified with ATLD. Although the disease had early onset and the clinical picture was initially severe, suggesting ataxia-telangiectasia, neurological impairment, ocular motor apraxia and neuropsychological tests showed very slow deterioration in adult age. The patients developed eye and head motor strategies to compensate ocular motor apraxia. MR measurements and MR spectroscopy disclosed widespread neuronal and axonal involvement. ATLD should be considered in patients with ocular apraxia and ataxia in infancy. The long follow-up provided insights into clinical outcome, with functional neuroimaging studies shedding light on the pathogenetic mechanisms of this rare disease.

Clinical and radiological findings of a cerebrotendinous xanthomatosis patient with a novel p.A335V mutation in the CYP27A1 gene

We herein describe the case of a Japanese cerebrotendinous xanthomatosis (CTX) patient with a novel CYP27A1 gene mutation. The patient had been diagnosed with cataracts at 25 years of age and subsequently developed neurological symptoms in his forties, being referred to our hospital at 47 years of age. Upon admission, Achilles tendon xanthomas, cognitive impairment, dysphagia, dysarthria, dystonia, spasticity, muscle weakness and ataxia were observed. Brain MRI revealed abnormal signals in the dentate nuclei, periventricular white matter and pyramidal tract, and the serum cholestanol level was elevated. A CYP27A1 gene analysis identified compound heterozygosity for p.A335V, a novel mutation, and p.R405Q, a previously reported mutation. Making an early diagnosis of CTX is crucial, as the administration of chenodeoxycholic acid reverses metabolic derangement.

Young-onset dementia

Young-onset dementia is a neurologic syndrome that affects behavior and cognition of patients younger than 65 years of age. Although frequently misdiagnosed, a systematic approach, reliant upon attainment of a detailed medical history, a collateral history, neuropsychological testing, laboratory studies, and neuroimaging, may facilitate earlier and more accurate diagnosis with subsequent intervention. The differential diagnosis of young-onset dementia is extensive and includes early-onset forms of adult neurodegenerative conditions including Alzheimer's disease, vascular dementia, frontotemporal dementia, Lewy body dementias, Huntington's disease, and prion disease. Late-onset forms of childhood neurodegenerative conditions may also present as young-onset dementia and include mitochondrial disorders, lysosomal storage disorders, and leukodystrophies. Potentially reversible etiologies including inflammatory disorders, infectious diseases, toxic/metabolic abnormalities, transient epileptic amnesia, obstructive sleep apnea, and normal pressure hydrocephalus also represent important differential diagnostic considerations in young-onset dementia. This review will present etiologies, diagnostic strategies, and options for management of young-onset dementia with comprehensive summary tables for clinical reference.

Psychiatric manifestations in cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX) is a rare and severe, but treatable, inborn disorder of bile acid biosynthesis and sterol storage with autosomal recessive inheritance and variable clinical presentation. CTX treatment consists of chenodeoxycholic acid and must be started as early as possible to prevent permanent disability. Psychiatric manifestations are rare and non-specific, and often lead to significant diagnostic and treatment delay. Therefore, better recognition of the gamut of psychiatric manifestations in CTX can diminish the risk of misdiagnosis and irreversible neurological deterioration. We hereby describe the psychiatric features in CTX. A complete review of all published cases of CTX in the medical literature was undertaken and the case reports with psychiatric presentation were collected and analyzed. We also describe the psychiatric features in relation to the neurological semeiology in six patients with CTX diagnosed at the La Salpêtrière Hospital. We conclude that psychiatric manifestations in CTX follow a bimodal/bitemporal pattern, appearing early in the disease course in the form of a behavioral/personality disorder associated with learning difficulties or mental retardation, or manifesting in advanced disease in the setting of dementia as rich neuropsychiatric syndromes, such as frontal, orbitofrontal or frontotemporal syndromes of cortico-subcortical dementia encompassing behavioral/personality disturbance, affective/mood disorders or psychotic disorders. Behavioral/personality disturbance in childhood or adolescence, especially when accompanied by learning difficulties, should therefore lead to further investigation to exclude CTX, as early diagnosis and treatment is critical for prognosis.

The neuropsychiatry of inborn errors of metabolism

A number of metabolic disorders that affect the central nervous system can present in childhood, adolescence or adulthood as a phenocopy of a major psychiatric syndrome such as psychosis, depression, anxiety or mania. An understanding and awareness of secondary syndromes in metabolic disorders is of great importance as it can lead to the early diagnosis of such disorders. Many of these metabolic disorders are progressive and may have illness-modifying treatments available. Earlier diagnosis may prevent or delay damage to the central nervous system and allow for the institution of appropriate treatment and family and genetic counselling. Metabolic disorders appear to result in neuropsychiatric illness either through disruption of late neurodevelopmental processes (metachromatic leukodystrophy, adrenoleukodystrophy, GM2 gangliosidosis, Niemann-Pick type C, cerebrotendinous xanthomatosis, neuronal ceroid lipofuscinosis, and alpha mannosidosis) or via chronic or acute disruption of excitatory/inhibitory or monoaminergic neurotransmitter systems (acute intermittent porphyria, maple syrup urine disease, urea cycle disorders, phenylketonuria and disorders of homocysteine metabolism). In this manuscript we review the evidence for neuropsychiatric illness in major metabolic disorders and discuss the possible models for how these disorders result in psychiatric symptoms. Treatment considerations are discussed, including treatment resistance, the increased propensity for side-effects and the possibility of some treatments worsening the underlying disorder.

Inherited cerebellar ataxia in childhood: a pattern-recognition approach using brain MRI

Ataxia is the principal symptom of many common neurologic diseases in childhood. Ataxias caused by dysfunction of the cerebellum occur in acute, intermittent, and progressive disorders. Most of the chronic progressive processes are secondary to degenerative and metabolic diseases. In addition, congenital malformation of the midbrain and hindbrain can also be present, with posterior fossa symptoms related to ataxia. Brain MR imaging is the most accurate imaging technique to investigate these patients, and imaging abnormalities include size, shape, and/or signal of the brain stem and/or cerebellum. Supratentorial and cord lesions are also common. This review will discuss a pattern-recognition approach to inherited cerebellar ataxia in childhood. The purpose is to provide a comprehensive discussion that ultimately could help neuroradiologists better manage this important topic in pediatric neurology.

Polyneuropathy in cerebrotendinous xanthomatosis and response to treatment with chenodeoxycholic acid

Polyneuropathy has been reported in cerebrotendinous xanthomatosis (CTX), although its nature and possible association with certain genotypes and phenotypes are unclear. The effect of chronic administration of chenodeoxycholic acid (CDCA) on peripheral nerve conduction parameters is still debated. We report clinical, laboratory, and electrophysiological findings in 35 CTX patients. Twenty-six subjects (74.2 %) showed peripheral nerve abnormalities. Polyneuropathy was predominantly axonal (76.9 % of patients) and generally mild. No correlation was found between its presence and clinical or biochemical data. In polyneuropathic patients, CDCA treatment improved electrophysiological conduction parameters, irrespective of the duration of therapy. Improvement mainly concerned nerve conduction velocities, whereas most nerve amplitudes remained unchanged. This means that CDCA treatment did not influence the number of axons activated by maximum electrical stimulation but increased the conduction of the still-excitable fibers. Our findings may suggest that CDCA treatment promotes myelin synthesis in nerve fibers with residual unaffected axons. The effect of therapy may therefore depend largely on the extent of irreversible structural damage to axons.

Polyneuropathy in cerebrotendinous xanthomatosis and response to treatment with chenodeoxycholic acid

Polyneuropathy has been reported in cerebrotendinous xanthomatosis (CTX), although its nature and possible association with certain genotypes and phenotypes are unclear. The effect of chronic administration of chenodeoxycholic acid (CDCA) on peripheral nerve conduction parameters is still debated. We report clinical, laboratory, and electrophysiological findings in 35 CTX patients. Twenty-six subjects (74.2 %) showed peripheral nerve abnormalities. Polyneuropathy was predominantly axonal (76.9 % of patients) and generally mild. No correlation was found between its presence and clinical or biochemical data. In polyneuropathic patients, CDCA treatment improved electrophysiological conduction parameters, irrespective of the duration of therapy. Improvement mainly concerned nerve conduction velocities, whereas most nerve amplitudes remained unchanged. This means that CDCA treatment did not influence the number of axons activated by maximum electrical stimulation but increased the conduction of the still-excitable fibers. Our findings may suggest that CDCA treatment promotes myelin synthesis in nerve fibers with residual unaffected axons. The effect of therapy may therefore depend largely on the extent of irreversible structural damage to axons.

Direct visualization of cerebellar nuclei in patients with focal cerebellar lesions and its application for lesion-symptom mapping

As yet, human cerebellar lesion studies have not taken advantage of direct magnetic resonance imaging (MRI) of the cerebellar nuclei in individual patients. In the present study, susceptibility weighted imaging (SWI) was used to visualize lesions of the dentate nuclei in patients with chronic focal lesions. Fifteen patients with cerebellar lesions either due to stroke or tumor surgery underwent SWI imaging using a 1.5T MRI scanner. Dentate nuclei were seen as hypointensities in all patients. Three of the patients underwent additional SWI imaging at 3T and 7T. Compared to 1.5T, corrugation of the dentate wall was seen with greater precision and the dorsal, iron-poorer part was seen more fully. Lesion-symptom mapping was performed based on the 1.5T MR images. Patients were divided into two groups with and without upper limb ataxia. A region-of-interest-(ROI)-driven normalization technique was used which had initially been developed by Diedrichsen et al. (2011) for functional MRI (fMRI) of the dentate nuclei. Compared to conventional normalization of the cerebellum, overlap of dentate lesions improved and lead to increased sensitivity of lesion-symptom maps. Subtraction analysis revealed that the more dorsal and rostral parts of the dentate nuclei were related to upper limb ataxia. Findings were in good accordance with the dentate hand area shown in recent fMRI studies. These data provide evidence that direct identification of dentate lesions together with the ROI-driven normalization technique allows for improved lesion-symptom mapping at the level of the cerebellar nuclei already at conventional 1.5T MRI field strength.

Cerebrotendinous xanthomatosis: a rare cause of spinocerebellar syndrome

A 34-year-old patient demonstrating pyramidal and cerebellar signs, accompanied by epilepsy, peripheral neuropathy, mental retardation and bilateral cataract was diagnosed with cerebrotendinous xanthomatosis based on the clinical picture, magnetic resonance imaging of the brain and serum sterol analysis. Tendon xanthomas were not observed in this case. After establishing the diagnosis, treatment with chenodeoxycholic acid and statin was introduced. During the next two years of the follow-up, serum cholestanol and 7α-hydroxycholesterol levels decreased in response to the therapy, but this was not reflected in the patient's neurological condition, which was slowly progressing. Treatment effectiveness in cerebrotendinous xanthomatosis is variable, notably better in patients who had started therapy before the injury to the nervous system took place. The present case report points to cerebrotendinous xanthomatosis as a rare cause of spinocerebellar syndrome, which might be treatable if diagnosed in early life.