Clinical and neuroradiological findings in classic infantile and late-onset globoid-cell leukodystrophy (Krabbe disease)

A neglected neurodegenerative disease: Adult-onset globoid cell leukodystrophy

Globoid cell leukodystrophy (GLD), or Krabbe disease (KD) is a rare neurodegenerative disease, and adult-onset GLD is more even neglected by clinicians. This review provides detailed discussions of the serum enzymes, genes, clinical manifestations, neuroimaging features, and therapies of GLD, with particular emphasis on the characteristics of adult-onset GLD, in an attempt to provide clinicians with in-depth insights into this disease.

Unusual Neuroimaging in a Case of Rapidly Progressive Juvenile-Onset Krabbe Disease

Krabbe disease is a progressive neurologic disorder caused by deficiency of the lysosomal enzyme galactocerebrosidase. The disease commonly has an early-infantile onset, but can have late-infantile, juvenile, or adult-onset phenotypes. Classic computed tomography (CT) and magnetic resonance imaging (MRI) findings in Krabbe have been well described. We report a patient, ultimately diagnosed with juvenile-onset Krabbe, who presented with atypical CT imaging and rapid disease progression. Our patient was a previously healthy and developmentally appropriate female who presented at 3 years 4 months of age with ataxia and motor regression that had progressed over the course of 6 weeks without an identifiable catalyst. CT, performed in the emergency setting, demonstrated extensive white matter hyperdensity. Subsequent MRI showed T2 hyperintensity of the white matter corresponding to the areas of hyperdensity on the CT, as well as enhancement of multiple cranial nerves bilaterally, suggestive of Krabbe disease. Enzymatic testing demonstrated low galactocerebrosidase activity and molecular testing of GALC revealed compound heterozygosity for 2 known pathogenic mutations, consistent with a diagnosis of Krabbe Disease. This included the common 30-kb deletion and a known pathogenic mutation associated with juvenile/adult-onset disease. Our patient's diffuse hyperdensity on CT offers a new radiographic finding to include in the repertoire of Krabbe imaging, and thus aide in the diagnostic evaluation. The rapidity of progression our patient demonstrated is additionally unique and should be considered in the identification of juvenile Krabbe as well as the complicated decision-making process regarding potential treatments.

Adult-onset Krabbe disease due to a homozygous GALC mutation without abnormal signals on an MRI in a consanguineous family: A case report

Background

The most frequent and common form of Krabbe disease (KD) is early‐onset KD in infants, and late‐onset KD has been reported to be a rare disease. In the present study, we reported an adult‐onset KD patient in a consanguineous Chinese family.

Methods

Clinical and radiological data were collected for a family pedigree. The patient was diagnosed with late‐onset KD through next‐generation sequencing. The result was confirmed by Sanger sequencing. GALC enzyme activity was also examined by the colorimetry method. Both the grey matter volume (GMV) and white matter volume values were examined and compared with the average values from ten age‐matched normal controls. Moreover, we reviewed all the available KD studies on PubMed to understand the correlation between the phenotype and genotype of the identified mutation.

Results

The main manifestations of the proband were sudden onset seizures and cognitive decline. Mutation analysis of the GALC revealed a homozygous c.1901T>C mutation in exon 16, which resulted in an amino acid change in p.L634S. Sanger sequencing results showed that the homozygous mutation was inherited from the patient's parents, both of whom were revealed to be heterozygous carriers. Moreover, a decrease in GALC enzyme activity was also detected. However, no abnormal signals were found in the brain MRI. Further structural MRI analysis revealed a significantly decreased GMV in the proband compared to the normal controls. Moreover, it is of interest that all patients with the c.1901T>C mutation had late‐onset KD and were selected from Asian countries, especially Japan and China.

Conclusions

This patient with a homozygous GALC mutation expands the clinical presentation and characteristics of adult‐onset KD, as indicated by grey matter atrophy without abnormal white matter signals.

Survey of quality of life, phenotypic expression, and response to treatment in Krabbe leukodystrophy

OBJECTIVES

To develop a quality of life (QOL) survey for Krabbe disease (KD), and to thereby improve understanding of its phenotypic expression and response to treatment.

METHODS

The survey, the Leukodystrophy Quality of Life Assessment (LQLA) and the Vineland Adaptive Behavior Scales were co-administered to 33 patients or their caretakers. These included the phenotypes of early infantile KD (EIKD; 0-6 months old at onset), late infantile cases (LIKD; 7-12 months old at onset), and cases that emerged after 12 months old, late onset (LOKD). The sample included cases with and without stem cell transplantation (SCT). Reliability and concurrent validity were assessed for overall and subscale scores. Analysis of variance tested differences in QOL between phenotypes and transplant groups (none, pre-, post-symptom).

RESULTS

Good concurrent validity with the Vineland was shown for total, communication, daily activity, social, and motor scales and good reliability was observed. LOKD cases had better communication skills than either EIKD or LIKD and better overall QOL than EIKD. Analyses of individual items showed that communication items, mostly, contributed significantly to phenotype differences. Presymptomatic SCT significantly improved QOL compared to postsymptomatic SCT or no treatment. Presymptomatically treated patients had near-normal total scores.

CONCLUSIONS

The LQLA is valid and reliable. Despite small sample size, phenotypic demarcation was determined to be due mainly to differences in communication skills. There was a relative enhancement of QOL in LOKD patients, and in those who had presymptomatic SCT. These results apply to the current controversy about recommendations for newborn screening for this condition.

Early progression of Krabbe disease in patients with symptom onset between 0 and 5 months

BACKGROUND

Krabbe disease is a rare neurological disorder caused by a deficiency in the lysosomal enzyme, β-galactocerebrosidase, resulting in demyelination of the central and peripheral nervous systems. If left without treatment, Krabbe disease results in progressive neurodegeneration with reduced quality of life and early death. The purpose of this prospective study was to describe the natural progression of early onset Krabbe disease in a large cohort of patients.

METHODS

Patients with early onset Krabbe disease were prospectively evaluated between 1999 and 2018. Data sources included diagnostic testing, parent questionnaires, standardized multidisciplinary neurodevelopmental assessments, and neuroradiological and neurophysiological tests.

RESULTS

We evaluated 88 children with onset between 0 and 5 months. Median age of symptom onset was 4 months; median time to diagnosis after onset was 3 months. The most common initial symptoms were irritability, feeding difficulties, appendicular spasticity, and developmental delay. Other prevalent symptoms included axial hypotonia, abnormal deep tendon reflexes, constipation, abnormal pupillary response, scoliosis, loss of head control, and dysautonomia. Results of nerve conduction studies showed that 100% of patients developed peripheral neuropathy by 6 months of age. Median galactocerebrosidase enzyme activity was 0.05 nmol/h/mg protein. The median survival was 2 years.

CONCLUSIONS

This is the largest prospective natural history study of Krabbe disease. It provides a comprehensive description of the disease during the first 2 years of life. With recent inclusion of state mandated newborn screening programs and promising therapeutic interventions, enhancing our understanding of disease progression in early onset Krabbe disease will be critical for developing treatments, designing clinical trials, and evaluating outcomes.

A clinical review on megalencephaly: A large brain as a possible sign of cerebral impairment

Megalencephaly and macrocephaly present with a head circumference measurement 2 standard deviations above the age-related mean. However, even if pathologic events resulting in both megalencephaly and macrocephaly may coexist, a distinction between these two entities is appropriate, as they represent clinical expression of different disorders with a different approach in clinical work-up, overall prognosis, and treatment. Megalencephaly defines an increased growth of cerebral structures related to dysfunctional anomalies during the various steps of brain development in the neuronal proliferation and/or migration phases or as a consequence of postnatal abnormal events. The disorders associated with megalencephaly are classically defined into 3 groups: idiopathic or benign, metabolic, and anatomic. In this article, we seek to underline the clinical aspect of megalencephaly, emphasizing the main disorders that manifest with this anomaly in an attempt to properly categorize these disorders within the megalencephaly group.

Magnetic resonance imaging findings of central nervous system in lysosomal storage diseases: A pictorial review

Lysosomal storage diseases (LSD) are a complex group of genetic disorders that are a result of inborn errors of metabolism. These errors result in a variety of metabolic dysfunction and build-up certain molecules within the tissues of the central nervous system (CNS). Although, they have discrete enzymatic deficiencies, symptomology and CNS imaging findings can overlap with each other, which can become challenging to radiologists. The purpose of this paper is to review the most common CNS imaging findings in LSD in order to familiarize the radiologist with their imaging findings and help narrow down the differential diagnosis.

Predominant Corticospinal Tract Involvement in a Late Infant with Krabbe Disease

A case of late-infantile Krabbe disease in a patient who presented with developmental regression and spastic quadriplegia in late infancy is reported. Brain magnetic resonance imaging (MRI) at 11 months of age showed predominant corticospinal tract involvement, which usually appears in adult Krabbe disease. Galactocerebrosidase activity in lymphocytes and skin fibroblasts was very low. Genetic testing revealed compound heterozygous mutations of the galactocerebrosidase (GALC) gene, c.635_646 delinsCTC and c.1901T>C [p.L618S], both of which are known pathogenic mutations. It has been reported that the c.1901T>C [p.L618S] mutation is associated with the late-onset phenotype and, in a past case, a homozygous mutation at this location showed predominant corticospinal tract involvement on MRI. Although further analysis is needed to identify the pathophysiological mechanism, this combination of mutations is likely to be associated with this unusual MRI finding in late-infantile Krabbe disease. Because these types of mutations are common for Japanese patients, it is possible that there are more undiagnosed and late-diagnosed patients of late-infantile Krabbe disease who display limited lesions on MRI. Pediatricians should be aware that patients with late-infantile Krabbe disease can present with predominant corticospinal tract involvement on MRI.

Phenotypic variability of Krabbe disease across the lifespan

Krabbe disease (galactocerebrosidase deficiency) is an inherited leukodystrophy that results in severe neurological defects due to altered myelination. Classically, disease onset is within the first year of life. Juvenile and adult-onset cases may have less classic presentations, making diagnosis difficult and often delayed. Here, we review the literature to demonstrate the hetereogeneity of presenting symptoms across all age groups. We also discuss diagnostic approach, emphasizing variation in biochemical, functional, and genetic results among Krabbe phenotypes. Better understanding of the various Krabbe disease phenotypes is critical to facilitate timely diagnosis and appropriate treatment of this clinically heterogeneous disorder.

Variabilité phénotypique dans la maladie de Krabbe au cours de la vie du patient. La maladie de Krabbe (déficit en galactocérébrosidase) est une leukodystrophie héréditaire qui donne lieu à des déficits neurologiques sévères dus à un trouble de la myélinisation. Chez les cas dont la présentation est classique, la maladie débute au cours de la première année de vie. Si la maladie commence chez un adolescent ou un adulte, le mode de présentation peut-ětre moins classique, ce qui rend le diagnostic difficile et souvent tardif. Nous analysons les articles traitant du sujet pour démontrer l'hétérogénéité des symptômes au moment de la première consultation et ceci dans tous les groupes d'âge. Nous discutons également de l'approche diagnostique en mettant l'emphase sur la variation des résultats biochimiques, fonctionnels et génétiques des différents phénotypes dans la maladie de Krabbe. Une meilleure compréhension des différents phénotypes est cruciale pour faciliter un diagnostic précoce et un traitement approprié de cette maladie dont le mode de présentation clinique est hétérogène.

Krabbe Disease in the Arab World

The autosomal recessive inherited Krabbe disease (KD) is a devastating pediatric lysosomal storage disorder affecting white matter of the brain. It is caused by mutations in the gene coding for the lysosomal enzyme galactocerebrosidase. While most patients present with symptoms within the first 6 months of life, others present later in life throughout adulthood. The early infantile form of KD (EIKD) is frequent in the Muslim Arab population in Israel, with a very high prevalence of approximately 1/100 to 1/150 live births. The homozygous variant c.1582G > A (p.D528N) was found to be responsible for EIKD in Palestinian Arab patients. KD was reported in different Arab countries with much lower frequency. While most Arab patients presented with EIKD, late infantile and late onset KD forms were also reported. Most Arab patients presented with variable symptoms ranging from EIKD to late onset KD, with variable clinical findings. Based on literature studies, this review focuses on the clinical and molecular findings of KD patients with Arab ancestry, and highlights the need for developing universal genetic screening programs to overcome the under-reported status of KD prevalence in Arabia. This is expected to improve the prognosis of the disease and promote targeted molecular diagnostics to the Arab patients.

Multipotent stromal cells alleviate inflammation, neuropathology, and symptoms associated with globoid cell leukodystrophy in the twitcher mouse

Globoid cell leukodystrophy (GLD) is a common neurodegenerative lysosomal storage disorder caused by a deficiency in galactocerebrosidase (GALC), an enzyme that cleaves galactocerebroside during myelination. Bone marrow transplantation has shown promise when administered to late-onset GLD patients. However, the side effects (e.g., graft vs. host disease), harsh conditioning regimens (e.g., myelosuppression), and variable therapeutic effects make this an unsuitable option for infantile GLD patients. We previously reported modest improvements in the twitcher mouse model of GLD after intracerebroventricular (ICV) injections of a low-dose of multipotent stromal cells (MSCs). Goals of this study were to improve bone marrow-derived MSC (BMSC) therapy for GLD by increasing the cell dosage and comparing cell type (e.g., transduced vs. native), treatment timing (e.g., single vs. weekly), and administration route (e.g., ICV vs. intraperitoneal [IP]). Neonatal twitcher mice received (a) 2 × 10(5) BMSCs by ICV injection, (b) 1 × 10(6) BMSCs by IP injection, (c) weekly IP injections of 1 × 10(6) BMSCs, or (d) 1 × 10(6) lentiviral-transduced BMSCs overexpressing GALC (GALC-BMSC) by IP injection. All treated mice lived longer than untreated mice. However, the mice receiving peripheral MSC therapy had improved motor function (e.g., hind limb strength and rearing ability), twitching symptoms, and weight compared to both the untreated and ICV-treated mice. Inflammatory cell, globoid cell, and apoptotic cell levels in the sciatic nerves were significantly decreased as a result of the GALC-BMSC or weekly IP injections. The results of this study indicate a promising future for peripheral MSC therapy as a noninvasive, adjunct therapy for patients affected with GLD.

Patterns of magnetic resonance imaging abnormalities in symptomatic patients with Krabbe disease correspond to phenotype

BACKGROUND

Initial magnetic resonance imaging studies of individuals with Krabbe disease were analyzed to determine whether the pattern of abnormalities corresponded to the phenotype.

METHODS

This was a retrospective, nonblinded study. Families/patients diagnosed with Krabbe disease submitted medical records and magnetic resonance imaging discs for central review. Institutional review board approval/informed consents were obtained. Sixty-four magnetic resonance imaging scans were reviewed by two neuroradiologists and a child neurologist according to phenotype: early infantile (onset 0-6 months) = 39 patients; late infantile (onset 7-12 months) = 10 patients; later onset (onset 13 months-10 years) = 11 patients; adolescent (onset 11-20 years) = one patient; and adult (21 years or greater) = three patients. Local interpretations were compared with central review.

RESULTS

Magnetic resonance imaging abnormalities differed among phenotypes. Early infantile patients had a predominance of increased intensity in the dentate/cerebellar white matter as well as changes in the deep cerebral white matter. Later onset patients did not demonstrate involvement in the dentate/cerebellar white matter but had extensive involvement of the deep cerebral white matter, parieto-occipital region, and posterior corpus callosum. Late infantile patients exhibited a mixed pattern; 40% had dentate/cerebellar white matter involvement while all had involvement of the deep cerebral white matter. Adolescent/adult patients demonstrated isolated corticospinal tract involvement. Local and central reviews primarily differed in interpretation of the early infantile phenotype.

CONCLUSION

Analysis of magnetic resonance imaging in a large cohort of symptomatic patients with Krabbe disease demonstrated imaging abnormalities correspond to specific phenotypes. Knowledge of these patterns along with typical clinical signs/symptoms should promote earlier diagnosis and facilitate treatment.

High-throughput screening of stem cell therapy for globoid cell leukodystrophy using automated neurophenotyping of twitcher mice

Globoid cell leukodystrophy (Krabbe's disease) is an autosomal recessive neurodegenerative disorder that results from the deficiency of galactosylceramidase, a lysosomal enzyme involved in active myelination. Due to the progressive, lethal nature of this disease and the limited treatment options available, multiple laboratories are currently exploring novel therapies using the mouse model of globoid cell leukodystrophy. In order to establish a protocol for motor function assessment of the twitcher mouse, this study tested the capability of an automated system to detect phenotypic differences across mouse genotypes and/or treatment groups. The sensitivity of this system as a screening tool for the assessment of therapeutic interventions was determined by the administration of murine bone marrow-derived stem cells into twitcher mice via intraperitoneal injection. Animal behavior was analyzed using the Noldus EthoVision XT7 software. Novel biomarkers, including abnormal locomotion (e.g., velocity, moving duration, distance traveled, turn angle) and observed behaviors (e.g., rearing activity, number of defecation boli), were established for the twitcher mouse. These parameters were monitored across all mouse groups, and the automated system detected improved locomotion in the treated twitcher mice based on the correction of angular velocity, turn angle, moving duration, and exploratory behavior, such as thigmotaxis. Further supporting these findings, the treated mice showed improved lifespan, gait, wire hang ability, twitching severity and frequency, and sciatic nerve histopathology. Taken together, these data demonstrate the utility of computer-based neurophenotyping for motor function assessment of twitcher mice and support its utility for detecting the efficacy of stem cell-based therapy for neurodegenerative disorders.

Later onset phenotypes of Krabbe disease: results of the world-wide registry

The majority of newborns screening positive for Krabbe disease have not exhibited the expected early infantile phenotype, with most clinically normal despite low galactocerebrosidase activity and two mutations. Most are expected to develop the later onset phenotypes. The World-Wide Krabbe Registry was developed in part to expand our understanding of the natural history of these rare variants. As of June 2011, 122 patients were enrolled in the registry: 62% manifested early infantile onset (previously reported), 10% manifested onset at 7-12 months (late infantile), 22% manifested onset at 13 months to 10 years (later onset), and 5% manifested adolescent/adult onset. Data on disease course, galactocerebrosidase activity, DNA mutations, and results of neurodiagnostic studies were obtained from questionnaires and medical records. Initial signs (late infantile) included loss of milestones and poor feeding, whereas later onset and adolescent/adult phenotypes presented with changes in gait. Elevated cerebrospinal fluid protein and abnormal magnetic resonance imaging results were present in most, but not all, patients at diagnosis. Phenotypic variability occurred in four sibships. Five-year and 10-year survivals for all later onset phenotypes were at least 50%. The later onset Krabbe phenotypes differ from those with early infantile disease, but no specific predictor of phenotype was identified.

Metabolic disorders of the brain: part I

Due to nonspecific clinical presentation, diagnosis of metabolic disorders affecting the brain is very challenging for physicians. It is always the constellation of the clinical examination, biochemical assay and imaging that helps in reaching the diagnosis of metabolic disorders. Diagnosis of these disorders or even limiting the differential diagnosis on imaging may pose a formidable challenge to the radiologist. In these two articles (Metabolic Disorders of the Brain: Parts I and II) we have tried to highlight the important clinical and imaging pearls of the major and more commonly encountered metabolic disorders. In the first article we discuss metabolic disorders related to dysfunction of the cellular organelle namely lysosomal, peroxisomal, and mitochondrial. We have also discussed the relevant genetic abnormalities, biochemical findings and application of newer imaging techniques which may aid in diagnosis of these various disorders.

Intracranial calcification in early infantile Krabbe disease: nothing new under the sun

We report the cases of three children, one male and two females, with a diagnosis of early infantile Krabbe disease demonstrating intracranial calcification on computed tomography (CT). The pattern of calcification was similar in all individuals and involved the internal capsule and cerebral white matter. The presence of calcification caused some diagnostic confusion in what was otherwise a typical clinical and radiological presentation. This finding is not new and has previously been described in publications from the 1980s and 1990s reporting the CT and magnetic resonance imaging appearances of Krabbe disease. With increasing use of magnetic resonance as the first imaging modality for investigation of neurological disorders, characteristic CT appearances may be forgotten. This report serves as a reminder that Krabbe disease should be included in the differential diagnosis of disorders causing intracranial calcification.

Early infantile Krabbe disease: results of the World-Wide Krabbe Registry

New York State began screening for Krabbe disease in 2006 to identify infants with Krabbe disease before symptom onset. Because neither galactocerebrosidase activity nor most genotypes reliably predict phenotype, the World Wide Registry was developed to determine whether other clinical/neurodiagnostic data could predict early infantile Krabbe disease in the newborn screening population. Data on disease course, galactocerebrosidase activity, DNA mutations, and initial neurodiagnostic studies in 67 symptomatic children with early infantile Krabbe disease were obtained from parent questionnaires and medical records. Initial signs included crying/irritability, cortical fisting, and poor head control. Galactocerebrosidase activity was uniformly low. Eight of 17 manifested novel mutations. Ninety-two percent (n = 25) exhibited elevated cerebrospinal fluid protein; 76% (n = 42) demonstrated abnormal magnetic resonance images; 67% (n = 15) exhibited abnormal computed tomography findings; 43% (n = 28) produced abnormal electroencephalogram findings; 100% (n = 5) demonstrated abnormal nerve conduction velocities; 83% (n = 6) produced abnormal brainstem evoked responses; and 50% (n = 6) exhibited abnormal visual evoked responses. One, 2, and 3 year survivals were 60%, 26%, and 14%, respectively. Although most symptomatic patients with the early infantile phenotype manifested abnormal cerebrospinal fluid protein, magnetic resonance imaging, brainstem evoked responses, and nerve conduction velocities, studies of affected children may be normal. Other biomarkers are needed to predict phenotype in the newborn screening population.

Normal neuroimaging in early-onset Krabbe disease

Krabbe disease has characteristic findings on brain magnetic resonance imaging (MRI) according to age of clinical onset. MRI-negative Krabbe disease has not been reported in early-onset cases. We present the serial clinical and MRI of brain findings in a case of early-onset Krabbe disease with proven enzyme deficiency. Despite clinical progression, the MRI findings of the child remained normal over a period of 15 months.

Newborn screening for Krabbe disease: the New York State model

Krabbe disease is a rare inherited neurologic disorder affecting the central and peripheral nervous systems. The disease has four phenotypes: early infantile, later onset, adolescent, and adult. The only known treatment is hematopoietic stem cell transplantation, which is, in the early infantile form of the disease, most beneficial if performed before onset of clinical symptoms. In August 2006, New York State began screening all newborns for Krabbe disease. A rapid and accurate technique for assessing galactocerebrosidase activity and performing DNA mutation analysis had been developed. Interpreting these results was limited, however, because neither enzyme activity nor genetic mutation reliably predicts phenotype. A series of initiatives were therefore developed by a multidisciplinary group of neurologists, geneticists, metabolic pediatricians, neurodevelopmental pediatricians, and transplant physicians (the Krabbe Consortium of New York State) to enhance the effectiveness of the newborn screening program. A standardized clinical evaluation protocol was designed based on the available literature, criteria for transplantation for the early infantile phenotype were formulated, a clinical database and registry was developed, and a study of developmental and functional outcomes was instituted. This multidisciplinary standardized approach to evaluating infants who have positive results on newborn screening may serve as a model for other states as they begin the process of screening for Krabbe disease and other lysosomal storage disorders.

The Hunter's Hope Krabbe family database

The objective was to identify presenting signs and symptoms, age at onset of symptoms and diagnosis, and survival in a large population of children with Krabbe disease. In 1997, Hunter's Hope Foundation began collecting clinical data on patients who had been diagnosed with Krabbe disease. As of June 2006, 334 families had returned questionnaires. Deidentified data were analyzed, including country of origin, sex, age at onset of symptoms, symptoms before diagnosis, age at diagnosis, symptoms after diagnosis, initial diagnosis, and survival. Seventy-one percent of patients developed symptoms at 0 to 6 months of age, 19% between 7 and 12 months, and 10% at 13 months + (13 months-5.5 years). The most common initial symptoms for age 0 to 12 months were crying and irritability, stiffness, and seizures. Older children were more likely to present with gait disturbances or loss of milestones. Survival differed according to age at onset of symptoms. Children with the early infantile phenotype (onset 0 to 6 months) had significantly worse survivals than either those with onset at 7 to 12 months or at 13 months to 5.5 years. Given that neither galactocerebrosidase activity nor mutation analysis reliably predict disease severity, the data from this study should help investigators recognize the earliest symptoms of the disease, as well as increase awareness of age of onset and natural history of the various phenotypes.

Cerebral white matter: neuroanatomy, clinical neurology, and neurobehavioral correlates

Lesions of the cerebral white matter (WM) result in focal neurobehavioral syndromes, neuropsychiatric phenomena, and dementia. The cerebral WM contains fiber pathways that convey axons linking cerebral cortical areas with each other and with subcortical structures, facilitating the distributed neural circuits that subserve sensorimotor function, intellect, and emotion. Recent neuroanatomical investigations reveal that these neural circuits are topographically linked by five groupings of fiber tracts emanating from every neocortical area: (1) cortico-cortical association fibers; (2) corticostriatal fibers; (3) commissural fibers; and cortico-subcortical pathways to (4) thalamus and (5) pontocerebellar system, brain stem, and/or spinal cord. Lesions of association fibers prevent communication between cortical areas engaged in different domains of behavior. Lesions of subcortical structures or projection/striatal fibers disrupt the contribution of subcortical nodes to behavior. Disconnection syndromes thus result from lesions of the cerebral cortex, subcortical structures, and WM tracts that link the nodes that make up the distributed circuits. The nature and the severity of the clinical manifestations of WM lesions are determined, in large part, by the location of the pathology: discrete neurological and neuropsychiatric symptoms result from focal WM lesions, whereas cognitive impairment across multiple domains--WM dementia--occurs in the setting of diffuse WM disease. We present a detailed review of the conditions affecting WM that produce these neurobehavioral syndromes, and consider the pathophysiology, clinical effects, and broad significance of the effects of aging and vascular compromise on cerebral WM, in an attempt to help further the understanding, diagnosis, and treatment of these disorders.

Decreased T2 signal in the thalami may be a sign of lysosomal storage disease

INTRODUCTION

Lysosomal disorders are rare and are caused by genetically transmitted lysosomal enzyme deficiencies. A decreased T2 signal in the thalamus has occasionally been reported.

AIMS

Because the finding of bilateral abnormal signal intensity of the thalamus on T2-weighted images has not been systematically reviewed, and its value as a diagnostic tool critically evaluated, we carried out a systematic review of the literature.

METHODS

Articles in English with 30 trios of keywords were collected from PubMed. Exclusion criteria were lack of conventional T2-weighted images in the protocol and not being a human study. Finally, 111 articles were included. The thalamus was considered affected only if mentioned in the text or in the figure legends.

RESULTS

Some 117 patients with various lysosomal diseases and five patients with ceruloplasmin deficiency were reported to have a bilateral decrease in T2 signal intensity. At least one article reported a bilateral decrease in signal intensity of the thalami on T2-weighted images in association with GM1 and GM2 gangliosidosis and with Krabbe's disease, aspartylglucosaminuria, mannosidosis, fucosidosis, and mucolipidosis IV. Furthermore, thalamic alteration was a consistent finding in several types of neuronal ceroid lipofuscinosis (NCL) including CLN1 (infantile NCL), CLN2 (classic late infantile NCL), CLN3 (juvenile NCL), CLN5 (Finnish variant late infantile NCL), and CLN7 (Turkish variant late infantile NCL).

CONCLUSION

A decrease in T2 signal intensity in the thalami seems to be a sign of lysosomal disease.

Design and optimization of lentiviral vectors for transfer of GALC expression in Twitcher brain

BACKGROUND

Demyelination in globoid cell leukodystrophy (GLD) is due to a deficiency of galactocerebrosidase (GALC) activity. Up to now, in vivo brain viral gene transfer of GALC showed modest impact on disease development in Twitcher mice, an animal model for GLD. Lentiviral vectors, which are highly efficient to transfer the expression of therapeutic genes in neurons and glial cells, have not been evaluated for direct cerebral therapy in GLD mice.

METHODS

Lentiviral vectors containing the untagged cDNA or the hemagglutinin (HA)-tagged cDNA for the full-length mouse GALC sequence were generated and validated in vitro. In vivo therapeutic efficacy of these vectors was evaluated by histology, biochemistry and electrophysiology after transduction of ependymal or subependymal layers in young Twitcher pups.

RESULTS

Both GALC lentiviral vectors transduced neurons, oligodendrocytes and astrocytes with efficiencies above 75% and conferred high levels of enzyme activity. GALC accumulated in lysosomes of transduced cells and was also secreted to the extracellular medium. Conditioned GALC medium was able to correct the enzyme deficiency when added to non-transduced Twitcher glial cultures. Mice that received intraventricular injections of GALC vector showed accumulation of GALC in ependymal cells but no diffusion of the enzyme from the ependymal ventricular tree into the cerebral parenchyma. Significant expression of GALC-HA was detected in neuroglioblasts when GALC-HA lentiviral vectors were injected in the subventricular zone of Twitcher mice. Life span and motor conduction in both groups of treated Twitcher mice were not significantly ameliorated.

CONCLUSIONS

Lentiviral vectors showed to be efficient for reconstitution of the GALC expression in Twitcher neural cells. GALC was able to accumulate in lysosomes as well as to enter the secretory pathway of lysosomal enzymes, two fundamental aspects for gene therapy of lysosomal storage diseases. Our in vivo results, while showing the capacity of lentiviral vectors to transfer expression of therapeutic GALC in the Twitcher brain, did not limit progression of disease in Twitchers and highlight the need to evaluate other routes of administration.

Magnetic resonance and diffusion tensor imaging in pediatric white matter diseases

The central nervous system undergoes profound and predictable developmental changes during the first few years of life that provide the structural and functional elements necessary for normal neurological development. The establishment and maturation of white matter pathways is a critical component of the developing nervous system. Diffusion tensor imaging (DTI) offers a noninvasive and quantitative means for the evaluation of white matter changes. DTI has contributed to the evaluation of a number of childhood leukoencephalopathies; it has also been used to follow brain maturation in abnormal states, such as premature birth or early brain injury. Furthermore, it has helped characterize the relation between white matter integrity and cognitive abilities. In the future, DTI is expected to play an increasingly large role in defining developmental abnormalities at an early age and in assessing therapies for pediatric disorders such as leukodystrophies.

Heredofamilial brain calcinosis syndrome

Brain calcinosis syndrome (BCS) usually is defined as bilateral calcium accumulation in the brain parenchyma, primarily in the basal ganglia. More than 50 reported clinical conditions have been associated with BCS. We reviewed clinical, radiological, and genetic features of heredofamilial BCS accompanying all conditions associated with calcium accumulation in the brain reported in English between 1962 and 2003 in MEDLINE. The location, extent, and degree of calcification in the brain show diversity not only among the various disorders but also among patients sharing the same condition. The pathogenesis of BCS is uncertain. More complicated mechanisms may be Involved when brain calcinosis is present but calcium, phosphorus, and parathyroid hormone metabolism abnormalities are absent. We review conditions associated with heredofamilial BCS in which brain calcinosis is nearly uniformly present because such information may be Important to the clinician pursuing an investigative strategy.

Adult onset Krabbe disease may mimic motor neurone disease

Krabbe's disease (galactocerebrosidase deficiency) rarely presents in adults, usually with predominantly upper motor neurone clinical features. We report a case in whom the clinical features were similar to motor neurone disease. Nerve conduction studies and neuroimaging were important in leading to the correct diagnosis. Differences in adult-onset presentations are described.

Evaluation of white matter anisotropy in Krabbe disease with diffusion tensor MR imaging: initial experience

PURPOSE

To compare diffusion tensor magnetic resonance imaging with conventional T2-weighted imaging for evaluation of white matter changes in patients with Krabbe disease.

MATERIALS AND METHODS

In eight patients with Krabbe disease and eight age-matched control subjects, anisotropy maps were generated with diffusion tensor data by using echo-planar imaging with diffusion gradient encoding in six directions. Anisotropy maps and T2-weighted images were visually inspected. Relative anisotropy (RA) and normalized T2-weighted signal intensity in white matter tracts and gray matter nuclei were quantitatively compared between patients and controls (paired Student t test).

RESULTS

Loss of diffusion anisotropy appeared on anisotropy maps as areas of decreased hyperintensity in patients with Krabbe disease. Differences in RA between Krabbe disease patients and control subjects were significant in eight of nine white matter structures studied (P =.001-.01) and in basal ganglia (P =.04). T2-weighted signal intensity was also significantly different in the same white matter structures (P =.006-.049) but not in basal ganglia. In the three patients imaged after stem cell transplantation, mean RA was between the RAs of untreated patients and control subjects.

CONCLUSION

Diffusion tensor-derived anisotropy maps (a) provide a quantitative measure of abnormal white matter in patients with Krabbe disease, (b) are more sensitive than T2-weighted images for detecting white matter abnormality, and (c) may be a marker of treatment response.

Clinical and cerebral FDG PET scan in a patient with Krabbe's disease

A 2-year, 6-month-old Saudi male with infantile Krabbe's disease was studied with fluorine-18-labeled-2-fluoro-2-deoxyglucose positron emission tomography (FDG PET) scan. The patient presented with a gradual loss of developmental milestones, irritability, and crying. At the advanced stage of the disease, he developed tonic-clonic seizures and became a microcephalic, extremely irritable, blind, spastic quadriplegic child, with no deep tendon reflexes. Laboratory studies revealed normal blood chemistry, muscle enzymes, very long chain fatty acids, and acylcarnitines. No abnormal urinary organic acids were detected. The cerebrospinal fluid protein concentration was increased. Magnetic resonance imaging of the brain revealed mild brain atrophy and white matter disease mainly in the centrum semiovale. Electroretinography was normal; however, electroencephalography and visual-evoked potentials were abnormal. Peripheral nerve conduction studies documented a demyelinating neuropathic process. The FDG PET study of the brain demonstrated a marked decrease in the metabolism of the left cerebral cortex and no uptake in the caudate heads. Normal glucose uptake was observed in the thalami, lentiform nuclei, and cerebellum. The patient did not present for subsequent clinic visits and is presumed dead.

MRI nerve root enhancement in Krabbe disease

Krabbe disease is characterized by abnormal breakdown and turnover of myelin, leading to extensive demyelination in both the peripheral and central nervous systems. A 7-month-old infant with early-onset Krabbe disease had deceptively normal head images, but spinal MRI demonstrated abnormal gadolinium enhancement of the lumbosacral sacral nerve roots and cauda equina such as that seen in Guillain-Barré syndrome. Abnormal enhancement in spinal MRI has not been previously described in patients with leukodystrophies.

MRI and electrophysiological abnormalities in a case of canine globoid cell leucodystrophy

A six-month-old West Highland white terrier with progressive, multifocal neurological disease was diagnosed with canine globoid cell leucodystrophy (GCL). Magnetic resonance imaging (MRI) of the brain was performed, as well as electrophysiological testing (including brainstem auditory evoked response, peripheral nerve conduction velocity, repetitive stimulation, F wave analysis and electromyography). MRI findings were consistent with diffuse, symmetrical white matter disease. Electrodiagnostic testing revealed evidence of peripheral neuropathy and an abnormal brainstem auditory evoked response. These observations were consistent with the pathological changes in central and peripheral white matter described for canine GCL, and resembled what has been described in human patients. It is believed that the tests may raise the suspicion of GCL in dogs and may aid in monitoring disease progression.