Alexander disease: Ventricular garlands and abnormalities of the medulla and spinal cord

Longitudinally extensive transverse myelitis

PURPOSE OF REVIEW

Longitudinally extensive transverse myelitis (LETM) is a frequently devastating clinical syndrome which has come into focus for its association with neuromyelitis optica (NMO). Recent advances in the diagnosis of NMO have led to very sensitive and specific tests and advances in therapy for this disorder. LETM is not pathognomonic of NMO, therefore it is important to investigate for other causes of myelopathy in these patients. This review aims to discuss recent advances in NMO diagnosis and treatment, and to discuss the differential diagnosis in patients presenting with LETM.

RECENT FINDINGS

Fluorescence-activated cell sorting and cell binding assays for NMO-IgG are the most sensitive for detecting NMO spectrum disorders. Patients who have a clinical presentation of NMO, who have been tested with older ELISA or immunofluorescence assay and been found to be negative, should be retested with a fluorescence-activated cell sorting assay when available, particularly in the presence of recurrent LETM. Novel therapeutic strategies for LETM in the context of NMO include eculizumab, which could be considered in patients with active disease who have failed azathioprine and rituximab. Thorough investigation of patients with LETM who are negative for NMO-IgG may lead to an alternate cause for myelopathy.

SUMMARY

LETM is a heterogeneous condition. Novel treatment strategies are available for NMO, but other causes need to be excluded in NMO-IgG-seronegative patients.

Inherited leukoencephalopathies with clinical onset in middle and old age

The currently widespread use of neuroimaging has led neurologists to often face the problem of the differential diagnosis of white matter diseases. There are various forms of leukoencephalopathies (vascular, inflammatory and immunomediated, infectious, metabolic, neoplastic) and sometimes white matter lesions are expression of a genetic disease. While many inherited leukoencephalopathies fall in the child neurologist's interest, others may have a delayed or even a typical onset in the middle or old age. This field is rapidly growing and, in the last few years, many new inherited white matter diseases have been described and genetically defined. A non-delayed recognition of middle and old age inherited leukoencephalopathies appears important to avoid unnecessary tests and therapies in the patient and to possibly anticipate the diagnosis in relatives. The aim of this review is to provide a guide to direct the diagnostic process when facing a patient with a suspicion of an inherited form of leukoencephalopathy and with clinical onset in middle or old age. Based on a MEDLINE search from 1990 to 2013, we identified 24 middle and old age onset inherited leukoencephalopathies and reviewed in this relation the most recent findings focusing on their differential diagnosis. We provide summary tables to use as a check list of clinical and neuroimaging findings that are most commonly associated with these forms of leukoencephalopathies. When present, we reported specific characteristics of single diseases. Several genetic diseases may be suspected in patients with middle or old age and white matter abnormalities. In only few instances, pathognomonic clinical or associated neuroimaging features help identifying a specific disease. Therefore, a comprehensive knowledge of the characteristics of these inherited white matter diseases appears important to improve the diagnostic work-up, optimize the choice of genetic tests, increase the number of diagnosed patients, and stimulate the research interest in this field.

Imaging manifestations of the leukodystrophies, inherited disorders of white matter

The leukodystrophies are a diverse set of inherited white matter disorders and are uncommonly encountered by radiologists in everyday practice. As a result, it is challenging to recognize these disorders and to provide a useful differential for the referring physician. In this article, leukodystrophies are reviewed from the perspective of 4 imaging patterns: global myelination delay, periventricular/deep white matter predominant, subcortical white matter predominant, and mixed white/gray matter involvement patterns. Special emphasis is placed on pattern recognition and unusual combinations of findings that may suggest a specific diagnosis.

Identification of a novel nonsense mutation in the rod domain of GFAP that is associated with Alexander disease

Alexander disease (AxD) is an astrogliopathy that primarily affects the white matter of the central nervous system (CNS). AxD is caused by mutations in a gene encoding GFAP (glial fibrillary acidic protein). The GFAP mutations in AxD have been reported to act in a gain-of-function manner partly because the identified mutations generate practically full-length GFAP. We found a novel nonsense mutation (c.1000 G>T, p.(Glu312Ter); also termed p.(E312*)) within a rod domain of GFAP in a 67-year-old Korean man with a history of memory impairment and leukoencephalopathy. This mutation, GFAP p.(E312*), removes part of the 2B rod domain and the whole tail domain from the GFAP. We characterized GFAP p.(E312*) using western blotting, in vitro assembly and sedimentation assay, and transient transfection of human adrenal cortex carcinoma SW13 (Vim(+)) cells with plasmids encoding GFAP p.(E312*). The GFAP p.(E312*) protein, either alone or in combination with wild-type GFAP, elicited self-aggregation. In addition, the assembled GFAP p.(E312*) aggregated into paracrystal-like structures, and GFAP p.(E312*) elicited more GFAP aggregation than wild-type GFAP in the human adrenal cortex carcinoma SW13 (Vim(+)) cells. Our findings are the first report, to the best of our knowledge, on this novel nonsense mutation of GFAP that is associated with AxD and paracrystal formation.

Magnetic resonance imaging and genetic investigation of a case of Rottweiler leukoencephalomyelopathy

Background

Leukoencephalomyelopathy is an inherited neurodegenerative disorder that affects the white matter of the spinal cord and brain and is known to occur in the Rottweiler breed. Due to the lack of a genetic test for this disorder, post mortem neuropathological examinations are required to confirm the diagnosis. Leukoencephalopathy with brain stem and spinal cord involvement and elevated lactate levels is a rare, autosomal recessive disorder in humans that was recently described to have clinical features and magnetic resonance imaging (MRI) findings that are similar to the histopathologic lesions that define leukoencephalomyelopathy in Rottweilers. Leukoencephalopathy with brain stem and spinal cord involvement is caused by mutations in the DARS2 gene, which encodes a mitochondrial aspartyl-tRNA synthetase. The objective of this case report is to present the results of MRI and candidate gene analysis of a case of Rottweiler leukoencephalomyelopathy to investigate the hypothesis that leukoencephalomyelopathy in Rottweilers could serve as an animal model of human leukoencephalopathy with brain stem and spinal cord involvement.

Case presentation

A two-and-a-half-year-old male purebred Rottweiler was evaluated for generalised progressive ataxia with hypermetria that was most evident in the thoracic limbs. MRI (T2-weighted) demonstrated well-circumscribed hyperintense signals within both lateral funiculi that extended from the level of the first to the sixth cervical vertebral body. A neurodegenerative disorder was suspected based on the progressive clinical course and MRI findings, and Rottweiler leukoencephalomyelopathy was subsequently confirmed via histopathology. The DARS2 gene was investigated as a causative candidate, but a sequence analysis failed to identify any disease-associated variants in the DNA sequence.

Conclusion

It was concluded that MRI may aid in the pre-mortem diagnosis of suspected cases of leukoencephalomyelopathy. Genes other than DARS2 may be involved in Rottweiler leukoencephalomyelopathy and may also be relevant in human leukoencephalopathy with brain stem and spinal cord involvement.

ASTROCYTES: EMERGING STARS IN LEUKODYSTROPHY PATHOGENESIS

Astrocytes are the predominant glial cell population in the central nervous system (CNS). Once considered only passive scaffolding elements, astrocytes are now recognised as cells playing essential roles in CNS development and function. They control extracellular water and ion homeostasis, provide substrates for energy metabolism, and regulate neurogenesis, myelination and synaptic transmission. Due to these multiple activities astrocytes have been implicated in almost all brain pathologies, contributing to various aspects of disease initiation, progression and resolution. Evidence is emerging that astrocyte dysfunction can be the direct cause of neurodegeneration, as shown in Alexander's disease where myelin degeneration is caused by mutations in the gene encoding the astrocyte-specific cytoskeleton protein glial fibrillary acidic protein. Recent studies point to a primary role for astrocytes in the pathogenesis of other genetic leukodystrophies such as megalencephalic leukoencephalopathy with subcortical cysts and vanishing white matter disease. The aim of this review is to summarize current knowledge of the pathophysiological role of astrocytes focusing on their contribution to the development of the above mentioned leukodystrophies and on new perspectives for the treatment of neurological disorders.

A case of adult-onset alexander disease featuring severe atrophy of the medulla oblongata and upper cervical cord on magnetic resonance imaging

Adult-onset Alexander disease (AOAD) has been increasingly recognized since the identification of the glial fibrillary acidic protein gene mutation in 2001. We report on a 56-year-old man who was genetically confirmed as AOAD with the glial fibrillary acidic protein mutation of p.M74T. He developed spastic tetraparesis, sensory disturbances in four limbs, and mild cognitive impairment without apparent dysarthria and dysphagia. The case was characterized by severe atrophy of the medulla oblongata and upper cervical cord with intramedullary signal intensity changes on magnetic resonance imaging. While AOAD is diverse in clinical presentation, the peculiar magnetic resonance imaging findings of marked atrophy of the medulla oblongata and cervical cord are thought to be highly suggestive of the diagnosis of AOAD.

A novel adult case of juvenile-onset Alexander disease: complete remission of neurological symptoms for over 12 years, despite insidiously progressive cervicomedullary atrophy

We present here a 25-year-old woman with genetically confirmed (p.R276L mutation in the GFAP gene) juvenile-onset AxD. Episodic vomiting appeared at age nine, causing anorexia and insufficient growth. Brain MRI at age 11 showed a small nodular lesion with contrast enhancement in the left dorsal portion of the cervicomedullary junction. Her episodic vomiting improved spontaneously at age 13, and she became neurologically asymptomatic. The enhancement of the lesion disappeared simultaneously, although the plaque remained. Longitudinal MRI observations, however, revealed insidiously progressive cervicomedullary atrophy without a signal change. This case broadens our knowledge of AxD: (1) molecular analysis of the GFAP gene is warranted in patients with MRI evidence of tumor-like lesions in the brainstem, particularly if they present with isolated episodic vomiting and/or anorexia; (2) the disease can be self-remitting for at least 12 years; (3) cervicomedullary atrophy, characteristic of the adult form, can be insidiously progressive without a signal change before the clinical symptoms appear.

Glial fibrillary acidic protein mutations in adult-onset Alexander disease: clinical features observed in 12 Japanese patients

OBJECTIVE

To clarify the clinical manifestations of adult-onset Alexander disease (AOAD) in Japanese patients with glial fibrillary acidic protein (GFAP) gene mutations.

METHODS AND MATERIALS

  Twelve patients of AOAD with GFAP mutations detected in our centre were examined for neurological and magnetic resonance imaging (MRI) findings.

RESULTS

  Major symptoms were pyramidal and bulbar signs. In addition, three patients presented abnormal behaviour and/or memory disturbance. Two of the three patients also had Parkinsonism and had been diagnosed with fronto-temporal dementia or progressive supranuclear palsy until GFAP mutations were detected. Abnormalities of the medulla oblongata and cervical spinal cord were observed on MRI in all patients.

CONCLUSIONS

  Patients presenting with pyramidal and/or bulbar signs with abnormalities of the medulla oblongata and cervical spinal cord on MRI should be considered for GFAP analysis as this is the typical presentation of AOAD. Abnormal behaviour and cognitive disorders including deterioration of memory were rare symptoms but could be an obstacle to diagnosing Alexander disease.

Alexander disease causing mutations in the C-terminal domain of GFAP are deleterious both to assembly and network formation with the potential to both activate caspase 3 and decrease cell viability

Alexander disease is a primary genetic disorder of astrocyte caused by dominant mutations in the astrocyte-specific intermediate filament glial fibrillary acidic protein (GFAP). While most of the disease-causing mutations described to date have been found in the conserved α-helical rod domain, some mutations are found in the C-terminal non-α-helical tail domain. Here, we compare five different mutations (N386I, S393I, S398F, S398Y and D417M14X) located in the C-terminal domain of GFAP on filament assembly properties in vitro and in transiently transfected cultured cells. All the mutations disrupted in vitro filament assembly. The mutations also affected the solubility and promoted filament aggregation of GFAP in transiently transfected MCF7, SW13 and U343MG cells. This correlated with the activation of the p38 stress-activated protein kinase and an increased association with the small heat shock protein (sHSP) chaperone, αB-crystallin. Of the mutants studied, D417M14X GFAP caused the most significant effects both upon filament assembly in vitro and in transiently transfected cells. This mutant also caused extensive filament aggregation coinciding with the sequestration of αB-crystallin and HSP27 as well as inhibition of the proteosome and activation of p38 kinase. Associated with these changes were an activation of caspase 3 and a significant decrease in astrocyte viability. We conclude that some mutations in the C-terminus of GFAP correlate with caspase 3 cleavage and the loss of cell viability, suggesting that these could be contributory factors in the development of Alexander disease.

Nationwide survey of Alexander disease in Japan and proposed new guidelines for diagnosis

Alexander disease (AxD) is a rare neurodegenerative disorder characterized by white matter degeneration and formation of cytoplasmic inclusions. Glial fibrillary acidic protein (GFAP) mutations have been reported in various forms of AxD since 2001. However, a definitive diagnosis remains difficult because of uncertain prevalence, and different clinical features seen in infantile AxD and adult AxD may lead to confusion and misdiagnosis. Here we report an epidemiological study conducted in Japan. Two nationwide questionnaire-based surveys were conducted using tentative diagnostic criteria. We gathered information regarding prevalence, neurological findings, magnetic resonance imaging (MRI) findings, electrophysiological findings, genetic information, and the results of therapeutic interventions and home care. Prevalence of various forms of AxD was determined as 27.3% (infantile), 24.2% (juvenile), and 48.5% (adult). Prevalence of AxD in Japan was estimated to be approximately 1 case per 2.7 million individuals. The main characteristics of infantile and juvenile AxD include delayed psychomotor development or mental retardation, convulsions, macrocephaly, and predominant cerebral white matter abnormalities in the frontal lobe on brain MRI. The main characteristics of adult AxD include bulbar signs, muscle weakness with hyperreflexia, and signal abnormalities and/or atrophy of medulla oblongata and cervical spinal cord on MRI. To ensure correct diagnosis of AxD, the physician should understand the importance of the process of GFAP genetic testing, which provides definitive diagnosis. Therefore, we propose new clinical guidelines for diagnosing AxD based on simplified classifications: cerebral AxD (type 1), bulbospinal AxD (type 2), and intermediate form (type 3).

Alexander disease with periventricular calcification: a novel mutation of the GFAP gene

Alexander disease is a rare neurodegenerative leucoencephalopathy caused by de novo mutations in the GFAP gene. Infantile, juvenile, and adult subtypes have been described and the clinical and radiological phenotypes are broad. Here we report on a single case of juvenile-onset Alexander disease associated with a novel frameshift mutation in the GFAP gene. The 8-year-old male patient had a relatively mild clinical phenotype characterized by dystonia, intermittent episodes of raised intracranial pressure, and characteristic radiological changes. He also presented with the additional and to our knowledge previously unreported, neuroimaging finding of periventricular calcification. We postulate that in children with leucoencephalopathy and periventricular calcification of undetermined aetiology, the diagnosis of Alexander disease should be considered. If the magnetic resonance imaging findings are compatible with Alexander disease, then DNA analysis of the GFAP gene should be performed even if the full criteria for a neuroradiological diagnosis are not met.

[Metabolic disorders with typical alterations in MRI]

The classification of metabolic disorders according to the etiology is not practical for neuroradiological purposes because the underlying defect does not uniformly transform into morphological characteristics. Therefore typical MR and clinical features of some easily identifiable metabolic disorders are presented. Canavan disease, Pelizaeus-Merzbacher disease, Alexander disease, X-chromosomal adrenoleukodystrophy and adrenomyeloneuropathy, mitochondrial disorders, such as MELAS (mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes) and Leigh syndrome as well as L-2-hydroxyglutaric aciduria are presented.

Strategies for treatment in Alexander disease

Alexander disease is a rare and generally fatal disorder of the CNS, originally classified among the leukodystrophies because of the prominent myelin deficits found in young patients. The most common form of this disease affects infants, who often have profound mental retardation and a variety of developmental delays, but later onset forms also occur, sometimes with little or no white matter pathology at all. The pathological hallmark of Alexander disease is the inclusion body, known as Rosenthal fiber, within the cell bodies and processes of astrocytes. Recent genetic studies identified heterozygous missense mutations in glial fibrillary acidic protein (GFAP), the major intermediate filament protein in astrocytes, as the cause of nearly all cases of Alexander disease. These studies have transformed our view of this disorder and opened new directions for investigation and clinical practice, particularly with respect to diagnosis. Mechanisms by which expression of mutant forms of glial fibrillary acidic protein (GFAP) lead to the pleiotropic manifestations of disease (afflicting cell types beyond the ones expressing the mutant gene) are slowly coming into focus. Ideas are beginning to emerge that suggest several compelling therapeutic targets for interventions that might slow or arrest the evolution of the disease. This review will outline the rationale for pursuing these strategies, and highlight some of the critical issues that must be addressed in the planning of future clinical trials.

The clinical spectrum of late-onset Alexander disease: a systematic literature review

Following the discovery of glial fibrillary acidic protein (GFAP) mutations as the causative factor of Alexander disease (AxD), new case reports have recently increased, prompting a more detailed comprehension of the clinical features of the three disease subtypes (infantile, juvenile and adult). While the clinical pattern of the infantile form has been substantially confirmed, the late-onset subtypes (i.e., juvenile and adult), once considered rare manifestations of AxD, have displayed a wider clinical spectrum. Our aim was to evaluate the clinical phenotype of the adult and juvenile forms by reviewing the previously reported cases. Data were collected from previously published reports on 112 subjects affected by neuropathologically or genetically proven adult and juvenile Alexander disease. Although the late-onset forms of AxD show a wide clinical variability, a common pattern emerges from comparing previously reported cases, characterized by pseudo-bulbar signs, ataxia, and spasticity, associated with atrophy of the medulla and upper cervical cord on neuroimaging. Late-onset AxD cases can no longer be considered as rare manifestations of the disease. The clinical pattern usually reflects the topographic localization of the lesions, with adult cases displaying a predominant infratentorial localization of the lesions. Juvenile cases show clinical and radiological features which are intermediate between adult and infantile forms.

Leukodystrophies with late disease onset: an update

PURPOSE OF REVIEW

Knowledge of the metabolic and genetic basis of known and previously unknown leukodystrophies is constantly increasing, opening new treatment options such as enzyme replacement or cell-based therapies. This brief review highlights some recent work, particularly emphasizing results from studies in adulthood leukodystrophies.

RECENT FINDINGS

Evidence from recent studies suggests increasing importance of metabolic dysfunctions, for example, in peroxisomal lipid metabolism or energy homeostasis, influencing axonal integrity and oligodendrocyte function and leading to white matter demyelination. In addition, diagnostic and therapeutic progress in metachromatic leukodystrophy, X-linked adrenoleukodystrophy, Krabbe diseases and other rare leukodystrophies with late onset are summarized.

SUMMARY

Better understanding of leukodystrophies in neurological routine practice is of crucial importance for differentiating between other white matter diseases such as toxic, inflammatory or vascular leukoencephalopathies. Many leukodystrophies are particularly important to recognize because specific treatments already exist or are currently under investigation. The article also provides an overview of currently known leukodystrophies in adulthood.

The burden of inherited leukodystrophies in children

OBJECTIVES

Leukodystrophies are diseases of the white matter for which data concerning clinical characteristics, incidence, disease burden, and description of outcomes are sparse. The purpose of our study was to determine the incidence and most common types of inherited leukodystrophies in a population, the mortality and time course of deaths, common neurologic features in patients, and health care costs associated with leukodystrophies.

METHODS

We conducted a retrospective, hospital- and clinic-based surveillance of inherited leukodystrophies among children younger than 18 years presenting to a regional children's hospital. We enrolled children evaluated from January 1, 1999, through December 31, 2007; clinical information was obtained from medical records. We calculated incidence based on state birth rates.

RESULTS

A total of 122 children with an inherited leukodystrophy were identified; 542 patients were excluded. A total of 49% had epilepsy, 43% required a gastrostomy tube, and 32% had a history of developmental regression. Mortality was 34%; average age at death was 8.2 years. No final diagnosis was reported in 51% of patients. The most common diagnoses were metachromatic leukodystrophy (8.2%), Pelizaeus-Merzbacher disease (7.4%), mitochondrial diseases (4.9%), and adrenoleukodystrophy (4.1%). Endocrine abnormalities and hypoplastic cerebellum were noted in significant portions of patients (15% and 14%). Average yearly per-patient medical costs were $22,579. Population incidence was 1 in 7,663 live births.

CONCLUSIONS

Inherited leukodystrophies are associated with substantial morbidity and mortality in children. Overall population incidence is higher than generally appreciated (1 in 7,663 live births). Most leukodystrophies remain undiagnosed, but a logical algorithm based on prevalence could aid testing.

Adult-onset Alexander disease with typical "tadpole" brainstem atrophy and unusual bilateral basal ganglia involvement: a case report and review of the literature

BACKGROUND

Alexander disease (ALX) is a rare neurological disorder characterized by white matter degeneration and cytoplasmic inclusions in astrocytes called Rosenthal fibers, labeled by antibodies against glial fibrillary acidic protein (GFAP). Three subtypes are distinguished according to age at onset: infantile (under age 2), juvenile (age 2 to 12) and adult (over age 12). Following the identification of heterozygous mutations in GFAP that cause this disease, cases of adult-onset ALX have been increasingly reported.

CASE PRESENTATION

We present a 60-year-old Japanese man with an unremarkable past and no family history of ALX. After head trauma in a traffic accident at the age of 46, his character changed, and dementia and dysarthria developed, but he remained independent. Spastic paresis and dysphagia were observed at age 57 and 59, respectively, and worsened progressively. Neurological examination at the age of 60 revealed dementia, pseudobulbar palsy, left-side predominant spastic tetraparesis, axial rigidity, bradykinesia and gaze-evoked nystagmus. Brain MRI showed tadpole-like atrophy of the brainstem, caused by marked atrophy of the medulla oblongata, cervical spinal cord and midbrain tegmentum, with an intact pontine base. Analysis of the GFAP gene revealed a heterozygous missense mutation, c.827G>T, p.R276L, which was already shown to be pathogenic in a case of pathologically proven hereditary adult-onset ALX.

CONCLUSION

The typical tadpole-like appearance of the brainstem is strongly suggestive of adult-onset ALX, and should lead to a genetic investigation of the GFAP gene. The unusual feature of this patient is the symmetrical involvement of the basal ganglia, which is rarely observed in the adult form of the disease. More patients must be examined to confirm, clinically and neuroradiologically, extrapyramidal involvement of the basal ganglia in adult-onset ALX.

Leukodystrophies and other genetic metabolic leukoencephalopathies in children and adults

Abnormalities of CNS white matter are frequently detected in patients with neurological disorders when MRI studies are performed. Among the many causes of such abnormalities, a large group of rare genetic diseases poses considerable diagnostic problems. Here we present a compilation of genetic leukoencephalopathies to consider when one is confronted with white matter disease of possibly genetic origin. The table contains essentials such as age at onset of symptoms, clinical and MRI characteristics, basic defect, and useful diagnostic studies. The table serves as a diagnostic check list.

Alexander disease: An important mimicker of focal brainstem glioma

We report the case of a 6-year-old male who was referred to a tertiary oncology center with a focal brainstem lesion which was presumed to be neoplastic. Due to the symmetric nature of the lesion on magnetic resonance imaging, the evaluation was expanded to investigate other possible causes and eventual diagnosis of Alexander's disease (AD) was made. AD is a neurodegenerative disease which must be included in the differential for tumor-like lesions within the posterior fossa.

[Adult onset Alexander disease with a novel variant (S398F) in the glial fibrillary acidic protein gene]

We report a 58-year-old woman with adult onset Alexander disease. At the age of 54 she noticed numbness in bilateral legs and at 57 she developed left sided spastic gait. Her walking difficulty was gradually worsened and followed by the development of weakness in left arm, dysarthria and dysphagia. Her mother and elder brother also had similar clinical presentations which suggested an autosomal dominant neurological disorder. With MRI findings showing localized atrophy of medulla oblongata and upper cervical cord with hyperintensities on T2-weighted image, diagnosis of adult onset Alexander disease was made. We performed genetic analysis and found novel variant (S398F) in the glial fibrillary acidic protein gene. In case of slowly progressive myelopathy with bulbar palsy of unknown origin, especially those with atrophy limited to medulla oblongata and upper cervical cord, adult onset Alexander disease should be taken into consideration.

Alexander disease as a cause of nocturnal vomiting in a 7-year-old girl

Alexander disease is a rare form of leukodystrophy with a highly variable clinical course. Occasionally night-time nausea and vomiting are the first symptoms of juvenile Alexander disease. A 7-year-old girl had recurrent night-time vomiting and her growth and weight gain had deteriorated after her sixth birthday. Cranial MRI demonstrated two small, symmetrical focal areas of abnormally high signal intensity in the dorsal medulla oblongata on T2-W and FLAIR images. These were suggestive of juvenile Alexander disease, and subsequent sequencing of the glial fibrillary acidic protein (GFAP) gene revealed a heterogeneous missense mutation in the GFAP gene in exon 6. Alexander disease should be considered in young patients with atypical anorexia nervosa-type symptoms.

Review of Alexander disease: beyond the classical concept of leukodystrophy

Alexander disease is classified as one of the leukodystrophies, which are degenerative diseases primarily affecting the cerebral white matter. Formal diagnosis is achieved by showing diffuse accumulation of Rosenthal fibers in the brain by biopsy or autopsy. Showing a heterozygous mutation in the glial fibrillary acidic protein (GFAP) gene is currently sufficient for diagnosis. The mechanisms of Rosenthal fiber formation remain unclear. However, both the quality and quantity of GFAP are important. GFAP-epsilon (rodent homologous GFAP-delta), one of the alternatively spliced GFAP isoforms, may also play a modulating role in aggregate formation. The current ease of diagnosis has accelerated the accumulation of a wide variety of patients with Alexander disease along with the widespread use of MRI. In contrast to the classical infantile type, patients with juvenile and adult types mainly complain of bulbar symptoms and usually show progressive atrophy of the lower brainstem and cervical spinal cord with mild or minimal leukodystrophic changes. Among the many MRI findings of Alexander disease, periventricular linear lesions with various names depending on the thickness and shape seem to represent the unique pathophysiology, because the subventricular zone of the adult human brain includes special astrocytes that behave as multipotent progenitor cells and specifically produce GFAP-epsilon. Except for a few mutations, no clear phenotype-genotype correlation has been established for Alexander disease, although male preponderance in the infantile type suggests that phenotypes may be partly affected by gender.

Megalencephalic leukoencephalopathy with subcortical cysts: a third confirmed case with literature review

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) causes early-onset, slowly progressive central nervous system white matter disease, macrocephaly, and later cognitive and motor decline. We describe brain structure in a patient with MLC and proven MLC1 mutations. A male, normal at birth, had macrocephaly at 6 months followed by developmental delay. Magnetic resonance imaging showed extensive signal abnormality in cerebral white matter and subcortical progressive cystic changes in the bilateral temporal and right frontal areas. Biopsy of frontal gyrus at age 15 months showed normal gray matter. The subcortical white matter was pale due to prominent fine uniform 2- to 4-mu-thick vacuoles with a few interspersed myelinated axons and rare microglia. The vacuoles had a single-, double-, or, rarely, triple-unit membrane (resembling myelin) and contained occasional organelles but no intermediate filaments. Both normal myelinated and thinly myelinated axons were observed. The outer and occasionally the inner layers of myelin surrounding intact axons formed blebs that may represent a source for vacuoles. Genetic analysis identified 2 heterozygous mutations of intron 3 (c.322-1 G>A) and intron 7 (c.597+1G>A), the 1st leading to deletion of amino acids 60 to 89 and the 2nd to deletion of amino acids 194 to 199. Fine uniform vacuolation of white matter with wide separation of myelinated axons is the hallmark of MLC in early childhood.

Invited article: an MRI-based approach to the diagnosis of white matter disorders

BACKGROUND

There are many different white matter disorders, both inherited and acquired, and consequently the diagnostic process is difficult. Establishing a specific diagnosis is often delayed at great emotional and financial costs. The pattern of brain structures involved, as visualized by MRI, has proven to often have a high diagnostic specificity.

METHODS

We developed a comprehensive practical algorithm that relies mainly on the characteristics of brain MRI.

RESULTS

The initial decision point defines a hypomyelination pattern, in which the cerebral white matter is hyperintense (normal), isointense, or slightly hypointense relative to the cortex on T1-weighted images, vs other pathologies with more prominent hypointensity of the cerebral white matter on T1-weighted images. In all types of pathology, the affected white matter is hyperintense on T2-weighted images, but, as a rule, the T2 hyperintensity is less marked in hypomyelination than in other pathologies. Some hypomyelinating disorders are typically associated with peripheral nerve involvement, while others are not. Lesions in patients with pathologies other than hypomyelination can be either confluent or isolated and multifocal. Among the diseases with confluent lesions, the distribution of the abnormalities is of high diagnostic value. Additional MRI features, such as white matter rarefaction, the presence of cysts, contrast enhancement, and the presence of calcifications, further narrow the diagnostic possibilities.

CONCLUSION

Application of a systematic decision tree in MRI of white matter disorders facilitates the diagnosis of specific etiologic entities.

MR imaging characteristics and neuropathology of the spinal cord in adult-onset autosomal dominant leukodystrophy with autonomic symptoms

BACKGROUND AND PURPOSE

MR imaging findings in adult-onset autosomal dominant leukodystrophy (ADLD) with autonomic symptoms have been described in the brain, but no descriptions of MR imaging findings in the spinal cord have been published. Here, we describe MR imaging findings in the spinal cord in adult-onset ADLD with autonomic symptoms and histopathologic investigations of the spinal cord.

MATERIALS AND METHODS

Twelve subjects from 2 families with adult-onset ADLD with autonomic symptoms identified by clinical investigation underwent MR imaging examination of the spinal cord. Sagittal and transverse sections were obtained. MR imaging examination of the brain was performed in 11 patients. One of the patients underwent postmortem examination, and the spinal cord was subjected to histopathologic analysis.

RESULTS

In all family members with adult-onset ADLD with autonomic symptoms, even in the asymptomatic person, the spinal cord was thin. All examined family members also had a slight general white matter signal intensity (SI) increase in the whole spinal cord, mainly visible in T2-weighted transverse images. The pathologic examination revealed a discrete demyelination in the spinal cord. Brain MR imaging also showed increased T2 SI in the white matter.

CONCLUSIONS

The spinal cord is affected in adult-onset ADLD with autonomic symptoms. Findings consist of atrophy and a diffuse T2 SI increase in the white matter. Transverse images are needed to assess these findings. The typical SI changes of the spinal cord are also present in subjects without clinical symptoms of the disease and with very limited changes in the brain.

Can MR imaging diagnose adult-onset Alexander disease?

BACKGROUND AND PURPOSE

In recent years, the discovery that mutations in the glial fibrillary acidic protein gene (GFAP) were responsible for Alexander disease (AD) brought recognition of adult cases. The purpose of this study was to demonstrate that MR imaging allows identification of cases of AD with adult onset (AOAD), which are remarkably different from infantile cases.

MATERIALS AND METHODS

In this retrospective study, brain and spinal cord MR imaging studies of 11 patients with AOAD (7 men, 4 women; age range, 26-64 years; mean age, 43.6 years), all but 1 genetically confirmed, were reviewed. Diffusion and spectroscopic investigations were available in 6 patients each.

RESULTS

Atrophy and changes in signal intensity in the medulla oblongata and upper cervical spinal cord were present in 11 of 11 cases and were the diagnostic features of AOAD. Minimal to moderate supratentorial periventricular abnormalities were seen in 8 patients but were absent in the 3 oldest patients. In these patients, postcontrast enhancement was also absent. Mean diffusivity was not altered except in abnormal white matter (WM). Increase in myo-inositol (mIns) was also restricted to abnormal periventricular WM.

CONCLUSIONS

Awareness of the MR pattern described allows an effective selection of the patients who need genetic investigations for the GFAP gene. This MR pattern even led to identification of asymptomatic cases and should be regarded as highly characteristic of AOAD.

Acute onset of fatal vegetative symptoms: unusual presentation of adult Alexander disease

Since genetic analysis of the GFAP gene for the diagnosis of adult Alexander disease (AD) has been established in 2001, several cases of both sporadic and familial cases of AD have been described. Except for one patient, all subjects revealed glial fibrillary acidic protein (GFAP) mutations, and clinical progression of symptoms, mainly bulbar and pseudobulbar, were moderate. Here we report on a patient with acute onset of vegetative symptoms, rapid progression, and death within 2 months. Although histology and final magnetic resonance imaging (MRI) were characteristic of AD, sequencing of the encoding GFAP gene revealed no mutation. We believe that this case report expands the so far known clinical spectrum and MRI dynamics of adult AD, and suggest that analysis of the coding part of GFAP may be inconclusive in rare cases. In such patients, only histology may lead to definitive diagnosis.

GFAP mutations and polymorphisms in 13 unrelated Italian patients affected by Alexander disease

Alexander disease (AD), a rare neurodegenerative disorder of the central nervous system, is characterized by the accumulation of cytoplasmic protein aggregates (Rosenthal fibers) composed of glial fibrillary acidic protein (GFAP) and small heat-shock proteins within astrocytes. To date, more than 40 different GFAP mutations have been reported in AD. The present study is aimed at the molecular diagnosis of Italian patients suspected to be affected by AD. By analyzing the GFAP gene of 13 unrelated patients (eight with infantile form, two with juvenile form and three with adult form), we found 11 different alleles, including four new ones. Among the novel mutations, three (p.R70Q, p.R73K, and p.R79P) were identified in exon 1 and p.L359P in exon 6. The sequence analysis also detected six different single nucleotide polymorphic variants, including two previously unreported ones, spread throughout non-coding regions (introns 2, 3, 5, 6, and 3'UTR) of the gene. All patients were heterozygous for the mutations, thus confirming their dominant effect.

Magnetic resonance spectroscopy and metabolic imaging in white matter diseases and pediatric disorders

This review provides the reader with an overview of the magnetic resonance spectroscopy technique and the clinical, pathological, imaging, and metabolic features for select white matter disorders of interest. With this composite summary, the reader should find it easier to implement and interpret spectroscopy in the clinical setting for the diagnosis and monitoring of patients with white matter disorders.

GFAP and its role in Alexander disease

Here we review how GFAP mutations cause Alexander disease. The current data suggest that a combination of events cause the disease. These include: (i) the accumulation of GFAP and the formation of characteristic aggregates, called Rosenthal fibers, (ii) the sequestration of the protein chaperones alpha B-crystallin and HSP27 into Rosenthal fibers, and (iii) the activation of both Jnk and the stress response. These then set in motion events that lead to Alexander disease. We discuss parallels with other intermediate filament diseases and assess potential therapies as part of this review as well as emerging trends in disease diagnosis and other aspects concerning GFAP.

The functional alteration of mutant GFAP depends on the location of the domain: morphological and functional studies using astrocytoma-derived cells

To clarify the functional effects of mutant glial fibrillary acidic protein (GFAP), we examined the expression patterns of mutant GFAPs (V87G, R88C, and R416W) in astrocytoma-derived cells and performed migration assay. The morphological change was found in mutant GFAP cells, although the number of changes was small. On migration assay, the migration rate in cells with the V87G or R88C mutation, which are located in the helical rod domain in GFAP, was significantly higher than those of wild-type and R416W. These findings suggest that the functional abnormalities of astrocytes might be induced prior to aggregation of GFAP in Alexander disease and that the functional alteration depends on the location of the domain.

Alexander disease-associated glial fibrillary acidic protein mutations in mice induce Rosenthal fiber formation and a white matter stress response

Mutations in the gene for the astrocyte specific intermediate filament, glial fibrillary acidic protein (GFAP), cause the rare leukodystrophy Alexander disease (AxD). To study the pathology of this primary astrocyte defect, we have generated knock-in mice with missense mutations homologous to those found in humans. In this report, we show that mice with GFAP-R76H and -R236H mutations develop Rosenthal fibers, the hallmark protein aggregates observed in astrocytes in AxD, in the hippocampus, corpus callosum, olfactory bulbs, subpial, and periventricular regions. Astrocytes in these areas appear reactive and total GFAP expression is elevated. Although general white matter architecture and myelination appear normal, when crossed with an antioxidant response element reporter line, the mutant mice show a distinct pattern of reporter-gene induction that is especially prominent in the corpus callosum, and histochemical staining reveals accumulation of iron in the same region. The mutant mice have a normal lifespan and show no overt behavioral defects, but are more susceptible to kainate-induced seizures. Although these mice demonstrate increased GFAP expression by themselves, further elevation of GFAP via crosses to GFAP transgenic animals leads to a shift in GFAP solubility, an increased stress response, and ultimately death. The mice do not display the full spectrum of pathology observed in human infantile AxD, but may more closely resemble the adult form of the disease. These studies provide formal proof linking GFAP mutations with Rosenthal fibers and oxidative stress, and correlate gliosis and GFAP protein levels to the severity of the disease.