Brain MRI findings as an important diagnostic clue in glutaric aciduria type 1

Sensorineural Hearing Loss in a Child with Succinic Semialdehyde Dehydrogenase Deficiency

Succinic semialdehyde dehydrogenase (SSADH) deficiency is a rare autosomal-recessive disorder of gamma-aminobutyric acid (GABA) metabolism, resulting in accumulation of GABA and gamma-hydroxybutyric acid (GHB) in physiological fluids. Approximately 450 patients have been diagnosed worldwide with this inherited neurotransmitter disorder. We report on a five-year-old male patient, homozygous for the pathogenic variant (NM_170740:c.1265G>A) in ALDH5A1 presenting with an unexpected association of typical SSADH deficiency manifestations with bilateral sensorineural hearing loss (SNHL). Brainstem evoked response audiometry (BERA) testing showed mid-frequency sensorineural hearing damage that suggested a hereditary component to SNHL. Whole exome sequencing (WES) failed to discern other genetic causes of deafness. Several variants of uncertain significance (VUS) detected in genes known for their role in hearing physiology could not be verified as the cause for the SNHL. It is known that central auditory processing depends on a delicate balance between excitatory and inhibitory neurotransmission, and GABA is known to play a significant role in this process. Additionally, excessive concentrations of accumulated GABA and GBH are known to cause a down-regulation of GABA receptors, which could have an adverse influence on hearing function. However, these mechanisms are very speculative in context of SNHL in a patient with inherited disorder of GABA metabolism. Injury of the globi pallidi, one of hallmarks of SSADH deficiency, could also be a contributory factor to SNHL, as was suspected in some other inborn errors in metabolism. We hope that this case will contribute to the understanding of phenotypic complexity of SSADH deficiency.

Inherited Metabolic Causes of Stroke in Children: Mechanisms, Types, and Management

A stroke should be considered in cases of neurologic decompensation associated with inherited metabolic disorders. A resultant stroke could be a classical ischemic stroke (vascular stroke) or more commonly a "metabolic stroke." A metabolic stroke begins with metabolic dysfunctions, usually caused by a stressor, and leads to the rapid onset of prolonged central neurological deficits in the absence of vessel occlusion or rupture. The cardinal features of a metabolic stroke are stroke-like episodes without the confirmation of ischemia in the typical vascular territories, such as that seen in classic thrombotic or embolic strokes. Identifying the underlying cause of a metabolic stroke is essential for prompt and appropriate treatment. This study reviews the major inherited metabolic disorders that predispose patients to pediatric stroke, with an emphasis on the underlying mechanisms, types, and management.

Diagnostic Approach to Macrocephaly in Children

Macrocephaly affects up to 5% of the pediatric population and is defined as an abnormally large head with an occipitofrontal circumference (OFC) >2 standard deviations (SD) above the mean for a given age and sex. Taking into account that about 2-3% of the healthy population has an OFC between 2 and 3 SD, macrocephaly is considered as "clinically relevant" when OFC is above 3 SD. This implies the urgent need for a diagnostic workflow to use in the clinical setting to dissect the several causes of increased OFC, from the benign form of familial macrocephaly and the Benign enlargement of subarachnoid spaces (BESS) to many pathological conditions, including genetic disorders. Moreover, macrocephaly should be differentiated by megalencephaly (MEG), which refers exclusively to brain overgrowth, exceeding twice the SD (3SD-"clinically relevant" megalencephaly). While macrocephaly can be isolated and benign or may be the first indication of an underlying congenital, genetic, or acquired disorder, megalencephaly is most likely due to a genetic cause. Apart from the head size evaluation, a detailed family and personal history, neuroimaging, and a careful clinical evaluation are crucial to reach the correct diagnosis. In this review, we seek to underline the clinical aspects of macrocephaly and megalencephaly, emphasizing the main differential diagnosis with a major focus on common genetic disorders. We thus provide a clinico-radiological algorithm to guide pediatricians in the assessment of children with macrocephaly.

Bilateral lesions of the basal ganglia and thalami (central grey matter)-pictorial review

The basal ganglia and thalami are paired deep grey matter structures with extensive metabolic activity that renders them susceptible to injury by various diseases. Most pathological processes lead to bilateral lesions, which may be symmetric or asymmetric, frequently showing characteristic patterns on imaging studies. In this comprehensive pictorial review, the most common and/or typical genetic, acquired metabolic/toxic, infectious, inflammatory, vascular and neoplastic pathologies affecting the central grey matter are subdivided according to the preferential location of the lesions: in the basal ganglia, in the thalami or both. The characteristic imaging findings are described with emphasis on the differential diagnosis and clinical context.

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.

Genomics and Radiogenomics in Inherited Neurometabolic Disorders - A Practical Primer for Pediatricians

Advances in genetics has revolutionised the way we understand, diagnose and manage neurological disorders. Notwithstanding the fact that genetic confirmation has already become standard of care in routine clinical practice, radiological and clinical phenotyping has not diminished in value; in fact it has found an enhanced role in guiding and interpreting genetic test results. Inherited neurometabolic disorders are a prominent group of disorders which are seen commonly in clinical practice and many are potentially treatable. The concept of Radiogenomics is the bridge from phenotype to genotype and the strength of association varies widely across different inherited metabolic diseases. Understanding the strengths and limitations of these correlations forms the basis of success of multidisciplinary approach to diagnose these disorders. In this article authors give a brief overview of the genetic basis of a disease, available genetic tests and the prominent role of radiology in contemplating a diagnostic suspicion and guiding further confirmatory tests.

A Case of Mistaken Identity: Glutaric Aciduria Type I Masquerading as Postmeningitic Hydrocephalus

We report the characteristic neuroimaging features of a rare metabolic leukodystrophy in an 8-year-old boy, born of consanguineous parenthood. The child presented with macrocrania, regression of milestones, and dystonia. The patient was referred for magnetic resonance imaging with a clinical diagnosis of postmeningitic hydrocephalus. Imaging revealed ventriculomegaly, diffuse brain atrophy, bilaterally symmetric widened sylvian fissure with temporal lobe hypoplasia, periventricular white-matter hyperintensities, and atrophy with hyperintensity in bilateral basal ganglia was also seen. These imaging features were signatory to arrive at a diagnosis of glutaric aciduria type 1. This disorder may mimic other neurological diseases such as postmeningitic hydrocephalus, which delays the diagnosis. Since early diagnosis and treatment can arrest progression, increased awareness about this condition among radiologists will certainly prevent erroneous diagnosis as had occurred in our patient.

Oxidative damage in glutaric aciduria type I patients and the protective effects of l-carnitine treatment

The deficiency of the enzyme glutaryl-CoA dehydrogenase, known as glutaric acidemia type I (GA-I), leads to the accumulation of glutaric acid (GA) and glutarilcarnitine (C5DC) in the tissues and body fluids, unleashing important neurotoxic effects. l-carnitine (l-car) is recommended for the treatment of GA-I, aiming to induce the excretion of toxic metabolites. l-car has also demonstrated an important role as antioxidant and anti-inflammatory in some neurometabolic diseases. This study evaluated GA-I patients at diagnosis moment and treated the oxidative damage to lipids, proteins, and the inflammatory profile, as well as in vivo and in vitro DNA damage, reactive nitrogen species (RNS), and antioxidant capacity, verifying if the actual treatment with l-car (100 mg kg^-1  day^-1 ) is able to protect the organism against these processes. Significant increases of GA and C5DC were observed in GA-I patients. A deficiency of carnitine in patients before the supplementation was found. GA-I patients presented significantly increased levels of isoprostanes, di-tyrosine, urinary oxidized guanine species, and the RNS, as well as a reduced antioxidant capacity. The l-car supplementation induced beneficial effects reducing these biomarkers levels and increasing the antioxidant capacity. GA, in three different concentrations, significantly induced DNA damage in vitro, and the l-car was able to prevent this damage. Significant increases of pro-inflammatory cytokines IL-6, IL-8, GM-CSF, and TNF-α were shown in patients. Thus, the beneficial effects of l-car presented in the treatment of GA-I are due not only by increasing the excretion of accumulated toxic metabolites, but also by preventing oxidative damage.

Macrocephaly: Solving the Diagnostic Dilemma

Macrocephaly is a relatively common clinical condition affecting up to 5% of the pediatric population. It is defined as an abnormally large head with an occipitofrontal circumference greater than 2 standard deviations above the mean for a given age and sex. Megalencephaly refers exclusively to brain overgrowth exceeding twice the standard deviation. Macrocephaly can be isolated and benign or may be the first indication of an underlying congenital, genetic, or acquired disorder, whereas megalencephaly is more often syndromic. Megalencephaly can be divided into 2 subtypes: metabolic and developmental, caused by genetic defects in cellular metabolism and alterations in signaling pathways, respectively. Neuroimaging plays an important role in the evaluation of macrocephaly, especially in the metabolic subtype which may not be overtly apparent clinically. This article outlines the diverse etiologies of macrocephaly, delineates their clinical and radiographic features, and suggests a clinicoradiological algorithm for evaluation.

Toxic-Metabolic Neurologic Disorders in Children: A Neuroimaging Review

There are multiple causes of neurotoxicity in children including medications, extrinsic toxins and insults, illicit drugs, built up of toxic metabolites due to genetic or acquired disorders, and metabolic abnormalities. The review is centered on causes of neurotoxicity affecting the pediatric brain and producing typical and easily recognized imaging manifestations. Early identification of common and less common imaging findings may point toward the correct direction, and may facilitate early diagnosis and institution of appropriate treatment to reverse or at least limit the injury to the developing brain. Two common imaging patterns of neurotoxicity in children are the posterior reversible encephalopathy syndrome and acute toxic leukoencephalopathy that are usually related to chemotherapy and immunosuppression for common pediatric malignancies. Another well-described imaging pattern of injury in children involves reversible splenial lesions with or without associated white matter abnormalities. Multiple additional extrinsic causes of neurotoxicity are presented including radiation and chemoradiation, various medications and treatment regimens, poisoning, illicit drug use or accidental exposure, and the respective characteristic neuroimaging findings are highlighted. Intrinsic neurotoxicity may occur in the setting of inborn errors of metabolism or acquired progressive organ failure leading to build up of toxic metabolites. Additional intrinsic causes of neurotoxicity include metabolic derangements and characteristic imaging findings in all instances are reviewed. The goal of the article is to enhance familiarity of neurologists and neuroradiologists with the imaging appearance of common and less common toxic insults to the pediatric brain.

Audit of Organic Acidurias from a Single Centre: Clinical and Metabolic Profile at Presentation with Long Term Outcome

Introduction

Organic Acidurias (OA) accounts between 10% and 40% of confirmed Inborn Errors of Metabolism (IEM) in India. With prompt recognition and management, better survival but adverse neurodevelopmental outcome is reported.

Aim

To study the clinical and metabolic presentation, management with immediate and long term outcome of symptomatic children with confirmed OA.

Materials and Methods

Hospital based study of symptomatic children diagnosed to have OA between 2003 and 2009 and the survivors followed up over next five years. Diagnosis was based on clinical and metabolic presentation and confirmed by spectrometry analyses of urine and blood. Management, immediate outcome, compliance to treatment and recurrence of crises were documented. Neurodevelopmental outcome was assessed in follow up. Mean with Standard Error (Mean ± SE) and frequencies with percentages were calculated.

Results

Of 72 cases suspected to have IEM, 38 (52.8%) were confirmed of (IEM), and out of which 15 (39.5%) had OA. Methyl malonic acidemia, multiple carboxylase deficiency and Propionic Acidemia (PA) constituted the largest proportion. Neurodevelopmental issues (73.3%) and metabolic crisis (53.3%) were common presenting features. Mean ± SE of ammonia was 639.0±424.1 μg/dl and lactate was 33.6±4.9 mg/dl. Mean pH, bicarbonate, and anion gap was 7.27±0.07, 14.1±2.3 and 17.9±2.3 respectively. Management was protocol based. Death was reported in two cases of PA; other morbidities were seen in five. Recurrent crisis (46.7%) complicated the follow up in survivors. Spasticity, extrapyramidal movement disorder, intellectual subnormality, autism spectrum, attention deficit hyperactivity disorder and sensory neural deafness were seen amongst survivors, in spite of compliance to therapy.

Conclusion

OA is part of differential diagnosis in sick children and treatment needs to be prompt and specific. Prognosis is guarded even with long term cofactor supplementation in the symptomatic.

Clinical and laboratory analysis of late-onset glutaric aciduria type I (GA-I) in Uighur: A report of two cases

The aim of the present study was to investigate the clinical, biochemical and genetic mutation characteristics of two cases of late-onset glutaric aciduria type I (GA-I) in Uighur. The clinical data and glutaryl-CoA dehydrogenase (GCDH) genetic test results of two cases of late-onset GA-I in Uighur were collected and analyzed, and reviewed with relevant literature. One patient with late-onset GA-I primarily exhibited clinical intermittent headache, while the other patient was asymptomatic. The urinary organic acid analysis detected a large number of glutaric acid and 3-hydroxy glutaric acid, 3-hydroxy-propionic acid. One patient exhibited white matter degeneration in cranial magnetic resonance imaging (MRI) and the other patient showed no abnormality. The two patients both exhibited c. 1204C >T, p.R402W, heterozygous mutation, and c. 532G >A, p.G178R, heterozygous mutation. Besides central nervous system infectious diseases, patients with clinical headache, cranial MRI-suggested bilateral temporal lobe arachnoid cyst and abnormal signals in the basal ganglia should be highly suspected as late-onset GA-I. Early diagnosis and correct treatment are key to improve its prognosis.

[Complex heterogeneity phenotypes and genotypes of glutaric aciduria type 1]

Glutaric aciduria type 1 is a rare autosomal recessive disorder. GCDH gene mutations cause glutaryl-CoA dehydrogenase deficiency and accumulation of glutaric acid and 3-hydroxyglutaric acid, resulting in damage of striatum and other brain nucleus and neurodegeneration. Patients with glutaric aciduria type 1 present with complex heterogeneous phenotypes and genotypes. The symptoms are extremely variable. The ages of the clinical onset of the patients range from the fetus period to adulthood. The patients with mild glutaric aciduria type 1 are almost asymptomatic before onset, however, severe glutaric aciduria type 1 may cause death or disability due to acute encephalopathy. Acute metabolic crisis in patients with underlying glutaric aciduria type 1 is often triggered by febrile illnesses, trauma, hunger, high-protein foods and vaccination during a vulnerable period of brain development in infancy or early childhood. The early-onset patients usually have a poor prognosis. Urinary organic acids analysis, blood acylcarnitines analysis and GCDH study are important for the diagnosis of this disorder. Neonatal screening is essential for the early diagnosis and the improvement of prognosis.

Indications for the performance of neuroimaging in children

Pediatric neurology relies on ultrasound, computed tomography (CT), and magnetic resonance (MR) imaging. CT prevails in acute neurologic presentations, including traumatic brain injury (TBI), nontraumatic coma, stroke, and status epilepticus, because of easy availability, with images of diagnostic quality, e.g., to exclude hemorrhage, usually completed quickly enough to avoid sedation. Concerns over the risks of ionizing radiation mean re-imaging and higher-dose procedures, e.g., arteriography and venography, require justification. T1/T2-weighted imaging (T1/T2-WI) MR with additional sequences (arteriography, venography, T2*, spectroscopy, diffusion tensor, perfusion, diffusion- (DWI) and susceptibility-weighted imaging (SWI)) often clarifies the diagnosis, which may alter management in acute settings, as well as chronic conditions, e.g., epilepsy. Clinical acumen remains essential to avoid imaging, e.g., in genetic epilepsies or migrainous headaches responding to treatment, or to target sequences to specific diagnosis, e.g., T1/T2-WI for shunt dysfunction (with SWI for TBI); DWI, arteriography including neck vessels, and venography for acute hemiplegia or coma; coronal temporal cuts for partial epilepsy; or muscle imaging for motor delay. The risk of general anesthesia is low; "head-only" scanners may allow rapid MRI without sedation. Timely and accurate reporting, with discrepancy discussion between expert neuroradiologists, is important for management of the child and the family's expectations.

Structural brain defects

Up to 14% of patients with congenital metabolic disease may show structural brain abnormalities from perturbation of cell proliferation, migration, and/or organization. Most inborn errors of metabolism have a postnatal onset. Abnormalities from genetic disease processes have a prenatal onset. Energy impairment, substrate insufficiency, cell membrane receptor and cell signaling abnormalities, and toxic byproduct accumulation are associations between genetic disorders and structural brain anomalies. Collective imaging patterns of brain abnormalities can provide clues to the underlying etiology. We review selected metabolic diseases associated with brain malformations and highlight characteristic clinical and imaging manifestations that help narrow the differential diagnosis.