CT and MRI in late-onset metachromatic leukodystrophy

Neuroimaging Findings in Lysosomal Disorders: 2018 Update

Lysosomal storage disorders are a heterogeneous group of genetic diseases characterized by defective function in one of the lysosomal enzymes. In this review paper, we describe neuroradiological findings and clinical characteristics of neuronopathic lysosomal disorders with a focus on differential diagnosis. New insights regarding pathogenesis and therapeutic perspectives are also briefly discussed.

Myelin, myelin-related disorders, and psychosis

The neuropathological basis of schizophrenia and related psychoses remains elusive despite intensive scientific investigation. Symptoms of psychosis have been reported in a number of conditions where normal myelin development is interrupted. The nature, location, and timing of white matter pathology seem to be key factors in the development of psychosis, especially during the critical adolescent period of association area myelination. Numerous lines of evidence implicate myelin and oligodendrocyte function as critical processes that could affect neuronal connectivity, which has been implicated as a central abnormality in schizophrenia. Phenocopies of schizophrenia with a known pathological basis involving demyelination or dysmyelination may offer insights into the biology of schizophrenia itself. This article reviews the pathological changes in white matter of patients with schizophrenia, as well as demyelinating diseases associated with psychosis. In an attempt to understand the potential role of dysmyelination in schizophrenia, we outline the evidence from a number of both clinically-based and post-mortem studies that provide evidence that OMR genes are genetically associated with increased risk for schizophrenia. To further understand the implication of white matter dysfunction and dysmyelination in schizophrenia, we examine diffusion tensor imaging (DTI), which has shown volumetric and microstructural white matter differences in patients with schizophrenia. While classical clinical-neuropathological correlations have established that disruption in myelination can produce a high fidelity phenocopy of psychosis similar to schizophrenia, the role of dysmyelination in schizophrenia remains controversial.

The neuropsychiatry of inborn errors of metabolism

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

Metachromatic leukodystrophy: a case of triplets with the late infantile variant and a systematic review of the literature

Metachromatic leukodystrophy is a rare disorder with great clinical variability. We report the first case of triplets with the late infantile form of the disease and their systematic progression of symptoms. We reviewed the literature and identified all human studies that reported new cases since 1921. We analyzed survival by decade to assess the impact of historical changes in the management of care. Mean age at death and the 5-year survival from onset of symptoms for late infantile, juvenile, and adult phenotypes were 4.2 years and 24.9%, 17.4 years and 70.3%, and 43.1 years and 88.6%, respectively. The 5-year survival of cases reported after 1990 was significantly better than cases reported before 1970 in all subtypes of metachromatic leukodystrophy (late infantile: 52% vs 14%, juvenile: 100% vs 46%, adult: 95% vs 67%). Survival in the late infantile subtype was worse than that in other subtypes. Survival significantly improved over time in all subtypes.

Partial seizures in two cases of metachromatic leukodystrophy: electrophysiologic and neuroradiologic findings

This report concerns two cases of metachromatic leukodystrophy presenting partial seizures. One was a 2-year-old boy with a late infantile type and the other a 17-year-old girl with a juvenile type. The former had tonic-clonic seizures on the left with concomitant twitching of the left side of the face and adversive conjugate deviation of the eyes. After a while, his interictal sleep electroencephalogram (EEG) showed spikes in the right central area. The second case had hemiconvulsions on the right side, consisting mainly of tonic flexion of the upper limb followed by clonic flexions, and accompanied by adversive conjugate deviation of the head and eyes. Her ictal EEG showed rhythmic 6- to 7-Hz wave bursts in the left frontal area. To this date, no report has given a detailed discussion of the type of seizures and ictal EEG in metachromatic leukodystrophy. In addition, there have been few detailed reports of magnetic resonance imaging (MRI) in the juvenile type. It is interesting that typical partial seizures were observed in a hereditary metabolic disorder characterized by diffuse demyelination of the white matter, and the pathophysiology is discussed here mainly in relation to MRI findings of the case with the juvenile type.

Adult metachromatic leukodystrophy with an unusual relapsing-remitting course

A 46 year old woman had a relapsing-remitting course of hemiparesis, disorientation, paraparesis and seizures, followed by progressive dementia, spasticity and ataxia. Computed tomography at onset showed a parietotemporal hypodense area with diffuse mottled enhancement obliterating the lateral ventricle. Subsequent scans demonstrated symmetric periventricular non-enhancing hypodensities, progressive ventricular enlargement and atrophy. Adult metachromatic leukodystrophy was diagnosed on the basis of low leukocyte arylsulphatase A level and metachromatic material accumulation at neural nerve biopsy.

Reduced activity of arylsulfatase A and predisposition to neurological disorders: analysis of 140 pediatric patients

A sample of 140 children exhibiting neurologic disturbances (93 suffering from epilepsy and 47 with delayed psychomotor development or mental retardation) was tested for the activity of some lysosomal enzymes. A partial deficiency of arylsulfatase A (ASA) in leucocytes (activities lower than 60% of the control average) was detected in 36 patients (25.7%), whereas few ASA-deficient individuals (1.4%) were found in the control sample of 71 healthy children. Therefore, the frequency of ASA deficiency is abnormally high in our sample of pediatric patients. ASA activity levels were also assayed on fibroblasts from 12 of the 36 ASA-deficient patients; the mean activity in these cells was 20% of the control average. Excretion of urinary sulfatides was not increased in the tested ASA-deficient patients (10/36). Clinical symptoms of these ASA-deficient patients bore no resemblance to classical metachromatic leucodystrophy (MLD), but resemble literature cases labeled as atypical MLD or diagnostic puzzles. This result suggests that reduced ASA activity might be associated with an increased risk of developing neurologic or neuropsychiatric disturbances in children.

The relationship of the metachromatic leukodystrophies to neuropsychiatric disorders

The possible relationship between the metachromatic leukodystrophies and neuropsychiatric disorders is reviewed. Four kinds of evidence are considered: psychiatric symptoms as preemergent markers of the neurodegenerative process; increased behavioral problems in leukodystrophy families; screening for low enzyme levels among psychiatric populations; and studies in model systems. Whereas the basic postulate of an increased risk for psychiatric problems among individuals with lower levels of the enzymes deficient in the leukodystrophies remains attractive, there is no strong evidence in its support. Low enzyme levels can be found in psychiatric populations, but they may not be any more frequent than in the general population.