MR imaging of Pelizaeus-Merzbacher disease

Quantification of myelin in children using multiparametric quantitative MRI: a pilot study

PURPOSE

The purpose of this study was to evaluate the usefulness of multiparametric quantitative MRI for myelination quantification in children.

METHODS

We examined 22 children (age 0-14 years) with multiparametric quantitative MRI. The total volume of myelin partial volume (Msum), the percentage of Msum within the whole brain parenchyma (Mbpv), and the percentage of Msum within the intracranial volume (Micv) were obtained. Four developmental models of myelin maturation (the logarithmic, logistic, Gompertz, and modified Gompertz models) were examined to find the most representative model of the three parameters. We acquired myelin partial volume values in different brain regions and assessed the goodness of fit for the models.

RESULTS

The ranges of Msum, Mbpv, and Micv were 0.8-160.9 ml, 0.2-13%, and 0.0-11.6%, respectively. The Gompertz model was the best fit for the three parameters. For developmental model analysis of myelin partial volume in each brain region, the Gompertz model was the best-fit model for pons (R ² = 74.6%), middle cerebeller peduncle (R ² = 76.4%), putamen (R² = 95.8%), and centrum semiovale (R ² = 77.7%). The logistic model was the best-fit model for the genu and splenium of the corpus callosum (R ² = 79.7-93.6%), thalamus (R ² = 81.7%), and frontal, parietal, temporal, and occipital white matter (R ² = 92.5-96.5%).

CONCLUSIONS

Multiparametric quantitative MRI depicts the normal developmental pattern of myelination in children. It is a potential tool for research studies on pediatric brain development evaluation.

Discrepancy between auditory brainstem responses, auditory steady-state responses, and auditory behavior in two patients with Pelizaeus-Merzbacher disease

We reported two cases of Pelizaeus-Merzbacher disease. Both cases visited our hospital manifesting horizontal nystagmoid movements present from birth, and delayed motor development. Magnetic resonance imaging of the brain showed diffuse dysmyelination of the cerebral white matter, and auditory brainstem response showed waves I and II but absence of all subsequent components. Conditioned orientation reflex (COR) audiometry showed poor reactions in an infantile case whose development was severely retarded, and who spoke no meaningful words. Auditory steady-state response (ASSR) was a helpful tool for identifying her auditory ability; thereafter, her communication skills improved naturally. The other case was mildly developmentally retarded, and the results of COR audiometry and ASSR were considered the same level. The discrepancy between results of these hearing tests may arise under the influence of developmental level of the case.

Three young adult patients with Pelizaeus-Merzbacher disease who showed only waves I and II in auditory brainstem responses but had good auditory perception

Three young adult males with Pelizaeus-Merzbacher disease have been followed up since childhood. This disease is thought to be a dysmyelinating disorder of the brain during the prenatal period caused by gene mutations. The patients manifested horizontal nystagmus and severe rigidity of the extremities. Although the patients showed only waves I and II in auditory brainstem responses, they had relatively good hearing ability at approximately equal to dB. They could not speak words at all but could hear well and enjoy listening to conversation and music. One of them had a normal hearing threshold in pure-tone audiometry and a normal speech discrimination rate in speech audiometry. This can be explained by a nerve conduction blockade through dysmyelinated axons or the desynchronization of neurons and nerves responsible for the waves following waves I and II. At present, all three patients are living with their families. We report their present hearing, speech and language abilities.

An MRI and MRS study of Pelizaeus-Merzbacher disease

Earlier reports on T2-weighted magnetic resonance imaging (MRI) in the classical form of Pelizaeus-Merzbacher disease seemed to divide the patterns of the high-intensity lesions in the white matter into three subtypes: type I, diffusely hemispheric and corticospinal; type II, diffusely hemispheric without brainstem lesions; and type III, patchy in the hemispheres. The four boys presented in our study, between 10 and 17 years of age, with classical Pelizaeus-Merzbacher disease, who all had a duplicated proteolipid protein gene, invariably manifested type I despite their various clinical severities. Follow-up MRI after an interval of 5 years and proton magnetic resonance spectroscopy was performed in three of the patients. The white matter on the last MRI was unchanged in volume and the distribution of high-intense areas. Proton magnetic resonance spectroscopy revealed no abnormal peaks. These results were consistent with the lack of definite neurologic regression in the last 5 years and with the pathologic characteristics of well-preserved axons and the absence of sclerosis. Further study is required to precisely determine whether the patterns of MRI findings can be divided into subtypes corresponding to those of proteolipid protein gene abnormalities.

Oculodental digital dysplasia: neuroimaging in a kindred

Oculodental digital dysplasia (ODDD) is an uncommon inherited disorder with characteristic facial abnormalities, defects in dentition and syndactyly; previous reports have described neurologic dysfunction. We present neuroimaging features of a mother and daughter with ODDD; despite only the mother having neurologic dysfunction, the MRI findings in both are strikingly similar.

Spinocerebellar degeneration and cerebral hypomyelination in a family

The proband is a 24-year-old woman who developed symptoms of a spinocerebellar degeneration in early childhood. Neurological examination revealed normal cognitive function, optic atrophy, dysarthria, titubation, action tremors, increased deep tendon reflexes, Babinski's signs, and a spastic scissoring gait. The magnetic resonance imaging (MRI) showed an abnormal increased signal on long TR images involving white matter throughout the cerebral hemispheres, most striking in the subcortical white matter, and to a lesser degree in the brainstem, compatible with diffuse hypomyelinating or dysmyelinating diseases. Metabolic and chromosomal studies were normal. Her 49-year-old mother developed similar symptoms in her 20s and is now wheelchair-bound. Findings on neurological examination and MRI were similar to her daughter but more severe. The proband's maternal grandfather had a female cousin who had a neurological illness beginning in her 20s with similar symptoms and signs and died at the age of 44 years. Spinocerebellar degenerations are a group of syndromes with similar clinical manifestations but heterogeneous etiology. We report a family with spinocerebellar degeneration with distinct MRI findings compatible with hypomyelination or dysmyelination which has not heretofore been described. This family may represent a new spinocerebellar syndrome due to an abnormality of as yet an undetermined gene.

Neurophysiological study in Pelizaeus-Merzbacher disease

The Neurophysiological characteristics of Pelizaeus-Marzbacher disease (PMD) were studied in four Japanese patients aged between 5 and 13 years. Pendular spontaneous nystagmus was always recorded with a frequency between 2.5 and 4 Hz, and abnormal saccades with an almost twofold prolongation in onset time and 50% decrease in velocity were noted. Brainstem auditory evoked potentials consistently demonstrated severely altered waves II to V, following a normal wave I, despite normal hearing acuity. Somatosensory evoked potentials (SEPs) were always absent between brainstem components and early cortical responses. Late cortical components of SEPs and visual evoked potentials with significantly prolonged latencies were recorded in the three younger cases having normal sensory and visual acuity (N35 of SEP, 73.1 +/- 2.1 ms; N75 of VEP, 129.0 +/- 12.7 ms; mean +/- S.D.), while these peaks were absent in the oldest case having the most severe handicap. In motor evoked potentials (MEPs), R1 of blink reflex with significantly prolonged latency (14.9 +/- 1.48ms) was always obtained, and no subsequent R2 was elicited. Magnetic transcortical stimulation elicited no MEPs of the thenar even in the facilitating condition on voluntary contraction despite mild weakness of the thenar, while normal MEPs were always elicited on cervical stimulation. These electrophysiological findings were consistent with extensive conduction slowing involving the brainstem to the cerebrum, which seemed to be accompanied by conduction block in motor systems rather than sensory systems. Although each of the results was not specific, in combination they suggested the characteristics of diffuse brain dysmyelination in PMD.

CT and MRI of the brain in inherited neurometabolic disorders

The incidence of many autosomal recessive neurometabolic disorders is very high in Saudi Arabia, probably as a result of the frequency of consanguineous marriages. Because our hospital is the main referral center for the entire Kingdom, we examine a large number of patients who have a wide spectrum of neurometabolic disorders. We add our experience and review the world literature. Though a specific diagnosis is radiologically possible in a few disorders, the diagnosis must always be verified biochemically. When the patient is referred from a pediatric neurologist with the diagnosis of neurometabolic disorder, the aim of the neuroradiologist is to determine the amount of brain damage present and to follow the response to given therapy. When the patient is referred with a nonspecific diagnosis, such as delayed development, the aim is to suggest the possibility of a neurometabolic disorder and to initiate further evaluation including possible therapy and genetic counseling.

Pelizaeus-Merzbacher disease: clinical and DNA-linkage study of an extended family

We describe a 5-generation family of 6 individuals with Pelizaeus-Merzbacher disease, Type I. DNA linkage study was done to establish carrier status. Two loci, DXS162 and DXYS1, were informative in this family for carrier determination. The highest lod score is that for PMD-DXYS1 (Z = 1.421 at theta = 0). The carrier probability can only be defined as likely or unlikely in the absence of an established recombination frequency.

Mitochondrial encephalomyopathy--two years follow-up by MRI

A case of mitochondrial encephalomyopathy (MEM) followed-up by MRI for 2 1/2 y is presented. MRI showed gross, diffusely distributed white matter lesions in both hemispheres predominantly in frontal, parietal, temporal and occipital locations a marked ventriculomegaly indicative of cerebral atrophy. Except a slight increase of the cerebral atrophy there were no changes in the follow-up examinations. There are no specific MRI findings in MEM, the diagnosis is established by the synopsis of MRI, laboratory data and muscle biopsy.

Complicated hereditary spastic paraparesis with cerebral white matter lesions

A family is described with 5 males in a single generation affected with a previously undescribed complicated form of hereditary spastic paraparesis (HSP). The disease is characterized by speech difficulties, lower limb spasticity and hyper-reflexia, mental retardation, cerebellar ataxia, and tremor. The disease starts in the first decade of life and progresses for 3 to 6 years before stabilizing. Magnetic resonance imaging (MRI) of the brain demonstrates bilateral posterior periventricular white matter lesions. Visual evoked responses are markedly prolonged, but electromyography (EMG) and nerve conduction velocity studies are normal. Three of the 4 living affected members of this pedigree exhibit red-green color vision defects. The presentation of a new complicated hereditary spastic paraparesis syndrome in this pedigree extends our understanding of the variability and heterogenity of this syndrome and suggests an approach for the evaluation of similar families in future genetic studies.

A possible Japanese male case of Pelizaeus-Merzbacher disease

A boy with an abnormal auditory brain stem response showing only a wave I-II pattern, congenital nystagmus, psycho-motor retardation, pyramidal tract signs and muscular hypotonia was reported. The auditory brain stem response, short latency somatosensory-evoked potential, somatosensory-evoked potential and visual-evoked potential indicated an intramedullary disorder of conduction. Magnetic resonance imaging revealed marked high signal intensity of the cerebral white matter in T2-weighted images, suggesting hypomyelination. A muscle biopsy specimen showed neurogenic changes with mild myogenic changes.

Magnetic resonance imaging and computed tomography in Pelizaeus-Merzbacher disease

Six patients with the classical form of Pelizaeus-Merzbacher disease (PMD) were studied with computed tomography (CT) and magnetic resonance imaging (MRI) of the brain. While final diagnosis of PMD should be made on the basis of histopathologic findings in the brain, findings in this group support the fact that MRI can be used for tentative early diagnosis when computer tomographic examination is normal or nondiagnostic. All patients had MRI findings reflecting a pattern of diffuse white matter disease that can be considered characteristic in the appropriate clinical setting.

Pelizaeus-Merzbacher disease: identification of heterozygotes with magnetic resonance imaging?

We report magnetic resonance imaging (MRI) findings in two obligate and four facultative carriers for the "classical" X-linked form of Pelizaeus-Merzbacher disease (PMD). In T2-weighted images MR revealed bilateral multiple areas with signal hyperintensity in the periventricular and subcortical white matter in five women. Until suitable and closely linked DNA probes are found for heterozygote determination, MRI may represent a suitable means for carrier detection in individuals at risk in PMD families.

Magnetic resonance imaging in Pelizaeus-Merzbacher disease

Cranial computed tomography of a boy with clinical characteristics of the classic form of Pelizaeus-Merzbacher disease did not reveal a notable abnormality other than enlarged ventricles. Magnetic resonance imaging, however, demonstrated diffuse changes in the white matter with sparing of scattered small areas, suggesting persistent myelin islands which are a typical neuropathologic finding in Pelizaeus-Merzbacher disease. Magnetic resonance imaging appears more useful than computed tomography in confirming the diagnosis of Pelizaeus-Merzbacher disease.