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The MR evaluation of pachygyria and associated syndromes
Abstract
A retrospective study of 40 children with some form of pachygyria was performed at the Children's Memorial Hospital in Chicago. All 40 children had MR brain scans. We analyzed the MR findings, and correlated these findings with the clinical symptoms and course in all the children. We have autopsy findings in 15% these children. Based on our clinical, MR and autopsy findings, in conjunction with the medical literature, we found the following: (1) Pachygyria can occur as an isolated entity without an association with lissencephaly. The MR findings in these children consisted of a brain that demonstrated normal opercularization with either focal or diffuse areas of pachygyria without areas of agyria. These children live longer and have less severity of symptoms than the children with lissencephaly. (2) The MR findings in children with lissencephaly consisted of a brain that demonstrated abnormal opercularization with areas of total agyria or areas of agyria with pachygyria. (3) The MR findings in 25% of our children with polymicrogyria simulated pachygyria. The MR findings of the brain in these children consisted of a 'nubby' appearance to the outer surface of these abnormal gyri which resembled pachygyria but on histologic exam was polymicrogyria.
... Cases with this association confirmed neuropathologically have been reported [van Allen and Clarren, 1983;Sakuta et al., 1991;Graf et al., 1998]. We also recognize that it is often difficult to differentiate polymicrogyria from pachygyria and that pachygyria on magnetic resonance imaging (MRI) is sometimes diagnosed as polymicrogyria histologically [Byrd et al., 1991]. Our description is based on MRI but the final diagnosis requires neuropathological findings. ...
This chapter covers a varied group of disorders that develop as a consequence of genetic abnormalities, prenatal or perinatal infections, ischemia, or uncertain etiology. All lead to abnormal development of the nervous system. Some disorders have been selected because of the challenge they pose in diagnosis and management, and others because they illustrate important concepts in neurodevelopment or pathophysiology.
This chapter covers a varied group of disorders of inherited, postinfectious, ischemic, or undetermined etiology All lead to abnormal development of the nervous system. Some disorders have been selected because of the challenge they pose in diagnosis and management, and others because they illustrate important concepts in neuroembryology or pathophysiology.
Neuropsychologists frequently work with patients who have specified brain lesions that produce well-documented cognitive or behavioral effects. However, for those clinicians working with children or adolescents who suffer developmental disorders, the pathogenesis of cognitive and behavioral deficits may be poorly understood. This chapter reviews the anomalies of neurological development that not infrequently are seen in children and adolescents with developmental disorders. Most typically the neuropsychological manifestations of these anomalies impact on widely distributed functional systems, thus producing generalized and severe impairment. However, there are exceptions, especially with regard to anomalies of neuronal migration. Some basic understanding of these effects should aid neuropsychologists in a better conceptualization of how disorders of neurological development produce different effects than do discrete lesions of the central nervous system.
Lissencephaly is a rare congenital malformation of the brain characterized by complete or almost complete cerebral agyria. There are variable specific craniofacial features and malformations of other organic systems. We report on the sonographic diagnosis of three cases of lissencephaly. Complete or almost complete absence of gyri and sulci and wide, linear Sylvian fissures could be shown. Additionally, associated malformations such as dilatations of the ventricles, hypoplastic corpus callosum, cerebellum and brain stem could be demonstrated. In our opinion, ultrasonography should be the first examination in patients with micro- and macrocephaly and clinical signs suggesting migrational disorders. Routine sonographic examinations have to describe gyral folding in all patients. The diagnosis should be confirmed by magnetic resonance tomography, which provides better delineation of anatomic detail and gray-white matter differentiation than computer tomography. This allows correct and timely diagnosis which is important for accurate parental counseling with regard to both prognosis and risk for recurrence.
This chapter covers a varied group of disorders that develop as a consequence of genetic abnormalities, infections, ischemia, or uncertain etiology. All lead to abnormal development of the nervous system. Some disorders have been selected because of the challenge they pose in diagnosis and management, and others because they illustrate important concepts in neurodevelopment or pathophysiology.
Neuropsychologists frequently work with patients who have specified brain lesions that produce well-documented cognitive or
behavioral effects. However, for those clinicians working with school-age children or adolescents who suffer developmental
disorders, the pathogenesis of cognitive and behavioral deficits may be poorly understood.
The authors report a case of early infantile epileptic encephalopathy (EIEE) associated with hemimegalencephaly. The etiological factors in previously published cases of EIEE are reviewed and attention is focused on the high proportion of cases associated with neuronal migration disorders. We suggest that idiopathic cases of EIEE would be due to such disorders.
Neuronal migration disorders are the result of disturbed brain development. In such disorders, neurons are abnormally located. In diagnosing these conditions, magnetic resonance imaging is superior to any other imaging technique. This enables us to improve our knowledge of the clinical correlates of neuronal migration. With reference to migrational disorder, a retrospective study of all 303 patients with epileptic seizures referred for magnetic resonance imaging during a 3-year period was performed, 13 patients (aged 12-41, mean age 27) were identified. They represent 4.3% of the entire study group. Of the patients with known epilepsy, 6.7% and of the mentally retarded, 13.7% had migrational disorders. Four patients had schizencephaly as the dominant finding, one was classified as hemimegalencephaly, 2 had isolated heterotopias, and 6 had localized pachy- and/or poly-microgyria. The clinical pictures are complex. Ectopias of grey matter are recognised foci of epilepsy, but from an epileptological and a clinical viewpoint little attention has been given to these disorders. The present study shows that malmigration is not rare in epilepsy patients, especially not in the mentally retarded.
Agyria-pachygyria or lissencephaly type I, a diffuse cortical malformation, provides infantile spasms (IS) which are refractory and persisting after the first decade, an age at which IS have disappeared in the other causes. In order to study the functional postnatal development of the lissencephalic cortex, we measured regional cerebral blood flow (rCBF) using SPECT (Single photon emission computed tomography) and 133Xe in 14 children with lissencephaly, aged from 4 months to 12 years (mean = 40 months) compared to normal children of the same age range and to children with cryptogenic IS aged from 3 months to 3 years (mean = 13 months). rCBF was calculated in frontal (FR) and parieto-temporo-occipital (PTO) cortex as well as the ratio FR/PTO. FR/PTO was higher in lissencephalic patients than in controls (P < 0.001) due to higher FR rCBF (P < 0.001), particularly in patients aged less than 3 years. FR/PTO was also higher in lissencephalic patients than in patients with cryptogenic IS (P < 0.001) also due to higher FR rCBF (P < 0.001). The values of FR/PTO and FR rCBF remained stable during the first years of life and did not exhibit any age- or topography-related changes as they do in controls or in patients with cryptogenic IS. There results suggest that the normal process of postnatal development in the brain is lacking in agyria-pachygyria. That could play a role in determining the persistence of epileptic spasms, the specific seizure type of this malformation.
The architectonic features of abnormal cerebral cortex in a brain with lissencephaly and pachygyria suggest than neuronal migration was interrupted by cortical and subcortical laminar necrosis in the fourth fetal month. The severest cortical abnormality lies in the distal perfusion fields of the major cerebral arteries, while the normal areas are located in the proximal perfusion fields. These architectonic and topographic features suggest that intra-uterine hypoxia or perfusion failure may be a pathogenetic mechanism leading to lissencephaly and pachygyria.
A clinico-pathological report is given on 4 cases of agyria (premature neonate to age 13 months), 3 cases of pachygyria (aged 2,5 to 4,3 years) and a boy aged 4,5 years with temporal pachygyria and frontal microgyrias. Clinical features, more pronounced in agyria than in pachygyria, were microcephaly, frequent facial anomalies, neonatal feeding difficulties, hypotonia with subsequent seizures, hypsarrhythmic EEG pattern in 3 children, arrest of psychomotor development and signs of decerebration. One case of agyria occurred with familial faciorenal dysplasia, two were associated with congenital heart disease, and the fourth with chromosomal abnormality. Morphologically, the colpocephalic brain showed a four-layered agyric pallium with radially aligned cell columns and periventricular heterotopias, lacking differentiation of the claustra, olivary heterotopias and cerebellar dysgenesias in the 4 younger infants. In the agyric neonate additional agenesis of corpus callosum was present. Pachygyric brains showed a six-layered cortex, periventricular heterotopias, lacking differentiation of the claustra, but no cerebello-olivary anomalies. Cytoarchitectonic analysis of the agyric cortex suggests a disorder of neuronal migration during stage III of neocortex formation (Rakic and Sidman) between the 11th and 13th fetal week, while the pachygyric cortex showing the later formed layers II and IV presumable is caused by an attenuated and later disorder acting in early stage IV of neocortex formation, i. e. around or after the 13th fetal week. Additional insula-claustrum dysplasia, olivary and cerebellar anomalies are due to concomittent migration disorders between the 11th and 14th week. Along this period there is a gradient from agyric to normal six-layered cortex, whereas microgyria presumably results from an event occurring after migration has terminated (after the 16th fetal week). Etiological factors of agyria-pachygyria may be both hereditary (familial lissencephaly-syndrome) and environmental ones (prenatal drug application or intrauterine perfusion disorders).
Lissencephaly is a rare congenital malformation of the brain that has characteristic radiographic and clinical findings. Fifteen cases of lissencephaly were studied with CT and/or MR, and a classification was developed based on these cases and the description of this abnormality found in the literature. These findings can be divided into two groups, primary and secondary. The primary findings consist of (1) a cerebral surface that is agyric or agyric with pachygyric areas, (2) a cerebral contour that is oval or "hourglass" due to lack of or incomplete opercularization of the brain, and (3) an abnormal gray-white-matter distribution in the cerebral hemispheres. The primary findings are necessary to make the diagnosis, which can be made with either CT or MR; however, MR provided better delineation than CT of the cerebral surface and contour as well as better gray-white-matter differentiation in the lissencephalic brains. We believe MR is the technique of choice for evaluating patients with lissencephaly because it is safer and more versatile than CT and provides better delineation of the brains of children.
Neuronal migrational disorders of the brain represent abnormalities in the formation of the neocortex caused by faulty migration of the subependymal neuroblasts. These migrational anomalies include lissencephaly (agyria/pachygyria), pachygyria, schizencephaly, heterotopias, hemimegalencephaly, and polymicrogyria. We used MR imaging (performed on a 0.5-T or 1.5-T scanner) to evaluate 21 patients who had neuronal migratory anomalies. Four patients had lissencephaly, seven had pachygyria, including one patient with hemimegalencephaly, seven had schizencephaly, and three had heterotopias. All MR scans included T1-weighted spin-echo sequences, and seven also had inversion-recovery sequences. The cortical surface, cortex, and gray-white matter interface were well evaluated with both sequences; however, the inversion-recovery images were superior. All but two patients were imaged in both the axial and coronal planes: both projections demonstrated well the migrational abnormalities. MR is an excellent method for diagnosing the migrational anomalies of lissencephaly, pachygyria, schizencephaly, heterotopias, and hemimegalencephaly; it appears to be the imaging method of choice for evaluating these disorders.
Craniocerebral malformations remain enigmas to many radiologists because their pathogeneses are obscure, noninvasive imaging modalities could not display them in detail until recently, and concise classifications have been lacking. In this article the MRI findings of the most common congenital brain malformations are presented with an emphasis on the characteristic features of each malformation and the clinical symptoms and course.
Detailed clinical, pathological, and cytogenetic investigations of patients with lissencephaly over the past several years have demonstrated the existence of at least eight distinct conditions with variable genetic implications. In several of these disorders, especially chromosomally normal MDS, ILS, and CCL, too few patients have been reported to permit citation of accurate recurrence risk figures. Accordingly, we wish to begin a registry of patients with lissencephaly of all types for the purpose of developing such risk figures and request that any available information be sent to one of us (W.B.D. or J.M.O.).
A patient with the typical craniofacial features and clinical course of Miller-Dieker syndrome (MDS) was found on autopsy to have focal pachygyria rather than lissencephaly. The brainstem and cerebellum were hypoplastic, but thalami and basal ganglia were normal. We believe that MDS is a syndrome in which multiple specific pathways of neuronal migration are affected selectively, such as migration to the neocortex, migration via corpus pontobulbare, and cerebellar migration. However, another migration pathway (via corpus gangliothalamicum) is spared.
Four unrelated patients who had the clinical appearance of Miller-Dieker syndrome, also called lissencephaly syndrome, were studied. All four had a typical clinical course with failure to thrive, severe psychomotor retardation, opisthotonos, seizures, and death early in life. None of these children had lissencephaly, the anticipated central feature of this disorder. One of the four had pachygyria, one had polymicrogyria, and two had both pachygyria and polymicrogyria. The brain weights were normal to decreased. The ventricles were dilated in all cases. The cerebral cortex was thickened in each, with decreased white matter and diminution or distortion of the cellular layers, and there were neuroglial heterotopias. The corpus callosum was partially absent in one and thinned in three. The neuropathy found in these children with Miller-Dieker syndrome suggests a spectrum of gyral anomalies resulting from a single type of embryonic error.
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