Maple syrup urine disease in an infant with microgyria

Malformations of cortical development: clinical features and genetic causes

Malformations of cortical development are common causes of developmental delay and epilepsy. Some patients have early, severe neurological impairment, but others have epilepsy or unexpected deficits that are detectable only by screening. The rapid evolution of molecular biology, genetics, and imaging has resulted in a substantial increase in knowledge about the development of the cerebral cortex and the number and types of malformations reported. Genetic studies have identified several genes that might disrupt each of the main stages of cell proliferation and specification, neuronal migration, and late cortical organisation. Many of these malformations are caused by de-novo dominant or X-linked mutations occurring in sporadic cases. Genetic testing needs accurate assessment of imaging features, and familial distribution, if any, and can be straightforward in some disorders but requires a complex diagnostic algorithm in others. Because of substantial genotypic and phenotypic heterogeneity for most of these genes, a comprehensive analysis of clinical, imaging, and genetic data is needed to properly define these disorders. Exome sequencing and high-field MRI are rapidly modifying the classification of these disorders.

Polymicrogyria: a common and heterogeneous malformation of cortical development

Polymicrogyria (PMG) is one of the most common malformations of cortical development. It is characterized by overfolding of the cerebral cortex and abnormal cortical layering. It is a highly heterogeneous malformation with variable clinical and imaging features, pathological findings, and etiologies. It may occur as an isolated cortical malformation, or in association with other malformations within the brain or body as part of a multiple congenital anomaly syndrome. Polymicrogyria shows variable topographic patterns with the bilateral perisylvian pattern being most common. Schizencephaly is a subtype of PMG in which the overfolded cortex lines full-thickness clefts connecting the subarachnoid space with the cerebral ventricles. Both genetic and non-genetic causes of PMG have been identified. Non-genetic causes include congenital cytomegalovirus infection and in utero ischemia. Genetic causes include metabolic conditions such as peroxisomal disorders and the 22q11.2 and 1p36 continguous gene deletion syndromes. Mutations in over 30 genes have been found in association with PMG, especially mutations in the tubulin family of genes. Mutations in the (PI3K)-AKT pathway have been found in association PMG and megalencephaly. Despite recent genetic advances, the mechanisms by which polymicrogyric cortex forms and causes of the majority of cases remain unknown, making diagnostic and prenatal testing and genetic counseling challenging. This review summarizes the clinical, imaging, pathologic, and etiologic features of PMG, highlighting recent genetic advances.

A Golgi study of the cerebral cortex in Fukuyama-type congenital muscular dystrophy, Walker-type "lissencephaly," and classical lissencephaly

The cortical neuronal organization of the brain was studied and compared in three conditions. The neurons in the polymicrogyric cortex from a subject with Fukuyama-type congenital muscular dystrophy and from a child with ocular dysplasia (Walker-type lissencephaly) were large, irregularly aligned, and not completely mature. In the former condition, the abnormal neuronal arrangement was predominantly in the superficial cortex; in the latter both the superficial and deep cortex were involved. These two diseases may have a similar pathogenetic mechanism. In classical lissencephaly without evidence of other disease manifestations, the neurons were arranged in a radial pattern with heterotopia but no large neurons. The pathogenesis of these conditions is discussed.

Involvement of the central nervous system in congenital muscular dystrophies

Three children, two siblings and one unrelated child, with congenital muscular dystrophy with central nervous system (CNS) involvement are discussed. The siblings appeared to suffer from a relatively mild myopathy with progressive brain disease, of which brain biopsy in one showed astrocytic proliferation in the white matter. In the patient with severe muscle disease, autopsy showed widespread patchy demyelination in the white matter and developmental abnormalities in the cerebral and cerebellar cortex. These patients differ from the Japanese (Fukuyama) cases of CMD in the severity of the changes in the cerebral white matter, and from Santavuori's cases in the absence of ocular abnormalities and hydrocephalus. Their unique nosology is discussed.

Adrenoleukodystrophy. Preliminary report of a connatal case. Light- and electron microscopical, immunohistochemical and biochemical findings

This is the first description of a connatal case of adrenoleukodystrophy. The clinical picture consisted of severe psychomotor retardation, convulsions and hypsarrhythmia, but no obvious signs of adrenal insufficiency. Pathologically, the adrenals were small. The entire cortex was largely replaced by large round cells. Ultrastructurally, some cells in the adrenal cortex contained inclusions with electron-lucent clefts surrounded by a membrane. The anterior pituitary lobe could be demonstrated to have produced ACTH. The central nervous system showed extensive zones of demyelination in the brainstem, the cerebellum and the right-sided capsula interna. In the demyelinated areas there was sudanophilic breakdown and an intense gliosis. Ongoing demyelination could also be demonstrated by the chemical analysis. In the gray matter there waere micropolygyria of the insular cortex and swollen nerve cells in the nucleus arcuatus. Ultrastructure revealed the type of inclusions in the microglia of the same type as in the adrenals, and a different type of inclusions in unidentifiable cells, possibly neurons. These latter inclusions consisted of loosely stacked lamellar material. The findings are interpreted as further evidence of storage taking place in this disease.

Cerebral malformation associated with metabolic disorder. A report of 2 cases

A clinical and neuropathological study is presented of two cases each of which showed neuronal heterotopia. Microgyria was also present in one case. One patient was suffering from a degenerative disorder affecting the white matter. The other was a case of Menkes' disease. It is suggested that the antenatal damage may have been caused by an imbalance of the maternal metabolism, the predisposing factor being the mother's carrier state for a metabolic defect. This is the first report of teratogenesis in a case of Menkes' disease. It is also noted that in this case there is interference with the postnatal as well as the antenatal development of the brain.

Patterns of decerebration in infants and children: defects in homeostasis and sequelae

Sixty-four infants and children showing signs of decerebrate rigidity admitted to a paediatric unit have been studied. Cases of head injury, myelomeningocoele, and tumours were excluded from the series. The aetiological factors causing decerebration in the remainder fell into four main groups: infections, hypoxia, metabolic disease, and intracranial haemorrhage. Increased intracranial pressure was diagnosed in 87%. Defects in homeostasis occurred in 75%, respiratory abnormalities were present in 66%, cardiovascular in 33%, hypothermia in 30%, and hyponatraemia in 17%. Early recognition and treatment of raised intracranial pressure and defects in homeostasis are of the utmost importance if morbidity and mortality are to be minimized. There was a 31% mortality from the acute illness: 30% of the survivors were normal at follow-up examination; the remainder showed varying degrees of handicap. The severity of decerebration showed no correlation with aetiology or prognosis. The study shows that a wide range of disorders can lead to the clinical picture of decerebration in the young child, and that the prognosis is probably much better than in adults showing the same symptoms and signs.