Histopathological study of alobar holoprosencephaly. 1. Abnormal laminar architecture of the telencephalic cortex

Abnormal architecture of the telencephalic cortex was studied in six autopsy specimens of alobar holoprosencephaly by histopathological, electron microscopic and immunohistochemical methods. Several common abnormalities are described and their significance discussed. In all of the specimens, the cortices showed excessive thickness and abnormal lamination with a middle cellular layer and an external sparse layer, indicating disturbance of neuronal migration. Neurons of the external sparse layer were segmented into irregularly arranged groups, suggesting disturbance of tissue organization. In three specimens, the internal pyramidal layer contained numerous abnormal glomerular structures which consisted of fine dendrites and axons.

Histopathological study of alobar holoprosencephaly. 2. Marginal glioneural heterotopia and other gliomesenchymal abnormalities

Abnormalities of glial and mesenchymal elements were studied in six autopsy specimens of alobar holoprosencephaly by histopathological and immunohistochemical methods. Marginal glioneural heterotopia was observed in all of the specimens. It was most prominent in the prosencephalic base around the optic chiasm, and extensive in five specimens. The floor of the third ventricle was intermingled with excessive mesenchymal elements, and in three specimens the ventricular cavity was plugged by heterotopic nodules. In the cerebellum, dysplastic nodules were observed in two specimens. In the telencephalon, the marginal and subventricular layers were thickened. The pathological significance of these findings is discussed with their possible relationship to the pathomechanism of holoprosencephaly.

Developmental-stage-dependent radiosensitivity of neural cells in the ventricular zone of telencephalon in mouse and rat fetuses

Pregnant ICR mice were treated with single whole-body X-radiation at a dose of 0.24 Gy on day 10, 13, or 15 of gestation. Fetuses were obtained from mothers during 1 and 24 hours after irradiation. Pyknotic cells in the ventricular zone of telencephalon were counted in serial histological sections. Incidence of pyknotic cells peaked during 6 and 9 hours after irradiation in each gestation day group. Then, dose-response curves were obtained 6 hours after 0-0.48 Gy of irradiation. All three dose-response curves showed clear linearity in the dose range lower than 0.24 Gy. Ratios of radiosensitivity estimated from the slopes of dose-response curves in day 10, 13, and 15 groups were 1, 1.4, and 0.4, respectively. These demonstrated that ventricular cells in the day 13 fetal telencephalon were the most radiosensitive among the three different age groups. In order to confirm the presence of the highly radiosensitive stage common to mammalian cerebral cortical histogenesis, pregnant F344 rats were treated with single whole-body gamma-irradiation at a dose of 0.48 Gy on day 13, 14, 15, 17, or 19 of gestation. The incidence of pyknotic cells in the ventricular zone of telencephalon was examined microscopically during 1 and 24 hours after irradiation. The peak incidence was shown 6 hours after irradiation in all the treated groups, and the highest peak incidence was shown in day-15-treated group. The developmental stage of telencephalon of day 15 rat fetuses was comparable to that of day 13 mouse fetuses. Thus, the highest radiosensitivity in terms of acute cell death was shown in the same developmental stage of brain development, i.e., the beginning phase of cerebral cortical histogenesis, in both mice and rats.

Facial and neuroepithelial abnormalities in a neurological mutant with congenital hydrocephalus. A scanning electron microscope study

This investigation was carried out to determine the early structural abnormalities of the cephalic region in a genetic mutant of the rat characterized by prenatal aqueductal stenosis and hydrocephalus. The appearance of hydrocephalic and control embryos was examined on days 13-15 of gestation, and the structure and organization of the neuroepithelium and basal lamina were studied using scanning electron microscopy. In addition to some overall developmental delay, hydrocephalic embryos were characterized by abnormalities of forebrain and midbrain development, and eye and external ear anomalies. There were also associated defects of the midfacial region. The lateral cell surface of the neuroepithelium reflected the developmental delay of hydrocephalic embryos, and failed to undergo the morphogenetic cell-shaping changes seen in control embryos. There were also variations in the number of lateral cell-cell specializations as well as regions of neuroepithelial disorganization and occasional herniation into the mesenchymal compartment. The role of the neuroepithelial basal lamina and extracellular matrix in the development of these defects is considered.

Arhinencephaly. The spectrum of associated malformations

Eight cases are presented of arhinencephaly and its associated malformations, which included 2 examples of holoprosencephaly and 3 of agenesis of the corpus callosum. Additional features included cortical malformations, anomalies of the long tracts and of the optic pathway, cerebellar hypoplasia and dentato-olivary dysplasia. Each of these components covered a wide spectrum ranging in severity from extreme to minimal. Craniofacial dysmorphism, and cardiac, renal and endocrine disorders were present in some cases. Only 2 cases were associated with chromosomal abnormalities, 1 with trisomy 13, the other with partial trisomy 7(7q+). Of possible environmental factors, maternal diabetes was recorded in 1 case. While all cases can be classified into broad categories, the individual variations render each case apparently unique.

Atelencephalic microcephaly in a 21-week human fetus

Atelencephalic microcephaly, a rare and extreme disorder, is known morphologically by only six cases. Derivatives of the telencephalon are absent or dysplastic, while more caudal structures are normal or mildly deformed. A more extensive form, aprosencephaly, involves structures of the diencephalon and may be associated with holoprosencephalic facies. Extracranial anomalies may be present in both atelencephaly and aprosencephaly. We describe the seventh and youngest specimen, a 21-week female with atelencephaly. Maternal and gestational histories were unremarkable; the fetus was obtained by therapeutic abortion following diagnosis of a severe cranial malformation by ultrasound. A small and depressed, but intact, calvarium covered the brain. The forebrain was rounded and showed fused hemispheres, absent gyri, olfactory bulbs, and tracts. Caudal structures were mildly deformed. An oval mass of bone filled much of the middle cranial fossa. By light microscopy, several dysplastic changes were apparent in the forebrain. Ventricles were not present; small round cells resembling those of the germinal matrix were prominent in the forebrain. Pyramidal tracts were absent at all levels. The process responsible for these changes cannot be established with certainty; the changes are, however, in keeping with previous damage, such as that accepted for other encephaloclastic disorders. The insult in atelencephaly presumably occurs after closure of the rostral neuropore; earlier damage, with more widespread consequences, is possible for aprosencephaly. As with other destructive processes, etiology in atelencephaly and aprosencephaly is most likely heterogeneous.

Midline telencephalic dysgenesis: report of three cases

A series of three complex cerebral malformations is presented. The series was characterized by incomplete development of the commissural and chiasmatic plate of the developing forebrain. Associated anomalies included hypoplasia of the hippocampus, heterotopias, and nonfusion of the cerebellum. Mild facial anomalies were present, as were somatic anomalies of the heart and kidneys. Emphasis is placed on the order and classification of similar cerebral anomalies.

Occurrence of cyclopia, myelomeningocele, deafness, and abducens paralysis in siblings

As holoprosencephaly without chromosome defect may be associated with other CNS-related anomalies such as mental retardation, mental illness, facial paralysis, endocrine disorders, deafness, spina bifida, and myelomeningocele, we present a family in which one girl had a myelomeningocele, a brother had orbital hypotelorism, facial and cerebral asymmetries, cerebral palsy, abducens paralysis, and inner ear deafness. A 3rd pregnancy was terminated at 16 weeks; the fetus had cyclopia. A common cause is discussed in these cases and in those families in which holoprosencephaly and additional malformations occur among different generations.

[Long term survival of holoprosencephaly with shunting procedure (author's transl)]

A long survived case of holoprosencephaly with hydrocephalus has been infrequently reported in the literature. One such case were presented on this report. This male baby by cesarean section because of his large head circumferenced 45 cm. He was admitted to our clinic diagnosed as congenital hydrocephalus at the third day from birth. On admission the circumference of his head was measured 49 cm, but other external malformations were not noticed. Right transaxillary carotid angiogram showed anterior cerebral artery appeared like azygos anterior cerebral artery. Absence of falx and fornix were suspected pneumoventriculography and transillumination of the head. Finally he was diagnosed as holoprosencephaly accompanied with hydrocephalus by computed tomography. Ventriculo-peritoneal shunt was performed at the 22nd day of his life. On follow-up after discharge, mental and motor development was not so poor. He was able to speak a few of simple words one year after discharge. At present 4 years and 6 months after discharge, he can do simple conversation and walk with assistance. Repeated computed tomography shows the frontal cerebral mantle is thickening in 36 mm at present. Good resulted case of holoprosencephaly as presented here could not be found in the literature. The pathogenesis and treatment were also discussed here.

Different teratogenic efficacy to mouse fetal CNS of 5-azacytidine in combination with X-irradiation depends on the sequence of successive application

The single treatment of pregnant mice on day 12 post conception with 5-azacytidine (AzaCr), followed by a single irradiation dose of 200 rad two hours later, is exclusively neurotoxic to the fetus, as shown by a severe hypoplasia of the parieto-occipital regions of the telencephalon. This effect is explicable by the specific function of the mitotic cell population for the integrity of the cortex wall. Combining these two hazards in the reverse manner, i.e., irradiation followed by AzaCr, resulted in no general hypoplastic effect in the forebrain and only caused a depletion of cells in the marginal cortex. This indicates a significantly diminished AzaCr sensitivity of fetal cortical cells subsequent to X-irradiation. In addition, rosette-like cell clustering in the cortex of all X-irradiated animals occurs to a similar degree, irrespective of any additional AzaCr-treatment. The only conformity between these different schedules is that a great portion of the surviving cells is most likely in the DNA synthesizing phase at the time of irradiation. It is therefore concluded that rosette formation starts perferentially from cells injured during the S-phase.

Atelencephaly

A 13 1/2-month-old boy with severe microcephaly was found to have nearly total absence of the telencephalon. The patient had marmorated skin, hypoplastic penis and undescended testes. Spastic tetraparesis was present. Moro, grasp and sucking reflexes were easily elicited. He could not sit or stand, but was able to raise and support his head. He had occasional convulsions and a tendency to hypothermia and vomiting. The EEG showed symmetrical low-voltage theta-delta activity. His psychomotor development was severely retarded. Bone age was normal. Head circumference was 28cm at six months and did not increase after this age. At autopsy the small cranial vault and meninges were found to be intact. Brain weight was 105g. The supratentorial part of the brain was extremely small, consisting of an irregularly lobulated mass about 3cm in diameter and without any median fissure or ventricular cavity. The telencephalon was severely involved and partly replaced by gliomesenchymal scar tissue, while the diencephalic structures, including the eyes and the optic nerves and chiasm, were comparatively well-developed. The cerebellum and brain stem were essentially intact.

Atelencephalic microcephaly

A two-month-old child born with marked microcephaly (head circumference 17cm) was found at autopsy to have gliomesodermal tissue replacing the telencephalon (atelencephaly). This finding, together with genital anomalies and hypoplasia of the extremities, suggests arrest at the fifth week of fetal life. The clinical and pathological features are described and the pathogenesis is discussed.

An unusual malformation of the forebrain and concomitant destructive encephalopathy with calcifications

A 9-year old boy with profound mental retardation and severe neurologic deficit presented an unusual malformation of the forebrain distinguished by the following features: 1) microtelencephalon, alobulation, afissuration, and abnormal convolutional pattern; 2) persistence of hippocampal formation at its embryonic site in the dorsomedial wall of the telencephalon; 3) hypoplasia and abnormal configuration of ventricles; 4) agenesis of cerebral commissures; and 5) abnormal location and orientation of gray structures. Important concomitant findings characterized by severe destructive lesions, massive calcification, granular ependymitis, and low grade inflammation were suggestive of late sequelae of an infectious process, possibly congenital. Transplacental transmission of an unidentified pathogen with teratogenic properties was hypothesized as the probable cause. The teratogenic insult started in an early embryonic period and affected primarily the development of the neopallium in the telencephalic wall. The arrested development of the neopallium disrupted the chain of interdependent developmental events; consequently characteristic morphological modifications normally induced by the continuous growth and differentiation of the neopallium failed to occur or took an abnormal course. The name architelencephalon (Greek: arche, beginning; telencephalon, cerebral hemispheres) proposed for this particular malformation of the forebrain indicates its resemblance both to the human brain at early stages of development and also to mammalian brains on a lower level of phylogeny. Associated anomalies included an unilateral microphthalmia with cataract, severe stenosis of the aqueduct of Sylvius and macrocephaly. The microphthalmia was either a developmental anomaly or was infectious in origin. The stenosis of the aqueduct was attributed to granular ependymitis. Tearing of the thin dorsal diencephalic plate and arachnoid membrane and escape of the cerebrospinal fluid into the subdural space probably accounted for the macrocephaly.

The effect of hyperthermia on the neuroepithelium of the 21-day guinea-pig foetus: histologic and ultrastructural study

Hyperthermia was induced in guinea-pigs on day 21 of gestation by placing them in an incubator set at 42-5 degrees-43-0 degrees C for 1 hr. At intervals thereafter foetuses were removed from the uterus and sections of the telencephalon were prepared for light and electron microscopy. The histologic and ultrastructural appearance of the telencephalon of the normal 21-day guinea-pig foetus was described for comparative purposes. Damage to cells in mitosis characterised by clumping of chromosomes, and dispersal of polysomes in interphase cells were observed immediately after hyperthermia. Breakdown of the network of junctional complexes was apparent at 4 hr and cellular proliferation was inhibited for 6-8 hr. Degenerative changes and cell deaths were observed deep in the venticular zone after 8 hr; the extent of cell death was related to the post-stressing temperature. Proliferation was resumed at 8 hr and damaged and dead cells moved outward toward the intermediate zone. Phagocytosis of debris by large mononuclear cells was a common finding. Cytoplasmic inclusions, some of which were Feulgen-positive, were present in otherwise normal ventricular cells. Occasional dead cells and empty spaces were present in the ventricular zone at 24 hr and by 48 hr the ventricular zone was normal in appearance. It was concluded that previously observed micrencephaly in the offspring of guine-pig mothers which were heat stressed on day 21 of gestation resulted from a temporary cessation of proliferation and partial depopulation of the proliferating neuroepithelium.