DEVLOPMENT OF BRAIN AND IT'S CONGENITAL ANOMALIES

NEUROSCIENCEGUIDED BY :- DR.S.D.TRIPATHI.SIR

SUBMITTED BY:-MR.SAURABH ASHOKRAO JADHAV

INTRODUCTION

• Neural development refers to the processes that generate, shape, and reshape the NERVOUS SYSTEM of animals, from the earliest stages of Embryogenesis to Adulthood.

• It is NeuroEctodermal in Origin• Brain is develop from anterior end of neural tube

FORMATION OF NEURAL TUBE

Left lateral views and sections through the developing brain. A, The three primary brain vesicles. B, Development of telencephalon and diencephalon.C, Development of the metencephalon and myelencephalon

PRIMARY BRAIN VESICLES & THEIR SUB DIVISIONS

A-Midline longitudinal section through the fore-brain showing the medial wall of the right cerebral hemisphere and the right thalamus and hypothalamusB-Cross-section through the fore-brain at the level indicated, Xshowing the lateral ventricles, the hippocampal lobes, the third ventricle and the choroid plexus

DEVELOPMENT OF PROSENCEPHALON

A- Midline longitudinal section through the fore-brain at a later stage B- Cross-section through the fore-brain at the level indicated, X. C- Cross-section through the fore-brain at the level indicated, Y.

A-Midline longitudinal section through the fore-brain in the early foetal period showing the relationships of thedeveloping brain structures.B-Cross-section at the level indicated, X.

DEVELOPMENT OF MESENCEPHALON

Development of the basal and alar plates in the mesencephalon. Section through the mesencephalon at an early stage of development, A, and at a later stage of development, B, showing the alar and basal plates, the wide neural canal and migration of cells from the alar plates (arrows). C, Section through the mesencephalon showing the reduced size of the mesencephalic aqueduct and the development of motor and sensory nuclei from the basal and alar plates. The crura cerebri are also shown. Sections are at the levels indicated.

DEVELOPMENT OF RHOMBENCEPHALON

A-Dorsal views and cross-sections at the levels indicated through the myelencephalon andB- the developing cerebellum and pons

Dorsal view and longitudinal section of the developing cerebellum showing the commencement of surface folding

Left lateral view and longitudinal section of the developing cerebellum showing marked folding of the surface, the formation of folia.

A CONGENITAL MALFORMATION IN CALVES; THERE IS A SMALL OPENING ON THE SURFACE OF THE CALVARIA; THE HOLE CONNECTS WITH A DEFORMED DIENCEPHALON WHICH MAY DISCHARGE CEREBROSPINAL FLUID

CONGENITAL ANOMALIES OF BRAIN

HYDROCEPHALUS,an increase in volume of the CSF, can appear similar to hydranencephaly, but in hydrocephalus the ventricles retain a complete ependymal lining. Clinical signs can vary from mild to severe and include seizures, lethargy, or other forebrain abnormalities. There may be extensive expansion of the lateral ventricles in the frontal lobes. Hydrocephalus is seen sporadically in all large animals, although it is relatively common in calves, in which inheritance and vitamin A deficiency have been implicated.

Holoprosencephaly is a disorder caused by the failure of the prosencephalon (the embryonic forebrain) to sufficiently divide into the double lobes of the cerebral hemispheres. ... Lobar, in which there is considerable evidence of separate brain hemispheres, is the least severe form.

Cerebellar hypoplasia is most frequently found in kittens and calves. The most common cause is prenatal or perinatal viral infections.

CEREBELLAR HYPOPLASIACerebellar hypoplasia (fig. describes a situationwhere an insufficiency of neurons causeshypoplasia of the granular layer of the cerebellum.In severe cases, the Purkinje neurons will also bedestroyed. The condition is most frequently foundin kittens and calves, most commonly caused byprenatal or perinatal viral infections. The specificviruses are the feline panleukopaenia virus and thebovine virus diarrhoea (BVD) virus.

CEREBELLAR ABIOTROPHYCerebellar abiotrophy is characterized by the degenerationof the Purkinje cells in the already formedcerebellar cortex. It occurs postnatally or, occasionally,prenatally and has been observed in manydomestic species. The primary defect that causes thedegeneration is not known.

ARNOLD-CHIARI MALFORMATIONArnold-Chiari malformation is a condition characterizedby caudal displacement and herniation ofcerebellar structures through the foramen magnuminto the cranial cervical vertebral canal. Arnold-Chiari malformation is often accompanied by spinabifida, meningomyelocoele, and hydrocephalus.

EXENCEPHALYFailure in the closure of the rostral neuropore, resulting in abnormal fore-brain development and interference with fusion of the bones of the cranium, gives rise to the condition referred to as exencephaly.When the cranial defect is small, the meninges can herniate and theanomaly is referred to as cranial meningocoele. A largecranial defect, which allows the meninges and part ofthe brain to herniate, is referred to as encephalocoele.

MICROCEPHALYMicrocephaly, an abnormally small brain, hasbeen reported in calves, lambs, and piglets. Since thesize of the cranium depends on the development ofthe brain, the cranial vault is considerably smallerthan normal. External features of microcephalyinclude a narrow and flattened frontal area of thecranium. Cranial bones appear thicker than normal.The cause of the condition may be genetic or aprenatal insult such as an infection or exposure toa teratogen.

HYDRANENCEPHALYIn hydranencephaly, the cerebral hemispheresare replaced by two fluid-filled sacs. The brainstem is usually not affected, but some degree ofcerebellar hypoplasia may be observed. In domesticanimals this condition is most commonly caused byan in utero viral infection (blue tongue virus inruminants and panleukopaenia in cats) or, morerarely, by an interruption of the blood supply to thetelencephalon.

DICEPHALIC (˘MUITIPLE MALFORMATION)Two-headed animals (called bicephalic or dicephalic) they are monozygotic twin embryos.

MENINGOCELE AND LIPOMENINGOCELE

Meningocele typically causes mild problems with a sac of fluid present at the gap in the spine. Myelomeningocele, also known as open spina bifida, is the most severe form. Associated problems include poor ability to walk, problems with bladder or bowel control, hydrocephalus, a tethered spinal cord, and latex allergy.

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