NEURO

• notochord induces overlying ectoderm to differentiate into neuroectoderm and form neural plate
• notochord becomes the nucleus pulposus
• neural plate becomes neural crest cells and neural tube
• lateral wall of neural tube divides into alar and basal plates
• alar is sensory and induces by bone morphogenic proteins
• basal is motor and induced by sonic hedgehog
• paraxial mesoderm forms somite, sclerotome (vertebrae), dermatome (skin) , myotome (muscle)
• somites are formed from paraxial mesoderm
• Neural plate


  from neuroectoderm
• Forebrain (prosencephalon)


  • Telencephalon
  • Diencephalon
• Hindbrain (rhombencephalon)


  • Metencephalon
  • Myelencephalon
• Neuroepithelia in neural tube

  Give rise to CNS neurons, CNS glial cells (astrocytes, oligodendrocytes, ependymal cells)
• Neural crest


  Give rise to PNS neurons (dorsal root ganglia, autonomic ganglia [sympathetic, parasympathetic, enteric]), PNS glial cells (Schwann cells, satellite cells), adrenal medulla
• Mesoderm


  Gives rise to microglia
• Diencephalon forms thalamus hypothalamus and retina
• Telencephalon gives the cerebral hemispheres and the basal ganglia
• Lateral ventricles develop from the telencephalon
• the third ventricle develops from the diencephalon
• Mesencephalon gives the midbrain and the cerebral aqueduct
• rhomboncephalon gives the metencephalon and the myelencephalon
• metencephalon gives the pons and the cerebellum and the upper part of the 4th ventricles
• myelecenphalon gives the medulla and the lower part of the 4th ventricle
• neural tube defect is due to failure of the neural tube to close by week 4 due to maternal folate deficiency and it is diagnosed by ultrasound and maternal AFP
• spina bifida occulta is a closed NTD the dura is intact no herniation and it is associate with dimpling and tuft of hair at affected level
• Meningocele is an open ntd and only meninges herniate
• meningomyelocele is an open ntd and the meninges and cauda equina herniate
• myeloschisis open ntd exposed unfused neural without skin covering
• Holoprosencephaly is a disorder where prosencephalon fails to divide into 2 cerebral hemispheres . associated with SHH mutation. occurs during weeks 3-4. Associated with trisomy 18 trisomy 13 and fetal acohol syndrome. Symptoms; cyclopia poboscis and hypotelorism cleft palat mono ventricle and fused basal ganglia and pituitary dysfunction
• lissencephaly is due to failure of neuronal migration
• lissencephaly presents with microcephaly seizurs dysphagia and facial anomalies and lack of sulci and gyri
• Idiopathic intracranial hypertension increased icp without finding on imaging associated with females obesity vitamin a excess tetracyclin danazol

  lumbar puncture reveals increased opening pressure and provides headache relief tinnitus diplopia and normal cognition headache

  decreased visual aquity due to cranial nerve 6 palsy impaired optic nerve axoplasmic flow causes papilledema increased blind spot

  treated with acetezolamid weight loss and surgical intervention csf shunt placement or optic nerve sheath fenestration surgery for visual loss