neurosurgery.Congenital anomalies of the cns,(dr.mazn bujan)
Congenital anomalies of the CNS DR.MAZIN M.K. BOUJAN 2011
INTRODUCTION• Phenotype: the outer look.• Genotype: the inner genetics.1.Malformation=genetic=organ formation.2.Deformity= environmental-Internal (more sever, no spontaneous recovery) e.g.: Meningomyelocele=spastic muscles=club feet.-External (might correct itself after the resolution of the force) e.g.: oligohydraminios(uterus force) leads to premature descent of the head and eventually coronal synostosis ).3. disruption: tissue or organ destruction.4. a sequence: one primary defect leads to many secondary anomalies.
Neuroembryology• Stages of embryonic development;• Human embryo has 23 stages of development (each of 2-3 days long).• Stage 8 to 23 is related to CNS development.
Normal CNS development• The three basic regions of the CNS (forebrain, midbrain, and hindbrain) develop at the rostral end of the tube, with the spinal cord more caudally.• Within the developing spinal cord specification of the different populations of neural precursors (neural crest, sensory neurones, interneurones, glial cells, and motor neurones).• *J Neurol Neurosurg Psychiatry 2003;74:i3-i8 doi:10.1136/jnnp.74.suppl_1.i3
Stages of CNS developmentStage Main feature8 Beginning of organogenesis.9 3 pairs of somites.10 Most important stage of brain development11 Upper neuropore closure.12 Lower neuropore closure.13 Entire neural tube closure.14 Cerebral hemispheres development.15 Thalamus and hypothalamus.16 Olfactory system.17 Cranial nerves.18-20 Frontal, temporal, and occipital lobes.21-23 cerebellum
1.Arachnoid cyst1.Intracranial:• Usually asymptomatic discovered incidentally.• Could be symptomatic.Symptoms: Increased ICP, seizure, or hemiparesis.Treatment: from shunting to excision. 2.intraspinal:almost always dorsal.
2.Neuroenteric cystsIs a CNS cyst lined by endothelium resembling GIT or respiratory.Intraspinal: is the main location, usually anterior.Intracranial: few reported cases.Symptom: pain or myelopathy, meningitis(fistula type).Treatment: complete removal.
3.Craniosynostosis.• Congenital early closure of the sutures.• Might occur postnataly by abnormal positioning (lazy lambdoid).• Has many types according to the suture involved. Most common are:• Sagittal=scaphocephaly.• Unilateral Coronal= plegiocephaly.• Bilateral coronal = brachycephaly.• Treatment: surgery is usually cosmetic.
4.Encephalocele• Is cranium bifidum usually a cyst in the occipital region.• If only contains meningies=meningocele.• If contain meningies and cerebral tissue = encephalocele.• Another group is called basal encephalocele appear at the base of the skull and could be mistaken for a nasal polyp.• Treatment: surgical excision and water-tight Dural suture.
5.Chiari malformationBasically 4 types:• Chiari I: caudal descent of the cerebellar tonsils to the cervical canal.• Chiari II: caudal descent of the vermis, medulla and the 4th ventricle.• Chiari III: rare, cerebellar herniation + encephalocele.• Chiari IV: cerebellar hypoplesia.• Treatment: surgical decompression of the posterior fossa.
6.Dandy-Walker Malformation• Atresia of foramen Magendie and luschka.• Agenesis of the vermis.• 4th ventricle communicated with a posterior fossa cyst.• Treatment: shunt the posterior fossa cyst.
8.Spinal dysraphism• Spina bifida: types;1. Spina bifida occulta: an incidental finding of loss of spinous process and lamina.2. Meningocele: 1+ cystic distention of the meningies.3. Myelomeningocele: 1+2+ spinal cord or cauda equina involvement.Treatment : for 2 and 3 repair.
9.Tethered cord syndrom• Thick filum terminale with an abnormal low level conus medularis.Presentation: Gait difficulty, visible muscle atrophy, sensory deficit, bladder dysfunction, scoliosis and kyphosis.Treatment: division of the filum.
10.Split cord syndrom• Type one: 2 cords with 2 covering dura.• Type two(diplomyelia):2 cords within the same dura.• treatment: untethering the cord
11.Intracranial lipoma• Usually in the midline above the corpus callosum.• Asymptomatic discovered incidentally.• might cause seizure or hydrocephalus.Treatment :• shunting the associated hydrocephalus.• Direct surgery is rarely necessary.
12.Hypothalamic hamartoma• Masses of ectopic neural tissues.Presentation:• seizure, behavioral disturbance, precocious puberty, mental retardation, and visual impairment.• Surgical resection.