最新:脑积水Hydrocephalus文档资料.ppt
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1、Overview of CSF production,The CSF volume of an average adult ranges from 80 to 160 mlThe ventricular system holds approximately 20 to 50 ml of CSFCSF is produced in the choroid plexuses at a daily rate of 14-36 ml/hr,Overview of CSF production,The choroid plexuses are the source of approximately 80
2、%of the CSFThe blood vessels in the subependymal regions,and pia also contribute to the formation of CSF,Overview of CSF circulation,The CSF flows from the lateral ventricles downward to the foramina of Magendie and Luschka,to the perimedullary and perispinal subarachnoid spaces,and then upward to t
3、he basal cistern and finally to the superior and lateral surfaces of the cerebral hemispheres,CSF circulation,The pressure gradient is highest in the lateral ventricles and diminishes successively along the subarachnoid spaceArterial pulsations in the choroid plexuses help drive the fluid from the v
4、entricular systemNormally,the periventricular tissues offer little resistance to the flow of CSF,+,-,CSF pressure,The CSF volume and pressure are maintained on a minute to minute basis by the systemic circulationCSF pressure is in equilibrium with capillary pressure(determined by the arteriolar tone
5、),An increase in blood PCO2(hypoventilation)decreases pH and arteriolar resistance,this in turn gives rise to increased CSF pressure by increasing cerebral blood flowHyperventilation has the opposite effect,CSF pressure,Normal intracranial pressure(ICP)in an adult is between 2-8 mmHg.Levels up to 16
6、 mmHg are considered normalICP higher than 40 mmHg or lower BP may combine to cause ischemic damage,CSF pressure,Increased venous pressure has a direct effect on CSF pressureDownstream block of venous flow increases the volume of cerebral veins,dural sinuses,and the subarachnoid space,The function o
7、f the CSF,The CSF acts as a“water jacket”for the brain and spinal cordThe 1300 g adult brain weighs approximately 45 g when suspended in CSF,The function of the CSF,The CSF acts like a“sink”,effectively flushing waste products as new fluid is secreted reabsorbedA constant CSF electrolyte composition
8、 helps maintain a stable medium for excitable cells(neurons),Mechanisms of increase intracranial pressure,Brain,Blood and CSF are held in an inelastic container(cranium,vertebral canal and dura)Changes in volume of either element(Brain,CSF,Blood)is at the expense of the other two,HydrocephalusCommun
9、icating vs.Non-communicating(Dandy),This is an old classification of hydrocephalusThe terms refer to the presence or absence of a communication of the lateral ventricles with the spinal subarachnoid space,Communicating vs.Non-communicating,This classification was based on the imaging findings after
10、injection of dye into the ventricular system and simultaneous injection of air into the subarachnoid spaceDiffusion of dye into the subarachnoid space and passage of air into the ventricular space were the criteria for communicating hydrocephalus,Non-communicating hydrocephalus,There is no communica
11、tion between the ventricular system and the subarachnoid space.The commonest cause of this category is aqueduct blockage or stenosis.,Aqueductal stenosis,The normal aqueduct measures about 1 mm in diameter,and is about 11 mm in length.,Aqueductal stenosis,Is the most common cause of congenital hydro
12、cephalus(43%)Aqueduct develops about the 6th week of gestation M:F=2:1 Other congenital anomalies(16%):thumb deformitiesPrognosis:11-30%mortality,Etiology of aqueductal stenosis,Intrinsic Pathology of the AqueductSeptum or Membrane Formation:A thin membrane of neuroglia may occlude the aqueduct.It c
13、ommonly occurs caudally.There may be a primary developmental defect or it may follow granular ependymitis from intrauterine infections.This is the rarest of the types of narrowing.Forking of the Aqueduct:Typically,there are two channels seen in midsagittal plane unable to handle CSF volume.Most ofte
14、n seen with spina bifida.Gliosis of the Aqueduct:Usually of infectious origin showing a marked gliofibrillary response.The lumen is devoid of ependyma.Stenosis of the Aqueduct:Narrowed aqueduct without evidence of gliosis.This may have hereditary basis.,Etiology of aqueductal stenosis,Extrinsic Path
15、ology of the Aqueduct:Infectious.Abscesses.Neoplastic.Pineal tumors,brainstem gliomas,medulloblastoma,ependymoma.Vascular.AVM,aneurysm,Galen aneurysm.Developmental.Arachnoid cysts.,Clinical features of aqueductal stenosis,Obstructive hydrocephalus:presents with macrocephaly and/or intracranial hyper
16、tension.Parinauds syndrome.Inability to elevate eyesColliers sign.Retraction of the eyelids,Imaging of aqueductal stenosis,Ultrasonography can detect aqueductal stenosis in utero.,Sonogram,Imaging of aqueductal stenosis,CT and MRI.MRI is essential if third ventriculostomy is to be considered.,Treatm
17、ent of aqueductal stenosis,Treatment and ResultsRemove underlying cause of obstruction if possible.Third ventriculostomy as initial treatment of choice.VP shunt if technical reasons do not allow third ventriculostomy or if the child fails after ventriculostomy.Aqueductal stent can be placed if techn
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