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Cns path congenital, edema
 

Cns path congenital, edema

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    Cns path congenital, edema Cns path congenital, edema Presentation Transcript

      • Congenital Malformations
      • Development of CNS proceeds according to
      • a precise schedule
      • a) each morphological event is cornerstone for those that follow
      • i) myelination initiated late in embryonic development
      • ii) only after cellular differentiation and migration
      • iii) congenital anomalies reflect interruptions in the completion of critical developmental processes
      www.freelivedoctor.com
      • Neural tube defects (dysraphic states)
      • reflect impaired closure of the dorsal aspect
      • of vertebral column
      • a) Spina Bifida
      • i) most common in lumbosacral region. Further classified according to extent of defect
      • - Spina bifida acculta: restricted to vertebral arches, usually asymptomatic small tuft of hair or dimple
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        • - Meningocele: more extensive bony and soft tissue defects. Protrusions of meninges as fluid filled sac. Lateral aspects covered by skin, apex is ulcerated
        • - Meningomyelocele: More extensive defect with spinal cord flattened
        • - Rachischisis: extreme defect, spinal column converted into gaping canal
        • ii) Pathogenesis
        • - induced at 8-9th gestational day in experimental animals (rats and chicks) by chemicals (trypan blue,  vitamins)
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    • - maternal folic acid deficiency - other potential associated malformations include: 1. Arnold-Chiari Syndrome 2. Hydrocephalus 3. hydromyelia 4. polymicrogyria b) Anencephaly i) congenital absence of part or all brain ii) is second in incidence to spina bifida iii) concurrent with spina bifida www.freelivedoctor.com
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      • iv) highly vascularized, poorly differentiated
      • - “cerebrovasculosa”, lies on flattened base of the skull
      • Spinal Cord Malformations
      • Uncommon congenital disorders include:
      • a) duplications (rare)
      • i) complete (dimyelia)
      • ii) partial duplications into 2 separate structures (diastematamyelia)
      • b) hydromyelia
      • i) dilation of central canal of spinal cord
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    • c) Syringomyelia i) tubular cavitation (syrinx) which extends for variable distances along entire length of spinal cord - may or may not communicate with central canal ii) usually encountered in adults - many cases thought to represent congenital malformation iii) causes relate to trauma, ischemia,tumors iv) motor and sensory deficits anatomical location in spinal cord www.freelivedoctor.com
      • d) syringobulbia
      • i) variant of syringomyelia
      • ii) slit like cavities located in medulla
      • Arnold-Chiari Malformation
      • Involves medulla and cerebellum
      • a) brainstem and cerebellum compacted into bowl-shaped posterior fossa
      • b) often associated with syringomyelia or
      • c) lumbar meningomyelocele
      • d) symptoms depends on severity of defect
      • e) Pathogenesis:
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    • i) may occur when meningomyelocele anchors lower end of spinal cord - causes downward growth of spinal cord and - creates traction on medulla ii) curvature of medulla iii) breaking of quadringeminal plate iv)  intracranial pressure associated with hydrocephalus f) Pathology: i) caudal aspect of cerebellar vermis is herniated through an enlarged foramen magnum www.freelivedoctor.com
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      • Dandy-Walker Malformation
      • Enlarged posterior fossa
      • Cerebellar vermis is absent or only in
      • rudimentary form
      • a) in its place is a large midline cyst
      • Dysplasias of brain stem nuclei are common
      • Hydrocephalus
      • Congenital hydrocephalus
      • a) excessive amount of CSF
      • b) enlarged ventricles
      • c) congenital atresia of the aquaduct of Sylvius is most common cause
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      • i) 1 in 1000 live births
      • d) other causes
      • i) aqueduct narrowing by gliossis
      • - may be caused by transplacental transmission of viruses that induce ependymitis
      • Noncommunicating hydrocephalus
      • a) portion of ventricular system is enlarged
      • i) e.g., mass in 3rd ventricle
      • Communicating hydrocephalus
      • a) enlargement of entire ventricular system
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      • Communicating hydrocephalus
      • a) impairment of reabsorption
      • Hydrocephalus
      • a) hemispheres are enlarged
      • b) ventricular system is dilated
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      • Hydrocephalus ex vacuo
      • a) dilation of ventricular system with  CSF volume secondary to loss of brain parenchyma
      • Disorders of Cerebral Gyri
      • Frequently associated with mental
      • retardation
      • a) polymicrogyria
      • i) presence of small and excessive gyri
      • b) pachygyria
      • i) gyri  in # and usually broad
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    • c) lissencephaly i) cortical surfaces are smooth or imperfectly formed gyri d) heterotopias i) focal defects that lead to modules of ectopic neurons ii) mental retardation iii) may be caused by maternal alcoholism www.freelivedoctor.com
      • Chromosome Abnormalities
      • Associated with congenital defects
      • a) derrangements in autosomes 1-12
      • i) incompatible with life
      • ii) spontaneously aborted
      • b) Down Syndrome
      • i) trisomy 21
      • - mental retardation
      • - distinct facial features, etc.
      • ii) mild cerebral atrophy
      • iii) patients often develop Alzheimer disease pathology by 4th decade
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    • c) Trisomy 13-15 i) Holoprosencephaly - microcephalic brain - absence of corpus collusum - absence of interhemispheric fissure - rarely compatible with life beyond a few weeks ii) arhinencepahaly - absence of olfactory tracts and bulbs (rhinencephalon) - associated with holoprosencephaly or as solitary lesion www.freelivedoctor.com
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      • Cerebral edema, raised ICP and herniation
      • Brain and spinal cord exist in rigid
      • compartment
      • Cerebral edema
      • a) brain parenchymal edema may occur in a variety of conditions
      • i) vasogenic edema
      • - BBB disruption, resulting in increases in permeability
      • - may be focal or generalized
      • ii) cytotoxic edema
      • - increase intracellular volume
      • (hypoxia/ischemia inhibiting active pumps)
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      • b) Interstitial edema (i.e., hydrocephalus)
      • i) occurs around lateral ventricles
      •  ICP
      • a)  mean CSF pressure greater than 200 mm H 2 O with patient recumbent
      • i) most occur with mass effect
      • b) if severe enough will cause brain to displace where herniation may occur
      • i) subfalcine (cingulate) herniation
      • - asymmetric expansion of cerebral hemisphere displaces cingulate gyrus under the Falx cerebri
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    • - may be associated with compression of branches of the anterior cerebral artery ii) transtentorial (uncinate) herniation - medial aspects of temporal lobe is compressed against tentorium cerebelli - 3 rd cranial nerve is compressed - pupillary dilation and ocular movement impairment on side of lesion www.freelivedoctor.com
    • - progression of this type of herniation  hemorrhages in pons and midbrain (Duret hemorrhages) - may result from the tearing of penetrating veins and arteries supplying upper brainstem iii) tonsilar herniation - displacement of cerebellum (tonsils) through foramen magnum - this type of herniation is life threatening ( compression of brainstem - - CV and resp centers) www.freelivedoctor.com
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      • CNS TRAUMA
      • Epidural hematoma
      • a) accumulation of blood between calvaria and the dura
      • i) usually results from a blow to the head
      • - if not quickly treated, is generally fatal
      • Pathogenesis:
      • a) dura securely bound to inner aspect of Calvaria (analogons to periosteum)
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    • b) middle meningeal arteries occupy space between dura and calvaria i) grooved into inner table of bone ii) branches across temporal-parietal area (mainly as 3 major vessels) c) temporal bone one of thinnest bones of skull i) vulnerable to fractures - minor trauma may cause fracture - and transect branches of middle meningeal artery  life threatening epidural hemorrhage www.freelivedoctor.com
      • Pathology:
      • a) blood escapes into epidural space
      • i) thereby separating dura from calvaria
      • - progressive enlargement of hematoma
      • b) asymptomatic for first 4-8 hours
      • c) when hematoma volume  30 to 50 ml
      • i) symptoms resemble space occupying lesion
      • ii) downward displacement of CSF
      • iii) if hematoma continues, ICP eventually exceeds cerebral venous pressure!
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    • - venous sinuses are compressed  cerebral ischemia (hypoxia)  - diffuse cortical impairment  confusion and disorientation d) ”Cushing Reflex” is protective response to  CBF and oxygenation i) HR  (increases filling) ii) myocardial contractility  iii) systolic BP  e) hematoma can  to ~60 ml i) after compensation is exhausted  ii) brain shifted laterally away from side of hematoma www.freelivedoctor.com
    • iii) medial temporal lobe compressed against midbrain  displaces it  through in tentorium  fatal event known as “transtentorial herniation” iv) 3rd nerve compression v) pupil fixed and dilated (same side) vi) further compression  further hypoxia and impairs neuronal function vii) damage to reticular formation  expressed clinically as decline in level of consciousness www.freelivedoctor.com
    • viii) shortly thereafter  hemorrhage and necrosis of brainstem  irreversible damage  death or irreversible coma f) epidural hematomas are progressive and if not treated, are fatal in ~4-48 hrs g) concussion i) transient loss of consciousness due to trauma ii) mainly to brainstems reticular formation - e.g., boxing “knock-out”  - deflects head up and posteriorly  www.freelivedoctor.com
    • - these motions import quick torque on brainstem and cause  functional paralysis of neurons of reticular formation iii) a blow to temporal-parietal area may cause skull fracture but does NOT generally cause a concussion - lateral movement of cerebral hemispheres is prevented by the Falx www.freelivedoctor.com
      • Subdural Hematoma
      • Reflects torn bridging veins in subdural space
      • a) major cause of death
      • i) falls
      • ii) assaults
      • iii) vehicular accidents
      • iv) sporting mishaps
      • Pathogenesis:
      • a) cerebral hemispheres tethered loosely by blood vessels and cranial nerves and float in CSF
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    • b) when brain impacts skull i) stationary head struck ii) moving head strikes object c) cause shearing effect in subdural space i) tears veins d) unlike epidural space, subdural space can expand i) since bleeding usually is from veins ii) usually stops spontaneously (i.e., bleeding) - with only ~ 25-50 ml - from local tamponade effect e) can compress veins  thrombosis f) usually bilateral www.freelivedoctor.com
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      • Pathology:
      • a) even if small can cause irritation
      • i) between hematoma and dura 
      • - leads to granulation tissue (several weeks)
      • - creates membrane above hematoma (i.e., outer membrane)
      • - fibroblasts form fibrous membrane
      • b) static subdural hematoma has 3 routes of evolution
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    • i) may be reabsorbed  only small amounts of residual hemosiderin ii) remain static with potential for  calcification iii) hemorrhage may enlarge (rebleeding, usually within 6 months) iv) granulation tissue is vulnerable to re-bleed (shaking of head) c) during genesis of subdural hematoma i) bridging vein severance is precisely located to the subdural space - compartmentalizes blood away from CSF www.freelivedoctor.com
    • - absence of blood in CSF does NOT negate presence of subdural hematoma d) clinical S & S: i) stretching meninges  headache ii) pressure on motor cortex  contralateral weakness iii) focal cortical irritation  seizures iv) bilateral subdural hematoma  cognitive dysfunction - misdiagnose as dementia v) rebleeding may cause transtentorial herniation www.freelivedoctor.com
      • Subarachnoid Hemorrhage
      • Any bleeding into subarachnoid space
      • Seen with traumatic head injuries
      • a) 2/3 of cases reflect rupture of pre- existing arterial aneurysm (discussed later)
      • b) 10% occur as AVM
      • c) remainder from variety of conditions
      • i) infections
      • ii) blood dyscrasias
      • iii) tumors
      • iv) vasculitis
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      • Cerebral Contusion
      • Traumatic bruise of the brain surface
      • a) usually result from anteroposterior displacement
      • i) similar to subdural hematoma
      • ii) severity corresponds to acceleration of head
      • b) lesion at point impact referred to as
      • i) coup injury (i.e., contusion)
      • - same side as impact
      • c) lesion (i.e., contusion) on opposite side as impact referred to as
      • i) counter coup contusion
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      • d) contusions are permanent (necrotic tissue)
      • i) phagocytized rapidly
      • Penetrating Wounds
      • In absence of injury to vital brain structures
      • immediate threat to life is hemorrhage
      • a) lethal transtentorial herniation
      • b) herniation of cerebellar tonsils into foramen magnum
      • i) compression of medulla
      • - disabling CV and Resp. centers
      • Velocity contributes a blast effect to
      • projectile
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    • a) high velocity i) disrupts tissue by its own mass ii) centrifugal blast - enlarges diameter of cylinder causing disruption iii) can cause immediate death - explosive  in ICP, which  - herniates cerebellar tonsils into foramen magnum d) seizures are a threat in healed penetrating wounds i) 6-12 months after the trauma www.freelivedoctor.com
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      • Spinal Cord Injuries
      • Often lead to paraplegia or quadriplegia
      • a) direct injury via
      • i) penetrating injuries
      • - stab
      • - bullets
      • b) indirect
      • i) fractures
      • ii) displacement of vertebrae
      • c) trauma may complicate injury via  blood supply  necrosis
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      • Hyperextension vs. hyperflexion
      • a) vertebral bodies aligned by 2 longitudinal ligaments
      • i) anterior spinal ligament
      • ii) posterior spinal ligament
      • b) hyperextension injury
      • i) forehead struck from front and driven posteriorly
      • - diving head first into shallow water
      • - posterior displacement tears anterior spinal ligament
      • - cord damaged by posterior bony processes
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    • c) hyperflexion injury i) head or shoulders hit from behind - head driven forward - sharp forward angulation of spinal cord d) consequences of spinal cord injury vary i) concussion - mildest injury - transient and reversible of spinal cord function ii) contusion - more severe trauma ranging from  (minor transient bruise  hemorrhage) www.freelivedoctor.com
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    • - spinal cord necrosis and edema caused by contusion  myelomalacia hematoma within cord  hematomyelia iii) lacerations and transactions - usually produced by penetrating wounds - are irreversible - cause paralysis of lower limbs (paraplegia) - or quadriplegia (all 4 extemitites www.freelivedoctor.com
      • Circulatory Disorders
      • Vascular Malformations may lead to hemorrhage
      • AVM (ArterioVenous Malformations)
      • a) most common congenital vascular malformation
      • i) has greatest clinical significance
      • - seizures
      • - intracranial hemorrhages (subarachnoid)
      • - 2nd – 3rd decades
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      • b) typically seen in cerebral cortex
      • c) abnormal blood vessels replace cortical grey matter and extend deeply into white matter
      • d) defect enlarges with time  involves larger area
      • Cavernous angioma
      • a) less common than AVM
      • b) similar to cavernous angioma elsewhere
      • i) liver
      • c) formed by large, irregular, thin-walled vascular channels
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      • d) most are asymptomatic
      • i) may cause intracranial bleeding
      • ii) epilepsy or
      • iii) focal neurological disturbances
      • Telaigiectasia
      • a) focal aggregate of small vessels
      • b) may initiate seizures, but rarely rupture
      • Venous angioma
      • a) focus of few enlarged veins
      • b) distributed randomly in spinal cord and brain
      • c) usually asymtomatic and overlaps in past with cavernous angioma
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      • Cerebral aneurysms
      • Rupture and lead to fatal hemorrhage
      • a) result from  vascular pressure and weakened arterial wall
      • Causes:
      • a) developmental defects:
      • i) berry (saccular, medial defect)
      • b) atherosclerotic
      • i) produce mass effect
      • c) hypertension
      • i) associated with arteriolar lipohyalinosis and
      • ii) induces Charcot-Bouchard aneurysm
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    • d) bacterial infections i) leads to mycotic aneurysms e) trauma i) rarely caused dissecting aneurysms 1. Berry aneurysm a) consequence of arterial defects b) arise during embryogenesis i) when arteries bifurcate c) greater than 90% of sacular aneurysms occur at branch points in carotid system d) rupture results in life-threatening SAH i) ~35% mortality during initial hemorrhage www.freelivedoctor.com
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    • 2. Atherosclerotic aneurysm a) localized mainly in major cerebral arteries i) vertebral ii) basilar iii) internal carotid b) fibrous replacement of media and c) destruction of internal elastic membrane i) weakens arterial wall  aneurysm d) they are fusiform and elongate e) rarely rupture i) major complication is thrombosis www.freelivedoctor.com
      • 3. Mycotic aneurysm
      • a) infections of arterial wall
      • i) septic emboli (inflammation)
      • - usually from cardiac valve
      • b) may also cause cerebal abscess or meningitis
      • Cerebral Hemorrhage
      • Causes stroke (apoplexy)
      • a) hemorrhage without trauma are “spontaneous”
      • b) most are caused by vascular anomalies (aneurysms)
      • c) long standing hypertension
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    • i) occurs in preferential sites (order of frequency) - basal ganglia-thalamus (65%) - pons (15%) - cerebellum (8%) - Other causes of cerebral hemorrhage, independent of hypertension: AVM leakage, erosion of blood vessel by neoplasm, bleeding diathesis – (e.g., thrombocytopenic purpura), endothelial injury via microorganisms (e.g., ricketisiae), embolic infarction (hemorrhage into area of necrosis) www.freelivedoctor.com
    • d) compromises integrity of arterial wall by depositing i) lipid ii) hyaline material (i.e., protein) iii) i and ii known as “lipohyalinosis ” iv) weakening wall leads to Charcot- Bouchard aneurysm - located mainly along trunk of a blood vessel rather than at its bifurcation e) onset of symptoms is abrupt i) weakness usually dominates www.freelivedoctor.com
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    • ii) when hemorrhage is progressive - death within hours to days - as hematoma enlarges, may cause death via transtentorial herniation - may rupture into ventricle with massive hemorrhage  distension of 4th ventricle and compression of vital centers - Routine hemorrhage  catastrophic  loss of consciousness  damage to reticular formation – death prior to arriving at hospital www.freelivedoctor.com
      • - cerebellar hemorrhage  ataxia and severe occipital headache and vomiting
      • Cerebral Ischemia and Infarction
      • Major causes of stroke
      • a) global ischemia
      • i) cardiac arrest
      • ii) external hemorrhage
      • iii) thrombosis
      • - regional ischemia
      • iv) hypoxia
      • - near drowning, CO poisoning, suffocation
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    • 1. Global Ischemia a) pattern of injury reflects anatomy of cerebral vasculature i) Watershed infarcts: anterior, middle and posterior cerebral arteries perfuse overlapping territories - no anastamoses between their terminal branches - areas of overlap are therefore not perfused as well and infarcts (via global ischemia) occur in these “watershed areas” www.freelivedoctor.com
    • ii) Laminar necrosis : also reflects topography of cerebral vasculature - intraparenchymal pial vessels - penetrate at right angles and are deep penetrators into grey matter - more focal areas of ischemia iii) Selective neuronal sensitivity - Purkinje cells of cerebellum - pyramidal neurons of Sommer sector I hippocampus www.freelivedoctor.com
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      • - these are very sensitive areas to ischemial hypoxia
        • these neurons are more vulnerable and develop localized necrosis
        • 2. Regionsl Ischemia and Cerebral Infarction
        • a) atherosclerosis
        • i) occlusive disease
        • - major causes of M & M
        • ii) infarcts caused by embolyization are hemorrhagic
        • iii) infarcts initiated via thrombosis are ischemic (“bland”)
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        • b) infarcts via emboli (see ii) occlude flow abruptly  distal segment becomes necrotic and leak blood into region
        • c) thrombosis progresses slowly and gradually causing ischemia  guards against secondary hemorrhage
        • d) infarct transforms affected tissue into friable debris
        • i) eliminated by macrophages
        • ii) initially infracted surrounded by blood capillaries
        • iii) when infarcted area in phagocytized, remnant cystic cavity
        • iv) Liquefactive necrosis
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    • e) clinical outcome dependent on structures involved i) proximal and MCA occluded by atherosclerosis and thrombosis - resultant infarct transects internal capsule  hemiparesis or hemiplegia f) localized ischemia associated with 3 distinct clinical syndromes i) TIA (transient ischemic attack) - focal cerebral dysfunction last less than 24 hrs (usually only a few minutes in duration) - signifies risk for infarct www.freelivedoctor.com
    • ii) stroke in evolution - progression of neurological symptoms while patient is under observation - uncommon and usually reflects propagation of a thrombus in carotid or basilar artery iii) complete stroke - stable neurologic defects resulting from cerebral infarct www.freelivedoctor.com
      • 3. Regional Occlusive CVD
      • Classified into 5 categories (caliber and
      • nature of vessel)
      • a) large extracranial and intracranial arteries
      • i) frequently involved in atherosclerosis
      • - common carotid (at bifurcation of ECA and ICA)
      • - occlusion of ICA  ipsilateral hemisphere
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    • - occlusion of carotid artery produce infarcts (most often) to portions of distribution of the MCA b) Circle of Willis i) deficits depend on collateral circulation ii) MCA often occluded by thrombosis complicating atherosclerosis in circle of Willis www.freelivedoctor.com
    • c) Parenchymal arteries and arterioles i) rarely become atherosclerotic ii) damaged by hypertension iii) small lacunar infarcts iv) when occur in  numbers - multiple infarct dementia v) fibronoid necrosis (hypertensive encephalopathy) via malignant hypertension - minute hemorrhages (petechiae) www.freelivedoctor.com
    • d) capillary bed i) small emboli (fat or air) occlude capillary bed - petechiae most common in white matter e) cerebral veins i) venous sinus thrombosis is potentially lethal for the following: - systemic dehydration (e.g., infants with g.i. fluid loss) - phlebitis (mastoiditis or bacteremia) - obstruction by neoplasm - sickle cell disease www.freelivedoctor.com
      • CSF
      • Constitutes accessory circulatory system
      • a) produced mainly by choroids plexus
      • i) ~500 ml/day
      • ii) reabsorbed by arachnoid villi
      • Obstruction to flow of CSF is within the
      • ventricles, hydrocephalus is 
      • noncommunicating
      • a) congenital malformation
      • b) neoplasms
      • c) inflammation
      • d) hemorrhage
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      • Aqueduct of Sylvius is most common location
      • of obstruction (congenital malformation)
      • Viral ependymitis during embryogenesis may
      • result in congenital aqueduct stenosis
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