The nervous system

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The nervous system
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Major differences

• between nervous system and other organ
  systems of the human body
• 1. Topographic localization - specific areas
  (cerebral centers) - even small focal lesion may
  cause selective severe dysfunction - variable
  neurologic deficits (dependent on location) -
  e.g. frontal cortex spinal cord
• 2. Protective mechanism
• - skull - protection from trauma vulnerability
  to intracerebral expansions, edema, etc.
• - CSF - protection can cause hydrocephalus

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• 3. Limited spectrum of pathologic responses to
  injury - e.g. glial response is similar in
  various lesions (infarction, trauma,
  degeneration)
• 4. Specific diseases - majority of pathologic
  processes are similar to other organs
  (infections, ischemia, etc.) - some disorders are
  specific to neural tissue (e.g. neurodegenerative
  processes)

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Cells of nervous system and their behaviour in
pathologic processes

• Neurons
• heterogenous family
• no postembryonic multiplication or regeneration
• most common - necrosis (nucleus - pyknosis,
  karyorrhexis, karyolysis cytoplasm -
  chromatolysistigrolysis (loss of Nissl
  substance)
• - infections (intraplasmatic inclusions)

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• Astrocytes
• major supporting cell type
• in an injury - gemistocytic astrocytes (Gr.
  gemistosfull) - production of dense network of
  cellular processes (analogous to fibrous scar) -
  no collagen! - glial scar
• Rosenthal fibres - eosinophillic
  intracytoplasmatic refractile fibres - reaction
  to slowly growing expansile lesions
• corpora amylacea - accumulation of glycoproteins
  in cell processes - sign of aging

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• Oligodendrocytes
• satelite cells around neurons - processes wrap
  around axons - myelin lymphocyte-like nuclei
• loss of myelin in acquired demyelinating
  disorders (e.g. multiple sclerosis)
• Ependymal cells
• lining of ventricles - closely related to
  chorioidal cells
• loss of e. cells - proliferation of supependymal
  glial cells - ependymal granulations
• infections - CMV - viral inclusions

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• Microglia
• derived from circulating monocytes
• most important phagocytic cells in CNS
• phagocytosis of lipids - gitter cells elongation
  of nuclei - rod cells in viral infections -
  accumulation - microglial nodules

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Edema, herniation and hydrocephalus

• rigid compartment (skull, vertebral column, dura
  mater)
• brain parenchyma (P), blood (B), CSF (C)
• PBCconstant

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Cerebral edema

• more appropriately brain parenchymal edema
• vasogenic
• disruption of integrity of the blood-brain
  barrier
• escape of fluid from vasculature into
  interstitial space (interstitial edema)
• no lymphatic vessels! - no drainage!
• localized (periphery of abscesses or tumors) or
  generalized
• cytotoxic
• intracellular edema - due to cellular injury -
  e.g. hypoxia-ischemia

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• Clinically
• headache, edema of N.II. papilae, vertigo,
  vomiting, coma, death
• Grossly
• increased weight (1500 g)
• brain overfills cranial cavity, gyri are
  flattened, sulci are narrowed, ventricles
  compressed
• herniation occurs

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Herniation

• increased intracranial pressure - brain is "too
  large" for the cranial cavity
• type of herniation depends on location of
  expansion

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1. Transtentorial (uncinate) herniation

• medial aspect of temporal lobe is compressed
  against the free margin of tentorium cerebelli
• N.III. is compressed - ocular manifestation
• posterior cerebral artery is compressed -
  secondary ischemic injury (visual cortex)

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2. Subfalcine (cingulate) herniation

• unilateral asymmetric expansion within cerebral
  hemisphere
• displacement of cingulate gyrus under the falx
  cerebri
• compression of branches of anterior cerebral
  artery

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3. Tonsillar herniation

• displacement of cerebellar tonsils through the
  foramen magnum
• life threatening - brain stem compression,
  compromises vital respiratory centers
• hemorrhagic lesions in the midbrain (secondary
  brain stem (Duret's) hemorrhages)

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Hydrocephalus

• CSF produced by choroid plexus - circulation
  (foramina Luschka and Magendie) - absorption by
  arachnoid granulations
• hydrocephalus accumulation of excessive CSF
  within ventricular system
• decreased resorption (majority of cases) or
  overproduction
• noncommunicating h. - obstruction of the flow of
  CSF within the ventricles (tumors of aqueductus
  Sylvii, postmeningitic stenosis)
• communicating h. - obstruction of the flow of CSF
  in subarachnoid space or in granulations

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• before closure of cranial sutures - enlargement
  of the head, increase of head circumference
• after closure of cranial sutures - enlargement of
  the ventricles, increased intracranial pressure
• h. ex vacuo dilatation of the ventricular
  system (secondarily) due to loss of brain
  parenchyma - compensation flow of CSF remains
  normal

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Vascular diseases

• normally - 15-20 of cardiac output - very
  sophisticated system of autoregulation of
  perfusion
• ischemia - irreversible parenchymal injury within
  brief period (5 min)
• vascular insults - 3rd most common cause of death
  (USA)
• global hypoxic-ischemic encephalopathy
• infarcts
• hemorrhages

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Global hypoxic-ischemic encephalopathy

• brain is sufficiently perfused even in severe
  hypotension (50 mm Hg systolic)
• hypoxiadecrease in the O2 ischemiadecrease of
  tissue perfusion
• most susceptible - neurons (namely pyramidal
  cells of hippocampus, Purkinje cells of
  cerebellum)
• high risk areas at junctions of arterial
  territories (watershed areas)

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• morphology - depends on severity of ischemia and
  duration from injury
• first changes visible only after 12-24 hrs.
  (patient must survive this period!)
• Grossly edema, softening, irregular
  discoloration, areas of hemorrhage, laminar
  cortical necrosis
• later on - patient maintained on respiratory
  support - brain death - body survives, in brain
  progression of necrosis - "respirator brain" -
  swollen, dusky and soft
• fate of the patient depends on degree of ischemia
  (only confusion - coma - loss of cortical
  functions - death)

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• Micro neuronal shrinkage or swelling,
  eosinophilia, nuclear pyknosis in neuropil -
  perivascular and pericellular empty spaces (sign
  of edema)
• later stages - cleaning of necrosis (gitter
  cells), perifocal gliosis - postmalatic pseudocyst

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Infarcts

• local circulatory disturbances
• most common form of cerebral vascular disease
  (80 of "strokes")
• 7th decade, MgtF
• arterial occlusion causes
• atherosclerosis thrombosis - most comm. int.
  carot. a., basilar a.
• embolism (from heart endocarditis, atrial
  thrombi, proximal segment of carotid a.,
  paradoxic thrombembolism f. ovale) - most
  common target intracerebral blood vessels
  (middle cerebral a.)

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• Extent, distribution and clinical symptoms
  influenced by
• site of arterial occlusion
• time span of development
• presence of anastomoses (circle of Willis)
• systemic perfusion pressure
• Grossly (irrespective of causes and location)
• first changes after 6-12 hrs - softening, pale
  discoloration, blurring of borders
• full blown appearance - 2-3 days - liquefaction -
  malacia sharper demarcation
• after 1Mo - cavitation (postmalatic pseudocyst)

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• Clinical symptoms
• sudden onset, preceded by transient episodes of
  neurologic dysfunctions - Transient Ischemic
  Attacks (TIAs) - important predictor of stroke
• 1/3 of patients with TIAs develops infarcts
• symptoms caused by infarct itself, perifocal
  edema, herniation
• contralateral hemiparesis spasticity
• loss of sensation, visual field abnormalities
• speech abnormalities (aphasias) - if dominant
  hemisphere is involved
• small infarcts in basal ganglia - slowly
  progressing symptomatology
• status lacunaris, status cribrosus

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Intracranial hemorrhages

• epidural
• subdural
• subarachnoid
• intraparenchymal

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Epidural hematoma

• rupture of meningeal artery (skull fracture)
• middle mening. a.
• expansion - compression of brain herniation
• rapid progression - immediate surgical drainage!
• lucid interval between trauma and progressive
  loss of consciousness

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Subdural hematoma

• disruption of bridging veins (brain-dural
  sinuses)
• rapid change of head velocity (blows to the head,
  violent shaking)
• mainly at cerebral convexities
• acute - slowly progressing - clotted blood
• chronic - in atrophic brains - no acute symptoms
  - decomposition of blood - osmotic enlargement -
  slowly progressive neurological symptoms
• confused clinically with dementia, Alzheimer's
  disease

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Subarachnoid hemorrhage

• less frequent than intraparenchymal hemorrhage
• not associated with trauma
• most common cause - rupture of saccular (berry)
  aneurysm, less commonly A-V malformation
• 1 of population (more common in certain
  disorders - polycystic kidney disease,
  coarctation of aorta, A-V malformations of the
  brain)
• more frequent in arterial hypertension

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Saccular (berry) aneurysm

• location - bifurcation of branches of internal c.
  a. - defect of elastic lamina
• multiple in 25 of pts.
• size mm-cm
• highest risk of rupture 4-7 mm (beyond this
  size likelihood of rupture decreases)
• larger aneurysms - mass effect
• subarachnoid bleeding - usually not massive -
  leakage!
• arterial spasms - infarcts (40) - 4.-9. day

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Clinical features

• FgtM, lt50's
• increased pressure (lifting heavy things,
  defecation)
• abrupt onset, headache, nausea, vertigo, coma
• bloody CSF, meningeal signs (neck rigidity)
• 50 acute mortality
• tendency to recurrence

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Combined intraparenchymal and subarachnoid
hemorrhage

• A-V malformationsclumps of vessels
• arteriesveins
• intrahemispheric or on the surface of hemisphere
• bleeding in 10's-30's

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Intraparenchymal hemorrhage

• traumatic spontaneous
• mid- to late adult life (peak 60Y)
• most common cause hypertension (lt50 of cases)
• 15 of patients with hypertension die because of
  brain hemorrhage
• HT gt atherosclerosis, arteriolosclerosis,
  necrosis of arterioles
• Charcot-Bouchard microaneurysms
• rupture - intraparenchymal bleeding
• vessels lt300µm in basal ganglia

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• Other causes
• systemic coagulation disorders
• open heart surgery
• neoplasms
• vascular diseases (amyloid angiopathy,
  vasculitis, berry aneurysms, A-V malformations)
• Clinical symptoms
• stroke - abrupt onset
• severe headache, vomiting, loss of consciousness
  - coma

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• Grossly
• basal ganglia (putamen, external capsule),
  thalamus, cerebral white matter, pons, cerebellum
• brain is asymetrically distorted - mass effect -
  herniation
• dissection into ventricles and/or subarachnoid
  space
• no or sparse necrosis
• pseudocyst - hemosiderin in the wall

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CNS trauma

• epidural hematoma
• subdural hematoma
• traumatic parenchymal injuries
• Concussion
• Diffuse axonal injury
• Contusion
• Complications

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Concussion

• transient loss of consciousness, widespread
  paralysis, seizures
• recovery over hours to days
• loss of memory about the trauma
• no anatomic lesion!

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Diffuse axonal injury

• cause of posttraumatic dementia or persistent
  vegetative state
• result of sudden angular acceleration/deceleration
  
• stretch of nerve cell processes
• grossly - no changes! (rarely minute areas of
  hemorrhage)

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Contusion

• result of blunt trauma
• lacerations (tearing) and hemorrhages in the
  superficial brain parenchyma
• traumatic subarachnoid hemorrhage
• microscopically - small hemorrhagic infarcts
• any place, most commonfrontal poles, temporal
  poles, occipital poles, posterior cerebellum
• skull is usually intact!
• healing by glial scar, hemosiderin deposits
• common cause of seizure activity

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Complications

• posttraumatic edema (herniations, secondary
  infarcts)
• infections, licquorrhea
• posttraumatic hydrocephalus
• seizures

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Infections

• 2 factors - 1. nature of the infectious agent
  (rabies, HSV I)
• 2. integrity of normal host defenses
  (skull fracture)
• bacteria, viruses, fungi, higher organisms
  (amebae, parasites)
• meningesCSF meningitis
• brain parenchyma encephalitis
• meninges -gt brain meningoencephalitis
• localized (abscess, poliomyelitis) generalized
  (bacterial leptomeningitis)

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Gates of infection

• blood - hematogenous
• nerves - neurotropic (HSV, rabies)
• trauma - direct infection
• ear - otogenic (mastoiditis, ottitis media)
• paranasal sinuses (frontal sinusitis)
• puncture - iatrogenic (lumbal pucture)

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(Lepto)Meningitis

• arachnoidpia matersubarachnoid space
• rapid spread via subarachnoid space -
  generalization
• purulent (usually bacterial)
• lymphocytic (viral)
• chronic (bacterial, fungal, amebic)

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Purulent meningitis

• Etiology
• newborns - E. coli (neural tube defects!)
• children - H. influenzae (vactination!), Str.
  pneumoniae
• young adults - N. meningitidis (small epidemies -
  army, holiday camps)
• old adults, posttraumatic - Str. pneumoniae, G-
  bacilli

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• Grossly
• meninges are congested, edematous, opaque
• exudate in subarach. space (pus, fibrin) -
  yelowish colour
• distribution varies - pneumococcal m.convexities
  hemophilusbasilar exudate
• congestion and edema of the brain and spinal cord
• most severe cases - ventricular ependymitis
  pyocephalus
• Microscopically
• leptimeningessubarachnoid space filled by
  purulent exsudate (neutrophils, fibrin, bacteria)

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• Clinical features
• fever, general symptoms (fatigue, ...)
• meningeal signs - headache, stiff neck, altered
  mental status, photophobia)
• CSF is turbid, neutrophils, protein, glucose
  levels are decreased, bacteria
• prognosis depends on rapidity of diagnosis
  antimicrobial treatment
• late complication meningeal adhesions -
  hydrocephalus

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Lymphocytic meningitis

• usually of viral origin (so called "aseptic")
• self-limited, much better prognosis - spontaneous
  healing, no complications
• any viral infection (most frequent mumps, echo-,
  coxackie-, EBV, HSV)
• sometimes associated with concurrent encephalitis
• clinically similar to bacterial m. - less severe
  symptoms
• CSF - lymphocytes, slightly elevated protein,
  glucose normal

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Chronic meningitis

• bacteria (TB!, Brucella, Treponema pallidum) and
  fungi (Cryptococcus neoformans - AIDS!)
• slower development
• Grossly - basilary meningitis
• Microscopically - lympho, plasma cells,
  macrophages (TB - Orth's cells), fibroblasts,
  granulomas, caseous necrosis (TB)

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• Clinically - headache, stiff neck - may be
  absent!
• CSF - mononuclear cells, increased protein,
  decreased glucose
• Complications - adhesions, hydrocephalus,
  endarteritis (intimal proliferation with
  subsequent occlusion of lumen) - infarcts

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Parenchymal infections

• localized (abscess, tuberculoma, toxoplasmosis)
• generalized (viral encephalitis)

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Brain abscess

• wide variety of bacteria (Staphylococci,
  Streptococci, anaerobes)
• hematogenous spread - from elsewhere in the body
  (endocarditis, lung abscesses, bronchiectasis,
  osteomyelitis)
• contiguous spread - adjacent foci of infection
  (otitis media, sinusitis)
• direct implantation - trauma
• most commonly - cerebral hemispheres (temporal
  and frontal lobes)
• solitary or multiple

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• enlargement - mass effect symptoms according to
  localization
• misdiagnosed as a tumor
• cavity filled by thick pus (yellow-green),
  delimited by pyogenic membrane (layer of
  granulation tissue, richly vascular)
• surrounding parenchyma edematous, congested
• reactive astrocytes

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Viral encephalitis

• almost always spread from extracerebral sources
  (varicella-zoster rabies)
• almost always also infection of meninges -
  lymphocytes in CSF
• histologically - most characteristic
  lymphocytic perivascular infiltrates (cuffing)
  microglial nodules neuronophagia (necrosis and
  fagocytosis of individual neurons) sometimes
  viral inclusions (Negri bodies in rabies, CMV
  inclusions)

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• specific feature tropism of certain viruses
  (zoster - ggl. cells of posterior ganglia
  poliomyelitis - anterior corns of spinal cord)
• certain viruses cause latent infections - hidden
  for many months to years - reactivation
  infection
• 2 groups
• 1. acute viral infections
• 2. slow viral diseases

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Acute viral infections

• (pan)encephalitis, meningoencephalitis
• arthropode-borne (arbo) viruses - mosquitoes,
  ticks
• perivascular infiltrates, microglial nodules
• regional epidemies - eastern and western equine,
  Venezuelan, St. Louis, California encephalitis
• frequently fatal

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• Herpetic infections (HSV I, II)
• necrotizing, hemorrhagic
• inclusion bodies!
• children (newborns), young adults
• fatal, in survivors - dementia, loss of memory
• encephalitis may accompany other common
  infections - measles, rubella, chickenpox, mumps
  and also in AIDS (both HIV and opportunistic
  infections)

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Slow virus diseases

• very long latency, slow progression
• Subacute sclerosing panencephalitis (SSP)
• Progressive multifocal leukoencephalopathy (PML)
• Subacute spongiform encephalopathy
  (Creutzfeld-Jacob)

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Subacute sclerosing panencephalitis (SSP)

• children and young adults
• following measles, rarely after vaccination
• clinically - changes of the personality, slow
  progression to death
• histologically - neuronophagia, gliosis

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Progressive multifocal leukoencephalopathy (PML)

• JC virus (no relation to Creutzfeld-Jacob
  disease!)
• slowly evolving encephalopathy, in
  immunocompromised (AIDS, leukemias,
  immunosupression, TB)
• virus infects oligodendroglia - areas of
  demyelinization
• slow progression of neurologic symptoms, no
  treatment

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Subacute spongiform encephalopathy
(Creutzfeld-Jacob)

• rapidly progressing dementia (months-several
  years) -gt death
• very rare (11Mio) sporadic and familial forms
• etiologic element prion (PRotein infectION) -
  protein with abnormal tertiary structure
• exact mechanism of development is unclear
• closely related to other prion diseases (scrapie,
  kuru (N. Guinea), mad cow disease)
• histology - cerebral cortex - bubbles and holes
  (spongiform encephalopathy)

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Other CNS infections

• protozoal - malaria, toxoplasmosis (pseudocysts
  in AIDS), amoebae, ricketts, parasites

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Tumors

• some specific features
• irrespective of dignity (ben/mal) similar
  clinical symptoms
• sometimes localization is more important than
  biological behavior (ependymoma of IV. ventricle
  - respiratory centre!)

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Tumors of neuroepithelial tissue

• Astrocytic tumors
• wide range of neoplasms
• differ in location, age and gender distribution,
  morphological features, growth potency
• tendency to dedifferentiation in recurrent tumors

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Astrocytoma

• diffuse infiltration of margin - local
  infiltrative growth - difficult operative
  treatment
• younger adults
• several cm - infiltration via commissures into
  contralateral hemisphere
• Histology
• Fibrillary astrocytoma
• Gemistocytic astrocytoma
• Anaplastic astrocytoma - increased cellularity,
  distinct nuclear atypia and marked mitotic
  activity

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Glioblastoma multiforme

• poorly differentiated
• hemorrhage, necrosis - inhomogenous structure
• marked nuclear atypia and mitotic activity,
  prominent neovascularisation and necrosis with
  pseudopalisading of tumor cells
• dismal prognosis (average survival 8-10M)

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Oligodendroglioma

• less frequent (5 of all glial tumors)
• well-differentiated, diffusely infiltrating
• adults, cerebral hemispheres
• tumor cells with rounded nuclei
• microcalcifications (X-rays!)

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Ependymoma

• cerebral ventricles, central canal of the spinal
  cord
• children and young adults (first two decades)
• presents by blocking CSF - no possible operation
• rosettes ( columnar cells arranged around a
  central lumen)

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Medulloblastoma

• malignant infantile invasive tumor of cerebellum
  (vermis, later hemispheres)
• neuronal differentiation
• metastasizes via CSF (implantations on
  ventricular ependyme and in subarachnoid space)

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Meningioma

• slowly growing benign tumor
• attached to dura mater - ventral poles of cranial
  cavity (falx, convexity, sphenoidal bone)
• adults, predominance for females
• usually solitary, rarely multiple
• invasion of bone (not a sign of malignancy)
• whorls and psammoma bodies (Ca2)
• impression of brain parenchyma

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Metastatic tumors of the CNS

• carcinomas (lungs, breast)
• melanoma
• choriocarcinoma
• renal clear cell carcinoma
• multiple lesions, sharp circumscription, spheric,
  collateral edema

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Degenerative diseasesDiseases of myelin

• Multiple sclerosis
• young adults, peak incidence 18-40Y
• waxing and waning neurological abnormalities
• different regions, progression over many years
• visual disturbances (blurred vision, diplopia,
  scotomata)
• paresthesias, spasticity of extremities, speech
  disturbances, gait abnormalities

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• pathogenesis not fully understood
• autoimmune disease?
• environmentalhereditary factors
• Grossly
• external appearance of brain and spinal cord -
  normal
• cut section - areas of demyelinization (plaques)
• plaques anywhere - common sites periventricular
  areas, optic nerves, spinal cord
• early lesions pinksoft, chronic ones grayfirm

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• Microscopically
• areas of demyelinization
• starts in perivenous regions
• variable perivascular lymphocytic infiltrate

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Metabolic and toxic disturbances

• nutritional - avitaminosis B1, B12
• B1 (thiamin)
• Wernicke-Korsakoff sy (encephalopathypsychosis)
• accompanied by peripheral neuropathy
• alcoholics!
• B12 (cobalamin)
• pernicious anemia, peripheral neuropathy
• subacute degeneration of spinal cord (dorsal and
  lateral white columns)

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Poissoning

• lead (Pb), mercury (Hg), arsenic (As)
• industrial chemicals
• medicaments
• irradiation
• alcohol (acute, chronic-Wernicke-Korsakoff sy)

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Metabolic disorders

• metabolic encephalopathy
• hyperglycaemic coma
• uremia
• portotsystemic encephalopathy - hepatic coma
• M. Wilson (hepatolenticular degeneration)
• phenylketonuria

75
Neuronal degenerative disorders

• unknown origin
• similar clinical presentation
• selective lesion of one or several functional
  systems, others uninvovlved (e.g. Parkinsons
  disease - striatum and ncl. niger)
• symetric, progressive course
• inherited or sporadic

76

• involvement of cortex - dementia (Alzheimer,
  Pick)
• involvement of basal ganglia - extrapyramidal
  symptomes (rigidity, tremor) (Parkinson,
  Huntington)
• spinocerebelar degeneration (Friedreich ataxia)
• motoric neurons (ALS, Werding-Hoffman)

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Alzheimer's disease

• most common cause of dementia in elderly (50Y)
• sporadic, in 10 family history
• cause remains unknown
• factors associated with development genetic
  factors, deposition of amyloid (amyloid precursor
  protein-APP)

78
Morphology

• usually brain atrophy (frontal, temporal,
  parietal lobes)
• symetrical dilatation of lateral ventricles
• hydrocephalus ex vacuo
• Micro
• neurofibrillary tangles (coarse filamentous
  aggregates within cytoplasm of neurons) -
  hippocampus, basal forebrain, neocortex and brain
  stem
• senile plaques - aggregates of tortuous coarse
  neurites in the neuropil of cerebral cortex,
  sometimes with amyloid core
• amyloid angiopathy
• only if numerous lesions are present - diagnosis
  of AD

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Parkinsonism

• disturbance in motor neuron functions
• rigidity, expressionless face, stooped posture
• gait disturbances, slowing of voluntary
  movements, pill-rolling tremor
• James Parkinson 1817 (1st descr.)
• Awakenings (R. deNiro)

80

• idiopathic - progressive, 5-8th decade
• parkinson sy
• lesion of dopaminergic pathways
• grossly - depigmentation of susbst. nigra and
  locus coeruleus
• micro - loss of melanin containing ggl. cells
• Lewy bodies - intraplasmatic inclusions

81
Other diseases

• Huntington d. - fatal disorder of extrapyramidal
  motor system - choreadementia
• Amyotrophic lateral sclerosis - (Lou
  Gehrig-baseball star) - progressive degener. of
  pyramidal system - muscle weaknes, atrophy
• Werding-Hoffmann d. - AR - congenital hypotonia
  (floppy infant sy) - loss of neurons in anterior
  horns - death in 1stY
• Pick d. - lobar atrophy - less frequent than
  Alzheimer, similar clinical features

82
Diseases of peripheral nervous system

• axons of motoric and sensoric neurons, Schwann
  cells (myelin)
• two groups of diseases
• peripheral neuropathies
• tumors of peripheral nerves

83
Peripheral neuropathies

• nutritional and metabolic (DM, avitaminosis
  B1-thiamine, B6-pyridoxine), alcoholism, renal
  failure
• toxic (lead, arsenic, antitumor drugs-cisplatin,
  vincristine, organic solvents)
• inflammatory (Guillain-Barré, vasculitic
  neuropathy, leprosy, sarcoidosis)
• hereditary
• miscellaneous (amyloidosis, paraneoplastic, Ig
  disorders)

84
Tumors of peripheral nerves

• Schwannoma (neurilemmoma, neurinoma)
• tumor of Schwann cells
• solitary, encapsulated, sometimes pigmented
• any peripheral nerve, often N.VIII (acoustic
  neuromas - deafness) or spinal nerves
  (paravertebral)
• nerve at the periphery of the tumor (surgery
  possible!)
• Histo - 2 components
• Antoni A - organized, palisaded (Verocay bodies)
• Antoni B - myxoid, patternless
• no risk of malignant transformation

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• Neurofibroma
• tumor of Schwann cells - similar nature
• more frequently multiple, sometimes
  unencapsulated
• peripheral branches of nerves - fusiform
  enlargement - subcutaneous tissue
• nerve embedded within tumor
• Histo - loose structure, slender elongated cells
  with "wavy" nuclei
• no palisades
• risk of malignant transformation (it is rare!)

86
Neurofibromatosis (von Recklinghausen's disease)

• inherited - AD - multiple neurofibromas anywhere
  (skin, retroperitoneum, GIT, spinal nerves)
• skin lesions (pedunculated neurofibromas, café au
  lait spots)
• high risk of malignant transformation!!! -
  malignant peripheral nerve sheath tumor (MPNST)
• Elephant Man (D. Lynch)