Transcript TYPES OF HERNIATIONS

Pathology of
Nervous System (I) -1
2016
Dr. Mohammed Alorjani, MD EBP
OUTLINE:
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Characteristic cellular features in the CNS
General patterns of CNS cell pathology following
various types of injury
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Consequences of ↑ CNS pressure
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Patterns of CNS vascular disease including
trauma & perinatal CNS injuries
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Patterns of CNS infection
Significant features in CNS
Pathology
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Extremely susceptible to increased I.C.P.
Highly susceptible to ischemia & hypoxia
Site of lesion may be more important than
its nature
Selective vulnerability of defined structures
to disease processes
Selective function of neurons in different
sites  Same process but different
symptoms
No regeneration  gliosis not fibrosis
Component cells of CNS
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Neurons
Glial cells & fibers:
 Astrocyte
 Oligodendrocyte
 Ependymal
cells
 Microglia
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Meninges:
 Meningothelial
cells
 Connective tissue & BV
Reactions of components to injury
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Neurons:
A- Acute injury:
I- Necrosis:
12-24 hrs Irreversible ischemia/hypoxia:
RED NEURONS
with injured axons → axonal swelling →
SPHEROIDS
II- Apoptosis in development, aging…..
Red Neurons in ischemic injury
B - Chronic or subacute injury:
Degenerative diseases
– Neuronal loss & replacement by gliosis in
progressive diseases, usually selective
– Neuronal processes may be thickened &
tortuous (Dystrophic Neurites)
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e.g. Parkinson’s Disease, Alzheimer’s
disease …….. etc.
C -Axonal injury lead to:
Cell body swelling & Central Chromatolysis
D- Inclusions:
Nuclear or cytoplasmic e.g. viral infections
E - Accumulations e.g.
lipofuscin, complex lipids & abnormal
proteins e.g. Tay Sach Disease …
Chromatolysis
Viral nuclear inclusions
Rabies, cytoplasmic inclusions
Lipid Accumulation
 Astrocytes:
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Respond by ↑number & size
Commonest reactive change is Gliosis
May lead to Fibrillary astrocytes
Gemistocytes –
– Swollen reactive astrocytes with
acidophilic cytoplasm (↑GFAP)
Rosenthal fibers –
– Aggregates of thick eosinophilic astrocytic
fibers, in old gliosis or some low grade
glial tumors
GFAP immunostain showing reactive astrocytes
Arrows pointing at Gemistocytes
Gemistocytes
Rosenthal fibers
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Oligodendrocytes:
- Synthesis & maintenance of myelin
- Deranged in demyelinating disease
- Inclusions in specific viral infections
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Ependymal cells:
- Ependymal Granulations ??
- Inclusions characteristic of CMV
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Microglia:
Scavengers of the brain:
– Macrophages in infarction: (Gitter cells)
– Elongated cells in syphilis: (Rod cells)
– Aggregates of microglia around injured
cells: (Microglial nodules)
– Aggregate around dead neurons:
(Neuronophagia)
Neuronophagia
Microglia showing neuronophagia
Increased Intracranial
Pressure
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Definition:  in CSF pressure > 15 mm. Hg
Manifestations:
– Papilledema & visual disturbances
– Nausea & vomiting
– Headache
– Neck stiffness
– Mental status changes
– Others
Pathophysiology:
Brain 70% , CSF 15% , Blood 15%
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Intracranial compartments are balanced
Expansion in any component is first
compensated by  in the rest
i.e.  CSF,  blood ,  ventricular size
If P.  15-20mm.Hg , compensation fails
Displacements & Herniations
Usually to opposite side of lesion 
contralateral ± ipsilateral symptoms
 TYPES
OF HERNIATIONS:
Types of herniation
1- Subfalcine herniation
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Herniation of Cingulate
gyrus under falx
cerebri into the
subfalcine space
• Pressure on Anterior
Cerebral Artery 
Cerebral infarction
2- Transtentorial hernation
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Uncinate herniation of medial
temporal lobe through free
margin of tentorium
• Pressure on PCA  Occipital
infarction
• 3rd.& 6th. Cranial Nerves.
 ipsilateral dilated pupil &
impaired eye movement
• Cerebral peduncle
compression on opposite side
 ipsilateral hemiparesis
3- Tonsillar herniation
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Herniation of cerebellar
tonsil and medulla
through foramen
magnum
• BRAIN STEM !!!
• Pressure on
respiratory &
cardiac centers
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Result :
Brain stem compression & hemorrhage
 Acute obstruction CSF
 Cardiorespiratory failure & death
 DURET Hemorrhages:
* Midline and paramedian brain stem
hemorrhage secondary to brain herniation
due to increased ICP above the tentorium
from any cause.
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* Cause ? Laceration of penetrating veins
and arteries supplying upper brain stem
Duret hemorrhage
Causes of Increased ICP
1- Cerebral Edema
i - Vasogenic due topermeability with
dysfunction of blood brain barrier
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Extracellular
More in white matter
Localized or Generalized
Infarcts, contusions, tumors, abcesses…
ii- Cytotoxic due to neuronal & glial injury
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Intracellular
More in grey matter
More in toxic & metabolic causes
Dry flat gyri
Sulci narrowed, blurred
markings
Normal white matter
Edematous white matter
2- Infarction & Hemorrhage
3- Infections - Abscesses & meningitis
4- Tumors - Primary & Secondary
5- Trauma - especially in diffuse brain
damage
6- Hydrocephalus
CSF
FLOW
HYDROCEPHALUS
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Amount of CSF is balanced between its
generation & resorption.
Otherwise, hydrocephalus develops.
Excess CSF in ventricular system with
enlarged ventricles, caused by
I-  resorption in inflammation &
obstruction
ii- Overproduction of CSF, e.g. in some
tumors
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Hydrocephalus maybe acute  rapid
ICP
Chronic with compensation, mainly in
children  Large head, thin skull
Fontanelle closure is the factor whether hydrocephalus will result in cranial enlargement
Hydrocephalus. Magnetic resonance image of a child with
communicating hydrocephalus, involving all ventricles.
Hydrocephalus. Dilated lateral ventricles seen in a coronal section
through the midthalamus.
Types of Hydrocephalus:
1- Noncommunicating:
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Due to obstruction of CSF flow within the
ventricles.
Localized to site of obstruction.
Due to a malformation or
acquired obstruction at foramina –
 Post-inflammatory
 Tumors
 Gliosis around aqueduct of Sylvius
 Intraventricular hemorrhage…etc
2- Communicating:
Impaired resorption.
Generalized to all ventricles.
- Post meningitis
- Post subarachnoid hemorrhage
3- Normal pressure (ex vacuo)
- Brain infarcts & Degenerative diseases
- Compensatory  CSF & Dilatation of
ventricles.
Congenital Malformations
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May involve brain or spinal cord, causes ???
May be associated with mental retardation,
or hydrocephalus …etc
Include:
– Neural Tube defects e.g. Spina Bifida occulta,
meningomyelocele, encephalocele, anencephaly…
– Forebrain defects
– Post. fossa defects e.g. Arnold Chiari
Syndrome.
– Spinal cord defects.
Arrow points at meningomyelocele
ANENCEPHALY
Thank you