CSB520 Lecture Notes - Lecture 13: Demyelinating Disease, Diarrhea, Peripheral Neuropathy
Week 13 - Nervous System Pathology
Wednesday, 8 June 2016 7:18 PM
MeningesMeninges
1. Dura (outer later)
○Thick protective layer continuous with skull
2. Arachnoidea (middle layer)
3. Pia (innermost layer)
○Continuous with actual brain tissue
Cerebrospinal Fluid - SubarachnoidCerebrospinal Fluid - Subarachnoid
•CSF is secreted into the ventricles and flows throughout the subarachnoid space where
it cushions the CNS
Nervous SystemNervous System
•Highly specialised cells, regions etc.
•CNS is protected from mechanical injury by the skull & vertebrae
•Meninges separate the brain from the body - the blood brain barrier
•CSF surrounds the brain & spinal cord
Cross Section of the BrainCross Section of the Brain
•Grey matter
○Cortex - neurone, support cells
○Deep parts of the brain - basal ganglia, thalamus, hypothalamus
•White matter
○Beneath the cortex - myelinated axons
○Commissural, projection association fibres
•Trauma (sudden torsion) can tear the myelin sheaths)
Cells of the Nervous SystemCells of the Nervous System
•Neurone
○Perikaryon
○Dendrites
○Axon
•Support cells (glia)
1. Astrocytes
2. Oligodendroglia
3. Microglia
4. Ependymal cells
○These are proliferative
•Will divide if there is injury in the brain and form scar tissue (instead of
collagen)
•Area of GLIOSIS
•Tighter junctions and strong basement membranes (astrocytes) in brain
○Tightly regulated environment
Why is the CNS Special?Why is the CNS Special?
•Between a rock and a hard place
•If something goes wrong, there is no place for the brain to shift
•SOL = space occupying lesionSOL = space occupying lesion
•Intracranial pressureIntracranial pressure
•If the SOL is sudden, it will lead to sudden increase in intracranial pressure the brain
will be displaced
○The most dangerous place to displace is the foramen magnum
○This is a medical emergency in adults, and so medical professionals will try to
reduce rise in the intracranial pressure, perhaps by opening a hole in skull
allowing it to swell
•If SOL is slow, then over time the brain will adapt and then apoptosis leading to
atrophy
Space Occupying LesionSpace Occupying Lesion
•Increased volume of intracranial contents (e.g. oedema, hydrocephalus)
•Oedema:
○Abnormal accumulation of fluid in cerebral parenchyma, leading to increase in
cerebral volume
•Hydrocephalus:
○Increased CSF
○CSF backing up in the brain
1. Diffuse:
○Vasogenic
•BBB dysfunction (breakdown of the tight endothelial junctions) leading to
increased permeability (oedema or hydrocephalus)
○Cytotoxic (toxic to living cells)
○Interstitial leading to hydrocephalus
2. Focal
○Abscess, tumour, haematoma (accumulation of blood)
HydrocephalusHydrocephalus
•Communicating
○Increase of CSF throughout the system, accumulating everywhere
○Atrophy all around (in ventricles, on surface of brain)
•Non-communicating
○Problem with flow of CSF
○Leading to gliosis or blockage
Consequences of SOLsConsequences of SOLs
•Increased intracranial pressure (ICP)
○Intracranial shift & herniation
○Epilepsy
○Hydrocephalus
○Systemic Fx (brain dysfunction)
•Adaptation
○Decreased CSF
○Pressure atrophy
○Decreased blood volume
•Limits to adaptations results in critical period when any increased in volume greatly
raises pressure
Raised ICPRaised ICP
•Papilledema (pupils fixed and dilated)
○Swelling & compression of optic nerve
•Nausea & vomiting
○Pressure on vomiting centres in pons & medulla
•Headache
○Pressure on pain receptors around intracranial blood vessels and in the Dura
mater
•The brain tissue itself doesn't have pain reception
•Headache would be due to meninges or blood vessels
•Altered levels of consciousness (from drowsy to deep coma)
•Death
Brain HerniationBrain Herniation
•Associated with SOLs
1. Herniation of cingulate gyrus
2. Herniation of cerebral uncus
3. Herniation of cerebral tonsil
•Associated with traumatic injury
4. Herniation through an opening of broken skull
Major DiseasesMajor Diseases
•Developmental & genetic diseases
•Diseases caused by trauma
•Circulatory disorders
•Infectious diseases
•Brain tumours
•Autoimmune diseases
•Metabolic & nutritional diseases
•Neurodegenerative diseases
Traumatic InjuryTraumatic Injury
•Missile (penetrating) vs non-missile (blunt)
•Missile:
○Depressed (e.g. fracture, a bit of the skull pushing into the brain)
○Penetrating (e.g. a bullet)
○Perorating (e.g. shots right through)
•Non-missile:
○Road traffic accidents, falls, rotational forces (e.g. shaken baby syndrome)
○Intracranial haematomas, oedema, infarction & infection
•Primary vs Secondary
○Primary:
•Focal (contusions, lacerations)
•Diffuse axonal injury
○Secondary:
•Intracranial haematomas, oedema, infarction & infection
•Complications: epilepsy, persistent vegetative state, post-traumatic dementia
Trauma of the CNSTrauma of the CNS
•Brain injury
○Brain concussion
○Diffuse axonal injury
○Brain contusion
•Coup lesion & countercoup lesion
○Laceration
Intracranial HaemorrhagesIntracranial Haemorrhages
•Epidural
Document Summary
Thick protective layer continuous with skull: arachnoidea (middle layer, pia (innermost layer) Cerebrospinal fluid - subarachnoid: csf is secreted into the ventricles and flows throughout the subarachnoid space where it cushions the cns. Nervous system: highly specialised cells, regions etc, cns is protected from mechanical injury by the skull & vertebrae, meninges separate the brain from the body - the blood brain barrier, csf surrounds the brain & spinal cord. Cross section of the brain: grey matter. Deep parts of the brain - basal ganglia, thalamus, hypothalamus: white matter. Commissural, projection association fibres: trauma (sudden torsion) can tear the myelin sheaths) Axon: support cells (glia, astrocytes, oligodendroglia, microglia, ependymal cells. These are proliferative: will divide if there is injury in the brain and form scar tissue (instead of collagen, area of gliosis, tighter junctions and strong basement membranes (astrocytes) in brain. Why is the cns special: between a rock and a hard place.
