Chapter 29 Pathogenesis and Physiology of CNS Disease and Injury Flashcards
What are the two broad types of CNS cells
Neurons and glial cells
Name 3 glial cell types and their main function
- Oligonendrocytes: Form CNS myelin sheaths
- Astrocytes: Structural and metabolic support
- Microglia: Innate immune system. Extraneural lineage
What does grey amtter consist of?
and white mater
Grey matter = neuronal cell bodies
White matter = axons and associated glial cells
What is the grey/white matter distribution of brainstem?
Scattered grey matter nuclei with intervening tracts of white matter
Name the four ventricles of the brain and the connceting ducts
- Lateral ventricles (one in each hemisphere)
- 3rd ventricle (midline, ventral to lateral ventricles)
- Fourth ventricle (ventral to cerebellum)
Lateral ventricles –> interventricular foramina –> 3rd ventricle –> mesencephalic aqueduct –> 4th ventricle –> lateral aperture into subarachnoid space OR continues caudally to enter central canal of SC
Where is CSF formed
Choroid plexus of lateral 3rd and 4th ventricles
What are the 3 layers of meninges (out to in)
What maches up pachymeninges?
And leptomeninges?
Dura, arachnoid, pia
Pachymeninges = dura + arachnoid
Leptomeninges = arachnoid + pia
What are the two (potential) spaces between the meninges
Subarachnoid (filled with CSF)
Subdural (potential space for haemorrhage)
Wat is the name of connective tissue separating cerebral hemispheres?
And cerebrum from cerebellum
- Falx cerebri*
- Tentorium cerebelli*
Anatomically speaking, how may the brain herniate?
- Transtentorial (ventral to tentorium)
- Through foramen magnum
T2-weighted sagittal image of the brain showing herniation of the cerebellum through the foramen magnum (long arrow) and transtentorial herniations causing compression of the cerebellum (short arrows).
What is normal resting cell membrane potential?
Intracellular cation?
And extracellular cation
- 80 mV (inside of cell negative)
K+ intracellular
Na+ extracellular
What is the role of myelin?
Allows rapid conduction over long distances while minimizing axonal diameter
At what MAPB is CNS perfusion steadily maintained
50 - 160 mmHg
Graph of autoregulatory control of cerebral blood flow (CBF) and vascular diameter, in response to changes in mean arterial pressure (MAP), arterial partial pressure of oxygen (PaO2), and arterial partial pressure of carbon dioxide (PaCO2).
How does high paCO2 worsed increased ICP?
Increasing PaCO2 –> vasodilation of cerebral vessels –> increased intracranial volume and ICP
What % change in cerebral perfusion if effected by a 1% change in PaCO2?
5%!
ie small Co2 change –> large perfusion change
Below which paco2 level is cerebral ischameia possible (due to vasoconstriction)
<25 mm Hg
What is formula for cerebral perfusion pressure (CPP)
CPP = MABP - ICP
Explain pathophys of cushings reflex
High ICP or low MABP –> ischaemia of neurons in medulla –> increased systemic vasomotor tone –> baroreceptors activated –> bradycardia
If cerebral perfusion pressure drops further –> massive cathecholamine release –> myocardial ischaemi and arrythmias
Which abx have good bbb penetration? And which poor?
How is injury to CNS subclassified
- Primary mechanical damage: Brain swelling, hypoxia, diffuse axonal injury
- Secondary injury mechanisms: Biochemical and metabolic changes –> neuronal and glail cell death
What study has been performed.
Describe abnormalities
Cervical myelogram from a Doberman Pinscher with neck pain and tetraparesis that was diagnosed with caudal cervical spondylomyelopathy.
A: Ventral extradural compression of the spinal cord at the C5-C6 intervertebral disc space is obvious with the vertebral column in neutral position.
B: When the vertebral column is extended (B), a dorsal component to the spinal cord compression is visible at dorsal articulation of C5-C6, and a ventral extradural compressive lesion is also visible at the C6-C7 intervertebral disc space. This illustrates the dynamic nature of compression of the vertebral column and highlights the potential for inflicting further spinal cord injury while performing diagnostic tests.
What study had been performed
Describe abnormalities
Lateral view of a myelogram of the thoracolumbar vertebral column of a dog that was hit by a car and presented paraplegic with absent sensation in both pelvic limbs. The intervertebral disc space at the T13-L1 articulation is widened. Contrast medium can be seen filling the substance of the spinal cord over the body of T13, indicating disruption of the spinal cord.
What is hansen type 1 ivdd
and type 2?
Type 1 = NP (dehydrated) extrusion
Type 2 = protrusion
Remember ANNPE: Peracute extrusions of normal nucleus pulposus material can produce very severe primary injuries; laceration of the dura may be inferred on myelographic images, and, on occasion, extruded nucleus pulposus material can traverse the substance of the spinal cord, leading to widespread hemorrhage and malacia
T2-weighted sagittal magnetic resonance image of the lumbar spinal cord showing hyperintensity within the spinal cord parenchyma overlying an intervertebral disc in which the nucleus pulposus appears smaller than those of the adjacent intervertebral discs. A small amount of material lies within the vertebral canal overlying the disc, causing minimal spinal cord compression. These findings are consistent with herniation of a normal nucleus pulposus.
