1. Characteristic features of CNS pathology
By: Shifaa’ AlQa’qa’

2. Normal brain:
The neocortex (gray matter):
six layers:
outer plexiform, outer granular, outer pyramidal,
inner granular, inner pyramidal, polymorphous
The white matter
Glial cells: oligodendrocytes, astrocytes, ependymal cells and microglia,

3. Features of Neuronal Injury:
acute neuronal injury:
Within 12 hours of an irreversible hypoxic-ischemic insult
Neurons:
shrinkage of the cell body
pyknosis of the nucleus
disappearance of the nucleolus
loss of Nissl substance
intense eosinophilia of the cytoplasm (“red
neurons”)

4. - axons : Axonal swellings (spheroids) cell body enlargement and rounding, peripheral displacement of the nucleus, enlargement of the nucleolus, peripheral dispersion of Nissl substance (central chromatolysis)

5. intracellular inclusions:
neurodegenerative diseases
Pathogenic viruses
With age (lipofuscin)
dystrophic neurites (neuronal processes become thickened and tortuous):
Neurodegenerative diseases

7. Astrocytes in Injury and Repair:
Gliosis ( scar formation)
hypertrophy and hyperplasia
The nucleus enlarges and becomes vesicular
the nucleolus becomes prominent
gemistocytic astrocyte (cytoplasm expands)
fibrillary astrocytes (cytoplasm shrinks)
Rosenthal fibers

10. Oligodendrocytes:
viral inclusions (PMLE)

11. Microglial cells:
activated macrophages in areas of demyelination, organizing infarct, hemorrhage, or trauma
rod cells (elongated nuclei)---- infection ??
microglial nodules/neuronophagia

12. Ependymal cells:
Injury with viral inclusions???

13. Cerebral Edema
Accumulation of excess fluid within the brain parenchyma
Extracellular Vasogenic edema
Intracellular Cytotoxic edema
Often occur together particularly after generalized injury

14. Vasogenic edema:
- blood-brain barrier is disrupted/ increased vascular permeability---- trauma, tumors, focal inflammation
- Localized
- Generalized
Cytotoxic edema:
cell membrane injury (neurons, glial cells)/ hypoxic-ischemic insult or after exposure to some toxins

15. The edematous brain is:
softer than normal
Often appears to “over fill” the cranial vault.
In generalized edema the gyri are flattened,
the intervening sulci are narrowed,
the ventricular cavities are compressed

16. Hydrocephalus
accumulation of excessive CSF within the ventricular system

18. impaired flow or resorption;
Overproduction of CSF

19. Noncommunicating hydrocephalus/:
localized obstacle to CSF flow
portion of the ventricles enlarges
Eg: masses obstructing the foramen of Monro or compressing the cerebral aqueduct
Communicating hydrocephalus:
The entire ventricular system is enlarged
Caused by reduced CSF resorption
Eg: meningitis

20. The head enlarges----- Infants
Increased intracranial pressure

21. Hydrocephalus ex vacuo ????

22. Herniation
When the volume of tissue and fluid inside the skull increases beyond the limit permitted by compression of veins and displacement of CSF, intracranial pressure rises---- trauma, intracranial hemorrhage, brain tumors
The cranial vault is subdivided by rigid dural folds (falx and tentorium), and a focal expansion of the brain displaces it in relation to these partitions.
If the expansion is sufficiently large, herniation occurs displacing tissue across dural partitions inside the skull or through openings in the skull

23. Subfalcine (cingulate) herniation:
Unilateral or asymmetric expansion of a cerebral hemisphere displaces the cingulate gyrus (frontal lobe) under the edge of falx.
compression of the anterior cerebral artery

24. Transtentorial (uncinate) herniation:
medial aspect of the temporal lobe is compressed against the free margin of the tentorium
posterior cerebral artery may also be compressed (primary visual cortex)
the third cranial nerve is compromised (pupillary dilation and impaired ocular movements on the side of the lesion)
Hemiparesis ipsilateral to the side of the herniation (false localizing sign)---- compression of the contralateral cerebral peduncle against the tentorium---Kernohan’s notch
Duret hemorrhages---- midbrain and pons

25. Tonsillar herniation:
displacement of the cerebellar tonsils through the foramen magnum
life-threatening, because it causes brain stem compression and compromises vital respiratory and cardiac centers in the medulla