As amazingly complex as the CNS is, even more amazing is the fact that its components are so remarkably simple----Neuron body, dendrites, axon.
Section from spinal cord. Is this grey matter or white matter?
Neurons with nucleus, nissl (Franz Nissl) granules, nerve fibers, glia. Glia are many times more common than neurons.
Blood vessel with endothelium and/or smooth muscle.
This particular stain shows why the most common glial cell is called an “astro”cyte.
Oligodendrocytes, the CNS myelinators. Note the clear space around their nuclei, much in the same way myelin washed out from schwann glial calls as well.
Ependymal cells look exactly like ciliated columnar cells and like the ventricular spaced and choroid.
Choroid plexus is “papillary” in configuration.
Cluster of microglia, the macrophages of the CNS.
Neuronal loss and gliosis is a hallmark of more “chronic” CNS injury
A comparison of edema “compartments” the ECS (EXTRA Cellular Space) is vasogenic and the ICS (INTRA Cellular Space) is cytotoxic.
Flattened gyri often signify edema. Why? Ans: compression against the calvarium
1) Falx, 2) Cingulate, and 3) Cereballar tonsillar levels of edema
“ Notching” of the cingulate gyrus.
Cerebellar tonsillar herniation
Basic pathophysiologic concepts about hydrocephalus which is defined as any major deviation from the normal physiology of CSF
Hydrocephalus on CT
Hydrocephalus on MRI
Hydrocephalus also showing cerebral edema, CT or MRI? Ans: CT Why? Ans: Bone is always very dense on CT, and water is always intense on T2 weighted MRI
Hydrocephalus, dilated ventricles
COMMON CNS malformations
Note the neural canal extends to the outside of the body. AFP, the same antigen found in hepatomas, is a good screening test for this.
Failure of the prosencephalon to develop, and separate, often leads to cyclops.
Normal corpus callosum
Absent corpus callosum
These are the three most common types of perinatal brain injuries
Differentiation between CNS trauma is crucial in medicolegal cases.
Know the correct definitions
Skull fracture types
Three common sequelae of CNS trauma
You should recall cord injury level versus sensory and motor defects: “C5, still alive”
Histopathologic progression of CNS infarcts, parallels the general cellular progression of events in inflammation
Classical congenital “berry” aneurysm
Extensive basilar subarachnoid hemorrhage
Basal ganglia symptoms include tremors (rhythmic, involuntary, oscillatory movements), athetosis (slow, writhing movements of the fingers and hands, and sometimes of the toes), chorea (abrupt movements of the limbs and facial muscles), ballism (violent, flailing movements), and dystonia (a persistent posture of a body part which can result in grotesque movements and distorted positions of the body).
Meninges, purulent, at the base of the brain
Meninges, purulent, at the top of the brain
Meningitis vs. meningoencephalitis
Perhaps encephalo-meningitis would be a better term? Why? Ans: viruses primarilly involve CNS parenchyma, rather than meninges
Perivascular lymphocytic cuffing is the hallmark viral encephalitis, especially with respect to early, mild, or peripheral considerations.
Eosinophilic Negri body of Rabies, also basophilic inclusions of CMV
Demyelination is associated with gliosis and edema, therefore bright signals on T2 weighted images
Demyelination and gliosis
PR -oteinaceous I -nfectious particle = PRI -on
“ Replication” is felt to be due to the protein undergoing a conformational change to induce neighboring proteins to become like it.
Hence the term “spongiform.”
CJ has also been called JC, but the term “JC” makes it confusable with the JC polyoma virus, so CJ-D is probably the politically correct term
Demyelination, generically, is a NON-specific pattern of CNS reaction to injury of many types and usually goes hand in hand with edema and gliosis, If it wasn’t for the “edema” associated with demyelination, the “plaques” would not be seen on MRI.
The PLAQUE of MS is NOT like a plaque of skin diseases, i.e., it is not a raised lesion, but an area of demyelination.
MS gave MRI its first HUGE boom, by virtue of being able to detect these lesions, due to edema!
Myelinated white matter stains BLUE, and demyelination is loss of blue. Remember MS is a disease PRIMARILLY of WHITE matter.
Plaques microscopically. Demyelination, edema, gliosis, and, lower right, relative preservation of the actual nerve fibers
FOUR classical areas for brain degeneration, a decent anatomic classification.
ALZHEIMER disease is many times more common than all the other dementias put together.
Prominent sulci in cortical atrophy. Why are the sulci, NOT the gyri, prominent in atrophy? Ans: cortical LOSS
Plaques and tangles and beta-amyloid
Plaques and tangles, and central core of AMYLOID
Amyloid with congo red stain (LEFT), and Amyloid with congo red stain under polarization (RIGHT.
Neurons with tangles displacing nucleus, H & E
Neurons with TANGLES, often displacing NUCLEUS.
A “tangle” in proximity to a nucleus. A “tangle” is hyperphosphorylation of a neuron microtubule protein called “tau”, causing it to precipitate
Tau is a gene, Tau protein is a microtubule protein associated with hyperphosphorylation in tau-opathies. MANY cortical dementias are associated with this.
How would one differentiate MID from MS? Ans: MS is purely white matter. In this MRI we see grey matter lesions, so it is more likely MID rather than MS
NORMALLY BLACK substantia nigra due to adequate dopamine.
PALE substantia nigra in Parkinson’s disease (on LEFT) due to inadequate dopamine.
The locus ceruleus is also pale in Parkinson’s disease, which is another pigmented area due to abundant dopamine.
Which patient has Parkinson’s disease? Ans: the RIGHT Why? Ans: decreased dopamine
Lewy bodies are commonly regarded as diagnostic of Parkinson’s disease also. The main substance of the eosinophilic inclusion is alpha-synuclein .
Alpha synuclein stains.
Vitamin B1 deficiency (Wernicke-Korsakoff), hemorrhagic mamillary bodies are the most classic finding. B1 deficiency is the culprit here.
Posterior column demyelination in B12 deficiency, this is also called SUBACUTE COMBINED DEGENERATION
Gliosis vs. Glioma?
Glioma, intermediate grade
Glioma, high grade, Note NECROSIS. NECROSIS (orangophilia and granularity) is needed for the diagnosis of a HIGH grade glioma.
Glioblastoma (multiforme). Why is it called “multiforme”? Note the 1) palisading (two arrows) and 2) necrosis (ovals) which are hallmarks of GBM.
Central necrosis is a sign of rapid growth. It outgrows its blood supply.
Normal oligodendrocytes on the left.
What is this? (Hint: note rosettes) Ans: neuroblastoma
Any midline cerebellum tumor in a child is a medulloblastoma till proven otherwise!
Midline cerebellum tumor in a kid. What is it? Ans: medulloblastoma
Arts of this meningioma are denser than bone.
Note cortical compression from this meningioma.
Psammoma bodies are diagnostic of meningiomas in brain tumors! What other kinds of tumors have psammoma bodies? Ans: papillary carcinomas, classically in thyroid
Toxoplasmosis and lymphomas and encephalitis are very common in AIDS. Might you cal the MRI lesion a “toxoplasmoma”? Ans: Sure
A solitary brain mass is statistically just as likely to be metastatic than primary
PRION PROTEIN Normally found in humans Exact structure known, 208 amino acids Specific chromosome, #20, specific genes also known Requires a conformational change to accumulate and do damage www.freelivedoctor.com