17. Central Nervous System Pathology Flashcards
Neural crest cells develop into what system?
PNS
Wall of the neural tube develops into what system?
CNS
Lumen of the neural tube develops into what?
ventricles, spinal cord canal
Neural tube defects associated with what (nutritional deficit)?
inadequate folate intake by mom prior to conception.
how can you detect a neural tube defect prior to birth?
elevated AFP (alpha-fetoprotein) in amniotic fluid and maternal blood.
anencephaly can result in what in the mother?
maternal polyhydramnios: since fetus is lacking CNS-controlled swallowing center, doesn’t swallow/resorb amniotic fluid: leads to polyhydramnios.
spinal bifida is failure of what to close?
posterior vertebral arch (caudal end of neural tube)
spinal bifida occulta is what?
almost-closed neural tube: leaves little tuft of hair or dimple
spinal bifida is what? what are the 2 types?
neural tube didn’t close; meningiocele (protrusion of meninges alone) or meningiomyelocele (meninges + spinal cord)
what is cerebral aqueduct stenosis?
congenital stenosis of the cerebral aqueduct
what does the cerebral aqueduct do?
drains fluid from the 3rd to 4th ventricles
what results from cerebral aqueduct stenosis?
accumulation of CSF -> hydrocephalus, large head circumference.
what is dandy-walker formation?
cerebellar vermis does not develop
how does a dandy-walker formation present?
very small cerebellum, massively dilated 4th ventricle, often hydrocephalus
what is an arnold-chiari malformation
congenital extension of the cerebellar tonsils through the foramen magnum
Type 1 vs Type 2 Arnold-chiari malformation?
Type 1: no sx
Type 2: obstruction of CSF flow -> hydrocephalus
in addition to hydrocephalus, what 2 other things can be associated with an arnold-chiari malformation?
meningiomyelocele, syringomyelia
what are the leptomeninges?
the Pia and the arachnoid layers. these are more fragile/light than the dura, which is DURAble!
from the brain to the skull, what is the order of the layers?
acronym = PAD: pia, arachnoid, dura
meningitis is inflammation of which layers?
the leptomeminges: pia and arachnoid.
in neonates, what are the 3 most common agents of meningitis?
Group B Strep, E Coli, Listeria monocytogenes. (BEL: babies come from BELlies!)
how do neonates get meningitis?
during birth/vag canal, from mom
how do we try to prevent neonatal meningitis?
by treating mom with abx if she has Group B strep.
most common cause of meningitis in children/teens? how does it get to the meninges?
Neisseria meningiditis. (also Strep pneumo) gets in via nasopharynx, gets into bloodstream, from there gets to meninges.
most common cause of meningitis in adults/elderly?
strep pneumo, N meningiditis
most common cause of meningitis in unvaccinated infants?
H flu
most common VIRAL cause of meningitis?
coxsackie virus via fecal-oral transmission
cause of meningitis in immunocompromised?
fungi
presentation of pts with meningitis?
classic triad: headache, neck stiffness, fever. may also see photophobia (esp with virus), vomiting, altered mental status
lumbar puncture: between what vertebrae? why?
L4-L5. spinal cord stops at L2, but subarachnoid space continues til S2
when doing LP, what layers will you cross?
skin, ligament, epidural space, dura, subdural space, arachnoid. NOT pia.
LP sample containing neutrophils with low glucose suggests what cause of meningitis?
bacterial: immune reaction, and they will eat the glucose
LP sample containing lymphocytes with normal CSF glucose suggests what cause of meningitis?
viral.
LP sample containing lymphocytes with normal glucose suggests what cause of meningitis?
fungal
how does the normal CSF glucose level relate to the normal serum glucose level?
CSF should be 2/3 serum glucose level.
complications of meningitis classically seen with what type of cause? why?
bacterial. because pus, inflammation will put pressure on the brain, causes herniation
what can brain herniation cause?
death
symptoms associated with healing from bacterial meningitis?
from healing, have massive fibrosis. this can cause:
- hearing loss (nerve damage)
- hydrocephalus (normal CSF path is blocked)
- seizure (scarring to brain surface)
what are a few forms of dementia/degen disorders?
Alzheimers, Vascular dementia, Pick disease, Parkinson’s, Huntington’s, Normal Pressure Hydrocephalus, Spongiform Encephalopathy
basics of degenerative disorders: characteristic is loss of what? often this is due to what?
characteristic loss of neurons within the grey matter. often this is due to accumulation of proteins, which damages neurons
degen of the cortex leads to what, in general?
dementia (this is grey matter loss)
degen of the brainstem/basal ganglia leads to what, in general?
movement disorders (also grey matter loss, but not cortical grey matter)
Alz: onset is generally around what age? what happens to risk with age?
onset around 60. risk doubles every 5 yrs thereafter.
Alz: degen disease of what part of brain?
cortex
(mainly temporal lobes and hippocampus according to Swenson & other sources)
what is the most common degen disease?
Alz
Alz: clinical features
- slow-onset memory loss, progressive disorientation
- loss of learned motor skills, language
- changes in behavior and personality
- mute and bedridden; infection commonly causes death
Alz: focal neuro defecits?
not generally seen. no focal tremor, no ataxia, no chorea
what are the two basic types of Alz?
sporadic (seen in elderly) and early-onset
most cases of Alz are sporadic or early onset?
95% sporadic
sporadic Alz: what allele is associated with incr risk? decr risk?
ApoE4 - incr risk
ApoE2 - decr risk (remember 4>2 therefore greater risk)
risk factors for sporadic form of Alz?
age, ApoE4
risk factors for early-onset Alz?
mutations in presenilin 1 and 2 genes, Down’s syndrome
what is the connection between Down’s and Alz?
Downs: 3 copies of chromo 21.
Amyloid Precursor Protein is on that chromo
how does the Amyloid Precursor Protein lead to Alz?
APP is a receptor on neurons. it is broken down by either alpha-amyloid or beta-amyloid. if person has ApoE4 allele, APP will be broken down by beta-amyloid, and resulting protein cannot be broken down –> Alz.
Alz: appearance of gross brain?
diffuse cerebral atrophy with narrowing of gyri, widened sulci, dilated ventricles
Alz: what are the plaques made of? what is their appearance?
neuritic plaques: made of beta-amyloid and trapped neuritic processes. look like blobby/diffuse Lewy bodies?
Alz: how can amyloid deposits incr hemorrhage?
they may also deposit around vessels
Aside from neuritic plaque, what is a path feature of Alz?
neurofibrillary tangles: intracellular aggregates of fibers made of Tau.
why would Tau protein get tangled in Alz? what do these tangles look like?
in Alz, it is hyperphosphorylated, and cannot organize cellular microtubules in that state. flame-like tangles
Alz: what loss occurs in the nucleus basalis of Meynert?
loss of cholinergic neurons