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STEP 1 Pathoma > Chapter 17 > Flashcards

Chapter 17 Flashcards

1
Q

How do neural tube defects arise?

A

From incomplete closure of the neural tube (neural plate invaginates early in gestation to form the neural tube, which runs along the cranial-caudal axis of the embryo. The wall of the neural tube forms the CNS tissue, the hollow lumen forms the ventricles and spinal cord canal, and the neural crest forms the peripheral nervous system)

Associated with low folate levels

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2
Q

How are neural tube defects detected in utero?

A

Elevated alpha fetoprotein (AFP) levels in the amniotic fluid and maternal blood

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3
Q

Anencephaly (absence of the skull and brain) results in what clinical finding?

A

Maternal polyhydramnios (since fetal swallowing of amniotic fluid is impaired)

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4
Q

What is the most common cause of hydrocephalus in newborns?

A

cerebral aqueduct stenosis (between 3rd and 4th ventricle)

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5
Q

Describe the flow of CSF

A

Produced by the choroid plexus lining the ventricles, flows into the lateral ventricles and then into the 3rd ventricle via the interventricular foramen of Monro

From the 3rd to 4th via the cerebral aqueduct

From the 4th ventricle into the subarachnoid space via the foramine of Magendie and Luschka

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6
Q

What is a Dandy-Walker malformation?

A

Congenital failure of the cerebellar vermis to develop presenting as a massively dilated 4th ventricle (posterior fossa) with an absent cerebellum (accompanied by hydrocephalus)

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7
Q

What is a Arnold-Chiari Malformation?

A

Congential downward displacement of the cerebellar vermis and tonsils through the foramen magnum causing obstruction of the CSF flow resulting in hydrocephalus

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8
Q

What is a syringomyelia?

A

Cystic degeneration of the spinal cord arising with trauma or in association with a type I Arnold Chiari Malformation (usually at C8-T1)

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9
Q

How might a syringomyelia present?

A

Presents as sensory loss of pain and temp with sparing of fine touch and position sense in the upper extremities due to involvement of the anterior white commissure of the spinothalamic tract with sparing of the dorsal columns

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10
Q

Syrinx expansion can result in involvement of other spinal tracts leading to:

A

Muscle atrophy and weakness with decreased muscle tone and impaired reflexes due to damage to lower motor neurons of the anterior horn

Horner syndrome with ptosis, miosis, and anhidrosis due to disruption of the lateral horn of the hypothalamospinal tract

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11
Q

How does poliomyelitis cause disease?

A

Damage to the anterior horns due to poliovirus presenting with lower motor neuron signs including flaccid paralysis with muscle atrophy, fasciculations, weakness with decreased muscle tone, impaired reflexes, and negative Babinski sign

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12
Q

What is Werdnig-Hoffman Disease?

A

A variant of spinal muscular atrophy- inherited degeneration of the anterior motor horn (AR) presenting as floppy baby (death occurs within a few yrs of birth)

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13
Q

What is amyotrophic lateral sclerosis (ALS)?

A

Degenerative disorder of upper AND lower motor neurons of the corticospinal tract with atrophy and weakness of the hands as an early sign (lack of sensory impairment distinguishes ALS from syringomyelia)

Mostly sporadic in middle aged adults

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14
Q

What is a known cause of one form of inherited amyotrophic lateral sclerosis (ALS)?

A

Zinc-copper superoxide dismuatase (SOD1) mutation- causes free radical injury to neurons

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15
Q

What is Friedreich-Ataxia?

A
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16
Q

What causes Friedreich-Ataxia?

A

AR due to expansion of an unstable trinucleotide repeat (GAA) in the frataxin gene (frataxin is needed for mitochondrial iron regulation; loss results in buildup with free radical damage)

Presents in early childhood, and pts are wheelchair bound within a couple yrs at most

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17
Q

What is the major association of Friedreich-Ataxia?

A

hypertrophic cardiomyopathy

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18
Q

What is meningitis?

A

Inflammation of the leptomeninges (meninges layers: dura, arachnoid, and pia; the pia and arachnoid are collectively called the leptomeninges)

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19
Q

What are the most common causes of meningitis by age?

A

Neonates: GBS, E. Coli, and Listeria

Adults: N. meningitis, S. pneumo

Coxsackievirus

Fungi (immunocompromised)

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20
Q

How long can neurons survive without glucose?

A

Undergo necrosis within 3-5 minutes

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21
Q

What are the major etiologies of global cerebral ischemia?

A

Low perfusion (e.g. atherosclerosis)

Acute decrease in blood flow (e.g. cardiogenic shock)

Chronic hypoxia (e.g. anemia)

Repeated episodes of hypoglycemia (e.g. insulinoma)

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22
Q

The clinical features of global cerebral ischemia are based on duration and magnitude of the insult. Explain

A

Mild ischemia results in transint confusion with prompt recovery, while severe ischemia results in diffuse necrosis (can cause vegetative state)

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23
Q

What are the most susceptible cells to ischemic injury?

A

Pyramidal neurons of the cerebral cortex (layers 3,5,6) leading to laminar necrosis

Pyramidal neurons of the hippocampus (long term memory)

Purkinje cells in the hippocampus

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24
Q

What is the definition of an ischemic stroke?

A

Regional ischemia of the brain resulting in focal neurologica deficits lasting 24+ hrs (less than 24 hrs= TIA)

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25
What are the major types of ischemic stroke?
Thrombotic (atheroscleosis typically occurs at branch pts.; results in a **pale** necrosis) Embolic stroke (most commonly from the left heart (a fib)- results in a **hemorrhagic** infarct at the cortex periphery) Lacunar stroke
26
Describe Lacunar strokes
Occurs secondary to hyaline arteriolosclerosis, a complication of HTN
27
Ischemic stroke leads to _____ necrosis
liquefactive
28
Describe the main histo findings of an ischemic stroke based on time
Eosinophilic change in the neuron cytoplasm (**red neurons**) at 12 hrs Necrosis (24 hrs), infiltation by neutrophils (days 1-3), and microglial cells (days 4-7 days), gliosis (2-3 weeks)
29
Describe the progression of intracerebral hemorrhage
Bleeding into brain parenchyma classically due to ruputre of **Charcot-Bouchard microaneurysms** of the lentriculostriate vessels (complication of HTN) and most commonly in the BASAL GANGLIA Presents as severe HA, N/V, and eventual coma
30
An LP of a suspected subarachnoid hemorrhage would show what?
**xanthochromia** (yellow hue due to bilirubin)
31
What are the most common causes of subarachnoid hemorrhage?
Most frequently due to ruptured Berry aneurysm (85%)- associated with Marfan syndrome and ADPKD AV malformation
32
What is the classic cause of a subdural hematoma?
Rupture of the middle meningeal artery NOTES: lucid interval, lens shaped CT
33
What are the major risk factors for a subdural hematoma?
age and alcohol (both cause shrinkage of the cerebrum) Most commonly due to rupture of bridging veins
34
What is subfalcine hernation?
displacement of the cingulate gyrus under the falx cerebri (compression of the ACA leads to infarction)
35
What is uncal hernation?
displacement of the temporal lobe uncus under the tenotrium cerebelli causing compression of CN III (look for CN III palsy, **Duret hemorrhages**)
36
What myelinates the CNS?
Oligodendrocytes
37
What myelinates the PNS?
Schwann cells
38
What are leukodystrophies?
Inherited mutations in enzymes neccessary for production of myelin
39
What causes metachromatic leukodystrophy?
due to deficiency of arylsulfatase (AR) (most common leukodystropy) causing accumulation of sulfatides in lysosomes of oligodendrocytes (lysosomal storage disease)
40
What is Krabbe disease?
due to deficiency of galactocerebrosidase (AR) causing galactocerebroside to accumulate in macrophages
41
What causes adrenoleukodystrophy?
due to impaired addition of CoA to long-chain fatty acids (X-linked), causing accumulation of fatty acids resulting in damage of adrenal glands and white matter of the brain
42
What causes MS?
Autoimmune destruction of CNS myelin and oligodendrocytes
43
MS is associated with HLA-\_\_\_
DR2 (most common in regions far from the equator)
44
How does MS present?
Relapsing neurologic deficits with periods of remission (multiple lesions in time and space) **Clinical features include:** Blurred vision in one eye (optic nerve) Vertigo and scanning speech mimicking alcohol intox (brainstem) Internuclear ophthalmoplegia (medial longitudinal fasciculus) Bowel, bladder, and sexual dysfunction Lower extremity loss of sensation or weakness Hemiparesis or loss of unilateral sensation
45
How is MS diagnosed?
MRI reveals plaques LP showing **increased lymphocytes**, increased **immunoglobulins with oligoclonal IgG bands on electrophroesis**, and **myelin basic protein**
46
What is subacute sclerosisng panecephalitis?
Progressive, delibitating encephalitis leading to death due to MMR vaccine/measles
47
What causes progressive multifocal leukoencephalopathy?
JV virus infection of oligodendrocytes (commonly in immunocompromised)
48
What causes central pontine myelinolysis?
Focal demyleination of the pons (anterior brain stem) due to rapid IV correction of hyponatremia (may present as locked in syndrome)
49
What is the most common cause of dementia?
Alzheimer disease
50
What are the symptoms of Alzheimer disease?
Slow-onset memory loss (begins with short-term) and progressive disorientation Loss of learned motor skills and language Personality change
51
What are the most common causes of Alzheimer disease?
52
What are some morphological findings of Alzheimer Disease?
Cerebral atrophy with narrowing of gyri, widening of sulci, and dilation of the ventricles **Neuritic plaques**- extracellular core comprised of AB amyloid with entangled neuritic processes Neurofibrillary tangles- intracellular aggregates of fibers composed of hyperphosphorylated tau protein
53
How is AB amyloid made?
From amyloid precursor protein (APP), which is coded on chromosome 21
54
Neurofibrillary tangles
Neurofibrillary tangles
55
Alzheimer is associated with loss of cholinergic neurons where?
nucleus basalis of Meynert
56
What is the 2nd most common cause of dementia?
Vascular dementia
57
What is Pick Disease?
Degenerative disease of the FRONTAL and TEMPORAL cortex (spares the parietal and occipital lobes) marked by round aggregates of tau protein in neurons
58
What causes Parkinson Disease?
Degenerative loss of dopaminergic neurons in the substantia nigra of the basal ganglia (look for round, esoinophilic inclusions of **a-synuclein** (lewy bodies) in the cortex
59
What causes Huntington Disease?
Degeneration of GABAergic neurons in the caudate nucleus of the basal ganglia (AD disorder of **chrom 4** of expanding trinucleotide (CAG) in the huntingtin gene). Suicide is a common cause of death
60
Are CNS tumors mostly primary or METs?
50-50
61
How might CNS MET tumors present?
as multiple, well circumscribed lesions at the gray-white junction (lung, breast, and kidney are common sources)
62
What are the most common CNS tumors in adults?
glioblastoma multiforme, meningioma, and schwannoma
63
What are the most common CNS tumors in children?
astrocytomas, ependymoma, and medulloblastomas
64
Describe glioblastoma multiforme
A malignany, high-grade tumor of astrocytes (most common primary malignant CNS tumor in adults) usually arises in the cerebral hemispheres, and classically crosses the corpus callosum **(butterfly lesion)**
65
How is the histo of glioblastoma multiforme described?
regions of necrosis surrounded by tumor cells (pseudopalisading) and endothelial cell proliferation GFAP positive; poor prognosis
66
What is a meningioma?
Benign tumor of arachnoid cells (most common benign CNS tumor in adults; more common in women) look for a dural tail
67
Meningioma- described as a **whorling pattern** psammoma bodies may be present
68
Describe schwannomas
Benign tumor of Schwann cells (often at the cerebellopontine angle and involving CN VII or VIII) S-100 positive Bilateral with NF-2
69
Describe oligodendrocytes
Malignant tumor of oligodendrocytes; imaging reveals a calcified tumor in white matter usually involving the frontal lobe (may cause seizures) **Fried-egg appearance** on biopsy
70
What is a pilocytic astrocytoma?
A benign tumor of astrocytes (most common CNS tumor of children; usually arising in the cerebellum) Imaging reveals a cystic lesion with a mural lobule
71
Biopsy of a pilocytic astrocytoma would classically show what?
**Rosenthal fibers**, thick eosinophilic processes of astrocytes GFAP positive
72
What is a medulloblastoma?
Malignant tumor derived from the granular cells of the cerebellum (neuroectoderm) usually arising in small children
73
The histo of medulloblastoma classically shows what?
small, round blue cells and possibly Homer-Wright rosettes
74
What is an ependymoma?
Malignant tumor of ependymal cells (usually in children) most commonly in the 4th ventricle **Perivascular pseudorosettes** are a classic biopsy findings
75
What tumor arises from the epithelial remnants of Rathke's pouch?
Craniopharyngioma (benign but can recur)

STEP 1 Pathoma (18 decks)

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