PATHOMA17 - Central Nervous System Pathology Flashcards
What are the developmental anomolies?
1) neural tube defects 2) cerebral aqueduct stenosis 3) Dandy Walker Malformation 4) Arnold Chiari Malformation
What do neural tube defects arise from?
They arise from incomplete closure of the neural tube
What happens to the neural plate early in gestation?
It invaginates to form the neural tube, which runs along the cranial caudal axis of the embryo
Regarding the neural plate, what forms the central nervous system?
The wall of the neural tube forms central nervous system tissue,
In the neural tube, what does the hollow lumen form?
the ventricles and spinal cord canal, and the neural crest forms the peripheral nervous system.
What are neural tube defects associated with?
low folate levels prior to conception
When are neural tube defects detected?
during prenatal care by elevated alpha-fetoprotein (AFP) levels in the amniotic fluid and maternal blood
What is anencephaly?
it is the absence of the skull and brain (disruption of the cranial end of the neural tube)
What does anencephaly lead to?
a frog like appearance of the fetus
What does anencephaly result in?
maternal polyhydramnios since fetal swallowing of amniotic fluid is impaired
What is spina bifida?
It is failure of the posterior vertebral arch to close, resulting in a vertebral defect (disruption of the caudal end of the neural tube).
How does Spina bifida occulta present?
as a dimple or patch of hair overlying the vertebral defect.
How does Spina bifida present?
with cystic protrusion of the underlying tissue through the vertebral defect
What is a meningocele?
protrusion of meninges
What is meningomyelocele?
protrusion of meninges and spinal cord
What is cerebral aqueduct stenosis?
congenital stenosis of the channel that drains cerebrospinal fluid (CSF) from the 3rd ventricle into the 4th ventricle
What does cerebral aqueduct stenosis lead to?
accumulation of CSF in the ventricular space; most common cause of hydrocephalus in newborns
What is the most common cause of hydrocephalus in newborns?
Cerebral aqueduct stenosis
What produces the CSF?
It is produced by the choroid plexus lining the ventricles
Decribe the flow of CSF?
from the lateral ventricles into the 3rd ventricle via the interventricular foramen of Monro, Flows from the 3rd ventricle into the 4th ventricle via the cerebral aqueduct, Flows from the 4th ventricle into the subarachnoid space via the foramina of Magendie and Luschka
What is the cerebral aqueduct?
Allows for the flow from the 3rd ventricle into the 4th ventricle
What allows the CSF to flow from the 4th ventricle into the subarachnoid space?
Via the foramina of Magendie and Luschka
What is the foramen of monro?
Allows for the flow of CSF from the lateral ventricles into the 3rd ventricle
What does cerebral aqueduct stenosis present with?
enlarging head circumference due to dilation of the ventricles (cranial suture lines are not fused)
What is a dandy walker malformation?
Congenital failure of the cerebellar vermis to develop
How does a dandy walker malformation present?
as a massively dilated 4th ventricle (posterior fossa) with an absent cerebellum; often accompanied by hydrocephalus
What is an Arnold chiari malformation?
Congenital extension of cerebellar tonsils through the foramen magnum
What might Arnold Chiari malformation result in?
Obstruction of CSF flow can result in hydrocephalus
What might Arnold chiari malformation occur in association with?
meningomyelocele and syringomyelia
What are the spinal cord lesions?
Syringomyelia, poliomyelitis, Werdnig-Hoffmann disease, amyotrophic lateral sclerosis, Friedreich ataxia
What is syringomyelia?
Cystic degeneration of the spinal cord
What does syringomyelia arise with?
trauma or in association with an Arnold-Chiari malformation
Where does syringomyelia usually occur?
at C8-T1
How does syringomyelia present?
as sensory loss of pain and temperature with sparing of fine touch and position sense in the upper extremities (cape like distribution)
What is the presentation of syringomyelia due to?
involvement of the anterior white commissure of the spinothalamic tract with sparing of the dorsal column
What does syrinx expansion result in?
involvement of other spinal tracts leading to 1. Muscle atrophy and weakness with decreased muscle tone and impaired reflexes 2. Horner syndrome with ptosis (droopy eyelid), miosis (constricted pupil), and anhidrosis (decreased sweating)
Why does the syrinx expansion result in muscle atrophy and weakness with decreased muscle tone and impaired reflexes?
Its due to damage to lower motor neurons of the anterior horn
What is ptosis?
Droopy eyelid
What is miosis?
Constricted pupil
What is anhidrosis?
Decreased sweating
Why does the syrinx expansion lead to horner syndrome with ptosis (droopy eyelid), miosis (constricted pupil), and anhidrosis (decreased sweating)?
It?s due to disruption of the lateral horn of the hypothalamospinal tract
What is poliomyelitis?
Damage to the anterior motor horn due to poliovirus infection
How does poliomyelitis present?
with lower motor neuron signs?flaccid paralysis with muscle atrophy, fasciculations, weakness with decreased muscle tone, impaired reflexes, and negative Babinski sign (downgoing toes)
What is Werdnig-Hoffman disease?
It?s an inherited degeneration of the anterior motor horn and is autosomal recessive
How does Werdnig-Hoffman disease present?
as a floppy baby, death occurs within a few years after birth.
What is amylotrophic lateral sclerosis?
Degenerative disorder of upper and lower motor neurons of the corticospinal tract
In ALS, what does anterior motor horn degeneration lead to?
lower motor neuron signs?flaccid paralysis with muscle atrophy, fasciculations, weakness with decreased muscle tone, impaired reflexes, and negative Babinski sign.
In ALS what does lateral corticospinal tract degeneration lead to?
upper motor neuron signs ? spastic paralysis with hyperreflexia, increased muscle tone, and positive Babinski sign.
What is an early sign of ALS?
atrophy and weakness of hands is an early sign
What distinguishes ALS from syringomyelia?
Lack of sensory impairment
What are most cases of ALS?
they are sporadic, arising in middle age adults
What is present in some familial cases of ALS?
Zinc-copper superoxide dismutase mutation (SOD) is present in some familial cases; leads to free radical injury in neurons
What is Friedreich Ataxia?
Degenerative disorder of the cerebellum and spinal cord
What does degeneration of the cerebellum lead to?
ataxia
What does degeneration of multiple spinal cord tracts lead to?
loss of vibratory sense and proprioception, muscle weakness in the lower extremities, and loss of deep tendon reflexes
What is the cause of Friedreich Ataxia genetically?
Autosomal recessive; due to expansion of an unstable trinucleotide repeat (GAA) in the frataxin gene
What is frataxin?
it is essential for mitochondrial iron regulation; loss results in iron buildup with free radical damage.
How does Friedreich Ataxia present?
in early childhood; patients are wheelchair bound within a few years
What is Friedreich Ataxia associated with?
hypertrophic cardiomyopathy
What does the spinothalamic tract do?
Pain and temperature sensation
What is the first order neuron for the spinothalamic tract?
Peripheral nerves of posterior horn; cell body is in dorsal root ganglion.
What is the second order neuron for the spinothalamic tract?
It arises from posterior horn, immediately crosses over in anterior white commissure, and ascends via the spinothalamic tract to thalamus
What is the third order neuron for the spinothalamic tract?
thalamus to cortex
What is the Dorsal column-medial lemniscus responsible for?
pressure, touch, vibration, and proprioception
What are the first order neurons for the dorsal column-medial lemniscus?
Peripheral nerves to medulla via dorsal column; cell body is in dorsal root ganglion.
What is the second order neuron for the dorsal column-medial lemniscus?
Arises from medulla, crosses over, and ascends via the medial lemniscus to thalamus
What is the third order neuron for the dorsal column-medial lemniscus?
Thalamus to cortex
What is the lateral corticospinal tract responsible for?
voluntary movement
What are the first order neurons for the lateral corticospinal tract?
Pyramidal neurons in the cortex descend, cross over in medullary pyramids, and synapse on the anterior motor horn of the cord (upper motor neuron)
What is the second order neuron for the lateral corticospinal tract?
Arises from the anterior motor horn and synapses on muscle (lower motor neuron)
What are the third order neurons for the lateral corticospinal tract?
None
What is the hypothalamospinal tract responsible for?
sympathetic input of the face
What is the first order neuron for the hyothalamospinal tract?
It arises from the hypothalamus and synapses on the lateral horn at T1
What is the second order neuron for the hypothalamospinal tract?
It arises from lateral horn at T1 and synapses on the superior cervical ganglion (sympathetic)
What is the third order neuron for the hypothalamospinal tract?
Superior cervical ganglion to eyelids, pupil, and skin of face
What is meningitis?
inflammation of the leptomeninges
What do the meninges consist of?
three layers (dura, arachnoid, and pia) that lie between the brain and the skull,
What are the leptomeninges?
Pia and arachnoid together
What is meningitis most commonly due to?
an infectious agent
What are the infectious agents that cause meningitis?
1) Group B streptococci, E coli, and Listeria monocytogenes (neonates) 2) N meningitidis (children and teenagers). Streptococcus-pneumoniae (adults and elderly), and H influenza (non vaccinated infants) 3. Coxsackievirus (children; fecal-oral transmission) 4. Fungi (immunocompromised individuals)
What is the infectious agent causing meningitis for neonates?
Listeria monocytes
What is the infectious agent causing meningitis for children and teenagers?
N. Meningitidis
What is the infectious agent causing meningitis for adults and elderly?
Streptococcus-pneumoniae
What is the infectious agent causing meningitis for non vaccinated infants?
H. Influenzae
What is the infectious agent causing meningitis for children; fecal-oral transmission?
Coxsackievirus
What is the infectious agent causing meningitis for immunocomprimised individuals?
fungi
How does meningitis present?
With a classic triad of headache, nuchal rigidity (neck stiffness), and fever; photophobia, vomiting, and altered mental status may also be present,
How is the diagnosis for meningitis made?
it is made by lumbar puncture (sampling of CSF)
How is a lumbar puncture performed?
by placing a needle between L4 and L5 (level of the iliac crest). Spinal cord ends at L2, but subarachnoid space and cauda equina continue to S2.
What are the layers crossed by the lumbar puncture?
include skin, ligaments, epidural space, dura, and arachnoid.
What are the CSF findings in LP for bacterial meningitis?
neutrophils with low CSF glucose; positive gram stain and culture often identify the causative organism.
What are the CSF findings in LP for viral meningitis?
lymphocytes with normal CSF glucose
What are the CSF findings in LP for fungal meningitis?
lymphocytes with low CSF glucose
Complications are usually seen with what type of meningitis?
bacterial meningitis
What is involved in cerebrovascular disease?
Neurologic deficit due to cerebrovascular compromise; major cause of morbidity and mortality
What is cerebrovascular disease due to?
ischemia (85% of cases) or hemorrhage (15% of eases)
What are neurons dependent on and what are the susceptible to?
serum glucose as an essential energy source and are particularly susceptible to ischemia (undergo necrosis within 3 - 5 minutes).
What is global cerebral ischemia?
Global ischemia to the brain
What are the major etiologies for global cerebral ischemia?
- Low perfusion (e.g., atherosclerosis) 2. Acute decrease in blood flow (e.g., cardiogenic shock) 3. Chronic hypoxia (e.g., anemia) 4. Repeated episodes of hypoglycemia (eg insulinoma)
What are the clinical features for global cerebral ischemia based on?
Its based on duration and magnitude of the insult.
What does mild global ischemia result in?
transient confusion with prompt recovery
What does severe global ischemia result in?
diffuse necrosis; survival leads to a vegetative state
What does moderate global ischemia lead to?
infarcts in watershed areas (eg area lying between regions fed by the anterior and middle cerebral artery) and damage to highly vulnerable regions
In moderate global ischemia, what are the vulnerable regions that may be damaged?
1) Pyramidal neurons of the cerebral cortex (layers 3, 5, and 6) 2) Pyramidal neurons of the hippocampus (temporal lobe) 3) Purkinje layer of the cerebellum
What does damage to the pyramidal neurons of the cerebral cortex (layers 3, 5, and 6) lead to?
laminar necrosis
What does damage to the pyramidal neurons of the hippocampus (temporal lobe) lead to?
Its important in long term memory
What does damage to the purkinje layer of the cerebellum lead to?
It integrates sensory perception with motor control
What is ischemic stroke?
Regional ischemia to the brain that results in focal neurologic deficits lasting > 24 hours
What happens in the symptoms last < 24 hours?
the event is termed a transient ischemic attack (TIA).
What are the subtypes for ischemic stroke?
They include thrombotic, embolic, and lacunar strokes.
What is the thrombotic stroke due to?
rupture of an atherosclerotic plaque
Where does atherosclerosis usually develop?
at branch points (e.g., bifurcation of internal carotid and middle cerebral artery in the circle of Willis).
What does atherosclerosis result in?
a pale infarct at the periphery of the cortex
What is an embolic stroke due to?
thromboemboli.
What is the most common source of emboli?
It is the left side of the heart (e.g., atrial fibrillation).
What does an embolic stroke usually involve?
the middle cerebral artery
What does the embolic stroke result in?
a hemorrhagic infarct at the periphery of the cortex
When does a lacunar stroke occur?
Its secondary to hyaline arteriolosclerosis, a complication of hypertension.
What vessels does lacunar stroke most commonly involve?
lenticulostriate vessels, resulting in small cystic areas of infarction
In a lacunar stroke, what does the nvolvement of the internal capsule lead to?
a pure motor stroke
In a lacunar stroke, what does the involvement of the thalamus lead to?
a pure sensory stroke.
What does ischemic stroke result in?
liquefactive necrosis,
What is an early microscopic finding (12 hours after infarction) for ischemic stroke?
Eosinophilic change in the cytoplasm of neurons (red neurons)
What happens 24 hours into an ischemic stroke?
coagulative necrosis
What happens in days 1-3 in an ischemic stroke?
infiltration by neutrophils
What happens in days 4-7 in an ischemic stroke?
microglial cells enzyme cause liquifactive necrosis