Pathology of the Central Nervous System Flashcards
Three Primary CNS Diseases
- Neural tube defects
- Cerebral edema
- Hydrocephalus
What are Neural tube defects (NTDs)?
a group of disorders characterized by failure of closure of the neural tube
(involve vertebrae and skull, w/ or w/o involvement of meninges, spinal cord, or brain)
What is notably increased with NTDs?
Concentration of alpha-fetoprotein (AFP) in amniotic fluid or maternal serum
What deficiency is associated with NTDs?
maternal folic acid
Six examples of NTDs
- Spina bifida
- Spina bifida occulta
- Spina bifida cystica
- Meningocele
- Meningomyelocele
- Anencephaly
Define Spina bifida
failure of posterior vertebral arches to close
Define Spina bifida occulta
spina bifida with no clinically apparent
abnormalities; defect limited to one
or two vertebrae
Define Spina bifida cystica
spina bifida complicated by herniation
of meninges through a defect
Define Meningocele
herniated membranes consisting of meninges
only
Define Meningomyelocele
portion of spinal cord included in
herniated tissue
Define Anencephaly
marked diminution (sometimes absence) of
fetal brain tissue; usually associated with the absence of overlying skull
73% of pts with spina bifida and related NTDs test positive for ___ ___ ___
hypersensitivity to latex
What is cerebral edema?
an abnormal accumulation of fluid in the
cerebral parenchyma
(results from BBB breakdown or damage)
What initiates damage resulting in cerebral edema? (x5)
- Ischemia (infarction)
- Trauma (head injury)
- Inflammation encephalitis or meningitis
- Cerebral tumors
- Metabolic disturbances (hyponatremia or hypoglycemia)
Cerebral edema results in ___ ___ , and it is associated with raised ___ ___.
cerebral swelling, intracranial pressure
Cerebral edema treatment:
minimizing the formation of edema by use of:
- osmotic agents (mannitol)
- corticosteroids
What is hydrocephalus?
an increase in the volume of CSF within the
brain resulting in the expansion of the cerebral ventricles
Three mechanisms resulting in hydrocephalus:
- Obstructive hydrocephalus; obstruction to the flow of CSF (most common)
- Impaired absorption of CSF at arachnoid villi (rare)
- Overproduction of CSF by choroid plexus neoplasms (very rare)
Obstructive hydrocephalus can be ___ or ___
congenital, acquired
Obstructive hydrocephalus is subdivided into:
- Non-communicating hydrocephalus: obstruction within the ventricular system leading to blockage of CSF flow from the ventricles to the subarachnoid space.
- Communicating hydrocephalus: extraventricular obstruction within subarachnoid space.
Five examples of traumatic brain injury:
- Contusions
- Concussions
- Traumatic vascular injury
- Epidural hematoma
- Subdural hematoma
Define brain contusions
(parenchymal) contusion caused by rapid tissue
displacement, disruption of vascular channels, and subsequent hemorrhage, tissue injury, and edema.
Contusions occur ___ the site of impact and/or ___ ___ the site of impact
at, opposite to
Contusions at the site of impact are called ___ ___. Contusions opposite to the site of impact on the other side of the brain are called ___ ___.
coup injury, countercoup injury
Brain contusions morphology: shape
On cross-section, contusions are wedge-shaped, with the widest aspect closest to the point of impact
Brain contusions morphology: blood extravasation
Within a few hours of injury, blood extravasates throughout the involved tissue, across the width of the cerebral cortex, and into the white matter and subarachnoid spaces
Brain contusions morphology: evidence and function
Although functional effects are seen earlier, morphologic evidence of injury in the neuronal cell body (nuclear pyknosis, cytoplasmic eosinophilia, cellular disintegration) takes about 24 hours to appear
Brain contusions morphology: inflammatory response
follows usual course, with neutrophils preceding the appearance of macrophages
Define concussion
describes reversible altered consciousness from
head injury in the absence of contusion
(transient neurologic dysfunction)
Four characteristic of concussion
- loss of consciousness,
- temporary respiratory arrest
- loss of reflexes
- amnesia for the even (unknown pathogenesis)
What is traumatic vascular injury (TVI)?
CNS trauma often directly disrupts vessel walls, leading to hemorrhage
What does TVI classification depend on?
the affected vessel, the hemorrhage and hematoma formation
Four types of TVI
- epidural
- subdural
- subarachnoid
- intraparenchymal (intracerebral)
Epidural hematoma pathophysiology in infants vs. children and adults
Dural vessels (especially the middle meningeal artery) are vulnerable to traumatic injury:
- In infants, traumatic displacement of the easily deformable skull may tear a vessel, even in the absence of a skull fracture.
- In children and adults, by contrast, tears involving dural vessels almost always stem from skull fractures.
What can blood accumulation from a torn vessel result in?
under arterial pressure, it can dissect the tightly applied dura away from the inner skull surface producing a hematoma that compresses the brain
surface
What is the effect of an epidural hematoma on the patient?
Clinically, patients can be lucid for several hours between the moment of trauma and the development of neurologic signs
Epidural hematoma treatment and consequence
An epidural hematoma may expand rapidly and constitutes a neurosurgical emergency necessitating prompt drainage and repair to prevent death
What is subdural hematoma?
Rapid movement of the brain during trauma can tear the bridging veins that extend from the cerebral hemispheres through the subarachnoid and subdural space to the dural sinuses
Which age groups are at risk of subdural hematomas?
Elderly and infants
Pathophysiology of hematoma in elderly pts.
Bridging veins disruption produces bleeding into the subdural space.
Elderly patients with brain atrophy have a higher rate of subdural hematomas:
– The bridging veins are stretched out, and the brain has additional space within which to move,
Pathophysiology of hematoma in infant pts.
Bridging veins disruption produces bleeding into the subdural space.
Infants are more susceptible to subdural hematomas because their bridging veins are thin-walled.
When do subdural hematomas become clinically evident?
within the first 48 hours after injury
Where are subdural hematomas most common?
over the lateral aspects of the cerebral hemispheres and may be bilateral
Neurologic signs of subdural hematomas.
- Attributable to the pressure exerted on the
adjacent brain - Symptoms may be localizing but more often are
nonlocalizing (headache, confusion, and
slowly progressive neurologic deterioration)
What is the treatment of symptomatic subdural hematomas?
surgical removal of the blood and associated reactive tissue
Subdural hematomas commonly _____ during the healing process (resulting in ___ ___ ___).
rebleed, chronic subdural hematomas
Subdural hematoma and underlying brain morphology
- An acute subdural hematoma appears as a collection of freshly clotted blood apposed to the contour of the brain surface, without extension into the depths of sulci.
- The underlying brain is flattened, and the subarachnoid space is often clear.
Venous bleeding is self-limited with breakdown and organization of the hematoma taking place over time resulting in three morphological stages:
- Subdural hematomas organize by lysis of the clot in about 1 week
- growth of granulation tissue from the dural surface into the hematoma in about 2 weeks
- fibrosis that occurs in 1 to 3 months
(Fibrosing lesions may eventually retract, leaving only a thin layer of connective tissue (“subdural membranes”).
Define cerebrovascular disease (CVD)
injury to the brain as a consequence of altered blood flow
What are the three types of CVD?
- Cerebral infarctions
- Intracerebral (Intraparenchymal) Hemorrhage
- Subarachnoid Hemorrhage
___ is the clinical designation that applies to all CVD conditions, particularly when symptoms begin acutely
Stroke
What are the two possible mechanisms through which CVD develops?
- Hypoxia, ischemia, and infarction
- Hemorrhage
Which is a amore common etiology in the brain, an embolism or a thrombosis?
An embolism, but occur
Hypoxia, ischemia, and infarction can either be a ___ process or ___, with the clinical manifestations determined by the ___ of brain affected
global, focal, region
Hemorrhage result from ___ of CNS vessels.
rupture
Two common etiologies of hemorrhage include:
- hypertension
- vascular anomalies (aneurysms and malformations)
Cerebral infarctions are most commonly caused by ___ ____ or ___ ___ ___ ___
Atherosclerotic thrombi, Emboli of cardiac origin
Atherosclerotic thrombi are usually due to ___ ___ ___ ___ (___ ___), most commonly at the ___ ___
carotid artery atherosclerotic disease (plaque rupture), carotid bifurcation
Emboli of cardiac origin are secondary to: (x3)
– valvular (especially, mitral valve) pathology
– acute anterior myocardial infarctions or congestive cardiomyopathies resulting in cardiac mural hypokinesias or akinesias with thrombosis
– cardiac arrhythmias (typically atrial fibrillation)
The extent of a cerebral infarction is determined by: (x4)
- site of the occlusion
- size of the occluded vessel
- duration of the occlusion
- collateral circulation
Neurologic abnormalities depend on: (x2)
- the artery involved
- its area of supply
The gross appearance of an ischemic cerebral infarct varies with ___
time
Describe the appearance of brain tissue effected by an infarction as time progresses
- 1st 6 hrs of irreversible injury: there is little change in appearance
- by 48 hrs: the tissue becomes pale, soft, and swollen, and the corticomedullary junction becomes indistinct.
- from 2 to 10 ds: the brain becomes gelatinous and friable, and the previously ill-defined boundary between normal and
infarcted tissue becomes more distinct as edema resolves in the viable adjacent tissue. - from 10 ds to 3 ws, the tissue liquefies (i.e.,
liquefaction necrosis), eventually leaving a fluid-filled cavity that continues to expand until all of the dead tissue is removed.
___ is the risk factor most commonly associated with clinically significant deep brain intracerebral (Intraparenchymal) hemorrhages
Hypertension
Hypertension can cause vessel wall abnormalities (making them weaker and more vulnerable to rupture), including:
- accelerated atherosclerosis in larger arteries,
- hyaline arteriolosclerosis in smaller arteries,
- proliferative changes and frank necrosis of
arterioles (severe cases)
Five locations where Hypertensive intraparenchymal hemorrhage can originate in:
- putamen (50 - 60% of cases)
- thalamus
- pons
- cerebellar hemispheres (rarely)
- other regions of the brain
Rupture of an artery within brain tissue leads to ___ of ___, which ___ ___ tissue and causes ___ intracranial volume until the resulting tissue ___ halts the bleeding
extravasation, blood, displaces brain, increased, compression
What is the most frequent cause of clinically significant subarachnoid hemorrhage?
rupture of a saccular “berry” aneurysm in a cerebral artery
(most common type)
___ ___ ___ is the most common type of intracranial aneurysm
Saccular (“berry”) aneurysm
(The vessels within the circle of Willis often are affected)
Subarachnoid hemorrhage may also result from: (x4)
- extension of a traumatic hematoma
- rupture of a hypertensive intracerebral hemorrhage into the ventricular system
- vascular malformation (e.g., arteriovenous malformation, cavernous malformation)
- hematologic disturbances, and CNS tumors
Name the eight infections CNS diseases
- Bacterial Meningitis
- Viral (Aseptic) Meningitis
- Brain Abscess
- Chronic Meningoencephalitis
- Viral Encephalitis
- Slow Virus Diseases
- Fungal Infections
- Protozoal Infections
- Prion Diseases
Meningitis is ___ of the meninges
inflammation
Define Acute pyogenic (bacterial) meningitis
Infection of the leptomeninges (pia and arachnoid mater), and the CSF, which diffusely affects the whole meninges and subarachnoid space.
What is the most serious form of meningitis?
Bacterial Meningitis
Two organisms that cause Bacterial Meningitis are:
Neisseria meningitidis and Streptococcus pneumoniae
What is the timeline of symptom development for bacterial meningitis?
- About 25% have symptoms that develop over 24 hours
- The remainder generally
become ill over 1 to 7 days
What are the classic symptoms of bacterial meningitis in adults? (x8)
- headache
- stiff neck (nuchal rigidity)
- fever and chills
- vomiting
- photophobia
- confusion
- seizures (in ~ 33% of cases)
- history of a recent upper respiratory infection
Meningitis caused by ___ ___ may progress to a___ with multiple organ involvement, and may be associated with ___, petechial, or purpuric skin rash.
N. meningitidis, meningococcemia, maculopapular
Meningococcemia is sometimes complicated by the ___ ___ syndrome
Waterhouse-Friderichsen
What is Waterhouse-Friderichsen syndrome?
hemorrhagic destruction of the adrenal cortex, acute hypocorticism with circulatory collapse, and DIC
Other complications of meningitis include: (x4)
- ventriculitis,
- intracerebral abscess
- cerebral infarction
- subdural empyema (a collection of pus in the subdural space)
Diagnosis of bacterial meningitis:
- CSF is cloudy due to increased numbers of neutrophils
- CSF protein levels increase and
glucose concentrations fall
Treatment of bacterial meningitis:
vigorous intravenous antibiotic therapy
prevention of bacterial meningitis:
a vaccine is available for meningitis caused by Neisseria meningitidis
prognosis of bacterial meningitis:
- mortality ranges from 3% for H. influenzae to 60% for Strep. pneumoniae
- highest in the very young and
the elderly
Long-term complications of bacterial meningitis: (x9)
In addition to subtle CNS changes:
- nerve deafness
- cortical blindness
- paralysis
- muscular hypertonia
- ataxia
- complex seizure disorders
- learning disabilities
- obstructive hydrocephalus
- cerebral atrophy
Three facts about viral (aseptic) meningitis:
- the most common cause of meningitis. - it is a benign and self-limiting illness
- less severe than bacterial meningitis
Viral meningitis may occur as a ___ of viral infection, (e.g., ___ or ___)
complication, mumps, measles
The two common causative organisms of viral meningitis are:
- enteroviruses (e.g., echoviruses, coxsackie viruses, and polioviruses)
- mumps virus (paramyxovirus)
Symptoms of viral meningitis:
acute onset of:
- headache
- fever
- nuchal rigidity
- irritability
- rapid development of meningeal irritation
Diagnosis of viral meningitis:
- the CSF is clear and colorless
- CSF contains excess lymphocytes, moderately increased protein, and normal glucose concentration
Treatment of viral meningitis:
palliative care (control of symptoms) only
Prognosis of viral meningitis:
Complete recovery usually occurs without specific therapy
