Central Nervous System Flashcards
changes seen following acute CNS hypoxia/ischemia, severe hypoglycemia,
and other acute insults
THE EARLIEST MORPHOLOGIC MARKERS OF NEURONAL DEATH
evident by 6 to 12 hours after an irreversible hypoxic/ischemic insult
Acute neuronal injury (“red neurons”)
shrinkage of the cell body
pyknosis of the nucleus
disappearance of the nucleolus
loss of Nissl substance
intense cytoplasmic eosinophilia
refers to neuronal death that occurs as a result of a progressive
disease of months to years duration, as is seen in slowly evolving
neurodegenerative diseases such as amyotrophic lateral sclerosis
and Alzheimer disease.
Subacute and chronic neuronal injury (“degeneration”)
change observed in the cell body during regeneration of the axon
Axonal reaction
best seen in ANTERIOR horn cells of the spinal cord when motor axons are cut or seriously damaged
refers to degeneration of axons after disruption of nerve fibers
Wallerian degeneration
The most important histopathologic marker of CNS injury, regardless of etiology
characterized by hypertrophy and hyperplasia of ASTROCYTES
GLIOSIS
occurs when unilateral or asymmetric expansion of a cerebral hemisphere displaces the cingulate gyrus under the falx.
compression of the anterior cerebral artery and its branches –>
secondary infarcts.
SUBFALCINE (CINGULATE) HERNIATION
herniating part: CINGULATE
herniation through: UNDER THE FALX CEREBRI
occurs when the medial aspect of the temporal lobe is compressed
against the free margin of the tentorium
COMPRESSED STRUCTURES:
CN III
PCA
contralateral cerebral peduncle
DURET HEMORRHAGES - brainstem and pons
TRANSTENTORIAL (UNCAL, MESIAL TEMPORAL) HERNIATION
herniating part: MEDIAL ASPECT OF TEMPORAL LOBE
herniation through: TENTORIUM CEREBELLI
KERNOHAN PHENOMENON
refers to displacement of the cerebellar tonsils through the foramen magnum
life-threatening because it causes brainstem compression and
compromises vital respiratory and cardiac centers in the medulla
COMPRESSED STRUCTURES:
brainstem
TONSILLAR HERNIATION
herniating part: CEEBELLAR TONSILS
herniation through: FORAMEN MAGNUM
cardiac and respiratory depression
MC CNS malformations
NEURAL TUBE DEFECTS
malformation of the anterior end of the neural tube that leads to absence of most of the brain and calvarium
Forebrain development is disrupted at approximately
28 days of gestation
all that remains in its place is the area cerebrovasculosa - flattened remnant of disorganized brain tissue with admixed ependyma, choroid plexus, and
meningothelial cells
ANENCEPHALY
extrusion of malformed brain tissue through a midline defect in the cranium
ENCEPHALOCELE
OCCIPUT - common location
MC neural tube defects may be an asymptomatic bony defect (spina bifida occulta)
SPINAL DYSRAPHISM OR SPINA BIFIDA
spectrum of malformations characterized by incomplete separation of the cerebral hemispheres across the midline
midline facial abnormalities - cyclopia
absence of the olfactory cranial nerves and related structures
HOLOPROSENCEPHALY
ASSOCIATIONS:
Trisomy 13
Absence of white matter bundles that carry cortical projections from one hemisphere to another
Agenesis of the corpus callosum
POSTERIOR FOSSA ANOMALIES
less severe disorder
low-lying CEREBELLAR TONSILS extend down into the VERTEBRAL CANAL
may be a silent abnormality or may become symptomatic
because of impaired CSF flow and medullary compression
Chiari type I malformation
POSTERIOR FOSSA ANOMALIES
SMALL POSTERIO FOSSA
misshapen midline cerebellum with downward extension of vermis through the foramen magnum
hydrocephalus
lumbar myelomeningocele
Other associated changes may include
caudal displacement of the medulla, malformation of the tectum,
aqueductal stenosis, cerebral heterotopias, and hydromyelia
Arnold-Chiari malformation (Chiari type II malformation)
POSTERIOR FOSSA ANOMALIES
SMALL POSTERIOR FOSSA
misshapen midline CEREBELLUM with downward extension of vermis through the foramen magnum
hydrocephalus
lumbar myelomeningocele
Arnold-Chiari malformation (Chiari type II malformation)
POSTERIOR FOSSA ANOMALIES
enlarged posterior fossa
ABSENCE or HYPOPLASIA of cerebellar vermis
CYSTIC DILATATION of the 4th ventricle
Dandy Walker Malformation
Neurons sensitive to ischemia
Pyramidal layer of hippocampus (CA1: Sommer sector)
Cerebellar Purkinje cells
Pyramidal cells of cerebral cortex
Common sites of hypertensive intraparenchymal hemorrhage
PUTAMEN
thalamus
pons
cerebellar hemispheres
MC clinically significant vascular malformations
10-30 y/o
MALES
SEIZURE
intracerebral hemorrhage
SAH
ARTERIOVENOUS MALFORMATION
posterior branches of MCA
(+) neutrophils
DECREASED sugar
INCREASED protein
(+) culture
ACUTE PYOGENIC MENINGITIS
(+) lymphocytic - viral
(+) neutrophils - chemical
NORMAL sugar
INCREASED protein
(-) culture
ACUTE ASEPTIC MENINGITIS
(+) mononuclear
N or DECREASED sugar
MARKED INCREASED protein
(+) MTB
TUBERCULOUS MENINGITIS
Signs of meningeal irritation
Nuchal rigidity
(+) Brudzinski sign
(+) Kernig sign
chronic meningitis involving the base of the brain and more variably the cerebral convexities and spinal leptomeninges
MENINGOVASCULAR NEUROSYPHILIS
caused by invasion of the brain by T. pallidum
manifests as insidious but progressive cognitive impairment associated with mood alterations (DELUSIONS OF GRANDEUR) that terminate in severe dementia (general paresis of the insane)
PARETIC NEUROSYPHILIS
the result of damage to the sensory axons in the dorsal roots
impaired joint position sense and ataxia (locomotor ataxia)
loss of pain sensation –> skin and joint damage (Charcot joints)
“lightning pains”
absence of deep tendon reflexes
TABES DORSALIS
Neuronophagia of the anterior horn motor neurons of the spinal cord
POLIOMYELITIS
widespread neuronal degeneration and an inflammatory reaction that is most severe in the BRAINSTEM
basal ganglia, spinal cord, and dorsal root ganglia may also be involved
RABIES
Pathognomonic microscopic findings in RABIES
cytoplasmic, round to oval, eosinophilic inclusions found in:
NEGRI BODIES
PYRAMIDAL NEURONS OF THE HIPPOCAMPUS
PURKINJE CELLS OF THE CEREBELLUM
autoimmune demyelinating disorder characterized by distinct episodes of neurologic deficits that are separated in time and are attributable to patchy white matter lesions that are separated in space
the MC of the demyelinating disorders
CD4+ hypersensitivity to myelin sheath
MULTIPLE SCLEROSIS
CSF: moderate pleocytosis
mildly elevated protein
increased IgG
OLIGOCLONAL IgG bands
MORPHOLOGY:
multiphasic sclerotic plaques
Common initial manifestation of multiple sclerosis
unilateral involvement of the OPTIC NERVE (OPTIC NEURITIS)
The MC prion disease
rare disorder that manifests clinically as a rapidly progressive dementia
dementia
startle myoclonus
Creutzfeldt-Jakob Disease (CJD)
SPONGIFORM transformation of the cerebral cortex and deep gray matter structures (caudate, putamen)
KURU PLAQUES - extracellular deposits of aggregated abnormal
PrP
Congo red– and PAS-positive and usually occur in the cerebellum
the most common cause of dementia in older adults, with an increasing incidence as a function of age
AB generation - critical event
accumulation of two proteins (Aβ and tau)
APP (Ch21) - Down syndrome region
ApoE (Ch 19) - strong influence
Alzheimer Disease (AD)
TAU - triggers stress response – neuronal injury
AB - forms PLAQUES and TANGLES – elicits inflammatory response
PNEUMONIA - usual terminal event
Brain in patients with Alzheimer shows variable CORTICAL ATROPHY marked by GYRAL NARROWING and SULCAL WIDENING that is most pronounced in
frontal
temporal
parietal lobes
focal, spherical collections of dilated, tortuous, axonal or dendritic processes (dystrophic neurites) often around a central amyloid core, which may be surrounded by a clear halo
deposits of aggregated AB peptides in the neuropil
SPECIFIC FOR AD
NEURITIC PLAQUES
tau-containing bundles of filaments in the cytoplasm of the neurons that displace or encircle the nucleus
NOT specific for AD
correlate better with DEGREE OF DEMENTIA
NEUROFIBRILLARY TANGLES
Basis for cognitive impairment in patients with AD
DECREASED choline acetyltransferase
loss of synaptophysin immunoreactivity
INCREASED amyloid burden
neurodegenerative disease marked by a hypokinetic
movement disorder that is caused by loss of dopaminergic
neurons from the substantia nigra
PALLOR OF SUBSTANTIA NIGRA
PARKINSON DISEASE
tremor
rigidity
bradykinesia
neurodegenerative disease marked by a hypokinetic
movement disorder that is caused by loss of dopaminergic
neurons from the substantia nigra
PARKINSON DISEASE
tremor
rigidity
bradykinesia
Diagnostic hallmark of PD
LEWY BODY (a synuclein)
AD disease caused by degeneration of striatal neurons
characterized by a progressive movement disorder and dementia
jerky, hyperkinetic, sometimes dystonic movements involving all parts of the
body (chorea) are characteristic
affected individuals may later develop bradykinesia and rigidity
HUNTINGTON DISEASE
CAG repeats
atrophy of the caudate nucleus and the putamen
AR disease characterized by progressive ataxia, spasticity, weakness, sensory neuropathy, and cardiomyopathy
generally begins in the first decade of life with gait ataxia, followed by hand clumsiness and dysarthria
Deep tendon reflexes are depressed or absent, but an extensor plantar reflex is typically present
FRIEDREICH ATAXIA
GAA repeats - FRATAXIN
progressive disorder in which there is LOSS OF UMN in the cerebral cortex and LMN in the spinal cord and brainstem
denervation of skeletal muscles –> weakness and atrophy
SOD1 (Ch21) mutation
Amyotrophic Lateral Sclerosis (ALS)
UPPER MOTOR - cerebral cortex; atrophic BA 4,6 (precentral gyrus)
LOWER MOTOR - thinned anterior roots
loss of motor neurons and CN motor nuclei
BUNINA BODIES - PAS (+) cytoplasmic inclusions seen in remaining neurons
corticospinal tract degeneration
