Term
| general concepts when dealing with toxic/metabolic conditions |
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Definition
symmetry
selective vulnerability |
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Term
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Definition
right and left sides are usually affected equally
focal symptoms are UNlikely
(though not impossible to be asymmetric if the brain was asymmetric at baseline) |
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Term
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Definition
| certain cell types or brain regions are more sensitive than other to particular toxins or metabolic abnormalitites |
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Term
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Definition
| can occur whenever there is a substantial drop in oxygenation or cardiac output |
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Term
global hypoxia/ischemia
areas at risk |
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Definition
affects neurons more than glia
cortical neurons - layers 3 and 5; "laminar necrosis"
pyramidal neurons in CA1 of hippocampus
Purkinje cells of cerebellar cortex
(basal ganglia, dentate nuclei or cerebellum, inferior olivary nuclei) |
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Term
global hypoxia/ischemia
pathology |
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Definition
thinner paler gray matte in areas of laminar necrosis
eosinophilic, collapsed cytoplasm with pyknotic nuclei and indistinct nucleoli
(looks similar to stroke) |
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Term
global hypoxia/ischemia
clinical features |
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Definition
with brief ischemic/hypoxic event:
-syncope
-light headedness
-presyncope
-rapid return to baseline
prolonged event:
-mental status changes (mild confusion to coma)
-impaired new memory formation common
-may have permanent mental status change, epilepsy, myoclonus or ataxia |
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Term
global hypoxia/ischemia
potential consequences |
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Definition
mental status changes (due to diffuse cortical involvement)
-come to mild memory impairment
seizures
ataxia
myoclonus |
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Term
global hypoxia/ischemia
pathophysiology |
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Definition
same as the mechanisms of injury due to focal ischemia
abnormal electrical excitability, impaired regulation of intracellular calcium, accumulation of neurotoxic excitatory amino acids NTs, abnormal gene expression, apoptosis, and edema
diffuse process, the edema commonly causes increased ICP, which can progress to transtentorial herniation |
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Term
global hypoxia/ischemia
diagnoses |
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Definition
usually suggested by clinical setting
these patients often have multiple medical problems |
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Term
global hypoxia/ischemia
management |
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Definition
reversal of hypoxia/ischemia and correction of underlying cause asap
no interventions available to reverse any neurologic damage that has occurred
management focused on patient's overall medical condition |
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Term
carbon monoxide poisoning
clinical features |
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Definition
ACUTE
carboxyhemoglobin 10-20%: headache, dizziness, visual disturbances, confusion, nausea, ab pain, weakness
carboxyhemoglobin 20-40%: cardiac disturbances, dyspnea, vomiting, loss of consciousness
carboxyhemoglobin 40-60%: coma, seizures, respiratory impairment
SUBACUTE
headache, fatigue, dizziness, paresthesias, ches pain, palpitations, visual disturbances, difficulty concentrating |
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Term
carbon monoxide poisoning
sequelae |
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Definition
15-40% of pt who recover from acute or subacute poisoning develop delayed sequelae ~1-4 weeks after the initial exposure
apathy, memory impairment, bizarre behavior, mutism, parkinsonism, choreoathetosis, dystonia |
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Term
carbon monoxide poisoning
pathophysiology |
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Definition
CO binds to hemoglobin with 200x the affinity for oxygen
Left shift oxy dissociation curve = reduced oxy deliver to tissues |
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Term
carbon monoxide poisoning
areas at risk |
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Definition
preferentially involve:
-globus pallidus
-internal capsule
-hippocampus
-cortex
(same areas of involvement as hypoxia) |
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Term
carbon monoxide poisoning
pathology |
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Definition
hours: brain swollen, congested, cherry red
1-2 days: hemorrhage in globus pallidus and petechial hemorrhage in white matter
days-weeks: lesion in the GP appear necrotic or cavitated
Micro: foci of necrosis and/or perivascular hemorrhage in affected areas |
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Term
carbon monoxide poisoning
diagnosis |
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Definition
acute - straightforward because of clinical setting
subacute - more difficult, depends of awareness of clinical syndrome
direct spectroscopic measurement of carboxyhemoglodin level in blood is most reliable |
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Term
carbon dioxide poisoning
management |
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Definition
immediate removal from site of CO exposure and given 100% O2 by mask
refer for hyperbaric oxygen therapy if loss of consciousness or carboxyhemoglobin level > 30% |
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Term
thiamine deficiency
clinical features |
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Definition
occurs because of poor intake, malabsorption, or increased metabolic requirement
acutely: Wernicke's encephalopathy
chronically: Korsakoff syndrome |
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Term
| Wernicke's excephalopathy |
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Definition
classic triad: confusion, opthalmoplegia, ataxia
more likely in someone who is metabolically challenged |
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Term
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Definition
chronic thiamine deficiency
amnesia - inability to form new memories
confabulation - tendency to create fictional memories
difficulty with planning, directing, attention, problem-solving
often in chronic alcoholics who have a co-existing dementia |
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Term
thiamine deficiency
pathophysiology |
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Definition
thiamine is precursor for TPP (thiamine pyrophosphate), a cofactor of several critical enzymes in the TCA cycle
deficiency results in insufficient energy production; trouble utilizing glucose
often occurs after periods of high metabolic demand, esp after refeeding or IV glucose --> always admin thiamine along with IV glucose in emergency setting |
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Term
thiamine deficiency
areas at risk |
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Definition
mamillary bodies
areas that tend to border 3rd & 4th ventricle, cerebral aqueduct:
medial thalamic nuclei, floor of 3rd ventricle, periaqueductal region, colliculi, nuclei in the pontomedullary tegmentum |
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Term
thiamine deficiency
pathology |
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Definition
involved region slightly shrunken, brown discoloration (hemosiderin deposition)
maye petechial hemorrhages
acute lesions are edematous, preservation of neurons
chronic lesions gliotic and slightly spongioticm mild loss of neurons |
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Term
thiamine deficiency
diagnosis |
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Definition
recognition of clinical syndromes
extensive testing not often needed - tx is cheap and safe |
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Term
thiamine deficiency
management |
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Definition
| parenteral treatment with thiamine |
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Term
vitamin B12 (cyanocobalamin) deficiency
clinical features |
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Definition
from malabsorption (usually not inadequate intake)
neurologic manifestations develop over a period of months to years
paresthesia lower limbs, gait disturbances, ataxia, upper limb sensory symptoms, poss reduced position/viration, Lhermitte's phenomenon
visual and mental status changes |
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Term
vitamin B12 deficiency
pathophysiology |
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Definition
Vit B12 is cofactor for two major physiologic reactions
methylmalonic coA --> succinyl coA (TCA cycle)
homocysteine --> methionine (folate dependent; needed for methylation of myelin basic protein and other CNS proteins) |
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Term
vitamin B12 deficiency
pathology |
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Definition
subacute combined degeneration of the spinal cord
-degeneration and spongy vacuolation of both ascending and descending pathways
-posterior columns in thoracic region
progresses with myelin breakdown, axonal degeneration, macrophage infiltration, astrocytic gliosis |
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Term
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Definition
serum level of vitamin B12 below normal rage is reliable indicator
however normal blood levels may still be deficient if not physiologically enough for that person
measurement of methylmalonic acid and homocysteine more reliable -- elevated if deficient |
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Term
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Definition
most common cause of vitamin B12 deficiency
immune-mediated destruction of gastric parietal cells (produce intrinsic factor)
intrinsic factor necessary for vit B12 absorption in ileum
tested for by an assay for antibody to intrinsic factor |
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Term
vitamin B12 deficiecny
management |
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Definition
oral supplements can treat deficiency from inadequate intake
IM cobalamin for pernicious anemia |
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Term
hepatic enecephalopathy
clinical features |
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Definition
patients with hepatic failure frequently develop cerebral dysfunction
fluctuating attention
confusion
somnolence-->stupor-->coma
asterixis |
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Term
hepatic encephalopathy
pathogenesis |
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Definition
unknown
hyperammonemia is a major factor
toxins escape hepatic detoxification and enter the systemic circulation
increased levels of endogenous benzodiazepine receptor ligands; alterations in the metabolism of cerebral serotonin, dopamine, glutamate
can be precipitated by heavy protein load to the liver |
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Term
hepatic encephalopathy
pathology |
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Definition
Alzheimer's type II astrocytes
enlarged vesicular nucleus, marginated chromatin, scanty cytoplasm |
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Term
hepatic encephalopathy
areas affected |
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Definition
cortex
basal ganglia
thalamus, hypothalamus, subthalamus
dentate nucleus of cerebellum |
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Term
hepatic encephalopathy
diagnosis |
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Definition
often apparent from clinical setting
elevated serum ammonia
elevated CSF glutamine
characteristic EEG abnormality - triphasic waves |
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Term
hepatic encephalopathy
management |
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Definition
directed toward reducing ammonia levels
laxative to help send protein out bowel instead of to liver (lactulose) |
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Term
central pontine myelinolysis (CPM)
clinical features |
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Definition
limb weakness progressing over days-weeks
confusion, abnormal eye movement, dysarthria, dysphagia
hypotension, seizures, dystonia, choreoathetosis |
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Term
central pontine myelinolysis (CPM)
pathogenesis |
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Definition
monophasic demyelinating disease predominantly affecting basis pontis
usually in the setting of rapid correction of hyponatremia
mechanism unknown |
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Term
central pontine myelinolysis (CPM)
pathology |
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Definition
focal, gray region of myelin destruction in the basis pontis (anterior pons) - dymelination through crossing fibers of tracts in pons
active demyelination with reactive astrocytes and large numbers of foamy lipid-laden macrophages
contain only scanty lymphcytes |
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Term
central pontine myelinolysis (CPM)
diagnosis |
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Definition
based primarily on recognition of the typical clinical syndrome in the appropriate clinical setting
demyelinating lesions in characteristic locations on MRI can help |
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Term
central pontine myelinolysis (CPM)
management |
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Definition
no specific treatment know to affect course
aggressive support is indicated if identified |
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