Introduction to Neuropathology and Mass Lesions Flashcards

Question

Hydrocephalus types

Answer 1

Obstructive (non-communicating or internal) Results from blockage of CSF flow w/in the ventricular system Non-obstructive (communicating or external) Results from impaired flow or resorption of CSF outside of the ventricular system Ex Vacuo compensatory enlargement of ventricles due to loss of brain parenchymal volume (atrophy): CSF occupies space once occupied by brain parenchyma. ICP is normal Normal pressure hydrocephalus uncommon syndrome of progressive dementia, urinary incontinence, and disordered gait associated with ventricular enlargement but relatively normal ICP.

Answer 2

normal BBB acts as physiologic barrier preventing ingress of most large or charged molecules, e.g., many drugs cannot pass through the normal BBB BBB is thought to mature later in gestation but is generally present at birth: recall that bilirubin in premature infants with hyperbilirubinemia can pass into the CNS and cause damage to the basal ganglia (kernicterus) BBB breakdown occurs from many forms of inflammation or injury and can be recognized by neuroradiologists using “contrast agents”; this is known as “enhancement” and facilitates recognition of lesions on CT or T1 MRI scans

Answer 3

vasogenic edema: predominantly affects white matter and is due to increased interstitial fluid resulting from BBB breakdown, e.g., caused by inflammation, tumor, etc. cytotoxic edema: predominantly affects gray matter and reflects cellular swelling resulting from cell membrane ion pump dysfunction (usually due to energy failure), e.g., hypoxic/ischemic injury to neurons or glia periventricular interstitial edema: predominantly affects periventricular white matter and results from increased ventricular pressure (obstructive hydrocephalus)

Answer 4

TISSUE: meninges, brain parenchyma & interstitial fluid (~80%) VASCULAR: blood vessels and intravascular blood (~10%) CSF: intraventricular, interstitial, and subarachnoid (~10%)

Answer 5

Increased intracranial pressure ( ICP): Because the brain is confined within a rigid container (skull), any increase in one of the intracranial components (tissue, blood, CSF) must occur at the expense of the other two in order to maintain normal ICP. This is known as the Monro-Kellie hypothesis. When the compliance of the three components is exceeded, ICP begins to rise exponentially, if volume continues to increase.

Answer 6

CPP = MAP – ICP

Answer 7

Cerebral perfusion pressure (CPP) is autoregulated to remain stable. CPP = MAP (mean arterial pressure) – ICP. Up to a point, the body can maintain CPP by increasing MAP and dilating cerebral blood vessels. When ICP exceeds MAP, perfusion becomes inadequate to maintain brain function.

Answer 8

* headache (especially morning headache) * projectile vomiting * papilledema and loss of vision * cardiorespiratory physiologic changes (“Cushing response”) sinus bradycardia irregular respirations (Cheyne-Stokes) systolic hypertension * decline in level of consciousness (drowsiness progressing to coma) * neurogenic pulmonary edema * focal neurologic signs due to tissue shifts (e.g., dilated pupil)

Answer 9

parenchyma: tumors, edema, inflammation, abscess blood: hemorrhage, increased venous pressure, increased intra-arterial volume CSF: overproduction, blockage of CSF flow or resorption

Answer 10

usually treated by creating hyperventilation-induced hypocarbia, by administering intravenous mannitol to create an osmotic gradient, by administering barbiturates, or by administering corticosteroids to correct vasogenic edema. The exact mechanisms of some of these interventions are poorly understood.

Answer 11

When intracranial pressure exceeds arterial perfusion pressure, vascular perfusion stops and ischemia and brain death ensue. If the comatose patient is maintained on life support, the dead, non-perfused brain then undergoes autolysis (known as “respirator brain”). Such individuals show the clinical syndrome of “brain death”. In some individuals, enough brainstem/hypothalamic function may persist to permit spontaneous ventilation, autonomic control, sleep-wake cycles, and even preservation of eye movements, but usually without conscious awareness (“persistent vegetative state”).

Answer 12

Herniated Part Opening Effects Cingulate gyrus Subfalcine Compression of anterior cerebral artery

Answer 13

Herniated Part Opening Effects Uncus (medial temporal lobe) Tentorial incisure Compression of midbrain & CN III: coma, dilated pupil, duret hemorrhage

Answer 14

Herniated Part Opening Effects Dienchephalon & medial temporal lobes Tentorial incisure Compression of thalamus & midbrain: coma, posturing, hydrocephalus

Answer 15

Herniated Part Opening Effects Cerebellar tonsils & medulla Foramen magnum Compression of medulla: apnea, acute hydrocephalus, loss of consciousness