Week 1 - Trachte/Kraft Flashcards
What are the two types of cerebral edema?
- Vasogenic Cerebral Edema
2. Cytotoxic Cerebral Edema
What occurs in Vasogenic Cerebral Edema?
- Increased Vascular Permeability (leaky junctions in vessels –> fill with fluid –> swelling!)
- Fluid shifts into intracellular spaces in the brain
What causes Vasogenic Cerebral Edema?
- Localized edema due to tumor/abscess
- Generalized edema due to trauma
What causes in Cytotoxic Cerebral Edema?
-Cell membrane injury due to hypoxia or metabolic damage
What occurs in Cytotoxic Cerebral Edema?
- Individual cells swell and retain fluid
- Increased intracellular fluid in endothelial cells of the vessels, but cell junctions are okay
- Cells swell due to retained fluid
What is the normal pathway of circulation of CSF starting in the lateral ventricles?
- Made in choroid plexus of lateral ventricles
- Circulates through intraventricular foramen –> 3rd ventricle
- Passes through cerebral aquaduct –> 4th ventricle
- Moves down brainstem via central canal
- Travels laterally to venus dural sinus –> arachnoid granules
- Enters Superior sagittal sinus –> straight sinus –> confluence of sinuses
- Follows Transverse sinus –> sigmoid sinus
- Finally enters INTERNAL JUGULAR VEIN
What is the normal pathway of circulation of CSF starting in the fourth ventricle?
- Made in choroid plexus of fourth ventricle
- Circulates through median aperature
- Travels around Cerebellum
- Empties into occipital sinus –> Confluence of sinuses
- Follows Transverse sinus –> sigmoid sinus
- Finally enters INTERNAL JUGULAR VEIN
What is Noncommunicating Hydrocephalus?
- Blockage in the ventricular system that does not allow CSF flow in that area
- Only part of the ventricular system is enlarged
What are the causes of Noncommunicating Hydrocephalus?
-Congenital malformation, tumor, abscess, hematoma
What is Communicating Hydrocephalus?
- Blockage in subarachnoid space
- Enlarges the entire ventricular system
- Blocks the exit!
What are the causes of Communicating Hydrocephalus?
- Resolving meningitis
- Subarachnoid hemorrhage
- Dural sinus thrombosis
What is Hydrocephalus Ex Vacuo?
- Dilation of the ventricular system due to brain atrophy with compensatory increase in CSF volume
- No blockage in the ventricular system
What are potential causes of Hydrocephalus Ex Vacuo?
- Alzheimer’s disease
- Pick disease
- Being on a ventilator for an extended period of time
What is Increased CSF Production Hydrocephalus?
- Dilation of the ventricular system due to increased CSF production
- Uncommon
What causes Increased CSF Production Hydrocephalus?
Choroid plexus papilloma
What is Normal Pressure Hydrocephalus?
- Reversible enlargement of the ventricles
- May be a form of communicating hydrocephalus
- No cortical atrophy
What are the clinical features of Normal Pressure Hydrocephalus?
- Elderly patient with: gait disturbance, urinary incontinence, and dementia
- Often misdiagnosed as Alzheimer’s disease
What are the causes of increased intracranial pressure?
- Mass effect
- Edema
- Tumor
- Hematoma
What is the problem with increased intracranial pressure?
Compromises blood flow to the brain
What are the symptoms of increased intracranial pressure?
Headache, papilledema, decreased LOC
What are the three main types of herniation that can result from increased intracranial pressure?
- Subfalcine (Cingulate) Herniation
- Transtentorial (Uncinate) Herniation
- Tonsillar Herniation
What are the symptoms of herniation?
- Focal neurologic symptoms
- Respiratory arrest
- Cardiac arrest
- Coma
- Death
What is a Subfalcine (Cingulate) Herniation?
-Expansion of one hemisphere displaces the cingulate gyrus under the falx causing compression of the anterior cerebral artery
What are the specific symptoms of a Subfalcine (Cingulate) Herniation?
- Weakness of limbs
- Aphasia
What is a Transtentorial (Uncinate) Herniation?
- Compression of the Temporal Lobe against the tenorium
- Possibly Affects: CN III, Posterior cerebral artery, brainstem, contralateeral cerebral peduncle
What are the specific symptoms of a Transtentorial (Uncinate) Herniation?
- CN III –> fixed/dilated pupil, impaired ocular movements
- Posterior cerebral artery –> ischemia in primary cortex of vision
- Brainstem –> impaired consciousness due to duret hemorrhages (small ripped vessels)
- Contralateral cerebral peduncle –> Hemiparesis
What is a Tonsillar Herniation?
- Cerebellar tonsils get compressed through the foramen magnum.
- Compression of medulla can be FATAL if vital respiratory and cardiac centers are compromised.
What is the mechanism of action of Acetazolamide?
Carbonic anhydrase inhibitor:
- blocks carbonic anhydrase so cell cannot make H+ and HCO3-
- Lowers pH –> more acidic plasma
- interferes with the sodium pump –> hyperosmolarity in blood thus pulling fluid out of the CSF
What is the mechanism of action of Furosemide?
NKCC pump inhibitor:
- blocks the NKCC pump on the abluminal side
- causes hyperosmolarity in the blood, thus pulling fluid out of the CSF
What is the mechanism of action of Mannitol?
- Small sugar that cannot cross BBB
- Blood becomes hyperosmotic and draws water out of neurons & CSF
What is the best treatment for Vasogenic Cerebral Edema?
- Steroids: Dexamethasone reduces water permiability of tight junctions (transcriptional regulator so it takes awhile to work)
- Mannitol: Osmotic diuretic (osmotic force pulls water across membranes because #particles in blood > #particles in cells or CSF
What is the best treatment for Cytotoxic Cerebral Edema?
Agents that suppress CSF production!
- Acetazolamide
- Furosemide
- Mannitol
