Meninges And Blood Flow Flashcards
CSF Functions
Provides buoyancy to protect against sudden movements
Constant pressure
Antibacterial
Controls extracellular fluid of brain
Clears waste and toxins during sleep
Circumventricular organs
Regions where the blood-brain barrier is interrupted so that brain can respond to changes in blood chemistry
Meninges in order
Outside in:
Dura (periosteal, meningeal)
Arachnoid
Pia
Cisterns
Enlarged subarachnoid space where CSF collects
Lumbar puncture is contraindicated if there is increased intracranial pressure because
If there is a mass in the brain, do not want to pull fluid because it could cause a vacuum and thus herniation of brain
Lumbar puncture in adults vs. children
In adults: L3-L4
In children: L4-L5
Difference is because spinal cord is goes down to further vertebrae in children than in adults. Changes as child grows.
Falx cerebri
Inner dural fold separating cerebral hemispheres
Falx cerebelli
Inner dural fold separating two hemispheres of cerebellum
Tentorium cerebelli
Inner dural fold separating the posterior cerebral hemispheres and the cerebellum
Posterior fossa
Cavity formed by occipital bone as base and tentorium cerebelli as roof, which contains the cerebellum and the brainstem
Tentorial notch
Narrow opening in tentorium cerebelli where midbrain passes through
Epidural hematoma
usually caused by trauma causing the middle meningeal artery to break
Period of lucidity before brain herniation
Lens shape on MRI
Subdural hematoma
Retraction of brain (in older people) puts tension on bridging veins, which may cause them to rupture
Crescent shape on MRI
Subarachnoid hemorrhage
Bleeding into subarachnoid space usually due to trauma
In non-trauma cases, cased by A-V malformation or ruptured aneurysm
Sudden onset of severe headache
Most common site of aneurysm
Branch points of arteries
In men: anterior communicating artery
In women: posterior communicating artery
Causes of increased intracranial pressure
Tumor Hemorrhage Abscess Edema Hydrocephalus Infection
Symptoms of Increased Intracranial pressure
Headache Altered mental status Nausea, vomiting Downward looking eyes Papilledema Visual loss Diplopia Cushing's triad Skull expansion (in children)
Cushing’s triad
Symptom of increased intracranial pressure
Causes hypertension, bradycardia, and irregular respirations
Transtentorial and Central Herniation
Aka uncal herniation
Uncus of temporal lobe herniates through tentorial notch
Triad of symptoms: blown pupil (ipsilateral), hemiplasia (contralateral), and coma
Pupillary response due to the compression of CN III
Coma if there is distortion of midbrain reticular formation that impairs consciousness
Subfalcine herniation
Herniation of parts of brain under the falx cerebri
Tonsillar herniation
Cerebrum herniates through foramen magnum, compressing the medulla, which may lead to respiratory arrest, blood pressure instability, and death
Hydrocephalus definition and types
When there is excess CSF due to overproduction (tumor in choroid plexus), obstructed flow in the ventricles or subarachoid space, or decreased reabsorption by arachnoid granules.
Communicating hydrocephalus: lateral ventricles can still communicate with subarachnoid space
Non-communicating hydrocephalus: flow is obstructed within the ventricular system
Symptoms of hydrocephalus
Headache (especially in the morning because CSF is resorbed less efficiently when lying down)
Neck pain
Decreased cognitive function
Vomiting
Papilledema
Drowsiness
Failure to upward gaze
Ventriculoperitoneal shunt
Tube inserted surgically to let CSF drain out of brain and into abdomen where body can resorb it in order to prevent hydrocephalus and brain damage.
