Neuroanatomy PPT 2-4 Flashcards
What is the main blood supply of the brain.
Internal Carotid artery and Vertebral (basilar) artery
What is the most important factor in getting blood through the brain?
Arterial Blood pressure
Opposed bu intracranial Pressure, blood viscosity and narrowing of the vascular diameter.
Why does cerebral blood flow remain constant despite general pressure changes?
Autoregulation is due to compensatory lowering or raising of vascular resistance.
What branches of the internal carotid artery?
Ophthalmic Posterior Communicating Anterior Choroidal ACA MCA
What is the path of the Internal Carotid Artery?
Carotid Canal–> Petrous Portion of temporal bone–> Roof of the cavernous sinus
What forms the Basilar Artery?
Union of the two vertebra; arteries at the lower border of the pons
What branches of the Basilar Artery?
Pontine Arteries Labyrinthine Artery Anterior-Inferior Cerebellar Artery Superior Cerebellar Artery Posterior Cerebral Artery
What is the Circle of Willis?
What does it consist of?
Networks of arteries, that creates anastomosis between the blood supply of the brain.
Fed by the internal Carotids (anterior circulation) and Vertebrobasilar (posterior circulation).
Major Components of the Circle of Willis and corresponding areas
ACA- supplies medial aspect of the frontal lobes. (lower extremity motor and sensory cortices)
Anterior Communicating- Most common site of aneurysm
MCA- supplies laters aspect of brain (trunk, upper extremity motor and sensory, Broca and Wernicke)
PCA- supplie occipital lobe
Post. Communicating- also common site or aneurysm (CN iii palsy)
What are the Meningeal Arteries?
What do they supply?
Supply the intracranial dura matter.
Ant. Meningeal- from ethmoidal arteries: supply ant. cranial fossa.
Middle Meningeal- Branches from maxillary: results in EPIDURAL HEMATOMA
Post. Meningeal- supplies post. cranial fossa.
Pathway or venous drainage of the brain?
Veins–> Dural Sinuses–> internal jugular veins
Superior cerebral vein–> sup. sagittal sinus
Superficial Middle cerebral vein- cavernous sinus
Deep Middle Cerebral vein- straight sinus
What veins drain: Midbrain? Pons? Medulla Oblongata? Cerebellum?
Midbrain- basal or great cerebral
Pons-Basal vein, cerebellar veins
Medulla- spinal veins, and neighboring venous sinuses
Cerebellum- Great cerebral vein, adjacent venous sinuses
Where do the vertebral arteries arise from?
What are the main branches?
Arise from the subclavian artery and ascent through the transverse foramina.
Anterior Spinal Artery, Posterior Inferior Cerebellar Artery,
Posterior Spinal Artery- (arises from the PICA in most cases)
What forms the anterior spinal artery?
What does it supply?
It is formed by the union of two arteries from the vertebral artery.
Descends the anterior surface of the spinal cord and supplies the anterior 2/3s of the spinal cord
What forms the posterior spinal arteries?
What does it supply?
Arises directly from vertebral arteries or PICA.
descends near the posterior nerve roots. posterior 1/3 of the spinal cord.
Where do spinal veins drain?
Internal vertebral venous pleus
What is Cerebral Ischemia?
There is insufficient blood flow to the brain to meet metabolic demand.
irreversible damage begins after 5 min
What is an Ischemic Stroke?
Acute blockage of vessels–> disruption of flow and subsequent ischemia–> liquefactive necrosis.
What is a transient ischemic attack?
Brief reversible episode of focal neurologic dysfunction without and acute infarction. <15min
Where is the most common site for cerebral aneurysms? Why?
Most commonly occur at the site where two arteries join because there is a deficiency in tunica media.
May suddenly rupture into the subarachnoid space.
What are the meninges?
What are the divisions?
Three protective, connective tissue coverings that encircle the spinal cord and brain.
Dura, Arachnoid, and Pia Mater
Describe the Dura Mater
Outermost layer. Tough white dense connective tissue with many blood vessels and nerves.
Cranial= periosteal and meningeal layers
(layers separate to enclose the dural venous sinuses)
Describe the Arachnoid Mater
Thin, web like membrane. Lacks vessels.
Does not go into grooves.
Describe the Pia Mater
Thin, many nerves and blood vessels.
Follows the contours of the brain.
What is the main function of the rural venous sinuses?
Where are they situated?
Is to receive blood from the brain through the cerebral veins and the CSF from the subarachnoid space through the arachnoid villi.
Situated between the layers of the dura matter.
Where do the Dural venous sinuses drain?
Internal jugular veins in the neck
Describe the histology go the dural sinuses.
Describe their connections
Lined by endothelium and their walls are thick. No muscular tissue or valves.
Emissary veins connect the sinuses with diploid veins of the skull and scalp
What is the spinal epidural space? What does it contain?
It is the space between the spinal dura mater and the vertebral periosteum.
Contains loose areolar tissue, venous plexus and lymphatics.
Anesthetic-paravertebral nerve block
What is the cranial epidural space? What does it contain?
Its POTENTIAL space between the dura mater and the bones of the cranial vault
contains meningeal arteries and veins.
What is the Subdural Space?
What does it contain?
It is a POTENTIAl space between the dura and arachnoid.
Intracranially is contains veins that connect to the superior sagittal. (Bridging veins)
What is the subarachnoid space? What does it contain?
Located between the Pia mater and the arachnoid.
Contains CSF.
What are the 4 types of intracranial hemorrhages?
- epidural (EDH) - A (MMA)
- subdural (SDH) - V
- subarachnoid (SAH) - A
- intracranial/ intraparenchymal (ICH)
What is an Epidural Hematoma?
Arterial injury of what is most likely responsible for a EDH?
Bleeding into the space between the dura and the the skull.
Occurs more in adolescents and young adults. most common cause is injury. Associated with fracture
MIDDLE MENINGEAL ARTERY. may also be caused by injury to anterior meningeal artery, or venous sinus.
What are clinical presentations of a epidural hematoma?
Variable depending on severity.
transient loss of consciousness in mild cases to coma in server trauma.
LUCID INTERVAL= temp improvement and then deterioration.
headache, nausea, vomiting, lethargy, concussion, aphasia, hemiparesis and seizures.
What are the Radiological findings of a epidural hematoma?
LENS-SHAPED APPERANCE
Does not cross cranial suture lines.
What is an Subdural Hematoma?
Radiological findings?
Bleeding into the space between the dura mater and the arachnoid. Common cause- tearing of the bridging veins.
Crescent shape. ACUTE- hyper-dense (bright) CHRONIC- Hypo-dense (dimmer)
What are the symptoms of chronic subdural hematoma?
-Elderly patients
-Minimal or no trauma history
-Oozing slowly (weeks or months)
-Vague symptoms (headache impairment and unsteady gait)
Brain shrinks and pulls bridging veins away
What are the symptoms of acute subdural bleed?
-Immediately after injury
-Associated with traumatic subarachnoid hemorrhage and contusion.
Worse prognosis.
What is a Subarachnoid hemorrhage?
Radiological appearance?
Bleeding in the CSF filled space between the arachnoid and Pia.
Two kinds: Spontaneous and Traumatic
On CT dense areas of the blood in the subarachnoid space down into the sulci. and Blood in LUMBAR PUNCTURE
What are the symptoms and cause of a spontaneous subarachnoid bleed?
“WORST HEADACHE OF MY LIFE”
-Catastrophic headache
Results from artery aneurysm.
What are the symptoms and cause of a traumatic subarachnoid bleed?
- cerebral contusions
- sever headache
- traumatic injury
What is an intracerebral (ICH) bleed?
Bleeding within the Brain parenchyma.
Traumatic or Non-traumatic (HPB, vascular malformations, infection, vasculitis etc.)
What are clinical features of ICH?
- headache
- one sided weakness
- vomiting
- seizures
- decreased level of consciousness
- neck stiffness
What is the most common cause of non traumatic intracerebral hemorrhage?
Hypertension causes rupture of thin walled lenticular striate artery (MCA).
These will have will have atherosclerosis and mini strokes that add up.
What level is a spinal epidural preformed?
L4/L5
What is the ventricular system?
It is four cavities present in the brain. Two lateral, the third and fourth ventricles.
What is the Choroid Plexus?
What is its function?
There layers of membranes:
- An endothelial layer of the choroidal capillary wall with has fenestrations.
- pia membrane
- Layer of choroidal epithelial cells that contain numerous mito. and microvilli
Function: produce CSF
What is CSF?
What are the volume of CSF?
A clear colorless liquid composed primarily of water
Normal rate of production is 500ml/ day for a total volume of 90-140ml.
Productions IS NOT pressure regulated.
What is the Function of CSF?
- Cushions and protects
- Buoyancy and support
- Nourishes
- Removes Metabolites
- Pathway for Pineal secretions
How is CSF formed?
Ependymal Cells in the choroid plexuses lining the ventricles produce CSF.
Involves filtration of blood and carbonic anhydrase and many transport enzymes for ions in and out.
What is the circulation of CSF?
Lateral ventricles-Foramen of Monro- 3rd ventricle- Aqueduct- 4th ventricle -lateral (luschka) and median (magendie) foramen- subarachnoid- venous sinuses- heart and lungs- choroid plexuses- ventricles
What is the blood brain barrier? What constitutes it?
Endothelial cells linked by tight junctions. Control the passage of substances by active transport. prevent proteins, water soluble substance, protein bounds substance to enter into brain. Permeable to lipid soluble.
What are circumventricular organs?
regions where blood brain barrier is interrupted to allow chemical communication.
- vascular organ
- Subfornical
- Neurohypophysis (posterios pituitary)
- Median Eminence
- Subcommissural
- Pineal Gland
- Area Postrema
What is the Monro-Kellie Hypothesis?
Pressure volume relationship that aims to keep dynamic equilibrium between the 3 non compressible components: brain tissue, blood and CSF.
What happens when there is a disruption of the equilibrium of the non compressible components?
Auto-regulation of cerebral vessel caliber can compensate for modest reductions in cerebral profusion pressure.
large ^ pressure beyond auto-regulation capacity = decrease blood flow and brain ischemia
What are signs of increased intracranial Pressure?
- Headache
- Altered Mental Status
- Nausea and Vomiting
- Papilledema
- Visual loss
- Diplopia
- Cushing’s Triad: HBP, bradycardia and irregular respirations
What is a lumbar puncture? What are normal pressure levels?
Collections of CSF from the spinal subarachnoid space.
Between L4 and L5
Normal pressure
Adults: 90-180 mmH2O (8-15mmHg)
Children: 10-100 mmH2O
What is Hydrocephalus?
What are the 4 types?
Dilation of the cerebral ventricles caused by xs CSF, obstruction of flow , decreased reabsorption.
- Non Communicating- obstruction ventricles (aqueduct)
- Communicating Hydrocephalus- blockage of the subarachnoid space.
- Normal Pressure- communicating in adults.
- Hydrocephalus ed vacuo- Brain tissue diminish due to injury
Clinical features of Normal Pressure Hydrocephalus?
WWW- Wacky, Wobbly and wet.
Dementia, Ataxic gait and urinary incontinence.
What is meningitis?
Inflammation of the meninges that may be caused infections or non infections agents. Diagnosis CSF culture. -elevated WBC -decreased glucose concentration -increased protein concentration - increase pressure
What are the 4 types of Meningitis?
- Acute Purulent- bacterial. headache fever and neck rigidity
- Acute Aseptic- viral. depressed consciousness
- Mycobacterial meningoencephalitis
- Fingal meningoencephalitis
CSF diagnosis in Subarachnoid Hemorrhage
bloody, red blood cells present in cell count. Normal glucose
CSF diagnosis in Bacterial Meningitis
REDUCED GLUCOSE. cloudy appliance elevated protein
CSF diagnosis in Viral Encephalitis
Cloudy or clear. 25-500 lymphocytes. normal glucose.
a brain tumor, which had produced a noncommunicating hydrocephalus. What is the most likely location of the tumor?
the interventricular foramen, connecting the lateral with the third ventricle. A block of the interventricular foramen would lead to enlargement of the lateral ventricle.
