L2 - HARC: Vasculature of the CNS Flashcards
Describe and differentiate between the cerebral, cerebellar and brainstem arterial supply and trace their origin and anastomosis. Describe cerebrospinal fluid circulation and abnormalities that may interrupt the flow of CSF. Define and describe the dural venous sinuses and their venous flow pattern. Describe how a haemorrhage or blockage could disrupt the flow of arterial, venous or CSF flow and the resulting implications.
What are the 3 main arteries supplying the head and neck?
Common Carotid
- External CC
- Internal CC
Subclavian
- Vertebral
Where does bifurcation of CC artery occur?
C4
What are the meninges of the brain?
3 layers of protective tissue covering brain:
- dura mater
- arachnoid mater
- pia mater
What does the ECa commonly supply?
Predominantly extra-cranial structures
Exception: supplies meninges intracranially via the middle meningeal artery
What 2 systems are joined together by the Cerebral arterial circle (of Willis)?
- Carotid (anterior) system
2. Vertebrobasilar (posterior)
What makes up the anterior carotid system?
Right Internal carotid artery
Left ICa
What makes up the posterior vertebrobasilar system?
Vertebral arteries joining to become basilar artery.
run in transverse foramina of first 6 vertebrate
Define anastomosis?
connection between two normally divergent structures
Where does the ICa enter skull?
Enters via carotid canal
Passes over the foramen lacerum
What is the foramen lacerum?
hole in base of skull. filled with connective tissue and meningeal branches from ascending pharyngeal artery and emmisary veins from cavernous sinus to pterygoid venous plexus.
What is the carotid siphon?
curve in cavernous segment. portion of artery is surrounded by filaments of the sympathetic trunk. Lateral side - abducent CN VI
What is the origin of the vertebrobasilar system?
First part of subclavian artery
How does the vertebrobasilar system enter the skull?
Foramen magnum.
forms the basilar artery on anterior surface of brain stem, lying on top of clivus of the cranial base
What arteries make up the cerebral arterial supply?
Anterior cerebral artery
Posterior (PCa)
Middle (MCa)
Describe passage of Anterior cerebral artery
forward, medially under corpus callosum.
then superiorly and posterioly along superior surface of corpus callosum?
What is the corpus callosum?
thick nerve tract consisting of a flat bundle of commissural fibers, beneath cerebral cortex in brain.
What areas does the anterior cerebral artery supply?
Frontal lobes.
Medial aspect of parietal lobes
Optic chiasm
Lower limb motor and sensory cortexes.
Describe passage of Posterior cerebral artery?
PCa terminal branch of basilar artery.
Passes posterioly otw supplying parietal lobe.
Supplies occiptal lobe - visual cortex
Describe the passage of the middle cerebral artery?
Passes laterally towards temporal lobe up to lateral aspects of cerebrum.
Initially travels through lateral fissure.
What areas and lobes does the middle cerebral artery supply?
Temporal, parietal and occipital lobes.
Broca’s area- speech
Wernicke’s - language comprehension
Head and neck areas of motor and sensory cortexes.
Give examples of branches of the CoW which supply internal substance of the brain?
Lenticulostriate arteries
Medial striate
chorodial
Describe the lenticulostriate arteries?
from MCA.
Lateral striate arteries.
Describe the Medial striate arteries?
from Anterior cerebral artery.
reccurent artery of Heubner
Describe the chorodial arteries?
Ant. (MCa) - first branch
Post. (PCa) - first group rather than singular arteries
What do the lenticulostriate arteries supply?
Basal ganglia
Thalamus
Internal capsule
Why are lenticulostriate arteries associated with stroke?
LCS.a : small, penetrating BV supplying blood to most sub cortical structures.
Occlusions in these are reffered to as lacunar strokes.
Causes motor and sensory disruption.
What are examples of cerebellar arteries?
Superior cerebellar artery
Anterior Inferior cerebellar artery.
Posterior Inferior cerebellar artery.
Infarct definition?
small localised area of dead tissue resulting from failure of blood supply.
Infarction of Superior cerebellar artery may affect what structures?
Superior cerebellum
Posterolateral midbrain
Infarction in AICa may affect what structures?
Anteriorinferior cerebellum
Posterolateral pons
Inner ear
Infarction in PICa may affect which structures?
Posteroinferior cerebellum
Neurological defects that could arise due to infarction in SCa?
SCa - ataxia (gait), dysarthria (difficult articulation of speech otherwise linguistically OK), nystagmus (vol, invol eye movement), nausea, vomming, headache and vertigo
Neurological defects that could arise due to infarction in AICa?
vertigo, nausea, intolerance of head motion.
Horner’s syndrome: constriction of pupil (miosis), drooping of upper eyelid (ptosis) and anhidrosis (no face sweating)
unilateral hearing loss
ipsilateral facial paralysis.
Neurological defects that could arise due to infarction in PICa?
Headache
What bones make up the Pterion?
Pterion:
- Temporal
- Sphenoid
- Frontal
- Parietal
Where does the middle meningeal a. enter the skull?
Foramen spinosum.
Largest meningeal a.
Briefly, how are ventricles formed?
Ventricles: spaces in brain, filled with CSF
Central canal of neural tube dilates to form ventricles
Choroid plexus – CSF
- lateral, 3rd & 4th ventricles
Describe the pathway of CSF flow?
Lateral ventricle - Interventricular foramina Third Ventricle - cerebral aqueduct Fourth Ventricle - lateral and median apertures Subarachnoid space Arachnoid villi of dural venous sinuses - Venous blood Heart and lungs - arterial blood back to 3rd, 4th and lateral
What are the internal veins involved in head and neck venous drainage?
Cavernous sinus facial vein superior sagittal sinus inferior sagittal sinus confluence of sinuses
what are the external veins involved in head and neck venous drainage?
Angular vein
Retromandibular vein
Where do all veins involved in head and neck drain into?
Internal jugular vein
What two layers form dural venous sinuses?
- Periosteal layer - superficial and attached to the skull
- Meningeal - deep and projecting through cranial cavity
Spaces created between the two layers collect venous blood from the brain aka ‘dural venous sinuses’
Describe the cavernous sinus?
One of the dural venous sinuses of the head.
Network of veins that sit in a cavity.
approx 1 x 2cm
What passed through the cavernous sinus?
Carotid siphon of ICa.
CN III, IV, V (v1 & v2)
Describe an Epidural Haemorrhage?
Collection of blood between inner skull surface and outer dura (endosteal layer).
Source of bleeding is most commonly a torn middle meningeal artery.
Describe the look of an epidural haemorrhage?
Biconvex shape.
Can cause mass effect with herniation.
Don’t cross sutures as periosteum crosses through the suture continuous with other periosteal layer.
Middle meningeal artery is a branch of the….
maxillary artery from external carotid artery.
Describe a subdural haematoma?
Bleeding occurs between dura and arachnoid. Bleeding is under skull and outside brain.
Pressure on brain increases as blood accumulates.
Describe a subarachnoid haemorrhage?
Bleeding into subarachnoid space.
Area between arachnoid membrane and pia mater surrounding brain.
Look out for star like shape in CT.
What is hydrocephalus?
Accumulation of cerebrospinal fluid within brain.
