Clinically Relevant Anatomy of Space Occupying Lesions Flashcards
Monro Kellie hypothesis
- -Cranial compartment is incompressible and volume inside cranium is fixed
- -Cranium and its constituents create a state of volume equilibrium, such that an increase in the volume of one constituent must be compensated for by a decrease in the volume of another
- -The principle buffers to increased volume are CSF and blood volume to a lesser extent
give an example of an acute and subacute expanding intracranial pathology
- acute - bleed
- subacute - tumour
5 layers of scalp - outside to in
- Skin
- Connective tissue
- Aponeurosis
- Loose connective tissue
- Pericranium
aponeurosis layer
tendon layer between frontalis and occipitalis muscles
why do scalp lacerations bleed excessively
scalp arteries form a rich anastomotic network
which layer are the scalp arteries found in
Connective tissue layer
which arteries form the anastomotic network in the scalp
internal and external carotid
what is the pericranium
periosteum enveloping the skull (outer membrane of bone that is responsible for bone formation)
which types of joints are sutures, and what is their purpose
fibrous, to prevent cracks spreading between different skull bones
why is the pterion a disadvantage
- thinnest part of skull (frontal, temporal, parietal and sphenoid)
- directly above middle meningeal artery
which bone is the carotid canal found in,and what goes through it
temporal bone, internal carotid artery
what gives rise to the pain of meningitis
stretching of the dura mater
nerve supply to dura mater
sensory supply from CN V
describe the structure of the dura mater
- 2 layers: outer periosteal and meningeal
- in parts these are close together
- in parts there are dural venous sinuses between them
diaphragm sellae
sheet of dura mater over the pituitary fossa, has a hole to allow the pituitary stalk through
tentorium cerebelli
dura mater sheet over the cerebellum, separating cerebral hemispheres from cerebellum
where does the tentorium cerebelli attach
to the ridges of the petrous temporal bones
falx cerebri
- midline dura mater sheet
- separates the right and left cerebral hemispheres
attachments of the falx cerebri
- crista galli of ethmoid bone anteriorly
- internal aspect of sagittal suture
- internal occipital protuberance posteriorly
internal occipital protuberance
external occipital protuberance
outline the venous drainage of the brain
- cerebral veins drain venous blood from the brain into dural venous sinuses
- dural venous sinuses drain into internal jugular vein at jugular foramen
which dural venous sinus drains into the IJV
sigmoid sinus
where do the dural venous sinuses confluence
at the internal occipital protuberance
why are facial veins atypical
- they have thicker walls so wont collapse and have no valves
- this means bacteria could travel up them to the ophthalmic veins and towards cavernous sinus
cavernous sinus contents
CNIII, IV, V1, V2, VI and internal carotid artery
also, left CCA and subclavian artery
which artery supplies the lateral aspect of the cerebral hemisphere
left and right middle cerebral artery
which artery supplies the medial aspect of the right and left cerebral hemisphere
R and L anterior cerebral artery
where is the visual cortex located in the brain
posterior aspect
which artery supplies the posterior aspect of R and L cerebral hemispheres (including visual cortex)
posterior cerebral artery
?? are ophthalmic arteries
where is the circle of Willis located in the skull
subarachnoid space
outline CSF flow through ventricles of the brain
CSF formed in the choroid plexuses of each lateral ventricle flows into the 3rd ventricle, where more CSF is added by the choroid plexus here. It flows through the cerebral aqueduct of midbrain into the 4th ventricle, where another choroid plexus adds more CSF. The central canal of the spinal cord is continuous with the 4th ventricle.
CSF then enters the subarachnoid space through 3 openings in the roof of the 4th ventricle: (some CSF enters the central canal of teh spinal cord, whichb is continuous withb the 4th ventricle)
- Single medial aperture (Magendie)
- Paired lateral apertures (Luschka
describe the reabsorption of CSF
CSF then returns to venous blood from subarachnoid space by entering dural venous sinuses through arachnoid granules into the superior sagittal sinus. The dural venous sinuses drain into the IJV at the jugular foramen.
management of hydrocephalus
- ventricular peritoneal shunt - sited within the peritoneal cavity
where in the head is the middle meningeal artery located
between the bone and dura (remmeber can be damaged by pterion fracture)
where in the ehad is the circle of willis located
subarachnoid space
where in the mater layers are the cerebral veins located
they cross the subarachnoid space to drain into the dural venous sinuses
what kind of aneursym causes a subarachnoid haemorrhage
circle of Willis eg berry aneurysm, these are often congenital
what typically causes an extradural haemorrhage
- between bone and dura
- eg ruptured middle meningeal artery
- can occur after trauma to the pterion
what typically causes a subdural haemorrhage
- between dura and arachnoid
- eg torn cerebral veins
- occurs after falls in the elderly and those with a drinking problem
why is L3/4 the best space for a lumbar puncture
- the cauda equina is here not the spinal cord (ends at L2) - these roots are less easily damaged than the conus medullaris
- the vertebrae are not fused here (like the sacrum)
what goes through the anterior and posterior sacral foraminae
anterior and posterior rami of sacral spinal nerves
supratentorial herniation: cingulate (subfalcine)
frontal lobe is pushed under the falx cerebri - most common type
supratentorial herniation: central
squeezed through a notch in the tentorium cerebelli
supratentorial herniation: uncal
brain the uncus (medial part) of the temporal lobe herniates inferior to the tentorium cerebelli
supratentorial herniation: transcalvarial
brain squeezes through a fracture/gap in the skull
infratentorial herniation
can be upward or downward (into the foramen magnum)
which nerve can an uncal herniation damage
CNIII - ipsilateral fixed dilated pupil
what do the vertebral arteries branch off
R and L subclavian arteries
what can damage to the epidural venous plexus cause
- epidural haematoma
- can compress the spinal cord and cause cauda equina if large enough
