cranium ventricles and meninges Flashcards
layers of meninges from inner to outer
PAD
pia, arachnoid and dura (periosteal and meningeal layers)
the three fossa of the cranial base, and contents
anterior - frontal lobe
middle - temporal lobe
posterior - cerebellum and brainstem
falx cerebri and tentorium cerebelli
both made from dura
the falx cerebri seperates the left and right hemispheres and runs along the interhemispheric fissure
the tentorium cerebelli covers the superior aspect of the cerebellum
supratentorial and infratentorial mean
above (cerebrum) and below (cerebellum) the tentorium cerebelli
potential spaces of the meninges are
epidural
subdural
subarachnoid
the middle meningeal artery is in which meningeal space and branches from which artery
epidural space - a branch of the external carotid artery
the subdural space contains what type of vasculature
bridging veins that drain the cerebral hemispheres and drain into dural venous sinuses, which reach the internal jugular veins by sigmoid sinuses
this space contains the major brain arteries and CSF
subarachnoid space
how is CSF produced
by a choroid plexus structure lining the ventricles of the brain - these are specialised vascular structures lined with ependymal cells
how is CSF reabsorbed
via arachnoid granulations lining the ventricles following circulation of CSF around the subarachnoid space. the CSF is reabsorbed into dural venous sinuses via these granulations.
ventricles of the brain are and CSF travels in what order
lateral ventricles
foramen of monro
third ventricles
cerebral aquaduct
fourth ventricle
lateral formaina or luschka and midline foramina of magendie
remaining subarachnoid space till reabsorption
cisterns are
spaces in the subarachnoid space which have accumulated CSF in large volumes - create areas which permite unobstructed CSF flow
mass effect from intracranial lesions produce
- effacement of flattening of sulci
- neurological deficits, depending on location
- blood vessel occlusion - ischaemic infarction
- blood vessel erosion - haemorrhage
- vasogenic oedema (BBB damage)
- ventricular compression - hydrocephalus
- midline shift
- loss of consciousness by compression of RAS
CEREBRAL PERFUSION =
MEAN ARTERIAL PRESSURE - INTRACRANIAL PRESSURE (if ICP increases CPP decreases)
signs of elevated intracranial pressure are
- headache
- altered mental state, irritability
- nausea, vomiting
- papilloedema
- visual loss
- diplopia - abducens palsy commonly
- cushings triad - brady, hypertension, irregular respirations
herniation is a phenomenon where
structures creating a mass effect push intracranial structures from one compartment to another
three most clinically relevant forms of herniation are
tentorial herniation - herniation through the tentorial notch
central herniation - herniation that is central and downward
subfalcine - herniation under the falx cerebri
tentorial herniation
- medial temporal lobe (uncus)
triad
- blown pupil (CN III compression)
- hemiplegia (cerebral peduncle compression)
- coma
central herniation
downward displacement of the brainstem
tonsilar herniation is where the cerebral tonsils (most inferior portion of cerebellum) herniate through the foramen magnum
subfalcine herniation
where a unilateral mass effect can cause brain tissue to herniate under the falx cerebri - most commonly the cingulate gyrus
epidural heamatoma
caused by middle meningeal artery rupture from temporal bone fracture
lens shaped and biconvex
does not spread past the cranial sutures
initial symptoms not prominent, until intracranial pressure ensures, causing mass effect symptoms and herniation
subdural haematoma
rupture of the bridging veins in subdural space
crescent shaped
chronic (common in elderly b/c brain atrophy and warfarin),
acute (hyperdense to hypodense with time), haematocrit effect with continuous bleeding, poorer prognosis
subarachnoid haemorrhage
characterised by the phrase “worst headache of my life”
commonest cause arterial aneurysm, then AVM
aneurysms can be
- saccular or berry - balloon like outpouchings in arterial branch points
AComm, PComm and MCA
- fusiform - where main vessel becomes dilated and the wall thins out
