5.1 Cranium & the brain Flashcards
The cranial sutures are _______ joints (synarthroses) of the bones of the vault or face:
• ___________ are membranous areas in the cranial vault which have not ossified yet, and allow for rapid stretching and deformation of the cranium (for developing brain)
fibrous;
Fontanelles
Where is the coronal suture?
between frontal and parietal bones?
where is the sagittal suture?
between parietal bones?
where is the lambdoid suture?
between parietal and occipital bones
where is the pterion (in temporal fossa?
H-shaped junction between the frontal, parietal, temporal and sphenoid bones
Pterion fractures: the pterion is the weakest part of the skull and is easily fractured
- Direct traumatic blow (to the pterion) or indirect blows to the top or back of the skull may place sufficient force on the skull to fracture the pterion
• ______________ runs immediately deep to the pterion traumatic blows/fractures may rupture the artery (life-threatening significant epidural haematoma).
Anterior division of the middle meningeal artery
What are the 5 layers of the scalp?
Skin Connective tissue Aponeurosis Loose areolar tissue Pericranium
What does the skin of the scalp contain?
Contains sebaceous glands and hair follicles (head hair)
What does the connective tissue of the scalp contain?
Dense subcutaneous layer of fat and fibrous tissue containing the nerves and blood vessels of the scalp
Where does the aponeurosis of the scalp run?
Epicranial aponeurosis (galea aponeurotica) is a layer of dense fibrous tissue running from the frontalis muscle to occipitalis
what is the loose areolar tissue of the scalp made up of?
Made of type I and III collagen bundles and glycosaminoglycans (allows more superficial layers to shift about over the pericranium):
• Danger zone: infections may spread easily via emissary veins into the cranium
Pericranium of the scalp: Periosteum of the skull bones (provides nutrition and capacity for repair to the bones) → continuous with __________ at suture lines
endosteum
Scalp lacerations: deep lace rations to the scalp tend to bleed profusely (due to pull of _______________ preventing closure of vessel and skin, adherence of vessels to dense connective tissue preventing vasoconstriction, numerous anastomoses
- Loss of blood supply to the scalp does not cause bone necrosis (most arterial supply to skull is from the _________________)
occipitofrontalis muscle;
middle meningeal artery
what does the anterior cranial fossa contain?
Frontal lobe of the cerebral hemispheres
What does the middle cranial fossa contain?
Temporal lobes of the cerebral hemispheres
What does the posterior cranial fossa contain?
Cerebellum, pons, medulla oblongata (hindbrain)
[anterior cranial fossa]
perforations in cribiform plate
- bone
- structures
- ethmoid bone
- CN1
[middle cranial fossa]
optic canal
- bone
- structures
- lesser wing of sphenoid
- CNII, opthalmic artery
[middle cranial fossa]
superior orbital fissure
- bone
- structures
- between lesser and greater wings of sphenoid
- CN III, IV, V1 (ophthalmic), VI
- Lacrimal, frontal, nasociliary nerves (V1)
- Superior ophthalmic vein
[middle cranial fossa]
foramen rotundum
- bone
- structures
- greater wing of sphenoid
- CNV2 (maxillary)
[middle cranial fossa]
foramen ovale
- bone
- structures
- greater wing of sphenoid
- CNV3 (mandibular)
[middle cranial fossa]
foramen spinosum
- bone
- structures
- greater wing of sphenoid
- Meningeal branch of CN V3
- Middle meningeal artery
[middle cranial fossa]
carotid canal + foramen lacerum
- bone
- structures
- Between petrous part of temporal and sphenoid
- The foramen lacerum is normally closed in a living person, and the carotid canal is its continuation.
- ICA at the carotid canal
[posterior cranial fossa]
internal acoustic meatus
- bone
- structures
- Petrous temporal
- CN7+8
[posterior cranial fossa]
jugular foramen
- bone
- structures
- Between petrous part of temporal and condylar part of occipital bone
- CN 9. 10. 11
- IJV
[posterior cranial fossa]
hypoglossal canal
- bone
- structures
- occipital bone
- CN12
[posterior cranial fossa]
foramen magnum
- bone
- structures
- occipital bone
- Medulla oblongata
- Spinal part of CN XI
- Right and left vertebral arteries
where is the falx cerebri located?
Sickle-shaped fold; lies in midline between cerebral hemispheres
where is the tentorium cerebelli?
Crescent fold; roofs over the posterior cranial fossa (separates cerebellum from the occipital lobes)
where is falx cerebrelli located?
Small sickle-shaped fold; attached to the internal occipital crest and projects forward between the 2 cerebellar hemispheres
where is a diaphragma sellae?
Small circular fold; roofs over the sella turcica (pituitary fossa)
DURAL VENOUS SINUSES The dural venous sinuses lie between the _________________ mater, and drain the CNS, face, and scalp:
• Drain into the internal jugular veins (IJVs); do not possess valves (unlike other veins)
• Eleven venous sinuses which include the straight, superior, and inferior sagittal sinuses (in ____________), transverse sinus, sigmoid sinus and cavernous sinus:
o Straight sagittal sinus is a continuation of the _________________
periosteal and meningeal layers of dura;
falx cerebri;
great sagittal vein and inferior sagittal sinus
Cerebral venous sinus thrombosis (CVST): presence of thrombus within one of the dural venous sinuses, which occludes venous return and causes accumulation of deoxygenated blood in the brain parenchyma –> venous infarction
- May be complicated by _______________ –> unable to drain through the thrombosed venous sinuses
- Common clinical features headache, nausea and vomiting, neurological deficits
- Treatment: anticoagulant drugs
accumulation of CSF (hydrocephalus)
CSF CIRCULATION
CSF is produced by the _____________ in the lateral, third and fourth ventricles (via filtration of blood and modification of filtrate by reabsorption and secretion):
• Flows from lateral ventricles to 3rd ventricle via __________________
• 3rd and 4th ventricles are connected via the cerebral aqueduct (of Sylvius)
• Flows from 4th ventricle into the subarachnoid space via the lateral apertures (______________) and the median aperture (_______________):
o Foramina of Luschka drain CSF into the ___________________
o Foramen of Magendie drains CSF into the _____________
• Absorption of CSF back into the bloodstream occurs in the superior sagittal sinus via the __________ (push through arachnoid mater)
epithelial cells of the choroid plexus;
interventricular foramen (of Monro);
foramina of Luschka;
foramen of Magendie;
cerebellopontine angle cistern;
cisterna magna;
arachnoid villi
Hydrocephalus: accumulation of CSF within the ___________________, causing increased intracranial pressure and brain herniation/compression (abnormal function)
Head enlargement due to hydrocephalus occurs only in ______________________
- Most common congenital cause is ___________ (other causes include neural tube defects, arachnoid cysts, Arnold Chiari malformation)
- Associated with _________ (meningocele –> Arnold Chiari malformation –> increased cranial CSF production + uncal herniation –> hydrocephalus)
- Management: insertion of cerebral shunt system into the dural venous sinus (lies under the anterior fontanelle ) –> shunt must be changed as the person grows
ventricular system and CSF spaces;
children whose anterior fontanelle (soft spot) has not fused (before 6 months);
aqueductal stenosis;
spina bifida
What does the diencephalon contain?
Consists of the thalamus, hypothalamus, epithalamus (pineal gland) and subthalamus (functionally part of the basal ganglia)
What does the midbrain contain?
Connects the forebrain with the hindbrain (with cerebral aqueduct down the middle); consists of the cerebral peduncles (2 halves), substantia nigra, red nuclei and other important brainstem structures
What does the hindbrain contain?
Consists of the pons, medulla oblongata and cerebellum
What does the ventral midbrain contain?
crus cerebri (peduncles), CN III
What does the dorsal midbrain contain?
superior & inferior colliculi, CN IV
What does the ventral pons contain?
basilar sulcus (and basilar artery), CN V, VI, VII, VIII
What does the posterior pons contain?
superior, middle & inferior cerebellar peduncles, floor of 4th ventricle
What does the ventral medulla contain?
anterior median fissure, anterolateral sulcus, pyramids, olives, CN IX, X, XI, XII
what does the dorsal medulla contain?
posterior median sulcus, posterolateral sulcus, median sulcus, sulcus limitans, hypoglossal trigone, vagal trigone, area postrema, obex
The brain receives its arterial supply from the vertebral arteries (from ___________) and internal carotid arteries (ICA) which are connected in the ____________:
• Meninges are supplied by the anterior, middle, posterior meningeal arteries
• Venous drainage: cerebral veins → dural venous sinuses → internal jugular veins (IJV)
What are the branches of the internal carotid arteries and vertebral arteries? ?
subclavian arteries;
circle of Willis;
ICA: anterior cerebral, anterior communicating, middle cerebral;
vertebral: basilar, posterior cerebral; posterior communicating, anterior inferior cerebellar artery, posterior cerebellary artery, anterior spinal artery
Extradural haemorrhage
- injuries to the _______ (run in the epidural space)
- __________ lesion
- limited by suture lines
- midline shift (less)
- loss of consciousness –> lucid interval –> sudden detoriation (vomiting, restlessness, loss of consciousness)
meningeal arteries;
bioconvex
subdural haemorrhage
- Tearing of ______________ at point of entry to superior sagittal sinus
- __________ lesion
- Not limited by suture lines
- Midline shift
- Gradually increasing headache and confusion (slower onset)
superior cerebral veins (or bridging veins);
Concave (crescent-shaped)
Subarachnoid haemorrhage
- Leakage or rupture of congenital aneurysm on the ____________ (85%)
- Extends into ________ (CSF spaces)
- Not limited by suture lines
- Diagnosed by lumbar puncture (check for ______________)
- Sudden onset of severe headache (____________ headache)
circle of Willis;
sulci;
RBC count and xanthochromia;
thunderclap
The Monro-Kellie doctrine describes the pressure-volume relationship between intracranial pressure (ICP), volume of CSF, blood, brain tissue and cerebral perfusion pressure (CPP):
Vintracranial = __________+_______+________
• A dynamic equilibrium exists between the non-compressible components of the brain within the rigid compartment of the skull
• Increase in volume of one cranial component must be compensated by a decrease in the volume of another (main buffers of increased volumes are _________________)
• Signs & symptoms of increased ICP: headache (typically morning), vomiting (without nausea), ocular palsies, altered consciousness, back pain, papilloedema etc.
o Differ in children as their fontanelles have not fused (bulge out with high ICP)
Vbrain + Vblood + VCSF;
CSF and blood
What is the mechanism of uncal hernia?
Medial temporal lobe (uncus) pushes downward into the posterior cranial fossa through the tentorial incisura
What is the mechanism of central hernia?
Downward displacement of the cerebral hemisphere and basal nuclei (ganglia) through the tentorial notch
What is the mechanism of subfalcine hernia?
Brain tissue extending under the falx in the supratentorial cerebrum
What is the mechanism of tonsillar hernia?
Cerebellar tonsils protruding below the foramen magnum (compresses medulla and upper cervical spinal cord)
