Space Occupying Lesions and Head Trauma Flashcards
There is not a lot of spare room in the skull. Describe what happens if there is development of a space occupying lesion?
The base of skull foraminae do not readily allow ‘escape’ of contents to make up for this increased volume. This can lead to a steady increase in ICP until the body can no longer compensate for this which results in an exponential increase in ICP which can lead to brain herniation.
Name the 5 layers of the skull from external to internal?
Skin, connective tissue, aponeurosis, loose connective tissue, pericranium
What does the connective tissue layer of the skull contain?
Arteries of the scalp
What is the tendinous layer of the skull?
Aponeurosis
The scalp arteries arise from which vessels?
External carotid arteries
The ophthalmic arteries arise from which vessels?
Internal carotid arteries
Describe where the scalp arteries are found and what the significance of this is?
They form an anastamotic network just deep to the skin - means that scalp lacerations and incisions will bleed excessively
What type of joints are the sutures of the skull? What is the function of these?
Fibrous joints, prevent skull fractures from spreading
What is the pterion?
An H shaped suture which forms the thinnest part of the skull
The connections of which bones of the skull form the pterion?
Frontal, sphenoid, temporal, parietal
The mastoid and styloid processes are both features of which bone of the skull?
Temporal bones
Where is the middle meningeal artery found?
Coursing over the deep aspect of the pterion
What is the function of the meninges?
To form a protective covering around the brain and spinal cord
Stretching of which structure causes the pain in meningitis?
Dura mater
The dura mater is a tough, fibrous layer of meninge which receives a sensory supply from where?
CNV
The dura mater is actually composed of 2 layers - describe these? What structure does this allow the formation of?
Superficial layer (periosteal) and deep layer (meningeal) allow the formation of the dural venous sinuses
What is found in the subarachnoid space?
Circulating CSF
How is CSF in the subarachnoid space reabsorbed back into the venous circulation? Where is it reabsorbed back into?
Via arachnoid granulations which are strands of arachnoid mater projecting into the subarachnoid space / dural venous sinuses
What is the pia mater adherent to?
The brain, and all blood vessels and nerves entering/leaving the brain
Where is the dura mater adherent to?
The internal aspects of all bones of the skull
What is the diaphragm sellae?
A tough sheet of dura mater forming a roof over the pituitary fossa
What is the tentorium cerebelli?
A tough sheet of dura mater over the cerebellum
Where does the tentorium cerebelli attach to?
The ridges of the petrous part of the temporal bone
The tentorium cerebelli has a central gap to allow what structure to pass through?
The brainstem
What is the falx cerebri?
A midline structure made of dura mater which separates the left and right cerebral hemispheres
The falx cerebri is attached to the deep aspect of the skull - describe which structures specifically?
It begins by attaching to the crista galli of the ethmoid bone anteriorly and then runs along the deep aspect of the sagittal suture until it attaches to the internal occipital protuberance posteriorly
In what plane do each of the following structures sit a) falx cerebri? b) tentorium cereblli?
a) Sagittal b) Axial
If there is infection in the danger triangle of the face, what is the risk of this?
That infection will spread into the facial veins which can then lead back to the ophthalmic veins and to the cavernous sinus
What are the cavernous sinuses? Where are they found?
They are plexuses of dural venous sinuses - lateral to the body of the sphenoid bone on right and left sides
Superior and inferior sagittal sinuses will drain to where?
The confluence of sinuses
What is the role of the cerebral veins?
To drain venous blood from the brain into the dural venous sinuses
What structure forms after the confluence of sinuses? Where does this drain into?
The sigmoid sinus - drains into the internal jugular vein at the jugular foramen
Where is the confluence of sinuses found?
In the midline, at the internal occipital protuberance
The right common carotid artery is a branch of what? The left common carotid artery is a branch of what?
Brachiocephalic trunk / arch of aorta
The vertebral arteries are branches of which vessels?
Subclavian arteries
Where does the external carotid artery supply?
Structures of the neck, face and scalp (external to the cranial cavity)
The internal carotid artery enters the cranial cavity via what structure? What does it supply?
The carotid canal / supplies parts of the brain
How do vertebral arteries reach the cranial cavity?
They travel up the transverse foraminae within cervical vertebrae and then pass through the foramen magnum to enter the cranial cavity
Which arteries are responsible for supplying the medial aspect of the cerebral hemispheres?
The anterior cerebral arteries
Which arteries are responsible for supplying the lateral aspect of the cerebral hemispheres?
The middle cerebral arteries
Which arteries are responsible for supplying the posterior aspect of the cerebral hemispheres, including the visual cortices?
The posterior cerebral arteries
What are the two main branches of the internal carotid artery?
Middle and anterior cerebral arteries
The two vertebral arteries merge to form what structure? This then divides to form which other structures?
Basilar artery / posterior cerebral arteries
Which arteries are responsible for joining the anterior and posterior circulations of the brain?
Posterior communicating arteries
The arterial network of the brain is found inferior to which structure? Closely related to which other structures? Within where?
Midbrain / pituitary stalk and optic chiasm / subarachnoid space
Where is the subarachnoid space found? It completely surrounds which structures?
Between the arachnoid and pia mater / brain and spinal cord
Where is the CSF produced? How much is produced per day?
The choroid plexuses of the lateral and 3rd ventricles in the brain / 400-500mls
The subarachnoid space can be accessed via what procedure?
Lumbar puncture
At which spinal cord levels can a lumbar puncture be done?
L3/4 or L4/5
Where does the subarachnoid space end?
S2
Where is the 3rd ventricle found?
In the midline within the diencephalon
Where are the right and left lateral ventricles found?
In the right and left cerebral hemispheres
What structure connects the 3rd and 4th ventricles?
Cerebral aquaduct
The 4th ventricle is found between which two structures?
The cerebellum and pons
What structure is continuous with the 4th ventricle?
The central canal of the spinal cord
What structures connect the right and left lateral ventricles with the 3rd ventricles?
Right and left foraminae of Munro
From the 4th ventricle, most CSF passes into where? The minority passes into where?
Subarachnoid space / central canal
What is hydrocephalus?
An increased CSF volume due to excess production, obstruction to flow or impaired reabsorption of CSF
The middle meningeal artery is found between which two structures?
Bone and dura mater
An extradural haemorrhage is a bleed found where? It is caused due to rupture of which vessel? Trauma to where would cause this?
Between the skull bones and the dura mater / middle meningeal artery / pterion
What happens with regards to the meninges in a subdural haemorrhage?
The dura mater gets separated from the arachnoid mater
Subdural haemorrhage is caused by the tearing of which vessels?
Bridging cerebral veins
Subdural haemorrhages are mostly seen in who?
Falls in the elderly and those with a drinking problem
A subarachnoid haemorrhage results in bleeding into where?
The CSF of the subarachnoid space
What is usually the cause for a subarachnoid haemorrhage?
The rupture of an artery in the circle of willis, usually caused by an aneurysm
Which spinal layers does a needle pass through for an epidural anaesthetic?
Supraspinous ligaments, interspinous ligaments, ligamentum flavum, epidural space
Which spinal layers does a needle pass through for an LP?
Supraspinous ligaments, interspinous ligaments, ligamentum flavum, epidural space, dura mater, arachnoid mater, subarachnoid space
Damage to the extradural venous plexus during an epidural anaesthetic or lumbar puncture can have what effect?
Can cause an epidural haematoma which can compress the spinal cord or cauda equina
Where does the spinal cord end?
L2
The cauda equina consists of what?
All the L2 - Co spinal nerve roots
Describe what happens in an uncal herniation?
The uncus (medial part) of the temporal lobe herniates inferior to the tentorium cerebelli
Describe what happens in a tonsillar herniation?
The cerebellar tonsils herniate into the foramen magnum
What nerve can be compressed by an uncal herniation? What symptoms can this cause?
CNIII - ipsilateral fixed dilated pupil (blown)
