Intracranial Space Occupying Lesions and Head Trauma Flashcards
What are space occupying lesions?
Abnormal tissue taking up space.
Increased ICP may result in contents doing what?
Herniating.
What are the 5 layers of the scalp?
S - skin. C - connective tissue. A - aponeurosis. L - loose connective tissue. P - pericranium.
The scalp arteries form what?
A rich anastomotic network just deep to the skin.
As the scalp arteries form a rich anastomotic network, scalp lacerations and incisions are prone to what?
Bleeding excessively.
The right ophthalmic artery is a branch of what?
Right internal carotid artery.
What is the function of sutures (fibrous joints) of the skull?
Help to prevent skull fractures from spreading and thus minimise propagation.
Describe the pterion.
- H-shaped.
- Made up of frontal, parietal, temporal and sphenoid bones.
- Thinnest part of skull.
Describe the relationship between the middle meningeal artery and the pterion.
The middle meningeal artery courses over the deep aspect of the pterion.
The groove across the deep surface of the pterion is made by what?
The R/L middle meningeal artery.
The groove between the deep surfaces of the temporal and occipital bones are made by what?
The R/L sigmoid sinus.
What is meningitis?
Usually a bacterial or viral infection of the meninges.
What are the meninges?
Protective coverings for the brain and spinal cord.
The brain and spinal cord are surrounded by how many layers of membrane?
Three.
Name the three layers of membrane surrounding the brain and spinal cord.
- Dura mater.
- Arachnoid mater.
- Pia mater.
Describe dura mater.
“hard mother”.
- Tough/fibrous layer receiving sensory supply from mainly CN V.
- Encloses the dural venous sinuses.
Where are the dural venous sinuses enclosed?
Within the dura mater.
What does the arachnoid mater contain and what are their functions?
Arachnoid granulations that contain the circulating CSF.
Describe pia mater.
Adherent to the brain, the blood vessels and nerves entering/exiting the brain.
What is responsible for pain in meningitis?
Stretching of dura mater.
Dura mater is adherent to what?
Internal aspect of all bones of the skull.
What is diaphragm sellae?
A tough sheet of dura mater forming a roof over the pituitary fossa.
What is tentorium cerebelli?
Tough sheet of dura mater “tenting” over the cerebellum, attaching to the ridge of the petrous temporal bones with a central gap to permit the brainstem to exit.
What is falx cerebri?
Midline structure made of dura mater attaching to the deep aspect of the skull and separating the right and left cerebral hemispheres.
What does falx cerebri attach to anteriorly?
Crista galli of the ethmoid bone.
What does falx cerebri attach to posteriorly?
Internal occipital protruberance of the occipital bone.
Falx cerebri separates what?
The right and left cerebral hemispheres.
Cerebral veins drain venous blood from the brain into what?
Dural venous sinuses.
The left sigmoid sinus drains into what at the jugular foramen?
The left internal jugular vein.
Where is the confluence of the dural venous sinuses?
In the midline at the internal occipital protuberance deep to the external occipital protruberance.
What is the danger triangle?
Area of potential for venous spread of infection from superficial to deep.
Describe the path of the vertebral arteries to enter the cranial cavity.
Pass through transverse foraminae of cervical vertebrae then through foramen magnum to enter the cranial cavity.
The right internal carotid artery becomes internal to the cranial cavity via what?
The carotid canal.
The external carotid arteries remain external to the cranial cavity to supply what?
The neck, face and scalp.
In the Circle of Willis, the right anterior cerebral artery supplies what?
The medial aspect of the right cerebral hemisphere.
In the Circle of Willis, the right posterior cerebral artery supplies what?
The posterior aspect of the right cerebral hemisphere including the visual cortex.
In the Circle of Willis, the left middle cerebral artery supplies what?
The lateral aspect of the left cerebral hemisphere.
Describe the location of the Circle of Willis.
Inferior to the midbrain, closely related to the pituitary stalk and the optic chiasm within the subarachnoid space.
Where is the subarachnoid space located?
Between arachnoid mater and pia mater.
Describe the subarachnoid space.
A continuous space between arachnoid and pia mater completely surrounding both the brain and spinal cord to cushion and protect them.
What is contained within the subarachnoid space.
CSF.
Where is CSF produced?
In the choroid plexus of the ventricles of the brain.
Where is CSF reabsorbed?
Into the dural venous sinuses via the arachnoid granulations.
Where and how might the subarachnoid space be accessed?
Lumbar puncture at L3/4/5.
Where does the subarachnoid space end?
Inferiorly at the level of the S2 part of the sacrum.
What ventricle of the brain is found in the midline within the diencephalon?
3rd ventricle.
The cerebral aqueduct connects what?
The third and fourth ventricles in the midline.
What ventricle is found between the cerebellum and pons?
The 4th ventricle.
The central canal of the spinal cord is continuous with what ventricle?
The 4th ventricle.
CSF is secreted by what?
The choroid plexus.
CSF is circulated from the R&L lateral ventricles via what into the 3rd ventricle?
Right and left foraminae of monro.
CSF exits the 3rd ventricle via what into what?
Cerebral aqueduct into the 4th ventricle.
After CSF circulates from the 4th ventricle into the subarachnoid space what happens?
It is then reabsorbed from the subarachnoid space via the arachnoid granulations.
What are arachnoid granulations?
Absorptive “herniations” of arachnoid mater protruding into the dural venous sinuses.
CSF is reabsorbed by arachnoid granulations into what?
Dural venous sinuses.
What is hydrocephalus?
Increased CSF volume due to:
- Excessive CSF production.
- Obstruction of flow.
- Inadequate CSF reabsorption.
How is hydrocephalus treated?
Ventricular peritoneal shunt.
How is a ventricular peritoneal shunt placed?
“Tunnelled” beneath the skin of the neck and chest and then sited within the peritoneal cavity.
Cerebral veins cross the subarachnoid space to drain into where?
The superior sagittal sinus.
Describe an extradural haemorrhage.
Bleeding between the bone and dura due to ruptured middle meningeal artery often due to trauma to pterion.
Describe a subdural haemorrhage.
Bleeding between dura and arachnoid mater due to torn cerebral veins often due to falls (in elderly/those with drinking problems).
Describe a subarachnoid haemorrhage.
Bleeding into the CSF of subarachnoid space due to ruptured Circle of Willis - “Berry” aneurysm or congenital aneurysm.
Damage to the extradural venous plexus can result in what?
Epidural haematoma compressing the spinal cord or cauda equina.
What is the final destination of the epidural catheter?
Epidural space.
What is the final destination of the lumbar puncture?
Subarachnoid space.
Where does the spinal cord end?
L2
What does the cauda equina consist of?
L2-Co spinal nerve roots descending towards their intervertebral foramina.
- Motor roots anteriorly.
- Sensory roots posteriorly.
What types of supratentorial herniation are there?
- Cingulate (subfalcine).
- Central.
- Uncal (uncus -medial part of temporal lobe that herniates inferior to tentorium cerebelli).
- Transcalvarial.
What types of infratentorial herniation are there?
- Upward.
- Downward or tonsillar herniation (herniation of cerebellar tonsils - herniated into foramen magnum).
Compression of the oculomotor nerve by uncal herniation leads to what?
Ipsilateral fixed dilated pupil.
