Clinically relevant anatomy of intracranial space occupying lesions & head trauma Flashcards
What are the layers of the scalp?
S- skin C- connective tissue A- aponeurosis L- loose connective tissue P- pericranium
What is contained within the connective tissue layer of the scalp?
The named arteries of the scalp
Describe the blood supply to the scalp
The common carotid artery branches into the internal and external carotid artery. Internal carotid artery –> right ophthalmic artery. External carotid -> scalp branches
What is the protuberance of the skull?
External occipital protruberance
What are the processes of the skull
Mastoid and styloid processes
What is the pterion?
Thinnest part of the skull - H shaped Joins frontal, parietal, temporal and sphenoid bone
Which artery courses deep to the pterion?
Middle meningeal artery
What are meninges?
Protective converings for the brain and spinal cord
What are the three layers of the meninges?
Dura mater
Arachnoid mater
Pia mater
Describe dura mater
Tough/fibrous
Has a sensory nerve suppy from CN V
Encloses the dural venous sinuses
Describe the arachnoid mater
Spidery mother
Arachnoid granulations (reabsorb CSF)
What is contained in the subarachnoid space?
CSF
Describe pia mater
Adherent to the brain and the blood vessels and nerves entering or leaving brain
What is tentorium cerebelli
Sheet of dura mater ‘tenting’ over the cerebellum
Attaches to the ridges of the petrous temporal bones
Has a central gap to permit the brainstem to pass through
What is the diaphragm sellae
Tough sheet of dura mater forming a roof (diaphragm) over pituitary fossa
What is the falx cerebri?
Midline structure
Made of dura mater
Attaches to deep aspect of skull
Separates right and left cerebral hemispheres
What aspect of the skull does falx cerebri attach to anteriorly?
Crista galli of the ethmoid bone
What aspect of the skull does the falx cerebri attach to medially?
Sagittal suture
What aspect of the skull does the falx cerebri attach to posteriorly?
Occipital protruberance
Describe the drainage of the brain
Which arteries supply the brain?
vertebral artery
internal carotid
Describe the arteries in the circle of willis and what they supply
What is the volume of circulating CSF?
400-500mls
Where is CSF produced?
Choroid plexus of the ventricles
Where is CSF reabsorbed?
Dural venous sinuses via arachnoid granulations
Where does the subarachnoid space end?
S2 part of spine
where can CSF be accessed?
lumbar puncture at L3/L4 or L4/L5 IV disc levels to obtain a sample
Describe the circulation of CSF?
- secreted by choroid plexus in lateral and third ventricle
- moves from left to right ventricles via foraminae of monroe
- moves to the 3rd ventricle (midline)
- then into the cerebral aqueduct
- then into the 4th ventricle
- then into the subarachnoid space or into the central canal
- reabsorbed from subarachnoid space via arachnoid granulations
- then into the dural venous sinuses
What is hydrocephalus?
Excessive production, obstruction to flow or inadqeuate reabsorption of CSF leading to increased CSF volume
Describe a ventricular peritoneal shunt
Shunt catheter is tunelled beneath the skino f the nect and chest then sited within peritoneal cavity
Where does the circle of wilis lie?
Within the subarachnoid space
What are the three kinds of bleeds within the cranial cavity?
Extradural haemorrhage
Subdural haemorrhage
Subarachnoid haemorrhage
Describe an extradural haemorrhage
- between the bone & the dura
- ruptured middle meningeal artery
- trauma to the pterion
Describe a subdural haemorrhage
- separates the dura from the arachnoid
- torn cerebral veins
- falls in the elderly
Describe a subarachnoid haemorrhage?
- into the CSFof the subarachnoid space
- ruptured Circle of Willis (“berry”) aneurysm
- congenital aneurysm
What are the kinds of supratentorial herniations
cingulate (subfalcine)
Central (trans-tentorial)
Uncal
Transcalvarial
What are the kinds of infratentorial herniations?
Upward cerebellar/transtentorial
Downward cerebellar (tonsilar
Which type of herniation leads to a blown pupil?
Compression of the oculomotor enrve by an uncal herniation leads to an ipsilateral fixed dilated pupil
