Anatomy 4 - Space occupying lesions Flashcards
What is the problem with space occupying lesions and define what a SOL is ?
Space occupying lesions (SOL) = abnormal tissue taking up space in the skull
The problem with SOL’s is that the base of skull foraminae do not readily permit ‘escape’ of contents ==> Acute or sub acute (expanding) intracranial pathologies can result in increased ICP, in turn the increased ICP can result in herniation
What are the 5 layers of the scalp and how do you remember them ?
SCALP:
- Skin
- Connective tissue
- Aponeurosis
- Loose connective tissue
- Pericranium
What does layer 2 of the scalp contain and why is this important ?
Contains the named arteries of the scalp
The scalp arteries form a rich anastomotic network just deep to the skin – scalp lacerations & incisions can bleed excessively
What are the 4 main sutures of the skull and what is their function ?
- Coronal
- Sagittal
- Lamboid
- Squamous - joins the parietal and temporal bones
Function is to stop fractures spreading (they are fibrous joints)
What are the main bones of the skull ?
What are the main bones of the skull (face)
What are the main bones of the base of the skull
Go over some of the features of the skull
What is the pterion and why is it significant ?
It is the thinnest part of the skull formed between the Frontal, parietal, temporal and sphenoid bones
The middle meningeal artery courses deep to it ==> it is at risk to damage
State the following meningeal layers shown
What is the intracranial dura mater mainly innervated by ?
CN V
What is the dura mater adherent to ?
All of the bones of the skull
What is the tentorium cerebelli and the diaphragm sellae ?
Tentorium cereblli = a tough sheet of dura mater ‘tenting’ over the cerebellum
Diaphragm sellae = a tough sheet of dura mater forming a roof over the pituitary fossa
What is the falx cerebelli ?
A midline structure of dura mater splitting the brain into the left and right cerebral hemispheres
Label the venous drainage of the brain
Main veins to remember:
- Superior sagittal sinus
- Cerebral veins
- Left sigmoid sinus
- Opthalamic veins
- Internal jugular vein
- Facial vein
The dural venous sinuses lie between the periosteal and meningeal layers of the dura mater. They are best thought of as collecting pools of blood, which drain the central nervous system, the face, and the scalp. All the dural venous sinuses ultimately drain into the internal jugular vein
Label the arteries indicated
Note that the external carotid arteries remain external to the cranium and supply the face, scalp and neck
Label the arteries of the circle of willis
What do each of the following arteries supply:
- Anterior cerebral
- Middle cerebral
- Posterior cerebral
- Anterior cerebral - supplies the anteromedial portion of the cerebrum
- Middle cerebral - supply the majority of the lateral part of the brain.
- Posterior cerebral - supply both the medial and lateral parts of the posterior cerebrum.
Describe the clinical relevance of the danger triangle of the face
- The danger triangle of the face consists of the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla.
- Due to the special nature of the blood supply to the human nose and surrounding area, it is possible, albeit extremely unlikely, for retrograde infections from the nasal area to spread to the brain, causing cavernous sinus thrombosis, meningitis or brain abscess.
- This is possible because of venous communication (via the ophthalmic veins) between the facial vein and the cavernous sinus.
Describe the anatomy of the subarachnoid space in terms of:
- What is surrounds
- Where is it located
- What is contains
- Its function
Found between arachnoid mater and pia mater:
- completely surrounds both brain & spinal cord
- continuous
- cushions and protects the brain and spinal cord
Contains circulating cerebrospinal fluid (CSF)
Label the indicated structures
Describe the pathway of CSF from production to reabsorption
- CSF produced in the choroid plexus of the lateral ventricles
- The passes through the R and L foramina of monro (the interventricular foramina) into the 3rd ventricle
- The through the cerebral aqueduct into the 4th ventricle
- The passess mainly into the subarachnoid space but also some passes into the central canal of the spinal cord
- CSF is then absorbed from the subarachnoid space via arachnoid granulations into the dural venous sinuses
Where does the bleeding within the cranial cavity occur in each of the following and give an example of a common cause of each:
- Extradural haematoma
- Subdural haemoatoma
- Subarachnoid haematoma
- Extradural haematoma - bleeding occurs between the dura and bone, commonly due to a ruptured middle meningeal artery due to trauma to the pterion
- Subdural haemoatoma - bleeding occurs between the dural and subarachnoid mater, commonly due to torn cerebral veins due to falls in the elderly or people with alcohol problems
- Subarachnoid haematoma - bleeding occurs in the subarachnoid space commonly due to a ruptured berry aneurysm
What layers does the needle pass through in a lumbar puncture ?
- supra- and then interspinous ligaments
- ligamentum flavum
- epidural space (fat & veins) the destination of the epidural catheter
- then the lumbar puncture (spinal) needle continues..
- through the dura mater &
- arachnoid mater simultaneously …to reach the…
- subarachnoid space …to obtain the CSF sample
What are the different herinations which can occur in the brain as a result of raised ICP ?
Supratentorial herinations:
- Cingulate (subfalcine) - In cingulate or subfalcine herniation, the most common type, the innermost part of the frontal lobe is scraped under part of the falx cerebri
- central
- uncal - the uncus (medial part) of the temporal lobe herniates inferior to the tentorium cerebelli
- transcalvarial
Infratentorial herniations:
- upward
- downward or tonsillar herniation (herniation of the cerebellar tonsils): the cerebellar tonsils herniate into the foramen magnum
