The Meninges Flashcards
What are the three membranous layers lining the brain and spinal cord?
From superficial to deep:
1) Dura mater
2) Arachnoid mater
3) Pia mater
What is the function of the meninges?
Clinical importance?
1) Provide a supportive framework for the cerebral and cranial vasculature.
2) Acting with cerebrospinal fluid (CSF) to protect the CNS from mechanical damage.
Common site of infection and intracranial bleeds.
What pathology is associated with the meninges?
Intracranial bleeds and meningitis.
Within the cranium, the dura mater is divided into two layers. These are…
1) Peri-osteal layer
2) Meningeal layer
Between these two layers, the dural venous sinuses are located that ultimately drain blood into the internal jugular veins.
What are the main dural reflections within the cranium?
1) Tentorium cerebelli - separates the occipital lobe from the underlying cerebellum and brainstem.
2) Falx cerebri - connects to the crista galli anteriorly and the straight sinus posteriorly.
3) Falx cerebelli - inferior to the tentorium cerebelli but otherwise runs in the same orientation as the falx cerebri.
4) Diaphragm sellae - runs over the hypophyseal fossa and provides the roof of the pituitary gland, with the exception of a hole in the centre.
Vascular supply of the dura mater?
Associated foramina?
Middle meningeal artery (branch of the maxillary artery) - is transmitted through the foramen spinosum.
Middle meningeal vein.
What innervates the dura mater?
The trigeminal nerve.
Specifically, it is the nervosus spinosus of the mandibular branch.
Clinical relevance: extradural and subdural haemotomas
A haematoma is a collection of blood. If a haematoma develops within the cranium, this will lead to increased intra-cranial pressure and subsequent death.
Extradural - between the skull and periosteal dura mater - usually due to middle meningeal artery rupture in brain trauma.
Subdural - between the dura and arachnoid mater - results from damage to cerebral veins as they empty into dural venous sinuses.
Describe features of the arachnoid mater.
Avascular and doesn’t receive any innervation.
Projections of the arachnoid mater into the dura mater is known as arachnoid granulations - this allows CSF to drain into dural venous sinuses. It only attaches to the cerebrum from gyri to gyri.
Where is CSF stored?
Beneath the arachnoid mater in a space known as the subarachnoid space.
Describe features of the pia mater.
Very thin and adheres on all surfaces of the brain (gyri and sulci) and the spinal cord. It is highly vascularlised to supply the underlying neural tissue.
Clinical relevance: meningitis
Inflammation of the meninges.
Can be caused by pathogens and drugs.
Bacteria is the most common infective cause - Neisseria meningitidis and Streptococcus pneumoniae. Immune response causes cerebral oedema, increasing intra-cranial pressure. This has two effects: - cranial herniation - reduces cerebral perfusion This can rapidly lead to death.
