Head - (Dura, Arachnoid, and PIa Mater) - Brain Meninges / Sinsus

Subarachnoid hematoma

Blood - areas of increased density in cisterns and fissures (subarachnoid space).

Dura mater

Dura mater is also supplied by: anterior meningeal arteries (from ethmoidal arteries), posterior meningeal arteries (from ascending pharyngeal arteries) meningeal branches of the ophthalmic arteries, occipital arteries, vertebral arteries, ascending pharyngeal arteries.

Head Injuries and Intracranial Hemorrhage

Epidural hemorrhage (hematoma) •is arterial in origin •results from tearing of the branches of the middle meningeal artery, which typically occurs in the region of the pterion •blood collects between the periosteal layer of the dura and the calvaria and under arterial pressure slowly expands •extravasated blood strips the dura from the cranium oUsually this follows a hard blow to the head: motor vehicle crashes, falls, and sports injuries. oTypically, trauma produces a minor loss of consciousness (concussion). oFollowing the injury the patient usually regains consciousness and has a lucid interval for a period of hours. oLater, drowsiness and coma (profound unconsciousness) occur, which may lead to death. Compression of the brain occurs as the blood mass increases - evacuation of the blood and occlusion of the bleeding vessel(s) are required

Meningeal spaces (Extradural or epidural space) -

Extradural or epidural space - between the cranium (bones) and the external periosteal layer of the dura; becomes the natural space only pathologically when blood from torn meningeal vessels pushes the periosteum away from the cranium. Epidural space is external to the periosteum lining the cranium - is not continuous with the spinal epidural space (a space occupied by epidural fat and a venous plexus) which is internal to the periosteum covering the vertebrae

Inferior sagittal sinus

Inferior sagittal sinus runs in the inferior free border of the falx cerebri and ends in the straight sinus.

cavernous sinus

Inside each cavernous sinus are the: •internal carotid artery surrounded by the carotid plexus of sympathetic nerves •abducent nerve (CN VI) Structures that are embedded in the lateral wall of the sinus: •oculomotor nerve (CN III) •trochlear nerve (CN IV) •ophthalmic nerve (CN V1) •maxillary nerve (CN V2) Pulsations of the artery within the cavernous sinus help to promote propulsion of venous blood from the sinus.

Middle meningeal artery, i

Middle meningeal artery, is a branch of the maxillary artery: •enters the middle cranial fossa through the foramen spinosum •divides into anterior (frontal) and posterior (parietal) branches •frontal branch of the middle meningeal artery runs superiorly to the pterion and then curves posteriorly to the vertex of the cranium •parietal branch of the middle meningeal artery runs posterosuperiorly

Subarachnoid hemorrhage

Subarachnoid hemorrhage •is an extravasation of blood, usually arterial, into the subarachnoid space. •Most subarachnoid hemorrhages result from rupture of a saccular aneurysm or berry aneurism (sac-like dilation on the side of an artery) - aneurysms of vessels supplying and around the arterial circle (of Willis). •Some subarachnoid hemorrhages are associated with head trauma involving cranial fractures and cerebral lacerations. •Bleeding into the subarachnoid space results in meningeal irritation, severe headache, stiff neck, and often loss of consciousness.

Subarachnoid space

Subarachnoid space, between the arachnoid and pia, is a natural space that contains CSF, arteries, and veins of pia mater.

Subdural hematoma

Subdural hematoma •results from venous bleeding usually from torn cerebral veins where they enter the superior sagittal sinus •extravasated blood that splits dura and arachnoid and creates a space at the dura-arachnoid junction oHemorrhage usually follows a hard blow to the head that jerks the brain inside the cranium and injures it. oHematomas may develop within 1 week after injury. oClinical signs include a headache, decreasing level of consciousness, ipsilateral pupillary dilation, and contralateral hemiparesis (weakness of the entire left or right side of the body).

Subdural space

Subdural space is a space between the dura and arachnoid that may develop as the result of trauma and hemorrhage (hard blow to the head).

Leptomeningitis (Clinical Correlation)

Symptoms: Headache, Seizures, Fever, Painful stiff neck. Diagnosis is made by performing a lumbar puncture and examining the CSF.

Thrombophlebitis of Facial Vein

Thrombophlebitis of the facial vein - inflammation of the facial vein with secondary thrombus formation. Pieces of an infected clot may enter the cavernous sinus and produce thrombophlebitis of the cavernous sinus. •Triangular area from the upper lip to the bridge of the nose is the danger triangle of the face (is drained by facial vein).

Dural venous sinuses

endothelium-lined spaces between the periosteal and meningeal layers of the dura carrying venous blood veins from the surface of the brain empty into these sinuses - most of the blood from the brain drains through them into the internal jugular veins

Arachnoid mater and pia mater

•Arachnoid mater is avascular. •Numerous web-like arachnoid trabeculae passing between the arachnoid and pia (the derivation of the arachnoid-pia from a single embryonic layer). •Pia mater is is highly vascularized by a network of blood vessels. The pia adheres to the surface of the brain and follows all its contours. When the cerebral arteries penetrate the cerebral cortex, the pia follows them for a short distance, forming a pial coat and a peri-arterial space.

Metastasis of Tumor Cells to Dural Venous Sinuses

•Basilar and occipital sinuses communicate through the foramen magnum with the internal vertebral venous plexuses. •These venous channels are valveless. •Tumor cells from thorax, abdomen, or pelvis may spread to the vertebrae and brain (blood may flow in opposite direction) because intercostal and lumbar veins, veins of pelvis anastomose with internal vertebral plexus.

•Basilar plexus

•Basilar plexus (sinus) connects the inferior petrosal sinuses and communicates inferiorly with the internal vertebral venous plexus

Fractures of Cranial Base

•Basilar skull fracture is a fracture of the base of the skull, typically involving the temporal bone, occipital bone, sphenoid bone, ethmoid bone. •Fractures can cause tears in meninges - leakage of the cerebrospinal fluid (CSF). The leaking fluid: •may accumulate in the middle ear cavity, and dribble out through a perforated eardrum (CSF otorrhea) •may accumulate into the nasopharynx via the eustachian tube, causing a salty taste •may also drip from the nose (CSF rhinorrhea) in fractures of the anterior skull base •Signs and symptoms: •Battle's sign - subcutaneous ecchymosis in the mastoid region. •Raccoon eyes - bruising around the eyes, "black eyes" •Cerebrospinal fluid rhinorrhea •Cranial nerve palsy •Bleeding (sometimes profuse) from the nose and ears •Hemotympanum •Conductive or perceptive deafness, nystagmus, vomitus •Optic nerve may be compressed by the broken skull bones, causing irregularities in vision. •Serious cases usually result in death

Occlusion of Cerebral Veins and Dural Venous Sinuses (Blood Clot)

•Causes: blood clots, thrombophlebitis, tumors. •The most frequently thrombosed sinuses: transverse, cavernous, and superior sagittal sinuses.

•Cavernous sinus

•Cavernous sinus is located on each side of the sella turcica on the upper surface of the body of the sphenoid. It receives blood from the superior and inferior ophthalmic veins, superficial middle cerebral vein, and sphenoparietal sinus.

Subdural hematoma

•Crescentic area of increased density between the brain and the skull - acute hematoma. Mass effect causes a midline shift. •Area of decreased density - chronic hematoma. Midline shift.

Dural Origin of Headaches

•Dura mater is sensitive to pain, especially where it is related to the dural venous sinuses and meningeal arteries (numerous pain fibers). •Pulling on vessels, distension of the meningeal vessels may be the causes of headache. •Headache occurring after a lumbar spinal puncture for removal of CSF. When CSF is removed, the brain sags slightly, pulling on the dura mater; this causes a headache. For this reason, patients are asked to keep their heads down after a lumbar puncture to minimize the pull on the dura mater, reducing the chances of getting a headache. •Pain arising from the dura mater is generally referred, perceived as a headache arising in regions supplied by the involved cervical nerve or division of the trigeminal nerve.

Thrombophlebitis of Facial Vein

•Facial vein has clinically important connections with the cavernous sinus through the superior ophthalmic vein, and the pterygoid venous plexus through the inferior ophthalmic and deep facial veins - infection of the face may spread to the cavernous sinus and pterygoid venous plexus. •Blood from the medial angle of the eye, nose, and lips usually drains inferiorly through the facial vein. Because the facial vein has no valves, blood may pass through it in the opposite direction - from the face to the cavernous sinus. •Thrombophlebitis of the facial vein - inflammation of the facial vein with secondary thrombus formation. Pieces of an infected clot may enter the cavernous sinus and produce thrombophlebitis of the cavernous sinus. •Triangular area from the upper lip to the bridge of the nose is the danger triangle of the face (is drained by facial vein).

Fracture of Pterion

•Fracture of the pterion can be life threatening because it overlies the frontal branches of the middle meningeal vessels (lie in grooves on the internal aspect of the lateral wall of the calvaria). •The pterion is two fingers' breadth superior to the zygomatic arch and a thumb's breadth posterior to the frontal process of the zygomatic bone. •A hard blow to the side of the head may fracture the bones forming the pterion, producing a rupture of the frontal branch of the middle meningeal artery or vein. •The resulting epidural hematoma exerts pressure on the underlying cerebral cortex. An untreated middle meningeal vessel hemorrhage may cause death in a few hours.

Frontal emissary vein

•Frontal emissary vein passes through the foramen cecum of the cranium, connecting the superior sagittal sinus with veins of the frontal sinus and nasal cavities.

•Inferior petrosal sinuses

•Inferior petrosal sinuses run in a grooves between the petrous parts of the temporal bones and the basilar part of the occipital bone, drain the cavernous sinus into the transition of the sigmoid sinus to the internal jugular vein at the jugular foramen.

•Leptomeningitis

•Leptomeningitis is an inflammation of the leptomeninges (arachnoid and pia) resulting from bacterial and viral infections. Aseptic causes: drug reactions, autoimmune diseases, cancer. •The bacteria may enter the subarachnoid space through the blood (septicemia), spread from an infection of the heart, lungs, or other viscera. •Microorganisms may also enter the subarachnoid space from a compound cranial fracture or a fracture of the nasal sinuses. •Acute purulent meningitis can result from infection with many pathogenic bacteria, most typical is meningococcal meningitis.

•Mastoid emissary vein (bilateral) passes through the mastoid foramen and connects each sigmoid sinus with the occipital or posterior auricular vein.

•Mastoid emissary vein

Dural infoldings (reflections

•Meningeal layer of dura mater reflects away from the external periosteal layer of dura to form dural infoldings (reflections). •Dural infoldings divide the cranial cavity into compartments, forming partial partitions (septa) between parts of the brain and providing support for parts of the brain. •Dural infoldings include the: •Falx cerebri (cerebral falx). •Tentorium cerebelli (cerebellar tentorium). •Falx cerebelli (cerebellar falx). •Diaphragma sellae (sellar diaphragm).

Occipital sinus

•Occipital sinus lies in the attached border of the falx cerebelli and ends in the confluence of sinuses, communicates inferiorly with the internal vertebral venous plexus.

•Parietal emissary vein

•Parietal emissary vein (may be bilateral) passes through the parietal foramen in the calvaria, connecting the superior sagittal sinus with the veins of the scalp.

•Posterior condylar emissary vein passes through the condylar canal, connecting the sigmoid sinus with the veins in suboccipital region.

•Posterior condylar emissary vein

Brain meninges

•Protect the brain. •Form the supporting framework for arteries, veins, and venous sinuses. •Enclose a fluid-filled cavity, the subarachnoid space. 1.Dura mater (dura): tough, thick external fibrous layer. 2.Arachnoid mater (arachnoid): thin intermediate layer. 3.Pia mater (pia): delicate internal vasculated layer. •The intermediate and internal layers (arachnoid and pia) collectively make up the leptomeninx. The arachnoid is separated from the pia by the subarachnoid (leptomeningeal) space, which contains cerebrospinal fluid (CSF)

•Sigmoid sinuses

•Sigmoid sinuses follow S-shaped courses in the posterior cranial fossa (grooves in the temporal and occipital bones) then continue as the internal jugular veins after passing through the jugular foramen.

Sphenoparietal sinuses

•Sphenoparietal sinuses are related to the lesser wings of sphenoid.

Straight sinus

•Straight sinus (sinus rectus) is formed by the union of the inferior sagittal sinus with the great cerebral vein. It runs along the line of attachment of the falx cerebri to the tentorium cerebelli, joins the confluence of sinuses.

•Superior petrosal sinuses

•Superior petrosal sinuses run in the anterolateral margin of the tentorium cerebelli, attached to the superior border of the petrous part of the temporal bone, drain the cavernous sinus into the transverse sinuses at the site of formation of the sigmoid sinuses

Superior sagittal sinus

•Superior sagittal sinus lies in the superior attached border of the falx cerebri; begins at the crista galli and ends at the internal occipital protuberance joining the confluence of sinuses, a meeting place of the superior sagittal, straight, occipital, and transverse sinuses.

Tentorial Herniation

•Tentorial notch is slightly larger than is necessary to accommodate the midbrain. •Space-occupying lesions, such as tumors in the supratentorial compartment, intracranial hematomas produce increased intracranial pressure, and may cause part of the adjacent temporal lobe of the brain to herniate through the tentorial notch. •During tentorial herniation, the temporal lobe may be lacerated by the tough tentorium cerebelli, and the oculomotor nerve (CN III) may be injured (stretching, compression). Oculomotor lesions may produce paralysis of the extrinsic eye muscles supplied by CN III.

Transverse sinuses

•Transverse sinuses pass laterally from the confluence of sinuses (grooves in the occipital bone) along the posterolateral attached margins of the tentorium cerebelli and then become the sigmoid sinuses.

Emissary veins

•connect the dural venous sinuses with veins outside the cranium, passing through cranial bones •are valveless and blood may flow in both directions, usually away from the brain •size and number of emissary veins vary; many small ones are unnamed •infection can enter the cranial cavity through emissary vein •diploic veins may communicate with sinuses and veins outside cranium via emissary veins

Falx cerebri

•separates the right and the left cerebral hemispheres •attaches in the median plane to the internal surface of the calvaria, from the frontal crest of the frontal bone and crista galli of the ethmoid bone anteriorly to the internal occipital protuberance posteriorly •becomes continuous with the tentorium cerebelli

Dura mater

•two layers: •external periosteal layer of dura (endocranium) adheres to the internal surface of the cranium, is continuous at the cranial foramina with the periosteum on the external surface of the calvaria •internal meningeal layer is fused with the periosteal layer (except the dural sinuses and infoldings of dura mater), is continuous with the dura mater of the spinal cord forming its dural sac