Cranial Cavity Lecture Notes PDF 2024-2025

CRANIAL CAVITY Prof. Dr. Mona Zoair- Prof. Dr. Doaa Haiba 1-5/12/2024  Objectives of the lecture 1. Define the 3 membranes covering the brain (meninges). 2. Identify and compare between the layers of the dura mater. 3. List and define the dural folds and identify t...

CRANIAL CAVITY Prof. Dr. Mona Zoair- Prof. Dr. Doaa Haiba 1-5/12/2024  Objectives of the lecture 1. Define the 3 membranes covering the brain (meninges). 2. Identify and compare between the layers of the dura mater. 3. List and define the dural folds and identify their positions and attachments 4. List the nerves and arteries supplying dura in the 3 cranial fossae. 5. Define origin course and divisions of middle meningeal artery. 6. Define the dural venous sinuses, enumerate single and paired ones and identify their positions 7. Identify the position, relations, contents, tributaries, drainage and communications of cavernous sinus. 8. Define intracranial course and list important branches of internal carotid artery 9. Identify intracranial course of the cranial nerves  MENINGES Subdural space Dura mater: The outer fibrous layer which is attached to the bones of the skull. Arachnoid mater: The middle layer which is separated from the dura by the subdural space. Pia mater: The inner layer which is attached to the brain surface. It is separated from the arachnoid by the subarachnoid space which contains the cerebral vessels and cerebrospinal fluid.  DURA MATER The dura mater consists of 2 layers: 1. The outer endosteal layer 2. The inner fibrous meningeal layer. Over the vault of the skull, the 2 layers are fused and can be easily stripped away from the bone as a single sheet. At certain sites, the 2 layers are separated to enclose the dural venous sinuses between them.  DURA MATER Outer layer Inner layer It is rough because it is attached to the bone by It is a strong, fibrous dense membrane which fibrous processes and lines inner surface of covers and protects the brain and forms tubular skull bones extensions around the cranial nerves. It is not continuous with the dura of the spinal It is continuous with the dura of the spinal cord cord at the foramen magnum. through the foramen magnum.  DURAL FOLDS They are 4 folds inside the cranial cavity which divide it into spaces lodging the parts of the brain. These folds minimize the rotary displacement of the brain. They are: 1. Falx cerebri 2. Tentorium cerebelli 3. Falx cerebelli 4. Diaphragma sellae  DURAL FOLDS 1. Falx cerebri ▪ It is a crescent-shaped midline fold in-between the two cerebral hemispheres. ▪ Its anterior narrow margin (apex) is attached to the crista galli of the ethmoid bone and frontal crest of frontal bone. ▪ Its posterior broad margin is attached to the upper surface of the tentorium cerebelli in the midline.  DURAL FOLDS 2. Tentorium cerebelli ▪ It is a horizontal tent-like fold separating posterior parts of cerebral hemispheres from cerebellum in posterior cranial fossa. ▪ It has 2 margins attached and free. ▪ Attached margin is attached to: a) Posterior clinoid process b) Upper border of petrous part of temporal bone c) Margins of groove for transverse sinus. ▪ Free margin It is a U-shaped margin , which bounds an oval opening called the tentorial notch surrounding the midbrain and attached to the anterior clinoid process.  DURAL FOLDS 3. Falx cerebelli ▪ It is a small crescentic fold in the midline of the posterior cranial fossa between the two cerebellar hemispheres. ▪ This fold is attached posteriorly to the internal occipital crest and above to tentorium cerebelli. ▪ Anterior edge is free between 2 cerebellar hemispheres.  DURAL FOLDS 4. Diaphragma sellae ▪ It is a small horizontal fold of dura, which covers the pituitary gland in the hypophyseal fossa. ▪ It is perforated centrally for the passage of the infundibulum (pituitary stalk).  DURA MATER Nerve supply of the dura: Most of the supratentorial part by the ophthalmic nerve (Tentorial nerve). The dura of the anterior cranial fossa : 1. Anterior ethmoidal nerve. 2. Posterior ethmoidal nerve. The dura of the middle cranial fossa : 1. Nervous spinosus. 2. Meningeal branch of maxillary nerve The dura of the posterior cranial fossa by meningeal branches of the 10th &12th cranial nerves The dura around foramen magnum by 1st ,2nd & 3rd cervical nerves.  DURA MATER Arterial supply of the dura: The dura of the anterior cranial fossa : 1. Anterior ethmoidal artery 2. Posterior ethmoidal artery. The dura of the middle cranial fossa : 1. Middle meningeal artery. 2. Accessory meningeal artery. 3. Recurrent branch of lacrimal artery The dura of the posterior cranial fossa: 1. Vertebral artery 2. Occipital artery 3. Ascending pharyngeal artery  MIDDLE MENINGEAL ARTERY Origin Arises from the 1st part of maxillary artery. Course: It enters the cranial cavity through the foramen spinosum. Then it runs forwards and laterally in a groove on the squamous part of the temporal bone. It ends by dividing into: 1. Anterior branch (to anterior part of dura) runs upwards grooving bones at pterion. 2. Posterior branch (to posterior part of dura) runs upwards and backwards till lambda.  DURAL VENOUS SINUSES Definition: They are venous spaces present between the layers of dura. Characters: They are lined by endothelium. Their walls are devoid of muscular tissue. They possess no valves. They are communicated with the veins outside the cranial cavity through emissary veins. They receive venous blood from the brain, skull diploe , orbit and internal ear. They are drained into the internal jugular vein.  DURAL VENOUS SINUSES Single sinuses: 1. Superior sagittal sinus in the convex margin of falx cerebri 2. Inferior sagittal sinus in the lower concave free margin of falx cerebri 3. Straight sinus in the junction between falx cerebri and tentorium cerebelli 4. Anterior and posterior intercavernous sinuses on anterior and posterior margins of diaphragma sellae 5. Occipital sinus (not viewed) in the attached margin of falx cerebelli 6. Basilar plexus of sinuses on clivus of skull  Dural Venous Sinuses Paired sinuses 1. Sphenoparietal sinus on posterior edge of lesser wing of sphenoid 2. Cavernous sinus on each side of body of sphenoid bone and pituitary gland. 3. Superior petrosal sinus on upper border of petrous part of temporal bone. 4. Inferior petrosal sinus in groove between betrous temporal and basilar occipital bones. 5. Transverse sinus in the circumference of tentorium cerebelli. 6. Sigmoid sinus is the continuation of transverse sinus grooving the inner surface of base of petrous bone  DURAL VENOUS SINUSES Single Sinuses Paired Sinuses  CAVERNOUS SINUS Position: Lies on each side of the body of sphenoid and the pituitary gland. Extends from : 1. Anteriorly : the medial end of superior orbital fissure 2. Posteriorly: to the apex of the petrous bone  CAVERNOUS SINUS Relations Medially: 1. Pituitary gland. 2. Sphenoidal air sinus Laterally: 1. Brain Brain 2. Trigeminal ganglion. ▪ Nerves embedded in the lateral wall: From above downwards: − Oculomotor (3rd cr.) − Trochlear (4th cr.) − Ophthalmic (1st of 5th cr.) − Maxillary nerve. (2nd of 5th cr.) Contents: 1. Internal carotid artery 2. Abducent nerve (6th cr)  CAVERNOUS SINUS Central vein of retina Sphenoparietal Tributaries sinus Central vein of retina Middle Superior and inferior meningeal vein ophthalmic veins Sphenoparietal sinus Meningeal veins Cerebral veins Drainage The sinus drains posteriorly into: The superior petrosal sinus to the transverse sinus The inferior petrosal sinus to the internal jugular vein  CAVERNOUS SINUS Communications: Medially: other cavernous sinus and basilar plexus of sinuses Inferiorly: Pterygoid and pharyngeal plexuses by emissary veins passing through the foramen ovale and carotid canal. Anteriorly: anterior facial vein by superior ophthalmic vein  INTERNAL CAROTID ARTERY Anterior clinoid process Anterior cerebral artery Anterior Course: cerebral artery It enters the cranial cavity through the carotid canal in the petrous part of the temporal bone then it traverses foramen Cavernous lacerum. sinus It then passes upward and forward in the Foramen cavernous sinus (without communicating lacerum with it). Carotid The artery then leaves the sinus and canal passes upward again medial to the anterior clinoid process of the sphenoid bone. The internal carotid artery then inclines backward and terminates by dividing into the anterior and the middle cerebral Internal arteries to the brain. carotid artery  Internal Carotid Artery Important branches: 1. Ophthalmic artery to orbit 2. Anterior cerebral artery to brain 3. Middle cerebral artery to brain 4. Anterior choroidal artery to brain 5. Posterior communicating artery to brain  INTRACRANIAL COURSE OF CRANIAL NERVES 1. Olfactory nerve: Its fibers pass from nasal mucosa through cribriform plate of ethmoid bone to end in olfactory bulb. 2. Optic nerve: It leaves the orbit through the optic canal to enter the cranial cavity. Then, it unites with that of the opposite side to form the optic chiasma. 3. Oculomotor nerve: It passes in the lateral wall of cavernous sinus then divides into superior and inferior branches enter the orbit through superior orbital fissure.  INTRACRANIAL COURSE OF CRANIAL NERVES 4. Trochlear nerve passes in the lateral wall of cavernous sinus then enters orbit through superior orbital fissure. 5. Trigeminal nerve: 3 terminal branches arise from trigeminal ganglion: Ophthalmic nerve runs in the lateral wall of the cavernous sinus below the trochlear nerve then enters orbit through superior orbital fissure Maxillary nerve runs in the lateral wall of the cavernous sinus below the ophthalmic nerve then enters the pterygopalatine fossa through the foramen rotundum. Mandibular nerve enter the infratemporal fossa through the foramen ovale  INTRACRANIAL COURSE OF CRANIAL NERVES 6. Abducent nerve: It pierces dura at clivus then passes in the floor of cavernous sinus and enters orbit through superior orbital fissure. 7. Facial and auditory nerves (7,8): They enter the internal acoustic meatus 8. Glossopharyngeal, vagus, accessory nerves (9, 10, 11): They pass through jugular foramen 8. Hypoglossal nerve (12) passes through hypoglossal canal  IN CLASS EXERCISE Attached margin of tentorium cerebelli is attached to which of the following bony landmarks? A. Anterior clinoid process B. Posterior clinoid process C. Crista galli of ethmoid bone D. Frontal crest of frontal bone Which of the following paired dural venous sinus is labeled by the black arrow? A. Cavernous B. Inferior petrosal C. Straight D. Transverse  IN CLASS EXERCISE Which of the following cranial nerves runs in the floor of cavernous sinus? A. Oculomotor B. Trochlear C. Trigeminal D. Abducent List three tributaries of cavernous sinus  SOURCES& REFERENCES Books Videos Dural folds https://www.youtube.com/watch?v=Ck2om QfabdI Dural venous sinuses https://www.youtube.com/watch?v=TX5Fxr g4SD4 Chapter : Head& Neck Chapter : Head& Neck Cranial cavity: 1547- Lecture Notes PDF Cranial cavity: 873-876, 1558, 1660 886-889. 896-900 Thank You [email protected]