Overview of the Brain, Cranial Nerves, Blood Supply and Meninges

Objectives Name the parts of the brain and describe their main anatomical features Describe the attachments of the cranial nerves to the surface of the brain Describe the course and list the main branches of the vertebral, basilar and internal carotid arteries Name the arteries that form the cerebral arterial circle (of Willis) Indicate the location of the septa formed by the crania dura mater Indicated the location of the dural venous sinuses and understand the direction of blood flow through them Describe the anatomical relations of the cavernous sinus

Parts of the Brain brainstem: medulla oblongata pons midbrain cerebellum diencephalon: thalamus hypothalamus telencephalon (cerebral hemispheres)

thalamus hypothalamus

subcortical white matter cerebellar nuclei subcortical white matter cerebellar cortex

hypothalamus thalamus

hypothalamus

right thalamus left thalamus

Medial Surface of the Left Cerebral Hemisphere

central sulcus lateral sulcus insula

Lateral Ventricles there are 2 of them, 1 in each cerebral hemisphere parts: anterior (frontal) horn body (within parietal lobe) inferior (temporal) horn posterior (occipital) horn trigone (atrium)  area where body, inferior horn and posterior horn meet each other each lateral ventricle communicates with 3rd ventricle via interventricular foramen (of Monro)

Arterial Supply of the Brain it is provided by 2 pairs of arteries: vertebral and internal carotid vertebral artery: enters cranial cavity via foramen magnum right and left vertebral arteries join each other at pontomedullary junction to form basilar artery basilar artery runs along midline of anterior surface of pons and ends at upper end of pons by dividing into 2 posterior cerebral arteries vertebral and basilar arteries give branches that supply spinal cord, brainstem, cerebellum and posterior parts of cerebral hemispheres

Cerebral Arterial Circle (of Willis) formed by large cerebral arteries and their interconnections on ventral surface of the brain components: anterior communicating a. anterior cerebral a. internal carotid a. posterior communicating a. posterior cerebral a. serves as a potential vascular shunt, assisting in development of collateral circulation if one of the proximal vessels is occluded

Arterial Supply of the Brain internal carotid artery: begins at bifurcation of common carotid artery (at level of upper border of thyroid cartilage) parts: cervical (from origin to base of the skull) petrous (within carotid canal in petrous part of temporal bone) cavernous (within cavernous sinus the dural venous sinus located in middle cranial fossa, just lateral to sella turcica) cerebral (from the point it exits cavernous sinus to its termination, where it divides into anterior and middle cerebral arteries)

cerebral part cavernous part petrous part cervical part

cerebral part of internal carotid artery cavernous part of internal carotid artery

Arterial Supply of the Brain internal carotid artery (cont.): main branches: ophthalmic artery enters orbit via optic canal together with optic nerve posterior communicating artery joins posterior cerebral artery 2 terminal branches: anterior and middle cerebral arteries (right and left anterior cerebral arteries are connected by anterior communicating artery)

Aneurysms

Patient Case Patient is a 65 yo male who presented after having an acceleration/deceleration injury from a MVA 1 week ago. He c/o right neck pain and feel like he keeps dropping things with his right hand. What do you want to know?

You do an adjustment! & Request that he return in 1 week

He doesn’t show for his next appointment He doesn’t show for his next appointment. When you call to ask him about it, you find he has been admitted to the hospital on the evening of your first encounter.

Hollnehorst plaque on fundoscopic exam

Dura Mater of the Brain layers: endosteal (outer layer)  equivalent to periosteum covering inner surface of skull bones meningeal (inner layer)  dura mater proper, faces the brain the two layers are closely united, except where they separate to form dural venous sinuses

endosteal layer of dura mater meningeal layer of dura mater

Dura Mater of the Brain meningeal layer forms 4 septa  divide cranial cavity into freely communicating compartments cerebral falx (falx cerebri)  sickle-shaped fold that lies in the midline between two cerebral hemispheres cerebellar tentorium (tentorium cerebelli)  crescent-shaped fold that roofs over posterior cranial fossa (separates cerebellum from occipital lobes of cerebral hemispheres) tentorial notch  space between anterior, free border of tentorium cerebelli and dorsum sellae  filled mostly by midbrain cerebellar falx (falx cerebelli)  small sickle-shaped fold in posterior cranial fossa that projects between two cerebellar hemispheres sellar diaphragm (diaphragma sellae)  small circular fold that roofs over sella turcica (has small opening for pituitary stalk)

Dural Venous Sinuses located between inner and outer layers of dura mater receive blood from brain (via superficial and deep cerebral veins) as well as cerebrospinal fluid from subarachnoid space (via arachnoid granulations) blood collected by dural venous sinuses drains ultimately into internal jugular veins

Dural Venous Sinuses superior sagittal sinus: runs along upper border of falx cerebri  begins anteriorly at foramen cecum and terminates posteriorly in confluence of the sinuses (over internal occipital protuberance) inferior sagittal sinus: runs along lower, free border of falx cerebri, joins great cerebral vein (largest of the deep cerebral veins) to form straight sinus straight sinus: runs in midline, along junction of falx cerebri and tentorium cerebelli  terminates posteriorly in confluence of the sinuses

Dural Venous Sinuses transverse sinus: begins in confluence of the sinuses and runs along posterior border of tentorium cerebelli  when it reaches petrous part of temporal bone, it turns down to become continuous with sigmoid sinus sigmoid sinus: direct continuation of transverse sinus  terminates in jugular foramen, where it becomes continuous with internal jugular vein occipital sinus: small sinus that runs along posterior border of falx cerebelli  ends superiorly in confluence of the sinuses and inferiorly communicates with internal vertebral venous plexus (within vertebral canal)

Dural Venous Sinuses cavernous sinus: located in middle cranial fossa, one on each side of sella turcica drains contents of orbit, parts of cerebral hemisphere, pituitary gland and sphenoparietal sinus internal carotid artery and abducens nerve are located inside cavernous sinus cranial nerves III and IV and V1 and V2 divisions of trigeminal nerve are embedded in lateral wall of sinus it is drained posteriorly by superior and inferior petrosal sinuses

Dural Venous Sinuses superior petrosal sinus: runs along superior border of petrous part of temporal bone  connects cavernous sinus with terminal part of transverse sinus inferior petrosal sinus: runs along inferior border of petrous part of temporal bone (between petrous part and occipital bone)  connects cavernous sinus with internal jugular vein sphenoparietal sinus: small sinus that runs along posterior border of lesser wing of sphenoid  drains into cavernous sinus