Cranium-Wilson Flashcards
The spinal cord is surrounded by what 3 sacs?
dura mater
arachnoid mater
pia (outer layer of cord)
The entire CNS, including the brain, is surrounded by?
dura mater
In the cranium, the dura mater is fused to? What are the two layers of the dura mater?
periosteum
two layers of the dura mater: pericranium/periosteum fused with dura mater proper
Reflecting the dura reveals which meninge that lies on and surrounds the surface of the brain?
arachnoid mater
What is the dural fold that separates the cerebral hemispheres?
falx cerebri
What is the function of the tentorium cerebeli dural fold?
- tentorium (tent) cerebelli covers the posterior cranial fossa.
- separates the cerebellum from the occipital lobe of the cerebral cortex
What is the diaphragm sellae?
a flat piece of dura mater with a circular hole allowing the vertical passage of the pituitary stalk of the pituitary gland
What is Rathke’s pouch?
In embryogenesis, Rathke’s pouch is an evagination at the roof of the developing mouth in front of the buccopharyngeal membrane. It gives rise to the anterior pituitary (adenohypophysis), a part of the endocrine system.
The pituitary gland has two parts. What types of tumors may each part form?
-ANTERIOR pituitary may form a craniopharyngioma
(from embryonic tissue) in CHILDREN
-POSTERIOR pituitary may form adenoma in ADULTS
Midline lesions at the chiasm cause what kind of deficits?
Deficits are binocular, bitemporal and heteronymous
Pituitary adenoma (enlargement of the posterior pituitary) begins as bitemporal ___________ quadrantanopsia.
Craniopharyngioma (enlargement of the anterior pituitary) begins as bitemporal ____________quadrantanopsia.
superior
inferior
All bones are surrounded by what?
periosteum
The two layers of the dura mater eventually become separated to form what?
venous sinuses: veins that drain blood away from cranium, the brain in particular
What is the falx cerebelli?
- not as prominent as the falx cerebri
- in the posterior cranial fossa the cerebellum
- a small sickle shaped fold of dura mater, projecting forwards into the posterior cerebellar notch as well as projecting into the vallecula of the cerebellum between the two cerebellar hemispheres.
T/F. Anterior pituitary is derived from the inside of the oral cavity embryologically.
True!
Some of the axons of the optic nerve coming from the right eye bulb will cross over and go to the left side of the brain. Vice versa.
optic chiasma is a place where retinal fibers/axons cross from one side of the brain to the other
-as the tumor enlarges, most of the direct pressure is on the optic chiasma causing a blockage of function of those axons producing partial blindness
The lateral quadrants of the visual field are?
temporal hemiretina
The medial quadrants of the visual field are?
nasal hemiretina
T/F. The brain does not have any pain fibers.
True!
The meninges covering the brain has pain fibers
What is the main nerve that supplies the meninges of the brain?
trigeminal nerve
Where does the meninges covering the anterior and middle cranial fossa get its innervation from?
V1 (anterior), V2, V3 (middle) of the trigeminal nerve
Where does the tentorium cerebelli get its innervation from?
V1 of the trigeminal nerve
Where does the meninges covering the POSTERIOR cranial fossa get its innervation from?
C2 and C3
If the dura mater is irritated or inflamed for any reason it was cause what?
headache
- pain from the dura mater is headache
- inflamed blood vessels stimulate pain fibers in the meninges
If the sensory nerves running with the blood vessels supplying the meninges get swollen or irritated, what will they cause?
headache
The brain is not innervated and can be damaged with no pain or sensation!!!!
FACTS!!!!!
However if blood comes into contact with the meninges, it is an irritant producing an extremely severe headache
Blood is a very caustic substance that will irritate the nerve endings and produce intense headaches when an individual has a hemorrhaging stroke. Explain.
- If the blood vessels that run with the dura mater become inflamed or swollen they can stimulate a pain stimulus
- Hemorrhage (release of blood into the cranium) can also
The middle meningeal artery is one of the branches of what artery? What does it supply?
maxillary artery in the infratemporal fossa
-supplies the dura
Middle meningeal artery runs where?
- runs between the skull and periosteum
- it produces a groove in the skull
What are the two terminal branches of the external carotid artery?
- superficial temporal artery
- maxillary artery
What are the 8 branches of the external carotid artery?
Some Anatomists Like Freaking Out Poor Medical Students
- Superior thyroid
- Ascending pharyngeal
- lingual
- facial
- occipital
- posterior auricular
- maxillary
- superficial temporal
The major branch of the maxillary artery gives access to the skull. Explain.
- middle meningeal artery gives access to the cranial vault by going through the foramen spinosum
- identify the groove by the middle meningeal artery depression which goes to the foramen spinosum
-the middle meningeal artery enters the skull through the foramen spinosum
Why is the relationship of the middle meningeal artery to skull important?
- the middle meningeal artery passes through the lateral part of skull which is very thin (pterion)
- skull fractures may tear the meningeal artery producing an epidural hematoma
What is an epidural hematoma?
hemorrhage will occur between skull and the pericranium
- this is a painful type of stroke or hematoma
- as hematoma gets larger and larger, it pulls the periosteum from the bone (skull)
What are the consequences of an epidural hematoma?
- stripping the periosteum from the skull: allowing the hematoma to get larger
- compression of the brain (cerebral cortex): whatever cortex functions will be lost; pressure will then move to the other side of the cortex producing loss of cortex functions contralaterally for wherever the hematoma is located: loss of consciousness
- herniation of uncus (of the temporal lobe) through the space between the tentorium cerebelli and the midbrain and pons : causes compression of CN III (oculomotor nerve) and dilation of pupil
- increased pressure causes herniation of structures in the posterior cranial fossa through the foramen magnum specifically the cerebellar tonsils
- arteries are under a lot of pressure and may clot
Parasympathetic fibers of the oculomotor nerve are the most susceptible to uncal herniation. Explain.
innervate the sphincter pupillary muscle: smooth muscle that causes pupils to constrict in bright light
What are the early signs of uncal herniation and epidural hematomas?
dilation of pupils
-Oculomotor nerve is the nerve that is compressed and it has both somatic fibers going to extraocular muscles to move your eyes around in space and also parasympathetic nerve fibers to constrict pupils.
What are the consequences of herniation of cerebellar tonsils through the foramen magnum?
-compression of the medulla: has control centers for breathing and heart rate and how hard the heart pumps
- cushing triad
- death
What is the Cushing triad?
triad of symptoms that occur when you apply pressure to the respiratory centers of the medulla oblongata:
- respiratory rates become irregular
- bradycardia
- systolic hypertension: the distance between the systolic and diastolic pressure gets greater and greater; because the heart is slowing down the centers in the brain is saying we’re not getting enough oxygen to the brain so the heart pumps harder to get get blood to the brain
Arnold Chiari Type II malformation
Chiari malformation type 2 (CM type II) is a type of Chiari malformation in which both the cerebellum and brain stem tissue extend into the foramen magnum
-this can cause NONcommunicating hydrocephalus
CT blood characteristics
bone is bright on CT
- bright blood is acute blood
- dark blood is chronic
Talk and Die patient
- initially the neurological function is relatively normal
- as lesion enlarges the level of consciousness deteriorates rapidly
- eventually medulla is being compression due to the herniation of the cerebellum through the foramen magnum causing disruption of the heart and breathing centers of the brainstem causing death
The edges of the falx cerebri contain what?
large veins called sinuses
- superior sagittal sinus
- inferior sagittal sinus
- straight sinus: continuation of the inferior sagittal sinus back to the back of the skull
sagittal sinuses are curved in shape
T/F. The dural reflections of the falx cerebri and tentorium are perpendicular to one another.
True
The union of the falx cerebri and tentorium contains what?
straight sinus
What is the great cerebral vein of Gallen?
another structure that joins the inferior sagittal sinus to form the straight sinus
The straight, superior sagittal, and cerebellar sinuses drain into the confluens of sinuses.. What is confluens of sinuses?
The confluence of sinuses (torcular herophili, or torcula) is the connecting point of the superior sagittal sinus, straight sinus, and cerebellar sinus.
What comes off of the confluens of sinuses?
transverse sinus: drains blood toward the jugular foramen; becomes the sigmoid sinus which takes you right to the jugular foramen (internal jugular vein which empties into the subclavian vein)
the confluens of sinuses drains into the transverse sagittal sinus
At the jugular foramen, the sigmoid sinus becomes what?
the internal jugular vein
Where do cerebral vein runs?
on the surface of the brain (cerebral cortex) deep to the arachnoid mater
Rupture of a cerebral vein produces what?
bleeding into the subarachnoid space (deep to the arachnoid mater)
subarachnoid space contains CSF
-remember meninges have a rich innervation which will cause a headache
Subarachnoid hematomas can also be caused by what?
Berry aneurysms (weakness in the arterial wall of BV supplying the brain): wall is weakened and arterial pressure causes wall to balloon
What are the two common sites for berry aneurysms?
- junction of the anterior cerebral artery and the anterior communications
- junction of the middle cerebral and posterior communicating
arteries going in different directions causing turbulence are common place for aneurysms to occur
What do patients with subarachnoid hematomas experience?
“thunderclap” headache
Subarachnoid hematoma on CT
follow the contours of the outer surface of the brain
wil be shaped according to the parts in which the blood is forming
Subarachnoid hemorrhage can cause what other complication besides severe headaches?
- the patient can develop a COMMUNICATING hydrocephalus
- remember NONCOMMUNICATING hydrocephalus can develop from EPIDURAL hydrocephalus
- free flow of CSF from the choroid plexus to where it is reabsorbed; pressure of ALL ventricles of the brain will be elevated
The superior sagittal sinus is formed between what?
periosteum and dura mater
What veins go through the arachnoid mater to drain into the superior sagittal sinus?
cerebral veins (bridging veins)
What is the shaking baby syndrome?
Shearing of the CEREBRAL BRIDGING vein as they go from the surface of the cortex to terminate in the superior sagittal sinus
- bleeding into the SUBDURAL space forming a subdural hematoma
- shearing head trauma can produce a subdural hematoma by tearing bridging veins where they enter the superior sagittal sinus
How can you tell the difference between epidural (middle meningeal artery), subarachnoid (cerebral veins that run on surface of brain/berry aneurysms AKA Circle of Wilis), and subdural (cerebral bridging vein to superior sagittal sinus) hematoma?
by the shape of the hematoma itself
epidural: lens shaped
subarachnoid: enters sulci; follows the shape of the structures of the brain as blood surrounds the underlying brain
subdural: crescent shaped
Where does CSF drain?
- CSF drains into the superior sagittal sinus via arachnoid villi (granulations) to be reabsorbed back into the venous system.
- coming from the arachnoid mater, there are portions of it that herniate through into the superior sagittal sinus called arachnoid villi (granulations)
What is the function of arachnoid villi (granulations)?
the site where CSF is reabsorbed back into the vascular system
How does a subarachnoid hematoma lead to communicating hydrocephalus?
BLOOD HAS CLOTTING FACTORS that will go up into the villi and form a thrombus blocking the lumen of the villi and therefore there is no way for CSF to come back into the vascular system; thus develop elevated blood pressure in ALL of the brain ventricles (lateral, 3rd, cerebral aqueduct, 4th)
arachnoid villi can become calcified in the adult which would still block CSF absorption creating communicating hydrocephalus
Remember communicating hydrocephalus is when:
absorption(by arachnoid granulation/vili) < production (by the choroid plexus)
What does communicating hydrocephalus mean?
if CSF absorption (by granulations) is < production (by the choroid plexus)
What are the hematomas OUTSIDE of the brain that we’ve discussed?
epidural
subarachnoid
subdural
T/F. There can be hematomas inside the brain.
True!!
INTRAcranial hemorrhage can result in communicating hydrocephalus
the BLOOD can CUT through the BRAIN like a knife as it tries to drain into the ventricular system causing an enlargement of the stroke
When a person has a communicating hydrocephalus you produce Hakim’s triad which is?
classic symptoms a patient would present with if they have communicating hydrocephalus:
- ataxia particularly of the lower limb (cannot walk in a balanced/ coordinated fashion)
- dementia: problems with cognitive fxns
- urinary incontinence (leakage of the bladder)
OTHER symptoms include:
- headache
- papilledema
- nausea and vomiting
- sleeplessness or coma
Which part of the brain is the cavernous sinus (a dural sinus) found?
middle cranial fossa immediately lateral to the body of the sphenoid bone
Where does the cavernous sinus drain into?
the cavernous sinus drains into the transverse sinus via the superior petrosal sinus (which runs on top of the petrous bone)
Why is the cavernous sinus important?
-has a lot of connections with veins in the cranium and in the face
- its CONTENT:
- optic chiasma
- pituitary which sits directly behind the optic chiasma
- lateral wall of the sinus: oculomotor, trochlear, ophthalmic and maxillary nerves
- inside the sinus: internal carotid artery and abducens nerve; internal carotid plexus surrounding the internal carotid artery
What is the sigmoid sinus formed by?
the sigmoid sinus is formed by the union of the superior petrosal sinus and the transverse sinus
What is the internal carotid plexus?
- plexus of SYMPATHETIC nerve fibers that are post-ganglionic and coming from the superior cervical ganglion
- these nerve fibers are following the blood vessels up into the cranial vault to provide sympathetic innervation of control of the blood flow going through the blood vessels
What is the dangerous triangle of the face?
- area of the face where the venous drainage from the skin and underlying tissues and mucosa membranes; these veins have communications with the cavernous sinus!!!
- the communications are VALVELESS!!!
don’t pop your pimples!!!
Zit on nose; pop it and the infection can go various directions.
- can go through the facial vein (angular vein)
- superior ophthalmic vein to the cavernous sinus
- can go down through the facial vein and reach the pterygoid plexus reaching into the cavernous sinus
- or the infection can reach the inferior ophthalmic veins
T/F. All veins in the dangerous zone of the face have a communication with the cavernous sinus.
True!!
The pterygoid plexus and ophthalmic veins communicate with the cavernous sinus in the cranium.
What is cavernous sinus thrombophlebitis?
if you get an infections that spreads from the face to the cavernous sinus you can develop cavernous sinus thrombophlebitis
- can get clot forming swelling of a vein
- lose ability to look laterally (oculomotor and trochlear) AKA internal strabismus
- pupils could be fixed (constricted or dilated depending on what fiber are affected)
Emissary veins
- connect the scalp with the venous sinuses
- veins going from the scalp and face through the skull and can communicate with the sinuses in the skull
- are valveless so infection can go in either direction
- pathway in which infection can travel outside the cranium into the cranium producing meningitis or encephalitis
What is scaphocephaly?
premature closure of the sagittal suture
What is acrocephaly?
AKA Tower head/ Oxycephaly due to premature closure of the coronal suture and lambdoid suture (acorn shape)
Premature closure of sutures often occur in conjunction with what problems?
often occur in conjunction with other problems with the development of the face
What are symptoms of Albert’s syndrome (acrocephaly)?
Acrocephaly (Albert’s syndrome) is classified as a 1st branchial arch syndrome due to the premature fusion of skull and facial bones similar to Crouzon’s
- high forehead
- flat, sunken face
- shallow and wide orbits (eye)
- narrow, high palate
The trigeminal nerve does not go through a foramen but rather what?
goes through an invagination of the tentorium cerebelli known as the trigeminal cave (Meckel’s cave)
Which division of the trigeminal nerve is NOT found in the cavernous sinus?
mandibular division
thus if you have a cavernous sinus syndrome you may lose sensory sensation of the upper parts of the face but the territory of V3 will be spared
