RADSCI 242 - Cranium Exam

What are the three major divisions of the brain and what does each one do?

Cerebrum (higher functions: thinking, reasoning, movement), Cerebellum (coordination and balance), Brainstem (vital functions: heart rate, breathing, consciousness)

What is the function of the cerebrum?

Responsible for higher brain functions including thinking, reasoning, and voluntary movement

What is the function of the frontal lobe?

Decision-making, problem-solving, and planning

What is the function of the parietal lobe?

Processes sensory information related to touch, temperature, and pain

What is the function of the temporal lobe?

Important for memory, language, and emotion

What is the function of the occipital lobe?

Processes visual information

What is the cerebellum and what does it do?

Located below the cerebrum; responsible for balance, coordination, fine motor skills, motor learning, and timing of movements

What are the three parts of the brainstem and their functions?

Midbrain (vision, hearing, motor control), Pons (connects brain parts; controls sleep and respiration), Medulla Oblongata (regulates breathing and heart rate)

What are the four ventricles of the brain and where is each located?

Lateral ventricles (×2, one in each cerebral hemisphere), 3rd ventricle (between halves of the diencephalon), 4th ventricle (between brainstem and cerebellum)

What are the functions of cerebrospinal fluid (CSF)?

Cushions the brain, removes metabolic waste, and supplies nutrients

What is the choroid plexus and what does it do?

A network of cells and blood vessels located in the ventricles of the brain; it produces CSF

What is the blood-brain barrier (BBB) and how does it work?

A selective barrier that protects the brain by preventing harmful substances from entering brain tissue; allows passage of water, gases, lipid-soluble molecules, glucose, and amino acids

What are the three layers of the meninges from outermost to innermost?

Dura Mater → Arachnoid Mater → Pia Mater

What is the dura mater?

The tough outermost meningeal layer surrounding the brain and spinal cord

What is the arachnoid mater?

The web-like middle meningeal layer; contains the subarachnoid space filled with CSF

What is the pia mater?

The thin innermost meningeal layer that directly contacts and follows the surface of the brain

What is the epidural space and what does it contain?

The space between the skull and dura mater; contains fat and connective tissue

What is the subdural space and what does it contain?

The space between the dura mater and arachnoid mater; contains veins and arteries

What is the subarachnoid space and what does it contain?

The space between the arachnoid mater and pia mater; contains CSF and blood vessels

What are subarachnoid cisterns and what is their role?

Enlarged areas of the subarachnoid space where CSF pools around the brain; provide cushioning and house major blood vessels

What is the Circle of Willis and what is its function?

An arterial ring at the base of the brain that provides collateral circulation and helps maintain normal intracerebral pressure

What supplies the anterior vs. posterior blood to the brain?

Anterior: Internal Carotid Arteries | Posterior: Basilar Artery (via Vertebral Arteries)

What are the key components of the Circle of Willis?

Anterior Cerebral Arteries, Middle Cerebral Arteries, Posterior Cerebral Arteries, Anterior & Posterior Communicating Arteries

How many cranial bones and facial bones make up the skull?

8 cranial bones and 14 facial bones

What bones make up the calvarium (skull cap)?

Frontal bone, right and left Parietal bones, and Occipital bone

What bones make up the cranial floor?

Right and left Temporal bones, Sphenoid bone, and Ethmoid bone

What bones does the frontal bone articulate with?

Left and right Parietal bones, Sphenoid bone, and Ethmoid bone

What are the key landmarks of the frontal bone's squamous (vertical) portion?

Glabella, Supraorbital Groove (SOG), Supraorbital Margin (SOM), Supraorbital Notch (SON), and Frontal tuberosity

What bones do the parietal bones articulate with?

Frontal bone, Occipital bone, Temporal bone, Sphenoid bone, and the opposite Parietal bone

What is the significance of the parietal bones in skull anatomy?

They form the lateral walls and part of the roof of the cranium and represent the widest portion of the skull

What bones does the occipital bone articulate with?

Right and left Parietal bones, right and left Temporal bones, Sphenoid bone, and Atlas (C1)

What are the key features of the occipital bone?

Squamous portion, External Occipital Protuberance (Inion), Foramen Magnum, and Condylar portions that articulate with Atlas (C1)

What are the three primary parts of the temporal bone and what is each known for?

Squamous portion (flat lateral part), Mastoid portion (contains mastoid air cells), Petrous portion (houses organs of hearing and equilibrium)

What key structures are associated with the temporal bone?

Zygomatic Process, Zygomatic Arch, External Acoustic Meatus (EAM), TM fossa, TMJ, Jugular Foramen, Internal Acoustic Meatus

What surface landmark corresponds to the level of the petrous ridge?

Top of Ear Attachment (TEA)

What makes the sphenoid bone unique among the cranial bones?

It articulates with ALL 7 other cranial bones

What is the sella turcica and what does it house?

A saddle-shaped depression in the sphenoid bone that houses the pituitary gland

What is the dorsum sellae?

The posterior wall of the sella turcica

What projection best demonstrates the sella turcica?

True lateral projection

What foramina are found in the greater wings of the sphenoid?

Foramen Rotundum, Foramen Ovale, and Foramen Spinosum

What is the clivus and what does it support?

A part of the sphenoid bone that supports the pons and basilar artery

What is the cribriform plate of the ethmoid bone?

A horizontal plate with olfactory foramina that forms the roof of the nasal cavity

What is the crista galli and what is it an attachment for?

An upward projection of the ethmoid bone that serves as the attachment point for the falx cerebri

What does the perpendicular plate of the ethmoid bone form?

The superior portion of the nasal septum

What is the coronal suture and where is it located?

A fibrous joint between the frontal and parietal bones

What is the sagittal suture and where is it located?

A fibrous joint running between the two parietal bones along the top of the skull

What is the lambdoidal suture and where is it located?

A fibrous joint between the occipital and parietal bones

What is the squamosal suture and where is it located?

A fibrous joint between the temporal and parietal bones

What type of joint are cranial sutures and are they moveable?

Fibrous joints — Synarthrodial (immovable)

What is the bregma?

The bony point at the junction of the coronal and sagittal sutures

What is the lambda?

The bony point at the junction of the sagittal and lambdoidal sutures

What is the pterion?

The bony point at the junction of the frontal, parietal, temporal, and sphenoid bones

What is the asterion?

The bony point at the junction of the parietal, occipital, and temporal bones

What are fontanels and why do they exist?

Membrane-covered openings in the infant cranium where sutures have not yet fused ("soft spots"); allow for brain growth after birth

What are the six fontanels of the infant skull?

Anterior, Posterior, right and left Sphenoid, and right and left Mastoid fontanels

What is a mesocephalic skull and what are its measurements?

The average/most common head shape; width is 75–80% of length; petrous pyramids form a 47° angle

What is a brachycephalic skull?

A short/broad head shape where width is ≥80% of length and petrous pyramids form an angle greater than 47°

What is a dolichocephalic skull?

A long/narrow head shape where width is less than 75% of length and petrous pyramids form an angle less than 47°

What is the glabella?

The smooth bony prominence between the eyebrows on the frontal bone

What is the nasion?

The junction of the frontal and nasal bones; the bridge of the nose

What is the acanthion?

The point at the junction of the nose and upper lip

What is the mentum (mental point)?

The most inferior point of the mandibular symphysis (chin)

What is the gonion?

The angle of the mandible

What is the tragus?

The small cartilaginous projection in front of the External Acoustic Meatus (EAM)

What does the Top of Ear Attachment (TEA) correspond to internally?

The level of the petrous ridge of the temporal bone

What is the Glabellomeatal Line (GML)?

A cranial positioning line drawn from the glabella to the EAM

What is the Orbitomeatal Line (OML) and how does it relate to the GML?

A positioning line from the outer canthus to the EAM; it is approximately 7–8° below the GML

What is the Infraorbitomeatal Line (IOML) and how does it relate to the OML?

A positioning line from the infraorbital margin to the EAM; it is approximately 7–8° below the OML

What is the Glabelloalveolar Line (GAL) used for?

It is used as a reference line for lateral skull positioning alignment

What is the Interpupillary Line (IPL) used for in cranial positioning?

A line connecting the two pupils; used to check for tilt in the patient's head

What are the technical factors used for skull radiography?

Medium kVp (75–95), small focal spot, short exposure time, minimum 40" SID

What are the five common positioning errors in cranial radiography?

Rotation (MSP/GAL rotated), Tilt (MSP/GAL slanted), Excessive neck flexion, Excessive neck extension, Incorrect CR angle

What are the routine projections of the cranium series?

AP Axial (Towne Method), Lateral (bilateral), and PA Axial (Caldwell Method) or PA

What is the special projection of the cranium series?

Submentovertex (SMV)

What is the CR angle for the Towne Method when the OML is perpendicular to the IR?

30° caudal, centered 2.5" above the glabella

What is the CR angle for the Towne Method when the IOML is perpendicular to the IR?

37° caudal, centered 2.5" above the glabella

What anatomy is demonstrated on the AP Axial Towne projection?

Posterior clinoid process, foramen magnum, dorsum sellae, and petrous ridge

How do you know there is no rotation on a Towne projection?

The petrous ridges appear symmetric bilaterally

How do you know the CR angle and neck flexion are correct on a Towne projection?

The dorsum sellae and posterior clinoid processes are visible WITHIN the foramen magnum

What does it mean if the dorsum sellae appears SUPERIOR to the foramen magnum on a Towne projection?

Underangulation or insufficient neck flexion

What does it mean if the posterior arch of C1 is superimposed over the dorsum sellae on a Towne projection?

Overangulation or excessive neck flexion

What is the Haas Method and how does it differ from the Towne Method?

PA axial projection; nose and forehead against IR; 25° cephalic CR centered 1.5" inferior to inion; demonstrates same anatomy as Towne but produces more magnification

What is the CR location for the Lateral Skull projection?

2" superior to the EAM

What anatomy is demonstrated on a Lateral Skull projection?

Sella turcica, orbital plates, greater wings of sphenoid, anterior and posterior clinoid processes

How do you identify rotation on a Lateral Skull projection?

The greater wings of the sphenoid are NOT superimposed (correct = superimposed)

How do you identify tilt on a Lateral Skull projection?

The orbital plates are NOT superimposed (correct = superimposed)

How do you evaluate proper flexion on a Lateral Skull projection?

The GAL should be parallel to the edge of the IR

What is the CR angle and centering for the Caldwell Method (routine)?

15° caudal, centered at the nasion

What is the CR angle and centering for the Caldwell Method (alternative/steeper)?

25–30° caudal, centered at mid-orbit

What anatomy is demonstrated on the Caldwell projection?

Supraorbital Margin (SOM), petrous ridge, Infraorbital Margin (IOM), and midlateral orbital margin

What indicates correct CR angle on a Caldwell 15° projection?

Petrous ridges are projected into the lower ⅓ of the orbits

What additional anatomy is seen on a Caldwell 25–30° projection vs. 15°?

Foramen rotundum adjacent to IOM, superior orbital fissures within the orbits, petrous ridges at or just below IOM

What causes the petrous ridges to appear too low on a Caldwell projection?

Excessive tube angle or excessive neck extension

What causes the petrous ridges to appear too high on a Caldwell projection?

Insufficient tube angle or excessive neck flexion

How do you assess rotation on a Caldwell projection?

Equal distances from the midlateral orbital margins to the lateral cranium on both sides

What is the CR centering for the PA Skull (no angle)?

Centered at the glabella with no tube angle

What indicates correct positioning on a PA Skull projection?

Petrous ridges completely fill the orbits

What is the key difference between the PA Skull and PA Caldwell projection?

PA (no angle): petrous ridges fill the orbits | Caldwell (15°): petrous ridges are in the lower ⅓ of the orbits

How is the patient positioned for the SMV projection?

Neck hyperextended so the IOML is parallel to the IR; erect position preferred

Where is the CR centered for the SMV projection?

1.5" inferior to the mandibular symphysis, midway between the gonions; perpendicular to the IOML