Chapter 17 - Skull, Facial Bones, and Paranasal Sinuses

Question 1

skull

Answer 1

The skull consists of 22 bones. It is divided into the cranium, which protects the brain, and the facial bones, which provide the facial structure.

Question 2

calvaria

Answer 2

The portion of the cranium on which the base of the brain rests is the floor and the remainder that surrounds the brain

Question 3

The cranium consists of eight bones:

Answer 3

frontal, occipital, right and left parietal, right and left temporal, sphenoid, and ethmoid

Question 4

glabella

Answer 4

The bony prominence on the frontal bone between the eyebrows is a palpable positioning landmark

Question 5

external occipital protuberance

Answer 5

The occipital bone is at the lower part of the back of the skull and also forms the posterior portion of the cranial floor or base. In the approximate center on the outer surface of the occipital bone is a palpable bony prominence

Question 6

foramen magnum

Answer 6

The large round hole in the anterior portion of the occipital bone. It is the passage for the spinal cord between the skull and the spine.

Question 7

sella turcica

Answer 7

The rounded fossa in the center of the anterosuperior surface of the sphenoid bone, is the location of the pituitary gland.

Question 8

external auditory meatus, also called the external acoustic meatus

Answer 8

The EAM is the opening to the ear canal and is an important positioning landmark.

Question 9

petrous portion

Answer 9

Extending medially from the EAM area is a dense pyramid of bone, which contains the middle and inner ear structures.

Question 10

mastoid portion of the temporal bone

Answer 10

contains many small air cells, and the mastoid process is palpable just posterior to the earlobe.

Question 11

zygomatic arch

Answer 11

zygomatic process articulates anteriorly with the zygomatic (cheek) bone to form the zygomatic arch.

Question 12

sutures

Answer 12

The joints that connect the bones of the cranium are synarthrodial (immovable) joints

Question 13

sagittal suture

Answer 13

The parietal bones are joined

Question 14

coronal suture

Answer 14

Between the frontal bone and the parietal bones

Question 15

lambdoidal suture

Answer 15

Between the parietal bones and the occipital bone

Question 16

squamosal suture

Answer 16

The joint that joins the parietal and temporal bones

Question 17

The palpable bones of the face include

Answer 17

the maxilla, mandible (jaw), zygomas (cheek bones), and nasal bones

Question 18

maxilla

Answer 18

The maxilla is the largest immovable bone of the face and articulates with all of the other facial bones except the mandible.

Question 19

acanthion

Answer 19

This point, located at the junction of the nose and the upper lip, is a positioning landmark

Question 20

mandible

Answer 20

The mandible, or jaw, is the only movable bone of the face.

Question 21

mental protuberance or mental point

Answer 21

The prominence in the center of the mandible’s lower margin

Question 22

gonion

Answer 22

the angle of the mandible, and is a common positioning landmark.

Question 23

temporomandibular joint

Answer 23

The formation of the rounded projection on the superoposterior ramus, the mandibular condyle, articulates with the mandibular fossa of the temporal bone

Question 24

Seven small bones of the bony structure of the face:

Answer 24

the vomer, two palatine bones, two inferior nasal conchae, and two lacrimal bones.

Question 25

Three pairs of nasal conchae:

Answer 25

superior, middle, and inferior—are thin curved bony projections that divide the nasal cavity, forming air passages lined with mucous membrane. The superior and middle conchae are projections of the ethmoid bone. The inferior conchae are separate bones that articulate with the maxilla on either side.

Question 26

paranasal sinuses

Answer 26

air-filled cavities within the ethmoid, frontal, and sphenoid bones and within the maxilla (Fig. 17.5). They serve as resonating chambers for the voice and help to warm and moisten inhaled air. The sinuses develop during childhood and are not fully formed until age 16 to 18. At maturity, passages connect the sinuses to each other and to the nasal cavity.

Question 27

maxillary sinuses

Answer 27

also called the maxillary antra or the antra of Highmore. They are the largest paranasal sinuses and are located within the body of the maxilla on either side of the nasal cavity.

Question 28

frontal sinuses

Answer 28

the second largest paranasal sinuses and are located in the anterior frontal bone, superior to the nasal cavity. They are divided by a central septum into right and left compartments and are usually further subdivided. They are not symmetric and may vary greatly in size and shape. Absence of frontal sinuses is a normal variant.

Question 29

sphenoidal sinuses

Answer 29

occupy most of the body of the sphenoid bone and are located immediately inferior to the sella turcica. Although they normally occur as a pair of chambers, it is not unusual for only a single chamber to be present.

Question 30

two ethmoidal sinuses

Answer 30

located within the lateral masses of the ethmoid bone and consist of a varying number of small air cells. They are situated between and behind the orbits and anterior to the sphenoid sinuses.

Question 31

nasal septum

Answer 31

The vomer is posterior to the acanthion at the floor of the nasal cavity. It forms the inferior portion of the nasal septum, the wall that divides the nasal cavity.

Question 32

hard palate or roof of the mouth

Answer 32

The two palatine bones together with the maxilla

Question 33

nasion

Answer 33

the anterior depression in the midline of the skull between the orbits.

Question 34

three body planes:

Answer 34

coronal, sagittal, and transverse

The coronal and sagittal planes are adjusted by body position and rotation of the head. The transverse plane alignment depends on the flexion or extension of the neck.

Question 35

Angligner

Answer 35

a tool to determine the alignment between body planes or positioning lines and the image receptor (IR) plane,

Question 36

Skull - PA

Answer 36

Body position

Prone or seated facing upright Bucky.

Tip

When the prone patient crosses the arms under the chest, this elevation of the thorax allows greater flexion of the neck; it facilitates accurate positioning and relieves pressure on the nose.

Part position

Sagittal plane of skull is perpendicular to center of IR, with forehead and nose resting on table or against upright Bucky. Neck flexion adjusted to place OML perpendicular to IR (Fig. 17.8).

Central ray

Perpendicular to center of IR through nasion.

Structures seen

Frontal bone and outer contours of cranium from frontal perspective. When perpendicular central ray is used, petrous pyramids are projected within orbits (Fig. 17.9).

Question 37

Skull - PA axial (Caldwell method)

Answer 37

Body position

Prone or seated facing upright Bucky.

Tip

When the prone patient crosses the arms under the chest, this elevation of the thorax allows greater flexion of the neck; it facilitates accurate positioning and relieves pressure on the nose.

Part position

Sagittal plane of skull is perpendicular to center of IR, with forehead and nose resting on table or against upright Bucky. Neck flexion adjusted to place OML perpendicular to IR (Fig. 17.8).

Central ray

Angled 15 degrees caudad to center of IR through nasion (Fig. 17.10).

Structures seen

When a 15-degree caudad angle with the Caldwell method is used, petrous pyramids are projected through the lower third of the orbit and the orbital margins are more clearly demonstrated (Fig. 17.11).

Question 38

Skull - Ap Axial Projection (Towne Method)

Answer 38

Body position

Supine or seated.

Part position

Sagittal plane of skull is perpendicular to IR with back of head resting on table or against upright Bucky. Neck flexion adjusted to place OML perpendicular to IR (Fig. 17.12).

Tip

If patient is unable to flex neck sufficiently to get OML perpendicular to IR, placement of a wedge sponge under the head may assist in attaining the correct position.

Central ray

Angled 30 degrees caudad to center of IR through the foramen magnum at the level of the EAM. Central ray enters skull in midsagittal plane, approximately 2.5 inches superior to the glabella.

Tip

If the patient is unable to flex the neck sufficiently to get the OML perpendicular to the IR, the IOML can be placed perpendicular and the central ray angled 37 degrees caudad.

Structures seen

Occipital bone, posterior parietal bones, foramen magnum, and petrous portions of temporal bones (Fig. 17.13)

Question 39

Skull - Lateral Projection

Answer 39

Body position

Recumbent or seated in an anterior oblique body position with side of interest nearest IR (Fig. 17.14).

Part position

Sagittal plane of head is parallel to IR and interpupillary line is perpendicular to it (Fig. 17.15). Support under mandible may assist in maintaining this position. Neck flexion is adjusted to place the IOML parallel to the long axis of the IR.

Central ray

Perpendicular to center of IR through a point approximately 2 inches superior to the EAM.

Structures seen

Lateral image of entire cranium. Sella turcica is seen in profile. There should be no rotation or tilt of the cranium, and paired structures should be superimposed (Fig. 17.16). The side nearest the IR is most clearly seen.

Question 40

Skull - AP

When obesity or injury makes it difficult to position the patient prone, an AP projection may be substituted for the PA or PA axial (Caldwell method) projection. Radiation dose to the eyes and thyroid gland is increased compared with the PA projections.

Answer 40

Body position

Supine or seated.

Part position

Sagittal plane of the skull is perpendicular to the IR with back of head resting on table or against upright Bucky. Neck flexion is adjusted to place the OML perpendicular to the IR (Fig. 17.17).

Tip

If the patient is unable to flex the neck sufficiently to get the OML perpendicular to the IR, placement of a wedge sponge under the head may assist in maintaining the correct position.

Central ray

Perpendicular to the center of the IR through the nasion.

Structures seen

Frontal bone and outer contours of the cranium from a frontal perspective. When a perpendicular central ray is used, petrous pyramids are projected within the orbits (Fig. 17.18).

Question 41

Skull - AP AXIAL (“REVERSE” CALDWELL METHOD)

Answer 41

Body position

Supine or seated.

Part position

Sagittal plane of the skull is perpendicular to the IR with back of head resting on table or against upright Bucky. Neck flexion is adjusted to place the OML perpendicular to the IR (Fig. 17.17).

Tip

If the patient is unable to flex the neck sufficiently to get the OML perpendicular to the IR, placement of a wedge sponge under the head may assist in maintaining the correct position.

Central ray

Angled 15 degrees cephalad through nasion.

Structures seen

With the “reverse” Caldwell method, using a 15-degree cephalad angle, petrous pyramids are projected through the lower third of the orbit and the orbital margins are more clearly demonstrated. The orbits and other anterior structures are magnified in comparison with PA projections.

Question 42

Skull - Pa Axial Projection (Haas Method)

The PA axial projection (Haas method) may be used instead of the AP axial projection (Towne method). The Haas method is useful when obesity or exaggerated kyphosis of the thoracic spine makes it difficult for the patient to assume a supine position with the OML perpendicular to the IR or nearly so. Both the patient position and the tube angle are reversed. The resulting radiograph is similar to the AP axial projection (Towne method), but detail of the posterior structures is somewhat compromised because of the increased object–image receptor distance (OID).

Answer 42

Body position

Prone or seated facing IR.

Part position

Sagittal plane of skull is perpendicular to IR with forehead and nose resting on table or against upright Bucky. Neck flexion is adjusted to place OML perpendicular to IR (Fig. 17.19).

Central ray

Angled 25 degrees cephalad to center of IR through a point 1.5 inches below external occipital protuberance. Central ray exits skull in midsagittal plane at location approximately 1.5 inches superior to nasion.

Structures seen

Occipital bone, posterior parietal bones, foramen magnum, and petrous portions of the temporal bones (Fig. 17.20).

Question 43

Skull - SUBMENTOVERTICAL PROJECTION

The submentovertical projection is added to the routine examination when it is desired to demonstrate the structures of the cranial base more completely than they are seen with the Towne method. It is especially helpful for demonstration of the sphenoid bone and the cranial foramina.

Answer 43

Body position

Supine with shoulders and thorax elevated and supported to place top of head against table or seated with back to IR and back arched to place top of head against upright Bucky.

Part position

The sagittal plane of head is perpendicular to the IR. The neck is extended as much as possible with the head resting on its vertex. Neck extension is adjusted to place the IOML parallel to the IR or as near parallel as possible (Fig. 17.21).

Central ray

Perpendicular to IOML through midline and passing through a point 0.75 inches anterior to the level of the EAM.

Structures seen

Cranial base, including the occipital bone, foramen magnum, sphenoid and ethmoid bones, and petrous portions of temporal bone (Fig. 17.22). Foramina ovale and spinosum are also demonstrated on this projection.

Question 44

Facial Bones - Pa Axial Projection (Caldwell Method)

Answer 44

Body position

Prone or seated facing upright Bucky.

Tip

When the prone patient crosses the arms under the chest, this elevation of the thorax allows greater flexion of the neck; it facilitates accurate positioning and relieves pressure on the nose.

Part position

Sagittal plane of skull is perpendicular to center of IR, with forehead and nose resting on table or against upright Bucky. Neck flexion adjusted to place OML perpendicular to IR (Fig. 17.8).

Central ray

Angled 15 degrees caudad to center of IR through nasion (Fig. 17.10).

Structures seen

Orbits, zygomatic bones, maxilla, nasal septum, and a portion of the mandible (Fig. 17.23). The petrous ridges are projected into the lower third of the orbits.

Question 45

Facial Bones - Parietoacanthial Projection (Waters Method)

Answer 45

Body position

Standing, seated, or recumbent, facing IR.

Part position

The neck is extended with the chin resting on the table or upright Bucky. Neck flexion is adjusted so that the MML is perpendicular to the IR and the OML forms a 37-degree angle to the IR (Fig. 17.24). The sagittal plane is perpendicular to the IR.

Tip

When the patient is correctly positioned, the distance between the table or upright Bucky and the tip of the nose should be about 0.75 inches, or the width of the index finger.

Central ray

Perpendicular to the IR to exit at the acanthion.

Note

Should be done upright with a horizontal beam to show air-fluid levels.

Structures seen

Maxilla, orbits, zygomatic arches, and nasal septum (Fig. 17.25).

Tip

The petrous portion of the temporal bone should be projected beneath the maxillary sinus. If it is superimposed over the floor of the sinus, a greater degree of neck extension is necessary.

Question 46

Facial Bones - Lateral

Answer 46

Body position

Recumbent or seated in an anterior oblique body position with side of interest nearest IR (Fig. 17.14).

Part position

Sagittal plane of head is parallel to IR and interpupillary line is perpendicular to it (Fig. 17.15). Support under mandible may assist in maintaining this position. Neck flexion is adjusted to place the IOML parallel to the long axis of the IR.

Central ray

Perpendicular to the center of the IR through a point approximately halfway between the outer canthus and the EAM (Fig. 17.26).

Structures seen

Lateral image of all facial bones, with superimposition of paired bones (Fig. 17.27).

Question 47

Facial Bones - VERTICOSUBMENTAL PROJECTION OF ZYGOMATIC ARCHES

The zygomatic arches are seen on the submentovertical projection of the skull. Alternatively, the position may be reversed to provide a verticosubmental projection.

Answer 47

Body position

Prone or seated facing IR.

Part position

The neck is extended with the chin resting on the table or upright Bucky. Neck flexion is adjusted to place the IOML nearly parallel to the IR (Fig. 17.28). The sagittal plane is perpendicular to the IR.

Central ray

Angled caudad, perpendicular to the IOML and passing through the midsagittal plane 1.5 inches posterior to the level of the outer canthus.

Structures seen

Zygomatic arches free of superimposition (Fig. 17.29).

Question 48

Lateral Projection Of Nasal Bones

The nasal bones are very thin, so exposure factors similar to those used for a finger are used. Both lateral projections may be performed on a single IR because these are paired bones.

Answer 48

Body position

Same as for cranium and facial bones.

Part position

Same as for cranium and facial bones (Fig. 17.30).

Central ray

Perpendicular to IR to midpoint of nasal bone.

Structures seen

Lateral image of the nasal bone closest to the IR, the anterior nasal spine, and associated soft tissue (Fig. 17.31). Both lateral projections are usually taken.

Question 49

Paranasal Sinuses - PA axial (Caldwell method)

Answer 49

Body position

Prone or seated facing upright Bucky.

Tip

When the prone patient crosses the arms under the chest, this elevation of the thorax allows greater flexion of the neck; it facilitates accurate positioning and relieves pressure on the nose.

Part position

Extend the patient’s neck, with the tip of the nose touching the IR and the nasion centered to the IR. Position the patient’s head so the OML forms a 15-degree angle with the horizontal central ray. A radiolucent sponge may be placed between the forehead and grid to provide support (Fig. 17.38).

Central ray

Directed horizontal to exit the nasion.

Structures seen

Frontal and ethmoid sinuses (Fig. 17.39).

Question 50

Paranasal Sinuses - parietoacanthial (Waters method)

Answer 50

Body position

Standing, seated, or recumbent, facing IR.

Part position

The neck is extended with the chin resting on the table or upright Bucky. Neck flexion is adjusted so that the MML is perpendicular to the IR and the OML forms a 37-degree angle to the IR (Fig. 17.24). The sagittal plane is perpendicular to the IR.

Tip

When the patient is correctly positioned, the distance between the table or upright Bucky and the tip of the nose should be about 0.75 inches, or the width of the index finger.

Central ray

Perpendicular to the IR to exit at the acanthion.

Note

Should be done upright with a horizontal beam to show air-fluid levels.

Structures seen

It demonstrates the maxillary and ethmoid sinuses (Fig. 17.41).

Question 51

Paranasal Sinuses - Lateral

Answer 51

Body position

Recumbent or seated in an anterior oblique body position with side of interest nearest IR (Fig. 17.14).

Part position

Sagittal plane of head is parallel to IR and interpupillary line is perpendicular to it (Fig. 17.15). Support under mandible may assist in maintaining this position. Neck flexion is adjusted to place the IOML parallel to the long axis of the IR.

Central ray

Perpendicular to the center of the IR through a point approximately halfway between the outer canthus and the EAM (Fig. 17.26).

Structures seen

demonstrates all of the paranasal sinuses, with right and left chambers superimposed on each other (Fig. 17.43).

Question 52

Paranasal Sinuses - submentovertical projection

Answer 52

Body position

Supine with shoulders and thorax elevated and supported to place top of head against table or seated with back to IR and back arched to place top of head against upright Bucky.

Part position

The sagittal plane of head is perpendicular to the IR. The neck is extended as much as possible with the head resting on its vertex. Neck extension is adjusted to place the IOML parallel to the IR or as near parallel as possible (Fig. 17.21).

Central ray

Perpendicular to IOML through midline and passing through a point 0.75 inches anterior to the level of the EAM.

Structures seen

demonstrates the sphenoid and ethmoid sinuses (Fig. 17.45).

Question 53

cerebral concussion

Answer 53

A blow to the head that causes brief unconsciousness or disorientation, sometimes described as “seeing stars,”

Question 54

contrecoup injury

Answer 54

A severe blow to the head may cause the brain to move within the cranium, producing brain injury on the side opposite the location of the blow.

Question 55

most common facial fracture

Answer 55

The most common facial fracture is that of the nasal bones.

Question 56

transverse fracture of both nasal bones

Answer 56

The typical fracture caused by a blow to the nose

Question 57

blowout fracture

Answer 57

Fracture of the orbital floor. Bone fragments and soft tissues of the eye are forced into the maxillary sinus.

Question 58

mandible fractures

Answer 58

The structure of the mandible is such that sufficient force to cause a fracture in one area causes a wrenching stress in other portions of the bone.
often occur in pairs

Question 59

multiple myeloma

Answer 59

a malignant bone disease that may involve many bones of the body.

Question 60

Tumors within the brain

Answer 60

usually diagnosed by means of CT or magnetic resonance imaging (MRI) scans. Tumors that affect the bones of the cranium, however, may be evaluated by radiography.

Question 61

four sets of paranasal sinuses

Answer 61

maxillary, frontal, ethmoid, and sphenoid

Question 62

The routine examination of the cranium includes

Answer 62

the PA or PA axial (Caldwell method), AP axial (Towne method), and lateral projections.

Question 63

The routine examination of the facial bones includes

Answer 63

the PA axial (Caldwell method), parietoacanthial (Waters method), and lateral projections.

Question 64

The routine examination of the mandible includes

Answer 64

the PA, lateral, and axiolateral projections. It also may include AP axial projection for mandibular condyles and temporomandibular joints.

Question 65

The routine examination of the paranasal sinuses includes

Answer 65

the PA axial (Caldwell method), parietoacanthial (Waters method), lateral, and submentovertical projections. It is important that all projections be done upright to demonstrate air-fluid levels if they are present.