Cranium RTEC 233 Fall 2008 Week 1 & 2

Cranial Anatomy Calvaria Floor Frontal Occipital Left Parietal Right Parietal Floor Ethmoid Sphenoid Left Temporal Right Temporal The skull is made of 22 separate bones. There are 8 cranial bones and 22 facial bones. The cranial bones are further divided in the calvaria and the floor. The calvaria consists of 1 frontal bone, 1 occipital bone, and left and right parietals. The floor consists of 1 ethmoid, 1 sphenoid and right and left temporals. The cranial bones serve as a protective housing for the brain. Why the 14 facial bones give structure and differentiating facial features for each individual person.

The regions of the Cranial Floor Anterior: extends form anterior frontal bone to the lesser wings of the sphenoid It is associated with frontal lobes of cerebellum Middle: Extends from lesser wings to the apices of petrous ridges of temporal bone Accommodates temporal lobes and associated neurovascular structures Posterior: deep depression posterior to petrous ridge which protects cerebellum, pons and medulla oblongata

Frontal Bone Has a vertical and horizontal portion Vertical portion- forms the forehead and anterior part of the vault Horizontal portion- forms roof of orbits, part of the roof of nasal cavity, and greater part of anterior cranial fossa.

Parietal Bone Forms large part of sides of the cranium Forms posterior portion of the cranial floor Parietal eminence is used to measure width of head

Occipital Bone Inferosuperior portion of calvaria Squamous portion is superior to inion Ext. occipital protuberance – prominent bulge Contains foramen magnum and articulates with atlas (C1)

Ethmoid Bone Horizontal portion is called cribiform plate Vertical portion is called perpendicular plate 2 light spongy labyrinths

Sphenoid Bone Resembles shape of a bat Consists of a body, 2 lesser wings, 2 greater wings, 2 pterygoid processes Contains Sella turcica- important for positioning errors

Sella Turcica Lies in the MSP ¾” anterior & superior to EAM Deformity of the sella is often the only clue that a lesion exists intracranially

Temporal Bone Divided in 3 parts Squamous: upper portion forming part of the wall of skull Mastoid: Posterior to EAM contains mastoid tip (process) Petrous: dense & houses organs of hearing and balance Thickest most dense bone in cranium Level of TEA

Superior Cranium Visualized more clearly: Not well visualized: Sphenoid Temporals Occipital Frontal Not well visualized: Ethmoid Parietals Copyright © 2003, Mosby, Inc.

From this view you can visualize all the cranial bones Lateral Cranium From this view you can visualize all the cranial bones Copyright © 2003, Mosby, Inc.

Infant Sutures & Fontanels Anterior Close approx 2 years 2 Mastoids 2 Sphenoidal 1-3 months old Posterior 1-3 months In a newborn child the bones of the cranium are thin. At this time the cranium is not fully developed and contains small amounts of calcium. There are 6 areas in which the bones are not completely developed and ossified called fontanels. The anterior fontanel is located at the junction of the two parietal bones and the frontal bone. Where the occipital bone, parietal bone and mastoid portion of the temporal bone meet is where the mastoid fontanels are located (one on each side of the head. The place where the parietal bone, squamosal suture and greater wing of the sphenoid meet is at the sphenoidal fontanel. The posterior fontanel is located where the lamboidal and sagittal sutures meet. The anterior and mastoid fontanels close in the 2nd year of life, while the sphenoidal and posterior fontanels close in the first 1-3 months of life. Copyright © 2003, Mosby, Inc.

Adult Sutures and Junctions Coronal Sagittal Squamosal Lamboidal Junctions Bregma Lambda Pterion Asterion The coronal suture is found between the parietals and frontal bone. The sagittal suture is located on top of the head just between the two parietals posterior to the coronal suture. The squamosal suture is located between the temporal and parietal bones. The lamboidal suture is located between the occipital bone and the parietal bones. The bregma is where the coronal and sagittal sutures meet. The lambda is where the lamboidal and sagittal sutures meet. The pterion is where the parietal bone, squamosal suture and greater wing of the sphenoid meet. The asterion is where the occipital bone, parietal bone and mastoid portion of the temporal bone meet. Copyright © 2003, Mosby, Inc.

Lets compare Infant Adult Anterior fontanel Posterior fontanel Sphenoidal fontanels Mastoidal fontanels Adult Bregma Lambda Pterions Asterions

Anterior Cranium Not able to visualize: Able to visualize: Occipital Ethmoid Able to visualize: Parietals Frontal Sphenoid Temporals Copyright © 2003, Mosby, Inc.

Cranial Topography

Surface Landmarks

Skull morphology Mesocephalic: average Brachycephalic: Short and broad 47 degrees Brachycephalic: Short and broad Width 80% or greater than length 54 degrees Dolichocephalic: long and narrow Width is less than 75% than the length 40 degrees Skull morphology

Skull Positioning Lines

Skull Topography Be able to locate the following landmarks: Gonion Mental point External auditory meatus (EAM) Auricular point Top of ear attachment (TEA) Glabella Inner canthus Outer canthus Nasion Infraorbital margin Acanthion

Radiographic Landmarks Interpupillary line (IPL) Perpendicular line between pupils of eyes Acanthiomeatal line (AML) From acanthion to EAM Mentomeatal line (MML) From mental point (center of chin) to EAM

Radiographic Landmarks Orbitomeatal line (OML) From outer canthus to EAM Infraorbitomeatal line (IOML) From infraorbital margin to EAM Glabellomeatal line (GML) From glabella to EAM

Positioning Aids Use any straightedge: Straw Pen/pencil

Most Common Positioning Errors Rotation Tilt Excessive Flexion Excessive Extension Incorrect CR angle Rotation Rotation and tilt are the two most common errors that cause a repeat. Rotation is when the MSP is rotated and not parallel to the grid device or IR. In a lateral position this means that the MSP is parallel to the IR. Tilt is when the MSP is slanted or tilted not parallel with the grid device or IR. In the lateral projection there is tipping or slanting of the MSP laterally. Flexion and extension errors can be made by lowered or elevating the chin too much or too little. Many projections is skull radiography are very similar such as Waters, Lateral and Caldwell. The positioning for each projection is very similar and often it is the CR angle that makes the projection different. There are different CR angles for Caldwell projections depending on the area of interest. Tilt Copyright © 2005, Mosby, Inc.

Indications for Cranial Radiography Skull fractures Linear Depressed Basal skull Gunshot wounds Pituitary Adenomas Subdural hematoma Neoplasms Metastases Osteolytic Osteoblastic Combo of both Multiple myeloma Paget’s Disease Acoustic neuroma Indications for skull radiography has decreased because of more new technology such as CT and MRI. Although skull radiography is great for spatial resolution of bone it is not indicative of a brain injury. Additional modalities such as MRI and CT are used to assess brain tissue injury. Linear fractures are FX’s of the skull that appear jagged or irregular lines. Depressed fractures are sometimes called ping pong FX’s. A piece of fragmented bone that is separated and depressed into the cranial cavity. Basal skull FX are fractures seen through the denser structures of the temporal bone. These are very difficult to see because of the complex anatomy in the temporal region. If there is bleeding in this area sometimes an air-fluid level can been seen in the sphenoidal sinus if a horizontal beam is used for the lateral view. Gunshot wounds are usually used to localize bullets and bullet fragments. They are done antemortem and postmortem. Pituitary adenomas are tumors of the pituitary gland. Usually any findings of this disease is indicated by an enlarged sella turcica and erosion of the dorsum sellae. But more often than not, this is an incidental finding, if they are suspected of having this disease a CT or MRI are usually performed. Subdural hematoma: is an accumulation of blood in the subdural space due to injury of the head. Often occurs with a strong blow to the cranium, causing cortical or bridging veins surrounding the subdural space to tear. Neoplasms are new and abnormal growths. A metastatic neoplasms is one that is spread through blood and the lymphatic system. The skull is a common site for metastatic lesions. Metastatic lesions are characterized and visualized on the image as follows: Osteolytic- destructive lesions with irregular margins Osteoblastic- are proliferative bony lesions of increased density Combo- have a moth-eaten or cotton ball appearance because of the mix of osteolytic and osteoblastic lesions. Multiple myeloma consists of 1 or more bone tumors that originate in the bone marrow causing destruction of the bone. Paget’s disease is a disease of unknown origin that is marked by a stage of bone destruction followed by a bony repair. It involves many bony sites and skull is a common site. In the destructive phase there are many areas of lucency in a cotton wool appearance. Then there are areas of increased density (sclerosis) when in the reparative stage. Acoustic neuroma: a benign tumor arising from the Schwann cells of the 8th cranial nerve.

http://www.skullbaseinstitute.com/video_pituitary_tumor.htm http://www.skullbaseinstitute.com/video_acoustic_neuroma.htm

Disinfect the Table or Bucky!!

Cleanliness Hair and skin of face are naturally oily; illness often increases oiliness Cranial procedures require direct contact of patient’s face with VBS Clean device after each patient Wash your hands!!!

Radiation Protection Collimate to anatomy of interest Shield gonads/abdomen of pediatric patients and those of reproductive age Shield thyroid and thymus of pediatric patient when doing so will not interfere with demonstration of anatomy of interest Good communication and positioning skills reduce chance of need for repeat radiographs

General Body Position Hyposthenic/asthenic patients usually need support at chest to elevate C-spine Helps prevent downward tilt of MSP Hypersthenic patients require radiolucent support at head Helps prevent upward tilt of MSP

Hyposthenic/Asthenic Patients

Hypersthenic Patients

Positioning: Lateral Skull Seated upright or semi-prone MSP is parallel to IR Interpupillary line is perpendicular to IR Suspend respiration CR enters 2” superior to EAM Copyright © 2003, Mosby, Inc.

Positioning Trauma Lateral Skull Supine with sponge under head MSP is parallel to IR Interpupillary line is perpendicular to IR Suspend respiration CR enters 2” superior to EAM Copyright © 2003, Mosby, Inc.

Lateral Skull

Lateral Skull Radiograph Entire cranium without rotation/tilt SI orbital roofs, greater wings of sphenoid, and TMJ’s Sella turcica in profile Penetration of parietal No overlap c-spine by mandible Rotation would be evident by an ANTERIOR and POSTERIOR separation of symmetric bilateral structures such as EAM”S, mandibular rami,and greater wings of the sphenoid. Tilt would be evident by SUPERIOR and INFERIOR separation of the orbital roodfs, EAM’s and lesser wings of sphenoid. Side of interest closest to cassette. MSP is parallel to IR. IOML is perpendicular to the front edge of IR and IOML should be parallel to the long axis of the IR. CR enters 2” superior to the EAM. Pathology of interest for this projection usually includes: skull fractures, neoplastic processes and Paget’s disease. Copyright © 2003, Mosby, Inc.

Common PA projections O degree- Frontal bone, crista galli, internal auditory canals, frontal and anterior ethmoidal sinuses, petrous ridges, greater and lesser wings of sphenoid, and dorsum sellae. 15 degree caudal, commonly referred to as the Caldwell projection, demonstrates greater and lesser sphenoid wings, frontal bone, superior orbital fissures, frontal and anterior ethmoidal air sinuses, superior orbital margins and crista galli. 25-30 caudal demonstrates the same as the Caldwell and the following additional structures: the foramen rotundum, and the entire superior orbital fissures located within the orbits.

Positioning PA, PA Axial & Caldwell Prone or seated upright Forehead and nose against bucky or table OML perpendicular to IR MSP perpendicular to IR Respiration: suspend CR: 0, 15 caudal or 25-30 caudal, exiting nasion Copyright © 2003, Mosby, Inc.

Trauma PA and PA Axial Skull Semi supine: 1 side elevated to place head in true lateral Sponge under head Nose and forehead against vertical IR OML perpendicular to IR Direct horizontal CR perpendicular or 15 degrees caudad to exit nasion Copyright © 2003, Mosby, Inc.

PA and Caldwell Radiographs Entire skull with no rotation or tilt Petrous ridges in lower 1/3 of orbits with 15 caudal Petrous ridges fill orbits with horizontal beam Density and contrast are sufficient No motion Nasion in center of film, close collimation No rotation is evident by assessing that there is equal distance from lateral border of skull to lateral border of orbits on each side. Superior orbital fissures symmetric within orbits. Density and contrast are sufficient to visualize the frontal bone, and sellar structures without overexposure. Sharp bony detail indicates no motion. Copyright © 2003, Mosby, Inc.

Similarities and Differences Exit nasion Require close collimation OML is perpendicular to plane of IR All axials have caudal angles Respiration suspended Position of petrous ridges Best seen Body position Where the CR enters All PA and PA AXials exit nasion. All require close collimation so that that scatter does not degrade the image and cause the lateral borders to have excessive density. All axial projections the CR is projected caudally. All projections respiration is suspended for exposure. The petrous ridges are filling the orbits for a PA, in lower 1/3 for 15 degrees caudal. What is best seen changes based on the CR angulation. The position of the body changes whether they are semi-supine, prone, or upright. The CR will have to enter the body differently so the CR always exits the nasion.

Positioning: AP & AP Axial Skull Supine OML perpendicular to IR CR directed at nasion with a horizontal beam or 15 degrees cephalic Suspend respiration

AP Skull Radiograph Entire skull with no rotation or tilt Petrous ridges in lower 1/3 of orbits with 15 cephalad Petrous ridges fill orbits with horizontal beam Density and contrast are sufficient No motion Nasion in center of film, close collimation Image is magnified compared to PA Copyright © 2003, Mosby, Inc.

Positioning AP Axial (Towne) Supine or seated upright MSP perpendicular to plane of IR OML or IOML perpendicular to IR Suspend respiration CR 30 degrees caudal (OML) or 37 caudal (IOML). CR enters 2 ½” above glabella through the level of EAM Copyright © 2003, Mosby, Inc.

AP Axial (Towne) Radiograph Equal distance from lateral border of skull to foramen magnum Symmetric petrous ridges Dorsum sellae and posterior clinoid processes visible through foramen magnum Penetration of occipital bone without excessive density

Sella Turcica

Townes Comparison

Positioning PA Axial (Haas) Prone or seated upright Forehead and nose on table or grid device MSP perpendicular to the grid OML perpendicular to IR Suspend respiration CR 25 degrees cephalad entering 1 1/2 “ below occipital protuberance. R exits 1 ½” superior to nasion

PA Axial (Haas) Radiograph Prone or seated upright MSP & OML perpendicular Suspend respiration Directed cephalic 25 degrees to enter 1 ½” below the inion. Exit 1 ½” superior to nasion. Copyright © 2003, Mosby, Inc.

Haas PA Axial

Positioning SMV (Schüller) Supine or seated upright IOML parallel to IR MSP perpendicular to IR Suspend respiration CR enters the MSP of the throat between angles of mandible and passes through a point ¾”anterior to EAMS.

SMV (Schüller) Radiograph Adequate penetration of cranial base Equal distance from lateral border of skull to condyles SI of mental protuberance over anterior frontal bone Condlyes anterior to petrous ridges Symmetric petrosae

Positioning VSM (Schüller) Prone Chin resting on table MSP perpendicular to IR Suspend respiration CR directed perpendicular to IOML. CR passes through ¾” anterior to level of EAMS

VSM (Schüller) Radiograph Adequate penetration of cranial base Equal distance from lateral border of skull to condyles SI of mental protuberance over anterior frontal bone Condlyes anterior to petrous ridges Symmetric petrosae

SMV

What is wrong with this Caldwell?

What is wrong with this lateral skull?

What is wrong with this Towne’s?