Intro to the Skull

Question 1

What is the spot on the side of the head called that is thin, and if struck, could result in a rupture in the middle meningeal artery –> epidural hematoma?

Answer 1

The pterion

Question 2

Name three big differences between an infant skull and an adult skull.

Answer 2

1. Cranial sutures are not fused; they are bridged over by membranes, allowing for deformation during birth and brain enlargement.
2. Mandible is small.
3. Mastoid process is absent.

Question 3

What causes newborns to have “coneheads?”

Answer 3

Tight birth canal.

Question 4

What is craniosynostosis? What is the treatment?

Answer 4

Premature closure of the cranial sutures (usually happens by age 2), results in increased intracranial pressure, possibly developmental delays. Surgery is required to separate the sutures.

Question 5

What happens if the metopic suture closes prematurely?

Answer 5

A metopic ridge might develop down the middle of the forehead (or it could be deviated laterally to one side or the other).

Question 6

What type of skull fracture would cause bruising behind the ear?

Answer 6

A basilar skull fracture.

Question 7

What are the boundaries of the infratemporal fossa?

Answer 7

Bounded medially by the lateral pterygoid plate, anteriorly by the maxilla, posteriorly by the occipital bone, and superiorly by the base of skull. Inferiorly it is continuous with the pharynx.

Question 8

Which facial nerve is found in the infratemporal fossa? Through which foramen does it pass through to get to the infratemporal fossa?

Answer 8

The trunk of V3; it passes through the foramen ovale to get there.

Question 9

Name the three fossae of the cranial cavity and what lies immediately inferior to each.

Answer 9

Anterior fossa: roof of the orbit is inferior to it.
Middle fossa: root of the infratemporal fossa is inferior to it.
Posterior fossa: the roof of the bony/muscular compartment of the neck is immediately inferior to it.

Question 10

What are paranasal sinuses? Name the four.

Answer 10

Air-filled spaces within the bones of the skull and face that communicate with the nasal cavity.

Frontal sinuses
Ethmoidal sinuses
Sphenoidal sinuses
Maxillary sinuses

Question 11

What forms the lateral walls of the nasal cavity? What do they do to inspired air?

Answer 11

Three spongy bones - the conchae (superior, middle, inferior). Their mucosal surfaces warm and humidify inspired air.

Question 12

What is found deep to the conchae? What happens here?

Answer 12

Meatuses - the paranasal sinuses drain into these.

Question 13

Name which meatus each paranasal sinus empties into.

Answer 13

They all empty into the middle meatus, except for the nasolacrimal duct, which drains into the inferior meatus, and the posterior ethmoidal air cells, which drain to superior meatus.

Question 14

What is different about how the maxillary sinus drains into the middle meatus?

Answer 14

The duct is located superomedially, so gravity can’t drain it unless the head is tilted to the side.

Question 15

What is sinusitis? What can cause it?

Answer 15

Infection of the sinuses, often caused by a previous respiratory tract infection.

Question 16

Where is pain from sinusitis referred to? Explain.

Answer 16

It is referred to the upper jaw because superior alveolar nerves (a branch of V2 trigeminal) supply the sinus with sensation as they pass through to supply sensation to the upper jaw.

Question 17

Name the three meningeal layers from superficial to deep.

Answer 17

Dura, arachnoid, pia mater

Question 18

Describe the dura mater.

Answer 18

Its made of two layers, a tough outer fibrous layer and an inner meningeal layer.

Question 19

Define the epidural space, subdural space, and subarachnoid space.

Answer 19

Epidural is external to the dura mater.
Subdural is between the dura and arachnoid mater.
Subarachnoid is between the arachnoid and pia mater, this is where CSF lives!

Question 20

Do the meninges protect the brain within the cranial cavity, provide support for blood vessels and venous sinuses, and enclose the subarachnoid space in which cerebrospinal fluid (CSF) circulates?

Answer 20

Yeah

Question 21

________ ligaments extend from the pia mater through the arachnoid to the dura mater to prevent lateral movement.

Answer 21

Denticulate ligaments

Question 22

Where in the meningeal layers is the middle meningeal artery found? What does this artery supply?

Answer 22

The middle meningeal artery runs within the two layers (outer periosteal and inner meningeal) of the dura mater.

Question 23

The dura mater is fused except for where it forms…?

Answer 23

except for where it forms dural venous sinuses that carry blood from tributaries of cerebral veins

Question 24

What is an arachnoid granulation?

Answer 24

A broccoli-looking thing that sticks up from the arachnoid mater so CSF can enter the dural venous sinuses.

Question 25

Where is CSF produced?

Answer 25

In the choroid plexuses, collections of cells in the brain.

Question 26

What is the diaphragma sellae?

Answer 26

A flat piece of dura mater above the pituitary gland with a circular hole allowing the vertical passage of the pituitary stalk.

Question 27

Which cranial nerve innervates the majority of the dura (except for the floor of the cerebellum)?

Answer 27

Trigeminal (CN V); C2 (CERVICAL) innervates the floor of the cerebellum.

Question 28

What does an epidural hematoma look like in a CT scan? How can it cause death?

Answer 28

Lenticular (lens-shaped) extravasation of blood. It can laterally deviate the brain, brain stem gets compressed into the tentorium cerebelli, which is sharp and can cut it.

Question 29

What is a subdural hemorrhage? What causes it usually? What does this look like in a CT scan?

Answer 29

Extravasation of blood (usually venous from a cerebral vein) between the dura and arachnoid mater. Typically as a result of trauma. The blood accumulation will be crescent shaped.

Question 30

Describe a subarachnoid hemorrhage.

Answer 30

Arterial rupture - usually from an intracranial aneurysm. Blood accumulates in the subarachnoid space and mixes with CSF - lumbar puncture might be blood-stained. Looks like random clustered spots on a CT (way different from epidural or subdural)

Question 31

What type of hemorrhage is associated with a basilar tip aneurysm?

Answer 31

Subarachnoid hemorrhage