Cranial cavity l General head and neck revision  for dental students

Anatomy of cranial cavity 

INTRODUCTION

• Cranial cavity, the highest placed cavity, contains the brain, meninges, venous sinuses, all cranial nerves, four petrosal nerves, parts of internal carotid artery and a part of the vertebral artery besides the special senses. The anterior branch of middle meningeal artery lies at the pterion and is prone to rupture resulting in extradural hemorrhage.

CONTENTS OF CRANIAL CAVITY

• The convex upper wall of the cranial cavity is called the vault. It is uniform and smooth. The base of the cranial cavity is uneven and presents three cranial fossae (anterior, middle and posterior) lodging the uneven base of the brain.

• The cranial cavity contains the brain and meninges : the outer dura mater, the middle arachnoid mater, and the inner pia mater. The dura mater is the thickest of the three meninges. It encloses the cranial venous sinuses, and has a distinct blood supply and nerve supply. The dura is separated from the arachnoid by a potential subdural space.

• The arachnoid is separated from the pia by a wider subarachnoid space filled with cerebrospinal fluid (CSF). The arachnoid, pia, subarachnoid space and CSF are dealt with the brain; the dura is described here. This chapter also includes hypophysis cerebri, trigeminal ganglion, middle meningeal artery and other structures seen after removal of the brain, e.g. various cranial nerves and internal carotid artery.

 

Dural Folds

Definition : 

• They are double sheet of inner layer of dura, separate different parts of the brain supporting them.

1. Falx Cerebli

Shape:           

• Sickle

Site :  

• Between 2 Cerebral hemisphere

Attachment :           

• Upper margin: Related to Sagittal Sulcus
• Lower margin: Related to corpus callosum
• Base : Attached to sup surface of Tentorium Cerebelli
• Apex : Attached to Frontal Crest & Crista Galli

Content :      

1. Superior Sagittal sinus: At upper margin
2. Inferior Sagittal sinus: At posterior 2/3 of lower margin
3. Straight sinus:  between tentorium Cerebelli , Falx Cerebri

2. Tentorium Cerebelli

Shape:

• Tent-shaped

Site :  

• Between Cercbrum, Cerebellum

Attachment :

• Superior Surface: Attached to base of Falx Cerebri Base:
• Inferior Surface: Attached to base of Falx Cerebelli
• Free Border: Attached to Ant. Clenoid process
• Attached Border: Attached to:

1. Posterior clenoid Process
2. Superior Petrosal Sulcus
3. Transverse Sulcus     

Content :      

1. Straight : between tentorim Cerebelli. Falx Cerebri
2. Superior petrosal sinus: Along Sup. Petrosal Sulcus
3. Transverse sinus: Along transverse sulcus

 

3. Falx Cerelbelli

Shape:

• Inverted triangle      

Site :  

• Between 2 Cerebellar, hemisphere

Attachment :           

• Base: Attached to inf. Surface of T. Cerebelli
• Apex: attached to post. Border of F. magnum
• Anterior margin: Free
• Posterior margin :attached to in. occipital crest

Content :      

• Occipital: Along post margin

4- Diaphragma sellae:

Shape :

• Circular

Attachment :           

• Above pituitary gland

Site :  

1. Anterior : to tuberculum sellea
2. Posterior : to dorsum sellea

Content :

• Inter-cavernous

 

CLINICAL ANATOMY

• Pain-sensitive intracranial structures are:

1. The large cranial venous sinuses and their tributaries from the surface of the brain
2. Dural arteries
3. The dural floor of the anterior and posterior cranial fossae
4. Arteries at the base of the brain.

• Headache may be caused by:

• Dilatation of intracranial arteries
• Dilatation of extra cranial arteries
• Traction or distension of intracranial pain sensitive structures
• Infection and inflammation of intracranial and extra cranial structures supplied by the sensory, cranial and cervical nerves.

• Extradural and subdural hemorrhages :

• both are common. An extradural hemorrhage can be distinguished from a subdural hemorrhage because of the following differences:

1. The extradural hemorrhage is arterial due to injury to middle meningeal artery, whereas subdural hemorrhage is venous in nature.
2. Symptoms of cerebral compression are late in extradural hemorrhage.
3. In an extradural hemorrhage, paralysis first appears in the face and then spreads to the lower parts of the body. In a subdural hemorrhage , the progress of paralysis is haphazard.
4. In an extradural hemorrhage, there is no blood in the CSF, while it is a common feature of subdural hemorrhage.