Moore Text Practical 1 Flashcards
Temporal branch of CN VII
Emerges from the superior border of the parotid gland and crosses the zygomatic arch to supply the auricularis superior and inferior; the frontal belly of the occipitofrontalis; and the superior part of the orbicularis oculi
Zygomatic branch of CN VII
Passes via two or three branches superior and mainly inferior to the eye to supply the inferior part of the orbicularis oculi and other facial muscles inferior to the orbit
Buccal branch of CN VII
Passes external to the buccinator to supply this muscle and the muscles of the upper lip- upper parts of orbicularis oris and inferior fibers of the levator labii superioris
Marginal mandibular branch of CN VII
Supplies the risorius and muscles of the lower lip and chin. It emerges from inferior border of the parotid gland and crosses the inferior border of the mandible deep to the platysma to reach the face. In 20% of people, it passes inferior the the angle of the mandible
cervical branch of CN VII
Passes inferiorly from the inferior border of the parotid gland and runs posterior to the mandible to supply the platysma
Which other cranial nerve supplies motor innerv to muscles of the face besides CN VII (facial nerve)
Mandibular division of CN V- muscles of mastication
Main arterial supply to the face
Facial artery- arises from the external carotid artery and winds its way to the inferior border of the mandible, just anterior to the masseter. The artery lies superficially here, immediately deep to the platysma. Crosses the mandible, buccinator, and maxilla as it courses over the face to the medial angle of the eye. This artery lies deep to the zygomaticus major and levator labii superioris muscles.
Sends branches to the upper and lower lips- superior and inferior labial arteries. It ascends along the side of the nose, and anastomoses with the dorsal nasal branch of the ophthalmic artery. The terminal part of the facial artery is called the angular artery, which is distal to he lateral nasal artery at the side of the nose.
Two arteries accompanying cutaneous nerves in the face
Supra-orbital artery- branch of the ophthalmic artery, accompanies the Supra-orbital nerve across the eyebrows and forehead and continues to supply the anterior scalp to the vertex.
Mental artery- the only superficial branch derived from the maxillary artery, accompanies the nerve of the same name in the chin.
Which layer of the scalp are the arteries?
Within layer two of the scalp, the subcutaneous connective tissue layer between the skin and the epicranial aponeurosis.
The arterial walls are firmly attaches to the dense CT in which they are embedded, limiting their ability to constrict when cut. Consequently, bleeding from scalp wounds is profuse.
Facial veins
Valveless, coursing parallel with the facial arteries.
Primary superficial drainage of the face
Tributaries of the facial vein include the deep facial vein, which drains the pterygoid venous plexus of the infratemporal fossa
Drains directly or indirectly into the internal jugular vein. At the medial angle of the eye, the facial vein communicates with the superior ophthalmic vein, which drains into the cavernous sinus.
3 main neurovascular structures that traverse the parotid gland
Facial nerve, retromandibular vein and the external carotid artery
Fracture of the pterion
Overlies the frontal branches of the middle meningeal vessels, which lie in grooves on the internal aspect of the lateral wall of the calvaria.
The pterion is superior to the zygomatic arch and posterior to the frontal process of the zygomatic bone.
Hard blow to the side of the head may fracture the thin bones forming the pterion, resulting in a hematoma that exerts pressure on the underlying cerebral cortex- can cause death in a few hours
Background of the facial vein
The facial vein makes clinically important connections with the cavernous sinus through the superior ophthalmic vein, and the pterygoid venous plexus through the inferior ophthalmic and deep facial veins. Because of these connections, an infection of the face may spread to the cavernous sinus and pterygoid venous plexus.
Blood from the medial angle of the eye, nose and lips usually drains inferiorly through the facial vein, especially when a person is erect. Because the facial vein has no valves, blood may pass through the opposite direction.
Thrombophlebitis of facial vein
Inflammation of the facial vein with secondary thrombus (clot) formation
Pieces of an infected clot may extend into the intracranial venous system and produce thrombophlebitis of the cavernous sinus
Infection of facial veins spreading to the dural venous sinuses may result from lacerations of the nose or be initiated by squeezing pimples on the side of nose and upper lip- danger triangle of the face
Blunt trauma to the head
A blow to the head can detach the periosteal layer of dura mater from the calvaria without fracturing the cranial bones. In the cranial base, the two dural layers are firmly attached and difficult to separate from the bones. So, a fracture of the cranial base usually tears the dura and results in leakage of CSF. The innermost part of the dura, the dural border cell layer, is composed of flattened fibroblasts that are separated by large extracellular spaces. This layer constitutes a plane of structural weakness at the dura-arachnoid junction.
Tentorial herniation
The tentorial notch is the opening in the tentorium cerebelli for the brain stem, which is slightly large than is necessary to accommodate the midbrain. So, space-occupying lesions, such as tumors in the supratentorial compartment, produce increased ICP, and may cause part of the adjacent temporal love of the brain to herniated through the tentorial notch. During tentorial herniation, the temporal lobe may be lacerated by the tough tentorium cerebelli, and the oculomotor nerve (CN III) may be stretched, compressed or both. Oculomotor lesions may produce paralysis of the extrinsic eye muscles supplied by this CN.
Bulging of the diaphragma sellae
Pituitary tumors may extend superiorly through the aperture in the diaphragma sellae, or cause it to bulge. These tumors often expand the diaphragma sellae, producing disturbances in endocrine function before or after expansion. Superior extension of a tumor may cause visual symptoms owing to pressure on the optic chiasm, the place where the optic nerve fibers cross.
Occlusion of cerebral veins and dural venous sinuses
Can result from thrombi, thrombophlebitis, or tumors. The dural sinuses most frequently thrombosis are the transverse, cavernous and superior sagittal sinuses.
Cavernous sinus thrombosis usually results from infections in the orbit, nasal sinuses and superior part of the face. Cavernous sinus thrombophlebitis can go on to affect the abducens nerve as it traverses the sinus and may also affect the nerves embedded within the lateral wall of the sinus.
Septic thrombosis of the cavernous sinus often results in development of acute meningitis
Metastasis of tumor cells to dural venous sinuses
The basilar and occipital sinuses communicate through the foramen magnum with the internal vertebral venous plexuses. Because these venous channels are valveless, compression of the thorax, abdomen, or pelvis as occurs during heavy coughing or straining, may force venous blood from these regions into the internal vertebral venous system and from it into the dural venous sinuses. So, pus in abscesses and tumor cells in these regions may spread to the vertebrae and brain.
Fractures of the cranial base
The internal carotid artery may be torn, producing an ateriovenous fistula within the cavernous sinus. Arterial blood rushes into the sinus, enlarging it and forcing retrograde blood flow into its venous tributaries, especially the ophthalmic veins, causing the eyeball to protrude (exophthalmos) and the conjunctiva becomes engorged (chemosis). The protruding eyeball pulsates in synchrony with radial pulse (pulsating exophthalmos). Because CN III, IV, V1, V2, and VI lie in or close to the lateral wall of the cavernous sinus, these nerves may also be affected when the sinus is injured.
Dural origin of headaches
Pulling on arteries at the cranial base or veins near the vertex, where they pierce the dura will cause pain. Dissension of the scalp or meningeal vessels is believed to be one of the causes of headaches.
Many headaches appear to be dural in origin, such as the headache occurring after a lumbar spinal puncture for removal of CSF. These are thought to result from stimulation of sensory nerve endings in the dura. When CSF is removed, the brain sags slightly, pulling on the dura. So, patients are asked to keep their heads down after a lumbar puncture to minimize the pull on the dura.
Leptomeningitis
Inflammation of the leptomeninges (arachnoid and pia) resulting from pathogenic microorganisms. The infection and inflammation are usually confined to the SAS and the arachnoid-pia. Bacteria may enter the SAS through the blood or spread from an infection of the heart, lungs or other viscera. They may also enter the SAS from a fracture of the cranium or nasal sinuses. Acute purulent meningitis can result from infection with almost any pathogenic bacteria
Head injuries and intracranial hemmorrhage- epidural
Arterial in origin. Blood from torn branches of a middle meningeal artery collects between external periosteal layer of the dura and the calvaria. The extravasated blood strips the dura from the cranium. Usually this follows a hard blow to the head. A brief concussion (loss of consciousness) usually occurs, followed by a lucid interval of some hours. Later, drowsiness and coma occur. Compression of brain occurs as the blood mass increases.
Subdural hematoma
Dural border hematoma. No naturally occurring space between the dura-arachnoid junction. Usually caused by extravasated blood that splits open the dural border cell layer. The blood does not collect within a preexisting space, but rather creates a space. Hard blow to the head that jerks the brain inside the cranium. The precipitating trauma may be trivial or forgotten. Typically venous in origin and commonly results from tearing a superior cerebral vein as it enters the superior sagittal sinus.
Subarachnoid hemorrhage
Extravasation of blood, usually arterial, into the SAS. Usually result from rupture of an aneurysm (like of the internal carotid artery in strokes). Some are involved with head trauma involving cranial fractures and cerebral lacerations. Bleeding into the SAS results in meningeal irritation, severe headaches, stiff neck and often loss of consciousness
Danger area of the scalp
Loose connective tissue layer, since blood or pus spreads easily into it. Infection in this layer can also pass into the cranial cavity through small emissary veins, which pass through the parietal foramina in the calvaria, and reach intracranial sutures such as the meninges. An infection cannot pass into the neck, because the occipital bellies of the occipitofrontalis muscle attach to the occipital bone and mastoid parts of the temporal bones. Nor can a scalp infection spread laterally beyond the zygomatic arches because the epicranial aponeurosis is continuous with the temporal fascia that attaches to these arches. An infection or fluid can enter the eyelids and the root of the nose because the occipitofrontalis inserts into the skin and subcutaneous tissues and does not attach to the bone.
Occipitofrontalis facial expression
Front belly- elevates the eyebrows and wrinkles skin of forehead, protracts scalp (indicating surprise or curiosity)
Occipital belly- retracts scalp; increasing effectiveness of frontal belly
Orbicularis oculi facial expression
Closes eyelids: palpebral part blinks gently, orbital part tightly- winking.
Levator labii superioris and zygomatic minor facial expression
Part of dilators of mouth, retract (elevate) and/or evert upper lip; deepen nasolabial sulcus (showing sadness)
Orbicularis oris facial expression
Tonus closes oral fissure; phasic contraction compresses and protrudes lips (kissing) or resists distension (when blowing)
Buccinator facial expression
Presses cheek against molar teeth; works with tongue to keep food between occlusal surfaces and out of oral vestibule; resists distension (when blowing)
Zygomaticus major
Part of dilators of mouth; elevate labial commissary- bilaterally to smile (happy), unilaterally to sneer (disdain)
Levator Angeli oris
Part of dilators of mouth; widens oral fissure, as when grinning or grimacing.
Risorius and depressor anguli oris facial expression
Part of dilators of mouth; depresses labial commissure bilaterally to frown (sadness)
Depressor labii inferioris
Parts of dilators of mouth; retracts (depresses) and/or everts lower lip (pouting, sadness)
Mentalis muscle facial expression
Elevates and protrudes lower lip (“boo-boo lip”); elevates skin of chin (showing doubt)
Platysma facial expression
Depresses mandible against resistance; tenses skin of inferior face and neck (conveying tension and stress)
Neuralgias
Characterized by severe throbbing or stabbing pain in the course of a nerve caused by demyelinating lesion. Common cause of facial pain that is diffuse
3 common fractures of the maxilla
Le fort 1- horizontal fracture passing superior to the maxilla alveolar process (roots of the teeth) crossing the bony nasal septum and possibly the pterygoid plates of the sphenoid
Le fort 2- passes from the posterolateral parts of the maxillary sinuses superomedially through the infraorbital foramina, lacrimnals, or ethmoidal to the bridge of the nose. Entire central part of the face, including the hard palate and alveolar processes, is separated from rest of cranium
Le fort 3- horizontal fracture that passes through the superior orbital fissures and the ethmoid and nasal bones and extends laterally through greater wings of the sphenoid and frontozygomatic sutures. Concurrent fractures of zygomatic arches cause the maxilla and zygomatic bone to separate from the rest of the cranium
fractures of the mandible
Usually involves two fractures, which frequently occur on opposite sides of the mandible.
Fractures of the coronoid process are uncommon and usually single
Fractures of the neck of mandible are often transverse and may dislocate the TMJ on same side
Fractures of the angle are usually oblique and may involve the bony socket or alveolus of 3rd molar tooth
Fractures of the body pass through the socket of a canine tooth
Fractures of the calvaria
Hard blows in thin areas= depressed fractures, where bone is depressed inward
Linear calvaria fractures are most common, at the point of impact with fracture lines radiating away
Contrecoup fracture- no fractures occur at point of impact, but one occurs on the opposite side of the cranium
What two bony features of the skull are not present at birth
Mastoid and styloid processes
So the facial nerves are close to the surface when they emerge from the SM foramina, so they may be injured by forceps during a difficult delivery or later by an incision posterior to the auricle of the external ear (for mastoiditis)
Fontanelle positions
Anterior- bregma
Posterior- lambda
Sphenoidal and mastoid- overlain by the temporalis muscle
Which cranial bone is the most dynamic with age
Mandible
Premature closure of the cranial sutures
Types
Primary craniosynostosis
Results in several cranial malformations
Theory to be caused by abnormal development of cranial base that may exaggerate the dura mater that disrupt normal cranial suture development
Scaphocephaly- premature closure of sagittal suture= small, long, narrow wedge shaped cranium
Plagiocephaly- coronal or lambdoid suture on one side= cranium is twisted and asymmetrical
Oxycephaly or turricephaly- coronal suture= high, tower-like cranium
Usually do no affect brain development
