1 ` 2019 Neuroanatomy Objectives

Cerebral Cortex

Cortical Lobes Occipital Lobe Temporal Lobe Limbic Lobe (Insula)

Major Cortical and Lobe Division Landmarks Central (CS) Lateral (LF) Preoccipital Notch Parieto-occipital Fissure (POF)

Frontal Lobe Precentral Gyrus (Primary Motor Cortex – M1) Precentral Sulcus Brocca’s Area (Expressive Speech) Prefrontal Cortex (Cognition)

Parietal Lobe Postcentral Sulcus Postcentral Gyrus (Primary Sensory Cortex – S1) Central Sulcus

Occipital Lobe Calcarine Fissure Primary Visual Cortex (V1)

Temporal Lobe Superior Temporal Sulcus Heschl’s Gyrus (Primary Auditory Area –A1) Wernicke’s Area (Comprehensive Speech Area)

Limbic Lobe Structures Cingulate Gyrus (Cognition). Cingulate Sulcus Parahippocampal Gyrus (Memory) Uncus – Near Primary Olfactory Cortex (Smell).

Summary of Major Functional Centers of the Cerebral Cortex and Motor Control – Precentral Gyrus (M1), cranial V, VII, IX, X, XII.

2 Head and Neck Sensory – Post Central Gyrus (S1), head area receives sensory information largely from cranial V. Speech – Broca’s Area (speech production) and Wernicke’s Area (speech comprehension). – Primary Auditory Cortex (A1) Vision – Primary Visual Cortex (V1) (within the depths of the calcarine fissure) Smell –Limbic Cortex (Near Uncus)

Interhemispheric Commissures Anterior and Posterior Commissures

Brainstem

Diencephalon Thalamus (sensory relay to cortex and motor relay to cortex) Hypothalamus (basic physiologic drives and homeostasis) 3rd Ventricle

Midbrain Superior Colliculus ( relay) Inferior Colliculus ( relay) Cerebral Aqueduct (Aqueduct of Sylvius)

Pons and Superior Cerebellar Peduncle - white matter pathway (i.e., nerve fibers) connecting midbrain and cerebellum. Middle Cerebellar Peduncle -white matter pathway connecting and cerebellum. Inferior Cerebellar Peduncle -white matter pathway connecting medulla and cerebellum. 4th Ventricle

Medulla Pyramids Olives 4th Ventricle

Blood Supply of Central Circle of Willis Anterior Communicating Anterior Cerebral Artery Posterior Communicating Artery Posterior Cerebral Artery

Anterior Circulation (Internal Carotid Artery) Internal Carotid Artery Anterior Cerebral Artery Anterior Communicating Artery Posterior Communicating Artery

3 Posterior Circulation (Vertebral and Basilar ) Vertebral Arteries Posterior Spinal Arteries Posterior Inferior (PICA) Basilar Artery Anterior Inferior Cerebellar Artery (AICA) Superior Cerebellar Artery Posterior Cerebral Artery

CSF Cavities and Passageways Lateral Ventricle Foramen of Monro 3rd Ventricle Cerebral Aqueduct 4th Ventricle Cisterna Magna Superior Sagittal

CSF Circulation

Interventricular Lateral Ventricles 3rd Ventricle Foramen of Monro

Cisterna Magna Aqueduct of Sylvius Superior Sagittal (Cerebral Aqueduct) Sinus (Arachnoid Granulations) 4th Ventricle

Confluence of Sinuses

Transverse Sinus

Sigmoid Sinus

Internal Jugular

Vein

4 Dura matter - The external covering that forms the outermost layer of the meninges. Is dense . Contains the sinuses and forms folds of septa (i.e. ). Arachnoid matter - Middle layer of meninges. Web-like connective tissue matrix that does not enter sulci of cerebral cortex. The arachnoid is partly separated from the pia matter by the subarachnoid space which contains (CSF). Pia matter - Inner layer of meninges. Thin connective tissue membrane that adheres to the nervous tissue (faithfully follows the underlying nervous tissue of the ).

Folds of Dura Matter Falx cerebri – Sickle shaped sheet of dura that forms a partition between the two cerebral (cortical) hemispheres. Tentorium cerebelli- Fold of dura that separates the cerebral hemisphere from the cerebellum. (Forms roof over posterior cranial ). -Small sickle shaped fold of dura that extends slightly between the cerebellar hemispheres.

Venous Sinuses of the Dura Matter -Located within superior part of falx cerebri. Contains many arachnoid villa that constitute the main site of passage of CSF into the venous blood. Drains into the confluens of sinuses. Inferior sagittal sinus- Located on the free margin (inferior border) of the falx cerebri. Drains into the . Straight sinus- Located in the tentorium cerebelli. Drains into the confluens of sinuses. Transverse sinus- Drains into the . Sigmoid sinus – Drains into the internal jugular . Superior and inferior petrosal sinuses- Both drain posteriorly. The drains into internal and the into sigmoid sinus. - Drains posteriorly into the superior and inferior petrosal sinuses.

Cranial Nerves (CN’s)

CN I – Olfactory CN VII - Facial CN II – Optic CN VIII -Vestibulocochlear CN III – Oculomotor CN IX - Glossopharyngeal CN IV – Trochlear CN X - Vagus CN V – Trigeminal CN XI - Accessory CN VI - Abducens CN XII-Hypoglossal

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I. Cranial Fossae:

Anterior, Middle and Posterior Cranial Fossae

A. - Formed by frontal (orbital plate), (, ) and the (lesser wings). 1. Foramen: a. Cribriform plate - (for CN I)

B. – Formed by the sphenoid bone (greater wings, ), and (petrous part, inner surface of squamous part). 1. Foramen: a. Optic - CN II and . b. - Ophthalmic vein, CN V1, CN III, CN IV, CN VI, sympathetic fibers. c. - CN V2. d. - CN V3. e. - . f. Foramen lacerum - Internal carotid artery and . g. – below middle cranial fossa, contains internal carotid artery. g. Hiatus of greater petrosal nerve - Greater petrosal nerve (of CN VII). i. Hiatus for the lesser petrosal nerve - Lesser petrosal nerve (of CN IX).

C. - Formed by , temporal bone (petrous part, mastoid part), and sphenoid bone (body). a. - , meninges, CN XI, and spinal arteries. b. - CN’s IX, X and XI, , sigmoid sinus, inferior petrosal sinus. c. - CN XII. d. Internal acoustic - CN VII, CN VIII, labyrinthine (auditory) artery.

6 Foramina of the

Anterior Ethmoidal Forman

Located in the anterior . Contains the anterior ethmoidal branch of the (V1), anterior ethmoidal artery, and anterior ethmoidal vein.

Carotid Canal

Located in the petrous portion of the temporal bone. Contains the internal carotid artery, internal carotid plexus (sympathetic), and (sympathetic) arising from the internal carotid plexus.

Condylar Canal

Located posterior to occipital condyle. Contains emissary vein linking the vertebral vein with the sigmoid sinus. Also called the posterior (see hypoglossal canal for anterior condylar canal). Also may contain an arterial branch from the that supplies the dura of the posterior cranial fossa.

Foramen Lacerum

Located at the medial end or apex of the petrous portion of the temporal bone, basal portion of the occipital bone, and sphenoid bone. It is spatially continuous with the carotid canal. During life the lower part floor of the foramen lacerum is closed with dense fibrous connective tissue and only a few small vessels pass through this foramen from the cavity of the skull to the exterior base of the skull. The main portion contains the internal carotid artery (and internal carotid plexus, deep petrosal nerve) and greater (superficial) petrosal nerve of CN VII. Inferior and anterior the foramen lacerum is continuous with the .

Foramen Magnum

Located in the occipital bone. Contains the spinal cord and meninges, spinal portion of the (CN XI), right and left vertebral arteries, anterior and posterior spinal arteries, and apical ligament of the odontoid of the .

Foramen Ovale

Located in the greater wing of the sphenoid bone. Contains the (V3) lesser (superficial) petrosal nerve and accessory meningeal vessels.

Foramen Rotundum

Located in the greater wing of the sphenoid bone. Contains V2.

Foramen Spinosum

Located in the greater wing of the sphenoid bone. Contains the middle meningeal artery and vein, and a meningeal branch of the mandibular nerve (a recurrent sensory branch from V3 passing upward from the to innervate the cranial dura).

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Located between the and the at the posterior lateral border of the hard . Contains the greater (anterior) palatine nerve, (know up to this point as the descending palatine artery) and corresponding .

Hiatus for the Greater Petrosal Nerve

Located in the tegmen tympani (roof of middle ) of the petrous temporal bone, in front of the arcuate eminence. Contains the greater (superficial) petrosal nerve of CN VII.

Hiatus for the Lesser Petrosal Nerve

Located in the tegmen tympani of the petrous temporal bone, about 3 mm anterolateral to the hiatus for the greater petrosal nerve. Contains the lesser (superficial) petrosal nerve of CN IX.

Hypoglossal Canal

Located in the occipital bone above the anterior part of the occipital condyle. Contains the (CN XII) and posterior meningeal branch of the ascending pharyngeal artery. Also known as the anterior condylar canal.

Incisive Foramen and Canals

Located in the maxillary bone. The foramen is located in the anterior region of the , immediately behind the teeth. The are usually visible within the . This complex contains the (branch of V2) and distal branches of the septal artery (from ) which descend on the (bone) of the , as well as the greater and vessels (traveling from the hard palate, below).

Inferior Orbital Fissure

Located between the greater wing of the sphenoid bone and maxilla. Contains the (V2), branches from the pterygopalatine to the , superior alveolar nerves (anterior and middle), infra-orbital artery and vein and .

Infra-Orbital Canal

Located on the anterior orbital surface of the maxilla. Contains the infra-orbital nerve, artery and vein.

Infra-Orbital Foramen

Located at the anterior opening of the infra-orbital canal, in the maxilla below the infra-orbital margin. Contains the infra-orbital nerve, artery and vein (supplies portion of the mid-).

Internal Acoustic Meatus

Located in the posterior medial surface of the petrous temporal bone. Contains the (CN VII), (CN VIII), and labyrinthine (auditory) artery (commonly from AICA but can originate from the basilar artery, superior cerebellar artery or less often PICA).

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Jugular Foramen

Located between the petrous temporal and occipital bone. Contains the glossopharyngeal nerve (CN IX), (CN X), accessory nerve (CN XI), sigmoid sinus, inferior petrosal sinus, and meningeal branches of the occipital and ascending pharyngeal arteries.

Lesser Palatine Foramen

Located in the posterior inferior aspect of the palatine bone. Contains the lesser palatine nerve and vessels which in part, supply the .

Mandibular Foramen

Located on the inner surface of the ramus of the . Contains the (from V3) and vessels.

Mental Foramen

Located on the outer surface of the body of the mandible usually below the second tooth. Contains the (a distal branch of V3) and vessels.

Mastoid Foramen

Located posterior to mastoid part of the temporal bone. Contains emissary vein linking with sigmoid sinus.

Nasolacrimal Canal

Located at the anterior, lower medial border of the formed by the and maxilla. Contains the .

Optic Foramen/Canal

Located in the sphenoid bone between the body and root of the lesser wing. Contains the and ophthalmic artery. Most consider the foramen and canal as synonymous terms, yet another perspective is the optic foramen is the posterior opening to the portion.

Petrotympanic Fissure

Located in the temporal bone (specifically between tympanic part of the temporal bone and tegmen tympani). Contains the nerve and anterior tympanic artery (a branch from the )

Posterior Ethmoidal Foramen

Located approximately 1-2cm behind the anterior ethmoidal foramen, in or near the frontoethmoidal suture. Contains the posterior ethmoidal nerve and vessels.

9 Posterior Superior Alveolar Canal

Located in the posterior center of the infratemporal surface of the maxilla. Contains the posterior superior alveolar nerves (V2) and vessels (from maxillary artery/vein).

Pterygoid Canal

Located at the root of the pterygoid processes of the sphenoid bone in line with the medial pterygoid plate. Contains the nerve in the pterygoid canal (also known as the Vidian nerve). It is formed by the joining of the greater petrosal nerve (parasympathetic branch from the facial nerve) and deep petrosal nerve (sympathetic branch from the carotid plexus).

Pterygopalatine Foramen ()

Located at the upper end of the perpendicular plate of the palatine bone between its orbital and sphenoid processes. The foramen is located in the medial wall of the , and in the lateral wall of the . Contains the sphenopalatine artery and lateral, posterior superior nasal branches of V2.

Pterygopalatine Fossa (Sphenopalatine Fossa)

Is a large pyramidal space behind and below the apex of the orbit. It communicates laterally with the infratemporal fossa through the , medially with the nasal cavity through the sphenopalatine (or pterygopalatine) foramen, posteriorly with the through the foramen rotundum, and anteriorly with the orbit through the . It transmits branches of the maxillary nerve (V2), facial nerve and carotid plexus (nerve in the pterygoid canal or Vidian nerve) and maxillary vessels.

Pterygomaxillary Fissure

Opening between the lateral pterygoid plate of the sphenoid bone and the infratemporal (posterior) surface of the maxilla and is continuous above with the inferior orbital fissure. It transmits the maxillary artery (entering the pterygopalatine fossa), and the posterior superior alveolar nerve (a branch from V2 which leaves the pterygopalatine fossa to enter the maxilla on its infratemporal surface).

Stylomastoid Foramen

Located between the styloid process and the mastoid process of the temporal bone. Contains the facial nerve (CNVII: motor branches to muscles of facial expression; and a sensory + motor branch of VII termed the posterior auricular nerve) and the stylomastoid arterial branch of the posterior auricular artery.

Superior Orbital Fissure

Located in the sphenoid bone between the body and the greater and lesser wings. Contains the occulomotor nerve (CN III), (CN IV), abducens (or abducent) nerve (CN VI). Also contains the , and nasociliary nerve of the (all branches of V1). Finally, contains the , orbital branch of the middle meningeal artery, and nerve branch (or ramus) from the internal carotid plexus (sympathetic – innervation to the orbit).

10 Superior Orbital Notch or Foramen

Located on the medial aspect of the supra-orbital margin of the . Contains the (from frontal nerve of V1) and vessels.

Zygomatico-Facial Foramen

Located on the anterior lateral surface of the (also referred to as the external surface, facial surface, or malar surface of zygomatic bone). Contains the (branch of V2) and vessels.

Zygomatico-Orbital Foramen

Located in the orbital surface of the zygomatic bone (internal surface facing the orbital cavity). Contains the zygomatic branch of the maxillary nerve (branch of V2).

Zygomatico-Temporal Foramen

Located near the base of the frontal process of the zygomatic bone, specifically on the temporal surface of the zygomatic bone in the infratemporal fossa (i.e., external posterior surface of the zygomatic bone facing the infratemporal fossa). Contains the zygomtic-temporal nerve (branch of V2).

11 Introduction to the Head, and Face

I. Nerves to the Face

A. Trigeminal Nerve (cranial nerve V) -Divides into three major branches: Ophthalmic, Maxillary and Mandibular. As a note, the three branches will in turn, divide into additional branches that exit skull to supply skin with somatic sensory fibers (, temperature and touch receptors). One branch (Mandibular) will also supply muscles.

1. - A sensory nerve which supplies orbit, face and nose. a. Lacrimal Nerve (in lateral orbit). Terminal branches supply sensation to the skin over the lateral superficial eye. b. Frontal Nerve (in midline of orbit). Supplies sensation to the and front of the scalp (via terminal branches of the supraorbital and supratrochlear nerves). c. Nasociliary Nerve (in medial orbit) - Supplies sensation to the tip of nose (via terminal branches of the ) and the skin over the superior medial aspect of the nose (via terminal branches of the ). Posterior ethmoidal nerve also branches from nasociliary nerve to supply the posterior superior nasal cavity nasal .

2. Maxillary Nerve - A sensory nerve which supplies tissues associated with maxillary bone. Divides into several branches to the face: a. - Supplies sensation to upper , lower lid, upper , and lateral nose. b. Zygomaticotemporal Nerve – Supplies sensation to skin over anterior part of . c. Zygomaticofacial Nerve – Supplies sensation to skin over zygomatic bone (cheek).

3. Mandibular Nerve – A sensory and motor nerve which supplies tissues associated with the mandible. The motor part innervates the (i.e. muscles associated with chewing). Divides into several major branches: a. (some refer to this as the long buccal nerve) - Supplies sensation to skin over cheek (i.e., over ). b. -Supplies sensation to parts of the ear and skin over temporal region. c. Inferior Alveolar Nerve - Enters mandible to supply sensation to the teeth. The nerve passes through to form the Mental Nerve (see below). d. Nerve to the Mylohyoid – Motor branch that innervates the and anterior belly of the . e. - Supplies the anterior 2/3’s of the and floor of the mouth with sensory fibers. f. Mental Nerve- Supplies skin over the and lower mandible. Represents the terminal part of the inferior alveolar nerve. g. Motor Nerves to Muscles – Temporalis, masseter, medial pterygoid, lateral pterygoid, mylohyoid, anterior belly of digastric, tensor palatini and tensor tympani muscles.

12 B. Facial Nerve (Cranial Nerve VII) - A motor nerve to the muscles of facial expression which include the muscles directly over the facial skeleton, as well as the (neck), (back of scalp) and external auricular (ear) muscles. The nerve emerges from the and divides into 5 general branches that are purely motor: 1. Temporal 2. Zygomatic 3. Buccal (Do not confuse with the buccal branch of the trigeminal which is sensory!) 4. Marginal Mandibular 5. Cervical

Mnemonic: To Zanzibar By Motor Car (Please – posterior auricular n)

Note, another branch of facial nerve arising from stylomastoid foramen courses posteriorly as the posterior auricular nerve which innervates occipital belly of occipitofrontalis muscle. This nerve also contains sensory fibers to external ear and skin posterior to ear. There is also a short motor nerve of the facial nerve to the and posterior belly of the digastric muscle.

II. Major Arteries to the Face

A. – Main artery of the face (including lip and nose). It is a branch of the external carotid system. Gives rise to inferior labial and superior labial branches and continues upward running along the lateral part of the nose and eventually to the medial angle of the eye. Along the lateral part of the nose it is called the .

B. Superficial Temporal Artery- One of the two terminal branches of the (the other is the maxillary). Supplies temporal region (over squamous [smooth] part of temporal bone and scalp).

C Transverse Facial Artery- Small artery that arises from the superficial temporal artery and passes under the to lateral angle of eye.

III. Major Veins of the Face

A. - Courses posterior to facial artery and empties into the internal jugular vein. It often sends a communicating branch to the . It provides the major venous drainage of the face. (Once was commonly called anterior facial vein).

B. Superficial Temporal Vein - Drains temporal region and scalp and joins the retromandibular vein (see below).

C. Retromandibular Vein - Formed by union of superficial temporal and . It joins facial vein anteriorly and posteriorly. (Once was commonly called posterior facial vein).

IV. Lymphatic Drainage of the Face

A. The mid-face drains through lymphatic vessels that empty into the submandibular and submental lymph nodes.

B. The lateral face drains into parotid lymph nodes.

13 C. Submandibular and parotid nodes in turn drain into cervical nodes.

V. Basic Organization of the Scalp - Consists of 5 layers from superficial to deep (S-C-A-L-P).

A. Skin B. Connective Tissue C. - Specifically referred to as Galea Aponurotica or . Strong membranous sheet of connective tissue that covers the dome of the from the highest nuchal line posteriorly (a bony attachment) to the anteriorly (no bony attachment). It links together the paired muscular frontal bellies (located anteriorly over the frontal bone) with the paired occipital bellies (located posteriorly over the occipital bone). Collectively the muscle is called the occipitofrontalis and is innervated by the facial nerve. D. - Loose, sponge-like connective tissue which permits free movement of the scalp. This is a danger area of the scalp since pus or blood can spread easily throughout the scalp. E. Pericranium - Fibrous periosteum (also connective tissue) of the skull (calvaria).

Muscles of Facial Expression

General Information

 Facial nerve (CN VII) innervates all and 3 deep muscles (stylohyoid, posterior belly of the digastric, and stapedius muscles).  Muscles of the face vary in their development.  The superficial closely invests a number of the facial muscles.  The fascia is so tightly adherent to the muscle and skin that all practical purposes, there are no potential spaces for infection within this area. (The exception is around the eyes where the fascia is not tightly adherent).  The nerves generally enter the muscles on deep surfaces and typically do so close to the posterior border of the muscle.  In general, the muscles of facial expression originate from bone and insert into skin (exceptions are platysma, and procerus). The terminal fibers of the muscles that insert into the skin often interdigitate with fibers of other adjacent muscles of facial expression.  The facial artery lies deep to the platysma, risorius, and the zygomaticus major and minor, but crosses superficial to the buccinator and the .  SMAS – Superficial Muscular Aponeurotic System- plane of tissue in face/neck containing facial muscle fibers, and elsewhere fibrous or fibro-aponeurotic tissue. It is not directly attached to bone. (e.g., see Perkins and Waters, Facial Plast. Surg. Clin. North Am., 2014, 22:253-268; Broughton and Fyfe, Anat. Res. Int., 2013; Pessa, Anesthet. Surg. J., 2016, 36:515-526; Hwang Choi, J. Craniofac. Surg. 2018, 29:1378-1382).

The facial muscles are divided into 6 broad categories based upon region.

I – Mouth II – Nose III – Eye (orbital group) IV – Ear V – Scalp VI- Cervical (neck)

14 Facial Muscles (learn specific origins and insertions only if it is beneficial to you)

I. Mouth

- Lower Group (depressors) - All muscles arise (or originate) from mandible and are innervated by the marginal mandibular branch of CN VII.

1. Depressor Anguli Oris Originates from the mandible and inserts on the corner of the mouth and skin. Its function is to depress the corner of the mouth. It is often well developed, the most superficial and the most lateral of the depressor group.

2. Depressor Labii Inferioris Originates from the mandible in part from under the depressor anguli. It inserts into the skin of the chin. It functions to depress the lower lip.

3. Mentals This is the deepest lying muscle of the group. It originates from the mandible. It inserts the skin of the chin. Its function is to draw the lower lip to the gingiva.

-Middle (lateral) Group

1. Risorius This is a thin and poorly defined muscle and different in that it does not arise from the bone. It arises from subcutaneous skin over the parotid and inserts on the corner of the mouth into the skin and mucosa. Like the platysma it crosses superficial to the facial vein and artery. Its function is to draw the corner of the mouth laterally and upward (similar to the zygomatic muscles). Innervated by the buccal branch of CN VII.

2. Zygomaticus Major Originates from the zygomatic bone, anterior to the zygomaticotemporal suture and passes obliquely down to insert onto the corner of the mouth where it attaches to the skin and mucosa. It is positioned superficial to the buccinator muscle and facial vessels. Innervated by the zygomatic and buccal branches of CN VII.

3. Zygomaticus Minor Originates from the zygomatic bone posterior to the zygomaticomaxillary suture. It passes downward and medially to insert into the muscular substance of the upper lip. The action of the zygomaticus major and minor is to draw the angle of the mouth upwards and laterally. Innervated by the buccal branch (and possibly the zygomatic branch in some cases) of CN VII.

Upper Group (levators) – All muscles innervated by the buccal branch of CN VII

1. Alaeque Nasi Originates from the frontal process of the maxilla lateral to the nose. It inserts into the skin and alar cartilage of the nose but primarily into the skin of the upper lip. Its primary action is to raise and evert the upper lip.

15 2. Levator Labii Superioris It originates from the of the maxilla, under the orbicularis oculi. It inserts into the