Head, Neck, Vestibular, and Cranial Nerve Neurovascular Anatomy

Comprehensive practice flashcards covering head and neck neurovascular structures, cranial meninges, dural venous sinuses, brain arterial circle, vestibular anatomy and neurophysiology, and cranial nerve functional components, pathways, and clinical lesions.

What are the two layers of the cranial dura mater, and how does its connection to the spinal cord compare to the spinal dura mater?

The cranial dura mater consists of an outer periosteal layer (attached to the skull and continuous with pericranium at cranial foramina) and an inner meningeal layer. Only the inner meningeal layer continues through the foramen magnum to become continuous with the spinal dura mater.

What two types of anatomical structures are created when the two layers of cranial dura mater separate?

The separation of the periosteal and meningeal dural layers forms dural partitions (inward projections that subdivide parts of the brain) and intracranial venous structures (dural venous sinuses).

What are the four dural partitions found within the cranial cavity?

1. Falx cerebri
2. Tentorium cerebelli
3. Falx cerebelli
4. Diaphragma sellae

What structure traverses the central opening of the diaphragma sellae, and what is its function?

The infundibulum passes through the central opening of the diaphragma sellae, connecting the pituitary gland in the hypophyseal fossa with the base of the brain along with its accompanying vessels.

Which arteries provide the primary blood supply to the dura mater in each cranial fossa?

• Anterior cranial fossa: Anterior meningeal arteries (branches of ethmoidal arteries) • Middle cranial fossa: Middle and accessory meningeal arteries (branches of maxillary artery) • Posterior cranial fossa: Posterior meningeal artery and branches from the ascending pharyngeal, occipital, and vertebral arteries

How is the cranial dura mater innervated across its different regions?

• Floor & anterior part of falx cerebri: Ophthalmic division ($V_1$) • Tentorium cerebelli & posterior part of falx cerebri: Ophthalmic division ($V_1$) • Middle cranial fossa medially: Maxillary division ($V_2$) • Middle cranial fossa laterally: Mandibular division ($V_3$) • Posterior cranial fossa: Cervical nerves C1, C2, and sometimes C3, plus possibly the vagus nerve (CN X)

What are the three cranial meningeal spaces and their structural locations?

• Epidural space: Potential space between the dura mater and the calvaria • Subdural space: Potential space in the innermost dural layer near the dura-arachnoid interface • Subarachnoid space: Normally present, fluid-filled space containing cerebrospinal fluid (CSF) and blood vessels, enlarged in cisterns

What is the complete anatomical pathway of cerebrospinal fluid (CSF) circulation from production to reabsorption?

CSF is produced by choroid plexus in the ventricles $\rightarrow$ lateral ventricles $\rightarrow$ interventricular foramina of Monro $\rightarrow$ third ventricle $\rightarrow$ cerebral aqueduct of Sylvius $\rightarrow$ fourth ventricle $\rightarrow$ subarachnoid space via midline foramen of Magendie and two lateral foramina of Luschka $\rightarrow$ arachnoid villi/granulations $\rightarrow$ superior sagittal sinus and lateral lacunae.

What volume of cerebrospinal fluid (CSF) is normally produced each day in an adult?

Approximately half a liter ($0.5\,\text{L}$ or $500\,\text{mL}$) each day.

What clinical constellation of symptoms typically characterizes Cerebro-spinal Fluid (CSF) Leak syndrome?

Dizziness, nausea, fatigue, and a metallic taste in the mouth.

What is Kernig's sign in the context of meningitis, and what does a positive sign indicate?

Kernig's sign is assessed with a straight leg raise test; reproduction of marked neck pain constitutes a positive sign, indicating meningeal irritation that requires emergency medical attention.

What are the five embryological/developmental divisions of the brain listed from rostral to caudal?

1. Telencephalon (cerebral hemispheres)
2. Diencephalon (thalamus, hypothalamus)
3. Mesencephalon (midbrain)
4. Metencephalon (pons and cerebellum)
5. Myelencephalon (medulla oblongata)

What are the intracranial branches of the vertebral and basilar arteries?

• Vertebral arteries: Small meningeal branches, anterior spinal artery, posterior spinal artery, and posterior inferior cerebellar artery (PICA) • Basilar artery: Anterior inferior cerebellar artery (AICA), pontine arteries, superior cerebellar artery (SCA), and terminal bifurcation into the two posterior cerebral arteries (PCA)

What four major branches arise from the internal carotid artery within the cranium?

1. Ophthalmic artery
2. Posterior communicating artery
3. Middle cerebral artery (MCA)
4. Anterior cerebral artery (ACA)

Why do emissary veins present a high clinical risk for the spread of cranial infections?

Emissary veins lack valves, which allows blood and infections to flow backwards from extracranial tissues directly into the intracranial dural venous sinuses.

What are the arterial supply, venous drainage, and lymphatic drainage of the facial tissues?

• Arterial supply: Branches of the external carotid artery (facial artery, transverse facial artery, maxillary artery) • Venous drainage: Facial and transverse facial veins (connecting to the cavernous sinus via emissary veins) • Lymphatic drainage: Submental, submandibular, and pre-auricular/parotid lymph nodes

What are the three main functional divisions of the vestibular system organization?

1. Peripheral sensory apparatus (semicircular canals, otolith organs, vestibular nerve)
2. Central processor (vestibular nuclear complex and cerebellum)
3. Mechanism for motor output (eye movements and positional movements)

How are the three pairs of semicircular canals arranged geometrically, and what is the tilt of the horizontal canal?

They are arranged in three coplanar pairs at $90^\circ$ angles to each other. The horizontal semicircular canal is tipped backward by $30^\circ$ relative to the horizontal plane.

What mechanical deflection of hair cell stereocilia produces excitation versus inhibition in the vestibular ampullae?

Deflection of stereocilia toward the kinocilium causes depolarization (excitation), whereas deflection away from the kinocilium causes hyperpolarization (inhibition).

What are the specific sensory stimuli detected by the utricle and saccule within the otolith organs?

• Utricle: Detects horizontal linear acceleration and gravitational orientation changes during pitch (flexion/extension) and roll (lateral flexion) • Saccule: Detects vertical linear acceleration

What is the structural composition of the otolithic membrane and otoconia?

The otolithic membrane is a fibrous and gelatinous matrix overlying the maculae into which stereocilia and kinocilia project. Otoconia are small calcium carbonate crystals covering the outer surface of this membrane.

Which vestibular structures are supplied by the anterior vestibular artery?

The vestibular nerve, the majority of the utricle, and the ampullae of the horizontal and anterior semicircular canals.

Which vascular branches arise from the common cochlear artery, and what structures do they supply?

• Main cochlear artery: Supplies the cochlea • Vestibulocochlear artery: Supplies part of the cochlea, the ampulla of the posterior semicircular canal, and the inferior part of the saccule

Which peripheral vestibular structures send afferents through the superior versus inferior vestibular nerves?

• Superior vestibular nerve: Anterior semicircular canal, horizontal semicircular canal, and utricle • Inferior vestibular nerve: Posterior semicircular canal and saccule

What is the function and neural circuitry mediating the Vestibulo-Ocular Reflex (VOR)?

The VOR stabilizes visual images on the retina during head movements by producing eye movements equal in velocity and opposite in direction to head motion. It is mediated by a 3-neuron arc: primary vestibular afferent $\rightarrow$ secondary vestibular efferent (vestibular nuclei) $\rightarrow$ oculomotor motor neuron.

How do the lateral and medial vestibulospinal tracts differ in their site of termination and functional role in postural reflexes?

• Lateral Vestibulospinal Tract (LVST): Originates from the lateral vestibular nucleus and terminates ipsilaterally in the ventral horn of the spinal cord to facilitate alpha and gamma motor neurons to limb extensor muscles. • Medial Vestibulospinal Tract (MVST): Originates from the medial vestibular nucleus and terminates bilaterally in the cervical spinal cord to control neck muscles and maintain head position correlated with eye movements.

Which cranial nerve innervates the skeletal muscles derived from each of the functional pharyngeal arches in human development?

• 1st arch: Trigeminal nerve (CN V) • 2nd arch: Facial nerve (CN VII) • 3rd arch: Glossopharyngeal nerve (CN IX) • 4th arch: Vagus nerve (CN X, superior laryngeal branch) • 6th arch: Vagus nerve (CN X, recurrent laryngeal branch) • Posterior arch: Accessory nerve (CN XI) (Note: The 5th arch does not progress in humans).

What do the six functional components of cranial nerves (GSA, GVA, SA, GSE, GVE, BE) represent?

• GSA: Somatosensory perception of touch, pain, temperature • GVA: Sensory input from viscera • SA: Special senses (smell, taste, vision, hearing, balance) • GSE: Somatic motor innervation to voluntary skeletal muscles • GVE: Autonomic parasympathetic motor innervation to smooth muscle, cardiac muscle, and glands • BE: Branchial motor innervation to skeletal muscles derived from pharyngeal arch mesoderm

Through which cranial foramina do each of the three divisions of the trigeminal nerve (CN V) exit the skull?

• Ophthalmic division ($V_1$): Superior orbital fissure • Maxillary division ($V_2$): Foramen rotundum • Mandibular division ($V_3$): Foramen ovale

Which muscles are innervated by the branchial efferent (BE) motor root of the trigeminal nerve (CN V)?

The four muscles of mastication (temporalis, masseter, medial pterygoid, lateral pterygoid), tensor tympani, tensor veli palatini, anterior belly of digastric, and mylohyoid.

Which cranial nerves exit the cranial cavity through the superior orbital fissure versus the jugular foramen?

• Superior orbital fissure: Oculomotor nerve (CN III), trochlear nerve (CN IV), ophthalmic division of trigeminal nerve ($V_1$), and abducent nerve (CN VI) • Jugular foramen: Glossopharyngeal nerve (CN IX), vagus nerve (CN X), and accessory nerve (CN XI)

What cranial nerve lesion is shown in this diagram, and what causes the characteristic clinical triad?

Oculomotor nerve (CN III) palsy. It presents with ptosis (inactivation of levator palpebrae superioris), mydriasis (decreased pupillary constrictor tone resulting in a dilated pupil), and a "down and out" resting position of the eye (unopposed actions of the lateral rectus and superior oblique muscles).

What nerve lesion is demonstrated by this patient's inability to direct gaze "down and in"?

Trochlear nerve (CN IV) palsy, resulting in paralysis of the superior oblique muscle and inability to look inferiorly when the eye is adducted.

What cranial nerve condition is illustrated here, and what are its key clinical signs?

Bell's palsy (peripheral facial nerve / CN VII palsy). Clinical findings include ipsilateral paralysis of the muscles of facial expression (inability to close the eye, drooping eyelid, flattened nasolabial fold, asymmetrical smile), dry conjunctivae, and altered taste on the anterior two-thirds of the tongue.

What nerve injury produces the tongue atrophy and directional deviation seen in this image?

Hypoglossal nerve (CN XII) lesion. Denervation causes atrophy of the ipsilateral intrinsic and extrinsic tongue muscles and deviation of the tongue toward the affected (lesioned) side upon protrusion.

What clinical findings indicate a lesion of the vagus nerve (CN X)?

Soft palate asymmetry with deviation of the uvula toward the normal (unaffected) side, and vocal cord paralysis resulting in hoarseness.

What are the classic symptoms and common causes of a vestibulocochlear nerve (CN VIII) lesion?

Progressive unilateral hearing loss and tinnitus (ringing in the ear), frequently caused by compressive masses such as a tumor at the cerebellopontine angle.