Cranial Nerves XI and XII + Brainstem Blood Supply

List the Cranial Nerves and their associated Foramina

1. Olfactory - Cribiform Plate

2. Optic - Optic Canal

3. Oculomotor - Superior Orbital Fissure

4. Trochlear - Superior Orbital Fissure

5. Trigeminal

   • Opthalmic - Superior Orbital Fissure

   • Maxillary - Foramen Rotundum

   • Mandibular - Foramen Ovale

6. Abducens - Superior Orbital Fissure

7. Facial - Internal Acoustic Meatus

8. Vestibulocochlear - Internal Acoustic Meatus

9. Glossopharyngeal - Jugular Foramen

10. Vagus - Jugular Foramen

11. Accessory - Jugular Foramen

12. Hypoglossal - Hypoglossal Canal

List the Cranial Nerves and their associated Function (Motor or Sensory)

1. Olfactory - Sensory

2. Optic - Sensory

3. Oculomotor - Motor

4. Trochlear - Motor

5. Trigeminal - Both

6. Abducens - Motor

7. Facial - Both

8. Vestibulocochlear - Sensory

9. Glossopharyngeal - Both

10. Vagus - Both

11. Accessory - Motor

12. Hypoglossal - Motor

Accessory Nerve (CN XI) - Location of nerve and nuclei, innervations

• Nerve Location: Upper Cervical Segments C1 - C4/5

• Nuclei Location:

  • Nucleus Ambiguus: Caudal medulla within the reticular formation (hard to see)

  • Spinal Accessory Nucleus: Upper cervical cord and spinomedullar junction, located where normally the ventral horn would be

    • Synapse with UMNs from Corticobulbar Tract (bilateral)

Accessory Nerve (CN XI) - Function

• Function: MOTOR

  • Nucleus Ambiguus: Muscles of the pharynx for speech and swallowing

  • Spinal Accessory Nucleus: SCM and Trapezius motor function

What are some signs of an Upper or Lower motor neuron lesion affecting the Accessory nerve or nucleus?

• UMN lesion: Damage to a Corticobulbar Tract does not cause many issues, due to bilateral input from the other side

• LMN lesion: Damage to the Accessory nerve or its nuclei can lead to ipsilateral LMN lesion symptoms

  • Flaccid paralysis

  • Atrophy

  • Fasiculations

  • Only affecting SCM and Trapezius

• SCM damage:

  • Poor flexion of the neck (head usually tilts contralaterally to damage)

  • Poor rotation away from lesion

• Trapezius damage:

  • Difficulty raising arm above head due to poor scapular rotation

  • Ipsilateral dropped shoulder

  • Winged scapula

Hypoglossal Nerve (CN XII) - Location of nerve and nuclei, innervations

• Nerve Location: Medial medulla between the olives and pyramids

• Nuclei Location:

  • Hypoglossal Nucleus: Medulla, near the midline and superior to the medial longitudinal fasiculus

Hypoglossal Nerve (CN XII) - Function

• Function: MOTOR

  • Hypoglossal Nucleus: All intrinsic tongue muscles and most extrinsic tongue muscles (except palatoglossus - CN X)

What are some signs of an Upper or Lower motor neuron lesion affecting the Hypoglossal nerve or nucleus?

• UMN lesion: Corticobulbar tract damage will lead to few symptoms due to bilateral input

  • However, genioglossus (involved with protruding the tongue) has unilateral innervation

  • Hence, tongue deviates to paralysed side when protruded as genioglossus undergoes atrophy and flaccid paralysis

• LMN lesion: Damage results in ipsilateral atrophy, paralysis and fasciculations of all tongue muscles

  • Tongue deviates to paralysed side when protruded

Name each of the main arteries in the posterior circulation chain

From Rostral to Caudal:

1. Posterior medial and lateral branches

2. Posterior Cerebral Artery

3. Superior cerebellar Arteries

4. Pontine Arteries

5. Labyrinthine Artery (not needed)

6. Basilar Artery

7. Anterior Inferior Cerebellar Artery

8. Vertebral Artery

9. Anterior Spinal Artery

10. Posterior Inferior Cerebellar Artery

11. Posterior Spinal Artery

What are the arteries involved with the blood supply for the Medulla?

• Anterior and Posterior Spinal Arteries:

  • Branch off the vertebral artery to supply the anterior and posterior medulla respectively

  • Also supply respective regions of the spinal cord

• Vertebral Arteries:

  • Supply the lateral aspect of the Medulla

• Posterior Inferior Cerebellar Arteries

  • Branch off the vertebral artery at rostral medulla to supply the posterior-lateral aspect of the rostral medulla

What are the arteries involved with the blood supply for the Pons?

• Basilar Artery: Gives rise to Pontine Arteries

• Pontine Arteries:

  • Supplies medial and lateral pons

• Anterior Inferior Cerebellar Arteries:

  • Branch off the basilar artery at the level of the caudal pons to supply the posterior-lateral aspect of caudal-to-mid pons

• Superior Cerebellar Arteries:

  • Branch of the basilar artery at the rostral pons level to supply posterior-lateral region of rostral pons

What are the arteries involved with the blood supply for the Midbrain?

• Posterior Cerebral Artery: Gives rise to medial and lateral branches

  • Posterior-medial branches supply medial aspect of midbrain

  • Posterior-lateral branches supply lateral aspect of midbrain

  • Collicular branches supply the posterior aspect of the midbrain

  • PCA continue posteriorly to supply occipital lobe

What are the clinical presentations that might be seen by damage to the Vertebral artery

Main arterial output to the posterior circulatory system. Damage could be life threatening

What are the clinical presentations that might be seen by damage to the Anterior Spinal Artery

Medial Medullary Syndrome

• Hypoglossal nucleus: Ipsilateral tongue atrophy and paralysis, deviation to side of damage

• Medial lemniscus: contralateral body loss of fine touch, vibration and conscious proprioception

• Corticospinal tract: contralateral body muscle weakness/paralysis

What are the clinical presentations that might be seen by damage to the Posterior Spinal Artery

Ipsilateral body loss of fine touch, vibration and conscious proprioception sensations

• Carries fibres from cuneate and gracile fasiculi and/or nuclei

  • These fasiculi cross AFTER reaching the medial lemniscus

What are the clinical presentations that might be seen by damage to the Posterior Inferior Cerebellar Artery

Lateral Medullary Syndrome:

• Vestibular nuclei: Nystagmus (repetitive eye movements) and vertigo (dizziness)

• Nucleus Ambiguus (CNXI) : Difficulty speaking (dysarthria), and difficulty swallowing (dysphagia)

• Cuneo & Spinocerebellar tracts and cerebellum: Ipsilateral loss of motor coordination (ataxia)

• Spinal trigeminal nucleus and tract: Ipsilateral loss of pain and temperature in face

• Spinothalamic tract - contralateral body loss of pain and temperature sensations

What are the clinical presentations that might be seen by damage to the Anterior Inferior Cerebellar Artery

• Vestibular nuclei: Nystagmus (repetitive eye movements) and vertigo (dizziness)

• Cerebellum: Ipsilateral loss of motor coordination (ataxia), nystagmus and vertigo

• Spinal & Principal Trigeminal nuclei: Ipsilateral face loss of pain and temperature & fine touch and vibration, respectively

What are the clinical presentations that might be seen by damage to the Superior Cerebellar Artery

Cerebellum: Ipsilateral loss of motor coordination (ataxia), nystagmus and vertigo

What are the clinical presentations that might be seen by damage to the Pontine Arteries

Motor Nuclei and Tracts

• Abducens nucleus: Ipsilateral eye loss of abduction

• Facial motor nucleus: Paralysis to entire ipsilateral side of facial expression muscle

• Trigeminal motor nucleus: Paralysis of ipsilateral muscles mastication

• Pontine nuclei: Contralateral loss of motor coordination (ataxia) *masked by paralysis

• Corticospinal tract: Contralateral body muscle weakness/paralysis (hemiparesis/hemiplegia)

• Corticobulbar tract: Tongue deviation away from the side of the lesion

Sensory Nuclei and Tracts

• Medial lemniscus: Contralateral body loss of fine touch, vibration and conscious proprioception sensations

• Spinothalamic tract: Contralateral body loss of pain and temperature

• Trigeminothalamic tract: Contralateral face loss of pain and temperature, & fine touch and vibration

What are the clinical presentations that might be seen by damage to the Posterior Cerebral Artery

Weber’s Syndrome: hemianaesthesia, loss of vision, and paralysis on contralateral side of body

• Oculomotor & Edinger Westphal nuclei: Ipsilateral eye “down and out” deviation, dilated pupil, closed eyelid, (ptosis), difficulty focusing

• Occipital lobe - Loss of vision

Sensory tracts - contralateral loss of all sensation from body and face (hemianesthesia)

• Medial lemniscus

• Spinothalamic

• Trigeminothalamic

Cerebral peduncle (motor tracts)

• Corticobulbar tract - paralysis to contralateral side lower quarter of face (i.e. below the eye), tongue deviation away from side of the lesion

• Corticospinal tract - contralateral body muscle weakness/paralysis (hemiparesis/hemiplegia)

• Corticopontine tract - contralateral ataxia *masked by paralysis