Brainstem

Question 1

Which cranial nerves are different?

Answer 1

Olfactory cranial
Optic nerve
Direct outgrowth of brain, share same structure as CNS, myelinated so not similar to peripheral nerves

Question 2

Describe the Oculomotor nerve function (3)

Answer 2

Motor
oculomotor nucleus in midbrain (LMN), innervates most extra-ocular muscles

Parasympathetic motor
arise from Edinger-Westphal nucleus and pass to the ciliary ganglion. Post-ganglionic fibres innervate the pupil (constrict).

Question 3

What are the consequences of damage to the oculomotor nerve?

Answer 3

Damage results in the ipsilateral eye being deviated downward and laterally (“down and out”), ptosis (eyelid droops), and a fixed dilated pupil (no parasympathetic innervation)
May be damaged in raised intracranial pressure with tentorial herniation, or disorders involving the cavernous sinus. Trauma around orbit

Question 4

What are the muscles involved in eye movement control?

Answer 4

• Superior and inferior oblique

- Superior, inferior, lateral and medial rectus

Question 5

Which eye muscles does the oculomotor nerve not innervate?

Answer 5

• Superior oblique

- Lateral rectus

Question 6

Where are the oculomotor nerves in the brainstem?

Answer 6

LMN = Close to periaqueductal grey matter
Parasympathetic= Edinger-Westphal nucleus

Question 7

Describe the Trochlear nerve function (4)

Answer 7

Only cranial nerve to arise from the dorsal surface of the brainstem.
Motor
Supplies the superior oblique muscle

Question 8

What is the consequence of damage to the trochlear nerve?

Answer 8

Damage results in diplopia (double vision) when looking downward and medially (direction globe moves when sup. oblique contracts).

Question 9

Where does the Trochlear nerve arise?

Answer 9

Trochlear nucleus

Question 10

Describe the Abducens nerve function (6)

Answer 10

Motor

supplies the lateral rectus muscle

Question 11

What are the consequences of damage to the abducens nerve?

Answer 11

Damage results in diplopia when looking laterally.

Question 12

Where do the abducens fibres arise?

Answer 12

Upper pons

Question 13

Describe the Trigeminal nerve motor function (5)

Answer 13

Motor supply
Supplies the skeletal muscles of mastication which all develop from the first branchial arch. Fibres arise from the trigeminal motor nucleus and join the mandibular division of the trigeminal nerve

Question 14

Describe the Trigeminal nerve sensory function

Answer 14

the trigeminal ganglion is the equivalent of a dorsal root ganglion and receives sensory input from three branches; ophthalmic, maxillary and mandibular. There are three sensory nuclei;
mesencephalic; proprioception from jaw
chief sensory nucleus and spinal nucleus
Fibres decussate and pass to thalamus.

Question 15

Describe the trigeminothalamic pathway

Answer 15

• Pressure and temperature and pain pass into the brainstem trigeminal nuclei
• Proprioception= mesencephalic nucleus
• Head to ventral posterior nuclei of thalamus

Question 16

What is the Cavernous sinus?

Answer 16

This is a dural venous sinus in the middle cranial fossa.
The III, IV, V (ophthalmic and maxillary) and VI nerves all lie in relation to the sinus.
Either side of the pituitary fossa

Question 17

What is cavernous sinus syndrome?

Answer 17

The “cavernous sinus syndrome” will give rise to variable ocular palsies and upper trigeminal sensory loss.
Caused by trauma, neoplasia, thrombosis, inflammatory conditions.

Question 18

Describe the motor functions of the facial nerve (7)

Answer 18

supplies the muscles of facial expression which develop from the second branchial arch, and stapedius, stylohyoid and part of digastric

Question 19

Describe the parasympathetic motor functions of the facial nerve

Answer 19

pre-ganglionic fibres arise in the sup. salivatory nucleus and pass to;
pterygopalatine ganglion (lacrimal gland)
submandibular ganglion (submandibular and sublingual salivary glands)

Question 20

Describe the sensory functions of the facial nerve

Answer 20

cutaneous sensory information from the external ear. 1st order neurones lie in the geniculate ganglion (middle ear) and axons pass to the spinal trigeminal nucleus.

Question 21

Describe the special sensory functions of the facial nerve

Answer 21

the chorda tympani nerve innervates (taste) the anterior 2/3rds of the tongue. 1st order neurones lie in the geniculate ganglion (middle ear) and pass to the nucleus solitarius (also receives fibres from IX and X).

Question 22

What are the consequences of damage to the facial nerve?

Answer 22

Conditions affecting VIIth nerve include;
Bell’s palsy; unilateral facial paralysis
Geniculate herpes zoster (vesicles in ear drum)
UMN lesion- upper facial muscles are relatively well preserved due to bilateral innervation of the facial nucleus.
LMN lesion- paralysis of both upper and lower facial muscles.

Question 23

Where do facial nerve fibres arise?

Answer 23

• Facial nucleus

- Pons

Question 24

Describe the special sensory functions of the vestibulocochlear nerve (8)

Answer 24

sensory information relating to hearing (cochlear nerve) and balance (vestibular nerve). 1st order neurones in the vestibular and cochlear ganglia pass to vestibular (4) and cochlear nuclei (2) in the medulla.

Question 25

What are the symptoms of vestibulocochlear nerve damage?

Answer 25

deafness, tinnitus | dizziness, vertigo

Question 26

What are the conditions involving the vestibulocochlear nerve?

Answer 26

Acoustic schwannoma labyrinthitis Meniere’s disease

Question 27

Describe the motor functions of the glossopharyngeal nerve (9)

Answer 27

fibres arise from the nucleus ambiguus and innervate a single pharyngeal muscle which arises from the third and fourth branchial arches (stylopharyngeus).

Question 28

Describe the parasympathetic motor functions of the glossopharyngeal nerve

Answer 28

fibres arise from the inf. salivatory nucleus and pass to the otic ganglion, from where post-ganglionic fibres innervate the parotid gland

Question 29

Describe the sensory functions of the glossopharyngeal nerve

Answer 29

provides sensory information from the pharynx, posterior 1/3rd of the tongue and the middle ear. 1st order neurones lie in the ganglion and pass to the trigeminal sensory nucleus. Important in the gag reflex.

Question 30

Describe the special sensory functions of the glossopharyngeal nerve

Answer 30

taste information passes from posterior 1/3rd of the tongue and the pharynx to the nucleus solitarius. information from the carotid body and carotid sinus passes to the nucleus solitarius.

Question 31

Describe the motor functions of the vagus nerve (10)

Answer 31

fibres arise from the nucleus ambiguus and innervate muscles of the soft palate, pharynx, larynx and oesophagus which arises from the third and fourth branchial arches . Important in swallowing and speech

Question 32

Describe the parasympathetic functions of the vagus nerve

Answer 32

fibres arise from the dorsal motor nucleus and pass to a number of ganglia within the cardiovascular, respiratory and gastrointestinal systems.

Question 33

Describe the sensory functions of the vagus nerve

Answer 33

provides sensory information from the pharynx, larynx, tympanic membrane and part of outer ear. 1st order neurones lie in the ganglion and pass to the trigeminal sensory nucleus. Important in the gag reflex.

Question 34

Describe the special sensory functions of the vagus nerve

Answer 34

taste information passes from the pharynx to the nucleus solitarius. information from the aortic body and aortic arch passes to the nucleus solitarius.

Question 35

Describe the motor functions of the accessory nerve (11)

Answer 35

LMN’s are in the nucleus ambiguus and in the anterior horn of the upper cervical cord. They innervate trapezius and sternomastoid. Shrug shoulders

Question 36

What nerves does swallowing involve?

Answer 36

9 and 10 | Parasympathetic fibres through vagus nerve

Question 37

What nerves foes sneezing involve?

Answer 37

9 10 11 and 5 | Spinal reflexes in lower spinal cord

Question 38

What is the jugular foreamen?

Answer 38

The lower cranial nerves (IX, X, XI) may all be affected at the base of the skull (jugular foramen) by tumour, trauma or an inflammatory process. XII leaves the skull via the hypoglossal foramen and is only affected by large tumours

Question 39

Describe the motor functions of the hypoglossal nerve

Answer 39

This innervates both the extrinsic and intrinsic muscles of the tongue. LMN’s are in the hypoglossal nucleus. Unilateral lesions result in weakness and atrophy of the tongue on the affected side. When protruded the tongue deviates towards the affected side.

Question 40

Describe Bulbar and pseudobulbar palsy

Answer 40

Bulbar refers to the motor nuclei of the brainstem (strictly the medulla[“bulb”]). Corticobulbar fibres pass from the cortex to brainstem nuclei. As with elsewhere in the motor system there are UMN (pseudobulbar) and LMN (bulbar) lesions. =Bulbar (LMN); atrophy and fasciculation of the innervated muscles. =Pseudobulbar (UMN); usually have to be bilateral lesions due to bilateral innervation. Exaggerated reflexes (jaw) and spastic paresis of the tongue. =Dysphonia, dysphagia and dysarthria are seen in both. Bulbar palsies are most commonly seen in MND (chronic) and Guillain-Barre (acute). Pseudobulbar palsies are most commonly seen in vascular disease and demyelination.

Question 41

What are the other components of the brainstem?

Answer 41

-Reticular formation =Periaqueductal grey matter (midbrain) has ascending arousal pathways, and descending pain suppression pathways -Autonomic control centres =Cardiovascular =respiratory -Ascending and descending white matter pathways

Question 42

What is the Reticular activating system?

Answer 42

-Thalamus (cortical activation, sleep spindle) -Input from hypothalamus (sleep/wake switch) =Deactivation= coma