The Brain Stem

Question 1

In what level of the brain stem do you begin to see coursing together spinothalamic tract and medial lemniscus?

Answer 1

Since middle pons

*below that level they course separated

Question 2

The only muscle that XI CN innervates

Answer 2

Stylopharyngeus

Question 3

What muscles of the pharynx and palate for swallowing are not innervated by X CN?

Answer 3

• tensor palati (V) - palate

- Stylopharyngeus (IX) - pharynx

Question 4

What intrinsic muscle of the tongue is not innervated by XII CN? What innervates it?

Answer 4

• palatoglosus (X)

Question 5

What structure allow you to know that you are in the medulla?

Answer 5

The olives - convoluted inferior olivary tract

Question 6

What is the lateral lemniscus? What information does it carry?

Answer 6

• ascending auditory pathway

- fibers from both cochlear nuclei to the inferior colliculus of the midbrain

Question 7

What is the difference between innervation from UMN to cranial nerves and spinal nerves through corticobulbar and corticospinal tract respectively?

Answer 7

• UMN innervation of LMN in spinal nerves is contralateral

- UMN innervation of LMN in cranial nerves is bilateral (exception VII CN - partially bilateral)

Question 8

How do you expect to find the clinical presentation in a facial nerve lesion vs corticobulbar (central lesion)? Why?

Answer 8

• facial nerve lesion (bell palsy) ▶️ all facial muscles paralysis
• corticobulbar lesion ▶️ contralateral muscles of mouth paralysis, upper face division is spare
• because innervation of UMN to LMN of VII CN is not totally bilateral, for the LMN of the mouth muscles is just contralateral.

Question 9

What is the function of the tensor tympani and stapedius (skeletal muscles)? Who innervates them?

Answer 9

• contract to prevent damage of the inner ear when the ear is exposed to loud sounds
• stapedius (VII), tensor tympani (V3)

Question 10

What auditive symptom may cause a lesion in facial nerve at brain stem or temporal bone (bell palsy)?

Answer 10

Hyperacusis

*stapedius not offer protection against loud sounds

Question 11

What structures are affected when patient have bilateral sensorineural hearing loss?

Answer 11

• auditory structures in brain stem, thalamus, or cortex

* hearing loss bilateral and decreased ability to localize sound source

Question 12

What structures are affected in bilateral sensorineural hearing loss?

Answer 12

• VIII CN, cochlear nuclei in pons, damage of cochlea

Question 13

How do you differentiate sensorineural and obstructive hearing loss?

Answer 13

• sensorineural: air conduction>bone conduction
• obstructive: bone conduction>air conduction
• apply rinne and Weber tests to differentiate

Question 14

What is the cause of internuclear Ophtalmoplegia? How do you distinguish from oculomotor lesion? Common pathology associated

Answer 14

• medial longitudinal fasciculus lesion ▶️ inability to adduct one eye on attempted gaze to the opposite side
• convergence intact, abducted eye exhibits nystagmus
• multiple sclerosis (bilateral MLF lesion)

Question 15

What is the clinical presentation if a lesion at PPRF center occur?

Answer 15

• “lateral gaze paralysis” - inability to look to the lesion site
• ipsilateral complete facial paralysis ▶️ VII nerve loop over VI nucleus
• abducens nucleus coexist with PPRF ▶️ center for ipsilateral horizontal gaze

Question 16

What additional signs can you have as useful to identify and differentiate a cortical lesion (including brodman 8) that cause neither eye can look to one side?

Answer 16

• slow drift to the opposite side asked to move the eyes

- contralateral lower face weakness and upper limb weakness (cortical zones with UMN for that regions of the body too)

Question 17

What can a vestibular nuclei or nerve lesion produce?

Answer 17

• vestibular nystagmus: slow deviation of the eyes toward the lesion side and a fast correction back to the normal side, opposite of lesion side (cortex response)

Question 18

What is the cause of Meniere disease? Sign and symptoms?

Answer 18

• distention of the fluid spaces in the cochlear and vestibular parts of the laberynth
• abrupt, recurrent attacks of vertigo (minutes to hours), tinnitus deafness, (usually one ear), nausea and vomiting.

Question 19

Which are the gaze centers to control the horizontal gaze?

Answer 19

• frontal eye field (brodmann 8) ▶️ contralateral horizontal gaze control
• paramedian pontine reticular formation (PPRF) ▶️ ipsilateral horizontal gaze control

Question 20

Why do we have vestibular symptoms as nystagmus in lateral medullary syndrome (Wallenberg)?

Answer 20

Lesion in vestibular nueclei and pathways

Question 21

Cause of medial midbrain (Weber) syndrome? Structures involved. Some symptoms.

Answer 21

• occlusion do branches of posterior cerebral artery
• CN III, corticobulbar and corticospinal tract
• mydriasis, ptosis?, external strabismus, accommodation affected, contralateral spastic paresis, lower face weakness.

Question 22

Cause of dorsal midbrain (Parinaud) syndrome? Structures involved. Some symptoms.

Answer 22

• pineal tumor compressing superior colliculi
• paralysis upward or vertical gaze, bilateral pupillary abnormalities, ⬆️ intracranial pressure, noncommunicating hydrocephalus if compress cerebral aqueduct

Question 23

Functions of reticular formation

Answer 23

• coordinate and integrate the actions of different parts of the CNS
• regulation muscle and reflex activity, control respiration, cardiovascular responses, behavioral arousal and sleep

Question 24

What is the jugular foramen (vernet) syndrome? Signs.

Answer 24

Lesion of jugular foramen ▶️ dysfunction of CN IX, X, XI

dysphagia, hoarseness, loss of gag reflex ipsilateral, uvula deviation toward normal side