Brain Stem

Question 1

How do cranial nerves arise from the brain stem?

Answer 1

Motor nerves - medially
Mixed nerves - laterally

From midbrain: 2,3
From pons: 4, 5, 6, 7, 8
From medulla: 9, 10, 12
(11 - from spinal cord)

Question 2

How do tracts pass through the midbrain?

Answer 2

Spinothalamic tract - laterally
Descending hypothalamic tract - laterally
Corticospinal tract - medially and dorsal
Medial Lemniscus - medial (medulla and pons) -> lateral (midbrain)

Question 3

What is Medial Medullary Syndrome?

Answer 3

Anterior Spinal Artery
• Pyramid: contralateral spastic paresis
• Medial lemniscus: contralateral loss of tactile, vibration, conscious proprioception
• XII nucleus/fibers: ipsilateral flaccid paralysis of tongue with tongue deviation on protrusion to lesion side.

Question 4

What is Lateral Medullary Syndrome?

Answer 4

PICA, Wallenberg Syndrome
• Inferior cerebellar peduncle: ipsilateral limb ataxia
• Vestibular nuclei: vertigo, nausea/vomiting, nystagmus (away from lesion)
• Nucleus ambiguus (CN IX, X): ipsilateral paralysis of larynx, pharynx, palate → dysarthria, dysphagia, loss of gag reflex
• Spinal V: ipsilateral pain/temperature loss (face)
• Spinothalamic tract: Contralateral pain/temperature loss (body)
• Descending hypothalamics: ipsilateral Horner syndrome

Question 5

What is Medial Pontine Syndrome?

Answer 5

Paramedian Branches of Basilar Artery
• Corticospinal tract: contralateral spastic hemiparesis
• Medial lemniscus: contralateral loss of tactile/position/vibration
sensation
• Fibers of VI: medial strabismus

Question 6

What is Lateral Pontine Syndrome?

Answer 6

AICA
• Middle cerebellar peduncle: ipsilateral ataxia
• Vestibular nuclei: vertigo, nausea and vomiting, nystagmus
• Facial nucleus and fibers: ipsilateral facial paralysis; ipsilateral loss
of taste (anterior two-thirds of tongue), lacrimation, salivation, and
corneal reflex; hyperacusis
• Spinal trigeminal nucleus/tract: ipsilateral pain/temperature loss
(face)
• Spinothalamic tract: contralateral pain/temperature loss (body)
• Cochlear nucleus/VIII fibers: ipsilateral hearing loss
• Descending hypothalamics: ipsilateral Horner syndrome

Question 7

What is Dorsal Midbrain (Parinaud) Syndrome?

Answer 7

Tumor in Pineal Region
• Superior colliculus/pretectal area: paralysis of upward gaze, various pupillary abnormalities
• Cerebral aqueduct: noncommunicating hydrocephalus

Question 8

What is Medial Midbrain (Weber) Syndrome?

Answer 8

Branches of PCA
• Fibers of III: ipsilateral oculomotor palsy (lateral strabismus, dilated pupil, ptosis)
• Corticospinal tract: contralateral spastic hemiparesis
• Corticobulbar tract: contralateral hemiparesis of lower face