Brainstem

Question 1

Which cranial nerves exit medially from the brainstem and what feature connects them?

Answer 1

III, IV, VI, XII - all purely motor

Question 2

Which cranial nerves exit laterally from the brainstem and what feature connects them?

Answer 2

V, VII, VIII, IX, X - mixed sensory and motor

Question 3

Where are the cerebral peduncles found, and what separates them?

Answer 3

Ventral surface of the midbrain, separated by the interpeduncular fossa

Question 4

Three types of axons found in the cerebral peduncles and their synaptic destinations

Answer 4

1) corticopontine - pontine nuclei; 2) corticospinal - lower motor neurons of cranial nerves; 3) corticobulbar - lower motor neurons of spinal nerves

Question 5

Which cranial nerve emerges in the interpeduncular fossa?

Answer 5

III (oculomotor) - arises from midbrain

Question 6

Which cranial nerves emerge from the pontomedullary junction?

Answer 6

VI, VII, VIII

Question 7

Which cranial nerve emerges from the rostral pons?

Answer 7

V

Question 8

Where do axons from the pontine nuclei travel?

Answer 8

Through the middle cerebellar peduncle to the cerebellum

Question 9

What two tracts do the medullary pyramids contain?

Answer 9

Corticospinal and corticobulbar

Question 10

Which cranial nerves emerge dorsolateral to the olive?

Answer 10

IX, X

Question 11

Which cranial nerve emerges medial to the olive and lateral to each pyramid?

Answer 11

XII

Question 12

Where are the dorsal column nuclei (nucleus cuneatus and gracilis) located?

Answer 12

Caudal medulla

Question 13

Which is the only dorsally exiting cranial nerve?

Answer 13

IV

Question 14

Which is the only completely crossed cranial nerve?

Answer 14

IV

Question 15

The superior and inferior colliculi are found on the dorsal surface of what?

Answer 15

Midbrain

Question 16

The superior and inferior colliculi serve what function?

Answer 16

Spatial orientation in response to conjugate gaze (superior) and auditory input (inferior)

Question 17

What separates the pons from the cerebellum?

Answer 17

Fourth ventricle

Question 18

A lesion of the corticospinal tract at the level of the basis pontis would result in?

Answer 18

Contralateral UMN symptoms

Question 19

Trace the pathway of the lateral motor system

Answer 19

Corticospinal tract courses ventrally and medially through the brainstem (basis pedunculi in midbrain, basis pontis in pons, pyramid in medulla), decussates in the pyramid, travels in the lateral corticospinal tract of the spinal cord to lateral motor nuclei in the ventral horn

Question 20

Trace the pathway of the medial lemniscal system

Answer 20

Dorsal columns synapse in dorsal nuclei in caudal medulla, axons from nuclei cross immediately as internal arcuate fibers and form the medial lemniscus on contralateral side, medial lemniscus courses medially through the medulla dorsal to the corticospinal tract, then moves dorsally and laterally as it passes through pons and midbrain to ventral posterior lateral nucleus of thalamus

Question 21

A complete lesion of the medial lemniscus in the brain stem results in?

Answer 21

Loss of touch, vibration, and pressure sensations in the upper and lower limb, neck, and trunk contralateral and below the lesion

Question 22

Medial lemniscus moves from _____ to _____ as it ascends the brainstem to the _____ of the thalamus

Answer 22

medial; lateral; ventral posterior lateral nucleus

Question 23

Trace the pathway of the anterolateral system

Answer 23

Peripheral nerve fibers with cell bodies in dorsal root ganglia enter the spinal cord and course in Lissauer’s tract for 1-2 levels, synapse in the substantia gelatinosa of the dorsal horn, decussate in the anterior commissure, run up the spinal cord in the anterolateral pathway as the spinothalamic tract, which runs in the lateral part of the brainstem as it goes to the ventral posterior lateral nucleus of the thalamus

Question 24

The spinothalamic tract gives off the _____ tract in the pons and the _____ tract in the midbrain

Answer 24

spinoreticular; spinomesencephalic

Question 25

A lesion of the spinothalamic tract in the brainstem may result in?

Answer 25

Loss of pain and temperature sensations from the upper and lower limb, neck, and trunk contralateral and below the lesion

Question 26

Descending hypothalamic fibers that innervate preganglionic autonomic neurons course through the brainstem with the _____

Answer 26

spinothalamic tract

Question 27

Trace the path of descending hypothalamic fibers from hypothalamus to spinal cord

Answer 27

Fiber arise in the hypothalamus, course without crossing in the lateral part of the brainstem with the corticospinal tract until they synapse with preganglionic sympathetic and parasympathetic neurons in the brain stem and spinal cord

Question 28

Patients with a lesion of the descending hypothalamic axons of the brainstem may present with what?

Answer 28

Central Horner's syndrome that is always ipsilateral to the side of the lesion. In addition to ptosis, miosis, and anhydrosis of the face and scalp, patients may show loss of pain and temperature sensations in limbs and trunk contralateral to the lesion due to the proximity of the spinothalamic tract

Question 29

Location and function of the medial longitudinal fasciculus

Answer 29

MLF courses through the length of the brainstem in the floor of the 4th ventricle, adjacent to the cerebral aqueduct in the midbrain; MLF functions to link the vestibular nuclei and centers for conjugate gaze with the abducens, trochlear, and oculomotor nuclei (coordinates eye movements)