11_Brainstem Lesions_Q and A_Jonathan

Question 1

Intro: • brain pathology usually leads to inactivation of function. Exception: illnesses like seizures which overactivate brain functions
• Most brain pathology is centered around one location. Example: stroke or tumor. Exception: illnesses like MS which produce scattered lesions and unrelated symptoms

Answer 1

• brain pathology usually leads to inactivation of function. Exception: illnesses like seizures which overactivate brain functions
• Most brain pathology is centered around one location. Example: stroke or tumor. Exception: illnesses like MS which produce scattered lesions and unrelated symptoms

Question 2

If there are signs and symptoms that involve cranial nerves on one side of the face/body and signs and symptoms on the other side of the body, not related to cranial nerves, where might the lesion be? Why?

Answer 2

• brain stem
o most cranial nerves in the brainstem connect to the same side of the face
o most nerve tracts from the body cross in the brainstem

Question 3

Assuming brainstem (one side of face, opposite side of body), if the symptoms involve motor cranial nerves and weakness in the body, where might the lesion be?
What are exceptions?

Answer 3

• medial brain stem

* exceptions are: facial, vagus, and mastication which may be lateral brainstem lesion

Question 4

Assuming brainstem (one side face, opposite side body), if the symptoms involve sensory cranial nerves and loss of pain or temperature sensation in the body, where might the lesion be?

Answer 4

• lateral brainstem
• These are in the Alar plate
• Note: sensory cranial nerves includes special sense as well as other senses like vestibular system

Question 5

Assuming brainstem, where might the lesion be with regard to inferior-superior axis? What are the exceptions? (exceptions listed separately next)

Answer 5

• the vertical level of the lesion is at the level of the cranial nerve nucleus and/or its exit from the brain.
• Loss of facial pain and temperature sensation ==> lesion is in spinal trigeminal tract/nucleus in the lateral medulla
o This runs longitudinally through the medulla
• Weakness in the lower face, with preservation of forehead function, ==> this is above the pons on the contralateral side in the coritcobulbar tract

Question 6

If you have loss of facial pain and temperature sensation, where is the lesion?

Answer 6

• lesion is in spinal trigeminal tract/nucleus in the lateral medulla
o This runs longitudinally through the medulla

Question 7

If the weakness is in the lower face with preservation of the forehead function, where is the lesion? (note: this is important to distinguish stroke from Bell’s Palsy)

Answer 7

• this is above the pons on the contralateral side in the coritcobulbar tract

Question 8

Note: when dealing with long tracts of nerves, location may not be able to be determined dependent exclusively on symptoms.

Answer 8

Note: when dealing with long tracts of nerves, location may not be able to be determined dependent exclusively on symptoms.

Question 9

What long tract is loss of vibratory sense, joint position sense, and well-localized touch and pressure related to?

Answer 9

• medial lemniscus pathway

* Note: “pathway means more than one neuron. It is a multi-step pathway.”

Question 10

What is an indication of the inferior-superior location of the lesion in the dorsal columns?

Answer 10

• ipsilateral columns in the caudal medulla

* contralateral above the decussation

Question 11

What long tract is loss of pain and temperature on the contralateral side of the body related to? Where is it located?

Answer 11

• Spinalthalamic tract aka Anterolateral System (called ALS)
• Lateral brainstem and anterolateral cord
• Note: this tract decussates the spinal cord at the level of vertebral entry to the spinal cord

Question 12

What is an indication of thalamic lesions?

Answer 12

• production of loss of ALL sensations on the contralateral side of the body

Question 13

What is the course of the Corticospinal Tract? Are these ascending or descending?

Answer 13

• posterior limb of the internal capsule ==> cerebral peduncle ==> base of pons ==> medullary pyramid ==> pyramidal decussation
• Note: damage to this tract is a common cause of “upper motor neuron” pathology
o Muscle weakness, but reflexes are intact
o Pathological reflexes

Question 14

What are the corticobulbar fibers?

Answer 14

• These are fibers going from the cortex to the brainstem

* They are controlling

Question 15

What is the course of the corticobulbar tract? (ppt said we must know this) (long answer)

Answer 15

• originates in motor cortex of the frontal lobe, just superior to the lateral fissure and rostral to the central sulcus.
• descends through the genu of the internal capsule and a few fibers in the posterior limb of the internal capsule, as it passes from the cortex down to the midbrain.
• In the midbrain, the internal capsule becomes the cerebral peduncles.
• The white matter is located in the ventral portion of the cerebral peduncles, called the crus cerebri.
• The middle third of the crus cerebri contains the corticobulbar and corticospinal fibers.
• The corticobulbar fibers exit at the appropriate level of the brainstem to synapse on the lower motor neurons of the cranial nerves.

Question 16

What is the course of the corticobulbar tract? (short answer)

Answer 16

• motor cortex frontal lobe, superior to the lateral fissure and rostral to the central sulcus ==>
• genu of the internal capsule and a few fibers in the posterior limb of the internal capsule ==> midbrain
• internal capsule ==> the cerebral peduncles ==> crus cerebri ==> leave brainstem to synapse on the lower motor neurons of the cranial nerves.

Question 17

What are some features of damage to the corticobulbar fibers?

Answer 17

• contralateral lower face: weakness in the tongue and soft palate

Question 18

What is the hypothalamospinal system?
Where are nerves in this system found?
What syndrome is associated with the hypothalamospinal system? (wiki)

Answer 18

• connects the thalamus to the ciliospinal center of the intermediolateral cell column in the spinal cord (T1, T2).
• It is found in the dorsolateral quadrant of the lateral funiculus, in the lateral tegmentum of the medulla, pons and midbrain. Lesions of the hypothalamospinal tract cause ipsilateral Horner’s syndrome.
• Lesions of the posterior inferior cerebellar artery (PICA) lead to the so called lateral medullary syndrome, with ipsilateral Horner’s Syndrome as the result of lesioning this nucleus.

Question 19

What is the hypothalamospinal system? (from class)

Answer 19

• it is a descending sympathetic control system
• it is one of the few tracts that is only ipsilateral
• It is found on the ipsilateral brain stem and spinal cord

Question 20

In the cerebellar system, in what side of the body does damage to the peduncles produces symptoms?

Answer 20

• Damage to the peduncles produces ipsilateral symptoms

* In general, cerebellar damage affects the ipsilateral side

Question 21

Explain when and how cerebellar symptoms can occur on the contralateral side.

Answer 21

• cerebellum ==> superior cerebellar peduncle ==> midbrain ==> motor cortex
• At some point must cross ==> crossing occurs in the caudal midbrain
• The superior cerebellar peduncle produces ipsilateral symptoms below the middle part of the midbrain.
• Contralateral symptoms from the red nucleus up to the VL of the thalamus
• Contralateral symptoms can also occur from damage to the pons (pontine nuclei project to the contralateral cerebellum)

Question 22

What side do cerebellar symptoms occur if there is damage to the pons? The middle cerebellar peduncle?

Answer 22

• pons ==> contralateral and/or ipsilateral symptoms
o contralateral ==> ponine nuclei that project to the contralateral cerebellum
o ipsilateral symptoms ==> damage to the middle cerebellar peduncle

Question 23

What is exclusionary of cerebellar damage?

Answer 23

• if a limb is very weak, there is no cerebellar symptoms in that limb

Question 24

What nerves are associated with…
Midbrain?
Pons?
Medulla?
Cervical spinal cord?

Answer 24

Midbrain ==> CN III, CN IV
Pons ==> CN V, CN VI, CN VII, CN VIII
Medulla ==> CN IX, CN X, CN XII
Cervical spinal cord ==> CN XI

Question 25

Note: “centers” in the midbrain and pons are involved in eye movement control

Answer 25

Note: “centers” in the midbrain and pons are involved in eye movement control

Question 26

Note: the visceral are closest to the sulcus limitans between the alar and basal plate

Answer 26

Note: the visceral are closest to the sulcus limitans between the alar and basal plate

Question 27

What functions are affected by the spinal nucleus/tract of the trigeminal (spinal V)?

Answer 27

• somatic sensory nucleus
• pain and temperature
• begins caudal medulla

Question 28

Mid medulla. The hypoglossal nucleus in the mid-medulla is what kind of nerve?

Answer 28

• general somatic motor

Question 29

Mid medulla. The dorsal motor nucleus of the vagus (DMX) is what kind of nerve fiber?

Answer 29

• general visceral motor (parasympathetic)

Question 30

Mid medulla. The Solitary Nucleus aka Nucleus Tractus Solitarius (NTS) is what kind of nerve fiber?

Answer 30

• general visceral sensation and special visceral afferent (taste)

Question 31

Mid medulla. What kind of nerve fiber is the vestibular nucleus (lateral brainstem in the alar plate)?

Answer 31

• special somatic sensory (vestibular cochlear)

Question 32

Mid Medulla. What kind of nerve fiber is the nucleus ambiguous?

Answer 32

?

Question 33

Caudal Pons. Explain the relationship of the facial nucleus and the abducens nucleus in the facial colliculus. What kind of nerve fibers are each?

Answer 33

• both the facial nuclei and the abducens nuclei are found in the facial colliculus.
• The facial nerve wraps around the abducens nucleus to make the facial colliculus
• Facial nerve ==> ?
• Abducens nerve ==> ?

Question 34

Rostral pons. What are the locations of in the rostral pons and what do each do?
IV?
Motor nucleus of the trigeminal CN V?
Chief Sensory Nucleus of the CN V?

Answer 34

• IV ==> central ==> motor function to the eye
• Motor nucleus of CNV ==> lateral basal plate ==> muscles of mastication
• Chief Sensory Nucleus of the CN V ==> alar plate ==> all sensory functions of CN V terminates here.
o Touch, pressure
• note the spinal nucleus of CN V is pain and temperature only

Question 35

Mesencephalon

Answer 35

• CN III exits the interpeduncular fossa

* Somatic motor nucleus