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► Med - Neuroanatomy > Exam #3: Lesions I > Flashcards

Exam #3: Lesions I Flashcards

1
Q

What three structures are part of the cerebral peduncle in the rostral midbrain?

A

1) Tegmentum
2) SN
3) Basis Pedunculi

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2
Q

What does the MLF connect?

A

CN III, IV, VI in the caudal midbrain

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3
Q

What is the only CN to cross in the midbrain?

A

Trochlear nerve

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4
Q

Where is the decussation of the SCP?

A

Caudal midbrain

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5
Q

What artery supplies the corticospinal & corticonuclear tracts in the midbain basis pedunculi?

A

PCA

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6
Q

What arteries supply the midbrain?

A

Branches of the PCA

Superior Basilar a.

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7
Q

What specific artery supplies the corpora quadrigemi?

A

Quadrageminal a. which is a branch of the PCA

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8
Q

What is the eponym for Medial Midbrain Syndrome?

A

Weber Syndrome

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9
Q

What is the eponym for Central Midbrain Syndrome?

A

Claude Syndrome

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10
Q

What is the eponym for Medial Midbrain + Central Midbrain Syndrome?

A

Benedict Syndrome

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11
Q

What is the general pattern of midbrain lesions?

A
  • Oculomotor nerve palsy IPSILATEAL

- All of the other deficits (hemiparesis) are CONTRALATEARAL

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12
Q

Where is the lesion in Medial Midbrain Syndrome (Weber)?

A

Rostral Midbrain Basis i.e. the base (ventral) portion of the rostral midbrain

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13
Q

What structure are involved in Medial Midbrain Syndrome?

A

Oculomotor n.
Corticospinal
Corticonuclear

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14
Q

What is the presentation of Medial Midbrain Syndrome in relation to the eye? Explain the presentation to the associated muscles that are paralyzed b/c of the lesion.

A

IPSILATERAl CN III palsy=

  • Ptosis (levator palpebrae superioris)
  • Lateral strabismus/ horizontal diplopia (medial rectus + LR & SO)
  • Vertical diplopia (superior & inferior rectus)
  • Mydriasis (PNS sphincter pupillae)
  • No accomodation of the lens (PNS ciliary muscle)
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15
Q

With a CN III lesion on the LEFT, which eye will constrict with light shined in the RIGHT eye? What about left?

A 
Afferent= CN II 
Efferent= CN III (PNS)

RIGHT eye only

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16
Q

What type of corticonuclear projections does the trigeminal nucleus generally receive? What is the exception?

A

Generally, CN V motor nucleus receives BILATERAL UMN projections
- EXCEPTION= lateral pterygoid m. that receives CONTRALATERAL UMN projections only

17
Q

What is a presentation of a lesion to the trigeminal nucleus e.g. if there is a lesion to the midbrain, what will the presentation be?

A

Corticonuclear tracts to the RIGHT lateral pterygoid m. (muscle of mastication) come from the LEFT. The manifestation of a lesion is mandible deviation.

Thus, LEFT midbrain lesion= mandible deviation to the RIGHT (weak side)

18
Q

What type of projections does the facial nucleus receive?

A

Upper Facial Nucleus= bilateral UMN

Lower Facial Nucleus= contralateral UMN ONLY

19
Q

What type of projections does the nucleus ambiguus receive?

A

Primarily CONTRALATERAL projections

20
Q

What muscle is controlled by the nucleus ambiguious? What structure does this muscle control? If there were a lesion in the LEFT midbrain, what would the expected presentation be?

A
  • Musculous uvulae m. controls the uvula
  • Receives CONTRALATERAL UMN projections

Thus, LEFT midbrain lesion will effect the RIGHT nucleus ambiguous. However, with a weak RIGHT musculous uvulae m. the uvula will deviate to the LEFT.

21
Q

What type of projections does the hypoglossus nucleus receive? What is the exception? If there is a LEFT midbrain lesion, what would the expected presentation be?

A

Hypoglossal nucleus receives BILATERAL UMN projections
- EXCEPTION is genioglossus, which receives CONTRALATERAL UMN projections

Thus, LEFT midbrain lesion will effect the RIGHT hypoglossal nucleus; specifically, the genioglossus m. will be effect. Protrusion of the tongue will be to the RIGHT, the weak side.

22
Q

Where do corticospinal tracts decussate?

A

Caudal medulla

23
Q

Describe the presentation Medial Midbrain Syndrome (Weber) with a lesion to the LEFT rostral midbrain.

A

LEFT oculomotor palsy

RIGHT

  • CN V= RIGHT deviation of jaw
  • CN VII= RIGHT weakness of lower face
  • CN X= uvula deviation to the LEFT
  • CN XII= tongue protrusion to the RIGHT
  • Corticospinal tracts= hemiparesis
24
Q

Where is the lesion associated with Central Midbrain Syndrome (Claude Syndrome)?

A

Branches of the PCA & Superior Basilar Artery

25
Q

What structures are effected in Central Midbrain Syndrome (Claude Syndrome)?

A
  • CN III fasicules as they course ventrally (ipsilateral CN III palsy)
  • Red Nucleus
  • Cerebellothalamic fibers
26
Q

Where is the CN III Palsy associated with Central Midbrain Syndrome?

A

IPSILATERAL

27
Q

What is the function of the Red Nucleus?

A

Control of the distal muscles of the upper limb via RUBROSPINAL tract

**However, NOT clinically significant b/c of corticospinal tract (humans)

28
Q

What structures are connected by the cerebellothalamic fibers? Where do cerebellothalamic fibers cross-over?

A

Cerebellothalamic fibers connect the cerebellum to the CONTRALATERAL thalamus

  • After exiting the cerebellum, these fibers ascend the SCP
  • SCP decussates in the caudal midbrain (Mickey Mouse)
29
Q

What is the function of the cerebrothalamic fibers? What is the manifestation of a lesion to the cerebellothalamic fibers?

A

Cerebellothalmic fibers are sensory fibers sending information to the cortex; the cortex then sends impulses back down to the cerebellum to alter movement on the CONTRALATERAL side of the body

Thus, a lesion will cause ataxia and intention tremor on the CONTRALATERAL side of the body

30
Q

Where Benedikt Syndrome the eponym for?

A

Medial + Central Midbrain Syndromes

31
Q

Describe the presentation of Benedikt Syndrome.

A

BOTH= IPSILATERAL CN III Palsy

Medial=

  • Contralateral mandible deviation
  • Contralateral lower facial weakness
  • IPSILATERAL uvula deviation (even though it effects the CONTRALATERAL nucleus ambiguous)
  • Contralateral hemiparesis (corticospinal tracts)

Central=
- Contralateral ataxia & intention tremor

32
Q

What is the additional manifestation of Benedikt Syndrome compared to just the medial & central midbrain syndromes alone??

A

SN lesion= CONTRALATERAL tremor/ involuntary movement at REST

33
Q

What does MS have the most impact on?

A

Heavily myelinated tracts of the CNS

34
Q

Describe the presentation a demyelination lesion to the caudal midbrain caused by MS. What structures will be effected? What will the presentation be?

A

Trochlear nucleus= paralysis of CONTRALATERAL superior oblique–>hypertropia (up & out)

Medial Longitudinal Fasiculus (MLF)= medial rectus= defect in conjugate horizontal movement with ADduction of IPSILATERAL eye

Cerebellothalamic fibers= CONTRALATERAL

  • Intention tremor
  • Dysmetria
  • Dysdiadochokinesia (impaired RAM)

► Med - Neuroanatomy (36 decks)

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