Exam #3: Lesions II (Pons) Flashcards
How are brainstem lesions localized?
The level of the lesion is localized by the cranial nerve involved
Where are the nuclei for CN III located?
Rostral midbrain
Where are the nuclei for CN VI located?
Caudal pons
Where are the nuclei for CN XII?
Rostral Medualla
What structures will be effected by a lesion to the medial pons?
CN VI*
MLF
Corticospinal/ corticonuclear tracts
Medial lemniscus
What structures will be effected by a lesion to the medial medulla?
CN XII
Pyramids i.e. corticospinal tracts mostly
Medial lemniscus
When there are lesions to the medial brainstem, what is the general pattern of deficits i.e. what is the general pattern to the patient’s presentation?
- IPSILATERAL CN deficits
- CONTRALATERAL long tract signs
*****Note that this is referred to as an “alternating hemiplegia”
What is the clinical syndrome seen when there is a CN III lesion?
Upper alternating hemiplegia
What is the clinical syndrome seen when there is a CN VI lesion?
Middle alternating hemiplegia
What is the clinical syndrome seen when there is a CN XII lesion?
Lower alternating hemiplegia
What tracts are involved in lateral brain stem lesions?
Spinothalamic tract (CONTRALATERAL) Spinal tract of V (IPSILATERAL)
*****Note that both of these tracts are involved in pain & temperature sensation
What CN nuclei are involved in lateral brain stem lesions?
CN V CN VII CN VIII CN IX CN X
Where is the nucleus of CN V located in the brainstem?
Midpons
Where is the nucleus of CN VII located in the brainstem?
Caudal pons
Where is the nucleus of CN VIII located in the brainstem?
Caudal pons & medulla
Where is the nucleus of CN IX located in the brainstem?
Medulla
Where is the nucleus of CN X located in the brainstem?
Medulla
What causes a lesion to the medial rostral pons?
Lesion to the basilar artery, specifically the paramedian branches
What is the expected presentation of a lesion of the basilar artery affecting rostral pons i.e. the medial pontine basis?
*****Dysarthria Hemiparesis Syndrome
1) Corticospinal tract involved will give CONTRALATERAL UE & LE weakness
2) Corticonuclear tract involved will give CONTRALATERAL lower face weakness generally causing dysarthria. The specific muscles involved will be:
- Lateral pterygoid (mandible deviation away from the lesion)
- Musculus uvulae (uvula deviation toward the lesion)
- Genioglossus (tongue deviation away from the lesion)
What is the expected presentation of a lesion to the caudal pons i.e. the medial pontine basis? How would you differentiate this lesion from a lesion to the rostral pons?
*****Ataxic Hemiparesis Syndrome
1) Corticospinal tract involved will give CONTRALATERAL UE & LE weakness
2) Corticonuclear tract involved will give CONTRALATERAL lower face weakness & dysarthria
- Musculus uvulae (uvula deviation toward the lesion)
- Genioglossus (tongue deviation away from the lesion)
* Same as lesion to rostral pons, but the lateral pterygoid is NOT affected i.e. no mandible deviation
New aspect:
- Pontine nuclei/ Transverse pontine (pontocerebellar) fibers–> CONTRALATERAL ataxia
Neurologic examination reveals RIGHT upper & lower limb weakness accompanied by resistance to passive stretch (spasticity), exaggerated tendon reflexes ( hyperreflexia), and extensor plantar response (babinski sign). What tract is affected?
Corticospinal tract
Neurologic exam reveals a loss of 2-point discrimination, vibration, and limb position senses on the RIGHT side in the upper & lower limbs, trunk, and neck. What tract is affected? Where must the lesion be with the presentation described?
DC/ML & must be above the cervical level of the spinal cord
Neurologic exam reveals a loss of pin prick sensation to the right side of the face. What tract is affected?
LEFT trigeminalothalamic tract
A corneal reflex on the RIGHT eye could be elicited from either eye (not the left). What structure is affected?
Left CN VII
Recall,
- CN V= afferent
- CN VII= efferent
Neurologic exam reveals that the left side of the face sags, and the patient is unable to close the left eye or retract the left side of the mouth. What structure is affected?
LMN lesion on the left involving CN VII
Where is the level of the lesion to involved CN VII?
Caudal Pons
A patient’s eyes converged for near vision and she could look up and down, but she could not look to the left and her left eye was medially deviated. In attempting to gaze to the right, the right eye abducted but the left eye did not adduct. What are the structures involved?
Know that CN III is intact
- Left abducens nucleus deficit
- Left MLF
*****One and a half syndrome
What level is a lesion involving the abducens nucleus?
Caudal pons
What cranial nerves are associated with the rostral pons?
None
What cranial nerve is associated with the midpons?
CN V
What cranial nerves are associated with the caudal pons?
CN VI
CN VII
What cranial nerves are associated with the pons/medulla?
CN VIII
What cranial nerves are associated with the medulla?
CN IX, X, XI, XII
What is the facial colliculus?
A “bump” on the floor of the 4th ventricle in the caudal pons formed by the facial nucleus & abducent nucleus
What is Foville’s Syndrome?
Lesion in the cadual/ medial pons caused by occlusion of the paramedian branches of the basilar artery
*****This is the syndrome suffered by the woman in the first case study
What is the hallmark of “Wrong- Way Eyes Syndrome?”
Eyes cannot look to the side of the lesion (i.e. side of weakness) but they can look to the opposite side
What structures are involved in “Wrong- Way Eyes Syndrome?”
Abducent nucleus
Corticonuclear tract
Corticospinal tract
Occlusion of which arteries can cause “Wrong- Way Eyes Syndrome?”
Paramedian branches of the basilar artery
What is Millard-Gubler Syndrome?
This is a syndrome that presents as deficits in 75% of the face:
- Entire half of face on one side (LMN CN VII)
- Lower half of face on opposite side
Occlusion of what arteries will cause a lesion to the rostral/ medial medulla?
Anterior spinal artery
Vertebral artery
What is Medial Medullary Syndrome? What structures are involved?
Lesion effecting the medial/rostral medulla
- CN XII
- ML
- Corticospinal tracts
What is the expected presentation of Medial Medullary Syndrome?
CN XII= tongue deviation to side of lesion (LMN)
ML= 2-point discrimination, vibration, proprioception deficits contralateral to lesion
Corticospinal= contralateral weakness
What CNs are involved in the gag reflex?
CN XI & X
Neurologic examination reveals prominent ataxia to the left arm & leg, but normal strength (no hemiparesis). The patient cannot stand without falling. What structure is affected?
Left cerebellum
Neurologic examination reveals pin prick that is decreased to the left side of the face. What structure is involved?
Left spinal trigeminal tract
Neurologic examination reveals pin prick that is decreased to the right neck, trunk, and limbs. What structure is involved?
Right spinothalamic tract
What is Horner’s Syndrome associated with?
Hypothalamospinal tract
Where is the lesion located that will cause dysphagia, ataxia, & left ptosis?
Left rostral medulla
What syndrome did the patient in Case #2 have?
Lateral Medullary Syndrome or Wallenburg Syndrome
A lesion to which structures will cause difficulties in walking, tendency to sway to the right, staggering to the right?
Right ICP & cerebellum
A lesion to what structure will cause dizziness and tinnitus in the right ear?
CN VIII (right)
What did the patient in Case #3 have?
Acoustic Neuroma/ Schwanoma
