26 - Lesions II Flashcards
Background information… What long ascending or descending tracts or other pathways could be involved in brainstem lesions? (6)
1 - Corticospinal tract 2 - Corticonuclear (corticobulbar) tract 3 - Spinothalamic tract 4 - Medial lemniscus 5 - Spinal tract of V 6 - Superior cerebellar peduncle (carries cerebellothalamic fibers) and inferior cerebellar peduncle
Where does the spinothalamic tract run?
Tends to maintain its lateral position as it ascends through the brainstem
Where does the medial lemniscus run?
Tends to shift position from medial to lateral as it ascends through the brainstem
Where does the spinal tract of V run?
Descends ipsilaterally from the mid-pons to C2 of the spinal cord
What fibers does the superior cerebellar peduncle carry?
Cerebellothalamic fibers
What are the two types of structures that could be affected by a brainstem lesion?
Tracts and cranial nerves
Which tracts may be involved in a MEDIAL brainstem lesion (since they are located close to the midline)?
- Pyramidal tract (contains corticospinal tract axons)
- Medial lemniscus (nucleus gracilis and nucleus cuneatus, impairment of vibratory and touch-pressure sense)
Which MEDIAL cranial nerves could be affected by a medial brainstem lesion?
- Oculomotor (CN III)
- Abducent (CN VI)
- Hypoglossal (CN XII)
What information can we gain from determining which of the medial brainstem cranial nerves is affected?
We can determine the LEVEL of the lesion…
What level is CN III located at?
Oculomotor (CN III) - located in rostral midbrain
What level is CN VI located at?
Abducent (CN VI) - located in caudal pons
What level is CN XII located at?
Hypoglossal (CN XII) - located in medulla
Which tracts may be involved in a LATERAL brainstem lesion (since they are located laterally)?
- Spinothalamic tract
- Spinal tract of V
What is the spinothalamic tract responsible for?
Pain and temperature
Some crude/light touch
What is the spinal tract of V responsible for?
Pain and temperature
Note that it descends IPSILATERALLY***
Which LATERAL cranial nerves could be affected by a lateral brainstem lesion?
- Trigeminal (CN V)
- Facial (CN VII)
- Vestibulocochlear (CN VIII)
- Glossopharyngeal (CN IX)
- Vagus (CN X)
What information can we gain from determining which of the lateral brainstem cranial nerves is affected?
We can determine the LEVEL of the lesion…
What level are CN V and CN VII located at?
Trigeminal (CN V) and Facial (CN VII) - located in the pons
What level is CN VIII located at?
Vestibulocochlear (CN VIII) - located in pons/medulla
What level are CN IX and CN X located at?
Glossopharyngeal (CN IX) and Vagus (CN X) - located in the medulla
What is the most common way to determine the location of a brainstem lesion?
The level of the brainstem lesion is most often localized by the cranial nerve involved
What are the two different lesions that can occur in the medial pontine basis?
- Dysarthria hemiparesis (pure motor hemiparesis) syndrome
- Ataxic hemiparesis syndrome
What causes dysarthria hemiparesis (pure motor hemiparesis) syndrome?
Occlusion of the basilar artery - PARAMEDIAN BRANCHES
These branches supply the ventral territory of the pons
What structures are affected in dysarthria hemiparesis (pure motor hemiparesis) syndrome?
- Corticonuclear (corticobulbar) tract
- Corticospinal tract
Describe the deficits that occur with damage to the corticonuclear tract
- These are UMNs, so the deficit would be contralateral weakness on the contralateral side
- Dysarthria will occur
Dysarthria
A motor speech disorder due to weakness or paralysis of the mouth (lips, tongue) and lower half of the face
Describe the deficits that occur with damage to the corticospinal tract
Remember these are UMNs, so the deficits would be contralateral weakness on the upper and lower limb - hemiparesis
What is the other lesion that can occur in the medial pontine basis?
Ataxic hemiparesis syndrome
What causes ataxic hemiparesis syndrome?
Occlusion of the basilar artery - PARAMEDIAN branches which supply the ventral territory of the pons
What three structures are affected?
1 - Corticonuclear (corticobulbar) tract
2 - Corticospinal tract
3 - Pontine nuclei and pontocerebellar fibers
Describe the deficits that occur with damage to the corticonuclear (corticobulbar) tract
These are UMNs, so the deficit will be contralateral lower face weakness and dysarthria (motor speech disorder from muscle weakness)
Describe the deficits that occur with damage to the corticospinal tract
These are UMNs, so the deficit will be contralateral upper and lower limb weakness (motor hemiparesis)
Describe the deficits that occur with damage to the pontine nuclei and pontocerebellar fibers
Contralateral ataxia
Ataxia is disordered movement - a neurological sign consisting of lack of voluntary coordination of muscle movements that includes gait abnormality.
What is Foville’s syndrome?
A syndrome caused by a lesion in the medial pontine basis and tegmentum
What causes Foville’s syndrome?
Occlusion of the basilar artery - PARAMEDIAN branches which supply the ventral and dorsal territories of the pons
What three structures are affected by Foville’s syndrome?
1 - Corticonuclear (corticobulbar) tract
2 - Corticospinal tract
3 - Facial colliculus
Describe the deficits that occur by damage to the corticonuclear (corticobulbar) tract
Contralateral lower face weakness and dysarthria
What is dysarthria?
A speech deficit arising from weak facial muscles and tongue
What deficits occur by damage to the corticospinal tract?
Contralateral upper and lower limb weakness
Does the facial colliculus contain UMNs or LMNs?
LMN