Brainstem Lesion Localization
Brainstem Lesion Localization
1. Ipsilateral oculomotor palsy with contralateral hemiplegia indicates:
A. Benedikt syndrome
B. Weber syndrome
C. Wallenberg syndrome
D. Claude syndrome
Weber syndrome is a ventral midbrain lesion causing CN III palsy and contralateral hemiplegia.
2. Dysphagia and hoarseness are hallmarks of:
A. Lateral medullary lesion
B. Midbrain lesion
C. Medial pontine lesion
D. Cerebellar lesion
Wallenberg syndrome involves nucleus ambiguus causing dysphagia and hoarseness.
3. Facial paralysis with contralateral hemiplegia suggests lesion in:
A. Midbrain
B. Ventral pons
C. Lateral medulla
D. Cerebellum
Millard–Gubler syndrome occurs in ventral pontine lesions affecting CN VII and corticospinal tract.
4. Tongue deviation toward lesion indicates damage to:
A. CN IX
B. CN X
C. CN XII
D. CN V
Hypoglossal nerve palsy leads to tongue deviation toward the lesion.
5. Ipsilateral Horner syndrome with contralateral pain loss indicates:
A. Weber syndrome
B. Claude syndrome
C. Dejerine syndrome
D. Wallenberg syndrome
Wallenberg syndrome disrupts sympathetic fibers causing ipsilateral Horner syndrome.
6. Contralateral hemiparesis with ipsilateral tongue deviation suggests:
A. Medial medullary syndrome
B. Lateral medullary syndrome
C. Claude syndrome
D. Benedikt syndrome
Dejerine syndrome affects pyramids and hypoglossal nerve.
7. Cranial nerve VI nucleus lies in:
A. Midbrain
B. Pons
C. Medulla
D. Thalamus
The abducens nucleus is located in the dorsal pons.
8. Ipsilateral facial pain loss with contralateral body pain loss occurs in:
A. Medial pontine lesion
B. Midbrain lesion
C. Lateral medullary lesion
D. Cerebellar lesion
Spinothalamic and trigeminal tract involvement in Wallenberg syndrome.
9. Ipsilateral ataxia with CN III palsy suggests:
A. Weber syndrome
B. Dejerine syndrome
C. Millard-Gubler syndrome
D. Claude syndrome
Claude syndrome involves red nucleus and CN III causing ataxia.
10. Crossed neurological deficits most strongly indicate:
A. Brainstem lesion
B. Cortical lesion
C. Basal ganglia lesion
D. Peripheral neuropathy
Brainstem lesions cause ipsilateral cranial nerve signs with contralateral long tract deficits.
11. Ipsilateral loss of facial pain with contralateral body pain loss localizes to:
A. Medial medulla
B. Ventral pons
C. Lateral medulla
D. Midbrain tegmentum
Spinothalamic and spinal trigeminal tract involvement produces crossed pain loss in Wallenberg syndrome.
12. Internuclear ophthalmoplegia results from lesion of:
A. Red nucleus
B. Medial longitudinal fasciculus
C. Corticospinal tract
D. Pontine reticular formation
INO occurs due to lesion of the medial longitudinal fasciculus connecting CN VI and CN III nuclei.
13. Ipsilateral limb ataxia with contralateral hemiparesis indicates lesion of:
A. Cerebellar hemisphere
B. Superior cerebellar peduncle in midbrain
C. Vestibular nucleus
D. Inferior cerebellar peduncle
Lesions affecting the superior cerebellar peduncle in midbrain produce ataxia with contralateral weakness.
14. Facial nucleus is located in which structure?
A. Midbrain
B. Medulla
C. Pons
D. Cerebellum
The facial nerve nucleus lies in the caudal pons.
15. Ipsilateral facial paralysis with ipsilateral gaze palsy indicates:
A. Lateral medullary syndrome
B. Weber syndrome
C. Benedikt syndrome
D. Foville syndrome
Foville syndrome involves pontine tegmentum causing facial palsy and gaze palsy.
16. Contralateral spastic hemiplegia with ipsilateral CN III palsy indicates:
A. Weber syndrome
B. Wallenberg syndrome
C. Claude syndrome
D. Dejerine syndrome
Damage to corticospinal tract and CN III in ventral midbrain produces Weber syndrome.
17. Vestibular nuclei are primarily located in:
A. Midbrain
B. Medulla and pons junction
C. Thalamus
D. Hypothalamus
Vestibular nuclei lie in the floor of the fourth ventricle at the pontomedullary junction.
18. Contralateral body pain loss with intact facial sensation suggests lesion of:
A. Spinal trigeminal nucleus
B. Facial nucleus
C. Spinothalamic tract only
D. Red nucleus
Selective spinothalamic tract lesions cause contralateral body pain loss.
19. Benedikt syndrome involves lesion of:
A. Ventral pons
B. Medial medulla
C. Lateral medulla
D. Midbrain tegmentum
Benedikt syndrome involves red nucleus and CN III in midbrain tegmentum.
20. Ipsilateral facial paralysis with contralateral loss of vibration sense suggests:
A. Ventral pontine lesion
B. Lateral medulla
C. Midbrain tectum
D. Cerebellar hemisphere
Ventral pontine lesions may affect facial nerve and medial lemniscus pathways.
Localization of brainstem lesions is a classic neurological exercise. Because cranial nerve nuclei lie in the brainstem and long tracts pass through it, lesions typically produce “crossed findings”:
- Ipsilateral cranial nerve deficits
- Contralateral long-tract signs (motor or sensory)
This principle allows accurate localization to midbrain, pons, or medulla.
Brainstem Lesion Localization
1. Midbrain Lesions
Key structures:
- CN III, IV nuclei
- Red nucleus
- Cerebral peduncles
- Superior cerebellar peduncle
Typical Clinical Signs
• Ipsilateral CN III palsy → ptosis, dilated pupil, eye “down & out”
• Contralateral hemiparesis (corticospinal tract)
• Contralateral ataxia or tremor (red nucleus involvement)
Classic Syndromes
| Syndrome | Lesion | Features |
|---|---|---|
| Weber Syndrome | Ventral midbrain | Ipsilateral CN III palsy + contralateral hemiplegia |
| Benedikt Syndrome | Tegmentum | CN III palsy + contralateral ataxia/tremor |
| Claude Syndrome | Red nucleus + CN III | CN III palsy + contralateral ataxia |
2. Pontine Lesions
Key structures:
- CN V, VI, VII, VIII nuclei
- Middle cerebellar peduncle
- Corticospinal tract
Typical Signs
• Ipsilateral facial weakness
• Ipsilateral lateral gaze palsy
• Contralateral hemiparesis
• Loss of facial sensation
Classic Syndromes
| Syndrome | Lesion | Features |
|---|---|---|
| Millard-Gubler Syndrome | Ventral pons | CN VI + CN VII palsy + contralateral hemiplegia |
| Foville Syndrome | Dorsal pons | CN VI palsy + facial palsy + gaze palsy |
| Marie-Foix Syndrome | Pontine tegmentum | Ataxia + cranial nerve deficits |
3. Medullary Lesions
Key structures:
- CN IX, X, XI, XII nuclei
- Spinothalamic tract
- Inferior cerebellar peduncle
- Nucleus ambiguus
Typical Signs
• Dysphagia / hoarseness
• Contralateral body pain-temperature loss
• Ipsilateral facial sensory loss
• Ataxia
Classic Syndromes
| Syndrome | Lesion | Features |
|---|---|---|
| Wallenberg Syndrome | Lateral medulla | Dysphagia, hoarseness, ipsilateral facial pain loss, contralateral body pain loss |
| Dejerine Syndrome | Medial medulla | Contralateral hemiparesis + contralateral vibration loss + ipsilateral tongue deviation |
High-Yield Localization Rule (Exam Shortcut)
| Finding | Lesion Level |
|---|---|
| CN III palsy | Midbrain |
| Facial paralysis (CN VII) | Pons |
| Dysphagia + hoarseness | Medulla |
| Crossed motor deficit | Brainstem |
| Ataxia + cranial nerve deficit | Tegmentum involvement |
Ultra-High Yield Clinical Pattern
Crossed neurological signs = brainstem lesion
Example:
- Right facial palsy
- Left hemiparesis
➡ Right pontine lesion
✅ Memory Trick
“3-7-12 Rule”
- III → Midbrain
- VII → Pons
- XII → Medulla
