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🧠 BRAINSTEM SYNDROMES — Comprehensive Neurosurgery Viva Guide

Sources: Localization in Clinical Neurology 8e (Brazis), Adams & Victor's Principles of Neurology 12e, Harrison's Principles of Internal Medicine 21e, Bradley & Daroff's Neurology in Clinical Practice

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📌 CONCEPT: What are Brainstem (Alternating / Crossed) Syndromes?

• Ipsilateral CN palsy + Contralateral hemiplegia = Brainstem lesion
• All syndromes named after the cranial nerve involved at that level

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🗺️ BRAINSTEM LEVELS & SYNDROMES AT A GLANCE

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🔴 SECTION A: MIDBRAIN SYNDROMES

1. WEBER SYNDROME (Ventral Midbrain)

📊 Demography

• Age: Any adult; peak 50–70 years (ischaemic); younger if aneurysm or tumour
• Sex: M > F (vascular causes)
• Aetiology: Posterior cerebral artery or basilar artery perforators occlusion; posterior communicating artery aneurysm (compresses CN III from outside); midbrain tumour; tuberculoma

🧬 Anatomy / Pathology

1. CN III fascicle (exits through crus cerebri)
2. Corticospinal + corticobulbar fibres (cerebral peduncle)

🩺 Clinical Features (Memorise as 2 + 2)

1. CN III palsy — complete ptosis, eye "down and out," mydriasis (dilated fixed pupil), diplopia
2. Supranuclear gaze palsy toward opposite side (if medial peduncle involved)

⚠️ Viva Trap: In Weber, eye goes DOWN and OUT (LR6, SO4 intact, CN III out). Ask: "Why is the face involved?" → Corticobulbar fibres cross; facial nucleus for lower face is contralateral UMN.

🔬 Investigations

• Indication: Any suspected acute brainstem stroke or mass
• Sequence: DWI (hyperintense = acute infarct within hours), ADC map (hypointense = restricted diffusion), FLAIR (hyperintense after 24h), T1 + T2
• Positive finding: Hyperintense signal in ventromedial midbrain on DWI/FLAIR; can see PCA territory infarction

• Indication: Emergency if MRI not available; rule out haemorrhage
• Positive: Hyperdense (blood) or hypodense (infarct after 24h) lesion in midbrain

• Indication: Suspect posterior communicating artery aneurysm, PCA occlusion
• Positive: Aneurysm at PCoA-ICA junction; PCA occlusion

• Indication: Aneurysm confirmed on CTA, pre-surgical planning
• Gold standard for vascular anatomy

• Indication: If xanthochromia suspected (SAH with false-negative CT)

• NIHSS (NIH Stroke Scale) — baseline and serial monitoring
• Hunt & Hess (if SAH from aneurysm): Grade 1–5
• Fisher Scale (SAH, CT based): Grade 1–4
• GCS for consciousness level

💊 Management

A. General/Acute

1. Call for help — activate stroke team; ABCDE
2. Position — 30° head elevation if raised ICP; flat if BP low
3. Oxygen, IV access, cardiac monitor
4. BP management — in acute ischaemic stroke: allow up to 220/120 if not thrombolysing; target <180/105 if thrombolysing
5. Blood glucose control (4–10 mmol/L)
6. NPO if dysphagia

B. Specific Medical Management

• tPA (Alteplase) within 4.5 hours
  • MOA: Tissue plasminogen activator → activates plasminogen → plasmin → fibrinolysis
  • Dose: 0.9 mg/kg IV (max 90 mg); 10% as bolus, rest over 60 min
  • Contraindications: Haemorrhagic stroke, BP >185/110, INR >1.7, recent surgery <14 days, platelets <100,000
• Aspirin 325 mg (if no thrombolysis, within 24h)
  • MOA: Irreversible inhibition of COX-1 → ↓ TXA2 → ↓ platelet aggregation
  • Dose: 160–325 mg loading, then 75–100 mg/day
• Dual antiplatelet (Aspirin + Clopidogrel) for TIA/minor stroke (POINT trial) × 21 days, then single antiplatelet
  • Clopidogrel MOA: Prodrug → active metabolite blocks P2Y12 ADP receptor on platelets irreversibly
• Statins: Atorvastatin 80 mg/day
  • MOA: HMG-CoA reductase inhibitor → ↓ LDL → plaque stabilisation + anti-inflammatory
• Anticoagulation (if cardioembolic): Heparin or NOAC after 24h
  • Heparin MOA: Binds antithrombin III → inhibits thrombin (IIa) and Xa
  • Warfarin MOA: Inhibits Vitamin K epoxide reductase → ↓ Factors II, VII, IX, X, Protein C & S

C. Surgical Options

1. Mechanical Thrombectomy (MT)

• Indication: Large vessel occlusion (LVO) of basilar artery or PCA; NIHSS ≥6; within 6–24h (DAWN/DEFUSE criteria); CT/CTA confirms occlusion
• Contraindication: No salvageable penumbra; large established infarct (ASPECTS <6)
• Position: Supine, femoral access (groin)

1. GA or conscious sedation
2. Femoral artery access → guide catheter to vertebrobasilar system
3. Microcatheter through clot → Stentriever deployment
4. Aspiration (ADAPT technique) or combination
5. Thrombus retrieval
6. Post-procedure angiography to confirm recanalization
7. ICU transfer

2. Surgical Clipping (for PCoA Aneurysm causing Weber)

• Indication: Unruptured PCoA aneurysm with CN III palsy (high risk of rupture); ruptured aneurysm (Hunt & Hess I–III)
• Contraindication: Poor-grade SAH (H&H IV–V) — may delay; elderly with poor medical status
• Position: Supine, head turned 15–30° to contralateral side, Mayfield 3-pin head holder

1. Position: Supine, head fixed in Mayfield clamp, turned 30° contralateral
2. Scalp incision: Pterional (frontotemporal)
3. Craniotomy: Frontotemporal bone flap
4. Open sylvian fissure
5. Identify ICA, CN II, follow to PCoA origin
6. Temporary clip on parent artery (if needed)
7. Permanent clip across aneurysm neck
8. Confirm clip with ICG videoangiography or Doppler
9. Closure in layers

3. Endovascular Coiling (alternative to clipping for PCoA aneurysm)

• Indication: Poor surgical candidate; aneurysm anatomy favourable for coiling (narrow neck, fundus:neck ratio >2); unruptured
• Steps: Femoral access → microcatheter into aneurysm sac → platinum coils deployed → sac thrombosis

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2. BENEDIKT SYNDROME (Midbrain Tegmentum — Ventral)

Anatomy/Pathology

• CN III fascicle → ipsilateral CN III palsy
• Red nucleus → contralateral involuntary movements (rubral tremor = Holmes tremor, choreoathetosis)
• Corticospinal tract (partial) → contralateral hemiparesis
• Medial lemniscus may be involved

Clinical Features

⚠️ Key differentiator: Benedikt = CN III + tremor (red nucleus). Weber = CN III + hemiplegia only.

Investigations: Same as Weber (MRI DWI, MRA)

Management

• Stroke management as above
• Holmes/Rubral tremor — notoriously drug-resistant
  • Levodopa/carbidopa (dopaminergic pathway restoration)
  • Clonazepam, propranolol (partial benefit)
  • Deep Brain Stimulation (DBS) of VIM thalamus — most effective for refractory tremor
    • DBS Indication: Disabling tremor >12 months, failed ≥2 medications
    • Target: Ventral Intermediate (VIM) nucleus of thalamus, or caudal zona incerta

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3. CLAUDE SYNDROME (Midbrain Tegmentum — Dorsal)

Pathology

• Dorsal red nucleus + brachium conjunctivum (superior cerebellar peduncle after decussation)
• CN III fascicle

Clinical Features

• Ipsilateral CN III palsy
• Contralateral cerebellar ataxia (asynergia, dysmetria, dysdiadochokinesis) — more prominent than Benedikt, without hemiballismus
• Minimal or no hemiparesis

Mnemonic: Claude = Cerebellar (dorsal); Benedikt = Both (cerebellar + pyramidal + tremor)

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4. NOTHNAGEL SYNDROME (Midbrain Tectum)

• Lesion: Superior cerebellar peduncle + CN III (unilateral or bilateral)
• Features: Bilateral CN III palsies + cerebellar ataxia + gaze palsies
• Cause: Tumour (pinealoma, collicular glioma) — commonest
• No hemiplegia (pyramidal tract spared)

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5. PARINAUD SYNDROME (Dorsal Midbrain / Pretectal)

Demography

• Age: Young adults (pineal tumours 15–35 years); children (aqueductal stenosis); any age (MS, vascular)
• Aetiology: Pinealoma/germinoma (most common), hydrocephalus (aqueductal dilation), MS, vascular, trauma

Pathology

Clinical Features (DEWDROP mnemonic)

Investigations

• MRI Brain: Pineal mass, tectal plate compression, aqueductal stenosis, hydrocephalus
• Serum tumour markers: AFP (yolk sac), β-hCG (germinoma), LDH
• CSF tumour markers (after relieving hydrocephalus)
• Visual field testing + VEP
• Ophthalmology: Slit lamp for Kayser-Fleischer (Wilson's, if young)

Management

• Endoscopic Third Ventriculostomy (ETV)
  • Indication: Obstructive hydrocephalus from pineal/tectal mass
  • Position: Supine, Mayfield clamp
  • Steps: Burr hole (Kocher's point, 2.5 cm from midline, 1 cm anterior to coronal suture) → rigid endoscope into lateral ventricle → through foramen of Monro → floor of 3rd ventricle → fenestrate floor with monopolar electrode → balloons dilate ostium → CSF flows into prepontine cistern
  • Advantages: Avoids VP shunt; simultaneous endoscopic biopsy
  • Contraindication: Previous infection, thickened floor, unfavourable anatomy

• Germinoma: Radio-sensitive → craniospinal radiation ± chemotherapy (BEP — Bleomycin, Etoposide, Cisplatin) — NO primary surgery needed
• Teratoma / Non-germinomatous GCT: Surgery first (posterior interhemispheric or supracerebellar infratentorial approach) then radiation + chemo
• Pineocytoma (WHO Grade I): Surgical resection → EFS >90%
• Pineoblastoma (WHO Grade IV): Surgery + craniospinal RT + chemo (poor prognosis)
• MS/vascular: Treat primary cause

• Supracerebellar Infratentorial (Krause approach): Most common
  • Position: Sitting (risk: VAE) or prone/concorde (safer, preferred now)
  • Steps: Midline posterior fossa craniotomy below tentorium → dissect between tentorium and cerebellum → expose quadrigeminal plate → identify tumour → microsurgical excision
• Occipital Transtentorial: For superior extension
• Posterior Interhemispheric: For tumours extending into corpus callosum

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🔵 SECTION B: PONTINE SYNDROMES

6. MILLARD-GUBLER SYNDROME (Ventral Pons)

Demography

• Age: 50–70 years (vascular); any age (tumour, MS)
• Cause: Basilar artery perforators occlusion; pontine glioma; MS; haemorrhage

Anatomy/Pathology

• CN VI nucleus or fascicle → ipsilateral lateral gaze palsy / abducens palsy
• CN VII fascicle (as it loops around CN VI nucleus) → ipsilateral facial palsy
• Corticospinal tract (basis pontis) → contralateral hemiplegia

Clinical Features

⚠️ Key point: Facial palsy here is LMN type (involves forehead) because the facial nucleus itself or its intrapontine fascicle is involved — distinct from UMN (central) facial palsy which spares the forehead.

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7. FOVILLE SYNDROME / RAYMOND-FOVILLE SYNDROME (Pontine Tegmentum)

Pathology

• PPRF (Paramedian Pontine Reticular Formation) + CN VI nucleus → ipsilateral conjugate gaze palsy (eyes cannot look to side of lesion)
• CN VII nucleus/fascicle → ipsilateral LMN facial palsy
• Corticospinal tract
• Sometimes: Descending sympathetic fibres → ipsilateral Horner

Clinical Features

Millard-Gubler vs Foville: Millard-Gubler → only CN VI palsy (one eye can't abduct). Foville → full conjugate gaze palsy (BOTH eyes can't look toward lesion, due to PPRF damage).

Management (Pontine Syndromes)

• Ischaemic pons: Same stroke protocol; basilar artery thrombectomy if basilar occlusion (door-to-recanalization within 6h, extended to 24h for basilar stroke with favourable imaging — ATTENTION trial)
• Pontine glioma (DIPG in children): See below
• MS: IV methylprednisolone 1g/day × 5 days for acute relapse
  • MOA: Glucocorticoid → binds GR → inhibits NF-κB → reduces BBB permeability and inflammation

Surgical Approach: Brainstem Tumour (Pontine)

• Approach: Retrosigmoid / far lateral / suboccipital depending on location
• Most focal exophytic lesions: Safe to biopsy/resect via retrosigmoid craniotomy
• DIPG (Diffuse Intrinsic Pontine Glioma): Biopsy only; then focal RT (54 Gy) + ONC201 (H3K27M-mutant); NO radical surgery
• Safe entry zones for brainstem surgery:
  • Lateral sulcus of pons (between CN V and VII)
  • Supratrigeminal zone (above CN V)
  • Peritrigeminal zone
  • Median sulcus (floor of 4th ventricle)

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🟢 SECTION C: MEDULLARY SYNDROMES

8. LATERAL MEDULLARY SYNDROME (Wallenberg Syndrome) — MOST COMMON BRAINSTEM SYNDROME

Demography

• Age: 40–70 years; younger with vertebral artery dissection (30–50 years)
• Sex: M > F
• Risk factors: HTN, DM, smoking, dyslipidaemia, vertebral artery dissection (trauma, neck manipulation, Marfan's)
• Incidence: Most common brainstem infarct syndrome

Aetiology

• Vertebral artery occlusion (50%) — large vessel atherosclerosis
• PICA (Posterior Inferior Cerebellar Artery) occlusion — less common than vert. artery
• Vertebral artery dissection (15%)
• Small vessel disease (13%)
• Cardioembolism (5%)
• Others: Cocaine, tumour, MS, neck manipulation, trauma

🧬 Anatomy/Pathology

🩺 Clinical Features (LATERAL mnemonic)

⚠️ Crossed sensory loss: Ipsilateral face pain/temp loss + Contralateral body pain/temp loss = PATHOGNOMONIC of lateral medullary syndrome. This is because the spinal trigeminal nucleus (face, ipsilateral) and spinothalamic tract (body, crosses in spinal cord) are both in the lateral medulla.

⚠️ Preserved: Motor function (pyramids = medial medulla), vibration/proprioception (dorsal columns = medial), tongue movements (XII = medial).

• Skew deviation (ipsilateral hypotropia)
• Ocular tilt reaction
• Nystagmus (horizontal-torsional, beating away from lesion)
• Ipsipulsion (saccades and smooth pursuit pull toward lesion side)
• "Upside down" room sensation

• Rostral (more severe): Dysphagia, hoarseness, facial paresis
• Caudal: Predominant vertigo, nystagmus, gait ataxia

🔬 Investigations

• Indication: Acute brainstem syndrome; Wallenberg is a CLINICAL diagnosis — MRI confirms
• Finding: Hyperintense DWI + hypointense ADC lesion in lateral medulla (posterior to inferior olive, lateral to pyramid)
• Note: DWI may be initially negative in first 24h for lateral medullary infarcts — repeat MRI at 48–72h if clinically suspected

• Indication: All cases to identify vertebral artery stenosis/occlusion/dissection
• Finding: Vertebral artery narrowing, occlusion; dissection (double lumen, flap)

• Indication: If MRA not available; initial assessment

• Indication: Suspect vertebral artery dissection
• Finding: Crescentic hyperintense mural haematoma in vertebral artery wall

• Indication: Rule out cardioembolic source
• Finding: Left atrial thrombus, AF, patent foramen ovale

💊 Management

Acute Phase

1. ABC — airway is critical (dysphagia/dysphonia from nucleus ambiguus damage)
2. NPO → NGT feeding if dysphagia
3. Antiplatelet/anticoagulation as per stroke guidelines
4. VTE prophylaxis (compression stockings → LMWH when safe)
5. Head of bed 30°

Specific Drugs

• Aspirin 300 mg loading → 75 mg/day (all ischaemic strokes)
• Clopidogrel if aspirin intolerant
• LMWH/Heparin → Warfarin/NOAC if AF (cardioembolic source)
• Statin (Atorvastatin 80 mg) regardless of baseline LDL

• Prochlorperazine 12.5 mg IM/10 mg oral — D2 antagonist; vestibular suppression; SHORT-TERM only
• Betahistine (not evidence-based for central vertigo)
• NOT Betahistine for acute central vertigo

• Chlorpromazine 25–50 mg TDS (FDA-approved) — D2 antagonist
  • MOA: Dopamine D2 receptor antagonism → suppresses hiccup reflex arc (phrenic nerve + vagal + reticular formation)
• Baclofen 5–20 mg TDS — GABA-B agonist; inhibits phrenic nerve hyperexcitability
• Metoclopramide 10 mg TDS — D2 + 5HT3 antagonist

• SLT (speech and language therapy) assessment
• Modified diet; compensatory swallowing techniques

Intervention

• Vertebral artery stenting/angioplasty — for symptomatic high-grade stenosis resistant to medical therapy (intracranial atherosclerosis)
• Vertebral artery dissection: Anticoagulation (heparin → warfarin 3–6 months) or antiplatelet
• No surgical option for lateral medullary infarct itself

Follow-up

• 3 months: MRI brain + MRA, mRS/Barthel assessment, SLT review
• 6 months & 1 year: Functional rehabilitation, secondary prevention review
• Ongoing: Annual risk factor review (BP, lipids, HbA1c, AF screening)
• Dysphagia: Repeat videofluoroscopy at 3 months

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9. MEDIAL MEDULLARY SYNDROME (Dejerine Syndrome)

Demography

• Age: 50–70 years
• Cause: Anterior spinal artery or vertebral artery occlusion (anteromedial branches)
• Less common than lateral medullary syndrome

Anatomy/Pathology

• Pyramid (corticospinal tract) → contralateral hemiplegia (spares face — nuclei above)
• Medial lemniscus → contralateral loss of proprioception + vibration + discriminative touch (dorsal column modalities)
• CN XII fascicle → ipsilateral hypoglossal palsy (tongue deviates to side of lesion)

Clinical Features

⚠️ Dejerine differs from Wallenberg: Pain/temperature and cerebellar signs are ABSENT (medial structure spared from these tracts). There is no Horner, no dysphagia, no crossed facial sensory loss.

⚠️ Bilateral medial medullary infarct = "heart-shaped" or "Y-shaped" DWI lesion — presents as quadriplegia + bilateral tongue palsy (devastating).

Investigations: Same as Wallenberg (MRI, MRA)

Management: Same stroke protocol; focus on physio for motor recovery

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10. AVELLIS SYNDROME

• Lesion: Dorsolateral tegmentum of medulla; CN X (nucleus ambiguus)
• Features:
  • Ipsilateral palate + vocal cord paralysis (hoarseness, dysphagia)
  • Contralateral spinothalamic loss (pain/temp body)
  • Sometimes ipsilateral Horner (if descending sympathetics involved)
• No tongue palsy (XII spared)

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11. JACKSON SYNDROME

• = Avellis + CN XII involvement
• Lesion: More extensive dorsolateral medullary tegmentum
• Features:
  • Ipsilateral CN X: Palate, pharynx, vocal cord paralysis
  • Ipsilateral CN XII: Tongue deviation toward lesion (LMN)
  • Contralateral hemiplegia (corticospinal)

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12. BABINSKI-NAGEOTTE SYNDROME

• Lesion: Extensive lateral medulla + inferior cerebellum (involves both dorsolateral AND some medial structures)
• Features: Combined Wallenberg features + contralateral hemiplegia (pyramid included)
• Rare; usually large infarcts

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📐 CLASSIFICATIONS

Classification 1: By Level

MIDBRAIN:    Weber → Benedikt → Claude → Nothnagel → Parinaud
PONS:        Millard-Gubler → Foville/Raymond-Foville → One-and-a-half syndrome
MEDULLA:     Wallenberg (lateral) → Dejerine (medial) → Avellis → Jackson → Babinski-Nageotte

Classification 2: By Aetiology

Classification 3: Adams & Victor Intramedullary Brainstem Syndrome Table (Viva Gold)

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🔑 KEY VIVA POINTS — QUICK FIRE

1. Which syndrome has NO hemiplegia? → Wallenberg (pyramids spared — medial medulla)
2. Which brainstem syndrome does NOT involve CN directly? → Parinaud (supranuclear)
3. First sign of PCoA aneurysm? → Dilated pupil (parasympathetics on outside of CN III)
4. Why is facial palsy LMN in pontine lesions? → Facial nucleus or intrapontine fascicle affected
5. Millard-Gubler vs Foville? → MG = CN VI only; Foville = full conjugate gaze palsy (PPRF)
6. Why crossed sensory in Wallenberg? → Spinothalamic (body) crosses at spinal cord level; trigeminal spinal nucleus (face) is ipsilateral in lateral medulla
7. MRI timing: DWI positive immediately; FLAIR positive after 6–12h; lateral medullary DWI can be false negative initially → repeat at 48h
8. Most common cause of Wallenberg under 50? → Vertebral artery dissection
9. Bilateral pontine haemorrhage? → Bilateral pinpoint pupils (sympathetic damage) + quadriplegia + locked-in state; frequently fatal
10. Best surgery for Parinaud + obstructive hydrocephalus? → ETV (endoscopic third ventriculostomy)

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📊 SCORES USED IN BRAINSTEM SYNDROMES

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🧪 PATHOLOGY OF CLINICAL FEATURES

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📋 FOLLOW-UP PROTOCOL

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📝 SUMMARY TABLE

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🎯 Top Viva Traps — Don't Get Caught

1. "Which brainstem syndrome has NO hemiplegia?" → Wallenberg — pyramids (medial medulla) are completely spared
2. "Why does the tongue point toward the lesion in medial medullary syndrome?" → LMN CN XII palsy — weak side is ipsilateral; tongue tip deviates to the paralysed side
3. "Which CN III palsy hits parasympathetics first?" → Compressive (PCoA aneurysm, uncal herniation) — parasympathetics are on the outside of CN III. Ischaemic CN III palsy typically SPARES the pupil (vasa nervorum supply the core)
4. "Millard-Gubler vs Foville?" → MG = CN VI alone (one eye can't look out); Foville = PPRF damaged = full conjugate gaze palsy (both eyes look away from lesion)
5. "Best initial investigation for acute Wallenberg?" → MRI DWI — but warn that it can be false-negative in first 24h for lateral medullary infarcts; repeat at 48–72h