Wallenberg Syndrome (Lateral Medullary)
Wallenberg syndrome results from infarction of the lateral medulla, most commonly due to vertebral artery (VA) occlusion (~67%) or posterior inferior cerebellar artery (PICA) disease (~10%).[1] It…
Wallenberg syndrome results from infarction of the lateral medulla, most commonly due to vertebral artery (VA) occlusion (~67%) or posterior inferior cerebellar artery (PICA) disease (~10%).[1] It is a frequently misdiagnosed posterior circulation stroke that demands a high index of suspicion, particularly in the ED.[2-3]
1. History
- Onset: Acute onset of vertigo/dizziness (91%), nausea/vomiting (73%), and gait unsteadiness (88%)[4]
Key HPI questions
- Headache or neck pain (especially occipital/posterior) — present in ~80% of VA dissection cases[5]
- Dysphagia (61%), hoarseness (55%), hiccups[4]
- Facial numbness (ipsilateral) and body numbness (contralateral) — the hallmark crossed sensory pattern[2]
- Recent trauma, chiropractic manipulation, vigorous exercise, or sudden neck movement[6-7]
- Time of symptom onset (critical for thrombolysis eligibility)
- Important negatives: Typically no limb weakness or paralysis (distinguishes from anterior circulation stroke); absence of tactile sensory loss (dissociated sensory disturbance — pain/temperature affected, not light touch)[8]
2. Alarm Features
- Severe dysphagia with aspiration risk — aspiration pneumonia is a leading cause of respiratory failure and death[9-10]
- Respiratory failure — occurred in 8–11% of patients in series; associated with severe bulbar dysfunction, progression of bulbar symptoms, and extensive rostral medullary lesions[9-10]
- Autonomic dysregulation — sinus arrest, symptomatic bradycardia, heart block; may require pacemaker[11]
- Ipsilateral hemiparesis (Opalski variant) — suggests extension to corticospinal tract below pyramidal decussation[12]
- Bilateral symptoms — suggests bilateral medullary involvement or basilar artery compromise[13]
- Worsening or fluctuating neurological deficits — may indicate progressive dissection or propagating thrombus
3. Medications
Acute treatment
- IV alteplase (0.9 mg/kg, max 90 mg) if within 4.5 hours of onset; the EXPECTS trial demonstrated benefit even at 4.5–24 hours for posterior circulation strokes (89.6% vs 72.6% functional independence at 90 days)[14]
- Tenecteplase is FDA-approved for AIS and increasingly used, though alteplase has more established evidence in posterior circulation[15-16]
Secondary prevention
- Antiplatelet therapy: aspirin ± clopidogrel (short-term DAPT)[12][17]
- For VA dissection: antithrombotic therapy (antiplatelet or anticoagulation) for at least 3–6 months per AHA guidance; choice should be individualized[18]
- Statin therapy (e.g., atorvastatin)[19]
- Contraindicated/caution: Avoid anticoagulation if intracranial extension of dissection (risk of SAH); standard thrombolysis contraindications apply[20]
- Symptomatic: Antiemetics for vertigo/nausea; gabapentin or pregabalin for central neuropathic pain (common sequela)
4. Diet
- NPO initially until formal swallowing assessment — dysphagia is present in ~61% and is often severe[4][21]
- Modified diet (thickened liquids, pureed foods) based on speech-language pathology evaluation
- Nasogastric or PEG tube if prolonged severe dysphagia
- Long-term: heart-healthy diet addressing vascular risk factors (hypertension, hyperlipidemia)
5. Review of Systems
- Neurologic: Vertigo, diplopia, dysarthria, dysphagia, hiccups, facial/body numbness, gait instability
- Cardiovascular: Syncope, palpitations, chest pain (autonomic dysregulation)[11]
- Respiratory: Dyspnea, cough with eating (aspiration), sleep-disordered breathing
- Ophthalmologic: Ptosis, miosis (Horner syndrome), oscillopsia
- GI: Nausea, vomiting, difficulty swallowing solids/liquids
6. Collateral History and Family History
- Witness account of symptom onset time (critical for thrombolysis window)
- Recent neck trauma, chiropractic manipulation, vigorous sports, or motor vehicle collision[6-7]
- Family history of connective tissue disorders (Ehlers-Danlos syndrome, Marfan syndrome, Loeys-Dietz syndrome) — associated with cervical artery dissection[18]
- History of fibromuscular dysplasia (~15% association with dissection)[7]
- History of migraine (overlap with PHACTR1 gene mutations and dissection risk)[18]
7. Risk Factors
- For atherosclerotic LMI: Hypertension, diabetes, hyperlipidemia, smoking, atrial fibrillation, advanced age[1]
- For VA dissection (up to 43–51% of LMI cases): Younger age, lower BMI, headache at onset, absence of hypertension, recent minor cervical trauma, connective tissue disorders[18][22]
- Chiropractic cervical manipulation (~1.3 per 100,000 incidence of VA dissection within 1 week)[23]
- Mean age at dissection diagnosis: 45 years[18]
- Pathogenetic mechanisms in a large series: large vessel atherosclerosis (50%), arterial dissection (15%), small vessel disease (13%), cardiac embolism (5%)[1]
8. Differential Diagnosis
- Peripheral vestibular disorders (vestibular neuritis, BPPV, Meniere disease) — most common misdiagnosis; lack crossed sensory findings and Horner syndrome[3][8]
- Cerebellar infarction/hemorrhage — may coexist; prominent ataxia but typically without crossed sensory loss
- Medial medullary syndrome — ipsilateral tongue weakness (CN XII), contralateral hemiparesis, contralateral deep sensory loss[13]
- Brainstem demyelination (MS) — younger patients, subacute onset, prior episodes
- Brainstem tumor — progressive course
- Basilar migraine — episodic, fully reversible, no infarct on imaging
- Posterior fossa mass/abscess
- Cannot-miss: Basilar artery occlusion (can be rapidly fatal), cerebellar hemorrhage with brainstem compression
9. Past Medical History
- Prior stroke or TIA (especially posterior circulation)
- Previous VA dissection (recurrence is rare but possible — this patient had a recurrence at 3 years)[24]
- Hypertension, diabetes, atrial fibrillation, hyperlipidemia
- Connective tissue disorders
- History of neck surgery or trauma
- Smoking history
10. Physical Exam
- Vital signs: Blood pressure (often elevated; may have labile BP from autonomic dysfunction); heart rate (watch for bradycardia)[11]
Classic findings (ipsilateral to lesion)
- Horner syndrome (ptosis, miosis, anhidrosis) — 73%[4]
- Facial pain/temperature sensory loss (CN V spinal nucleus) — 85%[4]
- Palatal/pharyngeal/vocal cord paralysis (nucleus ambiguus) — uvula deviates away from lesion
- Cerebellar ataxia (limb dysmetria, gait ataxia) — 88%[4]
- Ipsipulsion — falling/leaning toward the side of the lesion[25]
Contralateral to lesion
- Loss of pain/temperature sensation on trunk and limbs (spinothalamic tract) — 94%[4]
- Other: Nystagmus (often horizontal-rotatory, beating away from lesion), dysarthria, hiccups
- Absent findings: Typically no hemiparesis (if present, consider Opalski variant or alternative diagnosis)[12]
11. Lab Studies
- Standard stroke labs: CBC, BMP, coagulation studies (PT/INR, aPTT), glucose, troponin, lipid panel
- Troponin: Elevated in neurogenic cardiac injury; also to rule out concurrent ACS[26]
- HbA1c for diabetes screening
- ESR/CRP if vasculitis suspected
- Toxicology screen in young patients (amphetamines associated with dissection)[7]
- Hypercoagulability workup if young patient without clear etiology
12. Imaging
- First-line: MRI brain with DWI — gold standard for detecting lateral medullary infarction; CT is insufficient for medullary lesions and frequently misses posterior fossa strokes[3-4]
- CT head: Obtain emergently to rule out hemorrhage, but sensitivity for posterior fossa ischemia is poor[3]
Vascular imaging (essential)
- CTA or MRA of head and neck — to evaluate for VA dissection or atherosclerotic occlusion[1][6]
- High-resolution vessel wall MRI (HR-VWMRI) — superior for detecting dissection (identified dissection in 51% of LMI patients in one series)[22]
- Key imaging findings: Restricted diffusion in lateral medulla on DWI; VA occlusion or dissection flap on angiography
- Note: Acute brainstem infarction may not be apparent on initial MRI; repeat imaging in 24–48 hours if clinical suspicion remains high[8]
13. Special Tests
- NIHSS — often low score (weighted toward anterior circulation); does not reliably capture posterior circulation deficits[3]
- Bedside swallowing assessment followed by formal videofluoroscopic swallowing study (VFSS) or fiberoptic endoscopic evaluation of swallowing (FEES)[21]
- Portable thermography — lateral body surface temperature differences can help detect Wallenberg syndrome, especially for non-neurologists; assessment takes <2 minutes[8]
- HINTS exam (Head Impulse, Nystagmus, Test of Skew) — useful to differentiate central from peripheral vertigo at bedside
14. ECG
- Obtain on all patients — both to evaluate for cardiac source of embolism and to monitor for neurogenic cardiac complications
- LMI-specific cardiac complications: Sinus arrest, symptomatic bradycardia, AV block due to involvement of nucleus tractus solitarius and dorsal vagal nucleus[11]
- General post-stroke ECG changes: ST-segment changes, QT prolongation, T-wave inversions ("cerebral T waves"), atrial fibrillation[27-28]
- Continuous telemetry monitoring recommended; extended cardiac monitoring (7-day Holter) for cryptogenic cases to detect paroxysmal AF[29]
- Dangerous patterns: New AF (embolic source), QT prolongation (risk of torsades), high-grade AV block
15. Assessment
- Wallenberg syndrome is a clinical diagnosis confirmed by MRI. The classic triad is ipsilateral Horner syndrome, ipsilateral cerebellar ataxia, and crossed hemisensory disturbance (ipsilateral face, contralateral body pain/temperature loss)[2][13]
- Presentation is highly variable — the "complete" syndrome is uncommon; incomplete forms are the rule[1-2]
Severity stratification
- Mild: Isolated vertigo/sensory symptoms, minimal dysphagia
- Moderate: Significant ataxia, moderate dysphagia, Horner syndrome
- Severe: Severe bulbar dysfunction, respiratory compromise, autonomic instability[9-10]
- Complications: Aspiration pneumonia, respiratory failure (11.6% acute mortality in one series), autonomic dysregulation, central pain syndrome (delayed), post-stroke depression[30]
- Prognosis: Generally good with optimal therapy; most patients achieve functional independence. Recurrent posterior circulation strokes are uncommon (~1.9% per year)[2][30]
16. Treatment Plan
Acute stabilization
- ABCs — monitor airway closely given bulbar dysfunction and aspiration risk
- NPO until swallowing assessed
- IV access, continuous telemetry, pulse oximetry
Reperfusion therapy
- IV alteplase within 4.5 hours if eligible (standard criteria); consider extended window up to 24 hours for posterior circulation stroke based on EXPECTS trial data[14]
- Mechanical thrombectomy for selected patients with VA/basilar occlusion within 6 hours[31]
Antithrombotic therapy
- If dissection: antiplatelet or anticoagulation for 3–6 months (individualized)[18]
- If atherosclerotic: short-term DAPT (aspirin + clopidogrel for 21–90 days), then single antiplatelet[17]
- If cardioembolic: anticoagulation per AF guidelines
Supportive care
- Speech-language pathology for swallowing rehabilitation[21]
- Physical/occupational therapy for ataxia and balance
- Blood pressure management (permissive hypertension acutely per stroke guidelines, then long-term control)
- Statin therapy
- Glycemic control
- Neuropathic pain management (common late complication): gabapentin, pregabalin, or amitriptyline
17. Disposition
- Admit all patients — stroke unit or ICU depending on severity
- ICU criteria: Severe bulbar dysfunction, respiratory compromise, hemodynamic instability, autonomic dysregulation, post-thrombolysis monitoring[9][11]
- Stepdown/stroke unit: Stable patients with moderate symptoms
- Neurology consultation — all patients
- Neurosurgery consultation if cerebellar edema/herniation risk or need for decompressive craniectomy[17]
- Interventional neuroradiology if endovascular therapy indicated
- Discharge criteria: Stable neurologic exam, safe swallowing, adequate mobility, secondary prevention medications initiated, follow-up arranged
18. Follow Up / Return Precautions
- Follow-up: Neurology within 1–2 weeks post-discharge; repeat vascular imaging at 3–6 months (especially for dissection to assess healing)[18]
- Speech therapy follow-up for ongoing dysphagia management
- Return immediately for: New or worsening weakness, difficulty breathing, inability to swallow, severe headache, vision changes, altered consciousness, syncope
- Expected recovery: Most patients improve significantly; dysphagia typically recovers as contralateral medullary swallowing center compensates. Central neuropathic pain (Dejerine-Roussy-like) may develop weeks to months later and can be chronic[21]
- Patient counseling: Avoid chiropractic cervical manipulation; medication adherence for secondary prevention; vascular risk factor modification (smoking cessation, BP control, diet, exercise)
- Recurrence risk: Low (~1.9%/year for posterior circulation stroke; recurrent dissection is rare except in connective tissue disorders)[18][30]
References
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31. Diagnosis and Management of Transient Ischemic Attack and Acute Ischemic Stroke: A Review. — Mendelson SJ, Prabhakaran S. The Journal of the American Medical Association. 2021.