Lateral Medullary Syndrome: Clinical Presentation
Lateral medullary syndrome (Wallenberg syndrome) presents with a characteristic constellation of symptoms including vertigo, ipsilateral ataxia, contralateral pain/temperature sensory loss, dysphagia, and Horner's syndrome, resulting from infarction of the lateral medulla typically due to posterior inferior cerebellar artery (PICA) or vertebral artery occlusion 1.
Core Clinical Features
The most reliable diagnostic triad consists of 2:
- Ipsilateral Horner's syndrome (91% of cases)
- Ipsilateral ataxia (85%)
- Contralateral loss of pain and temperature sensation (85%)
Complete Symptom Profile
Vestibular and Cerebellar Symptoms
- Vertigo (51-94% depending on series) - often the presenting complaint 3, 4
- Dizziness and unsteady gait (94.4%) 4
- Ipsilateral limb ataxia (70-85%) 2, 4
- Nystagmus (61%) 2
Sensory Disturbances
The hallmark sensory pattern involves:
- Ipsilateral facial pain and temperature loss (32-64%) 3, 2
- Contralateral body pain and temperature loss (25-85%) - sparing the face 3, 2
- This crossed sensory deficit is pathognomonic for lateral medullary lesions
Bulbar Dysfunction
- Dysphagia (19-51%) 3, 2, 4
- Dysarthria (44%) 4
- Hoarseness/dysphonia 3, 5
- Loss of ipsilateral gag reflex 5
Autonomic Features
Other Neurological Signs
- Headache (32%) - can be the presenting symptom 3, 4
- Diplopia or blurred vision (present in 11 patients in one series) 2
- Facial weakness (42%) 2
- Nausea and vomiting 1, 6
Important Clinical Pitfalls
Facial weakness and ocular symptoms do NOT necessarily indicate infarction extending beyond the lateral medulla 2. This is a critical point, as clinicians may incorrectly assume more extensive brainstem involvement.
The syndrome can present with delayed or gradual onset of symptoms 7. Patients may initially present with isolated vertigo or dizziness and develop the full syndrome over several days, which can lead to misdiagnosis as benign peripheral vertigo or other conditions 8, 7.
Most cases present as minor strokes (73% with NIHSS 1-4), which may lead to underestimation of severity 4.
Associated Findings
- Cerebellar infarction occurs in only 17.6% of cases, despite the high frequency of vertebral artery occlusion 2, 4
- Extramedullary involvement is present in 25% of cases 4
- Vertebral artery disease is confirmed in 73% of patients through vascular imaging 2
Etiology Distribution
The underlying causes include 4:
- Large vessel atherosclerotic disease (40.7%)
- Small vessel disease (37.6%)
- Arterial dissection (5.5%)
- Undetermined etiology (13.8%)
The key to diagnosis is recognizing the crossed sensory pattern (ipsilateral face, contralateral body), combined with ipsilateral cerebellar signs and Horner's syndrome, which should prompt urgent MRI with diffusion-weighted imaging for confirmation 4, 8.