What is Wallenberg's syndrome?

Wallenberg Syndrome: Neuroanatomical Basis and Clinical Manifestations

Wallenberg syndrome, also known as lateral medullary syndrome, is a neurological condition resulting from infarction in the territory of the posterior inferior cerebellar artery (PICA) affecting the dorsolateral medulla oblongata. This syndrome is primarily caused by occlusion of either the vertebral artery or the posterior inferior cerebellar artery, most commonly due to arteriosclerotic-thrombotic occlusion. 1

Pathophysiology

The primary mechanisms of Wallenberg syndrome include:

1. Vascular occlusion: Most commonly caused by:

   • Arteriosclerotic-thrombotic occlusion of the vertebral artery or PICA (most frequent) 2
   • Embolic arterial occlusion (less common)
   • Vertebral artery dissection (can occur even with trivial trauma) 3

2. Less common causes:

   • Syphilitic vascular changes
   • Tumors or metastases affecting the dorsolateral medulla
   • Metastatic encephalitis (extremely rare) 2
   • Multiple sclerosis (can mimic stroke presentation) 4

Clinical Manifestations

Wallenberg syndrome presents with a characteristic constellation of neurological symptoms due to involvement of specific structures in the lateral medulla:

Key Clinical Features:

• Vestibular symptoms: Vertigo, nystagmus, oscillopsia
• Ipsilateral Horner syndrome: Ptosis, miosis, anhidrosis
• Bulbar symptoms: Dysphonia, dysphagia, dysarthria, decreased gag reflex
• Sensory deficits:
  • Ipsilateral facial pain and paresthesia
  • Ipsilateral facial hypoalgesia and thermoanaesthesia
  • Contralateral hypoalgesia and thermoanaesthesia in the trunk and limbs
• Cerebellar signs: Ipsilateral ataxia, dysmetria
• Other features:
  • Diplopia
  • Facial ruddiness and dry skin
  • Impaired taste
  • Decreased ipsilateral blink reflex 1

Diagnosis

Diagnosis is primarily clinical, based on the characteristic constellation of symptoms, and confirmed with neuroimaging:

1. Clinical examination: Identifying the classic alternate sensory syndrome, Horner syndrome, and cerebellar manifestations
2. Neuroimaging:
   • MRI brain (particularly of the brainstem) is the gold standard
   • CT head may be performed initially but has low sensitivity (~10%) for posterior fossa ischemic strokes 5

Management

Management focuses on:

1. Acute treatment: Following stroke protocols if ischemic etiology is confirmed

2. Rehabilitation:

   • Swallowing therapy for dysphagia (patients may initially require nasogastric feeding) 6
   • Physical therapy for postural disorders and ataxia
   • Speech therapy for dysarthria

3. Secondary prevention:

   • Antiplatelet or anticoagulation therapy based on etiology
   • Risk factor modification for cardiovascular disease

Prognosis

The prognosis varies significantly between patients:

• Dysphagia and postural disorders often improve with rehabilitation, though recovery timelines differ significantly between patients 6
• Postural stability typically shows partial improvement after physiotherapy
• Early rehabilitation therapy is crucial for optimal recovery

Clinical Pearls and Pitfalls

• Wallenberg syndrome can be misdiagnosed as multiple sclerosis or other conditions, and conversely, MS can present as Wallenberg syndrome 4
• Even trivial trauma involving neck rotation (such as during golf) can cause vertebral artery dissection leading to this syndrome 3
• Patients may require emergency airway management if acute dyspnea develops due to severe bulbar dysfunction 6
• The HINTS examination (Head Impulse, Nystagmus, Test of Skew) can help differentiate central from peripheral causes of vertigo, though its accuracy depends on examiner experience 5

Understanding the neuroanatomical basis of Wallenberg syndrome is essential for proper diagnosis and management, as the classic neurological manifestations directly correlate with the affected structures in the lateral medulla.