B25. Symptoms of brainstem alternating syndromes (Weber’s and Wallenberg’s syndrome)

Brainstem stroke syndromes, also called brainstem alternating syndromes or crossed brainstem syndromes, are collections of symptoms occuring due to injury (usually ischaemic stroke) of the brainstem leading to ipsilateral motor and nuclear symptoms as well as contralateral sensory symptoms. The most common types are called Wallenberg syndrome and Weber syndrome. Other (very rare) types include Benedikt syndrome, locked-in syndrome, and many others.

Brainstem stroke syndromes are rare.

Wallenberg syndrome

Wallenberg syndrome is also called lateral medullary syndrome. It's the most common brainstem stroke syndrome.

• Infarct of lateral part of medulla oblongata due to posterior inferior cerebellar artery (PICA) obstruction
• Affection of ipsilateral cerebellar peduncle -> ipsilateral hemiataxia
• Affection of ipsilateral lateral spinothalamic tract, which later crosses in the anterior white commissure
  • -> Contralateral hypoesthesia
  • -> Contralateral decreased temperature sensitivity
• Affection of ipsilateral vestibular nuclei
  • -> vertigo, nausea
  • -> dizziness
  • -> ipsilateral nystagmus
• Affection of ipsilateral nucleus ambiguus (IX, X, XI)
  • -> Dysphagia
  • -> Hoarseness
  • -> Hiccups
• Affection of spinal trigeminal nucleus (V)
  • -> Ipsilateral hypoesthesia of the face
  • -> Ipsilateral decreased temperature sensitivity of the face
• Affection of sympathetic fibres -> Ipsilateral Horner syndrome

Weber syndrome

Weber syndrome is also called ventral midbrain syndrome.

• Infarct of ventral midbrain due to posterior cerebral artery obstruction
• Affection of ipsilateral oculomotor nerve
  • -> ptosis
  • -> mydriasis
  • -> inferolateral gaze deviation
• Affection of ipsilateral corticospinal tract, which later crosses in the pyramidal decussation
  • -> Contralateral hemiparesis or plegia
• Contralateral parkinsonism