Wallenberg syndrome

**Etiology/Vascular supply:** Occlusion of the posterior inferior cerebellar artery (PICA) or, more commonly, the intracranial vertebral artery. Causes: atherosclerosis/thrombosis, vertebral artery dissection (think young patient, neck trauma, chiropractic manipulation), embolism.

**Structures involved and resulting deficits:** - **Spinal trigeminal nucleus/tract** → ipsilateral loss of pain and temperature sensation on the face. - **Spinothalamic tract (lateral)** → contralateral loss of pain and temperature sensation in the body (trunk and limbs). This produces the classic "crossed" sensory findings. - **Nucleus ambiguus (CN IX, X)** → ipsilateral palate droop, dysphagia, hoarseness, diminished gag reflex (the afferent limb, CN IX, is also affected). - **Descending sympathetic fibers** → ipsilateral Horner syndrome (ptosis, miosis, anhidrosis). - **Vestibular nuclei** → vertigo, nausea/vomiting, nystagmus. - **Inferior cerebellar peduncle/cerebellum** → ipsilateral limb ataxia, dysmetria, and falling toward the side of the lesion (lateropulsion). - **Solitary nucleus/tract** (sometimes) → taste disturbance.

**Key spared structures (high-yield):** Because the lesion is lateral, the medial structures are spared. There is no weakness (corticospinal tract in the medial medulla/pyramids spared), no loss of vibration/proprioception/fine touch (medial lemniscus spared), and no tongue deviation (CN XII spared). Contrast with **medial medullary syndrome (Dejerine syndrome)**: anterior spinal artery/vertebral occlusion causing contralateral hemiparesis, contralateral loss of proprioception/vibration, and ipsilateral tongue deviation (CN XII).

**Memory aid:** "Don't PICA horse that can't swallow"; PICA → dysphagia, hoarseness. Ipsilateral face, contralateral body.

**Diagnosis:** Clinical localization; MRI with diffusion-weighted imaging (DWI) is more sensitive than CT for brainstem infarcts. Vascular imaging (CTA/MRA) to look for vertebral dissection or stenosis.

**Management:** Standard ischemic stroke care: IV thrombolysis (alteplase/tenecteplase) if within the window and no contraindications, antiplatelets, statin, and risk factor control. Dissection is treated with antithrombotic therapy (antiplatelet or anticoagulation). Supportive care for dysphagia (swallow evaluation, aspiration precautions, possible feeding tube) and vertigo/nausea (antiemetics, vestibular rehab). Monitor for cerebellar edema in larger cerebellar involvement, and for respiratory or autonomic instability (rare).

**Complications/Prognosis:** Aspiration pneumonia from dysphagia is the major early risk. Many patients recover substantially, though dysphagia and central pain syndromes can persist.

**Contrast with Lateral pontine syndrome (AICA):** Adds ipsilateral facial paralysis (CN VII), hearing loss/tinnitus (CN VIII), and similar crossed sensory findings.