Lateral Medullary (Wallenberg) Syndrome - PICA Territory Infarction
The most likely affected artery is A. PICA (Posterior Inferior Cerebellar Artery). This clinical presentation is classic for lateral medullary syndrome (Wallenberg syndrome), which results from infarction in the PICA territory 1, 2.
Clinical Syndrome Analysis
The constellation of symptoms described represents the hallmark features of lateral medullary syndrome:
- Ataxia (ipsilateral) - due to inferior cerebellar peduncle and cerebellar involvement 1, 3
- Ipsilateral facial sensory loss - from involvement of the spinal trigeminal nucleus and tract 1, 2
- Dysphagia - results from nucleus ambiguus damage affecting cranial nerves IX and X 1, 3
- Horner's syndrome (ipsilateral) - caused by disruption of descending sympathetic fibers 1, 2, 4
- Contralateral body sensory loss (likely the "contralateral LL weakness" mentioned) - from spinothalamic tract involvement 1, 2
Why PICA and Not the Other Options
PICA is the correct answer because it supplies the lateral medulla where all these structures are located 1, 2. The classic triad identifying lateral medullary syndrome consists of Horner's syndrome, ipsilateral ataxia, and ipsilateral hyperalgesia 2.
AICA (Option B) is incorrect because anterior inferior cerebellar artery territory infarction presents differently with vertigo, tinnitus, facial weakness, lateral gaze palsy, and hearing loss when pontine structures are involved 5. AICA territory strokes typically affect more anterior and lateral cerebellar structures along with the pons 5.
Basilar artery (Option D) is incorrect because basilar occlusion would produce bilateral findings, altered consciousness, and involvement of multiple posterior circulation territories rather than this focal lateral medullary presentation 6.
Option C ("Anterior cerebellar") is not a recognized major cerebellar artery and is anatomically incorrect.
Vascular Territory Context
The vertebrobasilar system, which includes PICA, commonly presents with ataxia, cranial nerve deficits, visual field loss, dizziness, imbalance, and incoordination 6. PICA typically arises from the vertebral artery and supplies the lateral medulla and inferior cerebellum 6, 1.
Risk Factor Consideration
This elderly hypertensive patient fits the typical demographic for PICA territory stroke, as large-artery atherosclerotic disease in the vertebrobasilar system is the main cause of posterior circulation strokes 5. The vertebral artery or PICA itself may be affected by thrombosis or emboli 2, 3.
Clinical Pitfall
Do not confuse contralateral findings - the sensory loss affecting the contralateral body (spinothalamic tract) is different from the ipsilateral facial sensory loss (trigeminal system), which is pathognomonic for lateral medullary syndrome 1, 2. True contralateral motor weakness would be unusual in pure lateral medullary syndrome and might suggest additional pontine involvement or misinterpretation of ataxia as weakness 4.