Hemimedullary infarct with ipsilateral hemiplegia: a vertebral artery dissection syndrome?

BACKGROUND: Hemimedullary syndrome is very rare and combines the clinical features of lateral and medial medullary infarctions. In patients with hemimedullary syndrome, the presence of ipsilateral, rather than contralateral hemiplegia, is rare. OBJECTIVE: To describe a patient with an infarction in the right hemimedulla with an ipsilateral motor deficit due to dissection of the right vertebral artery (VA) and to assess whether the ipsilateral hemiplegia may be the result of a specific stroke mechanism. METHODS: We reviewed the reports of hemimedullary syndrome in the literature and compared the characteristics of patients with dissection of the VA with those with VA atherosclerotic disease. RESULTS: In our patient, magnetic resonance angiography showed dissection of the right VA to be the cause of the stroke. In a review of the literature (including our case), hemiplegia was ipsilateral to the infarction in four of the five patients with VA dissection, but contralateral in all six patients with atherosclerotic disease of the VA (p=0.01). In all five cases of VA dissection, the right hemimedulla was involved, while, in the six cases of atherosclerotic disease, the left side of the medulla oblongata was affected in five instances and the right side in one (p=0.01). CONCLUSION: Dissection of the VA may provoke a hemimedullary lesion at a lower level than atherosclerosis, thus affecting medullary-penetrating branches that irrigate the medulla immediately below the pyramidal decussation. Hemimedullary syndrome accompanied by ipsilateral motor deficit should raise suspicion of dissection of the VA.