You have been rightly diagnosed to have a special type of stroke called Lateral Medullary Infarction. Successful prevention of recurrence of stroke needs identification of modifiable risk factors such as hypertension, diabetes, heart disease (esp. atrial fibrillation), smoking, hyperlipidemia etc. Hypertension has a very strong association with stroke.
Reduction of blood pressure within the so called normal range has now been shown to be associated with fewer recurrent strokes. Regular exercise, proper weight management and avoidance of high fat and salt intake is recommended. In case of non vegetarians, red meat should be substituted by white meat, esp. fish. A new antiplatelet drug, Clopidogrel, has been found to be slightly more effective than Aspirin in stroke prevention.