This article is interesting but misleading. (I do surgeries on patients with strokes):

CCMs (cavernous malformations) are vascular lesions, rare vascular lesions and relatively rarely they can bleed and cause "strokes" (as in neurological deficits in patients).

However CCMs that bleed make up a minuscule fraction of a percentage of all patients who have strokes (which are generally caused by ischemia - blockages to vessels with decreased oxygenated blood to the brain).

The title should read 'gut bacteria can potentially trigger rare type of brain vascular malformations'.