Even thrombolytics, the drugs used to dissolve blood clots after a cerebral infarction, or blockage of a vessel in the brain, can bring on another stroke - this time, by haemorrhage.

We’re frankly mystified at the suggestion to take beta-blockers for a rapid heartbeat. Certain beta-blockers, like Sotacor, can cause torsade de pointes, or an unusually rapid heartbeat of more than 100 beats per minute, according to Sortacor’s manufacturer, Bristol-Myers Squibb (Physicians’ Desk Reference).

So if you are taking any sort of medication, even for migraine, you might consider this a possible cause of your TIAs.

Ordinarily, if there are one or more risk factors for stroke, a doctor may suggest either drug therapy or surgery to reduce your risk. The gold standard of preventative stroke therapy is antiplatelet therapy - taking aspirin. Aspirin supposedly ‘works’ by thinning the blood and lowering blood pressure, and is a first-line treatment for TIA patients. The bottom line is that aspirin has never been proven to prevent stroke in low-risk patients with no history of cardiovascular disease (N Engl J Med, 1992; 327; 175-81).

Furthermore, aspirin is given in daily dosages of 5-325 mg/day but, at this level, it can act paradoxically - by increasing the risk of a burst blood vessel in the brain by 21 per cent, even in low-risk patients (Drugs Ther Bull, 1994; 32: 1 - 3).

One of the problems in using long-term just-in-case medicine like aspirin is that it depletes the body of many vital nutrients, which may be essential for protecting your heart and blood vessels.

In a study comparing patients taking aspirin with those taking warfarin and still others left untreated, there was no significant difference in low-risk patients between doing something and doing nothing; in high-risk patients, the differences between the three groups were large enough to be statistically significant, but not enough to be meaningful in terms of survival (J Am Med Assoc, 1995; 274: 1839-45).

The only other usual treatment for stroke is an operation to scrape away fatty deposits in your carotid arteries, which is unlikely in your case, given your age.

>From what you say, you don’t have any of the obvious causes for a TIA - high cholesterol, smoking, diabetes or alcohol abuse - although with your grandmother’s circumstance, there is a possibility of a genetic propensity to stroke.

Although you don’t give much information about your general health, one detail is highly significant: you had Lyme disease, caused by a bite from a tick which spreads Borrelia burgdorferi, a spiral-shaped bacteria). Although this disease is most prevalent in the US, it is being seen in increasing numbers in the UK. If left untreated, symptoms can come and go for years.

Numerous studies show that untreated Lyme disease can cause different neurological problems that imitate true stroke and TIAs. Indeed, the evidence suggests that Lyme borreliosis may be a more common cause of these puzzling episodes than medicine has previously thought.

In a study of patients with cerebral thrombosis or TIAs without a thrombosis, 24 of the 281 patients - nearly 9 per cent - had an immune-system response to B. burgdorferi, suggesting the presence of the bacteria in their blood. The researchers concluded that the symptoms of Lyme borreliosis may often masquerade as stroke (Stroke, 1993; 24: 1393-6).

Your tachycardia (rapid heartbeat) may also be related to Lyme myocarditis (heart inflammation due to the Lyme spirochaete) rather than a structural problem. In one case study, Lyme myocarditis had all the hallmarks of tachycardia (J Cardiovasc Electrophysiol, 1997; 8: 323-4).