Timothy C. Hain, MD . Page last modified: May 1, 2013
Defined Symptoms Diagnosis Treatment
Transient ischemic attacks or TIA's are brief episodes of neurological disturbance caused by reduced blood supply to an area of the brain. Strokes are longer lasting neurological disturbance, associated with permanent damage to the brain. This document discusses TIA's and strokes associated with dizziness, also known as Vertebrobasilar TIA's and Strokes. These strokes are from blockages of one or more of the arteries shown on the the picture to the right (Posterior Inferior Cerebellar Artery or PICA, vertebral arteries, anterior inferior cerebellar arteries or AICA, basilar artery, superior cerebellar artery or SCA).
|Normal "posterior circulation"||MRA scan of individual with narrowing of right vertebral artery, and dizziness/imbalance. No PICA is seen on the R side.|
A TIA or stroke usually begins abruptly. Reduced blood supply to the back part of the brain can cause dizziness. TIA's are temporary, and strokes have longer lasting symptoms (> 24 hours). In order of decreasing frequency, besides dizziness, other symptoms of vertebrobasilar TIA include visual disturbance, drop attacks, unsteadiness or incoordination, weakness, confusion, headache, hearing loss, numbness, speech disturbance, abnormal noise in the ears, and numbness around the mouth.
RISK FACTORS FOR TIA AND STROKE
To some extent, one can predict risk of stroke. Risk factors that are well known include:
**Numbers in () are derived from Whisnant et al, 1996
Risk from elevated blood pressure is steep and clear. For example, in the UK TIA trial, risk for recurrent stroke increased by 28% for every incremental increase of 10 mm Hg in systolic blood pressure between 130 and 160 (Farrell et al, 1991).
Although LDL-cholesteral, HDL cholesteral seems to reduce risk of stroke (Sacco et al, 2001). If your HDL cholesterol is > 35, then subtract one risk factor (a negative risk factor). Mitral valve prolapse is not a significant risk factor, overall (0.8 risk). TIA is a very strong risk factor for stroke (5.6 x risk). In general, relative risk for most of the above factors decreases with age (Whisnant et al, 1996), lending support for a unaggressive approach to risk factors in individuals of advanced age.
Risk from cholesterol can be further stratified into three groups, based on LDL (total cholesterol - HDL)-(triglycerides).
|LDL||Risk Factors||Risk Level for vascular disease|
|130-159||Less than 2||Moderate|
|>130||more than 2||High|
Controllable risk factors include being overweight, having high (> 140/90) or low blood pressure, heart disease, diabetes and smoking. Atrial fibrillation is a particularly important risk factor -- stroke occurs in 4.5% of untreated patients with atrial fibrillation per year. While uncommon, chiropractic neck manipulations can cause compression or tears of the vertebral arteries (Vibert et al, 1993; Smith et al, 2003), and for this reason, maneuvers involving neck "cracking" should be specifically avoided in individuals with vertigo. Whiplash injuries can also damage the vertebral arteries as the arteries traverse the vertebrae of the neck.
It is presently suggested that LDL be less than 100.
|Dissection of vertebral artery (cutoff of left sided vessel). Image courtesy of Ruth Ramsey, M.D. On the right hand side is another image of a vertebral dissection in a different patient. The vertebral artery on the left side is smaller and irregularly filled.|
DIAGNOSIS OF TIA AND STROKE
The diagnosis of TIA or stroke is usually made by a neurologist. Diagnosis is based upon having a compatible group of symptoms, exclusion of other reasonable causes such as disease of the inner ear, and identification of a cause of reduced blood flow.
Even when the examining doctor is very experienced, it is not always possible to be sure that a patient with dizziness does NOT have a stroke (see case example). Except in a few situations (i.e. BPPV), the clinical signs of vertigo are specific enough to exclude stroke. Because scanning every dizzy patient would be immensely costly, it is practically necessary to accept that with standard medical care, some patients may not be immediately diagnosed (if at all).
Testing to establish this diagnosis is individual to each patient, but usually will include blood tests for anemia and diseases of the circulation, an MR or CT angiogram test to visualize the blood vessels in the head and neck, and a hearing test and ENG test to exclude ear disease. Other common tests include the CT scan, EEG, EKG and Holter or event monitor. Vertebral artery doppler may be helpful in some.(Sakaguchi et al. 2003).
Recent studies suggest that atrial fibrillation occurs frequently in persons with TIA's, and that ambulatory cardiac monitoring may be indicated more often than thought in the past (Tayal et al, 2008; Cotter et al, 2013). This is particularly relevant as atrial-fibrillation is often treated with stronger blood thinners than other stroke-related conditions (see discussion of Coumadin treatment below). We think that the less invasive systems -- such as simply ambulatory event monitoring, are more sensible than the "implantable" systems, which seem to us to be both expensive as well as overly invasive.
RISK OF STROKE AFTER TIA
As noted above, TIA is a strong risk factor for stoke. The cumulative risk of stroke in persons having TIA's is about 18% in untreated patients, and about 10% in treated patients. The risk is highest in the first month (4-8%), and 12-13% in the first year (Toole, 1991). About 11% of persons with TIA in the emergency department will have a stroke within 90 days. There is also a significant risk of having a heart attack.
TREATMENT OF VERTEBROBASILAR TIA AND STROKE
No surgical treatment has shown to be effective for vertebrobasilar TIA or stroke. Medications are used to "thin" the blood, and to treat elevated cholesterol which may predispose to hardening of the arteries. Life style and dietary changes may reduce risk.
Currently available medications which may improve blood flow include:
Aspirin. There have been very many randomized trials of antiplatelet therapy. There appears to be little difference in doses between 50 and 1500 mg/day while larger doses increase the risk of gastrointestinal bleeding (Strauss, 2002). Nevertheless, as little as 1 baby aspirin per day reduces stroke incidence by about 30%. Aspirin is only about half as effective as coumadin for prevention of strokes associated with atrial fibrillation. Aspirin is no better than placebo for asymptomatic carotid stenosis. NSAID's do not prevent strokes (Bak, 2003)
Ticlodipine (Ticlid). This is a drug similar to aspirin. It is slightly more effective than aspirin, perhaps about 8%, but also slightly more risky. Dose is 250 mg, twice/day. CBC Blood tests must be taken every 2 weeks for the first 3 months because of the risk of neutropenia (low white cell count). Diarrhea occurs in 10% of persons on this drug.
Coumadin (Warfarin). The effectiveness of this medication for vertebrobasilar TIA is controversial, but current medical practice is to use coumadin in patients who have failed aspirin treatment. Also, in atrial fibrillation, coumadin reduces stroke by two thirds and death by one third. In atrial fibrillation, it is presently felt that coumadin should be given to all of those in whom it is safe. More about this follows. Coumadin has a higher risk of bleeding complication than other treatments. It is generally felt that the combination of aspirin and coumadin is more dangerous. It is only used in situations such as those persons with artificial heart valves. Usual starting dose is 5 mg daily, draw blood 1/week till stable, then readjust based on PT. Target "INR" or International Normalized Ratio is usually 1.5-2.5 but those with more severe problems may get higher targets (2-3 in atrial fibrillation, for example, see later). Patients on certain drugs may need more or less Coumadin because of interactions.
Dipyridamole (Persantine). Formerly used with aspirin, Persantine is now mainly used for patients on coumadin who have continued having TIAs in spite of adequate anticoagulation. Typical dose is 50 mg, three times/day. There is no added effect of combining this drug with aspirin.
Heparin. This intravenous medication is used in the hospital setting, in situations where there are repeated TIA's.
Low-molecular weight heparinoids. This medication is presently investigational. It is similar to heparin but does not require intravenous injection or frequent blood tests.
Pentoxifylline (Trental). Makes blood flow more freely. The usual dose is one tablet, three times/day. Pentoxifylline has not been proven to work in TIA.
Antiarythmics: Relevant for those with atrial fibrillation. Digoxin, beta blockers, verapamil, diltiazem, quinidine, procainamide, disopyramide, flecainide, propafenone, sotalol, and amiodarone are examples. Non-drug therapies such as ablation are also possible. These drugs have many side effects, which can include dizziness.
Dietary treatment (see comment below): If cholesterol is greater than 200, diet should be modified. The "step 1" diet is low in saturated fat, has limited cholesterol (no more than 300 mg/day), and for overweight individuals, restricted in calories. The total fat caloric content of the diet should not exceed 30%. One should strive to decrease consumption of meats, which are high in saturated fat, and replace calories with complex carbohydrates (not sugar), or fish. Avoid saturated oils such as palm oil and butter, using unsaturated oils such as olive oils or nut oils where needed. Increasing fiber in the diet may help reduce cholesterol. A minimum of 6 months of dietary treatment should be attempted before initiating drug therapy unless LDL cholesterol is > 130 mg/dl. For this level of LDL alter diet and begin drug therapy simultaneously.
Cholesterol should be rechecked at 4-6 weeks and 3 months after starting the diet. If the step-I diet fails (LDL not < 90), then proceed to the step-2 diet.
The step 2 diet limits saturated fat to less than 7% of total calories and cholesterol intake to less than 200 mg/day. Medications that reduce cholesterol such as lovastatin should be used if diet doesn't work. Those that are overweight should diet to reduce weight by 5 lbs/month till normal before starting any cholesterol lowering medications as reduction of weight is more effective than changes in diet or medication. Medication may be indicated when response to diet is inadequate. Patients with high cholesterol should avoid use of medications in the "beta blocker" family as well as in the "thiazide" diuretic family. Both of these types of medications are commonly used for control of blood pressure.
Comment on dietary treatment: While lowered cholesterol and avoidance of being overweight reduces stroke risk, there is disagreement about whether or not restriction of dietary fat avoids stroke. Gilman et al (1997) reported that dietary fat intake was inversely associated with stroke risk, with the lowest age-adjusted cumulative stroke rate in men for individuals who had a total fat intake of calories amounting to 50% of their caloric intake, and three times greater incidence for men with 26% intake. An alternative to the arduous and rigorous dietary treatment that would take this into account this observation might be to combine a higher unsaturated fat intake with drug treatment (see below), and avoidance of obesity through reduced caloric intake.
A second issue is that it is very clear now that drugs that lower overall cholesterol decrease cardiac risk. It seems likely that the same will be shown in the future for stroke. This again might make one inclined to use drug treatment for cholesterol early on.
Drug Therapy for hyperlipidemia: In recent years it has become clear that drugs that lower cholesterol can significantly reduce morbidity from vascular disease. Heart attacks, in particular, are reduced by roughly 30% starting 6 months after beginning treatment in individuals with elevated cholesterol. Although at this writing there are no published studies regarding stroke, it seems likely that "statin" drugs eventually be shown to reduce risk by about 25% in stroke and TIA (Strauss, 2002). The trend in vascular medicine is to use these agents earlier and with a lessened emphasis on dietary treatment. A target of 100 mg/dL for LDL is thought to be appropriate (Strauss, 2002). The vast majority of patients with a history of ischemic stroke or transient ischemic attck could benefit from statin use (Stroke, 2004).
At this writing, Lescol is the least costly treatment for low risk patients who require LDL reductions of 15-25%. Pravachol is an intermediate potency agent, and Lipitor is suitable for patients who require very substantial reductions. Niacin and bile acid agents such as Questran are also effective agents, but side effects limit their usefulness. A list of agents follows.
|Brand Name||Generic Name||Dose|
|Nicolar||Niacin||1 g BID|
|Lescol||fluvastatin||40 mg daily|
|Colestid||colestipol||10 g/day divided|
|Lipitor||atorvastatin||10-40 mg daily|
|Zocor||simvistatin||10 mg daily|
|Pravachol||pravastatin||20 mg daily|
|Mevacor||lovastatin||20 mg daily|
High blood pressure, particularly systolic pressure, should be rigorously controlled. A reasonable target is below 130/90. There are presently many highly effective medications for blood pressure. A reasonable treatment in many is a combination of an ace-inhibitor and a diuretic. This subject was recently reviewed by Messerli et al (2002) as well as Strauss (2002). It remains unclear how acutely and by how much blood pressure should be lowered after a stroke. Present thought is that all but the highest blood pressures should be left to settle spontaneously in the acute setting (Strauss, 2002).
Diabetes should be carefully regulated. Those with heart problems should get advice from a cardiologist.
Estrogen replacement where appropriate is associated with a 25-50% reduction of risk from heart disease as well as 15% decrease in LDL and 15% increase in HDL. Estrogen use may also reduce the risk of osteoporosis. A potential increased risk of breast cancer remains.
Life style : Persons with a sedentary life style are at higher risk for stroke than those with active life styles. Persons who have had TIA, in general, should not restrict their activity, but rather, might even consider increasing activity. Driving, swimming, and operation of potentially dangerous equipment is obviously risky. While recommendations must be individualized, we do suggest caution and if possible, avoidance of these activities.
Vitamen supplements. Low serum homocysteine levels is correlated with a modest reduction in the risk of ischemic heart disease and stroke (The Homocysteine Studies Collaboration, 2003). Folate supplementation is proabably reasonable in persons with low homocysteine.
Atrial fibrillation affects roughly 2.3 million adults in the United States. The prevalance is high -- nearly 4% of persons aged 60 years or older and nearly 9% of those aged 80 or older (Waldo, 2004). Compared with persons having a normal heart rhythm, persons with atrial fibrilation have a 4 to 5 fold increase in the liklihood of stroke. Several studies involving atrial fibrillation (AF) patients have been conducted. Analysis of several trials revealed that risk of stroke can be reduced by 68% by giving warfarin (coumadin). Aspirin alone reduces risk by about 36%. In AF patients < 65 years of age with no other risk factor, the risk of stroke is about 1% per year, which has lead some to the conclusion that treatment with coumadin is not warranted. In AF patients older than 65 years of age or less than 65 with one or more risk factors, data strongly supports the use of warfarin to reduce stroke.
After a stroke has been sustained in the context of AF, coumadin (warfarin) reduces risk of stroke by 67% compared to 18% for aspirin.Tight control of the INR is very desirable -- it should be between 2-3.5 in patients less than 80 years old, and 2-3 in those greater than 80 years old.
Recent data suggests that mobile cardiac telemetry may be indicated to occult atrial fibrillation (Tayal et al, 2008). This is a device similar to a Holter monitor.
Carotid endarterectomy is beneficial in persons with symptomatic carotid disease and severe carotid stenosis, defined as 70% to 99%. Benefits in persons with severe stenosis is a decrased risk of about 50%. In those marginal stenosis, between 50-69%, the risk reduction was less (about 27%). Persons with less than 50% stenosis were harmed by surgery according to the NASCET study (Strauss et al, 2002). Increased risk of surgery correlates with previous stroke, blood pressure greater than 180, older than 75 years, and history of peripheral vascular disease. Other vascular lesions in the brain also increased the risk of stroke (Strauss, 2002).
The brainstem graphic is courtesy of Northwestern University
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