Ultrasound Monitoring of Stroke Patients
Steven Novella, M.D.
Transcranial Doppler (TCD) testing uses sound waves to measure the speed with which blood flows through the large blood vessels within the head. The test can detect constriction (narrowing) of blood vessels as well as blood flow abnormalities related to cerebrovascular disease. In vasoconstrictive strokes, blood vessels to the head are narrowed, delivery of blood is reduced, and the brain suffers damage from lack of oxygen.
William M. Hammesfahr, M.D.,who practices neurology in Clearwater, Florida, advocates aggressive treatment of stroke patients with drugs to open the constricted blood vessels in an attempt to improve blood flow to the affected areas. He also recommends using TCD to monitor the progress of stroke patients. Hammesfahr's curriculum vitae describes his TCD laboratory as the Florida's West Coast's first for the treatment of stroke. During 1997, his Web site reported on four patients he has treated by this approach. Although the reports were favorable, there are at least five reasons for interpreting them skeptically.
1. The concept of dilating (widening) blood vessels to treat strokes runs contrary to prevailing evidence. Many studies using calcium channel blockers or vasodilators (blood-vessel wideners) with acute stroke have demonstrated that lowering blood pressure during a acute event is associated with a marked increase in the area of brain tissue damaged by the stroke. These studies, plus what it known about brain physiology, suggest that the increase in blood pressure resulting from a stroke is an attempt by the brain to increase blood flow to the ischemic (oxygen-starved) brain tissue. Decreasing blood pressure, therefore, worsens stroke.
2. Ultrasound studies have shown that the arteries supplying the ischemic brain tissue tend to be dilated, not constricted. In fact, they often are maximally dilated and cannot be dilated further, even with medications. In this situation, blood flow is directly related to blood pressure. Medications that lower blood pressure are therefore likely to decrease blood flow to injured brain tissue, not increase it.
3. Dr. Hammesfahr's cases included acute, subacute, and chronic stroke patients. He himself concludes that vasodilation "may also be used to treat acute, subacute and chronic neurological deficits after stroke." The mechanism of neurological deficit is not likely to be the same in these different stages of stroke. The deficits (weakness, inability to speak, etc.) of stroke victims that have lasted more than a few weeks, for example, are most often due to permanent brain damage, and do not depend on blood flow.
4. Four patients is far too small a sample from which to derive solid conclusions.
5. The case series was not controlled. To arrive at a reliable clinical conclusion, a much larger number of patients would have to be treated, followed with standard scoring mechanisms (not just the examination of one physician), and compared to a placebo-controlled group.
Hammesfahr's Web site also recommended TCD testing of "every patient who has a neurological deficit be evaluated for a vascular involvement and treated regardless of age or chronicity of the deficit." He claims that the test enables him to identify people at risk for vasospastic stroke before any clinical signs are apparent. This claim could be safely tested by determining whether people whose arteries he would consider constricted have more strokes than similar people with normal TCD results. To my knowledge, no such finding has been published.
TCD testing is useful for evaluating certain patients who have strokes. However, the routine testing and monitoring Hammesfahr recommends would result in considerable unnecessary expense. Florida Medicare regards vasodilation therapy for stroke rehabilitation or other brain damage as "investigational" and therefore does not cover the cost of TCD studies (CPT codes 93886, 93888) associated with this treatment .
Hammesfahr's Web site also claims that his method has produced "major improvements in patients suffering from traumatic brain injury, migraines, attention deficit hyperactivity disorder (ADHD) , and seizures." Postulating that ADHD can be improved by increasing blood flow to the brain, he reports on two adult sisters, ages 25 and 27, who improved over a 10-month period while undergoing his treatment in addition to psychotherapy, vocational counseling, relaxation therapy, and hypnotherapy. With this many factors at work, distinguishing what caused an improvement is not possible. Although Hammesfahr states that the patients performed better when TCD measurement showed increased cerebral blood flow, the test protocol lacked controls—so it is not possible to be certain that his observations were meaningful. Even if the observations were valid, the alleged blood flow increases were only temporary. (In a physically healthy individual, the brain regulates its own blood flow to within a very narrow optimum range.)
The theoretical basis for Hammesfahr's vasodilation treatment for stroke clashes with current knowledge about stroke physiology. In fact, the prevailing current belief is that such treatments should worsen stroke outcome, not improve it. I believe that vasodilation treatment for stroke patients should be done only as part of an approved peer-reviewed protocol that includes informed consent about the treatment's experimental status and possible risks. Because of the potential risk, I doubt that an institutional review board would permit such a study unless animal studies can demonstrate that the treatment is safe and potentially useful.
- 93886, 93888: Transcranial Doppler studies. The Florida Medicare B Update, Nov/Dec 1999.
Dr. Novella, a member of Quackwatch's advisory board, is Assistant Professor of Neurology at Yale University School of Medicine and president of the The New England Skeptical Society.
This article was revised on February 14, 2000.