Stroke is a neurological deficit resulting from interruption of blood supply to the brain. It is one of the leading causes of death and disability and remains one of the diseases most resistant to treatment. The most common type is thrombotic stroke where a blood clot forms in a major artery due to disease of the artery. This is very similar to myocardial infarction, also known as a heart attack. Less common types of stroke include embolic stroke where a blood clot travels from the heart or a major artery to lodge in a brain artery and hemorrhagic stroke where a cerebral artery ruptures and bleeds. Since the entire body and brain are under vascular pressure from the arterial side (mean blood pressure about 90) to the venous side (mean pressure about 0) interruption of blood supply creates a low pressure zone at the center of the blood deprived area. The brain is not equipped with alternate large arteries that can immediately supply fresh blood to a damaged area so the injured brain must depend on blood trickling in from the tiny peripheral capillaries. As this blood proceeds to the center of the stroked region it passes down a pressure and oxygen gradient with each successive millimeter of brain extracting more oxygen. The resulting brain pathology is one of concentric shells of brain tissue of different degrees of oxygenation. These different levels of oxygenation determine different levels of brain cell function. This description of the stroke lesion is the classic umbra/penumbra model (35). The umbra represents the most oxygen depleted core of the lesion that dies. The penumbra is the outer shell which consists of injured potentially salvageable brain tissue (see diagram right).

The most important question in stroke is how long can the umbra and penumbra survive before blood flow and oxygen are reestablished. Medical dogma through 1989 rigidly assumed that 6 minutes was the maximum time before the umbra died and possibly 30-60 minutes for the penumbra. In 1990 Dr. Neubauer published the "Idling Neuron" (21) letter to the editor of The Lancet that shattered the existing dogma by showing with SPECT brain imaging and hyperbaric oxygen therapy survival of the penumbra for 14 years in a 60 year old stroke victim. That patient recovered partial neurological function with a combination of hyperbaric and normobaric oxygen therapy delivered over a course of about one year, 14 years after her severe stroke. While this case is unusual other cases exist in the medical literature and Dr. Harch's hyperbaric experience. Unfortunately, there is no foolproof method to determine the amount of penumbra that is still recoverable days to years after stroke. SPECT brain imaging is one possibility when performed before and after a single hyperbaric treatment (see case below), but often a trial course of HBOT is the only method.

HBOT for acute and chronic stroke is based on Henry's Law which states that the amount of a gas, e.g. oxygen, that is dissolved in a liquid solution, e.g. blood, is proportional to the pressure of the gas interfacing with that solution. Since nearly 98-99% of hemoglobin in blood is saturated with oxygen at sea level all additional oxygen added by hyperbaric oxygen exposure is dissolved in the liquid plasma portion of the blood. It is this dissolved oxygen that exerts its drug effect on the pathology and pathophysiology in stroke and the other neuropathologies described on this website. In the history of hyperbaric medicine over 30 animal studies and 25-30 human studies have been published on HBOT in stroke. The best review of these is in Chapter 17 of the Textbook of Hyperbaric Medicine by K. K. Jain, 3rd Edition, 1999. The data is overwhelmingly positive in the animal studies and mostly positive in the human studies, but the human trials have lacked rigor. This discrepancy was the impetus for the newly launched HOTFAST (Hyperbaric Oxygen Therapy For Acute Stroke) Trial which commences in the Fall of 2000 at a number of centers in the United States. The project consists of three phases that will span 5-10 years if funded (see the end of this website): a first phase to assess feasibility and safety, a second phase to evaluate the proper dose, and a third phase to assess effectiveness. Coordination of the study is through the National Stroke Research Center in Winston-Salem, North Carolina and the Department of Biostatistics at the University of Alabama, Birmingham with Drs. James F. Toole and Paul G. Harch as the principal investigators and Dr. Richard Neubauer as the senior honorary consultant. While some studies are underway in chronic stroke increasing data is accumulating that is strongly suggesting that chronic stroke may be treatable with HBOT. Such a case from Dr. Harch's practice is presented below.

Case Presentation:

The patient is a 68 year old male complaining of persistent light-headedness since his third stroke nearly two years ago. The dizziness was of such severity that his balance and gait were affected and the patient became housebound and cane dependent. In addition he had weakness in his left leg, hyperextension problems with the left knee, trouble controlling his left arm, and incoordination on his right side. MRI of the brain showed multiple white matter strokes. SPECT brain imaging was performed before and after a single low-pressure HBOT and is displayed in Figures 1 and 2. The images are transverse with the first scan on the left and the second scan on the right of each figure and proceed from the top to the base of the brain. Note the global increase in brain blood flow (more yellow), increased smoothness and symmetry, and increased flow to the right cerebellum and temporal lobe (third, fourth, and fifth rows of Figure 2). On the basis of this change and the patient's subjective improvement he underwent a course of low-pressure HBOT and experienced marked reduction of his dizziness, improved ability to walk without a leg brace and cane, better balance and coordination, and notable improvement in his previously depressed mood. Repeat SPECT brain imaging reflected these gains as shown in Figures 3 and 4 which are side by side comparisons of the first scan to his final scan. The changes first noted in the second scan after a single HBOT (above) are now reproduced in the final scan and felt to be more permanent. Three dimensional reconstructions of all three scans are shown in Figures 5, 6, and 7 in the frontal face view. Note the generalized improvement in the surface of the brain and the dramatic increase in flow to the patient's right temporal lobe and cerebellum.

21. Neubauer RA, et al. Enhancing "idling" neurons. Lancet, 1990;335:542.

35. Astrup J, Simon L (1981) Thresholds in cerebral ischemia -- The ischemic penumbra. Stroke 12:6, 723-725.