NS-Clinical Correlation #4 -- Stroke


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NS-Clinical Correlation #4 -- Stroke

  1. 1. NS CC-4: Stroke Dr. Elkind April 19, 2001 (12-1pm) Transcriber: Llanyee Liwanpo (lil16@columbia.edu) PART 1: STROKE Stroke Morbidity and Mortality • Originally, it was estimated that 500,000 strokes occur in the United States each year (based on Framingham Study). However, this study was done on a homogeneous White population. Further studies that include minority populations show that the number is actually closer to 750,000 strokes each year. • Leading cause of serious, long-term disability • 3rd leading cause of death in America • 2nd leading cause world-wide • Accounts for more than 50% of all hospitalizations for acute neurological disease, especially since stroke patients do not always die from stroke but suffer significant disabilities Since the 1950s, there has been a significant decline in the incidence and mortality of heart disease and stroke. However, in the last decade, the numbers have begun to rise again. The cause of this trend is unknown, but it shows us that stroke is still a problem and further research must be done. Risk factors of stroke • Non-modifiable – these are risk markers for stroke o Age: Older age = higher risk o Gender: Men are at higher risk. However, because women live longer, there are more strokes occurring in women in terms of absolute numbers. o Race: Hispanics and Blacks have higher rates of stroke than whites o Heredity • Modifiable o Medical conditions  Hypertension – most important  Cardiac disease  Atrial fibrillation  Hyperlipidemia  Diabetes mellitus  Carotid stenosis  Prior stroke or TIA (Transient Ischemic Attack = same symptoms as stroke but lasting less than 24 hours) o Behaviors  Smoking  Sedentary lifestyle  Heavy alcohol use (However, similar to studies of heart disease and stroke, moderate use appears to have protective effects against stroke.) Northern Manhattan Stroke Study • Blacks have the highest incidence of stroke • Hispanics have the next highest incidence
  2. 2. • These results were found, even with adjustments made for socioeconomic differences. So what is a stroke? • According to the World Health Organization (1980): Stroke = “rapidly developing clinical signs of focal or at times, global disturbance of several functions, lasting more than 24 hours or leading to death, with no apparent cause other than that of vascular origin.” • Basically, it’s just saying that a stroke is “what a stroke looks like.” • TIA= same symptoms as stroke but lasting less than 24 hours  Shown: MRI scan of 50-yr-old male patient with history of atrial fibrillation who exhibited 5 minutes of slurred speech • The scan shown is a special MRI called Diffusion Weighted Imaging – very sensitive to early signs of ischemia • A bright white spot appears, indicating ischemia in that region of the brain • This illustrates the fact that even transiently occurring symptoms will do some damage to the brain. Therefore, the traditional definitions of stroke and TIA as being more or less than 24 hours, respectively, are mistaken. • Longer-lasting symptoms are more likely to cause damage to brain tissue, but transient symptoms are just as serious and will also cause damage. Therefore, patients suffering TIAs should NOT be sent home—they must get evaluation and treatment ASAP. • Therefore, the actual pathophysiological cause of the stroke/TIA is more important than the duration of symptoms. • Today, physicians take TIAs seriously and use it as a warning sign of what could happen UCLA Study showing relationship between likelihood of finding abnormality on MRI and duration of TIA (bar graph shown) • Longer-lasting symptoms = more abnormalities seen • Interestingly, approximately 70% of patients with symptoms lasting 12 to 24 hours showed abnormalities on their MRI. This means that 30% of patients show no abnormalities on their MRIs! These patients may be in a “gray zone”: their brain function is affected because of inadequate blood flow, but they have not yet developed a full stroke. Perhaps if we treat them early enough, they will have better recovery. Major blood vessels of the brain • All vessels connect at the base of the brain via the Circle of Willis => collateral flow here allows the brain some resistance to ischemia Vascular distribution • Middle cerebral artery • Anterior cerebral artery • Posterior cerebral artery Functional anatomy, i.e. visual cortex, Wernicke’s area, primary motor and sensory cortex • Knowledge of anatomy allows us to determine what functions are affected when a particular blood vessel is blocked • For example, in a right-handed person who has a stroke on the right side of his/her brain o Language function is unaffected
  3. 3. o Hemi-neglect = loss of awareness of the left side of body and external environment o Asomatagnosia = patients have no awareness of one side of their body, i.e. this patient may pick up his own left arm but not know that it is his. Types of stroke • Hemorrhagic o Subarachnoid (5-10%)  Blood vessel bulges and ruptures (especially at branchpoints), and bleeding occurs over the surface of the brain  Increased pressure  headache, nausea, vomiting, possibly coma o Intracerebral (10-15%)  Bleeding within the substance of the brain  An actual focal deficit occurs, i.e. weakness on one side of the body  Similar to ischemic stroke but because there is increased pressure, patient often also experiences headaches • Ischemic = blockage of blood vessel results in ischemia (75-85%) Salvaging the ischemic penumbra • Penumbra = meaning “shadow,” the surrounding area around the ischemic site • When a vessel is blocked, there is a core area that is severely affected and dies. The penumbra is subject to possible further damage as time progresses. The physician’s goal is to interfere with the cascade of events to limit the size of the infarct and shrink the penumbra. Effects of decreased cerebral flow • As blood flow decreases, there is a series of events that occurs: ISCHEMIA  PENUMBRA  INFARCTION Edema Na/K pump fails (decrease in ATP) Cell death Lactate collects Loss of membrane integrity Loss of electric activity • Stroke is not simply an acute occurrence; it is a process that we can interfere with before it is completed. Reversible and irreversible ischemic thresholds • Time is an important factor: o If blood flow goes to zero (as in cardiac arrest), there is irreversible brain cell death. o If there is still some blood flow, there is a window of time over which the damage is reversible. • Based on experiments done on monkeys:
  4. 4. o If blood flow is high enough, reversible state will last rather long. • In acute strokes, high blood pressure keeps the patient’s brain alive, so it is not a good idea to decrease his/her blood pressure because it cause irreversible damage. Therefore, physicians do not treat high blood pressure aggressively in cases of acute stroke. ***In other words, the amount of blood flow and the time determine how long the brain can live.*** Ischemic stroke subtypes in Northern Manhattan study (pie chart shown) • Cryptogenic (32%) - cause unknown • Lacunar (27%) – small strokes due to blockage lenticulostriate arteries • Cardioembolic (20%) – i.e. a blood clot breaks off from the heart and reaches the brain • Intracranial atherosclerosis (9%) • Extracranial atherosclerosis (8%) • Other (4%) PART 2: CLINICAL CASES Case 1: 70-year-old right-handed female History: Two prior ischemic strokes Current Symptoms: 2 months of jerking of right arm and leg, lasting a few seconds Loss of power in right hand on one occasion Fell twice because right leg weakness Two episodes of vision loss in the inferior field of the left eye in the past two months White spot appears in the left eye when she looks into the light CT scan Diagnosis: Left carotid artery stenosis Her episodes are TIAs due to decreased blood flow because deficits are not long-lasting The episodes of visual loss are also a marker of risk to the brain since the same vessel that supplies the eye (i.e. carotid artery) also supplies the brain. These episodes of transient visual loss are called transient monocular blindness (TMB) or amaurosis fugax (fleeting blindness) [The last point was not mentioned in class, but Dr. Elkind told me that it was something worth knowing.] Case 2: 63-year-old female History: Pulmonary embolism, complicated by stroke  caused left hemiparesis and remote shaking Current Symptoms:
  5. 5. Acute onset fall Left hemiparesis occurring at 10:30pm Admitted into ER at 10:50pm Exam: High blood pressure (180/110) but spontaneously decreases (146/99) Little speech output Follows simple commands Hemi-neglect on left side Severe left hemiparesis Left facial droop Mild loss of sensation on the left side Right gaze preference NIH stroke scale = 17 MRI done Diagnosis: Ischemic stroke, resulting in infarction of right side and small region of left side -Since stroke occurred on both sides at the same time, the clot must be from a proximal site (i.e. the heart); -The patient had a patent foramen ovale that caused a right to left shunt, allowing the clot to travel from leg to the right side, cross over to the left side of the heart, and up to the brain. This fits in well with her history of pulmonary embolism (= blood clot to the lungs). Treatment: Patient was given a thrombolytic agent (TPA) to dissolve the clot, but TPA must be given within a 3 hours timeframe. Next day, patient was alert and awake, showing improvement. Case 3 - 73-year old Current Symptoms: Left gaze deviation Aphasia Mild hemiparesis Lasting 5-7 hours Exam: CT scan Angiogram Diagnosis: Blockage of anterior and middle cerebral artery Even though symptoms lasted 5-7 hours, patient’s deficits were not severe because there was still some collateral flow to the motor strip. Treatment: Blood thinner given directly through a catheter to restore flow to that area. Case 4: 85-year old male History: Mild hypertension Current Symptoms: Increasing right side hemiparesis Slurred speech, hoarse voice Weakness in right arm Dragging and decreased strength of right leg
  6. 6. Right hand pronator drift Diagnosis: Left-sided stroke -Since patient’s speech is unaffected, middle cerebral artery is not involved. -Since cognition is unaffected and there is weakness in right face, arm, and leg, a small stroke occurred deep within the white matter, specifically in the pons in this particular case. (However, it could have occurred anywhere along the white matter pathways). This is called a pure motor stroke, due to blockage of a branch of the basilar artery that affects the descending motor tracts there.
  7. 7. Right hand pronator drift Diagnosis: Left-sided stroke -Since patient’s speech is unaffected, middle cerebral artery is not involved. -Since cognition is unaffected and there is weakness in right face, arm, and leg, a small stroke occurred deep within the white matter, specifically in the pons in this particular case. (However, it could have occurred anywhere along the white matter pathways). This is called a pure motor stroke, due to blockage of a branch of the basilar artery that affects the descending motor tracts there.