Stroke is the common term for damage to the brain due to problems with the blood vessels in the head or neck. Stroke can be considered a “brain attack,” involving brain damage due to blood flow difficulties.Cerebrovascular disease is the most common neurological condition that results in hospitalization. Worldwide, it is the second most common cause of death and the most common cause of disability.Strokes can be ischemic (due to lack of adequate blood flow) or hemorrhagic (due to bleeding in or around the brain).
Inadequate blood flow results in not enough oxygen or glucose reaching the brain cells, leading to cell death. There often is a stroke “core” where there is no blood flow that results in near immediate cell death, as well as an ischemic “penumbra” where there is inadequate blood flow for full function, but the cells have not yet died. This “penumbra” is often the target that emergent therapies try to save.
Transient Ischemic Attack (TIA)
TIA is a transient and resolved neurological symptom that was caused by temporary inadequate blood flow to a region of the brain. In the past, TIA was defined by symptoms lasting specific durations of time, but more recently experts agree that TIA should not result in permanent brain cell death. If there is evidence of brain cell death (such as with MRI) it should be termed a stroke.
The symptoms of TIA can be the same as for stroke, with the caveat that the symptoms resolve.
TIA is a major risk factor for an impending stroke. A person who has a TIA has an up to 17% chance of having a subsequent stroke within the next 90 days. It is important that a Neurologist investigate the cause of a TIA so that a permanent stroke can be avoided through risk factor modification.
The symptoms of ischemic stroke tend to have a sudden onset and are most severe within seconds to minutes. The deficits then often progressively improve over time, although the degree of improvement is variable and dependent on location of the stroke and other issues.
The precise symptoms of stroke vary greatly based on the location of the stroke. Most typically, the opposite side of the body from the stroke is affected, although there are exceptions in the brainstem and cerebellum.
Strokes may cause paresis (weakness), plegia (complete loss of movement), sensory loss, tingling, vision loss, dysarthria (thick or inarticulate speech), aphasia (language difficulties such as trouble expressing thoughts with word finding difficulty or difficulty understanding the speech of others), incoordination or clumsiness, dysphagia (difficulty swallowing), diplopia (double vision), facial droop, or other symptoms.
Because of the wide variety of symptoms that can present, any time there is a sudden onset of a neurological change, it is important for the medical provider to consider stroke.
A helpful tool has been developed to aid people to quickly recognize possible symptoms of a stroke and get the patient to the hospital as soon as possible, so as to try to save as much brain and function as possible. This utilizes the acronym “BE-FAST”
- Balance – did a person suddenly have new onset of difficulty with balance?
- Eyes – is there a sudden loss of vision or double vision?
- Face drooping – is one side of the face suddenly drooping or numb? Have a person smile in order to evaluate this more thoroughly, evaluating for asymmetry in facial movement.
- Arm weakness – is one arm suddenly weak or numb? Have a person hold both arms out in front, watching to see if an arm drifts down.
- Speech difficulty – is there a sudden change in the person’s speech or language? Is the speech more slurred? Can the person understand you, and can you understand the person?
- Time – if the person shows any of these symptoms, it is the time to call 9-1-1. The sooner a person receives treatment for ischemic stroke, the better chance the person has of a good outcome.
Significant advances have been made in diagnostic imaging in stroke, with newer advanced functioning imaging such as CT perfusion. There are a variety of tests during ischemic stroke evaluation, as outlined:
- CT of the head is done immediately, so as to rule out a hemorrhagic (bleeding) stroke. This must be ruled out before thrombolytic therapy can be considered.
- Perfusion imaging is done, either with CT or MRI technology, as a functional test to see what areas of the brain are completely “dead” or “unsalvageable” from stroke and what areas are “penumbra,” or tissue at risk that can still be salvaged by restoring blood flow.
- Vascular imaging is pursued to evaluate for narrowing or blockages in the arteries in the head or neck. This may involve CT technology, MRI technology, or ultrasound. These tests are referred to as an “angiogram,” denoting that it is mapping of the blood vessels.
- MRI of the brain is done to confirm or rule out the presence of ischemic stroke, which results in a typical finding of “restricted diffusion.” This can show the stroke volume, but also is helpful for noting the pattern of stroke in the workup for the cause of the stroke. MRI can also evaluate for bleeding, even if it has happened in the remote past.
- Cardiac evaluation is pursued, as many strokes may be cardioembolic – caused from clots that went to the brain from the heart. This includes an ECG, echocardiogram (ultrasound of the heart), and often prolonged heart rhythm monitoring
- Blood tests include a lipid panel to address cholesterol and hemoglobin A1c to evaluate for diabetes. In certain circumstances, other detailed tests to look for underlying causes for a person to have a higher likelihood of forming blood clots or having excessive inflammation are run.
Stroke care is on the forefront of medicine, with frequent advances in stroke treatment. The modern Neurologist has many tools.
- Thrombolysis involves the process of using “clot-busting” drugs to restore blood flow to the brain. As these medications (such as Alteplase and Tenecteplase) actively break down clots, there is a bleeding risk. In an effort to lower the risk of bleeding, there are restrictions on who can receive these medications. This has been shown to improve a person’s functional outcome, especially at 90 days after the stroke. A person typically has to have been known to be “well” (not have any stroke symptoms) within the past 4.5 hours prior to giving thrombolytics, but recently advanced use of MRI brain and perfusion imaging has allowed use in special circumstances beyond this.
- When a person meets detailed criteria to ensure that there is brain tissue that can be salvaged and there is evidence of a large blood clot in a blood vessel in the brain, neuro-interventional procedures can be done to remove the blood clot and restore blood flow. A Neuro-interventionalist places a catheter through the femoral artery in the thigh or the radial artery in the wrist and navigates the catheter under fluoroscopy (live Xray) to the location of the clot. Then a suction device or stent device is used to remove the clot and restore blood flow. This has been shown to dramatically improve a person’s functional outcome, especially at 90 days after the stroke.
- While high blood pressure over a long period of time increases the risk of stroke, letting the blood pressure be higher in the first 48 to 72 hours can help with blood flow to the area of stroke. This is termed “permissive hypertension.”
Evaluation of cause of ischemic stroke
After acute management, the focus turns to fervently searching for risk factors or cause of the stroke. By identifying these risk factors, they can be aggressively modified to reduce the risk of another stroke.
Large vessel atherosclerosis
- Large vessel atherosclerosis involves narrowing or stenosis of the large blood vessels, such as the carotid artery in the neck. This can result in pieces of the atherosclerotic disease dislodging and traveling to the brain, or simply inadequate blood supply to the regions supplied by the blood vessel due to slow flow through a severe narrowing.
- Cardioembolism refers to a blood clot that began in the heart and traveled to the brain. The most common cause would be an irregular heart rhythm called atrial fibrillation, in which the top portion of the heart “quivers” and does not pump well, resulting in blood clots forming that can travel to the brain. Other less common causes include atrial myxomas (an abnormal tissue), a patent foramen ovale and paroxysmal embolism (a blood clot going to the brain due to a hole in the heart), or infective endocarditis (an infection on the heart valve).
Small vessel ischemia
- Small vessel ischemia – involving blockages of the tiny lenticulostriate blood vessels – is typically due to risk factors such as hypertension (high blood pressure), high cholesterol, and smoking.
Stroke of other determined etiology
- Other less common known conditions can result in stroke, such as arterial dissection (tearing of the blood vessel), vasculitis (inflammation of the blood vessel), RCVS (sudden constriction of a blood vessel), venous sinus thrombosis, hypercoagulable conditions (conditions that may be genetic or acquired where a person is more likely to form blood clots, such as Protein S deficiency, Factor V Leiden mutation, or others).
Stroke of undetermined etiology
- During hospitalization, the workup may fail to show a clear cause of stroke. Some studies have shown this occurs in up to 40% of strokes. This is called “cryptogenic,” meaning “hidden cause.” The Neurologist will do an extensive evaluation after leaving the hospital to attempt to find the cause. This often involves prolonged cardiac rhythm monitoring to evaluate for infrequent undiagnosed atrial fibrillation, or other blood or genetic testing.
Prevention of ischemic stroke
Prevention of ischemic stroke relies on controlling modifiable risk factors, utilizing appropriate medications, and pursuing surgical procedures where indicated. Primary prevention refers to efforts taken to prevent a person from ever having a stroke, whereas secondary prevention is when a person has had a stroke and the efforts are taken to prevent yet another stroke.
Primary prevention involves surveillance for the development of risk factors for stroke and addressing those aggressively. Blood pressure should be controlled (either BP less than 140/90 or 130/80 depending on other patient features), statin medications should be used for elevated cholesterol (generally a high intensity statin under the age of 75 or a moderate intensity statin above that, with a typical goal of LDL<70), blood sugar should be controlled (goal of avoiding diabetes, or HgbA1c<=7% in the setting of diabetes), and people should stop smoking. If there is severe carotid artery narrowing, surgical intervention can be considered. Dietary and lifestyle changes can help lower risk of stroke, including adequate aerobic exercise and a healthy diet. Obesity should be addressed, as this is an independent risk factor for stroke.
While the same measures as primary prevention should be taken, in the case of secondary prevention additional detailed changes can be made to lower the risk of stroke depending on what is discovered to be the cause of the stroke.
Large vessel atherosclerosis
- Antiplatelet (such as aspirin or Plavix) and statin (such as atorvastatin or rosuvastatin) are used, and patients are evaluated for candidacy for surgical intervention of the narrowed artery.
- With the carotid artery, if the degree of stenosis is equal to or more than 70% and is the cause of the stroke, intervention is warranted. Intervention may be considered between 50-70%, but that is individualized. Carotid endarterectomy (an open surgery involving an incision in the neck to remove the narrowing) is generally preferred over carotid artery stenting, although individual cases may vary.
- In the setting of atrial fibrillation, stronger anticoagulants are used to significantly reduce the risk of stroke. This includes options such as warfarin, apixaban, rivaroxaban, or dabigatran.
- In the setting of a patent foramen ovale, the person should be evaluated for a closure procedure.
- If infective endocarditis is present, IV antibiotics are used, with a rare need for surgery.
Small vessel ischemia
- In addition to the intensive focus on addressing blood pressure control, statin medication, and tobacco cessation, antiplatelets (such as aspirin or Plavix) are used.
Stroke of other determined etiology
- The determined etiology will be addressed directly. Dissection may be treated with antiplatelets or anticoagulation, vasculitic processes will be treated with steroids or immunosuppressants, venous sinus thrombosis is treated with anticoagulants, hypercoagulable conditions are treated with anticoagulants, etc.
Stroke of undetermined etiology
- Aspirin and statin are used while an aggressive comprehensive evaluation for the cause of stroke is pursued. If an underlying cause is discovered – such as infrequent atrial fibrillation – that is addressed as in the above categories.
- There are ongoing clinical trials in place about other options in the setting of stroke where the cause continues to by cryptogenic.
Hemorrhagic (bleeding) stroke is less common than ischemic stroke, but it can cause significant disability and has a higher rate of death.
Hemorrhagic stroke can involve bleeding in the brain (intraparenchymal hemorrhage), around the covering of the brain (subarachnoid hemorrhage – SAH), or between the brain and the skull (subdural or epidural hemorrhage).
Hemorrhagic stroke results in focal neurological symptoms like ischemic stroke, but typically there is more headache, more nausea, a high incidence of loss of consciousness, and the symptoms tend to progress more slowly than in ischemic stroke.
Diagnostics / Evaluation of cause of hemorrhagic stroke
- CT of the head is the most important tool to diagnosis active bleeding in the brain.
- Vascular imaging (such as CTA or MRA) is often done to evaluate for an underlying vascular abnormality (discussed below).
- MRI of the brain can evaluate for evidence of previous remote bleeds or an underlying tumor that could have bled.
- Transcranial Doppler (TCDs) may be pursued after SAH, as they can sense a delayed vasospasm that occurs after SAH and must be treated.
- Blood pressure control is a mainstay of managing hemorrhagic stroke. In the setting of bleeding within the brain itself, infusions (such as nicardipine) are used to bring the blood pressure down, most typically with a systolic blood pressure between 140 and 180.
- Any bleeding disorders are corrected. This could involve giving reversal agents for anticoagulants or using medications or transfusions to counteract the effect of an antiplatelet like aspirin or Plavix.
- A neurosurgeon will address if there is any need for an external ventricular drain (EVD) to relieve hydrocephalus (a build-up of fluid in the brain) or need for a surgical procedure to drain the blood in the brain.
- If found, a vascular malformation should be addressed. This is sometimes done with open surgeries and sometimes with endovascular procedures from within the blood vessel.
Prevention of hemorrhagic stroke
Like ischemic stroke, it is important to work to prevent hemorrhagic stroke. Blood pressure control, cautious use of blood thinners, tobacco cessation, and avoiding illicit substances like cocaine are important. Occasionally, an incidentally found vascular malformation should be addressed.
- A cerebral aneurysm is an outpouching of a blood vessel due to a weakening in the vessel wall. Aneurysms can occasionally contribute to headache, cause symptoms from mass effect (such as compressing a cranial nerve), or can rupture and cause aneurysmal subarachnoid hemorrhage. A host of factors – including location of aneurysm, size of aneurysm, family history of aneurysm – can influence the risk of growth of an aneurysm and risk of rupture. Smoking increases the risk of cerebral aneurysm. There are familial and genetic components to aneurysms. Aneurysms can be treated with open surgical procedures involving clipping of the aneurysm or endovascular placement (from within the blood vessel) of metal coils or flow diversion devices.
Arteriovenous Malformation (AVM)
- An AVM is an abnormal tangle of blood vessels that has high blood flow through it. This can rarely result in headache, seizure, or ringing in the ears. The most common presenting symptom for AVM is rupture and hemorrhage in the brain, but most people with AVM never have a hemorrhage. Intervention for AVMs should involve a thoughtful multidisciplinary team. Options for treating AVMs include endovascular ablation and/or open surgical resection.
- A cavernoma is a local dilated abnormal blood vessel that has very little flow through it. Because of the low-flow state, these are quite low risk for hemorrhage in to the brain. Cavernomas can put someone at risk for having seizures, depending on the location. However, cavernomas are typically asymptomatic. There are genetic conditions that can result in many cavernomas. Most commonly, cavernomas do not warrant surgical intervention.