Stroke

Introduction

 

The normal functioning of the brain is directly dependent on the blood circulation system. Namely, the brain’s blood vessels supply oxygenated blood, glucose, and nutrition to all brain processing areas to maintain their proper functioning. 

 

When blood circulation in the cerebral cortex is obstructed and cannot reach the cortical structures, a stroke occurs. 

What Is a Stroke?

 

A stroke is a cerebrovascular disease that affects the brain’s blood-supplying vessels. It’s a medical emergency that can lead to sudden death.

 

A stroke occurs when the blood vessels of the brain become clogged or ruptured. The blockage of blood circulation cuts off the oxygenated blood supply from the cortical structures. The lack of oxygen impairs the brain’s function and leads to the destruction of neuron cells. 

What Are the Major Blood Vessels of the Brain?

 

The carotid arteries and two vertebral arteries are the brain’s major blood-supplying vessels. When these two vertebral arteries form one blood-supplying unit at the skull base, they are referred to as a basilar artery. 

 

On the other hand, when the basilar artery joins the other blood supplying arteries of the cerebral cortex, they form The Circle of Willis. 

The Carotid Arteries

 

The carotid arteries are the brain’s major blood supplying vessels. They conduct oxygen and nutrition to the facial structures, the neck, and the cerebral cortex. 

 

These arteries are positioned on each side of the neck and branch into two blood supplying sub-systems:

• The internal carotid artery – This blood vessel supplies blood to the cerebrum structures located in its back area. It branches into the cervical, intracranial, and petrosal artery.  
• The external carotid artery – The facial structures and the neck receive blood from the external carotid artery. This artery branches into the superior thyroid artery, lingual artery, posterior auricular artery, occipital artery, ascending pharyngeal artery, maxillary artery, superficial temporal artery, and the facial artery. 

The Vertebral Arteries

These paired arteries branch into four sections:

• The pre-foraminal division;
• The foraminal division;
• The extraspinal (or extradural) division;
• The intracranial (or intradural) division.

 

 

The vertebral arteries supply nutrition and oxygen to the cerebellum, the brain stem, the upper part of the spinal cord, and the back part of the cerebral cortex.

The Basilar Artery

The basilar artery is formed by the fusion of the left and right vertebral artery. The brain stem and the cerebellum are the brain structures that receive oxygenated blood and nutrition via this blood vessel. 

 

This artery branches into several other blood-supplying branches, such as:

• The labyrinthine artery;
• The upper cerebellar artery;
• The lower back cerebellar artery;
• The pontine branches of the basilar artery.

The Circle of Willis

The Circle of Willis is formed when the basilar artery, the internal carotid arteries, the front cerebral arteries, and the front and the back communicating arteries fuse in a blood-supplying system of the brain. 

What Are the Types of Stroke?

Based on the causes that lead to a stroke, modern medicine differentiates between the following types of stroke::

• Ischemic Stroke;

• Hemorrhagic Stroke;

• TIA (Transient Ischemic Attack) Stroke;

• Cryptogenic Stroke;

• Brain Stem Stroke;

• Cryptogenic Stroke. 

Ischemic Stroke 

When a blood clot blocks a blood vessel in the brain and obstructs the supply of oxygen and nutrition to the brain, it leads to an ischemic stroke. The vast majority of strokes are ischemic.

What Are the Causes of an Ischemic Stroke?

A plaque is a combination of fat, calcium, cholesterol, and other residues of the elements included in the brain’s blood supply system. Over time and due to some lifestyle habits, the plaque can build up and narrow the brain’s arteries. 

 

This accumulation that clogs the arteries is referred to as atherosclerosis – a disease that can cause inflammation of the blood supplying vessels and the brain. Also, due to the narrowed passaged and slow blood flow, clots can form and completely block the arteries of the brain, which always results in a stroke. 

What Are the Symptoms of an Ischemic Stroke?

The symptoms that point to an ischemic stroke are the following:

• Having high blood pressure values for a long time;
• Being of mature age;
• Having heart problems and diseases;
• Having a smoking habit.

What Are the Types of Ischemic Stroke?

There are 2 types of ischemic stroke:

• An embolic stroke, caused by a blood clot in the blood supplying artery of the brain;
• A thrombotic stroke results from a blood clot that has traveled to the brain via the blood supply system from another part of the body. 

Hemorrhagic Stroke

A hemorrhagic stroke occurs after bleeding in any part of the cerebral cortex due to a ruptured blood vessel. The bleeding exerts pressure onto the surrounding cortical structures, which causes damage to the neuron cells, impairs their function, or leads to neuron destruction. 

What Are the Causes of a Hemorrhagic Stroke?

 

Aneurysms (weak areas in the artery) and arteriovenous malformations (AVMs) are some of the leading causes of a hemorrhagic stroke. High blood pressure plays a prominent role as one of the primary triggers of stroke, due to the strain it puts on the walls of blood-supplying arteries. 

What Are the Symptoms of a Hemorrhagic Stroke?

The symptoms that point to a hemorrhagic stroke make up the following list:

• Brain bleeding (hemorrhage);
• Sudden loss of consciousness;
• Vomiting;
• Severe headache;
• Numbness of the facial structures;
• Numbness of the extremities;
• Partial paralysis of both the face and the body;
• Seizures;
• Sensitivity to sources of light;
• Impaired cognitive abilities;
• The inability of the affected individual to maintain posture and balance.

What Are the Types of a Hemorrhagic Stroke?

There are 2 main types of hemorrhagic stroke:

• The intracerebral hemorrhage occurs when blood from the pierced blood vessel spills among the surrounding tissues and structures of the brain.
• The subarachnoid hemorrhage, although not very common, occurs when blood from the ruptured blood vessel spills between the surrounding tissues and the brain.

TIA (Transient Ischemic Attack) Stroke

The transient ischemic stroke is sometimes labeled as a ‘ministroke’ due to the shortness of its effects. Namely, the circulation of blood in the brain is blocked for a very short time, unlike in other stroke types. 

What Are the Causes of a TIA (Transient Ischemic Attack) Stroke?

Blood clots are the primary cause of a transient ischemic stroke. However, high blood pressure, artery diseases, and some particular medical conditions (such as diabetes) are also risk factors. What Are the Symptoms of a TIA (Transient Ischemic Attack) Stroke?

 

This type of stroke is a warning sign since the blockage of the oxygenated blood supply to the brain lasts no longer than a few minutes. The symptoms include:

• Impaired physical abilities (inability to walk);
• Blurred vision (or even blindness on one of the eyes);
• Severe headache that occurs without any apparent reason;
• Mental confusion.

Cryptogenic Stroke

Unlike the other types of strokes that usually occur due to a blood clot that obstructs blood supply to the cortical structures, there is no apparent cause for a cryptogenic stroke. 

What Are the Causes of a Cryptogenic Stroke?

Since the cryptogenic stroke is sudden and short-lasting, the actual causes for its occurrence are hard to identify. Most often, a combination of several typical causes is the reason behind this type of stroke. 

What Are the Symptoms of a Cryptogenic Stroke?

The acronym F.A.S.T. has been created for the fast detection of a stroke. The initials refer to the main symptoms that ease the recognition of any type of stroke:

• F – face dropping;
• A – slurred speech;
• C – arm weakness;
• E – emergency (time to call 911).

Brain Stem Stroke

When a stroke occurs in the brain stem area, it’s labeled as a brain stem stroke. Since the brain stem is involved in regulating and controlling some of the most vital processes (breathing, language, and consciousness), a brain stem stroke can severely obstruct these functions. 

What Are the Symptoms of a Brain Stem Stroke?

While the affected individual can experience some of the common symptoms of a stroke (dizziness, inability to maintain balance, or a severe headache), the most characteristic symptoms of a stroke (such as partial paralysis of one side of the body) can be absent from the clinical picture. 

What Are the Warning Signs of a Stroke?

Since a stroke is a medical emergency, the symptoms usually occur suddenly and develop at a rapid pace. The affected individual may experience the following warning signs:

• Blurred vision;
• Inability to maintain concentration and alertness;
• Sudden confusion;
• Sudden problems with speech;
• Inability to understand spoken language;
• Sudden insensibility of face and body parts;
• Frequent vomiting;
• Loss of consciousness;
• Severe headache;
• Partial paralysis;
• Loss of ability to coordinate movements.

What Are the Risk Factors for a Stroke?

There are many risk factors regarding the lifestyle and health of a person that increases the possibility of a stroke. The list includes:

• High blood pressure;
• High cholesterol values;
• Smoking;
• Diabetes;
• Ischemia;
• Obesity;
• Hemorrhage;
• High levels of stress;
• Brain aneurysms;
• Advanced age;
• Rheumatoid arthritis or another inflammatory condition;
• Infections;
• Blood vessel diseases;
• Genetic predisposition;
• Sleep apnea;
• Migraine.

Cerebral Ischemia and Stroke

Cerebral ischemia refers to a condition that occurs when some part of the body stops receiving oxygenated blood and nutrition. The limited blood supply to the cortical structures obstructs vital processes by triggering the destruction of neuron cells, ischemic stroke, or cerebral infarction. 

 

Blood vessel problems, built-up plaque on the arterial walls, or blood clots cause this medical condition. 

Brain Hemorrhage 

 

Brain hemorrhage, or bleeding around the brain structures or between the cortical tissues, occurs after a rupture of the blood vessels, aneurysms due to increased blood pressure to the arterial walls, head trauma, etc.

 

When the brain hemorrhage is the result of some of the causes mentioned above, oxygen cannot reach the tissues where blood circulation has been obstructed. Left without oxygenated blood, the nerve cells located in the affected tissues die out in only a few minutes, leading to life-threatening conditions. 

Diabetes and Stroke

Diabetes mellitus (DM), or only diabetes, refers to a metabolic dysfunction resulting in abnormally high glucose levels in the blood. This chronic condition occurs due to the body’s inability to produce sufficient amounts of glucose, which is necessary for the energy of both the brain and the body’s tissues. 

 

The risk factors for diabetes mellitus include:

• Obesity;
• Cases of diabetes in the family (genetic heritage);
• Mature age;
• Polycystic ovary syndrome (PCOS);
• Physical inactivity;
• High cholesterol levels in the blood;
• A dysfunctional pancreas. 

Smoking and Stroke

Smoking imposes significant risks for overall health. The list of health hazards that occur due to smoking tobacco is quite long. It includes:

• Cancer;
• Heart diseases;
• Strokes;
• COPD;
• Diabetes,
• Lung diseases, etc. 

 

Smokers are more inclined to heart failures and high blood pressure, which is one of the major causes of stroke. If high blood pressure is already comorbid, the risk of a stroke is even higher.

 

The direct relation between smoking and stroke is the depletion of oxygen in the brain. Namely, smoking decreases the levels of oxygenated blood in the cortical tissues, which hinders the blood supplying arteries from pumping up blood faster. It also makes the blood platelets bond together, which may result in the formation of blood clots. 

What Are the Complications That Can Occur After a Stroke?

A stroke severely impairs the functions of the cortical structures. Since it also leads to the destruction of neuron cells, long-term disabilities, permanent brain damage, and so on, other medical problems are common. The list of complications that occur after a stroke comprises:

• Depression;
• Problems with memory;
• Impaired cognitive skills;
• Partial paralysis;
• Difficulty walking;
• Seizures;
• Development of dangerous blood clots;
• Inability to control bladder function;
• Loss of hearing and sight;
• A weakness of the muscles and the skeletal construction of the body;
• Pneumonia.

What Is Vascular Dementia?

When the reduced supply of oxygen and nutrients to the cerebral cortex structures suddenly triggers the occurrence of dementia, it’s referred to as vascular dementia. However, strokes are not always a cause of dementia.

What Are the Stages of Vascular Dementia Progression?

Vascular dementia develops gradually. The progression of this type of dementia that occurs after a stroke can be seen through 5 stages:

• Stage 1 doesn’t show any signs of impairment of cognitive abilities;
• Stage 2 displays some mild symptoms of a decline in cognitive abilities;
• Stage 3 the decline in cognitive abilities begins to accelerate; 
• Stage 4 shows moderate impairment of cognitive abilities;
• Stage 5 is a stage of severe impairment of the cognitive function of the brain.

What Are the Symptoms of Vascular Dementia?

 

The affected individual typically experiences the following symptoms:

• Inability to make decisions;
• Memory impairment;
• Anxiety and restlessness;
• Inability to maintain posture and balance;
• Apathy;
• Loss of will to participate in everyday activities;
• Inability to control the bladder;
• Inability to follow instructions or a plan;
• Confusion and lack of concentration.

How Does Stroke Affect Memory?

Memory loss and inability to focus and concentrate are some of the most severe complications after a stroke—the affected individuals face difficulty remembering some necessary everyday information, or what they were doing some moments ago. 

 

Also, they cannot return home by themselves, concentrate on a task or conversation, etc. Even reading a book can pose a real challenge to the patient who has suffered a stroke. 

 

Right after the stroke, the problems with memory are most apparent. However, memory can improve as the patient slowly recovers. 

Stroke Prevention Guidelines

The risk of stroke can be lowered by::

• Healthy nutrition on an everyday basis; 
• Practicing sports and physical activities; 
• Quitting smoking or any other similarly detrimental habit;
• Regulating blood pressure and blood sugar levels. 

Fun Facts

Did you know?

1. A silent stroke occurs with no visible symptoms but can cause severe damage to the brain. 
2. Stress is one of the leading and most unrecognized causes of a stroke.
3. Thrombolytics are drugs administered in case of a stroke in order to destroy the clot that prevents blood flow to the cortical structures. 
4. Nutrition rich in Vitamin D increases blood flow in the brain.
5. The carotid arteries consist of three layers: the outer layer (adventitia), the middle layer (media), and the deepest inside layer (intima). 
6. The bulb where the carotid arteries branch out is labeled as the carotid sinus. It contains receptors that control and regulate blood pressure. 
7. The Circle of Willis was discovered and analyzed by the English physician Thomas Willis (1621–1675).
8. The aorta is the largest blood supplying vessel in the body. The branches that stem from the aorta are labeled as arterioles.  
9. The brain cannot survive more than a few minutes without oxygen.
10. The diagnostic tests for a stroke include computed tomography (CT), magnetic resonance imaging (MRI), carotid ultrasound, echocardiogram, and other blood vessel imaging tests. These tests detect alterations in oxygen supply to the cortical structures and the health of the main blood supplying arteries.