Stroke
Stroke is the clinical designation for a rapidly developing loss of brain function due to an interruption in the blood supply to all or part of the brain. This phenomenon can be caused by thrombosis, embolism, or hemorrhage.
Stroke is a medical emergency and can cause permanent neurologic damage or even death if not promptly diagnosed and treated. It is the third leading cause of death and the leading cause of adult disability in the United States and industrialized European nations. On average, a stroke occurs every 45 seconds and someone dies from a stroke every 3 minutes.
The symptoms of stroke can be quite heterogeneous, and patients with the same cause of stroke can have widely differing handicaps. Conversely, patients with the same clinical handicap can in fact have different underlying causes.
The cause of stroke is an interruption in the blood supply, with a resulting depletion of oxygen and glucose in the affected area. This immediately reduces or abolishes neuronal function, and also initiates an ischemic cascade which causes neurons to die or be seriously damaged, further impairing brain function.
Risk factors for stroke include advanced age,hypertension (high blood pressure), diabetes mellitus, high cholesterol, cigarette smoking, atrial fibrillation, migraine with aura, and thrombophilia. Cigarette smoking is the most important modifiable risk factor of stroke.
In recognition of improved methods for the treatment of stroke, the term “brain attack” is being promoted in the United States as a substitute for stroke. The new term makes an analogy with “heart attack” (myocardial infarction), because in both conditions, an interruption of blood supply causes death of tissue which is life-threatening. Many hospitals have “brain attack” teams within their neurology departments specifically for swift treatment of stroke.
Types of stroke:
Strokes can be classified into two major categories: ischemic and hemorrhagic. Ischemia can be due to thrombosis, embolism, or systemic hypoperfusion. Hemorrhage can be due to intracerebral hemorrhage, subarachnoid hemorrhage subdural hemorrhageand epidural hemorrhage. ~80% of strokes are due to ischemia.
Ischemic stroke
In an ischemic stroke, which is the cause of approximately 80% of strokes, a blood vessel becomes occluded and the blood supply to part of the brain is totally or partially blocked. Ischemic stroke is commonly divided into thrombotic stroke, embolic stroke, systemic hypoperfusion (Watershed or Border Zone stroke), or venous thrombosis. Cocaine abuse doubles the risk of ischemic strokes.
Thrombotic stroke
In thrombotic stroke, a thrombus-forming process develops in the affected artery. The thrombus – a built up clot – gradually narrows the lumen of the artery and impedes blood flow to distal tissue. These clots usually form around atherosclerotic plaques. Since blockage of the artery is gradual, onset of symptomatic thrombotic strokes is slower. A thrombus itself (even if non-occluding) can lead to an embolic stroke (see below) if the thrombus breaks off-at which point it is then called an “embolus.” Thrombotic stroke can be divided into two types depending on the type of vessel the thrombus is formed on: Large vessel disease involves the common and internal carotids, vertebral, and the Circle of Willis. Diseases that may form thrombi in the large vessels include (in descending incidence):
- Atherosclerosis
- Vasoconstriction
- Dissection
- Takayasu arteritis
- Giant cell arteritis
- Arteritis/vasculitis
- Noninflammatory vasculopathy
- Moyamoya syndrome
- Fibromuscular dysplasia
Embolic stroke
Embolic stroke refers to the blockage of arterial access to a part of the brain by an embolus-a traveling particle or debris in the arterial bloodstream originating from elsewhere. An embolus is most frequently a blood clot, but it can also be a plaque broken off from an atherosclerotic blood vessel or a number of other substances including fat (e.g., from bone marrow in a broken bone), air, and even cancerous cells. Another cause is bacterial emboli released in infectious endocarditis.
Because an embolus arises from elsewhere, local therapy only solves the problem temporarily. Thus, the source of the embolus must be identified. Because the embolic blockage is sudden in onset, symptoms usually are maximal at start. Also, symptoms may be transient as the embolus lyses and moves to a different location or dissipates altogether. Embolic stroke can be divided into four categories:
- those with known cardiac source
- those with potential cardiac or aortic source (from transthoracic or
transesophageal echocardiogram) - those with an arterial source
- those with unknown source
High risk cardiac causes include:
- Atrial fibrillation and paroxysmal atrial fibrillation
- Rheumatic mitral or aortic valve disease
- Bioprosthetic and mechanical heart valves
- Atrial or ventricular thrombus
- Sick sinus syndrome
- Sustained atrial flutter
- Recent myocardial infarction (within one month)
- Chronic myocardial infarction together with ejection fraction
- Symptomatic congestive heart failure with ejection fraction
- Dilated cardiomyopathy
- Libman-Sacks endocarditis
- Antiphospholipid syndrome
- Marantic endocarditis from cancer
- Infective endocarditis
- Papillary fibroelastoma
- Left atrial myxoma
- Coronary artery bypass graft (CABG) surgery
Potential cardiac causes include:
- Mitral annular calcification
- Patent foramen ovale
- Atrial septal aneurysm
- Atrial septal aneurysm with patent foramen ovale
- Left ventricular aneurysm without thrombus
- Isolated left atrial smoke on echocardiography (no mitral stenosis or atrial fibrillation)
- Complex atheroma in the ascending aorta or proximal arch
Hemorrhagic stroke
A hemorrhagic stroke, or cerebral hemorrhage, is a form of stroke that occurs when a blood vessel in the brain ruptures or bleeds. Like ischemic strokes, hemorrhagic strokes interrupt the brain’s blood supply because the bleeding vessel can no longer carry the blood to its target tissue. In addition, blood irritates brain tissue, disrupting the delicate chemical balance, and, if the bleeding continues, it can cause increased intracranial pressure which physically impinges on brain tissue and restricts blood flow into the brain. In this respect, hemorrhagic strokes are more dangerous than their more common counterpart, ischemic strokes. There are two types of hemorrhagic stroke: intracerebral hemorrhage, and subarachnoid hemorrhage. Amphetamine abuse quintuples, and cocaine abuse doubles, the risk of hemorrhagic strokes.
Subarachnoid hemorrhage
Subarachnoid hemorrhage (SAH) is bleeding into the cerebrospinal fluid (CSF) of the subarachnoid space surrounding the brain. The two most common causes of SAH are rupture of aneurysms from the base of the brain and bleeding from vascular malformations near the pial surface. Bleeding into the CSF from a ruptured aneurysm occurs very quickly, causing rapidly increased intracranial pressure. The bleeding usually only lasts a few seconds but rebleeding is common. Death or deep coma ensues if the bleeding continues. Hemorrhage from other sources is less abrupt and may continue for a longer period of time. SAH has a 40% mortality over 30 day period.
The symptoms of SAH occur abruptly due to the sudden onset of increased intracranial pressure. Often, patients complain of a sudden, extremely severe and widespread headache. The pain may or may not radiate down into neck and legs. Vomiting may occur soon after the onset of headache. Usually the neurologic exam is nonfocal-meaning no deficits can be identified that attributes to certain areas of the brain-unless the bleeding also occurs into the brain. The combination of headache and vomiting is uncommon in ischemic stroke.
Ischemic stroke
As ischemic stroke is due to a thrombus (blood clot) occluding a cerebral artery, a patient is given antiplatelet medication (aspirin, clopidogrel, dipyridamole), or anticoagulant medication (warfarin), dependent on the cause, when this type of stroke has been found. Hemorrhagic stroke must be ruled out with medical imaging, since this therapy would be harmful to patients with that type of stroke.
Motor Skill
A motor skill is a skill that requires an organism to utilize their skeletal muscles effectively. Motor skills and motor control depend upon the proper functioning of the brain, skeleton, joints, and nervous system. Most motor skills are learned in early childhood, although disabilities can affect motor skills development. Motor development is the development of action and coordination of one’s limbs, as well as the development of strength, posture control, balance, and perceptual skills.
Motor skills are divided into two parts:
- Gross motor skills include lifting one’s head, rolling over, sitting up, balancing, crawling, and walking. Gross motor development usually follows a pattern. Generally large muscles develop before smaller ones. Thus, gross motor development is the foundation for developing skills in other areas (such as fine motor skills). Development also generally moves from top to bottom. The first thing a baby usually learns is to control its head.
- Fine motor skills include the ability to manipulate small objects, transfer objects from hand to hand, and various hand-eye coordination tasks. Fine motor skills may involve the use of very precise motor movement in order to achieve an especially delicate task. Some examples of fine motor skills are using the pincer grasp (thumb and forefinger) to pick up small objects, cutting, coloring and writing, and threading beads. Fine motor development refers to the development of skills involving the smaller muscle groups.
Fine Motor Skills
Fine motor skills can be defined as coordination of small muscle movements which occur e.g., in the fingers, usually in coordination with the eyes. In application to motor skills of hands (and fingers) the term dexterity is commonly used.
The abilities which involve the use of hands, develop over time, starting with primitive gestures such as grabbing at objects to more precise activities that involve precise hand-eye coordination. Fine motor skills are skills that involve a refined use of the small muscles controlling the hand, fingers, and thumb. The development of these skills allows one to be able to complete tasks such as writing, drawing, and buttoning.
During the infant and toddler years, children develop basic grasping and manipulation skills, which are refined during the preschool years. The preschooler becomes quite adept in self-help, construction, holding grips, and bimanual control tasks requiring the use of both hands.
Motor Learning
Motor learning is the process of improving the motor skills, the smoothness and accuracy of movements. It is obviously necessary for complicated movements such as speaking, playing the piano and climbing trees, but it is also important for calibrating simple movements like reflexes, as parameters of the body and environment change over time. The cerebellum and basal ganglia are critical for motor learning.
As a result of the universal need for properly calibrated movement, it is not surprising that the cerebellum and basal ganglia are widely conserved across vertebrates from fish to humans.
Although motor learning is capable of achieving very skilled behavior, much has been learned from studies of simple behaviors. These behaviors include eyeblink conditioning, motor learning in the vestibulo-ocular reflex, and birdsong. Research on Aplysia californica, the sea slug, has yielded detailed knowledge of the cellular mechanisms of a simple form of learning.
An interesting type of motor learning occurs during operation of a brain- computer interface. For example, Mikhail Lebedev, Miguel Nicolelis and their colleagues recently demonstrated cortical plasticity that resulted in incorporation of an external actuator controlled through a brain-machine interface into the subject’s neural representation.
Parkinson’s disease
Parkinson’s disease (also known as Parkinson disease or PD) is a degenerative disorder of the central nervous system that often impairs the sufferer’s motor skills and speech.
Parkinson’s disease belongs to a group of conditions called movement disorders. It is characterized by muscle rigidity, tremor, a slowing of physical movement (bradykinesia) and, in extreme cases, a loss of physical movement (akinesia). The primary symptoms are the results of decreased stimulation of the motor cortex by the basal ganglia, normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level cognitive dysfunction and subtle language problems. PD is both chronic and progressive.
PD is the most common cause of Parkinsonism, a group of similar symptoms. PD is also called “primary parkinsonism” or “idiopathic PD” (“idiopathic” meaning of no known cause). While most forms of parkinsonism are idiopathic, there are some cases where the symptoms may result from toxicity, drugs, genetic mutation, head trauma, or other medical disorders.
Cerebral Palsy
CP is an umbrella term encompassing a group of non-progressive, non- contagious neurological disorders that cause physical disability in human development, specifically the human movement and posture.
The incidence in developed countries is approximately 2-2.5 per 1000 live births. Incidence has not declined over the last 60 years despite medical advances (such as electro-fetal monitoring) because these advances allow extremely low birth weight and premature babies to survive. Cerebral refers to the brain and palsy refers to disorder of movement. CP is caused by damage to the motor control centers of the young developing brain and can occur during pregnancy (about 75 percent), during childbirth (about 5 percent) or after birth (about 15 percent) up to about age three. Eighty percent of causes are unknown; for the small number where cause is known this can include infection, malnutrition, and/or head trauma in very early childhood. It is a non- progressive disorder; meaning the brain damage does not worsen, but secondary orthopedic deformities are common. There is no known cure for CP. Medical intervention is limited to the treatment and prevention of complications possible from CP’s consequences. Overall, CP ranks among the most costly congenital conditions in the world to manage effectively.
The central nervous system
The central nervous system (CNS) represents the largest part of the nervous system, including the brain and the spinal cord. Together with the peripheral nervous system, it has a fundamental role in the control of behavior. The CNS is contained within the dorsal cavity, with the brain within the cranial subcavity, and the spinal cord in the spinal cavity.
Since the strong theoretical influence of cybernetics in the fifties, the CNS is conceived as a system devoted to information processing, where an appropriate motor output is computed as a response to a sensory input. Yet, many threads of research suggest that motor activity exists well before the maturation of the sensory systems and then, that the senses only influence behavior without dictating it. This has brought the conception of the CNS as an autonomous system.
In the developing fetus, the CNS originates from the neural plate, a specialised region of the ectoderm, the most external of the three embryonic layers. During embryonic development, the neural plate folds and forms the neural tube. The internal cavity of the neural tube will give rise to the ventricular system. The regions of the neural tube will differentiate progressively into transversal systems. First, the whole neural tube will differentiate into its two major subdivisions: spinal cord (caudal) and brain (rostral/cephalic). Consecutively, the brain will differentiate into brainstem and prosencephalon. Later, the brainstem will subdivide into rhombencephalon and mesencephalon, and the prosencephalon into diencephalon and telencephalon.
the CNS is covered by the meninges, the brain is protected by the skull and the spinal cord by the vertebrae. The rhombencephalon gives rise to the pons, the cerebellum and the medulla oblongata, its cavity becomes the fourth ventricle. The mesencephalon gives rise to the tectum, pretectum, cerebral peduncle and its cavity develops into the mesencephalic duct or cerebral aqueduct. The diencephalon give rise to the subthalamus, hypothalamus, thalamus and epithalamus, its cavity to the third ventricle. Finally, the telencephalon gives rise to the striatum (caudate nucleus and putamen), the hippocampus and the neocortex, its cavity becomes the lateral (first and second) ventricles.
The basic pattern of the CNS is highly conserved throughout the different species of vertebrates and during evolution. The major trend that can be observed is towards a progressive telencephalisation: while in the reptilian brain that region is only an appendix to the large olfactory bulb, it represent most of the volume of the mammalian CNS. In the human brain, the telencephalon covers most of the diencephalon and the mesencephalon. Indeed, the allometric study of brain size among different species shows a striking continuity from rats to whales, and allows us to complete the knowledge about the evolution of the CNS obtained through cranial endocasts.
The Peripheral Nervous System
The peripheral nervous system, or PNS, is part of the nervous system, and consists of the nerves and neurons that reside or extend outside the central nervous system (the brain and spinal cord) to serve the limbs and organs, for example. Unlike the central nervous system, however, the PNS is not protected by bone or the blood-brain barrier, leaving it exposed to toxins and mechanical injuries. The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system.
Naming of specific nerves
The 10 out of the 12 cranial nerves originate from the brainstem, and mainly control the functions of the anatomic structures of the head with some exceptions. CN X (10) receives visceral sensory information from the thorax and abdomen, and CN XI (11) is responsible for innervating the sternocleidomastoid and trapezius muscles, neither of which is exclusively in the head. Spinal nerves take their origins from the spinal cord. They control the functions of the rest of the body. In humans, there are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumber, 5 sacral and 1 coccygeal. The naming convention for spinal nerves is to name it after the vertebra immediately above it. Thus the fourth thoracic nerve originates just below the fourth thoracic vertebra. This convention breaks down in the cervical spine. The first spinal nerve originates above the first cervical vertebra and is called C1. This continues down to the last cervical spinal nerve, C8. There are only 7 cervical vertebrae and 8 cervical spinal nerves.
Cervical spinal nerves (C1-C4)
The first 4 cervical spinal nerves, C1 through C4, split and recombine to produce a variety of nerves that subserve the neck and back of head. Spinal nerve C1 is called the suboccipital nerve which provides motor innervation to muscles at the base of the skull. C2 and C3 form many of the nerves of the the weirdly shaped heck neck, providing both sensory and motor control. These include the greater occipital nerve which provides sensation to the back of the head, the lesser occipital nerve which provides sensation to the area behind the ears, the greater auricular nerve and the lesser auricular nerve. See occipital neuralgia. The phrenic nerve arises from nerve roots C3, C4 and C5. It innervates the diaphragm, enabling breathing. If the spinal cord is transected above C3, then spontaneous breathing is not possible.
Brachial plexus (C5-T1)
The last 4 cervical spinal nerves, C5 through C8, and the first thoracic spinal nerve, T1,combine to form the brachial plexus, or plexus brachialis, a tangled array of nerves, splitting, combining and recombining, to form the nerves that subserve the arm and upper back. Although the brachial plexus may appear tangled, it is highly organized and predictable, with little variation between people.
Before forming three cords
The first nerve off the brachial plexus, or plexus brachialis, is the dorsal scapular nerve, arising from C5 nerve root, and innervating the rhomboids and the levator scapulae muscles. The long thoracic nerve arises from C5, C6 and C7 to innervate the serratus anterior. The brachial plexus first forms three trunks, the superior trunk, composed of the C5 and C6 nerve roots, the middle trunk, made of the C7 nerve root, and the inferior trunk, made of the C8 and T1 nerve roots. The suprascapular nerve is an early branch of the superior trunk. It innervates the suprascapular and infrascapular muscles, part of the rotator cuff. The trunks reshuffle as they traverse towards the arm into cords. There are three of them. The lateral cord is made up of fibers from the superior and middle trunk. The posterior cord is made up of fibers from all three trunks. The medial cord is composed of fibers solely from the medial trunk.
Lateral cord
The lateral cord gives rise to the following nerves:
- The lateral pectoral nerve, C5, C6 and C7 to the pectoralis major muscle, or musculus pectoralis major.
- The musculocutaneous nerve which innervates the biceps muscle
- The median nerve, partly. The other part comes from the medial cord. See below for details.
- The upper subscapular nerve, C7 and C8, to the subscapularis muscle, or musculus supca of the rotator cuff.
- The lower subscapular nerve, C5 and C6, to the teres major muscle, or the musculus teres major.
- The thoracodorsal nerve, C6, C7 and C8, to the latissimus dorsi muscle, or musculus latissimus dorsi.
- The axillary nerve, which supplies sensation to the shoulder and motor to the deltoid muscle or musculus deltoideus, and the teres minor muscle, or musculus teres minor, also of the rotator cuff.
- The radial nerve, or nervus radialis, which innervates the triceps brachii muscle, the brachioradialis muscle, or musculus brachioradialis,, the extensor muscles of the fingers and wrist (extensor carpi radialis muscle), and the extensor and abductor muscles of the thumb. See radial nerve injuries.
Medial cord
The medial cord gives rise to the following nerves:
- The median pectoral nerve, C8 and T1, to the pectoralis muscle
- The medial brachial cutaneous nerve, T1
- The medial antebrachial cutaneous nerve, C8 and T1
- The median nerve, partly. The other part comes from the lateral cord. C7, C8 and T1 nerve roots. The first branch of the median nerve is to the pronator teres muscle, then the flexor carpi radialis, the palmaris longus and the flexor digitorum superficialis. The median nerve provides sensation to the anterior palm, the anterior thumb, index finger and middle finger. It is the nerve compressed in carpal tunnel syndrome.
- The ulnar nerve originates in nerve roots C7, C8 and T1. It provides sensation to the ring and pinky fingers. It innervates the flexor carpi ulnaris muscle, the flexor digitorum profundus muscle to the ring and pinky fingers, and the intrinsic muscles of the hand (the interosseous muscle, the lumbrical muscles and the flexor pollicus brevis muscle). This nerve traverses a groove on the elbow called the cubital tunnel, also known as the funny bone. Striking the nerve at this point produces an unpleasant sensation in the ring and little fingers.
Spinal Cord Injury
Spinal cord injury, or myelopathy, is a disturbance of the spinal cord that results in loss of sensation and/or mobility. The two common types of spinal cord injury are:
- Trauma: automobile accidents, falls, gunshots, diving accidents, war injuries, etc.
- Disease: polio, spina bifida, tumors, Friedreich’s ataxia, etc.
Spinal cord injuries are not the same as back injuries such as ruptured disks, spinal stenosis or pinched nerves. It is possible to “break one’s neck or back” and not sustain a spinal cord injury if only the vertebrae are damaged and the spinal cord remains intact.
About 450,000 people in the United States live with spinal cord injury, and there are about 11,000 new spinal cord injuries every year. The majority of them (78%) involve males between the ages of 16-30 and result from motor vehicle accidents (42%), violence (24%), or falls (22%).
Head Injury
Head injury is a trauma to the head that may or may not include injury to the brain.
The incidence (number of new cases) of head injury is 300 per 100,000 per year (0.3% of the population), with a mortality of 25 per 100,000 in North America and 9 per 100,000 in Britain. Head trauma is a common cause of childhood hospitalization.
Causes
Common causes of head injury are traffic accidents, home and occupational accidents, falls, and assaults. Bicycle accidents are also a common cause of head injury-related death and disability, especially among children.
Types of head injury
Head injuries include both injuries to the brain and those to other parts of the head, such as the scalp and skull. Head injuries may be closed or open. A closed (non-missile) head injury is one in which the skull is not broken. A penetrating head injury occurs when an object pierces the skull and breaches the dura mater. Brain injuries may be diffuse, occurring over a wide area, or focal, located in a small, specific area.
A head injury may cause a skull fracture, which may or may not be associated with injury to the brain. Some patients may have linear or depressed skull fractures.
If intracranial hemorrhage, or bleeding within the brain occurs, a hematoma within the skull can put pressure on the brain. Types of intracranial hematoma include subdural, subarachnoid, extradural, and intraparenchymal hematoma. Craniotomy surgeries are used in these cases to lessen the pressure by draining off blood.
Brain injury can be at the site of impact, but can also be at the opposite side of the skull due to a contrecoup effect (the impact to the head can cause the brain to move within the skull, causing the brain to impact the interior of the skull opposite the head-impact). If the impact causes the head to move, the injury may be worsened, because the brain may ricochet inside the skull (causing additional impacts), or the brain may stay relatively still (due to inertia) but be hit by the moving skull.
Complex Regional Pain Syndrome
Complex Regional Pain Syndrome (CRPS) is a chronic condition characterized by severe pain following injury to bone and soft tissue. The International Association for the Study of Pain has divided CRPS into two types based on the presence of nerve lesion following the injury. Type I, also known as Reflex sympathetic dystrophy (RSD), Sudeck’s atrophy, Reflex neurovascular dystrophy (RND) or algoneurodystrophy, does not have demonstrable nerve lesions, while type II, also known as causalgia, has evidence of obvious nerve lesions. The cause of these syndromes is currently unknown. Precipitating factors include illness, injury.
Brachial Plexus
The brachial plexus is an arrangement of nerve fibres (a plexus) running from the spine (vertebrae C5-T1), through the neck, the axilla (armpit region), and into the arm.
The brachial plexus is responsible for cutaneous and muscular innervation of the entire upper limb, with two exceptions: the trapezius muscle innervated by the spinal accessory nerve and an area of skin near the axilla innervated by the intercostobrachialis nerve. Therefore, lesions of the plexus can lead to severe functional impairment.
Traumatic Brain Injury
Traumatic brain injury (TBI), traumatic injuries to the brain, also called intracranial injury, or simply head injury, occurs when a sudden trauma causes brain damage. TBI can result from a closed head injury or a penetrating head injury and is one of two subsets of acquired brain injury (ABI). The other subset is non-traumatic brain injury (i.e. stroke, meningitis, anoxia). Parts of the brain that can be damaged include the cerebral hemispheres, cerebellum, and brain stem (see brain damage). Symptoms of a TBI can be mild, moderate, or severe, depending on the extent of the damage to the brain. Outcome can be anything from complete recovery to permanent disability or death. A coma can also affect a child’s brain.
Multiple Sclerosis
Multiple Sclerosis (abbreviated MS, also known as disseminated sclerosis or encephalomyelitis disseminata) is a chronic, inflammatory, demyelinating disease that affects the central nervous system (CNS). MS can cause a variety of symptoms, including changes in sensation, visual problems, muscle weakness, depression, difficulties with coordination and speech, severe fatigue, cognitive impairment, problems with balance, overheating, and pain. MS will cause impaired mobility and disability in more severe cases.
Multiple sclerosis affects neurons, the cells of the brain and spinal cord that carry information, create thought and perception, and allow the brain to control the body. Surrounding and protecting some of these neurons is a fatty layer known as the myelin sheath, which helps neurons carry electrical signals. MS causes gradual destruction of myelin (demyelination) and transection of neuron axons in patches throughout the brain and spinal cord. The name multiple sclerosis refers to the multiple scars (or scleroses) on the myelin sheaths. This scarring causes symptoms which vary widely depending upon which signals are interrupted.
The predominant theory today is that MS results from attacks by an individual’s immune system on the nervous system and it is therefore usually categorized as an autoimmune disease. There is a minority view that MS is not an autoimmune disease, but rather a metabolically dependent neurodegenerative disease. Although much is known about how MS causes damage, its exact cause remains unknown.
Multiple sclerosis may take several different forms, with new symptoms occurring either in discrete attacks or slowly accruing over time. Between attacks, symptoms may resolve completely, but permanent neurologic problems often persist, especially as the disease advances. MS currently does not have a cure, though several treatments are available that may slow the appearance of new symptoms.
MS primarily affects adults, with an age of onset typically between 20 and 40 years, and is more common in women than in men.
Hypotonia
Hypotonia is a condition of abnormally low muscle tone (the amount of tension or resistance to movement in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases and disorders that affect motor nerve control by the brain or muscle strength. Recognizing hypotonia, even in early infancy, is usually relatively straightforward, but diagnosing the underlying cause can be difficult and often unsuccessful. The long-term effects of hypotonia on a child’s development and later life depend primarily on the severity of the muscle weakness and the nature of the cause. Some disorders have a specific treatment but the principal treatment for most hypotonia of idiopathic or neurologic cause is physical therapy to help the person compensate for the neuromuscular disability.
