Myasthenia Gravis Lesson Plan

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Introduction Some of the neurological disorders are very rare but if once happened becomes chaos. Now mega star of the millennium Mr. Amitabh Bacchan had suffered from a very rare disease in 1980s called as Myesthenia gravis. synonyms

MG Myasthenia Gravis Pseudoparalytica Erb-Goldflam syndrome

Review the anatomy and physiolog y.

Anatomy and physiology of brain The brain is divided into the cerebrum, diencephalons, brain stem, and cerebellum. Cerebrum The largest and most obvious portion of the brain is the cerebrum, which is divided by a deep longitudinal fissure into two cerebral hemispheres. The two hemispheres are two separate entities but are connected by an arching band of white fibers, called the corpus callosum that provides a communication pathway between the two Lecture cum discussion

halves. Each cerebral hemisphere is divided into five lobes, four of which have the same name as the bone over them: the fontal lobe, the parietal lobe, the occipital lobe, and the temporal lobe. A fifth lobe, the insula or Island of Reil, lies deep within the lateral sulcus.

Lecture cum discussion.

Diencephalon The diencephalons is centrally located and is nearly surrounded by the cerebral hemispheres. It includes the thalamus, hypothalamus, and epithalamus. The thalamus, about 80 percent of the diencephalons, consists of two oval masses of gray matter that serve as relay stations for sensory impulses, except for

the sense of smell, going to the cerebral cortex. The hypothalamus is a small region below the thalamus, which plays a key role in maintaining homeostasis because it regulates many visceral activities.

Brain Stem The brain stem is the region between the diencephalons and the spinal cord. It consists of three parts: midbrain, pons, and medulla oblongata. The midbrain is the most superior portion of the brain stem. The pons is the bulging middle portion of the brain stem. This region primarily consists of nerve fibers that form conduction tracts between the higher brain centers and spinal cord. The medulla oblongata, or simply medulla, extends inferiorly from the pons. It is continuous with the spinal cord at the foramen magnum. All the ascending (sensory) and descending (motor) nerve fibers connecting the brain and spinal cord pass through the medulla. Cerebellum The cerebellum, the second largest portion of the brain, is located below the occipital lobes of the cerebrum. Three paired bundles of myelinated nerve fibers, called cerebellar peduncles, form communication pathways between the cerebellum and other parts of

the central nervous system. Ventricles and Cerebrospinal Fluid A series of interconnected, fluid-filled cavities are found within the brain. These cavities are the ventricles of the brain, and the fluid is cerebrospinal fluid (CSF). Spinal Cord The spinal cord extends from the foramen magnum at the base of the skull to the level of the first lumbar vertebra. The cord is continuous with the medulla oblongata at the foramen magnum. Like the brain, the spinal cord is surrounded by bone, meninges, and cerebrospinal fluid. The spinal cord has two main functions:

Lecture cum discussion

Define the key terms.

Serving as a conduction pathway for impulses going to and from the brain. Sensory impulses travel to the brain on ascending tracts in the cord. Motor impulses travel on descending tracts. Serving as a reflex center. The reflex arc is the functional unit of the nervous system. Reflexes are responses to stimuli that do not require conscious thought and consequently, they occur more quickly than reactions that require thought processes.

To discuss the incidence rate.

Definition Myasthenia gravis (MG) is a chronic disease characterised by fluctuating levels of muscle weakness. Lecture cum discussion

Incidence It is uncommon, affecting only 15 per 100,000 individuals, and although it can be a very serious condition, 90 per cent of patients live a near-normal life while continuing medical treatment. Classification The most widely accepted classification of myasthenia gravis is the Myasthenia Gravis Foundation of America Clinical Classification:

Class I: Any eye muscle weakness, possible ptosis, no other evidence of muscle weakness elsewhere Class II: Eye muscle weakness of any severity, mild weakness of other muscleso o

Class IIa: Predominantly limb or axial muscles Class IIb: Predominantly bulbar and/or respiratory muscles

Class III: Eye muscle weakness of any severity, moderate weakness of other muscleso

Class IIIa: Predominantly limb or axial muscles

o

Class IIIb: Predominantly bulbar and/or respiratory muscles

List the causes.

Class IV: Eye muscle weakness of any severity, severe weakness of other muscleso o

Class IVa: Predominantly limb or axial muscles Class IVb: Predominantly bulbar and/or respiratory muscles (Can also include feeding tube without intubation)

Class V: Intubation needed to maintain airway

Explain the pathophys iology .

Causes and risk factors it is an autoimmune disorder, in which weakness is caused by circulating antibodies that block acetylcholine receptors at the postsynaptic neuromuscular junction,[1] inhibiting the excitatory effects of the neurotransmitter acetylcholine on nicotinic receptors throughout neuromuscular junctions. Myasthenia is treated medically with cholinesterase inhibitors or immunosuppressants, and, in selected cases, thymectomy.

Pathophysiology MG is the result of a selective overactivity of the body's immune system in which patients produce antibodies against

Enumerate the signs and symptoms .

a particular target in their own body. Antibodies are the specialised types of protein made by the immune system in response, normally, to intrusion of a foreign body such as a virus. In MG however the protein being attacked is a normal component of the body, which is therefore being attacked by its own immune system. This is what is termed an 'autoimmune disease'. The target is a protein called the acetylcholine receptor (AChR), which is found at the junction between the nerve and the muscle (the neuromuscular junction) In order for a nerve impulse to reach a muscle fibre and cause the muscle to contract, a minute packet of a signalling chemical, acetylcholine, must be released from the end of the nerve and cross the gap to the muscle membrane. Here the acetylcholine molecule fits in to the receptor of the muscle like a key fits in a lock, and the signal is passed: a process known as neuromuscluar transmission. Under normal circumstances this process works very efficiently, but in MG, antibodies against the AChR reduce the efficiency of neuromuscular transmission, and as a result the person experiences muscle weakness particularly when they repeatedly try to use the same muscle. Although we now understand how antibodies to the AChR cause muscle weakness, we do not know why patients with MG develop these autoantibodies. Very rarely an individual can be born with a genetic

abnormality that causes a disorder that resembles MG (congenital myasthenia).

Signs and symptoms Muscle weakness caused by myasthenia gravis worsens as the affected muscle is used repeatedly. Since symptoms typically improve with rest. However, the symptoms of myasthenia gravis tend to progress over time, usually reaching their worst within a few years after the onset of the disease. Although myasthenia gravis can affect any of the muscles that you control voluntarily, certain muscle groups are more commonly affected than others. Eye muscles In more than half the people who develop myasthenia gravis, their first signs and symptoms involve eye problems, such as: Drooping of one or both eyelids (ptosis) Double vision (diplopia), which may be horizontal or vertical Face and throat muscles In about 15 percent of people with myasthenia gravis, the first symptoms involve face and throat muscles, which can cause difficulties with: Altered speaking. Your speech may be very soft or may sound nasal, depending upon which muscles have been affected. Difficulty swallowing. You may choke very easily, which makes it difficult to eat, drink or take pills. In some cases, liquids you're trying to swallow may come out your nose.

Lecture cum discussion

Discuss the diagnostic evaluation

Problems chewing. The muscles used for chewing may wear out halfway through a meal, particularly if you've been eating something hard to chew, such as steak. Limited facial expressions. Family members may note that you've "lost your smile" if the muscles that control your facial expressions are affected. Neck and limb muscles Myasthenia gravis can cause weakness in your neck, arms and legs, but this usually happens in conjunction with muscle weakness in other parts of your body such as your eyes, face or throat. The disorder usually affects arms more often than legs. However, if it affects your legs, you may waddle when you walk. If your neck is weak, it may be hard to hold your head erect. Factors that can worsen myasthenia gravis Fatigue Illness Stress Extreme heat Some medications such as beta blockers, calcium channel blockers, quinine and some antibiotics Diagnostic evaluation Patient History. Physical especially Neurologic examination,

Lecture cum discussion

Tests and diagnosis The key sign that points to the possibility of myasthenia gravis is muscle weakness that improves with rest. Tests to help confirm the diagnosis may include: Edrophonium test Injection of the chemical edrophonium (Tensilon) may result in a sudden, although temporary, improvement in your muscle strength an indic