NR 507 Week 8 Assignment; CNS; Brain Disorders (E-dapt Content)

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Matthew Perry

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Nursing

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NR 507 Advanced Pathophysiology

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Chamberlain

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21

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CNS: Brain Disorders Convulsions Epilepsy is a disorder that is due to one or more chronic conditions in the body. It is characterized by disturbed nerve cell activity in the brain. This leads to recurrent seizures. Seizures may occur due to brain trauma that leads to disturbed and uncontrolled nerve activity in the brain. It is important to differentiate between epilepsy and seizure. 4296409582543Seizure is a condition that occurs due to excessive and uncontrolled neuronal activity in the brain. The uncontrolled neuron activity can be generalized or localized to one area of the brain. For example, it can be localized just to the area that perceives the touch sensation. Whether it is generalized or localized, the excessive neuronal activity lead to the seizure. The type of seizure will depend on the area of the brain affected. Mechanisms of Seizure Development 273050633342Normally there exists a balance between the excitation and inhibition of neurons in the CNS. Neuronal activity is regulated by acetylcholine (ACH) and gamma-Aminobutyric acid (GABA). Neurons are synchronously active at the same time when they are not supposed to be. The term active denotes neuron firing where they are sending electrical signals from neuron to neuron. A microscope view of a neuron will demonstrate that each electrical signal that passes through it are just ions floating in and out through protein channels (see diagram below). The ion flow is controlled through neurotransmitters. Neurotransmitters bind to the receptors to tell the cell to either open the ion channels to relay the chemical message (excitatory neurotransmitters) or close the ion channels to inhibit the electrical message (inhibitory neurotransmitters). Phases of Seizures During a seizure, clusters of neurons in the brain become temporarily impaired. Seizures develop in a group of neurons when there is hyperexcitability and usually happens in two phases: Initiation phase: Some neurons become hyperexcited and start to have excess neuron discharges. One of the most important reasons relates to the body’s sodium level as in the case of hyponatremia. Propagation phase: Normally the neurons that have neuronal discharges are surround by a zone of inhibitory neurons called the zone of hyperpolarization. This zone prevents the spread of excessive neuron discharges to other parts of the brain. But due to some abnormality in the brain, as in the case of decreased sodium levels, the zone of hyperpolarization gets depolarized that allows the spread of neurons to other parts of the brain. In the diagram to the left, the electrical activity in the normal brain is displayed. Seizures can be partial or generalized in terms of the extent of the neuronal discharges. In a partial seizure, a portion of the brain is involved. During a generalized seizure, the neuronal discharge encompasses the entire cerebral cortex. Etiology of Seizures To remember seizure etiology, use the acronym Vitamins D: Types and Classifications of Seizures Generalized seizures: Generalized seizures usually start at one place in the brain and due to widespread neuronal networks, they spread through that whole cerebral cortex. The main characteristic of a generalized seizure is that there is spread of the seizure. One of the major structures that helps in the spread is the corpus callosum. It connects the right and left-brain hemispheres and because of this the seizure spreads to the other hemisphere of the brain. Below are the different types of generalized seizures. Match each type to their proper characteristics. Generalized tonic-clonic seizures: there is wide-spread and uncontrolled neuron activity in the entire cerebral cortex. These occur in 10% of patients who have epilepsy. There is excessive neuronal discharge in the motor nerves through the brain. Tonic-clonic phase (lasts 10-20 seconds): Due to the excessive discharge of neurons in the motor nerves that results in: the muscles of the body become contracted. without any relaxation. loss of consciousness. ictal cry. This is a typical sound produced by the tonic contractions of the laryngeal muscles and muscles of expiration. respiratory impairment that results in cyanosis. tonic contraction of the jaw muscles that can cause tongue biting. Increased sympathetic activity. This will cause increased heart rate and blood pressure Clonic phase (lasts one minute): continuous discharge of neurons gets interrupted. It is characterized by small durations of relaxation. This occur because of inhibitory mechanisms of the brain to try to control the wide-spread neuronal activity. The patient will exhibit spasms and jerking. This is perceived as violent shaking of muscles. Post-ictal phase (lasts one to two hours): this stage is characterized by confusion, unresponsiveness and muscle flaccidity. Following the post-ictal state, there will be a return to normal state of consciousness. Generalized tonic seizures: this seizure is characterized by unconsciousness and muscle rigidity. Generalized clonic seizures: this seizure is characterized by muscle spasms. Generalized absence seizure: this seizure is most common in children. It is caused by a genetic abnormality. They are characterized by sudden and brief loss of consciousness without muscle tone and last for only a few seconds. There is no associated post-ictal confusion. Post-Seizure Symptoms Post-ictal confusion. Paralysis that affects the arms and legs that is usually limited to one side of the body (Todd’s paralysis or paresis). It can last on average 15 hours and subsides completely by itself within two days. The exact mechanism behind Todd’s paralysis is not well-known but may be due to temporary but severe suppression of activity of the area of the brain affected by the seizure. Overall, in generalized seizures, it involves both hemispheres of the brain where the patient will lose consciousness briefly or over a long period of time. If the seizures do last for a long period of time (> 5 minutes with ongoing seizure) or the individual has multiple seizures without returning to normal in between, this is called status epilepticus. It is characterized by a clonic-tonic type sub-seizure. It can also be caused by other types that don’t involve convulsions. This situation is considered a medical emergency and can be life threatening if it is not treated immediately. Due to the variability of the seizures, the patient will be treated with benzodiazepines. They help to enhance the effect of the neurotransmitter GABA. Focal Seizures In focal seizures, the seizure is confined to one area of the brain. It usually involves just one hemisphere or one small part of a hemisphere. The symptoms are dependent upon the area of the brain affected as well as the spread of the seizure. If the focal seizure is confined to the motor area of the brain, the symptoms produced are the muscle jerking in one area. Some patients also exhibit turning of the head to one side. If the focal seizure occurs in the vision part of the brain, the symptoms are usually flashings of light which are only perceived by the patient. If the focal seizures occur in the auditory cortex, the patient will perceive a ringing sound in the ear. If it occurs in the sensory area of the brain, it is perceived as false touch sensations. Types of Focal Seizures Focal seizures without dyscognitive features: there is no impairment of consciousness. The patient remains conscious during the seizure and able to interact normally with the surroundings. These were previously classified as simple partial seizures. Focal seizures with dyscognitive features: there are marked impairment of consciousness without loss of consciousness. The patient appears to be awake but does not interact or answer questions. These were previously classified as complex-partial seizures. Seizure Diagnosis and Treatment Diagnosis Following a seizure, individuals will undergo diagnostic testing for evaluation of the seizure: Brain imaging: MRI. CT scan. EEG-to detect electrical activity in the brain. For new onset seizures brain scans are used to determine if there are any anatomical abnormalities (tumors or abnormal blood vessels). Surgery is indicated for tumor or blood vessel abnormalities. Because epilepsy can vary among patients in terms of severity and frequency, diagnosis involves several tests combined with a thorough analysis of the history and physical exam findings. After diagnosis, pharmacological management is included in the treatment plan. Treatment Anticonvulsants: A wide variety of options are available that target different areas of the brain. The choice of anticonvulsant is based on the specific needs of the patient (age, lifestyle, other health conditions, and the category or sub-category of seizure type). Surgery: Remove the cause of the seizure (tumor). Nerve stimulation: Certain nerves (vagus nerve) is stimulated to control the seizure by influencing neurotransmitter release. Ketogenic diet: Will force the body to burn fat instead of carbohydrates which will produce ketone bodies that is then used by the brain as an energy source instead of glucose. There are many thoughts on how this works to reduce seizures in some patients, the exact mechanism is unknown. Febrile Seizures These are seizures that happen during a fever. It is most common in children ages 6 months to 5 years. Neurons are the main cells of the nervous system and are composed of a cell body (contains organelles) and nerve fibers which are projections that extend from the cell body. Types of nerve fibers include dendrites (receives signals from other neurons or axons (sends signals in form of action potentials) along to other neurons. The synapse is where two nerves come together. This is where one end of an axon sends neurotransmitters to the dendrites or directly to a cell body. The diagram below depicts the anatomy of a nerve cell: 723862-1096As we have discussed in previous sections, some neurotransmitters bind to receptors to stimulate it to open the ion channels and relay the electrical message. These are known as excitatory neurotransmitters. There are others that close the channel that prevent the electrical message from going through. These are called inhibitory neurotransmitters. The main excitatory neurotransmitter in the brain is glutamate. Glutamate binds to NMDA receptors that tell the cell to open calcium ion channels. Since calcium has a positive electrical charge, it causes the inside of the cell to become more positive which triggers an action potential. The main inhibitory neurotransmitter in the brain is GABA. It binds to GABA receptors which commands the cell to open chloride ion channels. Since chloride has a negative charge, it makes the inside of the cell more negative. This inhibits the action potential. During a seizure, large groups of neurons become active in a synchronous way all at the same time. In a febrile seizure the fever is a trigger for the seizure. The reason for this process is unknown. Some of the possible reasons includes: The fever raises the core body temperature which makes neurons more excitable. Action potentials are more likely to occur. Fever causes hyperventilation. Increased respirations decrease the level of CO2 in the blood that leads to respiratory alkalosis with increase in blood pH that seems to excite the neurons. Fevers are caused by cytokines (interleukin 1beta (IL-1B) that are released by white

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