Responses
Choice #2 Genetic Components, Pathophysiology, and Major Neurologic Features
Neurofibromatosis (NF) is an autosomal dominant genetic disorder that has variable expressivity, which means that the patient can have signs and symptoms that can vary. Common symptoms include multiple caf-au-lait spots, neurofibromas, learning disabilities, and seizure disorders. Caf-au-spots are hyperpigmented lesions that vary in color from light brown to dark brown (Saedi, 2021).
According to McCance and Huether (2014), Cri du chat syndrome is an autosomal dominant genetic disorder with a deletion on the short arm of chromosome 5. What occurs in this genetic disorder is there is a deletion of multiple genes responsible for the phenotype. Additionally, there is evidence that there is a deletion of the telomerase reverse transcriptase gene. The size of the deletion varies among affected individuals. Studies show that larger deletions indicate more severe intellectual disability and developmental delay (Cri-Du-Chat Syndrome, 2020). Common symptoms that occur include a high-pitched cry, mental retardation, microcephaly, low birth weight, failure to thrive, widely spaced eyes, and unusually small jaw. This genetic disorder is also known as 5p minus.
Tay-sacs disease is an autosomal recessive genetic disorder with a mutation of the HEXA gene, which is chromosome 15. This is caused by a deficiency of hexosaminidase, which is an enzyme that will result in the accumulation of a material that damages the brain. The HEXA gene makes beta-hexosaminidase A, which plays a critical role in the brain and spine. Mutations in the HEXA gene interfere with the activity of beta-hexosaminidase A. This prevents the enzyme from breaking down GM2 ganglioside, which results in toxic levels that damages the neurons in the brain and spinal cord. This leads to the symptoms of Tay-sachs disease (Tay-Sachs Disease, 2020). Infants appear normal until the age of 3 to 6 months. Infants will lose motor skills such as rolling over and crawling. Common symptoms include failure to thrive, blindness, seizures, progressive paralysis, and death by age 4 (Woo & Robinson, 2014).
Parkinsons disease is an autosomal dominant genetic disorder. It is the second most common neurodegenerative disease (Liu et al., 2021). According to Woo and Robinson (2014), Parkinsons disease is a complex motor disorder with systemic nonmotor and neurologic symptoms. What occurs is a degeneration of basal ganglia that involves the dopaminergic nigrostriatal pathway, which produces the syndrome of abnormal movement. The pathophysiology of primary Parkinsons disease is unknown. Several genes have been identified but the hallmark pathologic features include loss of a dopaminergic pigmented neurons in the substantia nigra pars compacta with dopaminergic deficiency in the putamen portion of the stratum. There is also dopamine loss in the brainstem, thalamus, and cortex, and degeneration of the nigrostriatal pathway to the basal ganglia, which results in underactivity of the direct motor pathway and overactivity of the indirect motor loop.
A modified Hoehn and Yahr scale can be used to assess the progression of Parkinsons disease:
* 0 No visible disease
* 1 Unilateral involvement, may have a tremor of one limb
* 2 Bilateral involvement, balance intact
* 3 Bilateral involvement, slowing of body movement, mild to moderate postural instability, and gait difficulty
* 4 Bilateral involvement with severe postural instability, rigidity, and bradykinesia present
* 5 Bilateral involvement with an inability to walk, confinement to a wheelchair, cachexia present
In the early stages of Parkinsons disease, reflex, sensory, and mental status are usually normal. However, some symptoms are present in the early stages and include hyposmia, fatigue, pain, autonomic dysfunction, sleep fragmentation, depression, and dementia with or without psychosis. Parkinsonian tremor is usually one of the first symptoms in the early stages. Parkinsonian rigidity is when there is increased resistance to passive movements. The first symptoms regarding this symptom are painful muscle cramps in the toes and hands. Parkinsonian bradykinesia is a slow movement that occurs. Hypokinesia is the decreased frequency of movements, which is one of the earliest symptoms. Parkinsons disease can have symptoms of sleep disorders. About 90 percent of patients experience some sort of sleep disorder (Liu et al., 2021). All in all, Parkinsons disease occurs after 40 years of age, with a mean onset of 60 years of age. About 60,000 people are diagnosed each year in the United States. There is a 10 percent portion of the Parkinsons disease population that is familial, and the remaining are idiopathic (Woo & Robinson, 2014).
Choice #1, Spinal Cord Injury and Schwann Cells
Generally speaking, the spinal cord transmits information between the brain and the rest of the body. When it sustains damage, the nerve bundles that carry information stops working, leading to debilitating symptoms (Bates, 2015). There are approximately 273,000 cases of spinal cord injuries (SCI) in the United States, with 12,000 new cases annually (McCance & Huether, 2014). The authors further noted that the causes are attributed mostly to vehicular accidents, falls, violence, and sports. Acute and long term secondary medical complications are common in patients with SCI, not only causing functional sequelae, but also psychological and socioeconomic concerns (Sezer, Akku, & Uurlu, 2015). The goal for people affected with SCI are rehabilitation and treatment approaches that improve functional level, decrease secondary morbidity, and enhance quality of life (Sezer, Akku, & Uurlu, 2015).
Complication associated with SCI include respiratory complications, which are the most important causes of morbidity and mortality (Sezer, Akku, & Uurlu, 2015). The extent of complications depends on the level of injury and degree of impairment. Respiratory dysfunction seen are insufficiency of respiratory muscles, reduced vital capacity, ineffective cough, as well as reduction in lung and chest wall compliance (Sezer, Akku, & Uurlu, 2015). These circumstances lead to atelectasis, pneumonia, and respiratory failure (Sezer, Akku, & Uurlu, 2015). Cardiovascular complications are also apparent such that SCI can cause orthostatic hypotension due to low level of efferent sympathetic nervous activity and loss of reflex vasoconstriction, autonomic dysreflexia, reduced transmission of cardiac pain, impaired cardiovascular reflexes, and cardiac atrophy due to loss of cardiac mass (Sezer, Akku, & Uurlu, 2015). Additionally, Sezer, Akku, & Uurlu (2015) mentioned that there is also a loss in GI and GU functions following SCI such that patients suffer neurogenic bowel and bladder, as well as loss of muscular control presenting as spasticity which causes considerable impairment by contributing to functional impairment such as contractures, ulcers, posture disorders and pain (Sezer, Akku, & Uurlu, 2015). Chronic pain syndromes are also frequent following SCI as a result of damage to the nerve roots or the spinal cord itself and also due to musculoskeletal pain resulting from abnormal posture. Lastly, pressure ulcers are a very common secondary complication which can lead to further disability because of concerns of infection that may need medical and surgical interventions (Sezer, Akku, & Uurlu, 2015). SCIs are a chronic in nature because of the secondary complications that arise. This leads to functional disability, emotional and psychosocial distress, as well as economic burden both short term and long term because of hospitalizations, re-hospitalizations, therapies, medical equipment, and medication. Therefore, it is important to be aware of complications that may arise during the rehabilitative process and to be proactive with treatment plans.
On another note, since there is currently no definitive treatment for SCI, the focus of the neuroscience community is the repair of damaged spinal cord in hopes of regenerating function (Bates, 2015). The strategy that is being considered currently is the use of Schwann cells. According to Bates (2015), these cells have been found to support peripheral nerve fibers after an insult. She further adds that they work by proliferating to the area of insult and secrete growth factors to help repair the damaged axons of the peripheral nerves. Additionally, they also produce myelin, which insulates axons and subsequently helps speed up transmission of nerve signals (Bates, 2015). However, when an insult is sustained by the central nervous system, the opposite happens where chemicals that block axon growth is what floods the site of injury (Bates, 2015). So, a neuroscientist has considered adding the Schwann cells and growth factors to the injury and beyond in hopes that the axons start repairing, regenerating, and reconnecting all the way to the brain, and so far, this has been promising (Bates, 2015). With the current strategies actively being pursued by the neuroscience community, there is hope that new treatment interventions will prove useful in the rehabilitation and treatment of central nervous system disorders caused by spinal injuries.
