Neurofibromatosis, a genetic disorder which can either be inherited or caused by a mutation is a rare type of disorder consisting of 2 types that can affect an individual. NF1 is known to typically affect the skin, creating various benign tumours and spreading to other parts of the body. NF2 on the other hand affects the central & peripheral nervous system affecting the body in various ways. NF also disrupts the cognitive ability of individuals and in particular the effect this has had on children. The physical evidence for this is supported by the study conducted which offered promising results and also highlights the severity of this impairment.
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Neurofibromatosis, a genetically inherited disorder is a condition which affects patients quite vigorously with symptoms appearing as early as childhood or in later stages of adulthood. Symptoms can vary between each patient as the nature & severity of the disorder actually depends on what type of NF the patient has either inherited or been affected by (mutation). NF can cause damage to many body organs including the skin, skull, brain, eyes, spinal cord and nervous tissue. One of the earliest signs of this disorder are the development of familial cafe au-lait spots, tumour forming on the optical nerve, plexiform neurofibromas and the development of tumours within the inner ear affecting the hearing & balance nerves. NF has also has affected their cognitive abilities and in particular children who are diagnosed suffer most from this as it creates learning disabilities and behavioural difficulties from an early age.
First note of this condition was made back in the 13th century as historical data dates back to this point in time however, it wasn’t until the 18th century when German Pathologist Friedrich Daniel Von Recklinghausen established his paper which detailed his findings on what he thought Neurofibromatosis was. Through his work science had made its first move in breaking down this genetic disorder and with further examination of it, it became known to the world. Although scientists of that era had distinguished neurofibromatosis as Recklinghausen’s disease (NF1) and Central Neurofibromatosis (NF2) as being two similar disorders, it only became apparent within the last decade that the two types of Neurofibromatosis occurred as two different autosomal inherited genetic disorders that possessed common symptoms that would affect the individual’s body.
NF1 is type of autosomal genetic disorder that possesses a skin affecting phenotype which induces benign tumours in various cell types within the body. Due to the rarity of this case occurring, it can be thought of as a sporadic affecting 1 in 3500 individuals. In recent years however through the advanced pathophysiological understanding of this disorder, various conditions have been linked to NF1 & NF2 for example, Neurofibromas forming on the peripheral nerves, lesions created on the skin where one patch of the skin may appear darker in colour and curvature of the spine (Scoliosis). NF2 on the other hand is of the rarer type and typically affects the Central nervous system and the peripheral nervous system damaging the surrounding tissue creating lesions which can cause a cascade of effects to the individual. Of these effects the most common symptom is the development of malignant tumours on the spinal cord, peripheral nerves and the anterior portion of the skull.
Currently there is no medical treatment underway which is able to cure Neurofibromatosis, although an NF patient will have gone through a series of surgeries and oral examinations that would allow the doctor to track the progression rate of the disease and advise the next steps that the patient can take. Neurofibromatosis can present further complications as the disease grows and spreads, reducing the success rate of a potential surgery that will be needed in the future to remove various tumours throughout the patient’s case.
The development of this disorder is an intricate process. The cause of this ever-growing genetic disorder is often a result from a mutation in germline cells, as a result this causes a deletion at the 17q11.2 locus which represents the location of the gene within the chromosome that is affected by this mutation. NF1 gene serves the purpose of coding a protein called Neurofibromin which is produced by many cells within the body however in terms of the pathogenesis, is a tumour supressing protein that works by negative regulation of mitogenic acting ras signalling through a GTPase activating protein (GAP). Mitogenesis is the occurrence of mitosis via the activation of a mitogen which enables a signal transduction pathway allowing the transmission of extracellular signals to within the intended cell type, GAP acts as a regulator of Ras guanosine triphosphatase activity (GTPase) and as such regulates incoming signals for cellular division and differentiation. Together this plays an essential role in associated NF1 type tumour genesis.
Figure 1: represents interactions of key proteins & Genes involved in NF1 pathogenesis
Similarly to NF1, this NF2 pertaining gene located on the 22q12.2 region codes for a protein called Schwannomin (Merlin) which also is a type of tumour suppressor. Schwannomin serves as a regulatory molecule which watches over the growth, motility and cellular remodelling of the cell through the inhibition of the transduction of extracellular mitogenic acting signals. In relation to the inhibiting effect shown by Schwannomin, it also prevents the epidermal growth factor receptor signalling which prevents further proliferation within cells.
Figure 2: represents 3D structure of NF2 coding protein, Merlin.
As a result of this deletion on the NF1 gene, this has lead to the stop in production of neurofibromin which in turn has been suggested to result in the lack of inhibitory control of Ras. Therefore affecting the regulation of cellular proliferation & differentiation. Another suggestion was made that the noticeable increase in movement and production of neurons may have been the cause to structural and functional brain abnormalities which are accossiated with cognitive impairment. One of the most common symptoms as a result of Neurofibromatosis, however lack of cognitve abilties only becomes more apparent when they are needed. Brain abnormalties has also been suggested to be the reason to many social and behavioral difficulties that the individual may suffer from.
In order for the individulal to respond to a range of situations, there must be good communication between many different regiouns of the brain, therefore lack of this can make it difficult for the child or adult to react. Many of the problems that are associated with social and behavioral difficulties often include having trouble interacting with peers, poor social skills & exhibiting behvaioral concerns. However in order to support this wih physical evidense, not many studies have actully been conducted either between NF1 and cognition or the social and behavioral functioning associated with it. Of one study that was conducted by (Descheemaeker et al 2005), a range of 17 NF1 patients were selected to participate in a study that used socio-behavioural & cognitive measures, however in results they had found no significant relationships between them both.
To gain physical evidence to support that NF1 patients in particular children are affected by cognitive problems, a study was conducted. A range of NF1 patients from children’s to adults were recruited through the Dutch Neurofibromatosis Association with participants as follows:
Figure 3: represents 30 patients from children to adults with NF1 (mean age 11.7, SD=3.3, Range=6.9-17.3 years)
Figure 4: represents 30 healthy patients from children to adults (mean age 12.5 years, SD = 3.1, range 6.0–17.3 years)
This entire procedure had been approved by the parents signing their consent that their child can be assessed in the diagnostic test which was going to be used, also being passed by the Leiden University’s Education and Child Studies Ethics Committee. A combination of 5 computerised tests were conducted at the Amsterdam Neuropsychological Tasks institute that assessed the speed of information processing, cognitive control, and social information processing of each participant. Each of the participants processing speed was accessed through the app called Baseline, with a pointer in the middle, participants were required to use the mouse and click on the pointer and the timings for when they had clicked it were recorded. A total of 32 trials had been taken with both hands. To test cognitive control, an app which requires participants to remember figures that can be distinguished by colour, shape was used. Each trial displayed 4 figures and in each figure, the individual was required to press yes if the target was correct and no if the target was incorrect. A total of 48 trials were recorded. The inhibitory control was measured by the Response Organisation Arrows task. On the screen an arrow would be shown and the colour of the arrow would determine the response the individual should give either with the right or left key, if the arrow should point to the right the right key is pressed, if the arrow points to the left then the left key should be pressed.
A table of results was constructed as shown below:
Table 1: Represents test scores obtained via computer measuring cognition, social & behavioral measures between 30 NF1 type patients. Cognition scores represent error rate (p ≤ 0.05, p ≤ 0.001)
|Information Processing speed||Cognitive Control||Social information processing||Total cognition scores|
From this table of results it can be observed that the variety of test scores vary from –ve to +ve numbers, with social skills test containing the most negative integers. It is also important to note that the higher the score, corresponds to a poorer performance but the lower the test score, the better the individual has performed. It can be observed from the table that there were more significant relations between social and behavioural problems when it was the cognitive abilities that had suffered the most. However for autistic traits, emotional problems & social skills, there was a strong relation observed with the total cognition score. Also there was a strong relation with conduct problems and peer problems under social information processing. From the table of results it was also suggested that age was an important factor, as various cognitive skills were seen to improve for information processing speed (r = -0.51, p < 0.001), cognitive control (r = -0.35, p = 0.003) , social information processing (r = -0.45, p < 0.001) and the total cognition score (r = -0.57, p < 0.001). In regards to social functioning and behaviour, age was the only variable that had any significant relation to hyperactivity-inattention (r = -0.31, p = 0.008) and conduct problems (r = -0.29, p = 0.012) indicating that age played a huge factor in the reduction of problems in patients.
A graph was plotted comparing NF1 & control group for cognitive skills:
Graph 1: represents 30 NF1 & control group patients that were tested on their cognitive abilities, comparing them both. Total cognition score was used as a covariate for autistic traits, social skills & emotional problems. Social info processing was also used as covariate for conduct and peer problems. Cognitive control was used as the covariate for analysis of hyperactivity inattention
From the graph it can be observed that there was a significant difference in test scores between the NF1 patients & control group. The use of covariates not only provided accurate results but allowed a thorough statistical analysis to be made. Through this many of the results that were accumulated from table 1 were seen to either be significant in reduction or increase of cognitive ability. It can be noted that NF1 patients scored significantly lower on emotional problems & autistic traits from table 1 however when made a covariate as total cognition score this had seen to reduce the differences in both groups. Although autistic traits remained a significant associate to cognitive impairment but emotional problems had no longer become a significant factor.
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Neurofibromatosis has created many complications ever since it was first discovered from studying the pathology of the disorder to coming up with a potential treatment. Although a cure for this genetic disorder seems as though it will require more time, with studies concerning the social implications that have affected children, it seems as though patients not only require a treatment to deal with the wounds but also a way to deal with mental trauma many of the patients have suffered from. From the data that has been collected, although NF1 patients have performed poorly in results, through this study the evidences have also pointed towards an overall improvement of cognition which may help reduce behavioural problems of children with NF1 to the point where differences with healthy controls are no longer significant. However our attention should still remain at the fact that a large amount of studies & research has to be conducted to further scientific reach into NF and potential treatments for the future of NF patients.
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