Final answer:
Identifying the cause of nervous system disorders is challenging due to unknown genes involved, lack of obvious brain structure defects, variability in symptom onset and presentation, and the interplay of genetic and environmental factors.
Step-by-step explanation:
It is difficult to identify the cause of many nervous system disorders for several reasons. These complex conditions cannot be attributed to a single factor. First, the genes associated with these diseases are often not known, making it challenging to determine the genetic component of these disorders. Additionally, these disorders frequently present without any noticeable defects in brain structure, which complicates the diagnoses process.
Moreover, the onset and display of symptoms vary widely between patients, further obscuring the pinpointing of a definitive cause. Finally, nervous system disorders can result from a combination of genetic mutations and environmental factors such as emotional trauma, stress, and exposure to hazardous chemicals, which complicates establishing a clear-cut cause.