<Tr> <Td> </Td> <Td> This section is missing information about a number of brain disorders that not currently listed here . Please expand the section to include this information . Further details may exist on the talk page . (July 2016) </Td> </Tr> <P> Addiction is a disorder of the brain's reward system which arises through transcriptional and epigenetic mechanisms and occurs over time from chronically high levels of exposure to an addictive stimulus (e.g., morphine, cocaine, sexual intercourse, gambling, etc .). </P> <P> Arachnoid cysts are cerebrospinal fluid covered by arachnoidal cells that may develop on the brain or spinal cord . They are a congenital disorder, and in some cases may not show symptoms . However, if there is a large cyst, symptoms may include headache, seizures, ataxia (lack of muscle control), hemiparesis, and several others . Macrocephaly and ADHD are common among children, while presenile dementia, hydrocephalus (an abnormality of the dynamics of the cerebrospinal fluid), and urinary incontinence are symptoms for elderly patients (65 and older). </P> <P> ADHD is an organic disorder of the nervous system . ADHD, which in severe cases can be debilitating, has symptoms thought to be caused by structural as well as biochemical imbalances in the brain; in particular, low levels of the neurotransmitters dopamine and norepinephrine, which are responsible for controlling and maintaining attention and movement . Many people with ADHD continue to have symptoms well into adulthood . Also of note is an increased risk of the development of Dementia with Lewy bodies, or (DLB), & a direct genetic association of Attention deficit disorder to Parkinson's disease two progressive, and serious, neurological diseases whose symptoms often occur in people over age 65 . </P>

What nervous system disorder occurs when lesions form on the cerebral cortex causing dementia