Given that less than 10 percent of those with sarcoidosis will have neurological involvement, and possibly later on in their disease course, neurosarcoidosis has a prevalence of less than four per 100,000.Sarcoidosis most commonly affects young adults of both sexes, although studies have reported more cases in females. Incidence is highest for individuals younger than 40 and peaks in the age-group from 20 to 29 years; a second peak is observed for women over 50.Sarcoidosis occurs throughout the world in all races with an average incidence of 16.5/100,000 in men and 19/100,000 in women. The disease is most prevalent in Northern European countries and the highest annual incidence of 60/100,000 is found in Sweden and Iceland. In the United States sarcoidosis is more common in people of African descent than Caucasians, with annual incidence reported as 35.5 and 10.9/100,000, respectively. Sarcoidosis is less commonly reported in South America, Spain, India, Canada, and the Philippines. There may be a higher susceptibility to sarcoidosis in those with coeliac disease. An association between the two disorders has been suggested.The differing incidence across the world may be at least partially attributable to the lack of screening programs in certain regions of the world and the overshadowing presence of other granulomatous diseases, such as tuberculosis, that may interfere with the diagnosis of sarcoidosis where they are prevalent. There may also be differences in the severity of the disease between people of different ethnicities.
Visual problems may also be the result of papilledema (swelling of the optic disc) due to obstruction by granulomas of the normal cerebrospinal fluid (CSF) circulation.Seizures (mostly of the tonic-clonic/"grand mal" type) are present in about 15 percent and may be the presenting phenomenon in 10 percent.Meningitis (inflammation of the lining of the brain) occurs in 3–26 percent of cases. Symptoms may include headache and nuchal rigidity (being unable to bend the head forward). It may be acute or chronic.Accumulation of granulomas in particular areas of the brain can lead to abnormalities in the function of that area. For instance, involvement of the internal capsule would lead to weakness in one or two limbs on one side of the body. If the granulomas are large, they can exert a mass effect and cause headache and increase the risk of seizures. Obstruction of the flow of cerebrospinal fluid, too, can cause headaches, visual symptoms (as mentioned above) and other features of raised intracranial pressure and hydrocephalus.Involvement of the spinal cord is rare, but can lead to abnormal sensation or weakness in one or more limbs, or cauda equina symptoms (incontinence to urine or stool, decreased sensation in the buttocks). Endocrine
Granulomas in the pituitary gland, which produces numerous hormones, is rare but leads to any of the symptoms of hypopituitarism: amenorrhoea (cessation of the menstrual cycle), diabetes insipidus (dehydration due to inability to concentrate the urine), hypothyroidism (decreased activity of the thyroid) or hypocortisolism (deficiency of cortisol).