Frontotemporal dementia (FTD), a common cause of dementia, is a group of disorders that occur when nerve cells in the frontal and temporal lobes of the brain are lost. This causes the lobes to shrink. FTD can affect behavior, personality, language, and movement.

Cephalic disorders affect the central nervous system as it develops. They may also affect the brain and the growth of the skull.

A developmental venous anomaly is an unusual arrangement of small veins in the brain or spinal cord. It's a condition you are born with.

Arteriovenous malformations is the abnormal formation of veins and arteries. It can develop in the fetus or newborn baby.

Pneumocystis pneumonia or PCP is a fungal infection in 1 or both lungs. It is common in people who have a weak immune system, such as people who have AIDS.

Opportunistic infections that other people might fight off easily could make you really sick if you have HIV. Getting one or more of these opportunistic infections could mean that your HIV has advanced to AIDS.

HIV affects the brain and nervous system and can cause dementia.

The skull base offers support from the bottom. Think of it as the floor of the skull, where the brain sits. Tumors can form at the base of the skull.

Lymphadenitis is an infection in one or more lymph nodes. The lymph nodes help filter bacteria, viruses, and other unwanted material from the body.

Vascular dementia is caused by decreased blood flow to brain tissue causing signs of dementia. Read on for details about this condition.