What type of autoimmune disease attacks only brain cells and neurons without antibodies in blood work ?

Multiple Sclerosis: Multiple sclerosis is an immune-mediated/autoimmune disease that attack the myelin sheathes covering nerve axons but is not the result of an antibody-based autoimmune attack. It is thought to be the result of an attack by activated T-cells.

Autoimmune brain dz: Answers to your question include multiple sclerosis, rasmussen encephalitis, sometimes paraneoplastic diseases. Vasculitis conditions are numerous - some are not named. These attack blood vessels though, not neurons. Many of them have no blood test marker.

Several: The best known, of course in multiple sclerosis, but also, acute demyelinating encephalomyelitis in childhood, and a series of immune encephalitis conditions can be found. To date, no good blood test exists for MS, or ADEM, but one variant, neuromyelitis optica, can be confirmed via an anti-aquaporin study.