DEAR DR. ROACH: My 28-year-old son is in the hospital. He hasn’t been acting like himself for a few weeks (not sleeping nor eating well), and he suddenly had four seizures. The doctors are worried about a condition called autoimmune encephalitis.

— J.M.

ANSWER: Encephalitis means inflammation of the brain, which is a rare condition. It can be caused by infections (especially viruses) or autoimmune reactions, including antibody-mediated encephalitis. There are only 2,000 cases per year of antibody-mediated encephalitis in the United States.

Several different antibodies can be responsible, and each attacks a specific protein in the brain. At age 28, the most likely type of antibody causing antibody-mediated encephalitis is anti-NMDAR. With this syndrome, children and young adults often develop psychiatric symptoms including insomnia, abnormal movements, agitation and sometimes hallucinations. Seizures are common.

The diagnosis is made by finding the antibody in cerebrospinal fluid after a lumbar puncture (“spinal tap”). An MRI scan is also done to help confirm the diagnosis and exclude other causes.

Some cases of antibody-mediated encephalitis are associated with tumors. For example, young women with anti-NMDAR encephalitis have ovarian tumors over 50% of the time, while young men only have a tumor 5% to 10% of the time.

Treatment is best when begun early and when it is designed to reduce the immune system’s attacks on the body. With early treatment, most people do well.

DEAR DR. ROACH: I frequently can hear my heart beating as though it is inside my head. I am 82 years old and comparatively healthy, all things considered. When this happens, I hold my nose, close my mouth, and blow very hard, which creates pressure and a forceful popping sound in my ears. This removes the sound of the heartbeat for quite a while. What is happening to me? Is something wrong with my ears?

— W.C.G.

ANSWER: Hearing a heartbeat is concerning because there might be an abnormality in the blood vessels near your ear, specifically an aneurysm. Fortunately, this is uncommon, but you should go and get it checked out by your doctor.

When the pressure in the ear is very different from the outside, the eardrum does not move properly, so sounds from the outside are muffled, making internal sounds seem louder. “Clearing” your nose equalizes pressure in the middle ear by forcing open the Eustachian tube. The popping sound is the air pressure equalizing.