DEAR DR. ROACH: I had a pituitary tumor that was discovered over 25 years ago. For years, I had an MRI with and without dye every six months. Then it changed to once a year. Can you get damage from too many brain MRIs? — D.J.

ANSWER: An MRI uses powerful magnetic fields to take pictures of the body, and the resulting detail of soft tissue (such as the brain) is generally more helpful than a CT scan. Furthermore, MRI does not use ionizing radiation, so there is not a risk of cancer as there is from excess X-rays and CT scans (although the risk of cancer from X-rays and CT scans is probably small).

There has been concern about the MRI dye, called gadolinium. Some gadolinium dyes have been found to accumulate in the brain as well as other organs such as the bone and the liver. There is, as of yet, no clear harm that has been identified with gadolinium accumulation; however, clinicians should consider whether contrast is really necessary. The United States Food and Drug Administration requires that patients receive educational information prior to receiving gadolinium contrast.

Some gadolinium contrast agents are more likely to cause accumulation than others. In particular, macrocyclic gadolinium-based contrast agents are less likely to be retained. In your case, the interval was probably changed due to so many years of being stable; the tumor is unlikely to grow.

DEAR DR. ROACH: I am a 92-year-old male with a number of ailments including psoriasis, chronic obstructive pulmonary disease (COPD) and congestive heart failure (CHF). I have had several medical procedures, including prostate surgery, valve replacement and stents.

Please clarify the term “brain fog.” How would I know if I had this? — P.G.

ANSWER: “Brain fog” refers to difficulty with brain function, especially trouble with thinking clearly, trouble with concentration and memory changes. Many medical conditions can cause this, including acute delirium (which, by definition, is a sudden change in brain function), dementia and medications. I have recently heard the term being used to describe what many people feel after a bout of COVID, particularly severe COVID. The term is also used to describe cognitive symptoms associated with chronic fatigue, sleep disorders, migraine and several other conditions.

Only you can tell if you have had this as there are no tests that can be done to determine if a person has brain fog. I think it differs from the changes that happen to people as they age, as these symptoms are more sudden and often include problems with multiple functions of the brain.

DEAR DR. ROACH: Which treatment do you recommend for lung kansasii bacteria? — M.

ANSWER: Mycobacterium kansasii is a slow-growing bacteria related to tuberculosis. Because it can cause the progressive loss of lung function, I recommend treatment for most people with this infection. Women are more likely to be diagnosed with this condition, especially postmenopausal women and those who are quite thin. People with underlying lung diseases, especially COPD from smoking or other causes, are at a particularly high risk.

Symptoms of M. kansasii include cough and abnormal mucus in most people, with a minority having fatigue, having shortness of breath, coughing up blood, getting a fever or losing weight. Because lung disease tends to be progressive without treatment, and treatment is usually effective, most people benefit from it. The most common treatment is three antibiotics that are taken for a year. The exact choice is made after a microbiological evaluation of the organism.

A year is a long time, and there are potential side effects from the antibiotics that need to be watched for. Generally, an expert, such as an infectious disease specialist or a pulmonologist, is responsible for the treatment of this condition.