Mild cognitive impairment (MCI) happens when you experience a slight — but noticeable — decline in mental abilities compared to others your age. Mental abilities include: Memory. Reasoning and judgment. Planning and completing complex tasks. You may notice the decline in your abilities, or a loved one might. But the changes aren’t severe enough to interfere with daily, routine activities …

Migraine with aura (also called classic migraine) is a recurring headache that strikes after or at the same time as sensory disturbances called aura. These disturbances can include flashes of light, blind spots, and other vision changes or tingling in your hand or face. Treatments for migraine with aura and migraine without aura (also called common migraine) are usually the …

Microcephaly is a condition that causes your baby’s head to be smaller than expected for their size and age. Microcephaly happens when your baby’s brain needs more time to grow or doesn’t develop completely. The size of your baby’s skull depends on the size of their brain. Brain growth happens during fetal development and infancy. What are the types of …

Monoclonal gammopathy of undetermined significance (MGUS) is a blood disorder that affects plasma cells in your bone marrow. Most of the time, M proteins don’t cause issues and most people with MGUS don’t have symptoms. Healthcare providers often discover this condition after taking blood or urine samples as part of a routine physical examination. Rarely, this condition may also become a blood cancer or …

Myasthenia gravis is an autoimmune condition that causes skeletal muscle weakness. These are the muscles that connect to your bones and help you move. Myasthenia gravis usually targets the muscles in your eyes, face, neck, arms and legs. It can affect your ability to: Move your eyes or blink. Keep your eyes open. Make facial expressions. Chew, swallow and talk. Raise your arms up and …

MRSA (methicillin-resistant Staphylococcus aureus) is a type of bacteria that’s developed defense mechanisms (resistance) to antibiotics. MRSA infections are hard to treat because very few antibiotics are effective against them. MRSA most often causes skin infections but it can also cause serious infections in your lungs, heart and bloodstream. MRSA used to spread mostly in healthcare settings — among people in hospitals or …

Metatarsalgia (pronounced “MET-ah-tar-SAL-gee-ah”) refers to pain and inflammation in the ball of your foot, or forefoot. This is the area between the arches and toes on the bottom of your foot. The pain of metatarsalgia typically centers under one or more of the five bones at the bases of your toes, the metatarsal heads. Metatarsalgia has a number of different causes, including: …

Stage 4 prostate cancer happens when cancer spreads beyond the prostate to other parts of the body. Most prostate cancers are diagnosed when the cancer is only in the prostate. Sometimes prostate cancer doesn’t cause symptoms, and the cancer may not be detected until it has spread. When prostate cancer spreads to other parts of the body, it’s called metastatic …

Metachromatic leukodystrophy (MLD) is a rare genetic condition that leads to damage to the white matter of your central nervous system (brain and spinal cord) and peripheral nerves. MLD is one of several lysosomal storage diseases. White matter damage happens when fatty materials called sulfatides build up in your cells. The buildup impairs the growth of the myelin sheath (the protective covering around nerve fibers). Myelin gives white …

Mesenteric ischemia is an uncommon, dangerous condition that happens when parts of your digestive system don’t get enough blood flow. This usually happens because of a blockage in your blood vessels that provide blood to those areas. This condition is more common in people who are older, especially those with cardiovascular disease or blood clotting disorders. Without enough blood flow, the affected …