A tremor is an involuntary, rhythmic shaking movement—but it is a symptom, not a diagnosis. Tremors may occur at rest, during movement, while holding a position, or when contracting muscles against resistance. Causes range from stress, caffeine, and medications to essential tremor, Parkinson’s disease, metabolic disorders, and other neurologic conditions. Understanding when and how the shaking occurs can provide an important clue to what is causing it.

Influenza usually lasts days or weeks—but could its effects on the brain last much longer? From von Economo's mysterious encephalitis lethargica to modern research linking severe infections with neuroinflammation and later dementia, scientists are reconsidering the long-term neurologic consequences of infection. The evidence does not prove that influenza causes dementia, but it raises an important question: can infection alter the trajectory of an aging brain?

Your ferritin may be marked “normal,” but does that mean your iron stores are adequate when you are losing hair? Iron deficiency can develop before anemia, and lower ferritin has been associated with telogen effluvium. But there is no proven universal ferritin target for hair growth—and low ferritin should not automatically mean taking iron. Learn why ferritin is a diagnostic clue, what can cause depleted iron stores, and why unexplained hair loss deserves a broader evaluatio