Memory loss is one of the most common cognitive symptoms that brings people to a neurologist, and one of the most frightening. Most people who come in worried about their memory do not have dementia, and many have something treatable. This page covers what separates normal forgetting from the kind worth investigating, and how the cause is found.
What memory loss is
Memory loss is difficulty forming, storing, or retrieving memories. It can affect recent memory, long-term memory, or both, and it can be temporary or lasting. Some slowing of recall is normal with age: the information is there and it takes longer to surface.
What is not normal is memory that is progressively worse, or that interferes with things you used to manage without thinking. That deserves an evaluation, and not because the news is likely to be bad. It is because so many of the causes can be corrected.
Short-term vs long-term memory loss
People search for these as if they were two different diseases. In practice the distinction is a clue to the cause. Short-term memory loss, where new information does not stick and you repeat questions or lose track of the week, is the pattern of sleep deprivation, depression, medications, and, when it is progressive over years, the early stage of Alzheimer's disease. Long-term memory loss, where established knowledge or old events fall away, is uncommon on its own and points elsewhere: a head injury, a stroke, encephalitis, heavy alcohol use, or a later stage of a neurodegenerative disease.
| Short-term memory loss | Long-term memory loss | |
|---|---|---|
| What it looks like | New information does not stick: repeated questions, a lost week, a forgotten conversation | Established knowledge or old events fall away |
| Common causes | Poor sleep, depression and anxiety, medications, thyroid or vitamin B12 problems; early Alzheimer's disease when it worsens slowly over years | Head injury, encephalitis, heavy alcohol use, a later stage of a neurodegenerative disease |
| Usually reversible? | Often, when the cause is sleep, mood, a medication or a deficiency | Less often; recovery depends on the cause |
| When to get checked | When it affects daily life, keeps getting worse, or family notice it | Promptly, because it is uncommon on its own |
The inability to form new memories has a name, anterograde amnesia; losing memories from before an event is retrograde amnesia. Both are unusual outside injury, seizure, or illness, and both call for prompt evaluation.
Normal aging or something more
| Situation | Usually normal aging | Worth evaluating |
|---|---|---|
| Names | Losing a name and recovering it later | Not recognizing people you know well |
| Losing things | Misplacing keys or a phone | Finding items in odd places, such as keys in the freezer |
| Conversations | Forgetting part of a conversation | Repeating the same question within an hour |
| Getting around | Pausing to think about directions | Getting lost on a familiar route |
| Everyday tasks | Needing a list for a complicated week | Struggling with a recipe or the bills you always handled |
| Words | Occasionally hunting for a word | Substituting wrong words often enough that others notice |
| Who notices | You notice, others do not | Family notice before you do, or disagree that anything is wrong |
The right-hand column is not a diagnosis. It is the threshold at which the cause is worth finding, and mood changes or lost interest in things you enjoyed belong there too. Between normal aging and dementia sits mild cognitive impairment.
Sudden memory loss or confusion is an emergency
Memory loss or confusion that starts suddenly, especially with weakness, trouble speaking, a severe headache, or a fall, can be a stroke or another acute problem. Call 911 or go to the nearest emergency department. The gradual memory changes described on this page are evaluated in the office.
Sudden memory loss
A first episode of sudden memory loss means calling 911. One cause that alarms families but passes on its own is transient global amnesia: a sudden inability to form new memories that lasts hours. The person stays alert and knows who they are, but asks the same questions again and again. It usually affects people over 50 and clears within a day, leaving a gap in memory for the episode itself. It is diagnosed only once a stroke and a seizure have been ruled out, which is why the emergency department comes first.
What causes memory loss and forgetfulness
The list of what causes memory problems is long, but in clinic a short list accounts for most of it. The rows are ordered roughly by how often we find them.
| Cause | What points to it | Reversible |
|---|---|---|
| Medications | Sedatives, sleep aids, some bladder and allergy medications, opioids. Symptoms that track a new prescription | Usually |
| Sleep apnea and sleep disorders | Snoring, waking unrefreshed, daytime sleepiness | Usually |
| Vitamin B12 deficiency, thyroid disease | Found on blood tests, often with fatigue or other body symptoms | Usually |
| Depression, anxiety, sustained stress | Attention is the problem, and what is not attended to is not stored. Can closely mimic early dementia | Usually |
| Heavy alcohol use | A long history of heavy drinking, sometimes with poor nutrition | Partly |
| Concussion or head injury | Onset dates to the injury | Often improves |
| Multiple sclerosis and other inflammatory conditions | Slower thinking more than forgetting, other neurological symptoms or an abnormal MRI. See memory problems in MS | Often steadies with treatment of the disease |
| Stroke, including small silent ones | A step change rather than a slow slide, or an abnormal MRI | Managed, not reversed |
| Neurodegenerative disease | Slow progression over years, recent memory affected first, noticed by family | Managed, not reversed |
Neurodegenerative disease is what people fear when they come in, and it is last on this list for a reason. The rows above it are more common and more fixable, so they get checked first.
Looking beyond the memory complaint
- Daily life: Repeated problems and functional changes help describe the concern.
- Causes: Sleep, medication effects, and other medical conditions may contribute.
- Next steps: Examination guides blood tests, imaging, or cognitive testing.
How the cause is found
- A detailed history, ideally with a family member present, because the person with the memory problem is often the least able to describe it.
- A neurological examination and cognitive screening during the visit.
- Blood tests for vitamin deficiencies, thyroid function, and other medical contributors.
- A medication review, every prescription and over-the-counter product. One of the highest-yield parts of the evaluation.
- Brain imaging, usually MRI, when the history or examination calls for it.
- Neuropsychological testing when a detailed map of which abilities are affected would change the plan.
Treatment
- Treat the cause. Replacing vitamin B12, correcting thyroid function, treating sleep apnea or depression, or stopping an offending medication often improves memory, sometimes markedly.
- Medication for neurodegenerative disease. Medications such as donepezil ease symptoms for many patients, and for some with early Alzheimer's disease the newer infusions, lecanemab and donanemab, aim to slow progression. We discuss honestly whether you are a candidate and where they are given.
- Memory aids and routine. Calendars, phone reminders, pill organizers, and a consistent daily structure help more than most people expect.
- The habits that protect the brain. Exercise, a Mediterranean-style diet, sleep, social contact, and control of blood pressure, cholesterol, and blood sugar. Our article on keeping your brain healthy covers these.
What an evaluation here involves
A memory evaluation starts with a 60-minute visit with Dr. Achillefs Ntranos, MD, a board-certified neurologist who trained at Mount Sinai and completed postdoctoral neuroimmunology research at Johns Hopkins. Bring your medication list, prior imaging or test reports, and, if you can, someone who knows you well. MRI images can be uploaded ahead through our patient tools page. We look for the less obvious contributors as well as the usual ones, including neuroinflammation, autoimmune conditions, and sleep disorders.
Cognitive testing is a computerized battery you complete from home, reviewed with you and your family with a written plan; when a full evaluation by a clinical neuropsychologist is needed, we arrange it and go through the report together. Most people who come in worried about their memory do not have dementia. Visits are in Beverly Hills, at our Los Angeles office, or by video anywhere in California, and follow-ups are usually every one to three months for 30 minutes. Request a visit without a referral; requests are confirmed, and messages between visits answered, within 1 business day. If the DMV has asked for a medical evaluation, we also perform DMV driver evaluations.
Building a useful memory assessment
- Examples: Specific changes in daily life help explain the concern.
- Screening: Cognitive tasks and neurological examination add evidence.
- Tests: Blood work, imaging, or detailed testing may clarify the cause.