The Lewy body dementia evidence guide
Dementia with Lewy bodies is a brain disease that affects attention, perception, sleep, and movement. A person's alertness may change sharply. They may see people or objects that are not present, act out dreams, or develop movement problems similar to Parkinson's disease. These features can make a seizure difficult to recognize.
Some seizures cause shaking. Others may cause a sudden pause, loss of response, speech difficulty, or unusual movement. This guide explains what DLB studies have found, which symptoms can look similar, and what is known about electrical activity without outward signs.
Start here
Dementia with Lewy bodies often causes attention and alertness to change. A possible seizure may stand out because it starts suddenly, follows a similar pattern each time, and has a clear recovery period. Studies that count diagnosed seizures cannot show how many events remain unrecognized. [1] [2] [6]
Each can occur in dementia with Lewy bodies for more than one reason. The event's timing, sequence, and recovery help clinicians compare a possible seizure with the person's usual changes and other explanations. [5] [6]
A small ear-recording study found brief seizure-related electrical discharges, often at night. These were not recorded seizures, and similar discharges also appeared in many people without the disease. Larger studies are needed before anyone can estimate how common or important this activity is. [7]
This page focuses on dementia with Lewy bodies (DLB). “Lewy body dementia” may also include Parkinson disease dementia. Doctors distinguish the two partly by when changes in memory and thinking begin in relation to movement symptoms. [5]
Lewy body disease (LBD) is a broader category that can include Parkinson disease. When a study uses this broader group, the guide identifies it instead of presenting the result as a DLB-only estimate. [4]
How often seizures are reported
Studies report different percentages because they examined different groups and periods of time. One counted seizures near dementia diagnosis. Another estimated the chance of a seizure after DLB symptoms began. A third reviewed seizures recorded across the full course of Lewy body disease. Each percentage answers a different question.
In a 2026 study, 13 of 458 people whose DLB diagnosis was confirmed after death had active seizures within three years before or after diagnosis. The study excluded people with a clinical history of stroke or traumatic brain injury. The percentage covers a defined period around diagnosis rather than the full course of the disease. [3]
A memory-center study of 178 people with DLB estimated a 14.7% chance of developing a seizure over time. The rate was nearly ten times the rate in a similar-age general population. The DLB group included 29 people who also met clinical criteria for Alzheimer's disease. This estimate describes risk over time rather than the percentage who had already experienced a seizure. [1]
A study reviewed medical records from symptom onset to death for 103 people whose Lewy body disease was confirmed after death. Seizures were recorded in 12.6%. This broader group included people with Parkinson disease as well as DLB, so the result is not a DLB-only estimate. [4]
Marawar and colleagues studied 1,376 people with DLB in a national database. Thirty-six had seizures recorded from three years before diagnosis through later follow-up, or 2.6%. Within the same study, 19 of 500 people whose diagnosis was confirmed after death had seizures, or 3.8%. These groups overlap, so their results cannot be added together. [2]
The records provided few details about the events, EEG findings, or treatment. Some seizures may have gone unrecognized, while specialized centers may have seen people with more complex illness. This study and the later Ting study also draw from the same national data source, so they are not completely independent.
Clinical seizures have been documented in several DLB and Lewy body disease research settings. The exact percentage varies, but the evidence is strong enough to make seizures part of dementia education and event assessment.
The national database study found that seizures often began near the time of diagnosis. In a four-person clinical report, epilepsy began before the first reported DLB symptoms in three people. This timing makes earlier events relevant to the history, although late-onset epilepsy alone does not predict DLB. [2] [6]
How seizures can appear
A 2025 report described four people with DLB and epilepsy that began later in life. The report is too small to show how common these events are, but it provides useful examples of how seizures can appear in someone with DLB. [6]
Reported focal seizures caused reduced awareness, difficulty speaking, and an unusual position of one arm. “Focal” means that the seizure begins in one area or network of the brain. A clear sequence of changes can be more useful to report than a general impression that the person seemed less alert.
Another reported pattern combined reduced awareness and speech difficulty with repeated mouth movements. The order of the changes matters. Record what happened first, what the person could respond to, and how the episode ended.
The report also described seizures with shaking and prolonged or repeated seizure activity without adequate recovery. Doctors call this status epilepticus, a medical emergency. Seizures in DLB can therefore include both brief changes and severe, prolonged events.
One person had ongoing jerks, seizure-related EEG findings, and a diagnosis of myoclonic epilepsy. Myoclonus means a brief, shock-like jerk. These movements also occur in DLB for reasons unrelated to epilepsy, so the cause must be evaluated. [6]
Count sudden jerks and seizures separately. One study estimated that sudden jerks occurred in 58.1% of its DLB group over time. That percentage describes myoclonus, not seizures. [1]
Example of a useful event description
“While seated and talking, he suddenly stopped answering. His right arm held an unusual position. After about a minute he responded again, but speaking remained difficult. His usual sleepy periods do not look like this.”
This note records the sequence and shows how the event differed from the person's usual sleepy periods. Sudden speech difficulty or another lasting neurological change may require urgent assessment for causes beyond seizures.
Symptoms that can look similar
DLB can cause changing attention, visual hallucinations, daytime sleepiness, fainting, dream enactment, and movement problems. Some seizures can produce similar outward changes. The event's beginning, sequence, duration, and recovery help clinicians compare the possibilities. [5] [6]
| What someone notices | What else could explain it | Which details help |
|---|---|---|
| Staring, disengagement, or reduced response | A usual change in attention or alertness, sleepiness, or a focal seizure. | How suddenly it began, how long it lasted, response to voice, movements, recovery, and how it compared with the person's usual pattern. |
| An unusual perception or apparent fear | A DLB-related change in perception, mood, or behavior, or a focal seizure. | The person's own description, if available, and whether the same short sequence has happened before. |
| Collapse or a fall | Fainting from a heart or blood-pressure problem, movement instability, or a seizure. | Posture and activity beforehand, warning symptoms, loss of response, movements, injury, and recovery. |
| Movement or vocalization during sleep | Acting out dreams, another sleep event, or a seizure during sleep. | When it occurred, the order and length of the changes, whether the pattern repeats, and what happened on waking. |
| Jerks, tremor, or unusual posture | A brief shock-like jerk or another movement problem associated with DLB, or a seizure. | What the movement looked like, whether awareness changed, what the person was doing, and whether it was new. |
The DLB descriptions come from clinical guidance and published cases. Seagull developed the observation prompts to help people describe events clearly. They have not been tested as a diagnostic tool. [5] [6]
“More confused” can mean many things. Record what happened before the change, what the person did or could not do, how long it lasted, and whether recovery was immediate or gradual. Repeated sequences are useful to report, although repetition alone does not establish epilepsy.
Recent illness, medication changes, poor sleep, and other new symptoms belong in the account. Each can change a person's alertness or behavior and may need clinical assessment.
What EEG studies have found
An EEG records the brain's electrical activity. In DLB research, it may be used to study the brain's usual rhythms or to look for seizure-related activity. These are different questions, and each finding has a different meaning.
The study included three groups of 41 people: DLB with Alzheimer's-related brain changes, DLB without those changes, and Alzheimer's disease. Each person had a 20-minute resting EEG. Brief seizure-related abnormalities appeared in one person in the first DLB group and no one in the second. General slowing was common in both DLB groups. [8]
The short study mainly measured general slowing. Brief seizure-related abnormalities appeared in only one participant. This result shows that slowing and seizure-related activity are different findings. It cannot tell us how often intermittent activity occurs outside a 20-minute recording.
Tested in DLB | Small early study
Musaeus and colleagues, 2023
Read the study ↗The study included 10 men with DLB and 15 people without DLB. Small electrodes worn in the ears recorded for two days at a time, and people with DLB could repeat the recordings over six months. In the first recording, brief discharges appeared in 8 of 10 people with DLB and 7 of 15 controls. The difference in those proportions was not statistically significant, although the discharges occurred more often in the DLB group. Most appeared at night. A short conventional EEG found none. [7]
The 80% figure describes brief discharges, not silent seizures. The study was small, the ear electrodes covered limited areas, and similar findings appeared in many controls. Some signals may have been incorrectly identified. The study excluded nursing-home residents and daily hearing-aid users, and some participants had difficulty tolerating the equipment.
Seagull's perspective: Longer, practical recordings deserve further study in DLB. Larger and more representative groups are needed to determine which signals are reliable, how often they occur, and whether they affect care.
Limits of EEG detection
In the four-person DLB report, routine EEG and short sleep EEG often showed no seizure-related abnormalities even though the patients had been diagnosed with epilepsy. The result of any EEG depends on when the recording occurred, how long it lasted, where the electrodes were placed, and whether the event happened during the recording. [6]
A brief recording may end before occasional activity occurs. Longer recordings provide more time, and sleep can be especially important. The report should say whether the person was awake or asleep and whether a familiar event occurred during the EEG.
Scalp electrodes may not clearly show activity that begins deep in the brain. Researchers demonstrated this in two selected people with Alzheimer's disease using electrodes placed closer to deep memory areas. This finding explains a possible scalp-recording limit, but it does not measure how often DLB activity is missed. [10]
General slowing reflects broad changes in brain function. A brief discharge may occur at another time. Neither finding by itself identifies the cause of a particular change in alertness, hallucination, or fall. Clinicians interpret the event description and the recording together. [6] [8]
A study percentage does not show how reliable a test is. The percentage depends on who was studied, how the recording was done, and what researchers counted. Measuring a test's sensitivity requires a dependable way to confirm which activity was truly present.
A brief seizure-related discharge can occur without a noticed event. It is different from an actual seizure recorded on EEG without outward signs. General slowing is a third, separate finding. Current DLB studies do not establish how often any of these findings occur across the full DLB population.
A normal or negative EEG can leave epilepsy unresolved. An unexplained symptom alone does not prove that epilepsy is present.
Why this matters for care
Some seizures reported in DLB required urgent treatment. Other events may remain difficult to explain. Clear descriptions and continuity between care settings help clinicians understand what happened and decide what should happen next.
Two of the four people in the 2025 report had prolonged or repeated seizure activity without adequate recovery. This small report cannot show how often that happens in DLB. It does show why ongoing unresponsiveness or a lasting neurological change requires prompt assessment. [6]
The Marawar study found no statistically clear difference in death rates between people with and without seizures after other factors were considered. The seizure group was small, so the result leaves substantial uncertainty. Alzheimer's studies cannot fill this DLB evidence gap. [2]
The four-person report described difficulty controlling seizures as well as medication side effects. A report this small cannot identify the best medicine for DLB. Research on treating diagnosed epilepsy also answers a different question from research on treating brief electrical discharges found by chance. [6]
A family member may know the person's usual pattern. A nurse may witness the beginning, while an emergency team sees only the recovery. Bringing those observations together gives clinicians a clearer account of the event.
Seagull offers these prompts to improve communication. They have not been tested as a method for diagnosing seizures.
Research insights
Current DLB research is exploring possible connections with vascular injury, changing brain rhythms, and longer recording methods. These are early findings that help define the next questions.
DLB study | 13 people with active seizures
Ting and colleagues, 2026
Read the study ↗Researchers examined brain tissue after death. Among the people with DLB, tiny areas of damage and larger areas damaged by loss of blood flow were linked with active seizures. People with a known clinical history of stroke had been excluded, so some vascular injury had only been found later. [3]
Only 13 people in the DLB group had active seizures. The study also limited which patterns of brain changes could be included. Its results cannot rule out a role for Alzheimer's-related changes in other people with DLB.
Seagull's perspective: A DLB diagnosis may not explain the full seizure picture. Future research should examine vascular injury and other brain changes alongside the primary dementia diagnosis.
DLB study | Published abstract
Musaeus and colleagues, online July 2026
Read the study ↗The study included 10 people with DLB, 25 with Alzheimer's disease, and 15 people without dementia. Researchers compared ear EEG findings with resting EEG repeated over six months. In the DLB group, people with brief discharges showed a different pattern of change in theta, a slower brain rhythm. Slowing at the start of the study was not linked with the discharges. [9]
The groups were small and unequal in size. The study found a relationship between EEG measures. It did not show that the discharges caused faster decline or that treatment would help.
Seagull's perspective: This study asks whether brief discharges are connected with changes in brain activity over time. Larger studies must determine whether the relationship is reliable and whether it affects memory, daily function, or treatment.
Tested in temporal lobe epilepsy | Not yet tested in DLB
The HEAnet study used computer analysis to look for scalp EEG patterns linked with seizure-related activity in a deep memory area. Researchers compared scalp recordings with electrodes closer to that area. The study included people with temporal lobe epilepsy and people without epilepsy, not people with DLB. [11]
The DLB question: Can this method separate meaningful discharges from DLB-related slowing, movement, and other recording artifacts? It must also show whether a finding helps explain a person's events.
Tested in epilepsy | Not yet tested in DLB
The UMPIRE study tested a recording device placed beneath the scalp in 26 adults with epilepsy. Among eight people who had seizures visible on regular scalp EEG, all 25 of those seizures also appeared in the beneath-scalp recording. The study did not show whether the device finds deep seizures that regular scalp EEG cannot see. [12]
The DLB question: Would months of recording provide useful information, and would the procedure and ongoing equipment be acceptable for people with DLB and their care partners?
How Seagull evaluates a technology claim
Inclusion in this guide is research commentary. It is not a product endorsement or a statement that the technology is available for dementia care.
What research needs to answer next
Future studies should record detailed event histories and link them with EEG recordings when possible. Looking back at a medical record may miss important details about how an event began, unfolded, and ended.
Larger studies should count brief discharges and recorded seizures separately. They also need to report recording length, sleep, electrode coverage, and how the EEG was interpreted. Findings in people without DLB are essential for comparison.
DLB alone, DLB with Alzheimer's-related changes, and broader Lewy body disease are different groups. Vascular injuries may add another source of risk.
Research should measure changes that matter in daily life, including thinking, function, safety, sleep, comfort, and care-partner burden. A lower number of EEG discharges alone would not prove that care improved.
Studies need to include people at different stages of DLB, women as well as men, people in residential care, hearing-aid users, and people who need help wearing recording equipment. A technology must also be practical to use.
Sources and editorial approach
Seagull Health prepared this focused review using recent DLB research, clinical guidance, and selected studies of emerging detection technology. The evidence was reviewed on . This is an educational review rather than a clinical guideline or complete systematic review.
The core literature comes from Seagull's dementia-seizure resource collection, with added primary research and DLB clinical guidance. Every source below was published within the past ten years. The 2026 Neuroscience paper was available online in July, before its later issue date.
The guide identifies whether a source is a group study, case report, short EEG study, longer recording study, or technology study in another population. Seagull's perspective is clearly labeled. Several citations may use the same data, and an early finding does not become a clinical recommendation simply because it appears in a published study.
Beagle et al. (2017). Relative Incidence of Seizures and Myoclonus in Alzheimer's Disease, Dementia with Lewy Bodies, and Frontotemporal Dementia. Journal of Alzheimer's Disease.
Retrospective memory-center cohort, including 178 people in the DLB group. Reports seizures and myoclonus separately; includes some people meeting both DLB and Alzheimer's clinical criteria.
Marawar et al. (2020). Seizure occurrence and related mortality in dementia with Lewy bodies. Epilepsy & Behavior.
NACC database analysis of 1,376 people with clinically defined DLB. Reports seizure occurrence and mortality; event descriptions, EEG confirmation, and treatment data were limited.
Ting et al. (2026). Neuropathologic Correlates of Seizures in Patients With Alzheimer Disease and Dementia With Lewy Bodies. Neurology.
Autopsy-confirmed NACC cohort, including 458 DLB cases and 13 with active seizures. Vascular associations are exploratory, with few seizure cases and restricted pathology-based inclusion.
Vöglein et al. (2022). Seizure prevalence in neurodegenerative diseases: a study of autopsy-proven cases. European Journal of Neurology.
Medical-record review across the symptomatic course in 103 autopsy-confirmed Lewy body disease cases. This pathology group includes Parkinson disease as well as DLB.
McKeith et al. (2017). Diagnosis and management of dementia with Lewy bodies: Fourth consensus report of the DLB Consortium. Neurology.
Expert consensus. Defines DLB features and supportive EEG findings; not a seizure-prevalence or seizure-recognition validation study.
Porché et al. (2025). Late onset epilepsy and dementia with Lewy bodies: Underestimated association?. Journal of Alzheimer's Disease Reports.
Four selected clinical cases. Adds seizure descriptions, timing, EEG findings, and tolerability observations; cannot establish prevalence or rank treatments.
Musaeus et al. (2023). Subclinical Epileptiform Activity in Dementia with Lewy Bodies. Movement Disorders.
Exploratory ear-EEG study; small, selected sample. Device-company funding and author relationships disclosed.
van der Zande et al. (2018). EEG Characteristics of Dementia With Lewy Bodies, Alzheimer's Disease and Mixed Pathology. Frontiers in Aging Neuroscience.
Three matched groups of 41, studied with short resting-state EEG. Primarily addresses dementia-related EEG patterns, not detection of intermittent seizures.
Musaeus et al. (2026; online 3 July). Epileptiform discharges are associated with increased theta activity over time in patients with Lewy body dementia. Neuroscience.
Exploratory longitudinal EEG analysis. This guide's account is based on the published abstract; small, unbalanced subgroups limit interpretation.
Lam et al. (2017). Silent hippocampal seizures and spikes identified by foramen ovale electrodes in Alzheimer's disease. Nature Medicine.
Two selected Alzheimer's cases with invasive recordings. Included only to explain a scalp-detection limitation, not as direct DLB evidence.
Abou Jaoude et al. (2022). Noninvasive Detection of Hippocampal Epileptiform Activity on Scalp Electroencephalogram. JAMA Neurology.
Machine-learning research in temporal lobe epilepsy and controls. Not a validation study in DLB.
Halliday et al. (2025). The UMPIRE study: A first-in-human multicenter trial of bilateral subscalp monitoring for epileptic seizure detection. Epilepsia.
Implanted recording feasibility and safety study in adults with epilepsy. No DLB cohort; manufacturer relationships disclosed.