Seizures in Alzheimer's Disease

Symptoms are often "silent" and easily missed

confused older man with adult daughter

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People with Alzheimer's disease are estimated to have anywhere from a two- to six-fold increase in the risk of seizures compared to the general population. Over the course of the disease, anywhere from 10 percent to 26 percent will experience some form of seizure, both apparent and non-apparent, according to research from the Baylor College School of Medicine.

While it is still unclear which mechanisms trigger seizures, there are certain characteristics that can place an individual at higher risk.

Symptoms

A seizure is a sudden, uncontrolled electrical disturbance in the brain. While we tend to think of a seizure as a convulsion, it can sometimes manifest with subtle symptoms, such as changes in behavior, movement, feelings, or levels of consciousness.

Among the two most common types of seizure seen in people with Alzheimer's:

  • Partial complex seizures are those in which you become unaware of your surroundings and engage in unconscious actions such as fumbling, lip-smacking, wandering, or picking at clothes.
  • Generalized tonic-clonic seizures are characterized by all-body convulsions and are often accompanied by the abrupt loss of consciousness and/or bladder control.

Most seizures last anywhere from 30 seconds to two minutes. A seizure lasting longer for than five minutes is referred to as status epilepticus and is considered a medical emergency.

Having two or more seizures is classified as epilepsy.

Causes

Alzheimer’s disease is the most common form of dementia, affecting around five million Americans. Alzheimer's causes the progressive and irreversible deterioration of cognitive function, manifesting with the loss of memory and the gradual decline in the ability to think or reason. The disease is most commonly seen in the elderly and is believed to affect anywhere from four percent to 12 percent of people over 65.

Alzheimer's disease is caused by the gradual accumulation of a protein, known as beta-amyloid, in the brain. As the protein molecules begin to stick together, they create lesions (plaques) that interrupt the nerve pathways central to cognitive and motor function.

While it may seem reasonable to assume that the seizures are triggered by the degeneration of the brain, evidence strongly suggests that it is related more to beta-amyloid itself.

Beta-amyloid is actually a fragment of a larger compound known as amyloid precursor protein (APP). As APP is broken down, certain byproducts are released into the brain which can overexcite—and effectively overload—nerve pathways. As the disease progresses, the accumulation of these byproducts can cause nerve cells to fire abnormally, triggering seizures.

Risks Factors

Beyond the biochemical causes of Alzheimer's-related seizures, there are other factors that can place a person at an increased risk. Among them:

  • Early-onset Alzheimer's is associated with an increased likelihood of seizures, although the seizures themselves tend to develop in later-stage disease.
  • Mutations of the presenilin 1 (PSEN1) and presenilin 2 (PSEN2) genes are associated with the hyperproduction of APP. These genetic mutations are passed through families and, according to research from the Columbia University Medical Center, can increase the risk of seizures by 58 percent and 30 percent, respectively.

The severity of seizures also appears closely linked to the advancing stages of Alzheimer's. Institutionalized people tend to be the most severely affected (although it is possible that the seizures are simply recognized in an institutional setting where they may be otherwise missed at home).

Diagnosis

Not everyone with Alzheimer’s disease will experience seizures. Of those who do, they can be difficult to diagnose since the behaviors can often mimic those of the disease itself. This is especially true with partial complex seizures.

The diagnosis of Alzheimer's-related seizures is often an inexact science and one that may require input from a specialist known as epileptologist.

EEG and Other Diagnostic Tools

While an imaging study known as an electroencephalogram (EEG) can be used to confirm seizure activity, it has its limitation. The EEG measures electrical activity in the brain and, as such, can only definitively diagnose seizures if abnormalities occur during the test. As a result, only between 3 percent and 10 percent of Alzheimer's-related seizures are diagnosed with EEG alone.

With that being said, an EEG can sometimes detect abnormal electrical activity, known as epileptiform discharges, 24 to 48 hours after a seizure. If recurrent seizures are suspected, the doctor may recommend a wireless EEG in which a headset is worn for 24 to 72 hours to provide ongoing monitoring of brain activity.

While neuroimaging studies, such as computed tomography (CT) and magnetic resonance imaging (MRI), can detect changes in the brain consistent with Alzheimer's, they cannot tell us whether those changes are consistent with seizures. The same applies to genetic blood tests, which are more useful in supporting a diagnosis rather than making one.

Screening Questionnaire

Due to the limitations of the EEG and other lab-based tools, the diagnosis of Alzheimer's-related seizures is largely dependent on a seizure screening questionnaire. The contents of the questionnaire can vary but typically evaluate your risk based on:

  • Your medical history, including family history
  • Current or past medication use
  • Suspected seizure events, including a description of symptoms

Based on your responses, the epileptologist can use an algorithm to determine your seizure risk. A positive questionnaire result paired with abnormal EEG can deliver an accurate diagnosis in nine out of 10 cases.

Less definitive cases may still be treated presumptively, particularly in infirm or elderly people in whom a seizure may pose serious health risks.

Differential Diagnoses

While seizures are often missed in people with Alzheimer's disease, a type of seizure, known as an absence seizure, is sometimes misdiagnosed as early-stage Alzheimer's. An absence seizure is one in which an individual will suddenly "blank out" and wander aimlessly (a behavior referred to as amnestic wandering).

To differentiate between amnestic wandering with Alzheimer's and amnestic wandering with epilepsy, doctors may need to perform a physical exam, neuroimaging studies, EEG, and other tests to determine whether there are any signs of cognitive decline.

Since epilepsy can occur independent of Alzheimer's, the doctor may explore other explanations for the seizures, including:

Treatment

The treatment of Alzheimer's-related seizures typically involves the use of anticonvulsant medications such as Depakote (valproic acid), Neurontin (gabapentin), and Lamictal (lamotrigine). There is even some evidence that the anticonvulsant Keppra (levetiracetam), approved for the treatment of epilepsy, can help reverse some of the memory loss in people with Alzheimer's.

Other anticonvulsants should be used with caution as they may enhance the symptoms of dementia. These include Dilantin (phenytoin) which can impair memory and mental speed; Gabatril (tiagabine) which can affect verbal memory; and Topamax (topiramate) in which 40 percent of users experience significant memory and verbal impairment.

Even Tegretol (carbamazepine), considered a backbone of epilepsy therapy, is associated with a deterioration of mental speed and movement time. A dose adjustment can sometimes alleviate these effects.

A more invasive form of epilepsy treatment, known as deep brain stimulation (DBS), has shown promise in treating both conditions. However, because it requires surgery, DBS is considered only if epilepsy symptoms are severe and all other forms of pharmaceutical treatment have failed.

Neurosurgery is less commonly pursued in people with Alzheimer's since the seizures are primarily associated with the hyperproduction of APP rather than a brain injury.

A Word From Verywell

Because seizures are often "silent" in people with Alzheimer's, it is important to speak with your doctor if you even suspect they are occurring. There is increasing evidence that epilepsy is being underdiagnosed in this population of adults, particularly those who are elderly, homebound, and infirm.

Among some of the clues to look for:

  • Fluctuations in behavior or mental status, often occurring in spells
  • Infrequent rather than routine bedwetting
  • Sudden but subtle signs such as twitching and blinking

By identifying epilepsy early, it may possible to control the seizures and mitigate some of the ups and downs that characterize Alzheimer's disease.

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