What Are Atonic Seizures?

What You Need to Know About Atonic Seizures

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Atonic seizures (also known as drop attacks) are one of several types of seizures that can occur as a result of various underlying causes. “Atonic” means loss of muscle tone. This type of seizure is also known as akinetic or drop seizures.

Atonic seizures oftentimes begin during childhood are most common in children, although they may continue into adulthood. This type of seizure is often present in people who have other types of seizures as well, such as tonic or myoclonic seizures.

Atonic seizures are rare—among children with epilepsy, only 1 to 3 percent have atonic seizures.

What Is a Seizure?

Neurons, or nerve cells in the brain, communicate with each other constantly by transmitting electrical impulses from one to another. Voluntary movement (as well as involuntary movement) is controlled and regulated by these nerve transmissions.

A seizure is the result of the brain receiving surges of abnormal electrical signals, interrupting normal electrical brain functioning in the nerve cells that control the muscles. Primarily, there are two types of seizures: generalized and focal. The difference is mainly where they begin in the brain.

Generalized seizures involve the entire brain, and subsequently, affect the entire body. They may also cause convulsions (non-voluntary movements), but some generalized seizures (such as absence seizures) do not cause convulsions. There are six types of generalized seizures: absence (petit mal), atonic, tonic-clonic (grand mal), clonic, tonic, and myoclonic.

Focal seizures (also called partial seizures) are those that start in one part of the brain and affect the part of the body controlled by that part of the brain. Depending on the type of seizure, an atonic seizure can also be focal.

What Are Atonic Seizures?

Normally, the muscles are contracted slightly when a person sits or stands, which allows the body to stay upright. 

In an atonic seizure, a person’s muscles do not clench up as they do in the more well-known types of seizures called tonic-clonic (convulsive or grand mal) type. 

Atonic seizures cause a person’s muscles to suddenly become flaccid. 

In fact, the muscles become so relaxed that the person having atonic seizures often falls forward because the muscles are unable to support the body. It may be difficult to pinpoint an atonic seizure if a person is lying down when it occurs. This is because the cardinal sign of atonic seizures is when a person suddenly falls straight to the ground, unlike other types of seizures where muscle contractions propel a person forward or backward and may subsequently cause them to fall. 

In infants or those who are not standing up, atonic seizures may appear as a head drop.

During the seizure, the person is limp and unresponsive. Atonic seizures are less common than many other types of seizures, but they can occur in conjunction with other types. 

An atonic seizure may begin with one or more myoclonic jerks. This type of seizure is usually short in duration, coming on without warning. Recovery is usually quick (excluding any injuries that may occur from falling). Falls from atonic seizures oftentimes results in injuries to the face and head.

Types of Atonic Seizures

Atonic seizures can be categorized as focal seizures (starting in one part of the brain) resulting in muscle tone loss in only one part of the body. This is referred to as a focal motor atonic seizure.

When the atonic seizure starts on both sides of the brain, it is referred to as a generalized onset atonic seizure.  Most of the time, atonic seizures are generalized seizures. Generalized atonic seizures start out with a sudden loss of muscle tone in the head, trunk, or the entire body. 

Atonic seizures usually result in loss of consciousness (either for a short time span or longer). This type of seizure normally lasts less than 15 seconds but may last up to several minutes. After an atonic seizure, a person will quickly become alert and conscious.

Symptoms

Symptoms of atonic seizures may include:

  • a sudden loss of muscle strength
  • going limp and falling to the ground
  • if seated, the person’s head will appear to suddenly drop down
  • remaining conscious or experiencing a brief loss of consciousness
  • drooping eyelids
  • head nods
  • jerking movement

Causes

Anything that disrupts the normal nerve transmission in the brain can cause a seizure. This can include:

  • a very high fever
  • low blood sugar
  • high blood sugar
  • alcohol or drug withdrawal
  • a brain concussion (from an injury to the head)
  • strokes
  • some types of illnesses
  • a brain tumor
  • other factors

Common causes of seizures in infants include:

  • birth trauma
  • congenital issue (a problem at birth)
  • high fevers (not usually associated with epilepsy)
  • chemical or metabolic imbalance
  • other unknown factors

Risk Factors and Triggers

The underlying cause of atonic seizures is often unknown. Changes in the genes may be responsible for an increased risk of having atonic seizures.  In fact, it is estimated that there may be as many as 500 genes related to epilepsy. 

Children are most often affected by atonic seizures, but this type of seizure can occur at any age. Triggers for atonic seizures may include hyperventilation (fast breathing) and/or flickering lights.

What Is Epilepsy?

Epilepsy is a condition that affects nearly 2.2 million people in the United States. It’s one of the most common nervous system disorders.  When a person has two or more seizures, they are diagnosed with epilepsy of unknown cause.

Atonic seizures are commonly the type of seizure experienced with specific types of epilepsy, such as Lennox-Gastaut syndrome (LGS) and Dravet syndrome (DS).

LGS is a severe childhood form of epilepsy involving:

  • medication refractory seizures (when medication is not reducing the seizure episodes)
  • drop attacks (atonic seizures)
  • atypical absence seizures

Atypical absence seizures involve a less abrupt onset type of seizure compared to typical absence seizures, associated with loss of muscle tone in the trunk, limbs, or head and a gradual slump as well as mild myoclonic jerks.

Dravet syndrome (DS) is a severe form of epilepsy that includes symptoms such as:

  •  frequent, prolonged seizures often triggered by high body temperature (hyperthermia)
  • developmental delay in infants and children
  • speech impairment
  • ataxia (loss of full control of body movements)
  • hypotonia (an abnormally low level of muscle tone)
  • sleep disturbances
  • other health problems

When to See a Healthcare Provider

The first time anyone has a seizure (of any type) the healthcare provider should be notified immediately and diagnostic steps should be made, including an examination of the medical history and a physical exam. After a person is diagnosed, it’s important to seek immediate medical attention in any of the following scenarios:

  • a seizure lasting longer than five minutes
  • breathing that doesn’t normalize after the seizure is over
  • unconsciousness that lingers after the seizure is over
  • a second seizure that occurs after the first (cluster seizure)
  • a high fever occurs
  • heat exhaustion is experienced
  • a seizure that occurs during pregnancy
  • any time diabetes is diagnosed
  • when an injury occurs after a seizure

Diagnosis

Whenever a person has a seizure, it’s imperative that the healthcare provider discern the type of seizure and which area of the brain is involved. This is because the anti-seizure medication regime is partially based on the type and duration of seizures. Input from observers (via written descriptions or video recordings) describing the event is an important part of the diagnostic assessment.

An electroencephalogram (EEG) is the primary diagnostic tool used to diagnose seizures. 

The EEG procedure involves attaching electrodes to the scalp to measure the electrical activity in the brain.  An EEG can display abnormal electrical activity patterns in the brain. Various types of seizures can be identified by observing these patternsEEG tests are also conducted to measure the effectiveness of anti-seizure medications by testing how the drugs help with the electrical malfunction in the brain.

Magnetic resonance imaging (MRI) and computed tomography (CT) scans are also used to study important factors such as where the seizure occurs in the brain. These scans are often used to rule out possible causes of seizures such as a stroke.

If a diagnosis isn’t clear and anti-seizure medication isn’t effective, tests may be done to find out other origins of the problem that could be causing the falls.

Treatment

The goal in treating atonic seizures is to control, decrease the frequency, or stop the seizures without interfering with a person’s normal life’s activities—also referred to as activities of daily living (ADLs). The treatment for atonic seizures depends on many factors, including:

  • properly identifying the type of seizures
  • assessing the frequency of seizures
  • diagnosing the underlying cause of the seizures (when possible)
  • the person’s age, health status, and medical history
  • evaluation of the person’s medication tolerance and/or tolerance of other types of treatment

Factors that impact treatment options include:

  • the treatment goals
  • preferences of the parents or person with seizures (in adult patients)
  • side effects
  • the cost of the medicine
  • adherence with the use of the medicine

In addition to medication, the health care provider will most likely encourage:

  • proper rest to avoid sleep deprivation (which may trigger seizures)
  • avoiding other things that trigger a seizure (such as flashing lights, a fever, and heat exhaustion)
  • wearing a helmet to protect the head if falling as a result of an atonic seizure

Anti-Seizure Medication Administration

The health care provider will take several factors into consideration when prescribing anti-seizure medications. These include:

  • using the type of anti-seizure medication that is specific for the type of seizure
  • prescribing the lowest dose that will achieve seizure control
  • administering frequent blood and urine tests to ensure proper medication management

Types of Medication

Medication, in the form of anti-epileptic or anti-seizure drugs, is the most common form of treatment for seizures; however, it may take the healthcare provider some time to discover the right drug and the best dosage for each person. Types of anti-seizure medication includes:

  • Ethosuximide (Zarontin), which is commonly used as the first choice in anti-seizure drug treatment
  • Valproic acid (Depakene), another anti-seizure drug option, that is not recommended for women who are pregnant or of childbearing age because this medication can cause an increased risk of birth defects
  • Lamotrigine (Lamictal), which may be less effective than ethosuximide or valproic acid, but it has fewer side effects
  • Clobazam (Onfi)

Tips for Taking Anti-Seizure Medicine

Always take anti-seizure medication exactly as prescribed by the healthcare provider (including scheduled time and dosage). Discuss possible side effects and report any that occur to the healthcare provider as soon as possible.

Anticipate that several tests will be performed to measure the effectiveness and safety of anti-seizure medications.

These tests may include:

  • frequent blood work and urine to measure the optimal level (called the therapeutic dose) that works best to control seizures with minimal side effects
  • other types of tests to measure the effectiveness of anti-seizure medications in the body (such as EEGs)

Consult with the healthcare provider regarding any activity restrictions due to side effects (such as drowsiness) caused by anti-seizure medications. Many people taking anti-seizure medications are encouraged to refrain from operating heavy machinery.

Consult with the healthcare provider before taking other medication (including over the counter drugs) many of which could interfere with the effectiveness of anti-seizure medications or cause harmful side effects.

Other Types of Treatment for Atonic Seizures

The Ketogenic Diet

Ketogenic diets have been used to control seizures for some patients who don’t respond to medications—the diet is most often used to treat children. A ketogenic diet is a low-carbohydrate and high-fat diet.

The ketogenic diet tricks the body into a state of starvation from the lack of carbohydrates. This results in a state of ketosis in the brain. The diet was identified decades ago, but in 1990, studies began to back up its results in lowering seizures in kids who were not responding well to anti-seizure medication.

"The connection between metabolism and epilepsy has been such a puzzle," said Gary Yellen, Ph.D., professor of neurobiology at Harvard Medical School. He was introduced to the ketogenic diet through his wife, Elizabeth Thiele, MD, Ph.D., HMS professor of neurology, who directs the Pediatric Epilepsy Program at Mass General Hospital for Children.

"I've met a lot of kids whose lives are completely changed by this diet, it's amazingly effective, and it works for many kids for whom drugs don’t work," said Yellen.

Surgical Procedures

Vagus Nerve Stimulator (VNS)

VNS is a surgically implanted device that is sometimes implanted (and used in conjunction with anti-seizure medications) to help prevent seizures by sending small electrical impulses through a nerve in the neck—called the vagus nerve—to the brain.

A study published in 2013 discovered that while VNS was effective in lowering the incidence of some types of seizures (tonic-clonic and myoclonic type), it was ineffective at reducing atonic or tonic seizures in children with Lennox-Gastaut or Lennox-like syndrome.

Corpus Callosotomy

A surgical procedure called a corpus callosotomy (CC) is an operation aimed at interrupting the abnormal electrical activity in the brain, which spreads from one hemisphere to the other during a generalized seizure (such as an atonic seizure).

 This is done by severing (cutting) the corpus callosum—an area of the brain located between the two hemispheres. This does not usually stop the seizures; they continue on the side of the brain in which the seizures start. 

Surgery is not recommended for everyone with atonic seizures, but it may be a good option for some. A 2015 study involving patients with atonic seizures and drop attacks undergoing CC and VNS discovered that 58 percent of those who had CC performed were free of atonic seizures after the procedure, compared to only 21.1 percent of the study subjects who had VNS implants.

Coping

The prognosis or projected outcome of atonic seizures depends primarily on the cause. Sometimes epilepsy syndromes (epilepsy of unknown cause) will go away once a child grows older. Usually, a person must be seizure-free for one or two years before the option to stop anti-seizure medication is considered. 

This decision must always be made by the prescribing healthcare provider. In other instances, a child with atonic seizures may end up needing to take anti-epileptic medications into adulthood and during their entire life span. 

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