New Research Shows Why a Delayed Diagnosis of Focal Seizures Is So Dangerous

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Key Takeaways

  • Undiagnosed focal seizures are 10 times more likely to cause car accidents than motor seizures.
  • Focal seizures can take up to six years to diagnose, but once identified, can be easily treated with antiseizure medication.
  • Experts say that education is the best way to improve diagnosis time.

A new study from the New York University School of Medicine is highlighting safety concerns associated with undiagnosed focal epilepsy.

Epilepsy is a neurological condition characterized by seizures. But seizures don't always manifest themselves as the jerking or stiffening movements most people think of. Those are called motor seizures, and affect both sides of the brain. Nonmotor seizures, or focal seizures, look a lot different because they are limited to one area or side of the brain, making their diagnosis difficult. Researchers wanted to explore the repercussions of that delayed diagnosis.

The study, published in Epilepsia, included 447 epilepsy patients from the United States, Canada, Australia, and Europe who were being monitored at epilepsy centers worldwide.

Of the 447 patients in the study, 246 showed early signs of nonmotor seizures. Despite having symptoms, it took these patients up to six years to be diagnosed with epilepsy. By comparison, the 201 patients with motor seizures only experienced a two-month delay in diagnosis.

The researchers say that the disparity in diagnosis is dangerous: A lack of treatment can threaten the safety of patients and the general public—especially when patients with focal seizures who have not been diagnosed get behind the wheel of a car.

The study's findings support the researcher's concerns: 23 patients reported having one or more car accidents before their epilepsy diagnosis. Nineteen of the patients had non-motor seizures, while only four had motor seizures.

The delay in diagnosis and treatment means that patients with focal seizures are 10 times more likely to be involved in a motor vehicle accident (MVA) than patients with motor-seizures.

“Driving is a major issue among my patients with epilepsy,” Robert E. Hogan, MD, a neurologist at Barnes-Jewish Hospital and second vice president of the American Epilepsy Society, tells Verywell. “Patients with focal seizures may not remember having the seizure. The brain doesn’t turn off, but there may be a short period of time they are unaware and unfortunately, a car accident is what brings a lot of people to our center.”

What Is a Focal Seizure?

According to the Epilepsy Foundation, focal seizures are limited to one area or side of the brain. Most focal seizures last no longer than 2 minutes. In a focal onset aware seizures, people remain aware of their surroundings, but may feel frozen or be unable to respond to the environment. In focal impaired awareness seizures, the person loses awareness of their surroundings.

Nonmotor vs. Motor Seizures

There are several types of seizures. Each type is classified by the area of the brain that is affected. The classes that are referenced most often are nonmotor (focal seizures) and motor (generalized seizures). 

Nonmotor (focal) seizures can include:

  • Changes in heart rate, breathing, or coloration
  • Blank stare
  • Inability to respond to the environment
  • Behavioral arrest (stopping talking or moving)
  • Confusion
  • Slowed thinking
  • Problems talking and understanding
  • Sudden fear, dread, anxiety or even pleasure
  • Changes in hearing, vision, or taste
  • Feelings of numbness, tingling, or pain

Motor seizures can include:

  • Jerking (clonic)
  • Stiffness (tonic)
  • Loss of muscle (atonic)
  • Repeated or automatic movements (automatisms)

Delay in Diagnosing Focal Seizures

The delay in diagnosing focal seizures can be attributed to the exhibited signs and symptoms being very elusive. They can be mistaken for a number of different conditions.

Robert E. Hogan, MD

Focal seizures are treatable, but the biggest obstacle is diagnosis.

— Robert E. Hogan, MD

“The reason focal seizures can take a long time to diagnose is that they are subtle,” Robert Fisher, MD, a neurologist and director of the Stanford Epilepsy Center, tells Verywell. “For many physicians, the medical history of a patient has to reach a certain threshold before it triggers a possible focal seizure diagnosis. Unless they are falling down and convulsing then some doctors don’t think of symptoms being a seizure.”

According to the International League Against Epilepsy (ILAE), focal seizures are limited to one hemisphere of the brain and have several sub-classifications: focal-aware and focal impaired awareness. The latter is the most dangerous because the patient loses consciousness for short periods of time, leaving them unaware of their surroundings.

Another complication in the diagnosis of focal seizures is ruling out epilepsy imitators, including behavioral, psychosocial, psychiatric, and sleep-related conditions that can lead to a false diagnosis.

“Some symptoms can include what looks like daydreaming or a lack of focus, which may be presumed as rude. But in fact, [the person] is experiencing a seizure,” Fisher says.

Focal seizures can get worse if they are not treated, allowing for more serious symptoms to develop.

“A key finding in our study is if focal epilepsy is untreated, it becomes worse over time,” Jacob Pellinen, MD, study lead investigator and assistant professor at the University of Colorado School of Medicine, tells Verywell via email. “Many of the patients in our study who initially experienced nonmotor focal seizures went on to experience convulsions, and many experienced injuries as a result. These injuries could potentially be prevented if the seizures were recognized earlier.” 

What This Means For You

If you or a loved one is experiencing signs and symptoms of focal seizures, call a healthcare professional. If you need to wait for an appointment or referral to an epilepsy specialist, avoid driving to keep yourself and others safe.

Diagnosis and Treatment

It can be difficult to diagnose a seizure disorder. The diagnosis relies on a complete medical history and an accurate account of signs and symptoms. 

If a provider thinks a person could have epilepsy, they usually will need to order certain tests to confirm the diagnosis, including electroencephalography (EEG), computed tomography (CT) scan, magnetic resonance imagining (MRI), and a blood sample.

The Epilepsy Foundation states that the main goal of seizure treatment is “No seizures, no side effects.”

The most common treatment for epilepsy is antiseizure medication, but there are also other options including:

  • Dietary therapy
  • Clinical trials
  • Complementary health approaches
  • Neurostimulation devices
  • Surgery

“One of the great things is, we can treat seizures,” Hogan says. “Focal seizures are treatable, but the biggest obstacle is diagnosis.”

Improving Diagnosis Time for Focal Seizures

New evidence that undiagnosed focal impaired awareness seizures can lead to injuries will hopefully motivate the medical community to find new ways to speed up the time to diagnosis for patients.

Many neurologists, including Pellinen, believe that educating physicians and the general public on early signs and symptoms of focal seizures is critical.

“Focal nonmotor seizures are often overlooked not only by the public but also by primary care providers and emergency care providers,” Pellinen says. “This means that neurologists and epilepsy specialists need to do a better job at educating the public, healthcare trainees, and healthcare professionals. This may go a long way to improve seizure recognition and could help improve the quality of care for this patient population.”

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Pellinen J, Tafuro E, Yang A, Price D, Friedman D, Holmes M. Focal nonmotor versus motor seizures: The impact on diagnostic delay in focal epilepsy. Epilepsia. 16707.

  2. Epilepsy Foundation. Types of seizures.

  3. Epilepsy Foundation. Focal onset impaired awareness seizures (complex partial seizures).

  4. International League Against Epilepsy. Focal onset seizure.

  5. International League Against Epilepsy. Epilepsy imitators.

  6. Epilepsy Foundation. Treating seizures and epilepsy.