Focal Seizures

posted in: TDEF Blog | 9

By: Nicholas Parekh

What is a seizure?
Seizures are neurological events characterized by sudden surges of electrical activity in
the brain and are common in epileptic patients. Seizures usually last one to two minutes, and
seizures that last for more than five minutes are considered to be a medical emergency. Patients are diagnosed with epilepsy when they have experienced two or more “unprovoked” seizures (i.e. seizures without a clear cause) that are more than 24 hours apart. “Provoked” seizures have non-epilepsy related causes such as sleep deprivation or low blood sugar.

What is a focal seizure?
Focal seizures are the most common type of seizure in people over a year old. Unlike
generalized seizures which affect the entire brain, focal seizures are localized to a specific area of the brain. As a result, they are also referred to as partial seizures. Sometimes, focal seizures
spread to both hemispheres of the brain and become secondary generalized seizures. In these
cases, the focal seizure initially serves as an “aura” or warning of the impending larger seizure.

Focal seizures are classified based on whether the individual maintains consciousness
during the seizure. During a simple partial seizure, the individual remains conscious during the
episode. Conversely, the patient loses consciousness and is unresponsive for the duration of a
complex partial seizure. Simple partial seizures can transform into complex partial seizures, and
here, the patient will also experience an “aura”.

Focal seizures can be further sub-classified based on where they occur in the brain.
Temporal lobe seizures are the most common type of focal seizure. Since the temporal lobe has
roles in both emotion and memory, patients who experience a temporal lobe seizure may report
sudden feelings of anxiety or déjà vu.

The second most common location of focal seizures is the frontal lobe. Interestingly, they
often occur during sleep and have symptoms similar to sleep disorders. Due to the frontal lobe’s
role in motor functions, frontal lobe seizures can result in uncontrolled movements like thrashing and sleepwalking.

Lastly, seizures that originate in the occipital and parietal lobes are the least common,
each only accounting for about 5% of seizures. Since the occipital lobe is responsible for
processing visual input, seizures in this part of the brain may result in visual hallucinations such
as flashing lights. Patients with occipital lobe epilepsy must be cautious because seizures can be triggered by intense visual stimuli like video games or strobe lights. Similar to the occipital lobe, the parietal lobe also has a major role in sensory perception, so parietal lobe seizures may result in numbness or dizziness among other symptoms.

Symptoms
Unlike a generalized tonic-clonic or grand mal seizure which notably results in jerking
and convulsions, focal seizures have much more mild symptoms which are sometimes so mild
the person experiencing the seizure may not even realize it. Common symptoms of a focal
seizure include:

  • Blank staring
  • Confusion or disorientation after the seizure
  • Loss of awareness or responsiveness
  • Loss of memory
  • Hallucinations (sight, smell, taste, touch, or hearing)
  • Repeatedly saying a phrase or word
  • Automatisms (repetitive movements like lip smacking or rubbing one’s hands)
  • Cycling movements as if one was on a bicycle
  • Dizziness
  • Sudden emotions like fear or anger
  • Déjà vu

Diagnosis
Focal seizures can be diagnosed by describing them to a physician. Elucidating the cause
of the seizure itself is more difficult and may require additional testing. An
electroencephalogram (EEG) can be used to monitor for another seizure, but brain electrical
activity may appear normal in between seizures. Magnetic resonance imaging (MRI) or
computerized tomography (CT) scans can be used to locate structural abnormalities in the brain
that may be the source of the seizures.

Other tests may be used to rule out non-epilepsy related causes. For example, a spinal tap
or lumbar puncture procedure involves inserting a needle between the vertebrae of the lower
back to collect cerebrospinal fluid (CSF) and check for an infection.

Treatment
If the cause of the focal seizure is determined to be non-epileptic, then the patient is
treated by directly addressing the cause through dietary change, antibiotics, or other measures. If the patient is diagnosed with epilepsy, then antiepileptic medications are normally prescribed
first to reduce the frequency of seizures.

For patients who are not responsive to these drugs, there are more advanced forms of
treatment available. Vagus nerve stimulation (VNS) involves the connection of electrodes to the
left vagus nerve which originates in the brain. While it will not eliminate the occurrence of
seizures in epileptic patients, it does regulate brain electrical activity to an extent and can reduce
seizure frequency and intensity.

Likewise, responsive neurostimulation involves surgical implantation of a
neurostimulator device in the brain. It functions as a pacemaker in the heart, monitoring for
abnormal electrical activity and delivering electrical pulses to correct it before a seizure occurs.
It has also demonstrated the ability to reduce seizure frequency and intensity.

Lastly, epileptic patients who display no improvement after the previous forms of
treatment may be treated by surgical excision of affected areas of the brain.

Resources

CDC. (n.d.). Types of seizures . Retrieved January 1, 2021, from
https://www.cdc.gov/epilepsy/about/types-of-seizures.htm

Wells, D. (2017, June 1). Complex partial seizures . Healthline.
https://www.healthline.com/health/complex-partial-seizures#symptoms

Harvard Health Publishing. (2017, May). Partial seizures (focal seizures) .
https://www.health.harvard.edu/a_to_z/partial-seizures-focal-seizures-a-to-z

Johns Hopkins Medicine. (n.d.). Focal epilepsy . Retrieved January 1, 2021, from
https://www.hopkinsmedicine.org/health/conditions-and-diseases/epilepsy/focal-epilepsy

Mayo Clinic Staff. (2020, November 17). Vagus nerve stimulation . Mayo Clinic.
https://www.mayoclinic.org/tests-procedures/vagus-nerve-stimulation/about/pac-2038455

MedlinePlus. (n.d.). Partial (focal) seizure . Retrieved January 1, 2021, from
https://medlineplus.gov/ency/article/000697.htm

NYU Langone Health. (n.d.). Types of epilepsy & seizure disorders in adults . Retrieved January
1, 2021, from
https://nyulangone.org/conditions/epilepsy-seizure-disorders-in-adults/types

Stanford Health Care. (n.d.). How is epilepsy diagnosed? Retrieved January 1, 2021, from
https://stanfordhealthcare.org/medical-conditions/brain-and-nerves/epilepsy/diagnosis.ht
ml

UCSF Health. (n.d.). Responsive neurostimulation . Retrieved January 1, 2021, from
https://www.ucsfhealth.org/treatments/responsive-neurostimulation

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