Seizure

• Denote that a seizure is an acute, transient neurological event (typically less than 5 minutes in duration) caused¬ by abnormal (excessive or synchronous) electrical discharges within the brain.

Epilepsy

• Denote that epilepsy is the syndrome of recurrent, unprovoked seizures.
• As we’ll discuss elsewhere, provoked seizures can occur from conditions like intracranial hemorrhage or metabolic causes; whereas; unprovoked seizures do not have a triggering cause.

Status Epilepticus

• Denote that status epilepticus refers to seizure activity that fails to terminate within the anticipated time period (variably defined as anywhere from 5 – 30 minutes) OR it refers to a series of consecutive seizures without intervening recovery.
• Indicate that status epilepticus has a mortality of 15 – 20%; however, it is the underlying etiology for the seizures that is the major contributor to this poor prognosis.
  • Thus, as clinicians, we should never “give-up” on a patient no matter how long the duration of the status epilepticus, as the seizures can persist for weeks and patients can still have a good outcome if the underlying etiology resolves or is treated.

Common Causes of Provoked Seizures

• Denote that the following entities are considered the most common etiologies of seizures:
  • Stroke
  • Brain tumor
  • Brain injury
  • CNS infection

Most Common Cause of Epilepsy, Worldwide

• Denote that neurocysticercosis (taenia solium) is the most common cause of epilepsy, worldwide.
  • The seizures come from the accumulation of cysts within the brain, which occurs when patients swallow the eggs found in the feces of a person who has an intestinal tapeworm.

GENERALIZED SEIZURES

Semiology

• Define the tonic phase as a tonic as stiffening and define the clonic phase as rhythmic jerking.

Mimicker

• Indicate that a key mimicker of tonic-clonic seizure is convulsive syncope, which are convulsions brought on by syncope, a loss of adequate cerebral perfusion, rather than by abnormal electrical activity in the brain.
  • Bear in mind that one of the most common mimickers of generalized seizures, and most seizure types, is actually non-epileptic spells (aka psychogenic seizures).

Syndromes

• Indicate that generalized tonic-clonic seizures can occur in a wide-variety of epilepsy syndromes.

Detailed Semiology

• To best understand the clinical semiology of a tonic-clonic seizure, let’s diagram what happens to a person at each phase of the seizure.
  • We’ll include the corresponding EEG (electroencephalogram), which can be illuminating, at the end.

Pre-ictal

• Note that there is often a pre-ictal sensory prodrome that can last minutes to hours.
  • The ictal phase refers to the seizure, itself: the event.

Tonic Phase

• Show that there is tonic stiffening: show that the back and neck are arched. The patient is lying down because there is a loss of consciousness.

Clonic Phase

• Show that it’s characterized by rhythmic jerking (convulsions) of the face, arms, and legs.

Apnea

• During the ictal phase, there is often apnea with frothing at the mouth, choking sounds, and cyanosis (a blue appearance to the skin), which can mimic a cardiac arrest.

Post-ictal Relaxation

• Then, show that after the event, post-ictal, there is post-ictal relaxation, which involves a stupor with possible bladder or bowel incontinence and deep, slow respirations.

EEG Correlation

• See: Tonic-Clonic Seizure
• Now, let’s address the EEG rhythm, which even if we don’t read EEG, can help reinforce our understanding of the seizure presentation, itself.
• Draw a small strip of EEG – we’ll just show a couple of tracings; normally, there would be at least 18 tracings to a page.
• For reference, show the region between the vertical lines is one second.
• The number of wave cycles within that one second is the frequency, which is measured in Hertz (Hz).
  • A single wave cycle in one second would be 1 Hz.

Tonic Phase

• Indicate that at the initiation of the seizure, during the tonic phase, the EEG rhythm is a 10 Hz tonic (fast frequency), low amplitude waveform.

Clonic Phase

• Now, indicate that during the clonic phase, the corresponding EEG rhythm is 4 Hz (slower frequency) spike-and-wave activity.

Post-ictal Slowing

• Finally, indicate that after the event, there is post-ictal slowing, with only a few wave cycles per second.

MYOCLONIC – JUVENILE MYOCLONIC EPILEPSY (JME)

Semiology

• Next, indicate that myoclonic seizures, manifest with brief, shock-like muscle jerks.

Mimicker

• Indicate that they are often mistaken for a movement disorder.

Epilepsy

• Write that myoclonic seizures are an important component of juvenile myoclonic epilepsy (JME), which begins in adolescence (12 – 18 years old).
  • It is one of the photosensitive epilepsies; seizures can be triggered by flashing or flickering lights.

Detailed Semiology

• For juvenile, myoclonic epilepsy, draw a bed and a sunrise, because the events characteristically cluster upon awakening in the morning.
• And draw a bolt of lightning because the jerks are described as “lightning-like”.
• Draw our person lying in bed (because they tend to occur in the morning).
• Show that they manifest with symmetric, irregular, shock-like, jerks of the shoulders and arms, most notably, which can cause the person to drop items, but can also affect the legs, which can cause falls.

EEG Correlation

• Indicate that the EEG demonstrates polyspikes, which correlate with the myoclonic jerks, and characteristic disorganized, 4 – 5 Hz polyspike and wave discharges.
  • See: Polyspike-and-Wave Complexes
  • See: Status Myoclonus
• As mentioned, these discharges have a strong photoparoxysmal response, so flashing lights are used during EEG to elicit these discharges.

ATONIC – LENNOX-GASTAUT

Semiology

• Next, indicate that atonic seizures cause as loss of tone (drop attacks).
• They manifest with brief loss of muscle tone in the postural muscles or head.

Mimicker

• Indicate that they can be hard to distinguish from syncope, which also involves a sudden loss of tone.

Epilepsy

• Write that they are an important feature of Lennox-Gastaut syndrome, which involves multiple seizure types, including atonic seizures and cognitive dysfunction. It peaks at ~ 4 years of age.

EEG Correlate

• We’ll skip showing the EEG correlate of Lennox-Gastaut, but for reference, there are slow (1.5 – 2 Hz ) spike-and-wave discharges.

ABSENCE – CHILDHOOD ABSENCE EPILEPSY (CAE)

• Finally, for the major non-motor, generalized seizure, we’ll address absence seizures.

Semiology

• Indicate that absence seizures (aka petit mal seizures) manifest with a blank stare; patients appear to be daydreaming or zoning out.
• These patients may exhibit rhythmic facial movements or motor automatisms.
• Notably, there is no postictal confusion; patients can pick right back up where they left off with an activity.

Mimicker

• Indicate that it is essential to distinguish absence seizures from an attentional disorder, as these patients can be mistakenly diagnosed with a learning disability.

Epilepsy

• Indicate that they are the major seizure manifestation in childhood absence epilepsy (CAE), which typically occurs between 4 to 8 years of age, affects girls more than boys, and can involve 100s of seizures in a day.
• Show that children with absence seizure appear to be “daydreaming” or “staring off” in school.

EEG Correlation

• Indicate that the EEG demonstrates runs of well-organized 3 Hz generalized high-voltage rhythmic spike-and-wave discharges.
  • See: 3 Hz Generalized Spike-Wave Discharges

JUVENILE ABSENCE EPILEPSY (JAE)

• For reference, juvenile absence epilepsy (JAE) is another generalized epilepsy syndrome, which we can think of (albeit a simplification) as a mixture of childhood absence epilepsy and juvenile myoclonic epilepsy:
  • it occurs at 9 – 13 years of age
  • it involves absence and myoclonic seizures that tend to occur shortly after awakening.