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.
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.
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:
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.
Define the tonic phase as a tonic as stiffening and define the clonic phase as rhythmic jerking.
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).
Indicate that generalized tonic-clonic seizures can occur in a wide-variety of epilepsy syndromes.
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.
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.
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.
Show that it’s characterized by rhythmic jerking (convulsions) of the face, arms, and legs.
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.
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.
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.
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.
Now, indicate that during the clonic phase, the corresponding EEG rhythm is 4 Hz (slower frequency) spike-and-wave activity.
Finally, indicate that after the event, there is post-ictal slowing, with only a few wave cycles per second.
MYOCLONIC – JUVENILE MYOCLONIC EPILEPSY (JME)
Next, indicate that myoclonic seizures, manifest with brief, shock-like muscle jerks.
Indicate that they are often mistaken for a movement disorder.
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.
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.
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
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.
Indicate that they can be hard to distinguish from syncope, which also involves a sudden loss of tone.
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.
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.
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.
Indicate that it is essential to distinguish absence seizures from an attentional disorder, as these patients can be mistakenly diagnosed with a learning disability.
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.
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.
Note that the primary focal epilepsy syndrome is temporal lobe epilepsy, which is why in our diagram we show the seizure emanating from the medial temporal lobe, but focal seizures can occur from any cerebral lobe.
To localize the origination of the seizure, we can use both lateralizing and localizing signs.
On EEG, we look for focal epileptiform discharges.
See: Focal Epileptiform Discharge
In regards to seizure laterality, indicate the following important signs:
Indicate versive motor movements, which refers to contralateral turn of the head and/or eyes (away from the seizure).
Draw a brain and show a seizure emanating from the right hemisphere.
Then draw a pair of eyes and show that they exhibit forced eye deviation to the left: the side opposite (contralateral) to the side of seizure.
Next, indicate that Todd’s paralysis refers to a post-ictal weakness in the side of the body opposite to the seizure.
Consider the post-itcal slowing we drew following a tonic-clonic seizure: the brain is slow and suppressed, so naturally the corresponding side of the body is limp and weak.
Naturally, then, these signs can be important mimickers of stroke. In stroke:
The eyes can drift toward the side of the stroke: they look at the healthy side of the body (this is the opposite direction from in seizure wherein they look away from the seizure).
There is weakness on the side opposite of the stroke, similar to a Todd’s paralysis.
Some commonly discussed, albeit less reliable lateralizing signs, include the:
Figure 4 Sign
The arm contralateral to the seizure is extended at the elbow with the wrist in flexion and the fist is clenched.
The ipsilateral limb is in elbow flexion.
The arm contralateral to the seizure is raised and semi-extended above the head, as if holding a fencing foil.
The head is turned toward the raised arm while the ipsilateral arm is semi-flexed at at the patient’s side.
Now, in regards to lobar localization, let’s address a few common seizure localities (note that seizures emanate supratentorially, above the brainstem and cerebellum).
Draw a medial face of a cerebral hemisphere; we do this, because as mentioned, the most common locality for focal seizures is the medial temporal lobe.
Divide it into the temporal, frontal, parietal, and occipital lobes.
Indicate that temporal lobe seizures often manifest with sensory auras, automatisms, or speech arrest (or another form of cognitive impairment).
Wide variety of sympathomimetic, gastrointestinal, and respiratory symptoms
Indicate that frontal lobe seizures tend to be stereotyped and nocturnal. They are easily confused for psychogenic seizures or a movement disorder (especially because there is often NO loss of awareness or postictal phase).
Manifestations of frontal lobe seizures range from emotionally-driven, fearful hallucinations to motor activity: tonic-clonic movements and the more complicated positions described previously (figure 4 sign, fencing posturing, etc…).
Indicate that parietal lobe seizures tend to cause somatosensory auras, which we could predict given the role of the parietal lobe in sensory processing.
Note, however, that parietal lobe seizures are notoriously poorly localizing and they will commonly propagate to more regions with more readily obvious manifestations, such as the frontal lobe or the occipital lobe, before they are recognized.
And finally, indicate that occipital lobe seizures often produce elemental visual phenomena, such as flashing lights or geometric shapes, much like migraine auras.
Characteristically manifest with symptoms involve the GI system and throat, such as vomiting, hypersalivation, dysarthria or strange thoracoabdominal sensations.