Focal Seizures

  • 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

LATERALIZING SIGNS

  • In regards to seizure laterality, indicate the following important signs:

Versive Movements

  • 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.

Todd’s Paralysis

  • 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.

Stroke Mimickers

  • 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.

Additional Signs

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.
  • Fencing Posture
    • 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.

LOCALIZATION

  • 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.

Temporal Lobe

  • Indicate that temporal lobe seizures often manifest with sensory auras, automatisms, or speech arrest (or another form of cognitive impairment).
  • Sensory Auras:
    • Epigastric rising
    • Inappropriate fear
    • Olfactory hallucinations
    • Deja Vu
  • Autonomic features
    • Wide variety of sympathomimetic, gastrointestinal, and respiratory symptoms

Frontal Lobe

  • 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).
  • Additional Features:
    • 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…).

Parietal Lobe

  • 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.

Occipital Lobe

  • And finally, indicate that occipital lobe seizures often produce elemental visual phenomena, such as flashing lights or geometric shapes, much like migraine auras.

Insular Cortex

  • Characteristically manifest with symptoms involve the GI system and throat, such as vomiting, hypersalivation, dysarthria or strange thoracoabdominal sensations.

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