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A focal sensory seizure involves a sensation being experienced at seizure onset, without objective clinical signs of a seizure evident to the observer. Focal sensory seizures can be further described using the following descriptors:

  • Focal somatosensory seizure - characterized by sensory phenomena including tingling, numbness, electric-shock like sensation, pain, sense of movement, or desire to move. These seizures involve the sensorimotor cortex.
  • Focal sensory visual seizure - characterized by elementary visual hallucinations such as flashing or flickering lights/colours, or other shapes, simple patterns, scotomata, or amaurosis. More complex visual hallucinations such as seeing formed images are considered a focal cognitive seizure. Focal sensory visual seizures arise in the occipital lobe.
  • Focal sensory auditory seizure - characterized by elementary auditory phenomena including buzzing, ringing, drumming or single tones. More complex auditory hallucinations such as voices are considered a focal cognitive seizure. Focal sensory auditory seizures involve auditory cortex in the lateral superior temporal lobe.
  • Focal sensory olfactory seizure - characterized by olfactory phenomena - usually an odor, which is often unpleasant. These seizures involve the mesial temporal or orbitofrontal regions.
  • Focal sensory gustatory seizure - characterized by taste phenomena including acidic, bitter, salty, sweet, or metallic tastes. These seizures involve the parietal operculum and the insula.
  • Focal sensory vestibular seizure - characterized by symptoms of dizziness, spinning, vertigo or sense of rotation. These seizures involve the parietal cortex, temporo-parieto-occipital junction or parieto-temporal cortex.
  • Focal sensory seizure with hot-cold sensations - characterized by sensations of feeling hot and then cold.
  • Focal sensory seizure with cephalic sensation - characterized by a sensation in the head such as light-headedness or headache.

NOTE If the focal seizure is not characterized by this feature at the very outset of the seizure, it is not used to classify the seizure, it is instead used as a seizure descriptor, after the seizure is classified according to its onset feature.

NOTE Focal sensory seizures are one type of epileptic 'aura'. An 'aura' is an subjective experience (which may be sensory, emotional, autonomic or cognitive) felt by the individual having a seizure. The 'aura' reflects the initial seizure discharge in the brain. It may be an isolated phenomenon or progress to a focal motor seizure, to a focal impaired awareness seizure or to a focal to bilateral tonic-clonic seizure. An aura is also known as a "warning".

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