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COGNITIVE SEIZURE

An focal cognitive seizure involves an alteration in a cognitive function (which can be a deficit or a positive phenomenon such as forced thought), which occurs at seizure onset. To be classified as a focal cognitive seizure, the change in cognitive function should be specific and out of proportion to other relatively unimpaired aspects of cognition, because all cognition is impaired in a focal impaired awareness seizure. To characterize focal cognitive seizures, specific testing may be required early during the seizure. Focal cognitive seizures can be further described using the following descriptors:

  • Focal cognitive seizure with expressive dysphasia / aphasia - the onset of inability to speak, in an aware patient who knows what they wish to say but cannot express this. This seizure type is to be distinguished from a focal motor seizure with dysarthria/anarthria in which the patient speaks but speech is poorly articulated (a speech motor disorder).
  • Focal cognitive seizure with anomia - there is a specific difficulty naming everyday objects.
  • Focal cognitive seizure with receptive dysphasia / aphasia - the onset of inability to understand language in the absence of general confusion. This seizure type is seen in dominant hemisphere parieto-temporal lobe seizures.
  • Focal cognitive seizure with auditory agnosia - characterized by the inability to recognize or differentiate between sounds/words or relate them to their meaning. For example a person may hear a ringing sound, but may not connect this with the concept that the sound is from a telephone ringing.
  • Focal cognitive seizure with conduction dysphasia / aphasia - the onset of inability to repeat speech that is heard, due to failure to encode phonological information, in the setting of intact auditory comprehension (full understanding of what is heard), and fluent speech production (subject to paraphrasic errors).
  • Focal cognitive seizure with dyslexia/alexia - the seizure onset is associated with inability to read, due to impairment in understanding written words. This seizure type is seen in dominant hemisphere parieto-temporal lobe seizures.
  • Focal cognitive seizure with memory impairment - the onset of inability to retain memory for events occurring during the seizure, while other cognitive functions and awareness are preserved in the seizure.
  • Focal cognitive seizure with deja vu / jamais vu - characterized by memory phenomena such as feelings of familiarity (deja vu) and unfamiliarity (jamais vu).
  • Focal cognitive seizure with hallucination - characterized by the creation of composite perceptions without the presence of external sensory stimuli, these may be visual (e.g. formed images), auditory (e.g. hearing voices) or involve other sensory modalities, without change in awareness. The sensory phenomena may be accompanied by associated emotion or interpretation e.g. a formed visual image may be accompanied by fear, or may be experienced as persecutory or with paranoia (i.e. with unjustified suspicion / mistrust).
  • Focal cognitive seizure with illusion - characterized by an alteration of actual perception involving visual, auditory, somatosensory, olfactory, and/or gustatory phenomena, without change in awareness.
  • Focal cognitive seizure with dissociation - characterized by an experience of being disconnected from, though aware of, self or environment.
  • Focal cognitive seizure with forced thinking - characterized by the presence of intrusive thoughts, ideas or crowding of thoughts occurring at seizure onset. This is a rare seizure type, seen in frontal lobe seizures.
  • Focal cognitive seizure with dyscalculia/acalculia - characterized by difficulty completing or understanding mathematical calculation. This seizure type is seen in dominant hemisphere parieto-temporal lobe seizures.
  • Focal cognitive seizure with dysgraphia/agraphia - characterized by difficulty in writing. This seizure type is seen in dominant hemisphere parieto-temporal lobe seizures.
  • Focal cognitive seizure with left-right confusion - characterized by inability to distinguish right from left, at the onset of the seizure. This seizure type is seen in dominant hemisphere parieto-temporal lobe seizures.
  • Focal cognitive seizure with neglect - characterized by unilateral failure to report or respond/orient to stimuli presented contralaterally. This is seen contralateral to the hemisphere of seizure onset in non dominant hemisphere parietal lobe seizures.

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 cognitive 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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