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PARIETAL

Overview

Seizures with ictal onset in the parietal lobe may be difficult to diagnose, especially in children, because of the subjective nature of these seizures. Positive and/or negative sensory features occur. Typically paraesthesia is reported but disorientation, complex visual hallucinations, vertiginous and visual illusions and disturbance of body image (somatic illusion) can occur. Receptive language impairment can occur with dominant hemisphere involvement. Ipsilateral or contralateral rotatory body movements can occur. There is often involvement of other lobes as the seizure spreads.

Subtypes of parietal lobe seizures

  1. Primary sensory area (post-central gyrus)

    Seizures present with contralateral (or rarely ipsilateral or bilateral) sensory aura, most commonly paraesthesias with tingling and/or numbness. There may be prickling, tickling, crawling or electric-shock sensations in the affected body part. The sensory abnormality may spread sequentially along a body part as the seizure spreads on the cortex according to the sensory homunculus (Jacksonian march), when this occurs motor activity in the affected body part commonly follows. Less common sensory aura include pain and thermal perceptions (such as sensations of burning or cold).

  2. Non dominant parietal cortex

    Seizures may be characterized by body image distortions with feelings of movement (e.g. floating) or altered posture (e.g. twisting movement) in a stationary limb. Somatic illusions such as feeling of a body part being enlarged (macrosomatognosia), shrunken (microsomatognosia) or absent (asomatognosia), or elongated (hyperschematica) or shortened (hyposchematica) may also occur. Distal body parts and the tongue are more commonly affected.

  3. Secondary sensory area (parietal upper bank of the sylvian fissure)

    Seizures are characterized by an experiential aura followed by a feeling of inability to move which may spread sequentially through body parts in a Jacksonian march (ictal paralysis), this may be followed by clonic jerking in affected body parts.

  4. Parieto-occipital junction

    Visual illusions including macropsia (objects in a section of the visual field appear larger) or micropsia (objects appear smaller) may occur. Versive eye movements (typically contralateral) or epileptic nystagmus may be seen. If nystagmus is seen, this is typically with the fast component to the side contralateral to the hemisphere of seizure onset with the slow component returning to the ipsilateral side. Eye movements typically occur with retained awareness, and may be accompanied by head or trunk version. Complex visual hallucinations may occur.

  5. Paracentral lobule

    Seizures arising in the non-dominant hemisphere may be characterized by sexual sensations affecting the genitalia. The subsequent phase of the seizure may be accompanied by sexualized behavior.

  6. Dominant parieto-temporal region

    Seizures may be characterized by language impairment with difficulties reading, calculating and writing.

  7. Fronto-parietal operculum

    Seizures are characterized by facial (mouth and tongue) clonic movements (which may be unilateral), laryngeal symptoms, articulation difficulty, swallowing or chewing movements and hyper-salivation. Sensory (e.g. epigastric), experiential (e.g. fear) and autonomic (urogenital, gastrointestinal, cardiovascular or respiratory) features are common. Gustatory hallucinations are particularly common.

    NOTE the terms fronto-parietal opercular, centrotemporal, sylvian and rolandic seizures are synonymous, referring to seizures involving the region around the central sulcus, particularly in the lower central sulcus.

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