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Focal Seizures

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Overview

Previously known as partial seizures, focal seizures affect one hemisphere of the brain to begin with and may spread to both hemispheres and become generalised. 

Unlike generalised seizures (which always involve a loss of consciousness), focal seizures can be described as:

  • Aware – where consciousness is not impaired
  • Impaired awareness – where consciousness is impaired

Focal seizures are roughly classified as:

  • Aware/impaired awareness:
    • Motor-onset
    • Non-motor onset
  • Focal-to-bilateral tonic-clonic

An overview of seizures, epilepsy, classification, epidemiology, risk factors, general management, and implications in pregnancy can be found in Seizures and Epilepsy: An Overview.

Presentation

Motor-onset focal seizures

Motor–onset focal seizures include physical movement may be:

  • Automatisms:
    • Involuntary behaviour (e.g. lip smacking, Jacksonian march)
  • Atonic:
    • Sudden loss of muscle strength and tone
  • Clonic:
    • Involuntary, regular (rhythmic) muscle jerks
  • Epileptic spasms:
    • Sudden, involuntary tightening of a muscle
  • Hyperkinetic:
    • Irregular sequential movement of limb/axial muscles
  • Myoclonic:
    • Involuntary, irregular (non-rhythmic) muscle jerks
  • Tonic:
    • Increased tone (stiffness) of muscles

Non-motor onset focal seizures

Motor–onset focal seizures do not include physical movement may be:

  • Autonomic:
    • Changes in blood pressure, heart rhythm, bowels or bladder, gastric uprising, sweating, going pale, turning red, or drooling
  • Behaviour arrest:
    • Patients ‘freeze’
  • Cognitive:
    • Dream-like feeling, out-of-body feeling
    • Déjà vu – a new experience that somehow feels familiar
    • Jamais vu – a familiar experience that somehow feels new
  • Emotional:
    • Changes in mood/emotion
  • Sensory:
    • Touch, taste, hearing, vision, smell

Localisation

Overview

The presentation of a seizure may help identify which lobe a focal seizure may originate from:

  • Frontal lobe:
    • Brief duration (usually less than 30 seconds), may happen during sleep
    • Head movements
    • Leg movements
    • Todd’s paresis – temporary post-ictal paralysis/weakness
    • Jacksonian march – progresses in a predictable pattern then “marches” proximally:
    • For example, jerking in a finger, then over the whole hand
  • Parietal lobe:
    • Paraesthesia
    • Other sensory disturbances e.g. heat/electrical sensations
  • Temporal lobe:
    • Hallucinations – auditory/olfactory/gustatory
    • Feelings of rising in the stomach
    • Automatisms e.g. lip-smacking
    • Déjà vu
  • Occipital lobe:
    • Floaters and/or flashes
    • Visual field changes

Investigations

  • Blood glucose:
  • Full blood count:
    • Leukocytosis may suggest a central nervous system (CNS) infection
  • Urea and electrolytes (U&Es):
  • ECG:
    • To identify cardiac-related conditions that can mimic seizures
  • Toxicology screen:
    • Considered if illicit substances are suspected
    • Examples are cocaine, amfetamines, and opioids
  • Serum prolactin:
    • Consider if there is doubt that an actual seizure occurred
    • Prolactin is elevated within 10-20 minutes
  • Neuroimaging – ideally an MRI brain:
    • To identify structural abnormalities, intracranial masses etc.
    • A CT may be performed if an MRI is contraindicated
  • Electroencephalogram (EEG):
    • May show epileptiform activity that corresponds with a specific epilepsy syndrome
    • A normal EEG does not rule out epilepsy:
      • Sleep-deprived EEGs or manoeuvres provoking a seizure (e.g. hyperventilation or photic stimulation) may be performed
      • Ambulatory EEG monitoring for up to 48 hours may be considered

Management

Overview

  • 1st-line: carbamazepine or lamotrigine
  • 2nd-line: levetiracetam, oxcarbazepine, or sodium valproate

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