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Focal seizures and syndromes

Last updated: December 30, 2020

Summary

Focal (or partial) seizures are an abnormal activation of neurons confined to one cerebral hemisphere, and are best described according to whether or not consciousness and/or awareness are impaired. In contrast, generalized seizures are characterized by abnormal neuronal activity that quickly spreads to both hemispheres of the brain. Seizures can be caused by genetic abnormalities, structural abnormalities, metabolic disturbances, tumors, or infection. Symptoms depend on the location of the ictal event within the brain and may include clonic movements, as well as sensory and psychiatric symptoms. Focal seizures may involve altered levels of consciousness (complex partial seizures) or evolve to secondarily generalized seizures. Temporal lobe epilepsy is the most common type of focal seizure. It frequently arises from hippocampal sclerosis, but may also be caused by malignancies or infections. Diagnosis of focal seizures begins with electroencephalography and neuroimaging. If an infectious or a metabolic etiology is suspected, laboratory tests can also be helpful. Focal seizures secondary to underlying non-neurologic pathologies (e.g., infection or metabolic disturbances) are treated by correcting the underlying abnormality. Seizures of unknown etiology or from a neurological defect are managed with antiepileptic drugs such as lamotrigine (first-line), levetiracetam, or phenytoin.

Etiology

Common causes

  • Genetic
  • Structural and/or metabolic disturbances:
    • Morphologic changes (e.g., hippocampal sclerosis, tumor growth)
    • Electrolyte imbalances
    • Drug intake
    • Infections

Based on age group

Focal seizures with genetic cause

Benign epilepsy with centrotemporal spikes (BECTS; Rolandic epilepsy)

  • Definition: a benign form of epilepsy in children, featuring centrotemporal spikes
  • Epidemiology
    • Most common form of epilepsy in children (∼ 10–20% of cases)
    • Peak incidence: 7–9 years of age
  • Clinical features
    • Usually occurs during sleep
    • Facial twitching or numbness, hypersalivation, and speech arrest (during and frequently even after the event)
    • Involvement of an arm/entire side of the body is possible, as is secondary generalization.
  • Diagnostics: EEG shows centrotemporal spikes or sharp waves
    • Often in bursts and bilateral, in which case activity in one hemisphere may be independent of the other
    • Biphasic waves of approx. 70–100 ms (spikes) or up to 200 ms (sharp waves)
    • Horizontal dipole
      • Maximum positivity in the frontal region
      • Maximum negativity towards the centrotemporal region
  • Treatment: anticonvulsants (e.g., valproate) are only recommended in cases of high seizure frequency or severity
  • Prognosis: Seizures will usually have resolved spontaneously by puberty.

Rare idiopathic forms

Benign childhood epilepsy with occipital spikes

  • Classification
    • Early-onset (Panayiotopoulos type): < 10 years of age
    • Late-onset (Gastaut type)
  • Clinical features
    • Panayiotopoulos type
      • Vomiting is typical and frequent.
      • Seizures usually occur at night and last for ≥ 5 minutes
    • Gastaut type
      • Visual symptoms are typical.
      • Seizures usually occur during the daytime and last for less than 5 minutes.

Autosomal dominant nocturnal frontal lobe epilepsy

Familial lateral temporal lobe epilepsy

Focal seizures with structural or metabolic cause

Temporal lobe epilepsy

Frontal lobe epilepsy

  • Etiology: See “Etiology of focal seizures and syndromes” above.
  • Clinical features
    • Usually simple partial seizures featuring:
      • Motor symptoms
        • Muscle tension
        • Vocalization
        • Gaze deviation
        • Head directed towards the unaffected side
      • Autonomic symptoms (enuresis, salivation)
      • Impairment of speech
      • Attention deficits (staring spells that may appear similar to absence seizures)
      • Jacksonian march
        • Spreading of paresthesia or uncontrolled motor activity from one part of the body to adjacent areas, usually distally to proximally
        • Results from seizure activity that progresses to the motor cortex
        • March may progress to involve the entire limbs or the entire side of the body.
      • Todd's paralysis: sustained paralysis of the affected limb/area after the seizure
      • Usually a series of short seizures (≤ 30 s) occurring during sleep (which often wake the patient)
    • No aura
    • No postictal period of confusion

Focal seizures that feature Jacksonian marches are termed Jacksonian seizures, regardless of the origin of the seizures.

Parietal lobe epilepsy

Occipital lobe epilepsy

In general, patients suffering from partial seizures of structural or metabolic origin should be treated with antiepileptic drugs (e.g., lamotrigine or levetiracetam).

Epilepsia partialis continua

  • Epidemiology: rare
  • Etiology: unspecific; current or past damage to the cortex (e.g., scar tissue, encephalitis, tumors)
  • Clinical features
    • Clonic muscle activity of a particular region of the body (partialis), e.g., mouth, finger
    • Symptoms persist for several days (continua).
    • Might be considered a focal status epilepticus
  • Treatment: treat the underlying condition

Diagnostics

See “Diagnosis of seizure disorders.”

Treatment

See “Treatment of epileptic seizures.”

References

  1. Luef GJ. Epilepsy and sexuality. Seizure. 2008; 17 (2): p.127-130. doi: 10.1016/j.seizure.2007.11.009 . | Open in Read by QxMD