• Clinical science

Focal seizures and syndromes

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 anti-epileptic drugs such as lamotrigine (first-line), levetiracetam, or phenytoin.

Etiology

  • Focal seizures can be caused by many factors:
    • Genetic
    • Structural and/or metabolic disturbances:
      • Morphologic changes (e.g., hippocampal sclerosis or tumor growth)
      • Electrolyte imbalances
      • Drug intake
      • Infections
    • Unknown
  • Common causes based on age group:
    • Childhood: perinatal injury to the brain
    • Adolescence: encephalitis and cerebral trauma
    • Middle-aged adults: cerebral tumors
    • Adults of advanced age: vascular encephalopathies and vascular dementia

Focal seizures with genetic cause

Benign epilepsy with centrotemporal spikes

  • 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
  • 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 or an entire side of the body is possible, as is secondary generalization.
  • EEG: centrotemporal spikes or sharp waves
    • Often occurs in bursts
    • Often bilateral, in which case activity in one hemisphere may be independent of the other
  • Prognosis: usually seizures spontaneously resolve by puberty
  • Treatment:

Rare idiopathic forms

  • Benign childhood epilepsy with occipital spikes
    • Classification: early-onset (called Panayiotopoulos type, < 10 years old) or late-onset (Gastaut type)
    • Clinical features:
      • Panayiotopoulos type
        • Vomiting is typical and frequent.
        • Seizures usually occur at night and last for 5 minutes or longer.
      • Gastaut type
        • Visual symptoms are typical.
        • Seizures usually occur during daytime and last for less than 5 minutes.

References:[1]

Focal seizures with structural or metabolic cause

Temporal lobe epilepsy

Frontal lobe epilepsy

  • Etiology: see “Etiology” above
  • Clinical features
    • Usually simple partial seizures featuring various motor symptoms (muscle tension, vocalization, gaze deviation, or head directed towards the unaffected side )
      • May feature autonomic symptoms (enuresis, salivation), impairment of speech, or 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
      • 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)
      • Secondary generalization is possible.
    • Usually no aura and 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., the mouth or a finger
    • Symptoms persist for several days ("continua")
    • Might be considered a focal status epilepticus
  • Treatment: treat the underlying condition

References:[2][3][4][5][6][7][8]

Diagnostics

See seizure disorders learning card.

Treatment

See seizure disorders learning card.