Focal seizures and syndromes

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.

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

• Childhood: perinatal injury to the brain
• Adolescence
  • Encephalitis
  • Cerebral trauma
• Middle-aged adults: cerebral tumors
• Adults of advanced age
  • Vascular encephalopathies
  • Vascular dementia

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

• Clinical features: short seizures, usually during non-REM sleep

Familial lateral temporal lobe epilepsy

• Clinical features
  • Auditory hallucinations
  • Focal seizures that generalize secondarily

Temporal lobe epilepsy

• Epidemiology: most common form of epilepsy
  • ∼ 40% of all epilepsy cases
  • ∼ 70% of focal epilepsy cases
• Etiology
  • Hippocampal sclerosis: found in approx. 70% of patients suffering from temporal lobe epilepsy that is resistant to pharmacotherapy
  • Encephalitis (e.g., herpes simplex encephalitis)
  • Developmental disorders
  • Neurodegenerative disorders
  • Tumors
• Clinical features: Seizures commonly occur in clusters, last approx. 30 seconds to 2 minutes, and follow a specific sequence. ^[1]
  1. Aura
     • Visceral, olfactory, or auditory
     • Feelings of familiarity or unfamiliarity and “dreamy states”
  2. Focal seizure with impaired awareness (complex partial seizure)
     • Motor symptoms
       • Typically oral alimentary automatisms (e.g., lip-smacking)
       • Fidgeting (e.g., with clothing)
       • Stretching of the body
       • Walking in place
     • Autonomic symptoms
       • Tachycardia
       • Urge to void the bladder
       • Mydriasis
       • Sweating, salivating
     • Altered mental status
       • Children appear absent-minded (e.g., staring ahead, unresponsive when spoken to)
       • No loss of consciousness
     • Less frequently: loss or change in the sense of taste or smell, aphasia
     • Focal seizures may progress to generalized seizures.
  3. Postictal phase
     • Confusion and tiredness (common)
     • Transient epileptic amnesia (rare): anterograde or retrograde amnesia immediately preceding or following a seizure
• Diagnosis: EEG shows temporal lobe spikes
• Treatment
  • Pharmacotherapy: e.g., lamotrigine, levetiracetam
  • Surgical treatment: in case of medication resistance
• Prognosis: unfavorable (only 40% of patients on pharmacotherapy remain asymptomatic)

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

• Epidemiology: 5% of cases of focal epilepsy
• Etiology: See "Etiology of focal seizures and syndromes" above.
• Clinical features
  • Simple partial seizures, characterized by:
    • Sensory symptoms (e.g., paresthesia, pains)
    • Dyslexia
    • Sensory aphasia
    • Possible Jacksonian march
  • Transition to temporal or frontal lobe seizures (featuring the respective symptoms) may occur.

Occipital lobe epilepsy

• Epidemiology: rare
• Etiology: See "Etiology of focal seizures and syndromes" above.
• Clinical features
  • Simple partial seizures, characterized by:
    • Visual hallucinations
    • Gaze deviation
    • Cortical blindness
  • Transition to temporal or frontal lobe seizures (featuring the respective symptoms) is possible.

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

See “Diagnosis of seizure disorders.”

See “Treatment of epileptic seizures.”