Epilepsy, Types of Seizure, and EEG

Key Points

• Epilepsy is a neurological condition with recurrent seizures caused by abnormal electrical activity in the brain. Affects over 600,000 in the UK.
• Pathophysiology involves an imbalance between excitatory (glutamatergic) and inhibitory (GABAergic) neuronal signaling, lowering neurotransmission threshold.
• Risk factors include:
  • Head injury, stroke, brain tumors, neurodegenerative diseases
  • Genetic syndromes: tuberous sclerosis, Dravet syndrome
  • Metabolic/electrolyte imbalances: hyponatremia, hypoglycemia
  • CNS infection: encephalitis, meningitis
  • Alcohol withdrawal
• Seizure Classification:
  • Focal onset: aware or impaired awareness, motor or nonmotor
  • Generalized onset: motor (e.g., tonic-clonic) or nonmotor (absence)
  • Unknown onset: motor or nonmotor
• Clinical Features: Seizures with prodrome, stereotyped semiology, post-ictal confusion, Todd’s paresis.
• Differential Diagnoses: Dissociative seizures, vasovagal episodes.
• Investigations: Bedside (vital signs, glucose), lab (FBC, U&Es, bone profile, VBG), imaging (CT/MRI), electrical (EEG, video telemetry).
• Diagnosis: Requires two or more unprovoked seizures or epilepsy syndrome diagnosis.
• Management:
  • Medical: Anti-seizure medications, rescue medications
  • Dietary: Ketogenic diet for rare epilepsy subtypes
  • Surgical: Resection, lobectomy, hemispherectomy, corpus callosotomy.
• Complications: Accidental injury, status epilepticus, SUDEP.

Introduction

• Epilepsy features recurrent epileptic seizures.
• Seizures result from aberrant electrical activity spreading through the brain, manifesting with motor or sensory symptoms, often with reduced consciousness.
• Affects over 600,000 people in the UK.

Aetiology

Pathophysiology

• Imbalance between excitatory and inhibitory neuronal signaling reduces neurotransmission threshold.

Anatomy

• Clinical signs vary with seizure focus and spread.
• Frontal lobe: abnormal movements, vocalisation
• Temporal lobe: abnormal sensations
• Occipital lobe: visual disturbances

Risk Factors

Structural Abnormalities

• Head injury, stroke, tumors, neurodegenerative diseases
• Genetic syndromes: tuberous sclerosis, neurofibromatosis

Neurochemical Imbalance

• Genetic disorders affecting neuronal conduction can cause epilepsy.

Seizure Threshold

• Lowered by metabolic/electrolyte abnormalities, CNS infection, alcohol withdrawal
• Environmental triggers like flashing lights are rare.

Clinical Features

Classification of Epileptic Seizures

• Focal seizures: Specific focus, may retain or impair awareness, motor or nonmotor onset
• Generalized seizures: Affect both hemispheres, often motor
• Absence seizures: Brief, unresponsive, no muscle tone loss, mostly in children

History

• Collateral seizure history provides prodrome, seizure, and post-ictal period details.

Differential Diagnoses

• Dissociative Seizures: Often feature long duration, quick recovery, retained awareness.
• Vasovagal Episodes: Dizziness followed by loss of consciousness, brief jerking.

Investigations

Bedside

• Vital signs, capillary blood glucose for hypoglycemia.

Laboratory

• FBC, U&Es, bone profile, VBG for reversible causes.

Imaging

• CT/MRI to identify underlying factors.

Electrical and Visual Recordings

• EEG, video telemetry, patient videos for seizure characterization.

Diagnosis

• Diagnosis of epilepsy requires two unprovoked seizures or diagnosis of epilepsy syndrome.

Management

Medical Management

• Anti-seizure medications target sodium channels or GABAergic transmission.
• Rescue medications for non-terminating seizures.

Ketogenic Diet

• High-fat, low-carb diet alters brain metabolism to reduce seizures in rare types.

Surgical Management

• Surgical interventions for medication-refractory seizures.

Complications

• Accidental injury: Bruising, lacerations, fractures, burns.
• Status Epilepticus: Seizure >5 minutes; emergency intervention may be needed.
• SUDEP: Unexpected death, often unwitnessed.

References

1. Epilepsy Research and Statistics
2. International League Against Epilepsy Classification