36. Epilepsy - etiology, pathogenesis, clinical manifestations.

Epilepsy – etiology, pathogenesis, and clinical manifestations

Epilepsy is a chronic neurological disorder characterized by recurrent, unprovoked seizures resulting from abnormal, excessive, and synchronous neuronal discharges in the brain.

Etiology (Causes)

1. 1 Genetic (idiopathic epilepsy)

Inherited ion channel mutations ("channelopathies").

Family history of epilepsy.

Examples: Childhood absence epilepsy, juvenile myoclonic epilepsy.

1. 2 Structural causes (symptomatic epilepsy)

Perinatal injuries: hypoxic- ischemic encephalopathy.

Congenital brain malformations.

Traumatic brain injury.

• Brain tumors.
• Cerebrovascular disease: post- stroke epilepsy.
• Infections: encephalitis, neurocysticercosis.
• Neurodegenerative diseases: Alzheimer's disease.

1. 3 Metabolic and systemic causes

• Hypoglycemia, hyponatremia, hypocalcemia.
• Uremia, hepatic encephalopathy.
• Alcohol withdrawal.

1. 4 Unknown (cryptogenic epilepsy)

• No clear structural or metabolic cause found.

Pathogenesis

1. 1 Abnormal neuronal excitability

• Imbalance between excitatory neurotransmission (e.g., glutamate) and inhibitory neurotransmission (e.g., GABA).
• In epilepsy: excess excitation or reduced inhibition leads to hyperexcitability.

1. 2 Synchronous neuronal discharges

• Hyperexcitable neurons fire in synchrony → epileptic focus.
• Activity can remain focal or spread to involve larger brain areas.

1. 3 Paroxysmal depolarization shift

• Characteristic sudden, large depolarization in neurons → leads to rapid repetitive firing.

1. 4 Propagation

• Spread through local cortical connections or distant networks (via commissural fibers ).

Types of seizures (linked to manifestations)

Clinical Manifestations

Focal (partial) seizures

Without impaired awareness (simple focal)

• Motor (e.g., jerking of one limb).
• Sensory (e.g., paresthesia, visual flashes).
• Autonomic (e.g., epigastric rising sensation).

With impaired awareness (complex focal)

• Altered consciousness, automatisms (lip- smacking, fumbling).

Generalized seizures

Absence (petit mal)

• Sudden brief lapse of consciousness ("blank stare"), no postictal confusion.

Tonic- clonic (grand mal)

• Tonic phase: stiffening and fall.
• Clonic phase: rhythmic jerking.
• Postictal phase: confusion, fatigue.

Myoclonic

• Brief, shock- like muscle jerks.

Atonic

• Sudden loss of muscle tone → falls ("drop attacks").

Other possible manifestations

• Aura (sensory or psychic warning symptoms before a focal seizure).
• Secondary generalization: focal seizure progresses to bilateral tonic- clonic.