Seizures and Epilepsy

Study Guide ​

Definitions:


Epileptic seizure: synchronous excessive discharge of neurons in the cerebral cortex, manifesting as a stereotyped disturbance of consciousness, behavior, emotion, motor function, or sensation.

  • Classically with sudden onset, lasting seconds to minutes, and usually ceases spontaneously.

 

Epilepsy:  Chronic tendency for recurrent spontaneous unprovoked seizure.
Status epileptics  A medical emergency with a high mortality rate caused by the state of continuous or recurrent seizures, with failure to regain consciousness between seizures over 30 minutes.

  • Can cause anoxic brain damage.

 

 

Prodrome: Premonitory changes in mood or behavior; these may precede the attack by some hours.
Ictus: The attack or seizure itself.


Postictal period:  The time after the ictus during which the patient may be drowsy, confused and disorientated.

  • May have focal neurological signs (e.g. Todd’s paralysis).

 

Differential Diagnosis: 

Pathophysiology:

 

 

1. Mechanism of seizure initiation and propagation


a. Initiation:High-frequencyburstsofactionpotentialsandhypersynchronization

  •  Long-lasting depolarization of the neuronal membrane due to influx of extracellular (Ca2+)!opening of voltage-dependent sodium (Na+) channels!influx of Na+, and generation of repetitive action potentials!hyperpolarizing mediated by GABA receptors or potassium (K+) channels.

b. Propagation (the process by which a partial seizure spreads):

  • Sufficient activation to recruit neurons!loss of nearby inhibition!spread of seizure activity.

 

2. Epileptogenesis:

a. Transformation of a normal neuronal network into a chronically hyperexcitable one.

 

  • Initial CNS injury (trauma, stroke, or infection) ! months/years! first seizure.

  • Injury starts a process that progressively lowers the seizure threshold in the affected region ! spontaneous seizure occurs.   

References:

  1. Fischer, Conrad. Master The Boards. Print.

  2. Agabegi, Steven S, Elizabeth D Agabegi, and Adam C Ring. Step8Up To Medicine. Philadelphia: Wolters

    Kluwer/Lippincott Williams & Wilkins, 2013. Print.

  3. Le, Tao, Vikas Bhushan, and Herman Singh Bagga. First Aid For The USMLE Step 2 CK. New York: McGrawLHill

    Medical, 2010. Print

  4. Le, Tao et al. First Aid For The® USMLE. Print.

  5. Yogarajah, Mahinda. Neurology. Edinburgh: Mosby/Elsevier, 2014. Print.  

Written by: Abdullah AlAsaad

Reviewed by: Roaa Amer

                         Haifa Al Issa

Web Publisher: Adel Yasky