Epilepsy - B. Pharma 2nd Semester Pathophysiology notes pdf

Epilepsy

Contents

•       Epilepsy

•       Classification

•       Status epilepticus

•       Pathophysiology

Objectives  

At the end of PDF Notes, student will be able to

•         Define epilepsy

•         Define status epilepticus

•         Classify epilepsy

•        Describe the pathogenesis of epilepsy

Epilepsy

•       Chronic brain disease of diverse etiology

•       Characterized by recurrent paroxysmal episodes of uncontrolled excitation of brain neurons

•        Manifesting as brief episodes (seizures) of loss of consciousness, with or without characteristic body movements (convulsions)

Status epilepticus (SE)

Continuous convulsion lasting longer than 30 minutes OR Occurrence of serial convulsions between which there is no return of consciousness

Pathophysiology of Epilepsy

•       Normally, a balance between excitatory and inhibitory factors - proper functioning of a healthy human brain

•       Reduction of inhibitory synaptic activity or enhancement of excitatory synaptic activity -trigger a seizure

•        NTs mediating the bulk of synaptic transmission in the mammalian brain are amino acids

•       GABA - principal inhibitory

•       Glutamate - excitatory neurotransmitters

•       Repeated epileptic discharge can cause neuronal death (excitotoxicity).

•        A relative deficiency of inhibitory neurotransmitters such as GABA

•        An increase in excitatory neurotransmitters such as glutamate would promote abnormal neuronal activity

Clinical manifestations of Epilepsy

•       Depend on the location of the focus and the pathways involved in its spread

•       ‘Generalised’ - initial activation of both hemispheres of the brain

•       ‘Partial’ or ‘Focal’ -  discharge starts in a localised area of the brain

Grandmal seizure

•       Generalized convulsion, also called the grand-mal seizure.

•       Patient loses consciousness and usually collapses.

•       Followed by generalized body stiffening (called the "tonic" phase of the seizure) for 30 to 60 seconds,

•       violent jerking (the "clonic" phase) for 30 to 60 seconds,

•       patient goes into a deep sleep.

•       During grand-mal seizures, injuries and accidents may occur,

•       Tongue biting and urinary incontinence

Absence seizures

•       Short loss of consciousness (just a few seconds) with few or no symptoms

•       Patient, most often a child

•       Seizures begin and end abruptly

•       Patients are usually not aware that they are having a seizure, except that they may be aware of "losing time."

Myoclonic seizures

•       Consist of sporadic jerks

•       Usually on both sides of the body

•       Patients sometimes describe the jerks as brief electrical shocks

•        When violent, these seizures may result in dropping or involuntarily throwing objects

Clonic seizures

·         Repetitive

·         Rhythmic jerks

·         Involve both sides of the body at the same time

Tonic seizures

Tonic seizures are characterized by stiffening of the muscles.

Atonic seizures

•       Sudden and general loss of muscle tone

•       Particularly in the arms and legs

•       Often results in a fall

Simple partial seizures

•       Key feature is preservation of consciousness

•        A sudden depolarization within a group of neurons called Paroxysmal depolarizing shift (pds)

•       Lasts for 200 ms occurs in case of patients with partial seizures.

•       This results in generation of an abnormally rapid train of action potentials

Complex partial seizure

•       Impaired consciousness lasting 30 seconds to 2 minutes

•       Often associated with purposeless movements such as lip smacking or hand wringing

•       Associated with amnesia

Secondarily generalized seizure

Ø  Partial seizures may get generalized

Ø  spreading along diffuse connections to involve both cerebral hemispheres

Ø   This seizure spread occurs through several pathways

ü   U FIBRES connect various regions of the cortex.

ü   CORPUS CALLOSUM allows for spread between hemispheres.

ü   THALAMOCORTICAL PROJECTIONS provide a pathway for diffused synchronized spread throughout the brain

Summary

•       Epilepsy is characterized by recurrent paroxysmal episodes of uncontrolled excitation of brain neurons

•        Manifesting as brief episodes (seizures) of loss of consciousness, with or without characteristic body movements (convulsions)

•       Continuous convulsion lasting longer than 30 minutes is status epilepticus