epilepsy and the cortex

tonus

rigidity

clonus

tremors/convulsions

tone

tension in the muscle

primary symptom of epilepsy

seizures

causes for seizures

• not all seizures are due to epilepsy:

  • brain damage

  • tumours

  • tbi

  • toxic chemicals

  • fever in children

  • metabolic conditions

epilepsy seizure cause

generated by own brain dysfunction

seizure prevalence rates

• 1-4% of population will have MULTIPLE SEIZURE EPISODES

• 1:20 will have a one-time mild seizure

problems with diagnosing epilepsy

• there are many different types of epileptic seizures of varying complexity

• many different types of epileptic seizures present differently

old classifications of seizures

• grand mal

• petit mal

grand mal seizures

• Loss of consciousness and equilibrium

• Tonic-clonic convulsions

• Resulting HYPOXIA may cause brain damage

• Should put person on side and ensure airway is open

petit mal seizures

• Also known as ABSENCE SEIZURES

• Not associated with convulsions

• A disruption of consciousness associated with a CESSATION of ongoing behaviour

old views concerning seizures

many thought it was possession, but Hippocrates insisted it was a “DISEASE OF THE BRAIN” instead

new classifications of seizures

• focal seizures

• generalised seizures

• unknown

• unclassified

focal seizures

• One part of brain for origin, depolarising uncontrollably

• Defence mechanism that prevents depolarisation from spreading

• Can spread

subtypes of focal seizures

• focal preserved consciousness seizure (fpcs)

  • formerly known as focal simple seizure

• focal impaired consciousness seizure (fics)

• focal-to-bilateral seizure

  • formerly known as secondary generalisation seizure

generalised seizure

• involves the ENTIRE BRAIN

• Comes from the THALAMUS, which is connected to entire cortex

what modern type of seizures are grand mal and petit mal

generalised; generalised

seizure phases

• aura

• seizure

• post-ictal

aura

• sensory warnings before a seizure

  • e.g. tingling, olfactory hallucinations, visual symptoms

• does not always happen, seizure can happen unnanounced

seizure types

• tonic

• clonic

• tonic-clonic

• myotonic

• atonic

post-ictal

• after the attack

• Barely conscious

• Exhausted

• Hard to rouse, don’t make sense, confusion

diagnosis process for epilepsy

• take extensive history

• tests

  • EEG

  • blood work

  • scans

• replicate the seizure

• figure out where in the brain the seizure is

  • Different lobes in brain are differently inclined to generate seizure

• differential

how does one replicate a seizure in children

• sleep deprivation

• lots of sugar

• strobe lights

seizure origin prevalence: temporal lobe

30-50%

seizure origin prevalence: frontal lobe

20-25%

seizure origin prevalence: parietal lobe

6%

seizure origin prevalence: occipital lobe

5%

percentage of fics controllable with medication

35%

percentage of absence seizures controllable with medication

40%

percentage of grand mal tonic-clonic seizures controllable with medication

50%

other treatment for focal seizures

surgery removing the area of the brain causing depolarisation waves

keto and epilepsy

the ketogenic diet can help lessen risk of seizures, but is not foolproof

how many layers of the cortex are there

6

input layer of the cortex

IV

integration layers of the cortex

I, II & III

EEG input and cortex layers

all input is the result of the input and integration layers together

neuronal columns in the cortex

• Each column consists of several laminae.

• Neurons in a given column have similar properties.

  • eg., in the somatosensory cortex, all the neurons within a given column respond to stimulation of the same area of skin

brodmann’s map

• a cytoarchitectonic map based on ORGANISATION, STRUCTURE, and DISTRIBUTION OF CORTICAL CELLS

  • Regions with the same architecture

sensory receptors

• Respond only to a LIMITED STIMULUS RANGE

• EM spectrum for sight

• Certain shapes of molecules

• We need limits, cannot be infinite perceivers

• TRANSDUCTION– receptors transduce energy

  • Vision: light -> chemical energy in photoreceptors -> APs

  • Audition: air-pressure -> mechanical energy -> auditory receptors -> APs