EEG: definition
• It is record of variations in brain potential
• It is record of electrical activity of brain/neurons in different phases e.g. during sleep, wakefulness and epilepsy.
E.E.G
• Carried out by placing electrodes on surface of scalp.
• Sometimes placed directly on surface of cerebral cortex, e.g., during neurosurgical operations or in experimental animals.
• Such a record is called Electro- Corticogram (ECOG)
E.E.G
• E.E.G was 1st recorded by a German Psychiatrist Hans Berger.
• There are 2 methods for EEG recording• Recording of EEG can be unipolar or bipolar.• In unipolar EEG, active electrode is placed on
surface of scalp, while inactive or indifferent is placed at a distant point, like tip of 7th cervical vertebra.
• In bipolar EEG, both electrodes are active & placed on surface of scalp.
E.E.G
• In routine E.E.G, 20 electrodes are placed on scalp at different points to record EEG.
• In normal EEG, 4 types of waves can be seen: alpha, beta, theta & delta, in different phases.
• Character of each wave is described as
• 1- its intensity/voltage 2- frequency
Alpha waves: Waves of quiet wakefulness / waves of inattentiveness:
• Frequency: 8-13 / sec
• Voltage: 50 micro-volts
• Relaxed awareness
These are recorded when a person is awake but mentally relaxed & inattentive, e.g., lying comfortably in a quiet room, eyes are closed & person is mentally relaxed & inattentive.
Alpha waves: Waves of quiet wakefulness / waves of inattentiveness:
• When a person opens eyes or the brain becomes active by thinking process or solving a problem, alpha waves disappear.
• Frequency of alpha waves decreases by decreased body temperature, decreased glucocorticoid secretion, hypoglycemia & increase in pCO2.
(due to cold temp. / empty stomach / during suffocation, one cant relax)
Alpha waves: Waves of quiet wakefulness / waves of inattentiveness:
• Best recorded from parietal & occipital regions.
• Thalamo-cortical connections are important for it.
Beta waves: waves of alertness / wakefulness / desynchronized waves
• Frequency: 14-80 cycles/sec
• Amplitude / voltage: 20 microvolts.
Awareness with concentrated attention
• Recorded when brain is highly active.
• Best recorded from parietal & frontal regions.
• Recorded during REM sleep.
• Appear on eye opening
Theta waves:
• Frequency: 4-7 / sec• Voltage: 10 microvolts
• Best recorded from parietal & temporal regions.• Recorded during light sleep.• Recorded in adults during states of frustration &
disappointment.• In children normally recorded in awake E.E.G.• Also recorded in brain disorders like Grand Mal
Epilepsy. In degenerative brain disorders.
Delta Waves:
• Very slow waves.
• Frequency: 0.5 - 3 / sec
• Voltage: 100 microvolts
• Recorded in deep & restful sleep.
• Also recorded in coma, general anesthesia & in epilepsy. In organic brain disorders.
Physiological basis of E.E.G:
• Electrical activity recorded in EEG, is mainly from superficial layers of cerebral cortex which have number of dendrites on which many nerve terminals synapse.
• Some terminals are excitatory (EPSP is produced), some are inhibitory (IPSP is produced).
• Electrical activity recorded in EEG, is summation of EPSPs & IPSPs
Physiological basis of E.E.G:
• Amplitude of waves in EEG depends on how much the waves are synchronized / coordinated.
• If waves are synchronized, there is increased amplitude.
• If desynchronized, there are deflections in different directions & these neutralize each other, resulting into a small amplitude like in beta waves.
• During each wave there is synchronous discharge/ activation of neurons.
Physiological basis of E.E.G:
• Thalamo-cortical connections are important, mainly in recording of alpha waves.
• If these fibers are cut, alpha waves disappear & delta waves appear.
Clinical use of E.E.G:
• EEG reflects functional state of brain.
• Recorded as an investigation in patients .
• Also recorded for research purpose.
• Recorded for many hours in epilepsy cases.
• EEG machines are now computerized & there is automatic analysis of EEG.
Clinical use of E.E.G:
• Helps to diagnose SOL (Space occupying lesion) in skull, which may be infective, neoplastic, traumatic or vascular.
• It helps in diagnosis of epilepsy & its types.
• It helps in diagnosis of psychopathic disorders.
Clinical use of E.E.G:
• In Grand Mal epilepsy, there may be theta or delta waves (high voltage waves) in EEG.
• In Petit Mal epilepsy, there is spike & dome pattern.
• In Psychomotor epilepsy, mainly delta waves are seen.
Epilepsy• Epilepsy (also called “seizures”) is
characterized by uncontrolled excessive activity of either part or all of CNS.
• Attack occurs when basal level of excitability of neurons crosses threshold.
• Epilepsy can be classified into three major types:
• grand mal epilepsy, petit mal epilepsy, and focal epilepsy.
Grand Mal Epilepsy/Generalized epilepsy
• Grand mal epilepsy is characterized by extreme neuronal discharges in all areas of the brain cerebral cortex, deep parts of cerebrum, and brain stem.
• Discharges transmitted into the spinal cord sometimes cause generalized tonic seizures of the entire body, followed by alternating tonic and spasmodic muscle contractions called tonic-clonic seizures
• person bites his tongue
• difficulty in breathing & cyanosis
• urination and defecation can occur
• grand mal seizure lasts from a few sec to 3 to 4 min. It is also characterized by post seizure depression of the entire nervous system.
Factors which produce epilepsy
• Strong emotional stimuli
• Hyperventilation or alkalosis
• Effects of some drugs e.g. phenylenetetrazole
• High fever
• Loud noises
• Bright light
• Traumatic lesion in any part of brain
Petit mal/Partial epilepsy
• Person suddenly becomes unconscious.
• Convulsions do not occur
• Muscles of face show twitching & blinking of eyes
• Afterwards person become normal
• It occurs in late childhood
• Absence syndrome/ absence epilepsy
• Excitatory thalamocortical neurons
Focal Epilepsy
• It involves only localized area of brain (cerebral cortex or deep parts of cerebrum)
• The abnormality starts from a particular area and spreads to the adjacent area.
Focal Epilepsy
• Two types
• 1- Jacksonian epilepsy
• 2- Psychomotor epilepsy
• Causes
• 1- scar tissue in brain, 2- Tumor, 3- some destroyed part of brain tissue
• In Jacks, as the wave of excitation spreads over motor cortex, it causes progressive march
• Of muscle contrations throughout the opposite side of body.
• Beginning in mouth region and marching progressively downwards to legs.
Psychomotor epilepsy
• It is characterized by emotional outburst such as abnormal rage,anxiety,fear or discomfort.
• There is amnesia or confused mental state for some period.
• The cause, are the abnormalities in temporal lobe & tumor in hypothalamus and limbic system.
SLEEP
• “Period of inactivity during which there is unconsciousness from which person can be aroused by sensory & other stimuli”.
• Unconsciousness during surgical anesthesia, epilepsy & coma should not be considered as sleep.
Lack of SLEEP
• Sleep is essential for normal life. • It restores a balance between different parts of
nervous system.
If a person is not allowed to sleep for 2-3 days, certain effects are seen:
• Loss of concentration• Slow thought making• Loss of memory• irritability
Lack of SLEEP
If insomnia is further prolonged, person may develop:
• Dysarthria (defect of speech)
• Tremors
• Abnormal gait
Requirement of SLEEP
Varies with age:
• Infants: 20-24 hrs
• Young children: 12 hrs
• Young adults: 7-9 hrs
• Old age: 5-7 hrs
Relationship of SLEEP with ANS:
During sleep, generally there is
• Sympathetic inhibition &
• Parasympathetic stimulation
SLOW WAVE / Non-REM sleep / Delta wave sleep
• Deep & restful sleep.
• If a person is tired, he passes into deep sleep in 1 hr.
• On average it constitutes 75% of total sleep during a night.
• Dreams can be seen but are not remembered, so cannot be recalled.
• Muscle tone decreases.
SLOW WAVE / Non-REM sleep / Delta wave sleep
• Slowing of heart rate & respiratory rate
• BMR decrease
• There is GH secretion
• Pupillary constriction.
• Sleep walking (somnambulism) may be seen during slow wave sleep
REM sleep / paradoxical sleep
• Occurs in periods lasting for 5-30 min.
• Each period is repeated at every 90 min.
• There are 4-6 periods of REM sleep during a night.
• It constitutes 25% of total night sleep.
REM sleep / paradoxical sleep
• Its duration is different in different age groups.
• There is more REM sleep as age advances.
• If a person is tired, less REM sleep at night.
• If a person has taken rest during day time, more REM sleep at night.
REM sleep / paradoxical sleep
• There is active dreaming & dreams can be recalled.
• It is difficult to arouse the person from REM sleep as compared to non REM sleep but
• Usually in the morning, person wakes up from REM sleep.
REM sleep / paradoxical sleep
• During REM sleep, brain is highly active, so beta waves are recorded from EEG.
• Muscle tone increases.
• Rapid movement of eye.
• Twitching in different parts of body.
• Mild convulsions.
REM sleep / paradoxical sleep
• Respiratory & heart rate becomes irregular during REM sleep.
• Increased secretion of corticosteroid hormones.
• In males, may be erection (parasympathetic stimulation)
• Teeth grinding (BRUXISM) occurs.
• Replacement of alpha rhythm by asynchronous rhythm on opening eye.
Types of SLEEP
• SLOW WAVE / Non-REM sleep / Delta wave sleep
• 75% sleep
• Dreaming without memory
• Increased parasympathetic stimulation
• Decreased muscle tone
• Bed-wetting in children
• REM sleep / paradoxical sleep
• 25% sleep
• Active dreaming with memory
• Increased sympathetic stimulation
• Increased muscle tone, muscle twitching & convulsions.
Types of SLEEP• SLOW WAVE / Non-REM
sleep / Delta wave sleep
• Decreased heart rate
• Decreased respiratory rate
• Pupil constriction
• Easy to arouse from sleep
• Brain is not active
• REM sleep / paradoxical sleep
• Irregular heart rate
• Irregular respiratory rate
• No constriction of pupil
• Difficult to arouse from sleep, but gets up spontaneously in the morning
• Brain is active
Types of SLEEP
• SLOW WAVE / Non-REM sleep / Delta wave sleep
• Increased GH• No erection• No bruxism• Sleep walking
• REM sleep / paradoxical sleep
• Increased corticosteroid
• Erection• Bruxism• No sleep walking
Mechanism of sleep
• There is a cycle of wakefulness & sleep.
• When a person is awake, gradually neurons in reticular activating system become less & less active & there is also activation of certain sleep centers.
• This results into sleep.
Mechanism of sleep
• During hours of sleep, neurons in reticular activating system become progressively more & more active, leading to wakefulness.
Sleep centers:
• 1) LOCUS CERULEUS:
Location:• At junction of midbrain & pons.
• Neurons in this locus secrete nor epinephrine at nerve endings of nerve fibers.
• Nerve fibers from these neurons pass to reticular formation.
Sleep centers:
• This center (Locus Ceruleus) is involved in REM sleep, when brain is highly active.
• So perhaps nor-epinephrine secreting neurons are involved (sympathetic stimulation in REM sleep)
• Ach secreting neurons in reticular formation of upper brain-stem are also involved.
PGO spikes
• In REM sleep there are PGO spikes (large phasic potentials in groups of 3-5).
• These spikes are due to Acetylcholine secreting neurons in this pathway of producing REM sleep.
• Only the tone of neck muscles is dec., other muscles keep their tone.
• But at the same time there is locus ceruleus dependent inhibition of voluntary act.
Sleep centers:
• 2) RAPHE MAGNUS NUCLEUS:• Midline linear nuclei in upper pons & lower
medulla.• Fibers from here pass to reticular
formation, hypothalamus, limbic system & also spinal cord.
• These fibers synapse with pain-inhibitory neurons in dorsal horn of spinal cord (analgesia system).
Sleep centers:
• There is release of serotonin at nerve endings of these fibers.
• Raphe Magnus Nucleus is involved in Deep Slow Wave sleep (NREM sleep).
• Serotonin inhibitors wakefulness.
• Stimulation of SCN of Anterior hypothalamus, certain thalamic nuclei & portion of nucleus of tractus solitarius NREM sleep.
Muramyl dipeptide induced sleep:
Experimental observation:
• In animals kept awake for 2-3 days, muramyl dipeptide & other sleep promoting factors are produced in CSF of brain stem which can be later detected in blood & urine.
• When muramyl dipeptide is injected to some other animal, it immediately passes into sleep.
DISORDERS OF SLEEP:
• 1) Somnambulism / sleep walking
• 2) Bedwetting in children
• 3) Bruxism
• 4) Insomnia
• 5) Narcolepsy
• 6) Sleep apnea
1) Somnambulism / sleep walking• Occurs during slow wave sleep / NREM.
• More common in male children.
• Episode of sleep walking may remain for many minutes.
• Person walks with open eyes, obstacles are avoided during walking.
• Person wakes up unaware of sleep walking.
2) Bedwetting in children
• Also called Nocturnal enuresis.
• May be due to parasympathetic dominance, as it occurs in slow wave sleep.
4) Insomnia
• Inability to sleep, although sufficient facilities & time is available for sleep.
• Reason: Psychological or medical.
5) Narcolepsy:
• There are attacks of intense desire to sleep during day time
• Person cannot resist to sleep in the day
• Attack may last for seconds to minutes
Cause of Narcolepsy:
Etiology:
• Considered to be hypothalamic disorder
Evidence:
• Other features of hypothalamic disorders are present, e.g., obesity, polyuria, sexual retardation.
6) Sleep apnea
• During sleep, breathing stops suddenly.
• May be repeated 100’s of times in severe cases.
• When breathing stops, person wakes up, takes a few breaths & then tries to go to sleep.
6) Sleep apnea
• In the morning, person is fatigued & drowsy.
• There may be features of respiratory failure without respiratory disease.
6) Sleep apnea
ETIOLOGY:
• Exact cause ??
POSSIBLE CAUSES:
• Obesity
• Airway obstruction
• Disease of CNS
Story of sleep disorders:• Somoo (somnambulism / sleep walking) knocks mom’s
bedroom door, while sleeping.
• Complains of wetting his bed (bed-wetting)
• Mom reacts by Bruxism / teeth grinding
• Mom shouts: You disturbed my sleep, I cannot sleep at night because of you!! (insomnia)
• Mom adds: I will now go to sleep at my work place in the day! (narcolepsy)
• Mom continues: I am so tired, that I can hardly breathe (sleep apnea)