Download EEG & Sleep

EEG & Sleep
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 ElectroCorticogram (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.
Brain waves in normal E.E.G
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:
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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.
Clinical use of E.E.G:
• E.E.G silence is sure indication of brain
death.
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
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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
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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
Types of SLEEP
• SLOW WAVE / NonREM sleep / Delta
wave sleep
• REM sleep /
paradoxical sleep
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
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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.
Replacement of alpha rhythm by
asynchronous rhythm on opening eye:
Types of SLEEP
• SLOW WAVE / Non-REM
sleep / Delta wave sleep
• REM sleep / paradoxical sleep
• 75% sleep
• 25% sleep
• Dreaming without memory
• Active dreaming with memory
• Increased parasympathetic
stimulation
• Increased sympathetic
stimulation
• Decreased muscle tone
• Bed-wetting in children
• Increased muscle tone, muscle
twitching & convulsions.
Types of SLEEP
• SLOW WAVE / Non-REM • REM sleep / paradoxical sleep
sleep / Delta wave sleep
• Decreased heart rate
• Irregular heart rate
• Decreased respiratory rate
• Irregular respiratory rate
• Pupil constriction
• No constriction of pupil
• Easy to arouse from sleep
• Difficult to arouse from sleep,
but gets up spontaneously in the
morning
• Brain is not active
• Brain is active
Types of SLEEP
• SLOW WAVE / Non- • REM sleep /
REM sleep / Delta
paradoxical sleep
wave sleep
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Increased GH
No erection
No bruxism
Sleep walking
• Increased
corticosteroid
• Erection
• Bruxism
• No sleep walking
Changes in EEG when a person
goes to sleep:
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:
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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.
3) Bruxism
• Teeth grinding
• Occurs during active sleep (REM 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)