Lec 18 - SIDS

Question 1

What’s the definition of SIDS

Answer 1

1989 - sudden death of infant <1, + associated with sleep unexplained after autopsy, exam of circumstances of death + clinical history review
heterogeneous entity w/characteristic epi + clin features + diverse etiological pathways

Question 2

characterisitics of SIDS babies

Answer 2

0.5-.4/1000 live births
low SES
male
premature (low birth weight)
winter

Question 3

characteristics of SIDS mums

Answer 3

single
smoker
high parity w/short inter-pregnancy intervals
infection in pregnancy

Question 4

what is the respiratoy theories of SIDS

Answer 4

apparent life-threatening events
apnea > 20 seconds, cyanosis, near miss

Question 5

what is central apnea

Answer 5

failure of inspiration
- prematurity
- seizure induced
- rem sleep

Question 6

why does central apnea occur

Answer 6

defective:
- brainstem centres
- defective chemoreceptors
- defective stretch receptors

Question 7

what is obstructive apnea + evidence

Answer 7

normal occurrence eg smothering -> airway blockage
small choanae
large tongue
small mandible
lack of positive distending pressure

Question 8

what is accidental asphyxia

Answer 8

wedging
overlaying
plastic covers
water beds

Question 9

describe gastroesophageal reflux 1

Answer 9

acid -> eso -> chemoreceptors -> brainstem -> apnea

Question 10

describe gastroesophageal reflux II

Answer 10

acid -> bronchus -> type II pneumocyte damage -> reduced surfactant -> atelectasis -> apnea

Question 11

describe gastroesophageal reflux III

Answer 11

acid -> eso -> chemoreceptors -> brainstem -> bradycardia

Question 12

what are cardiac theories with SIDS

Answer 12

abberant conduction pathways
prolonged QT interval
abnormal response to autonomic control

Question 13

what is the problem with determining cardiac theories in SIDS

Answer 13

no antemortem ECGs
lack of histologic abnormalities

Question 14

role of infection in SIDS

Answer 14

occult infection causes or predisposes
clostridium botulinum - can cause sudden infant death but not related to SIDS
cytomegalovirus - not a problem
avon study - no difference in infection type

Question 15

immunological hyper-reactivity in SIDS

Answer 15

house dust mites, cow’s milk protein?
no consistent findings

Question 16

breast feeding in SIDS

Answer 16

protective = reduced DHA, inc neural maturation

Question 17

tripe risk model for SIDS

Answer 17

critical developnment period + exogenous stressors + vulnerable infant
shared sleeping = infant (young, small, premature) + parent (sedated, intoxicated, smoking, obese) + bed (multiple cosleepers, heavy covers, soft surface) some babies will die

Question 18

risk factors for SIDS

Answer 18

prone sleeping - face-down, 9x risk, airway obstruct, diaphragm splinting, reinhaling co2
cig smoke
covering head
overheating

Question 19

when does peak SIDS incidence coincide

Answer 19

with marked physiological changes in neural control of respiration, cardiac function and sleep cycles
=> generalised arousal deficit

Question 20

what are neuropath findings in SIDS

Answer 20

brainstem gliosis
arcuate nucleus receptor changes
inc neuronal dendritic spines
abnormal carotid bodies

Question 21

impact of neuropath findings

Answer 21

defective
- autonomic control
- brainstem respiratory control centres
- brainstem cardiac cc
- peripheral pulm rec
- vagal dysf
- chemo rec dysf
- arousal/sleep disturbance
- hyperpyrexia
- abnormal ntsm + brainstem receptors

Question 22

describe brainstem gliosis

Answer 22

17% cases
tegmental region in medulla, dorsal nucleus of vagus, inferior olivary nucleus, solitary nucleus, reticular nuclei
angiography - underperfused areas

Question 23

describe dendritic spines in SIDS

Answer 23

inc dendritic spines in brainstem neurons
maturational delay
effects cardiorespiratory control

Question 24

hypomyelination in SIDS

Answer 24

variable results => dec in SIDS
hypo or delayed myelination?
what is significance?

Question 25

describe decosahexenoic acid in SIDS

Answer 25

dec in SIDS DHA related to cerebral maturation demonstrated dec cortical levels in some SIDS infants

Question 26

arcuate nucleus hypoplasia

Answer 26

reduced size in some SIDS infants possible cardiorespiratory effect

Question 27

ntsm abnormalities in SIDS

Answer 27

defects in medullary serotonergic network reduced muscarininc, kainate, serotingergic receptor binding defects in promotor region of serotonin transporter 5-HTT gene failure to respond to autonomic challenges during sleep

Question 28

what does substance P do

Answer 28

SP is a tachykinin neuropeptide - excit + mod ntsm via tachykinin NK1R (co-transmitter with 5HT) stim respiration primary ntsm in carotid chemoreceptor reflex mediates ventilatory responses

Question 29

describe role of Nk1 receptor + the relevant study

Answer 29

respiratory rhythm generation maintenance of respiratory timing during sustatined hypoxia arcuate nuecleus from formalin fixed paraffin stained for sub P and NK1 rec dec in sub P immunoreactivity in arcuate nucleus in SIDS

Question 30

aim and hypothesis of bolton hunter sub p autoradiography

Answer 30

determination of NK1R binding density with sub p autoradiography in medullary 5HT system in SIDS vs controls hypothesis: NK1R binding densirt will dec in brainstem medullary 5HT for SIDS

Question 31

what is the inferior olivary complex (IoC)

Answer 31

defecits in cerebellar systems, purkinje fiber damage, ntsm defecits in IOC = associated with SIDS IOC - integration motor + sensory info, motor learning, control, coordination subdivisions DAO + MAO project to diff regions cerebellum MAO => vermis => propioception, sense spatial/positional mbm neck, shoulders, hips

Question 32

link between IOC and SIDS

Answer 32

reduction in NK1R density in DAO and MAO neg influence on cerebellar circuitary + motor control in SIDS infants

Question 33

inc brain weight and SIDS suggestions for cause

Answer 33

cerebral swelling/oedema agonal hypoxia/ischaemia metabolic/toxic megalencephaly agonal/vascular congestion

Question 34

what is B-amyloid precursor protein

Answer 34

transmembrane glycoprotein in axons nonspecific marker for axonal injury hypoxia, trauma, ischaemia, toxins

Question 35

why is BAPP significnat

Answer 35

lots means difficulty control respiration => low O2 saturation potential marker for familial central apnea SIDS and asphyxia have similar BAPP staining patterns