Lec 18 - SIDS Flashcards
What’s the definition of SIDS
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
characterisitics of SIDS babies
0.5-.4/1000 live births
low SES
male
premature (low birth weight)
winter
characteristics of SIDS mums
single
smoker
high parity w/short inter-pregnancy intervals
infection in pregnancy
what is the respiratoy theories of SIDS
apparent life-threatening events
apnea > 20 seconds, cyanosis, near miss
what is central apnea
failure of inspiration
- prematurity
- seizure induced
- rem sleep
why does central apnea occur
defective:
- brainstem centres
- defective chemoreceptors
- defective stretch receptors
what is obstructive apnea + evidence
normal occurrence eg smothering -> airway blockage
small choanae
large tongue
small mandible
lack of positive distending pressure
what is accidental asphyxia
wedging
overlaying
plastic covers
water beds
describe gastroesophageal reflux 1
acid -> eso -> chemoreceptors -> brainstem -> apnea
describe gastroesophageal reflux II
acid -> bronchus -> type II pneumocyte damage -> reduced surfactant -> atelectasis -> apnea
describe gastroesophageal reflux III
acid -> eso -> chemoreceptors -> brainstem -> bradycardia
what are cardiac theories with SIDS
abberant conduction pathways
prolonged QT interval
abnormal response to autonomic control
what is the problem with determining cardiac theories in SIDS
no antemortem ECGs
lack of histologic abnormalities
role of infection in SIDS
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
immunological hyper-reactivity in SIDS
house dust mites, cow’s milk protein?
no consistent findings
breast feeding in SIDS
protective = reduced DHA, inc neural maturation
tripe risk model for SIDS
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
risk factors for SIDS
prone sleeping - face-down, 9x risk, airway obstruct, diaphragm splinting, reinhaling co2
cig smoke
covering head
overheating
when does peak SIDS incidence coincide
with marked physiological changes in neural control of respiration, cardiac function and sleep cycles
=> generalised arousal deficit
what are neuropath findings in SIDS
brainstem gliosis
arcuate nucleus receptor changes
inc neuronal dendritic spines
abnormal carotid bodies
impact of neuropath findings
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
describe brainstem gliosis
17% cases
tegmental region in medulla, dorsal nucleus of vagus, inferior olivary nucleus, solitary nucleus, reticular nuclei
angiography - underperfused areas
describe dendritic spines in SIDS
inc dendritic spines in brainstem neurons
maturational delay
effects cardiorespiratory control
hypomyelination in SIDS
variable results => dec in SIDS
hypo or delayed myelination?
what is significance?
describe decosahexenoic acid in SIDS
dec in SIDS
DHA related to cerebral maturation
demonstrated dec cortical levels in some SIDS infants
arcuate nucleus hypoplasia
reduced size in some SIDS infants
possible cardiorespiratory effect
ntsm abnormalities in SIDS
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
what does substance P do
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
describe role of Nk1 receptor + the relevant study
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
aim and hypothesis of bolton hunter sub p autoradiography
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
what is the inferior olivary complex (IoC)
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
link between IOC and SIDS
reduction in NK1R density in DAO and MAO
neg influence on cerebellar circuitary + motor control in SIDS infants
inc brain weight and SIDS suggestions for cause
cerebral swelling/oedema
agonal hypoxia/ischaemia
metabolic/toxic
megalencephaly
agonal/vascular congestion
what is B-amyloid precursor protein
transmembrane glycoprotein in axons
nonspecific marker for axonal injury
hypoxia, trauma, ischaemia, toxins
why is BAPP significnat
lots means difficulty control respiration => low O2 saturation
potential marker for familial central apnea
SIDS and asphyxia have similar BAPP staining patterns
