29. Down’s syndrome

Question 1

A 7-year-old boy with Down’s syndrome is scheduled to undergo a 90-minute dental conservation procedure.

What is Down’s syndrome?

Answer 1

Down’s syndrome (Trisomy 21) occurs in approximately 1:700 births

(the commonest congenital abnormality).

The incidence increases with increasing maternal age and the majority
(95%) have an extra chromosome 21 because
of non-disjunction at the time of gamete formation.

It less commonly results from translocation (4%) and
it is these parents who are at great risk of having further affected children.

Question 2

What are the features of Down’s syndrome?

Skull Eyes + Hands

Answer 2

No single feature is pathognomonic of the syndrome, but the association of
several signs can usually lead to a clinical diagnosis. These include:

1. Skull
   Flattened face and occiput
   Third fontanelle
   Brachycephaly
   (the back of the head becomes flattened)
   Small mouth and ears
2. Eyes
   Prominent epicanthic folds
   Oblique palpebral fissure
   Brushfield spots
   Squint, nystagmus
   Cataracts
3. Hands
   Single palmar (Simian) crease
   Short fingers
   Wide gap between first and second toes

Question 3

What are the features of Down’s syndrome?

Resp

Heart

Answer 3

Respiratory
Macroglossia (50%)
Micrognathia
High arched palate (70%)
Subglottic stenosis (2%–6%)
OSA (50%–75%)
Increased susceptibility to respiratory infections
Atlantoaxial instability (15%)
Short, broad neck
Adenotonsillar hypertrophy

Heart
16%–60% have some sort of cardiac abnormality

Question 4

What are the features of Down’s syndrome?

CNS

Endocrine

GIT

Immune

Answer 4

CNS
Developmental delay
Epilepsy (10%)
Early onset Alzheimer’s

Endocrine
Hypothyroidism (40%)

GIT
Gastro-oesophageal reflux

Immune
Leukaemia (risk increased by 20 times)
Immunosuppression and increased infections

Question 5

Cardiac abnormalities associated with Down’s syndrome:

Answer 5

Endocardial cushion defects 40%
VSD 27%
PDA 12%
Fallot’s tetralogy 8%
Others 13%

Question 6

What abnormalities are relevant to anaesthesia?

Answer 6

Airway management

Patients with Down’s syndrome have a large,
protruding tongue,
a small mandible and
an increased incidence of subglottic stenosis

leading to difficult intubation and the need for a smaller tracheal tube than expected.

Atlantoaxial instability occurs in about 15% and is due to laxity of the
transverse atlantal ligament.

It is asymptomatic in most cases, particularly if the atlantoaxial distance
is less than 6 mm.

Care must be taken when manipulating the head and neck
during laryngoscopy/intubation and during anaesthesia in general
because of reduced muscle tone.

There is still debate as to whether all Down’s patients should
have cervical spine X-rays prior to anaesthesia.

The current consensus seems to be that those who are
symptomatic should be X-rayed.

Careful assessment of the airway and review of previous anaesthesia
records may give some indication as to the expected ease of laryngoscopy.

Post-extubation stridor, post-operative chest infections and pulmonary
oedema are more common than in the normal population.

Question 7

What abnormalities are relevant to anaesthesia?

Cardiac

Answer 7

The cardiac abnormalities associated with
Down’s syndrome are outlined above.

The main clinical problem is pulmonary hypertension,
which may also be present in the absence of an anatomical lesion

(? related to chronic anaemia).

Anaesthesia is based around controlling the balance
between pulmonary and systemic vascular resistance.

Question 8

What abnormalities are relevant to anaesthesia?

CNS

Answer 8

Intellectual impairment
May cause difficulties with co-operation at induction.
Associated epilepsy

Higher incidence of hepatitis B in institutionalised patients