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Spinal muscular atrophy (SMA) (Clinical presentation (Weak cry, poor…
Spinal muscular atrophy
(SMA)
Definition
Genetic degenerative neurological
disorder affecting anterior horn cell
causing weakness and wasting
Epidemiology
2nd commonest neuromuscular disease
after DMD
Pathophysiology
Defect
Mutations in SMN1
Mechanism
Degeneration of anterior horn cells in the spinal cord
Weakness and wasting of skeletal muscles
Types
Type 0: most severe, survival few weeks
Type 1: severe, positional deformities, paralysis, difficulties feeding and breathing
Type 2: present at 3-15m, never walk independently
Type 3: present >1y, can learn to walk
Clinical presentation
Weak cry, poor suckling
Paralysis
Delayed motor milestones
Difficulty breathing
Positional deformity
(arthrogyposis)
Diagnosis
Examination
Respiratory
Intercostal recession, weak cry,
respiratory distress
Neuro
LMN signs (weakness, fasiculations,
wasting, absent reflexes)
Newborn
Alert expression
Flaccid paralysis, wasting, fasiculations, weakness
Absent deep tendon reflexes
Developmental
Delayed motor milestones
Investigations
Bloods
SMA genetic testing
Special tests
EMG and EEG: shows neuromuscular disorder
Bedside
Obs (may have low sats, high RR)
History
PMH
Growth and development
Vaccinations
Known medical conditions
DH
Meds, allergies
POH
Scans, growth, bloods,
gestation, delivery, complications
PC/HPC
Poor cry, poor feeding, paralysis,
delayed motor milestones
FH
SMA, other muscular disorder
SH
Living arrangements,
school/nursery
Management
Conservative
Information, advice, support
MDT care (nurses, neurologist, dietician, SALT)