🔑 Key Learning

  • Red flags: not sitting by 8 months, not walking by 18 months, or early hand preference (<1 year)
  • Common causes: cerebral palsy (UMN), spinal muscular atrophy (LMN), Duchenne muscular dystrophy (myopathy)

đŸš© Early Years Red Flags

  • Floppy, poor head control
  • Unable to sit unsupported by 8 months
  • Asymmetry of motor skills - e.g. hand preference before 1 year
  • Not walking by 18 months
  •  💡 Tip: 8, 1, 18

🧬 Causes

  • Central motor deficit – cerebral palsy, SMA
  • Myopathy – Duchenne muscular dystrophy
  • Spinal cord lesions – spina bifida
  • Global delay – syndromes, unidentified causes

🧠 Cerebral Palsy

A chronic disorder of movement and/or posture that typically presents at < 2yrs. May be accompanied by disrupted development of cognition, communication etc. 

Pathology

  • Static injury to developing brain → movement/posture disorder
  • Causes:
    • 80% antenatal – cerebrovascular haemorrhage, congenital infection
    • 10% - hypoxic-ischaemic injury (birth asphyxiation)
    • 10% post-natal – meningitis/ encephalitis/ head trauma. Hypoglycaemia 

Clinical Features

  • Abnormal limb/trunk posture + tone
  • Abnormal gait 
  • Unable to sit without support by 8 months 
  • Asymmetric hand function/preference before 12 months
    • Suggests hemiplegia
  • Feeding difficulties – due to oromotor incoordination, gagging

Subtypes

  • Spastic: increased tone, brisk reflexes
  • Dyskinetic: dystonia, choreoathetosis
  • Ataxic: cerebellar features

🧬 Spinal Muscular Atrophy (SMA)

Pathology

  • AR mutation in SMN1 → anterior horn cell degeneration → LMN syndrome

Clinical Features

  • Floppy baby
  • Tongue fasciculations
  • Symmetric weakness, hypotonia
  • Hyporeflexia, bulbar signs

đŸ’Ș Duchenne Muscular Dystrophy (DMD)

The commonest type of muscular dystrophy - 1/3000 males.

Pathology

  • X-linked recessive
  • Molecular abnormality of dystrophin → progressive myofibre degeneration

Clinical Features

  • Commonly presents around 4-5yrs age – waddling lordotic gait
  • Abnormal gait - flat footed, persistent toe-walking
  • Delayed motor milestones and speech problems 
  • Calf pseudohypertrophy – replacement of muscle fibres by fat and fibrous tissue
  • Weakness in limb girdles (lower esp.) – Gower’s sign
    • Uses hands and arms to ‘walk up’ their own body from a squatting position due to lack of hip and thigh muscle strength.
  • Progressive atrophy - no longer ambulant by 10-15yrs
Duchenne muscular dystrophy. Gower sign.

Investigations

  • Raised CK
  • Genetic analysis

đŸ’Ș Becker Muscular Dystrophy (BMD)

Pathology

  • X-linked recessive
  • Same allele affected as DMD, but some functional dystrophin production is maintained - as a result, patients have milder features with later onset and slower progression.

Clinical Features

  • Diagnosed later than DMD ∌11 yrs
  • Mild early symptoms – fatigue, exercise cramps
  • Proximal weakness → shoulder girdle later
  • Patients are typically ambulatory until late twenties, and LE until mid-old age.

Complications

  • Dilated cardiomyopathy

📝 Exam Clues & Clinchers

  • Spastic CP: early hand preference, scissoring, UMN signs
  • SMA: floppy baby, tongue fasciculations, absent reflexes
  • DMD: Gower’s sign, calf hypertrophy, delayed milestones
  • BMD: similar to DMD, but slower progression and later onset