A 6-month-old with increased tone and leg scissoring is most consistent with which condition?

A 6-month-old with increased tone and leg scissoring is most consistent with which condition?

• A. Cerebral palsy
• B. Muscular dystrophy
• C. Down's syndrome
• D. Fragile X syndrome

Answer: (A)

Legs that scissor together with increased muscle tone in a 6‑month‑old point to spastic cerebral palsy, usually from early upper motor neuron injury affecting the corticospinal tracts. In spastic CP, hypertonia and brisk reflexes develop, and adductor spasticity can cause the legs to cross or pinch inward, which is the scissoring pattern often seen in involvement of the legs (spastic diplegia). This pattern is particularly common in infants who were born preterm or who have periventricular white matter injury. Muscular dystrophy tends to present with progressive proximal muscle weakness and characteristic gait changes later in childhood, not early hypertonia with leg scissoring. Down syndrome and Fragile X syndrome can show hypotonia and developmental delays in infancy, but the specific combination of increased tone with leg scissoring is most consistent with spastic cerebral palsy.

Legs that scissor together with increased muscle tone in a 6‑month‑old point to spastic cerebral palsy, usually from early upper motor neuron injury affecting the corticospinal tracts. In spastic CP, hypertonia and brisk reflexes develop, and adductor spasticity can cause the legs to cross or pinch inward, which is the scissoring pattern often seen in involvement of the legs (spastic diplegia). This pattern is particularly common in infants who were born preterm or who have periventricular white matter injury.

Muscular dystrophy tends to present with progressive proximal muscle weakness and characteristic gait changes later in childhood, not early hypertonia with leg scissoring. Down syndrome and Fragile X syndrome can show hypotonia and developmental delays in infancy, but the specific combination of increased tone with leg scissoring is most consistent with spastic cerebral palsy.