In individuals with spina bifida, the pattern of muscle tone is typically:

• A. Hypertonia and hypotonia
• B. Normal tone
• C. Flaccid only
• D. Hypotonia and spasticity

Answer: (D)

The muscle tone pattern in spina bifida reflects both lower motor neuron involvement at the level of the lesion and upper motor neuron involvement below it. Damaged nerve roots at the lesion produce decreased tone (hypotonia) in muscles innervated there. In contrast, disruption of corticospinal pathways below the lesion leads to increased tone (spasticity) in muscles beneath the level of the lesion. Because both phenomena can occur in different regions, the typical pattern is a mix of hypotonia in the affected (at the lesion) areas and spasticity in muscles below the lesion. This combination explains why hypotonia and spasticity is the best answer.