Which of the following is a neuromuscular disease included in the hypertonicity category?

• A. Multiple sclerosis
• B. Amyotrophic lateral sclerosis
• C. Parkinson’s disease
• D. Muscular dystrophy

Answer: (A)

Spasticity, a velocity-dependent increase in muscle tone, is a hallmark of hypertonicity that stems from upper motor neuron involvement. Multiple sclerosis is a classic CNS disease where demyelinating lesions disrupt corticospinal pathways, leading to disinhibition of reflexes and the development of spastic hypertonia in affected muscles. This makes MS a prototypical neuromuscular condition categorized under hypertonicity.

Other options either emphasize different forms of increased tone or primary muscle/nerve pathology. Parkinson’s disease mainly presents with rigidity, another form of hypertonia but arising from basal ganglia dysfunction rather than corticospinal tract changes. Muscular dystrophy is a primary muscle disease and typically presents with reduced tone (hypotonia) rather than spastic hypertonia. Amyotrophic lateral sclerosis can cause spasticity as UMN signs overlap with LMN involvement, but MS is the classic example highlighted in hypertonicity classification.