Cerebral palsy (CP) is a neurological disorder caused by a non-progressive brain injury or malformation that occurs during early brain development, often before, during, or shortly after birth. This brain injury affects the parts of the brain responsible for controlling movement, muscle tone, and posture. When cerebral palsy affects only one side of the body, it is typically referred to as **spastic hemiplegic cerebral palsy**. This condition results in muscle stiffness (spasticity) and weakness predominantly on one side of the body, such as one arm and one leg on the same side[2].
The reason cerebral palsy affects only one side of the body lies in the **location and extent of the brain injury**. The brain controls movement on the opposite side of the body through pathways called the corticospinal tracts. These tracts cross over (decussate) in the brainstem, meaning the left hemisphere controls the right side of the body and vice versa. If the injury or lesion is localized to one hemisphere of the brain—often the motor cortex or the white matter pathways beneath it—then the motor control and muscle tone on the opposite side of the body will be impaired[2][6].
In spastic hemiplegic CP, the damage is usually unilateral (one-sided), affecting the motor areas that control voluntary movement. This leads to:
– **Spasticity**: Increased muscle tone causing stiffness and resistance to movement on the affected side.
– **Muscle weakness**: Reduced strength in muscles on the affected side.
– **Impaired motor control**: Difficulty with fine and gross motor skills such as grasping, walking, or coordination on the affected side.
– **Asymmetry in posture and movement**: The unaffected side typically functions normally, leading to noticeable imbalance[2][5].
The brain lesion causing hemiplegic CP can result from various factors such as:
– **Perinatal stroke**: A stroke occurring around the time of birth that damages one hemisphere.
– **Intraventricular hemorrhage or periventricular leukomalacia**: Types of brain injury common in premature infants affecting white matter near the ventricles.
– **Trauma or infection**: Early brain injury from trauma or infections can also cause localized damage[2].
The non-progressive nature of the brain injury means the damage itself does not worsen over time, but the symptoms can change as the child grows. Secondary musculoskeletal problems such as contractures (permanent muscle shortening) and joint deformities may develop due to abnormal muscle tone and use patterns[2][4].
Muscle tissue on the affected side also undergoes changes. Studies show that muscles in children with CP often have altered structure and function, including shorter muscle fibers and increased stiffness, which contribute to the spasticity and weakness observed clinically[6]. These muscle changes are a direct consequence of the abnormal neural input from the damaged brain areas.
The clinical diagnosis of hemiplegic CP is based on observing these asymmetrical motor impairments, abnormal muscle tone, and reflexes. Imaging studies such as MRI can often identify the unilateral brain lesion responsible for the symptoms[2].
Treatment for hemiplegic cerebral palsy focuses on improving function and quality of life. It includes:
– **Physical therapy** to improve strength, flexibility, and motor skills on the affected side.
– **Occupational therapy** to enhance fine motor skills and daily living activities.
