Diplegia is a neurological condition resulting from an injury to the developing brain, which impacts the signals sent to the muscles. This damage causes a permanent disorder of movement, typically identified in infancy or early childhood when developmental delays become apparent. The condition is non-progressive, meaning the underlying brain injury does not worsen over time, though its physical manifestations can change as a child grows.
Understanding the Scope of Diplegia
The term “diplegia” refers to paralysis or significant weakness affecting two corresponding limbs. In motor disorders, this condition almost exclusively impacts the lower extremities much more severely than the upper limbs. The arms and hands may have only mild involvement, or they may be completely unaffected. Diplegia is classified by the anatomical distribution of the motor impairment, distinguishing it from other types of paralysis, such as hemiplegia (one side of the body) or quadriplegia (all four limbs).
The most common form is Spastic Diplegia, a specific subset of cerebral palsy (CP). CP is an umbrella term for non-progressive motor disorders that occur due to brain damage. Spasticity, present in up to 80% of all CP cases, refers to an increase in muscle tone that causes muscles to be stiff and tight.
Primary Physical Characteristics
The defining feature of diplegia is high muscle tone, or spasticity, predominantly in the leg muscles. This constant stiffness results from exaggerated reflexes and impairs standing and walking by pulling the leg muscles inward and causing the hips and knees to flex. A hallmark sign is the characteristic “scissoring gait,” where the legs cross over each other while walking due to tight hip adductor and flexor muscles. Children often exhibit toe walking, caused by spasticity in the calf muscles.
These abnormal gait patterns lead to balance problems, frequent falls, and delays in achieving gross motor milestones. Chronic spasticity can lead to secondary orthopedic issues due to the constant, uneven pull on the joints. Complications include contractures (shortening of muscles and tendons) and hip displacement or dislocation.
Etiology and Common Risk Factors
Diplegia results from damage to the brain’s white matter, which transmits signals to the motor neurons in the spinal cord. This injury often affects the part of the brain that controls leg movement and is frequently identified as periventricular leukomalacia (PVL)—the destruction of white matter near the brain’s ventricles. The timing of this injury is typically before or during birth, although it can occur shortly thereafter.
Extreme prematurity is the greatest risk factor; infants born before 32 weeks of gestation or with a very low birth weight (under 1,500 grams) are particularly susceptible. A lack of oxygen or blood flow to the brain, known as hypoxia-ischemia, is another major cause, often occurring due to complications with the placenta or umbilical cord during delivery. Severe infections in the mother or newborn, such as meningitis, can also lead to the brain inflammation and injury that causes the condition.
Diagnostic Process and Therapeutic Interventions
Diagnostic Process
Diagnosis begins with developmental monitoring and a thorough physical examination, observing a child’s muscle tone, reflexes, and motor skill progression. If a delay in meeting milestones is noted, brain imaging studies are used to confirm the underlying neurological damage. Magnetic Resonance Imaging (MRI) is the preferred method, as it provides detailed images that can reveal the characteristic white matter injury of PVL.
Therapeutic Interventions
Management of the condition is a lifelong, multidisciplinary effort aimed at improving mobility and reducing the effects of spasticity. Physical therapy and occupational therapy are foundational components, focusing on stretching, strengthening, and developing functional motor skills. Orthotic devices, such as braces or splints, are often used to provide support, stabilize joints, and maintain muscle length.
Medical treatments are employed to manage the persistent muscle stiffness and include both oral medications and localized injections. Oral muscle relaxants, such as baclofen and diazepam, work systemically to reduce nerve excitability and decrease overall muscle tone. For focal spasticity, injections of botulinum toxin (Botox) are administered directly into the tight muscle.
For children with severe lower-limb spasticity, a neurosurgical procedure called Selective Dorsal Rhizotomy (SDR) may be considered. During SDR, surgeons selectively cut the overactive sensory nerve rootlets in the lower spinal cord that are causing the excessive muscle tightness, providing a permanent reduction in spasticity.