Spastic seizures are a form of epilepsy that typically appears in the first year of life, with peak onset between four and seven months. These seizures are defined by a sudden, brief, and forceful contraction of the body’s muscles, often lasting only a second or two but occurring many times a day. While they can be mistaken for a simple startle reflex or colic, they represent a serious neurological event. The condition is rare, affecting approximately 1 in 2,000 to 4,000 live births.
Recognizing a Spastic Seizure
A spastic seizure is characterized by sudden muscle stiffening and falls into three main categories based on the observed movement. The most recognized form is the flexor spasm, where the baby’s body, arms, and legs bend forward abruptly. This motion is often described as a “jackknife” or “salaam” seizure and resembles a crunching motion as the knees are pulled toward the chest.
Another presentation is the extensor spasm, involving a sudden straightening of the body where the head may be thrown backward as the arms and legs extend rigidly. The most common presentation is a mixed spasm, which combines elements of both flexor and extensor movements. For instance, an infant might exhibit flexion in their neck and trunk while their legs extend.
These seizures frequently occur in clusters, with one spasm following another over several minutes. The clusters are often linked to the infant’s sleep-wake cycle, appearing just after waking or while falling asleep. Other signs can include the eyes widening or rolling up. Because the spasms are brief, they can be misinterpreted as normal baby movements.
Underlying Causes and Associated Conditions
Spastic seizures are not a disease but a symptom of an underlying issue affecting the brain. The most common condition associated with them is Infantile Spasms, also known as West syndrome. West syndrome is defined by a triad of symptoms: spastic seizures, a chaotic brain wave pattern on an EEG, and developmental regression or delay.
Many cases are linked to structural brain abnormalities, such as malformations that occurred during fetal development. Another cause is tuberous sclerosis complex, a genetic disorder that causes non-cancerous tumors to grow in the brain and other organs. Genetic and metabolic disorders are also identified as sources of the condition.
Brain injuries around the time of birth can also lead to spastic seizures. Perinatal asphyxia, where a newborn does not get enough oxygen around birth, can cause brain damage that later manifests as these seizures. Infections acquired in the womb or during infancy may also be a factor. In some cases, a specific cause cannot be identified.
The Diagnostic Process
Confirming a diagnosis requires an evaluation by a pediatric neurologist. The process begins with a physical and neurological examination to assess the baby’s development, reflexes, and health. The parent’s description of the events is a component of the diagnosis, and home videos of suspected seizures are very helpful for the medical team.
The most definitive diagnostic tool is the electroencephalogram (EEG), which records the brain’s electrical activity using scalp sensors. In many cases of infantile spasms, the EEG reveals a unique, disorganized pattern known as hypsarrhythmia. This pattern of chaotic spikes and slow waves is a hallmark of West syndrome.
To identify the underlying cause, doctors use neuroimaging techniques like a magnetic resonance imaging (MRI) scan of the brain. An MRI can reveal structural problems such as malformations, injury, or tumors. Blood and urine tests may also be ordered to screen for metabolic or genetic disorders.
Medical Management and Treatment Approaches
The primary goal of treatment is to stop the seizures and resolve abnormal brain wave patterns as quickly as possible for better long-term developmental outcomes. The two main first-line treatments are steroid therapy and a specific anti-seizure medication. Adrenocorticotropic hormone (ACTH) is a hormonal therapy administered by injection that is effective in stopping the spasms.
The other primary medication is vigabatrin, an anti-seizure drug particularly effective for infants whose seizures are caused by tuberous sclerosis complex. The choice between ACTH and vigabatrin depends on the underlying cause, medical protocols, and physician experience.
If initial treatments are not successful, other options may be explored, such as different antiepileptic drugs (AEDs) or the ketogenic diet. The ketogenic diet is a high-fat, low-carbohydrate medical diet that can help control seizures in some forms of epilepsy. In specific cases where seizures are caused by a localized brain abnormality, epilepsy surgery to remove that area may be considered.