Infantile Spasms Health Article

Definition

Infantile spasms (IS) are seizures seen in epilepsy of infancy and early childhood. The typical pattern of an infantile spasm occurs soon after arousal from sleep, and involves a sudden bending forward and stiffening of the body, arms, and legs. Additionally, arching of the torso can also be seen during an infantile spasm. Infantile spasms typically last for one to five seconds and occur in clusters, ranging from two to 100 spasms at a time.

Description

Infantile spasms were first described by the English physician W.J. West (1794–1848) in 1841. West's paper, published in the first volume of the medical journal Lancet, was a landmark in the development of pediatric neurology, and the seizure syndrome also became known as West syndrome. West observed the condition in his own infant son, giving a precise and complete description of the symptoms, along with the gradual mental deterioration, and intractability of the syndrome. Other neurological disorders, such as cerebral palsy, may be seen in almost half of infants with infantile spasms.

Infantile spasms may have variable features, but have been categorized primarily into three subtypes based on manifestations of posture and patterns of muscle involvement during the seizure. Flexor spasms involve flexion of the neck, trunk, and extremities. Extensor spasms consist of extension of the neck, trunk, and extremities. Mixed flexor-extensor spasms involve combinations of the above.

In many patients, spasms exhibit characteristic patterns involving time. Fifty to eighty percent of the epileptic spasms occur in clusters of two to more than 100 seizures. Patients may have dozens of clusters and several hundred spasms per day, but individual variability in seizure frequency is often large. Although spasms rarely occur during sleep, clusters of spasms are frequently activated after awakening from sleep. Spasms are occasionally triggered by loud noises with associated arousal from drowsiness and sleep, but are generally not sensitive to stimulation by human voices.

Demographics

In the United States, infantile spasms constitute 2% of childhood epilepsies, and 25% of epilepsies with onset in the first year of life. The rate of IS is 1.6–5.0 cases per 10,000 live births. As many as 5% of infants with this condition eventually die from complications of the seizures. Although males are affected slightly more often than females, no significant gender difference is noted.

Causes and Symptoms

The number of neurological diseases that can result in infantile spasms is very large, but some of the major categories include intrauterine injury and infection, disorders caused by lack of blood flow to the fetal brain, developmental malformations of the cerebral cortex, metabolic disorders, other genetic or chromosomal defects, meningitis, and tumors. These seizures are assumed to reflect abnormal interactions between the cortex and brainstem structures. The frequent onset of the spasms in infancy suggests that an immature central nervous system may be important in the formation of infantile spasm syndrome. One theory states that the effect of different stressors in the immature brain produces an abnormal excessive secretion of corticotropin-releasing hormone, which causes spasms.

In 90% of children with the condition, infantile spasms occur in the first year of life, typically between three to six months of age. Often, in the beginning, the attacks are brief, infrequent and not typical, so it is quite common for the diagnosis to be delayed. Frequently, because of the pattern of attacks and the cry that a child gives during or after an attack, they are initially thought to be due to colic, or gastric distress.

The typical pattern is of a sudden flexion (bending forward) in a tonic (stiffening) fashion of the body, arms, and legs. Sometimes, however, the episodes are of the extensor type (arching). Usually, they are symmetrical, but sometimes one side is affected more than the other.

Typically, each episode lasts a few seconds, followed by a pause of a few seconds, and a further spasm. While single spasms may occur, infantile spasms usually occur in sets of several spasms in a row. It is common for babies with infantile spasms to become irritable and for their development to slow down or even regress until the spasms are controlled.

Diagnosis

Information about the child's seizures and about the pregnancy, birth, and progress since birth, will help the physician in making the diagnosis. The diagnosis of infantile spasms is made by a combination of the typical features, along with a characteristic electroencephalogram (EEG), which shows a very disorganized pattern termed hypsarrhythmia.

Most children with infantile spasms will need a number of tests, such as blood, urine, and cerebrospinal fluid (fluid which circulates around the brain and spinal cord) sampling, in an attempt to screen for any infection or metabolic abnormality. X-ray studies such as CT scans, ultrasound, or MRI will be performed to evaluate the structure of the brain.