Infantile spasms are seizures characterized by sudden flexion of the arms, forward flexion of the trunk, extension of the legs, and hypsarrhythmia on EEG.
Infantile spasms last a few seconds and can recur many times a day. They usually manifest in children < 1 yr. Seizures may resolve spontaneously by about age 5 yr but are often replaced by other types of seizures.
Pathophysiology is unknown; however, infantile spasms may reflect abnormal interactions between the cortex and brain stem.
Usually, infantile spasms occur in infants with serious brain disorders and developmental abnormalities that often have already been recognized. These disorders may include
Tuberous sclerosis is a common cause; prognosis is sometimes better when seizures are caused by this disorder than when seizures have other identifiable causes.
Sometimes the cause cannot be identified.
Spasms begin with a sudden, rapid, tonic contraction of the trunk and limbs, sometimes for several seconds. Spasms range from subtle head nodding to contraction of the whole body. They involve flexion, extension, or, more often, both (mixed). The spasms usually occur in clusters, often several dozens, in close succession; they occur typically after children wake up and occasionally during sleep. Sometimes at first, they are mistaken for startles.
Developmental defects are usually present. In the first stages of the disorder, developmental regression can occur (eg, children may stop smiling or lose the ability to sit up or roll over).
Rate of premature death ranges from 5 to 31% and is related to the etiology of the infantile spasms.
Previous history (eg, neonatal hypoxic-ischemic encephalopathy) and/or symptoms and signs suggest the diagnosis in some children. Physical and neurologic examinations are done, but often no pathognomonic findings are identified except in tuberous sclerosis.
Waking and sleep EEG is done to confirm the diagnosis and check for specific abnormalities. Typically, the interictal pattern is hypsarrhythmia (chaotic, high-voltage polymorphic delta and theta waves with superimposed multifocal spike discharges). Multiple variations (eg, focal or asymmetric hypsarrhythmia) are possible. The ictal pattern is usually a sudden, marked and diffuse attenuation of electrical activity.
Neuroimaging, preferably MRI, is done if it has not already recently been done.
If it is not clear from neuroimaging or the previous history, tests to determine the cause may include
Laboratory tests (eg, CBC with differential; measurement of serum glucose, electrolytes, BUN, creatinine, sodium, calcium, magnesium, phosphorus, serum amino acids, and urine organic acids; liver function tests) if a metabolic disorder is suspected
CSF analysis to check for metabolic disorders
Infantile spasms are not responsive to typical anticonvulsants.
ACTH is the most effective treatment. Both high-dose (150 units/m2) ACTH and low-dose (20 units/m2) ACTH, given daily IM, have been used, and evidence that the higher doses work better is not conclusive; however, generally, if low-dose therapy has not stopped spasms within 2 wk, higher doses are used. ACTH therapy is typically continued at the effective dose for 2 to 3 wk and then tapered off over 6 to 9 wk.
Vigabatrin is the only anticonvulsant with proven efficacy; it is the drug of choice when the spasms are caused by tuberous sclerosis and is often used in children with an established preexisting serious brain injury or malformation and in those who do not tolerate or respond to ACTH. Dosage of vigabatrin is 25 mg/kg twice/day, increased gradually up to 75 mg/kg twice/day if needed. There is insufficient evidence that any other anticonvulsants or the ketogenic diet is effective.
Corticosteroids (eg, prednisone 2 mg/kg/day po) are sometimes given for 4 to 7 wk as an alternative to ACTH.
In some patients with resistant spasms, focal cortical resection can eliminate seizures.
There is evidence that the more quickly effective therapy is initiated, the better the neurodevelopmental outcome, particularly when no cause is identified.
Infantile spasms last a few seconds and can recur many times a day; they may resolve spontaneously by about age 5 yr but are often replaced by other types of seizures.
Usually, infantile spasms occur in infants with serious brain disorders and developmental abnormalities that often have already been recognized; tuberous sclerosis is a common cause.
Do waking and sleep EEG to confirm the diagnosis and to check for specific abnormalities; neuroimaging (preferably MRI), if not recently done, should be done.
ACTH is the most effective treatment, but vigabatrin is the drug of choice for spasms caused by tuberous sclerosis and is often used in children who have an established preexisting serious brain injury or malformation or who do not tolerate or respond to ACTH.