By: Nicholas Parekh
What are infantile spasms?
Infantile spasm syndrome (ISs), or more commonly West syndrome, is a rare epileptic
disorder that appears during the early stages of infancy. It is characterized by short tonic seizures
called “spasms” that last for only a couple of seconds and occur in clusters. During these spasms,
the baby’s legs typically curl toward the trunk while their arms may also curl or extend outward.
The baby may also stare blankly during the seizure. Clusters of spasms typically occur soon after
the infant wakes up or before falling asleep.
While West syndrome is relatively easy to diagnose based on the aforementioned
symptoms, pinpointing the exact cause is difficult. The disorder is multi-faceted with causes
ranging from metabolic to structural. There is evidence that many patients suffering from West
Syndrome are genetically predisposed to it. Multiple case studies describe identical twins having
their first spasm on the same day within minutes to hours of each other. Since identical twins
have identical genomes, the same gene or group of genes is likely activated by an environmental
trigger. Furthermore, many studies have found genetic mutations associated with West Syndrome
in a large proportion of patients.
Genes provide the “blueprint” to life and mutations in them may manifest in different
ways to cause West Syndrome. For example, mutations in genes essential to the function of
GABAergic (activated by or releasing GABA, the primary inhibitory neurotransmitter in the
brain responsible for “calming” it) neurons can result in increased brain excitability, or electrical
activity, and have been associated with the development of West Syndrome. Seizures result from
excessive brain excitability and synchronized electrical activity in large portions of the brain.
Genetic mutations may also result in structural abnormalities in the brain such as
hemimegalencephaly, a rare condition where one hemisphere of the brain is larger than the other,
which can promote the development of seizure disorders like West Syndrome. Interestingly,
researchers discovered that some mutations associated with decreased GABAergic neuron
function and infantile spasms are also linked to lissencephaly, a condition where the brain
appears to be smooth and lacks the typical folds and grooves.
Finally, there is an emerging link between Down Syndrome and ISs. Approximately 1 to
13% of all people with Down Syndrome have some form of epilepsy, with a large proportion
being ISs (6 to 32%). The exact reason for this is unknown.
Diagnosis
West Syndrome is usually diagnosed by the presence of a triad of symptoms: infantile
spasms, hypsarrhythmia, and developmental delay/regression. Infantile spasms usually begin
around 4-9 months of age with the average age of onset being 6 months. However, they may
sometimes be subtle and hard to discern from normal behavior or other epileptic disorders.
Hypsarrhythmia is the pattern of brain waves found in patients with ISs between spasms.
It is characterized by high amplitude waves and spikes that lack a clear pattern or rhythmicity. A
neurologist records the brain electrical activity of a patient with an electroencephalogram (EEG)
to look for this pattern.
After the patient is diagnosed with West Syndrome, the neurologist may order tests to
determine a potential cause of the seizures. For example, magnetic resonance imaging (MRI)
may be used to look for structural abnormalities in the brain which may have promoted the
development of the disorder.
Treatment
Quick diagnosis and treatment of West Syndrome are critical for mitigating the damage to
the infant’s developing brain. Unchecked, the disorder can lead to permanent intellectual
disability and predispose the individual toward developing other epileptic disorders.
West Syndrome is first treated through the administration of adrenocorticotropic hormone
(ACTH), which promotes the release of corticosteroids like cortisol from the adrenal cortex, or
prednisolone, a synthetic corticosteroid. Both serve to reduce inflammation in the brain that may
be contributing to infantile spasms. Sometimes corticosteroid treatment is combined with
vigabatrin, an anti-epileptic drug. However, the use of this drug must be closely monitored as it
has been shown to cause retinal damage and permanent vision loss in some patients. Like other
forms of epilepsy, the ketogenic diet (a diet low in carbs and high in fats) has been shown to
improve symptoms in some patients and may be a good alternative to hormonal and drug
therapy. Surgery is rarely prescribed unless the cause of the spasms can be identified with a
specific part of the brain.
Sources
Pavone, Piero et al. “West syndrome: a comprehensive review.” Neurological sciences : official
journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology
vol. 41,12 (2020): 3547-3562. doi:10.1007/s10072-020-04600-5
