Chapter 28: Infantile Spasms and West Syndrome

OVERVIEW

In 1841, Dr. William J. West penned a letter to Lancet in which he described an unusual condition in his 4-month-old son, James, that was characterized by "… slight bobbings of the head forward"…which "… increased in frequency, and at length became so powerful, as to cause a compete heaving of the head forward toward his knees, and then immediately relaxing in an upright position. … these bowings and relaxings would be repeated alternately at intervals of a few seconds, and repeated from ten to twenty or more times at each attack, which attack would not continue more than two or three minutes; he sometimes has two, three, or more attacks in the day …." Dr. West went on to describe a reduction in a developmental trajectory in his child that was normal prior to the onset of these events: he states that since the onset of the spells his son "… neither possesses the intellectual vivacity, or the power of moving his limbs, of a child of his age." This remarkable letter, now over 160 years old, remains the most eloquent clinical description of what we now know as infantile spasms. It describes the relentless nature of the condition, the early age of onset, the classical clinical presentation, and the developmental regression associated with infantile spasms.¹

In 1952, Gibbs and Gibbs² described the classical interictal electroencephalographic (EEG) pattern associated with infantile spasms, called hypsarrhythmia. This EEG is characterized by a chaotic and disorganized background of high-voltage, asynchronous spike and slow-wave activity. Although hypsarrhythmia is certainly characteristic of infantile spasms, it should be remembered that the EEG findings in infantile spasms are dynamic and hypsarrhythmia is but a point on a continuum of epileptiform changes observed on the EEG in this disorder. Therefore, the absence of hypsarrhythmia in the presence of clinical evidence of infantile spasms and other types of epileptiform abnormalities on the EEG does not in any way exclude the diagnosis of infantile spasms.

The term West Syndrome refers to an age-related triad of epileptic spasms, developmental regression, and hypsarrhythmia on EEG. Although this triad may be used synonymously with infantile spasms, the latter should refer strictly to the massive myoclonus because infantile spasms may occur in the absence of either hypsarrhythmia or mental retardation. The incidence of infantile spasm is 1 per 2000–4000 live births^3,4 and the prevalence rate is 0.15–0.2 per 1000 children of age 10 years or younger.⁵ It is slightly more common in males, accounting for about 60% of cases, and a family history exists in 3%–6%.

CLINICAL FEATURES

CLINICAL MANIFESTATIONS

The epileptic syndrome of infantile spasms begins in infancy, with initial onset mostly between 3 and 7 months of life in more than 50% of cases. Over 90% of cases begin before 12 months of life.⁶