The paroxysmal features and neurology of alternating hemiplegia of childhood are remarkable and fascinating. In their original report, Verret and Steele (128) described eight cases from the Hospital for Sick Children, Toronto; they regarded the condition as infantile onset complicated migraine. Casaer (129) only managed to include twelve cases in a multicenter European flunarizine trial. Since then, ten patients were reported from Montreal (130), a further twenty-two patients from Aicardi's group in Paris (131), and most recently forty-four patients from Boston (132). These and other figures suggest that the condition has in the past been both underdiagnosed and underreported.
The general features are well known to all pedi-atric neurologists, with attacks of flaccid hemiplegia on one or both sides, beginning in the first 18 months of life. This is associated with autonomic phenomena and the gradual appearance of developmental delay unsteadiness and a degree of choreoathetosis. Actually, paroxysmal hemiplegia is not the first symptom and usually the first hemiplegic attack is not noticed until after the age of 6 months or considerably later. The initial manifestations begin before the age of 6 months, often in the neonatal period. The earliest manifestation is commonly a disorder of eye movements, in particular nystagmus and strabismus. The nystagmus is paroxysmal and frequently unilateral. The strabismus may be paroxysmal also, and associated with signs of transitory internuclear ophthalmoplegia (133). Tonic and dystonic episodes also appear early in infancy, well before the first hemiplegic attack. These consist of predominantly brief and perhaps clustered tonic attacks that may be easily be mistaken for epileptic tonic seizures. These stiffenings are commonly unilateral, with some resemblance to the asymmetric tonic neck reflex, which may also be bilateral, with a degree of opisthotonus and up-deviation of the eyes. Pallor and crying or screaming and general misery tend to accompany these attacks.
Once hemiplegic episodes begin they may affect one or both sides [or even one upper limb and a contralateral lower limb as in case 3 of Casaer (129)]. Bilat eral hemiplegia is associated particularly with autonomic phenomena and drooling.
Some sort of trigger precedes attacks in most affected children. Emotional factors—excitement, bright lights, and bathing, including hot baths—are reported. The frequency of bathing as a trigger (in the bathroom, not in the sea) is probably underreported— in one family [case 3, Casaer, (129)] this regular trigger was not recognized until the child was 15 years old.
Developmental delay, ataxia, and persistent choreoathetosis develop in the majority of children, and a few develop migraine with aura (case 3, Casaer ; Silver and Andermann ).
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