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1. History
The syndrome of Alternating Hemiplegia of Childhood (AHC) was first described in 1971 by Drs. Verret and Steele, who reported the case of 8 children with hemiplegic migraine, of which three had “peculiar symptoms”. The A.H.C. syndrome was clearly indentified and distinguished from other related affections by a set of well-defined criteria (see below) and was confirmed by several reports. A meeting on the syndrome was held in Rome (1992). More recently at a symposium held in Seattle (USA-1997) several hypotheses on the possible causes of the syndrome were discussed and novel research methods were proposed (e.g. genetic studies). The cause(s) of the syndrome remain(s) unknown. Investigations performed up to know in several children (EEG, MRI, PET scan, SPECT, Caryotype, metabolic screening) have not clarified the etiology and mechanism of the condition. AHC is considered a rare disorder (about 5 cases listed in the Netherlands and 350 on a world scale).2. General Criteria for diagnosisThe criteria recognized as essential to carry the diagnosis are:
3. Remarks
4. Disease manifestations 4.1. Hemiplegic or unilateral hypertonic attacks Description: One side (upper or lower limb) becomes flaccid (hemiplegic) or on the contrary stiff with flexion or hyperextension (hypertonic). Very characteristic eye movements (jerks) are frequent (nystagmus). Frequency: all the children have paralytic episodes of variable duration, from a few minutes to several days. The intensity of symptoms may be fluctuating and they disappear temporarily during sleep. Precipitating factors may be noted. They include emotions (joy or fear), physical efforts or temperature changes. The effect of sleep on attacks is a very important feature of the condition. 4.2. Hemiplegic or bilateral episodes Description: Such episodes involve the four limbs, either in succession (shifting hemiplegia) or from the start (quadriplegia) often associated with marked dystonic phenomena.. They are often associated with temporary loss of speech, abnormal eye movements, decreased awareness. Marked rigidity, crying and apnea are often present. Frequency and duration: Such episodes are less frequent than hemiplegic attacks. They often last for hours or days and recur after disappearing during sleep, spontaneous or induced. Some degree of deterioration may follow the most severe episodes. 4.3. Epileptic manifestations Present in some children only, they rarely occur during a hemiplegic episode. Most often they occur independently and require a specific antiepileptic treatment. 5. Consequences of the disease Motor development can be variably impaired. Walking is often delayed, hypotonia is usual and imperfect control of movements and/or parasitic movements (choreoathetosis, dystonia) develop in most cases. Cognitive development is usually but not always impaired. School difficulties are inevitable. Today very few children follow a normal schooling with adapted support. The majority of the children need education in specialized establishments (IMP, EMP, IMPRO type). 6. Behaviour Affected children may be unstable, aggressive or depressed. They suffer changes of mood, usually of short duration, and are often anxious. Such disturbances do not seem to be related to medical therapy but dependent on the disorders itself. Mood changes may be premonitory of one attack. 7. Management The medical follow-up and care aims at limiting the severity and intensity of attacks by a continuous treatment. So far Sibelium (flunarizine) seems to be the most effective, even though in most children, it does not suppress the attacks and only moderately decreases the frequency of episodes. Other therapies are being currently studied. Careful follow-up and remedial help (physiotherapie, speech therapy, occupational therapy) are very important. |
