Alternating hemiplegia of childhood: early characteristics and evolution of a neurodevelopmental syndrome

Absence of small-vessel abnormalities in alternating hemiplegia of childhood

OBJECTIVE

To investigate whether Japanese patients with alternating hemiplegia of childhood (AHC) have the similar small-vessel abnormalities in skin reported in European patients with AHC.

METHODS

Electron microscopic observation of biopsied skin specimens were carried out in six Japanese patients with AHC. All patients (aged 5-17, all boys) had been diagnosed with AHC through their typical clinical courses and symptoms.

RESULTS

No abnormal findings in both endothelial cells and smooth muscle cells in skin small-vessels were obtained in the present study, either in the five flunarizine responders or in the one non-responder.

CONCLUSIONS

From our observations, we hypothesized that there may be some subtypes of AHC. The diverse clinical courses in patients with AHC and the differing efficacy of flunarizine treatment could be explained because of the heterogeneity of AHC subtypes.

Evidence of a non-progressive course of alternating hemiplegia of childhood: study of a large cohort of children and adults

Alternating hemiplegia of childhood is a neurological disorder characterized by episodes of hemiplegia, various non-epileptic paroxysmal events and global neurological impairment. Characterization of the evolution and outcome into adulthood has not been sufficiently investigated. The goal of this study was to elucidate the natural history of alternating hemiplegia within a large cohort of 157 patients, as part of the European Network for Research on Alternating Hemiplegia project. A questionnaire was formulated to determine the severity of both paroxysmal and global neurological impairment and address progression of the disorder by allocating data to specific age epochs up to and over 24 years of age. Patients in early age groups were consistently present in subsequent later age groups and for each patient, data were collected for each corresponding age epoch. The study was based on predominantly retrospective and, for a period of 2 years, prospective data. At inclusion, patients were aged from 9 months to 52 years. The median age at diagnosis was 20 months. All patients experienced hemiplegic attacks; 86.5% reported episodes of bilateral weakness, 88% dystonic attacks, 53% epileptic seizures, 72% developed chorea and/or dystonia and 92% mental retardation. When data over the course of the illness were examined for the whole cohort, the severity of symptoms did not appear to change, with the exception of abnormal ocular movements and hypotonia that regressed, but did not disappear into adulthood (from 86 to 36% and 76 to 36%, respectively). No statistically significant correlation between a history of severe paroxysmal hemiplegic/dystonic episodes and a worse neurological outcome was identified. Seven patients died, some of whom experienced severe plegic attacks or epileptic seizures at the time of death. History of severe plegic/dystonic attacks was not found to be an aggravating factor for deceased patients. Our results provide evidence that the natural history of alternating hemiplegia is highly variable and unpredictable for individual patients. However, we did not find evidence to support a steadily progressive and degenerative course of the disorder when patients were analysed as a group. For a minority of patients, a risk of sudden death was associated with more severe neurological impairment. The European Network for Research on Alternating Hemiplegia Registry, validated by our study, includes all major neurological signs and symptoms of alternating hemiplegia and may thus be used as a precedent for the progressive inclusion and follow-up of patients as well as a reference for genetic studies and treatment trials.

Evolution of hemiplegic attacks and epileptic seizures in alternating hemiplegia of childhood

To delineate the evolution of non-epileptic and epileptic paroxysmal events in alternating hemiplegia of childhood (AHC), we reviewed clinical information of nine patients (4-40 years) with AHC. Paroxysmal abnormal ocular movements, head turning, and tonic, clonic, or myoclonic limb movements were the initial symptoms (birth-8m) in each patient. Ictal electroencephalography (EEG) of these episodes, as well as hemiplegic periods that accompanied these symptoms later in infancy showed unremarkable findings or generalized slow background activity. Presumptive epileptic seizures appeared at 2-16y in seven patients: generalized tonic, clonic, myoclonic, tonic-clonic, or complex partial seizures often accompanied by cyanosis or prolonged respiratory arrest. Ictal EEGs recorded in four patients revealed focal slow or fast activities during facial or limb twitching, and widespread sharp waves or polyspike-wave activities during clonic/myoclonic seizures. Four patients with neonatal disease onset showed lower psychomotor developmental achievements compared with other patients, and experienced repeated status epilepticus followed by progressive deterioration. Cerebellar atrophy and hippocampal high signal changes on magnetic resonance imaging were common to this group with severe phenotypes. Apart from the paroxysmal motor symptoms accompanying the hemiplegic episodes, many AHC patients suffer from true epilepsies during childhood. Status epilepticus in AHC is linked to severe outcome with psychomotor deterioration. The variations in clinical phenotypes may imply multiple causative genes for AHC. This variation should be considered while managing patients with this disorder.