Alternating hemiplegia of childhood: report of a case having a long history.

We examined a patient with alternating hemiplegia of childhood (AHC) who had over a 23-year history of AHC to investigate the origin of the neurological deterioration with increasing age. Hemiplegic attacks had occurred consistently at a frequency of a few per week since infancy, and he first experienced attacks of cerebellar ataxia at the age of 23 years. Intellectual impairment, dysarthria, dystonic posturing, and a wide-based gait had been slowly progressive, but they had been stable since he turned twenty. The electromyographic response to transcranial magnetic stimulation was normal between attacks and showed reversible alteration during an attack. MRI revealed slight dilatation of the lateral ventricles, and MR angiography showed normal cerebral blood flow. Proton MR spectroscopy between attacks showed normal peak area ratios for N-acetyl groups, choline-containing compounds, and creatine and phosphocreatine, and it also demonstrated no lactic peak. 123I-IMP SPECT between attacks demonstrated diffuse cerebral hypoperfusion despite no evidence of ischemic change in the above MR study. These results suggest that the slowly progressive neurological deficits are due to the primary underlying pathology rather than the secondary neuronal loss as a result of frequent ischemic attacks.