References1. Leigh RJ, Robinson DA, Zee DS. A hypothetical explanation for periodic alternating nystagmus: instability in the optokinetic-vestibular system. Ann NY Acad Sci 1981;374:619 -635. 2. Baloh RW, Honrubia V, Konrad HR. Periodic alternating nystagmus. Brain 1976;99:11-26. 3. Davis DG, Smith JL. Periodic alternating nystagmus: a report of eight cases. Am J Ophthalmol 1971;72:757-762. 4. Keane JR. Periodic alternating nystagmus with downward beating nystagmus: a clinicoanatomical case study of multiple sclerosis. Arch Neurol 1974;30:399 -402. 5. Dow ER, Anastasio TJ. Induction of periodic alternating nystagmus in intact goldfish by sinusoidal rotation. Neuroreport 1997;8:2755-2759. 6. Wearne S, Raphan T, Cohen B. Control of spatial orientation of the angular vestibuloocular reflex by the nodulus and uvula.Dentatorubral pallidoluysian atrophy (DRPLA) is an autosomal dominant disease that has a wide variety of clinical symptoms. 1 There is a correlation between age at onset and clinical symptoms. Progressive myoclonus epilepsy (PME) is a usual feature of juvenile DRPLA; but late adult DRPLA patients usually experience cerebellar ataxia and hyperkinetic involuntary movements such as choreoathetosis, often without myoclonus or epilepsy. 2 We report two unrelated patients with infantile DRPLA. Patient 1. The patient is a 4-year-old boy and the second child of healthy, nonconsanguineous Japanese parents without a family history of neurologic diseases. His father is 39 years old and his mother is 35 years old. He has a healthy 8-year-old brother. There were no major problems in the neonatal periods. He developed normally until age 6 months when his mother noticed decreased activity. At age 1 year, he could stand with support; but he began to regress slowly and became irritable. At age 2 years, he had difficulty controlling his head and swallowing, sometimes showing dystonic posture. Choreoathetosis of the limbs appeared and became prominent. At age 2 years 7 months, he had tonic convulsions. Various antiepileptic drugs did not control the convulsions.He was no longer able to fix or follow, but had light perception and normal optic fundus. Nystagmus was not noted. Muscle tone was variable, and deep tendon reflexes were exaggerated. Plantar response was absent. Oral dyskinesia, severe choreoathetosis, and dystonia were continuously seen. Myoclonus was not present.Laboratory examination including lysosomal enzyme activities, organic and amino acid analysis, and the level of lactate and pyruvate, were unremarkable. Histologic examination of the biopsied skin and muscle revealed no abnormalities.MRI of the brain showed atrophy of the cerebrum and cerebellum, brain stem, and delayed myelination ( figure, A and B).Patient 2. The patient is a 2-year-old girl and the second child of healthy, nonconsanguineous Japanese parents. Her father is 46 years old and her mother is 37 years old. Her 10-year-old brother has epilepsy and mild mental retardation. Her birth and development up to age 4 months were normal, but she could no...
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