Pontine lesion in opsoclonus-myoclonus syndrome shown by MRI

SUMMARY Two patients with opsoclonus-myoclonus syndrome are reported whose magnetic resonance imaging (MRI) showed brain stem lesions. Both patients developed the opsoclonus-myoclonus syndrome after an upper respiratory illness. One case had visual hallucinations during the course of illness and MRI revealed a focal lesion in the pons involving the junction of basis and tegmentum. MRI of the second case showed a focal lesion at the upper pontine tegmentum. Opsoclonus, originally described by Orzechowski ' is a rapid, irregular and chaotic eye movement that occurs in all directions. Opsoclonus associated with general-ised myoclonus is well known as the opsoclonus-myoclonus syndrome, which occurs in association with viral and bacterial infections of the central nervous system, postinfectious encephalitis, intra-cranial tumours, hydrocephalus, thalamic haemorr-hage, multiple sclerosis, and toxic encephalopathies.2 The site of the responsible lesion, however, has been a matter of controversy; cerebellum,"5 midbrain,67 thalamus and midbrain,8 have been suggested, as well as a combination of several sites in the central nervous system.2 We report two recent cases of opsoclonus-myoclonus syndrome whose magnetic resonance imaging (MRI) showed pontine tegmentum lesions. We will discuss the pathophysiology of opsoclonus and myoclonus based on the MRI findings. This appears to be the first report of MRI in patients with opsoclonus-myoclonus syndrome. Case reports Case 1: A 73 year old male, whose chief complaint was body tremulousness and oscillopsia. Past history and famil