Histological Study On The Thalamic Lesion After Gamma Thalamotomy. A Case Report

Keywords: thalamotomy, radiobiology, gamma knife, thalamus, tremor

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      He had Gamma Thalamotomy for the movement disorders of parkinsonism in 2006, and died 2 years later by pneumonia. At autopsie, histological examination was performed to the thalamic lesion.
     Clinico-pathological study was carried out in a case with Corticobasal Degeneration.
     Since at the age of 69, this gentle man has been suffering from unknown involuntary movement consisted of mixture of tremor, choreic movement, etc. The movement disorders gradually increased,so at 71 year old, he visited Tokyo Rinkai Hospital and treated by clonazepam for tremor. Two years later, his myoclonic tremor and rigidity increased further and kept on wheel chair. 
     As medical treatment seemed to be difficult, he was sent to Hidaka Hospital for stereotactic treatment. Before the operation, EMG examination revealed high amplitude irregular grouping disharge during a small intentional movement of the limbs, mainly in the right arm. Passive movement of the limb provoked cogwheel like stretch reflex with 7 Hz grouped discharge. On April 20, 2006, left gamma thalamotomy was conducted. As usually, one shot of 130 Gy was irradiated to the left thalamic ventralis intermedius (Vim) nucleus at about 45 % of the thalamic length, using 4 mm collimator. After the operation, for about two years, his right hand involuntary movement reduced milder. In April 2008, because of accidental mis swallowing, he was hospitalized as an emergency case in Rinkai Hospital, but unfortunately passed away.
     KB and HE stained thalamic sections revealed a necrotic lesion of about 2mm diameter at the lateral border of the Vim nucleus surrounded by faint colored zone, which contains no neurons but reactive astrocytes and macropahages with many small vessels. Other pathological changes than the thalamic lesion showed nerve cell loss and gliosis in the midbrain and pallidum. Also many ballooned neurons were found in the cerebral corex. Especially in the frontal cortex, there were many neurofibrillary tangles and astrocytic plaques which were characteristics of CBD.
     This is a retrospective study.
     Histological examination 2 years after gamma thalamotomy demonstrated a round lesion at the intended site where no neurons but reactive astrocytes and macropahages.


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