Successful thalamotomy using external markers only.

The correlation between target centres for thalamotomy as determined by external markers or by the use of air studies was shown to be extremely close in eight patients undergoing pneumoencephalography. The site of the external markers was calculated in relation to the auriculoorbital and interaural planes, and a simple guide to aid in the placement of the markers was devised. Two cases are reported, one of parkinsonism and one of multiple sclerosis with intention tremor, in whom thalamotomy was carried out using external markers only. In both cases an excellent result was achieved. The value of this new method lies in the elimination of pneumoencephalography, the most unpleasant part of the operation of thalamotomy for movement disorders.