Locating the ventral intermediate thalamic nucleus for deep brain stimulation surgery: analysis of a case series comparing CT and MR targeting.

Background: Deep brain stimulation (DBS) surgery targeting the ventral intermediate thalamic nucleus (Vim) has proven efficacy in the treatment of tremor.

Aims: The primary aim is to investigate whether there is a statistically significant difference in patient outcomes when CT-guided targeting of the Vim is compared with MRI-guided targeting.

Methods: This is a retrospective study concerning patients undergoing Vim-targeted DBS at the Department of Neurosurgery, Royal Victoria Infirmary in Newcastle (9 August 2012 to 4 January 2019). Fahn-Tolosa-Marin Tremor Scale (FTM TS) and EQ-5D scores were collected from patient notes. Statistical analysis was performed using IBM SPSS Statistics Version 24. Independent samples -tests were used to compare means.

Results: Independent samples -test did not reveal a statistically significant difference between CT ( = 10; FTM TS mean = 65.40, SD = 11.40; EQ-5D mean = 39.50, SD = 17.87) and MR ( = 7; FTM TS mean = 60.57, SD = 7.50; EQ-5D mean = 32.14, SD = 9.94) groups in pre-surgery FTM TS (t(15) = 0.977,  = 0.344) and EQ-5D (t(15) = 0.982,  = 0.342) scores. No statistically significant difference between the CT (FTM TS mean = 24.12, SD = 20.47; EQ-5D mean = 75.56, SD = 15.63) and MR (FTM TS mean = 22.86, SD = 6.72; EQ-5D mean = 70.43, SD = 15.48) groups was revealed at 1 year assessment of FTM TS (t(14) = 0.155,  = 0.879) and EQ-5D (t(14) = 0.654,  = 0.524). The median difference between pre- and post-surgery FTM TS and EQ-5D scores in the CT group at 1 year was 43.00 and 35.00, respectively. The MR patient group median difference in pre- and post-surgery at 1 year was 35.00 and 35.00 respectively.

Conclusion: No statistically significant difference between CT and MR image-guided targeting patient groups was detected.