Diffusion tensor magnetic resonance imaging DTI

Authors: Volker A Coenen Kristin Kieselbach Irina Mader Peter C Reinacher

Publish Date: 2015/02/05

Volume: 157, Issue: 4, Pages: 739-741

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Abstract

Chronic pain syndromes pose a challenge for interdisciplinary teams of pain specialists We report a patient who presented with a neuropathic trigeminal pain syndrome after repeated resection of an epidermoid tumour involving the trigeminal ganglion Multiple therapeutic approaches—including chronic motor cortex stimulation intrathecal drug application and deep brain stimulation DBS to the periventricular/periaqueductal grey and sensory thalamus—did not lead to a sustained relief of pain with a persistent rating of 79 on the visual analogue scale VAS A magnetic resonance imaging MRI scan was suspicious for a malposition of the previously implanted clinically nonfunctional DBS electrodes The DBS system was completely removed surgically The patient underwent diffusion tensor magnetic resonance imaging DTI Imaging was performed on a clinical 3T MRI system Magnetom Trio Tim System 3 T Siemens Erlangen Germany DTI singleshot twodimensional SE EPI TR 10000 ms TE 94 ms diffusion values b = 0 s/mm2 and b = 1000 s/mm2 diffusion directions 61 slice count 69 voxel size 20 × 20 × 20 mm3 acquisition time 1140 min Deformation correction of the EPI sequence according to Zaitsev et al 1 DTI tractography StealthVizDTI system Medtronic Navigation Louisville USA FA level 02 minimal fibre length 10 mm seed density 50 maximal fibre cutoff angle 50° Tractography as shown here used the MCP coordinates of the previous removed and newly implanted electrodes Threedimensional visualisation and rendering of tracked fibres were performed with Amira Konrad Zuse Zemtrum Berlin Germany and Visualization Sciences Group SAS Bordeaux France electric stimulation as previously described 2At the day after imaging two DBS electrodes were implanted stereotactically assisted with the DTI technology MCP coordinates crosschecked with DTI fibretracking results VCP laterality 11 mm 2mm anterior to PC verticality at level of ACPC plane PVG/PAG 5mm laterality 2mm anterior PC verticality at level of ACPC planea–c Deep brain stimulation DBS electrode positions postoperative computed tomography superimposed onto preoperative T2weighted MRI scans a axial view at the level of the intercommissural plane b coronal view c parasagittal view Blue arrowheads in a and c indicate previous implantation site of a DBS electrode removed A second electrode from a previous operation removed was located intraventricularly its tract site is not discernible d e Results from diffusion tensor imaging DTI fibretracking analysis combined with individual electric field simulation studies d unsuccessful previous treatment with two DBS electrodes e successful stimulation attempt over VCP and PAG DBS electrodes now reaching the medial blue MPNS and lateral pink ML systems acg anterior cingulate gyrus BA24 ATR anterior thalamic radiation IC/STP internal capsule/superior thalamic peduncle MPNS midline polysynaptic nociceptive system VCP nucleus ventralis caudalis posterior PVG/PAG periventricular grey/periaqueductal grey prcg precentral gyrus pcg postcentral gyrus sfg superior frontal gyrus TL/ML trigeminal lemniscus/medial lemniscusRecently DBS of the medial lemniscus in neuropathic pain after planning with tractography has been described 3 This line of investigation is likely to be fruitful in the light of successful stimulation of fibre tracts in other indications 2 4 5 6 The PAG/MPNS system is concerned with autonomic emotional and pain function In the context of DBS the connectivity of the PAG has been previously addressed utilising the DTI technology 7 8 In accordance with our own tractography studies 9 we are convinced that one previously described upstream projection 8 is confluent with the ATR system that at different levels midbrain PAG prefrontal cortex bednucleus of the stria terminalis connects with the MFB system Recently we have shown in a pilot study that direct stimulation of the MFB has strong antidepressive effects 6 Since PAG/PVG stimulation is located in a supposed connection hub of MFB/ATR it is possible that PAG stimulation alters the network balance of the ATR system in favour of the MFB system and diminishes emotional and somatic pain We have elaborated on the limitations of the DTI technology in our previous publications 2 4 5This report strengthens the idea of the application of the DTI tractography technology for DBS surgery in neuropathic and nociceptive pain and moreover for the thorough analysis of the electrode positions obtained with respect to the fibre systems which in addition to computation of somatic pain are concerned with emotion processing

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