Metabolite and Electrode Alterations in Deep Brain Stimulation : Insights into Disease and Treatment
Bibliographic record
Abstract
Deep brain stimulation (DBS) alleviates symptoms in patients with Essential Tremor (ET) and Parkinson’s disease (PD). This thesis aimed to evaluate treatment aspects of DBS and the pathophysiology of ET and PD, focusing on lead displacement and metabolite evaluation of specific brain regions. In Paper I, DBS-lead position was registered the day after surgery and approximately one month later. Positional differences were computed in 23 patients (37 leads), and the volume of tissue activated (VTA) was simulated around the DBS-lead. In Paper II, ET patients underwent preoperative 3 T magnetic resonance spectroscopy (MRS) with voxels placed in the thalamus and cerebellum to assess GABA+ (inhibitory) and total glutamate + glutamine (Glx, excitatory). In ten ET and eleven PD patients, a 1.5 T MRS was performed before and after surgery (Papers III and IV, respectively) quantifying total N-acetylaspartate + N-acetylaspartyl- glutamate (tNA), total creatine + phosphocreatine (tCr), total choline + phosphocholine + glycerophosphocholine (tCho), and Glx. In ET, the thalamus, dentate nucleus, and cerebellar cortex were analyzed, and in PD, the thalamus and lentiform nucleus. The Essential Tremor Rating Scale (ETRS) in ET patients and the levodopa equivalent dose (LED) in PD patients were assessed pre- and postoperatively. An anterior and inferior displacement of both left and right leads was observed, and inferior displacement was associated with the anchoring technique. Despite VTA reduction due to temporal conductivity changes in the perielectrode space (PES) around the lead, the displacement resulted in additional brain areas being affected by stimulation. In patients with ET, the cerebellar GABA+/Glx ratio was positively correlated with the ETRS prior to surgery. Postoperatively, thalamic tNA concentrations were reduced in both ET and PD patients compared to preoperative levels, and were also lower than in healthy controls. In ET patients, the tNA reduction was localized to the targeted thalamus. No additional metabolite differences were observed. In conclusion, lead displacement resulted in new brain territories being stimulated, suggesting a clinical benefit of postponing stimulation until the electrode has stabilized. The correlation of the GABA+/Glx ratio with tremor severity supports cerebellar pathophysiology in ET and highlights the importance of inhibitory and excitatory balance in the cerebellum. The post-DBS decrease in thalamic tNA provides novel metabolite insight into a potential neuromodulatory mechanism that does not appear to be target- or disease specific.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".