Neurosurgeons Question Safety Claims for Staged Bilateral Lesioning in Parkinson’s Disease

A letter published in the Egyptian Journal of Neurosurgery raises methodological concerns about a recent study reporting that staged bilateral radiofrequency thalamotomy or pallidotomy is a safe and cost-effective alternative to deep brain stimulation for Parkinson’s disease. The original study, by El-Gretly and colleagues, described outcomes in fifteen patients with idiopathic Parkinson’s disease followed for up to 36 months, with reported sustained improvement in UPDRS-III scores, tremor, rigidity, gait, and speech.

The commenting authors, Assia Zanat, Nour Abu Shawish, Ali Karim, and Dua Jabbar, acknowledge that the reported outcomes are encouraging but argue that several design features make the study’s central conclusions difficult to support. Their letter, formatted as a correspondence to the editor, walks through four specific points where they believe the evidence does not yet justify the claim that staged bilateral lesioning matches deep brain stimulation in safety and efficacy.

The first and most fundamental concern is the absence of any comparator arm. All fifteen patients received open-label lesioning, with no sham procedure, medically managed comparison group, or deep brain stimulation group against which results could be benchmarked. In addition, the letter notes that UPDRS-III assessments do not appear to have been performed by raters blinded to treatment or to the timing of assessment.

This matters because expectation-driven improvement is well documented in surgical trials for Parkinson’s disease and can produce substantial early motor gains that are independent of the lesion itself. The letter cites the randomized deep brain stimulation trial by Deuschl and colleagues as an illustration of how much the apparent benefit of a novel surgical intervention can depend on which comparator is used. Without a comparator in the staged lesioning study, the commenters argue, it is difficult to separate the contribution of the lesion from non-specific surgical or expectation effects. They point out that the greatest gains in both treatment groups occurred at the six-month assessment, a pattern consistent with such non-specific effects.

The second concern addresses how patients were assigned to the two lesioning procedures. Target selection followed symptom phenotype: thalamotomy of the ventral intermediate nucleus for tremor-dominant disease, and pallidotomy of the internal globus pallidus for rigidity- and bradykinesia-dominant disease. The commenters describe this as clinically sound practice, but they emphasize that it means the thalamotomy and pallidotomy groups were, by design, different patient populations rather than randomly allocated ones.

This assignment scheme has direct consequences for one of the original study’s headline comparisons. The letter notes that the original authors reported pallidotomy achieving consistently lower UPDRS-III scores than thalamotomy at every postoperative time point. Because the groups differed in symptom profile from the outset, the commenters argue this reflects a comparison confounded by indication rather than a genuine treatment-effect difference. They recommend the finding be presented as a descriptive observation rather than an implied comparative advantage of one lesion target over the other.

The third point concerns anti-parkinsonian medication. Patients had medication withheld for only eight to twelve hours before surgery, yet the levodopa-equivalent daily dose does not appear to be reported at baseline or at any follow-up visit. Because medication titration over a 36-month period materially affects UPDRS-III trajectories, the commenters argue that reporting these doses would help clarify how much of the sustained benefit is attributable to the lesioning procedure itself rather than to concurrent pharmacological adjustment.

The fourth point identifies an apparent internal inconsistency in the reported speech outcomes. According to the letter, the text of the original study states that eight patients, or 53.3 percent, had normal speech postoperatively, while five patients, or 33.3 percent, had mild monotony. However, Graphic 5 in the same study reportedly shows 66.7 percent normal speech and 33.3 percent monotony. Neither pairing accounts for the full cohort of fifteen patients in the same way, and the commenters ask the original authors to clarify which figures are correct, arguing that resolving the discrepancy would strengthen confidence in the remaining reported outcomes.

The letter closes on a constructive note. The commenters commend the original authors for contributing valuable staged-lesioning data to a literature that remains dominated by deep brain stimulation studies, and they express hope that the observations will be useful for future prospective work in this area. Their overall position is not that the procedure is unsafe or ineffective, but that the study’s open-label, single-arm design and unreported medication data cannot yet distinguish a true lesion effect from expectation effects, indication bias, and pharmacological changes.

For readers following surgical options for Parkinson’s disease, the exchange highlights a recurring theme in functional neurosurgery: promising single-arm series, however carefully conducted, require randomized comparisons and blinded assessment before claims of equivalence to established treatments such as deep brain stimulation can be considered established. The letter was published as an open-access correspondence on 25 September 2026, commenting on an original article published on 25 August 2026.

Subject of Research: Methodological critique of a staged bilateral radiofrequency thalamotomy and pallidotomy study for Parkinson's disease

Article Title: Comment on “safety and efficacy of staged radiofrequency bilateral thalamotomy or pallidotomy in the treatment of Parkinson’s disease”

Article References: Zanat, A., Shawish, N. A., karim, A., & Jabbar, D. (2026). Comment on “safety and efficacy of staged radiofrequency bilateral thalamotomy or pallidotomy in the treatment of Parkinson’s disease”. Egyptian Journal of Neurosurgery, 41(1), Article 164. https://doi.org/10.1186/s41984-026-00672-1

Image Credits: AI Generated

DOI: 10.1186/s41984-026-00672-1

Keywords: Parkinson's disease, thalamotomy, pallidotomy, radiofrequency lesioning, deep brain stimulation, UPDRS-III, study design, confounding by indication, letter to the editor, functional neurosurgery, Comment, safety