Objective: This study aimed to clarify the clinical features of these cases

Background: Several case reports have described electrical conduction abnormalities that were undetected by impedance measurements using deep brain stimulation (DBS) programmers; however, no larger case series have been reported.

Method: Seven patients with electrical conduction abnormalities that were undetected by the DBS programmer were retrospectively reviewed. Abnormalities in these cases were confirmed by reopening the surgical site under general anesthesia and directly measuring the impedance by connecting the electrode to an impedance tester under direct visibility.

Results: The mean postoperative period was 10.1±3.6 years, while the primary diseases were Parkinson’s disease in three patients and dystonia in four (including two with DYT-TOR1A and one with a GNAO1-related disorder). Unexplained symptom fluctuations were observed in six of the seven patients, acute to subacute symptom exacerbation in five, symptom asymmetry in five, and electric shock-like pain at the electrode insertion site in the head in two. Three patients showed abnormalities such as electrode bending on head radiographs. Although the DBS programmer-measured impedance values were normal in all cases, open surgical impedance measurement was challenging in six due to unstable or high values, and one showed a short circuit. Reoperation was performed in five cases, with symptom improvement in all patients.

Conclusion: Electrical conduction abnormalities cannot be ruled out even when no abnormalities are detected in the DBS programmer-measured impedance values. Clinical observations such as unexplained motor fluctuations, laterality, or imaging findings may warrant the consideration of invasive impedance measurements.

References: 1. Farris S, Giroux ML. Lead wire fracture associated with normal therapeutic impedance measurements in a patient with a Kinetra neurostimulator. Neuromodulation 2010; 13: 65-67.
2. Fernández FS, Alvarez Vega MA, Antuña Ramos A, Fernández González F, Lozano Aragoneses B. Lead fractures in deep brain stimulation during long-term follow-up. Parkinsons Dis 2010; 2010: 409356.
3. Ikezawa J, Yokochi F, Okiyama R, et al. Two cases of device troubles that could not be detected by the controller of deep brain stimulation. Funct Neurosurg 2019; 61: 79-86 (in Japanese)

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MDS Abstracts - https://www.mdsabstracts.org/abstract/circuit-malfunctions-undetectable-by-dbs-programmers-role-of-intraoperative-direct-measurement-of-impedance/