Intensive sequential tDCS-rTMS over left DLPFC for biperiden dependence: A case report

Anticholinergic misuse is an underrecognized form of substance use disorder that can be difficult to treat. Noninvasive neuromodulation targeting prefrontal control networks has shown promise across substance use disorders but has not been described for biperiden dependence.

To report feasibility, tolerability, and preliminary clinical outcomes of a brief, intensive combined neuromodulation protocol; sequential anodal transcranial direct current stimulation (tDCS) followed by high frequency repetitive transcranial magnetic stimulation (rTMS) to the left dorsolateral prefrontal cortex (lDLPFC) in a single patient with refractory intramuscular biperiden dependence.

A 38-year-old man with schizoaffective disorder and borderline personality disorder self-administered up to 15 mg/day of intramuscular biperiden. He underwent an intensive course of neuromodulation consisting of two daily sessions (separated by a 20 minute break) for five consecutive days; each session comprised anodal tDCS to the lDLPFC (1.5 mA; 20 min 6 s) immediately followed by high frequency rTMS to the lDLPFC (15 Hz; 2400 pulses/session; 100% motor threshold). Addictive behavior was assessed with the Addictive Behavior Questionnaire (ABQ, 7DAS subscale) at baseline (T0), end of treatment (T1), and one month follow up (T2); daily vial consumption was recorded.

The 7DAS score decreased from 51 at T0 to 38 at T1, with a partial rebound to 46 at T2. Reported vial consumption fell from ≈3/day at baseline to 0/day by the end of treatment and remained between 0 and 1/day at one month. The intervention was well tolerated; only transient scalp discomfort and mild, short lived headaches were reported.

In this single case, a brief intensive sequential tDCS→rTMS protocol was feasible, well tolerated, and temporally associated with rapid reduction in biperiden use and improvement in addictive behavior scores. Findings are preliminary and hypothesis generating; controlled studies with objective toxicology, standardized stimulation parameters, and longer follow up are needed to evaluate efficacy, mechanisms, and durability.