transcraneal

Transcraneal refers to noninvasive techniques and measurements that interact with brain tissue through the skull. The goal is to modulate neural activity, map cortical function, or assess cerebral physiology without surgery. These methods are used in neuroscience research and clinical practice with varying evidence across indications.

Common transcraneal methods include transcranial magnetic stimulation (TMS), which uses a scalp coil to generate magnetic fields that induce currents in the cortex. Repetitive TMS (rTMS) and theta-burst protocols are used to produce lasting changes in excitability and have applications in depression and other conditions. Transcranial direct current stimulation (tDCS) applies a weak direct current via scalp electrodes to modulate neuronal excitability. Transcranial alternating current stimulation (tACS) uses alternating currents to influence brain rhythms. Transcranial focused ultrasound (tFUS) and related ultrasound approaches are experimental means to modulate activity noninvasively. Transcranial Doppler (TCD) ultrasound measures blood flow velocity in intracranial vessels for monitoring cerebral hemodynamics.

Safety and limitations vary by modality. TMS carries a rare risk of seizures; tDCS is generally well tolerated with mild scalp sensations or irritation; ultrasound methods require careful control of energy delivery to prevent heating. Across techniques, depth and focality can be limited, and effects can depend on skull thickness, anatomy, and state of the subject. Transcraneal methods are typically used as adjuncts to established treatments and in controlled research settings, with ongoing evaluation of efficacy, safety, and standardization.