LAUSR

Some 30–50% of vertigo and dizziness symptoms cannot be explained by vestibular deficit or organic illness. They show co-morbidity with psychiatric disorders, i.e., anxiety and phobic disorders [1], illustrated in the concept of phobic postural vertigo (PPV) [2] describing patients with postural dizziness and subjective instability of stance and gait without pathological findings on otoneurological examination, vestibular, and balance tests. PPV exacerbates during perceptional stimuli and in social situations. The association between vertigo/dizziness and anxiety may be explained by neuroanatomical connections between the vestibular system and neuronal pathways modulated by monoaminergic influences [3]. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that modulates cortical neuroplasticity. Anodal stimulation of the left dorsolateral prefrontal cortex (DLPFC) improves cognitive control over negative stimuli such as anxiety and symptoms of psychiatric disorders, e.g., depression [4]. Currently, there is one case study reporting on tDCS in generalized anxiety disorder [5]. We hypothesized that tDCS can modulate PPV symptoms by strengthening cognitive control over fronto-limbic connections. Possible neurophysiological and neuroanatomical explanations of the effects might be (1) unspecific network changes in deeper frontal and subgenual regions [6, 7]; (2) shared neuroanatomical links of vestibular system and neural circuits of anxiety and depression [8, 9]; or (3) side and mode of stimulation, leading to differential effects in the laterality of the functional organization [10]. Eight outpatients (three female, five male) of the German Center for Vertigo and Balance Disorders IFBLMU gave written informed consent for this open label pilot study as a precursor of a randomized placebo controlled clinical trial which has been acknowledged by the local ethics committee. Inclusion criteria were pertinent postitives in the medical history, supporting evidence from physical examinations and laboratory testing (normal findings on otoneurological examination and vestibular and balance tests), and symptom stability for at least 2 months. Five patients showed anxious control of posture. No one had a history of drug intake, brain injury, epilepsy, severe somatic disorders, or dermatologic disease. One patient was smoker, and two were suffering from migraine without aura (no long-term medication). One patient was treated with amitriptyline, two were undergoing psychotherapy, and all interventions were longer than 2 months. No patient received further medications. tDCS (anode: left DLPFC; cathode: right supraorbital; sponge size 35 cm2; five stimulations in 5 days; 2 mA, 30 min, 15 s fadein/fade-out) was performed with an Eldith DC stimulator (neuroConn GmbH, Ilmenau, Germany). All patients were informed to receive active stimulation; there was no sham condition. For assessment, Edinburgh Handedness Test (EHT), Vertigo Symptom Scale (VSS), Dizziness Handicap Inventory Ulrich Palm and Valerie Kirsch are contributed equally.