Differential diagnosis of vertigo--combined galvanic test and MRI.

Differential diagnosis of the disease entities of vertigo are important in clinical investigations. Many concepts and procedures have been proposed for available diagnostic tests. Recent basic and clinical studies proved the efficacy and reliability of galvanic tests, including galvanic nystagmus test (GNT) and galvanic body sway test (GBST), emphasizing that the effects of galvanization are: 1) on the action potential in vestibular nerve and 2) on the resting discharge of the vestibular nerve. These suggest further that galvanic nystagmus reaction (GNT) is mainly a manifested reaction of the semicircular canal system, while galvanic body sway such as spinal reflexes (includ. GBST) are mainly a reaction of the otolithic system. The purpose of this paper is to review briefly the previous results of GBST in our laboratory; and to introduce a newly devised combined galvanic test, simultaneous recording of both GBST and GNT; and also introduce magnetic resonance imaging (MRI) of the brain including the cerebrum, cerebellum with brainstem relating the central vestibular system, both of which help us to make a more defined diagnosis of the central origin vertigo. On CGT of a normal subject, galvanic eye movements are constantly induced showing the initial eye deviation and the following main deviation during galvanization, on both eyes, which are almost similar and occur synchronously. Galvanic body sway is also induced well with individual components, as described in the previous papers. CGT of the cases with vertigo revealed abnormal response patterns in each disease.