The aim of this paper is to report one case of dizziness caused by antiphespholipid syndrome (APS) misdiagnosed as conversion disorder. The patient was a 41-year-old woman. She began to complain of dizziness during her work at the age of 38, when she became busy with her task. She visited the out patient clinic of otolaryngology, but her otoneurological study and MRI of the brain were found to be normal. Her dizziness was not improving. She fe]t depressive reactively by the symptom. Visiting

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... out patient clinic of psychiatry, $he was diagnesed as "conversion disorder" causecl by psychological stress due to her business. Although she took some medicine prescribed by the clinic, her dizziness was not improving. Her neurological examination at our clinic showed left central facial nerve palsy and left central hypoglossal nerve palsy. Tz weighted MRI of the brain showed bi-parietal rnultiple spotty high intensity lesion and small rounded high intensity ]esion in the right posterior Iimb of internal capsula-globus pallidus. Left facial nerve palsy and hypoglossal nerve palsy were also considered to be originated from ischemia of right posterior ]imb of internal capsula. MR angiography showed irregular wall of left internal cervical artery. Blood test showed prolonged APTT and positive anti-Ca]diolipine-f92 GPI antibody. Psychelogical assessment by Zung's self-rating depres$ion scale (SDS) showed her depression was mild, which meant that ['conversion disorder" was denied, We diagnesed her as primary APS, and considered that her dizziness was caused by ischemia of ventral posterior lateral nucleus and ventral posterior inferior nucleus which was central vestibular tract jn right thalamus. This ischemia was one of the APS's symptoms.