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Positional vertigo and nystagmus without associated neurological symptoms and signs are characteristic features of benign paroxysmal positional vertigo (BPPV). Although positional nystagmus may occur with caudal cerebellar infarction including the nodulus, positional nystagmus is usually associated with other neurological signs such as spontaneous or gaze-evoked nystagmus, perverted head-shaking nystagmus, cerebellar dysmetria, or severe gait ataxia with falling. We present a patient with nodular infarction who had positional vertigo with nystagmus as a sole manifestation. Video-oculography showed apogeotropic positional horizontal nystagmus during head turning while supine, which was consistent with apogeotropic BPPV involving the horizontal canal. MRI disclosed acute infarct in the nodulus. Nodulus infarction should be considered in a patient with positional nystagmus, especially when the presenting symptoms and signs are consistent with BPPV involving the horizontal canal. [ABSTRACT FROM AUTHOR]

The caloric test is probably the most widely used clinical test of vestibular function. A unilateral decrease in response to cold and warm water reliably indicates a unilateral peripheral vestibular lesion. Central signs on caloric testing are less common but important to recognize because they are often associated with lesions of the brainstem. We describe a patient with a tumor originating in the floor of the fourth ventricle who presented with premature reversal after cold stimulation on one side and perverted nystagmus after cold stimulation of the other side. [ABSTRACT FROM AUTHOR]