Background <p>Benign paroxysmal positional vertigo (BPPV) is by far the most frequent cause of positional nystagmus (PN). However, PN may also be encountered in central lesions. In this case report we describe a patient with isolated positional vertigo and central PN which mimicked a lateral-canal cupulithiasis, including initial response to liberation maneuvers.</p> Case Description <p>A 44-year-old male patient reported new-onset position-dependent vertigo with nausea and gait-imbalance for 10 days. During supine roll testing for the lateral semicircular canals, he showed a persistent apogeotropic PN (being more intense left-ear-down) accompanied by moderate vertigo. Except for the PN, the neurologic examination was normal. He received a diagnosis of a apogeotropic-variant right-lateral canal BPPV and responded well to a Gufoni maneuver (nose-up). However, on follow-up, apogeotropic PN showed-up again, converted into a geotropic variant after a Barbecue-liberation maneuver, and then disappeared. Due to the re-emergence of the initial PN on the second follow-up consult, a brain-MRI was requested, disclosing disseminated infra- and supratentorial cystic brain metastases. The largest mass compressed midline cerebellar structures. Urgent surgical resection revealed a histopathologic diagnosis of an adeno-carcinoma of the lung.</p> Discussion <p>Short-lasting responses to liberation maneuvers may also be seen in CPN, mimicking the response-pattern expected in BPPV cases. Thus, response to treatment must be validated on a follow-up consultation. Pressure by a cystic cerebellar mass lesion on the nodulus and uvula that varies with changing head-position relative to gravity, resulting in adaptational changes in PN direction and intensity could explain our findings.</p>