Cerebellar vermis lesions and tumours of the fourth ventricle in patients with positional and positioning vertigo and nystagmus.

Positional and positioning vertigo and nystagmus syndromes are usually due to peripheral vestibular dysfunction. The most common form is benign paroxysmal positioning. In this paper, we discuss more serious aetiologies in the differential diagnosis for patients presenting with a history suggestive of benign paroxysmal positioning vertigo. We draw attention to the diagnosis of cerebellar vermis lesions and tumours of the fourth ventricle by presenting two cases of patients with positional nystagmus of so called benign paroxysmal type. We review the literature on positional nystagmus, highlighting key findings on history and physical examination to aid in the correct diagnosis of benign paroxysmal positioning vertigo, and to differentiate it from the rare yet sinister central aetiologies that can present with positional vertigo of the benign positional type. This is with the aim to avoid over-investigating a common presentation without missing a serious diagnosis.