<s>[INST] context: Pathologic vertigois generally classified as peripheral (labyrinthine) or central (brainstem or cerebellum).
The clinical presentation in this case is most consistent with central vertigo. Positional (especially horizontal) nystagmus (to-and-fro oscillation of the eyes) is common in vertigo of central origin,but absent or uncommon in peripheral vertigo.
The chronicity of the vertigo is characteristic of central vertigo, whereas the symptoms of peripheral vertigo generally have a finite duration and may be recurring.
Tinnitus and/or deafness is often present in peripheral vertigo, but absent in central vertigo.
The flocculonodular lobe, or vestibulocerebellum, is connected to the vestibular nuclei and participates in the control of balance and eye movements, particularly changes in the vestibuloocular reflex (VOR), which serves to maintain visual stability during head movement; a lesion of this area of the cerebellum may result in vertigo and nystagmus, whereas the spinocerebellum is involved in the coordination of limb movement. [/INST] question: A 27-year-old patient with a chief complaint of mild vertigo of 3-months duration is seen by a neurologist. Examination reveals a positional (horizontal and vertical) nystagmus that is bidirectional. The patient reports the absence of tinnitus. Which of the following is the most likely etiology of the vertigo? | options: A: Labyrinthitis B: Ménière’s syndrome C: Lesion of the flocculonodular lobe of the cerebellum D: Lesion of the spinocerebellum | answer: C </s>