On videonystagmography, a patient performs a visually guided tracking task during caloric-induced nystagmus. The examiner notes complete failure of fixation suppression of the evoked nystagmus. This finding localises the lesion to:
- A The peripheral vestibular apparatus of the irrigated ear
- B The vestibular nucleus complex in the brainstem
- C The cerebellum, particularly the flocculonodular lobe ✓
- D The medial longitudinal fasciculus
Correct answer: C. The cerebellum, particularly the flocculonodular lobe
Explanation
Visual fixation suppresses caloric nystagmus through cerebellar pathways involving the flocculus. Failure of fixation suppression is therefore a localising sign of cerebellar disease and is considered one of the strongest VNG indicators of a central lesion. Peripheral lesions show normal suppression, and a brainstem vestibular nucleus lesion alone does not abolish fixation suppression, killing options A, B and D.
Reference: Cummings Otolaryngology: Head and Neck Surgery, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.