Downbeat Nystagmus (DBN) is among the most common forms of centrally mediated positional provoked nystagmus. It may also be accompanied by a transient dizziness or vertigo. It is typically only seen in ears as the vertical component in an AC-BPPV or with stimulation (acoustic) of a Superior Canal Dehiscence.
Although vertigo is typically associated with CNS or acute labyrinthine lesions, numerous investigators have reported vertigo in cardiovascular disorders (Newman-Toker et al, 2008 and Jung et al, 2009). While DBN is most often linked to lesions within the Vestibulo-cerebellum it has recently been ascribed to cardiogenic causes (Choi et al, 2010). Choi et al, also cautions of the possibility of focal TIA within the vertebral or basilar artery.
A 78-year-old female is referred with complaints of positional dizziness. There was no precedent otologic/audiologic history or onset of focal neurological symptoms, other than those presented. MRI was read as “normal” but with the commonly reported age-related ischemic and atrophic changes. The patient is remarkable for a history of coronary artery disease, triple bypass and hypertension.
Modified Hallpike positioning (Roberts and Gans, 2008) was negative for a PC-BPPV response but provoked a non-transient DBN. The nystagmus was also seen in the supine position (SEE VIDEO), but not in side-laying positions. The referring primary care physician was contacted with a recommendation for neurology consult and correlation with previously obtained studies.
- The brain moves the eyes not the ears.
- Many patients are referred for “positional dizziness” but may have central or cardiogenic mediated symptoms including; non-transient vertigo, nystagmus, nausea etc.
- Beware of labeling patients with “non-classic” BPPV. If Canalith repositioning does not clear the involved ear, then it is highly unlikely you are dealing with an ear. AC-BPPV is very rare (1-3%) and is statistically and anatomically unlikely the cause of a non-fatiguing DBN.