Response to Letter by Johkura
We thank Dr Johkura for his interest in our recent study. We agree that distinguishing a central from a peripheral cause of dizziness in an individual patient can be challenging. A recent study demonstrates well that cerebellar infarction can closely mimic vestibular neuritis.1 These type of studies1–3 indicate that if one relies on isolated dizziness to discriminate, some patients with potentially serious etiologies will be missed. However, these studies also show that stroke is a very rare cause of isolated dizziness, so a call for increasing use of neuroimaging in the dizzy patient in general does not seem justifiable, particularly when considering the healthcare utilization perspective.
In his correspondence, Dr Johkura stresses difficulty in distinguishing central from peripheral causes of positional vertigo. Benign paroxysmal positional vertigo (BPPV) is generally readily distinguishable from central positional vertigo based on bedside characteristics of nystagmus and also the response to the simple repositioning maneuver described by Epley 15 years ago.4 Repositioning maneuvers for the horizontal canal variant are also well described.5 The patterns of nystagmus caused by BPPV are highly characteristic and well-defined for this very common disorder and its variants.6 To be conservative, central positional vertigo should be considered when features of BPPV are atypical or when nystagmus continues to be triggered by positional testing despite repositioning maneuvers. The extra step of retesting is critical to ensuring that the maneuvers did correct the disorder because repositioning does not treat central positional vertigo. Dr Johkura’s study helps to reiterate how uncommon central causes of positional vertigo are compared with BPPV. Because CT scans can miss a tumor or ischemic stroke, particularly within the posterior fossa, and MRI is not a practical routine study for the common presentation of dizziness in the Emergency Department, we feel a greater understanding of dizziness among clinicians and more studies establishing clinical predictors of central causes should be emphasized rather than increased reliance on neuroimaging.
Sources of Funding
L.B.M. is supported by NIH R01 NS38916.
Lee H, Sohn SI, Cho YW, Lee SR, Ahn BH, Park BR, Baloh RW. Cerebellar infarction presenting isolated vertigo: frequency and vascular topographical patterns. Neurology. 2006; 67: 1178–1183.
Kerber KA, Brown DL, Lisabeth LD, Smith MA, Morgenstern LB. Stroke among patients with dizziness, vertigo, and imbalance in the emergency department: a population-based study. Stroke. 2006; 37: 2484–2487.
Johkura K. Vertigo and dizziness associated with cerebrovascular diseases. Nihon Ishikai Zasshi [The Journal of the Japan Medical Association]. 2005; 134: 1485–1490[In Japanese].
Aw ST, Todd MJ, Aw GE, McGarvie LA, Halmagyi GM. Benign positional nystagmus: a study of its three-dimensional spatio-temporal characteristics. Neurology. 2005; 64: 1897–1905.