The diagnosis of BPPV is based on the clinical history and physical examination. Routine radiographic imaging or vestibular testing is unnecessary in patients who already meet clinical criteria for the diagnosis of BPPV (Table 2.1). Further radiographic or vestibular testing may have a role in the diagnosis if the clinical presentation is felt to be atypical, if Dix-Hallpike testing elicits equivocal or unusual nystagmus findings, or if additional symptoms aside from those attributable to BPPV are present, suggesting an accompanying modifying CNS or otological disorder.

Radiographic Imaging

Radiographic imaging, most commonly CNS imaging using magnetic resonance or CT techniques, is commonly obtained in the evaluation of a primary symptom complaint of vertigo. However, imaging is not useful in the routine diagnosis of BPPV because there are no radiological findings characteristic of or diagnostic for BPPV (Turski, et al., 1996) (Turski, et al., 1996). The lack of characteristic findings is likely due to fact that the pathology presumed to occur in BPPV within the semicircular canals occurs at a microscopic level that is beyond the resolution of current neuroimaging techniques (Parnes, et al., 1992). On a broader scale, previous retrospective reviews of elderly patients with dizziness failed to detect any significant differences in cranial MRI findings when comparing dizzy versus non-dizzy patients (Colledge, et al., 1996) (Day, et al., 1990).

Radiographic imaging of the CNS should be reserved for patients who present with a clinical history compatible with BPPV but who also demonstrate additional neurological symptoms atypical for BPPV. Radiographic imaging may also be considered for patients with suspected BPPV but inconclusive positional testing, or in patients with other neurological signs on physical examination that are not typically associated with BPPV. Such symptoms include abnormal cranial nerve findings, visual disturbances, and severe headache, among others. It should be noted that intracranial lesions causing vertigo are rare. (Hanley, et al., 2001) Potential lesions causing vertigo identifiable on CNS imaging include cerebrovascular disease, demyelinating disease, or an intracranial mass; they are most often located in the brain stem cerebellum, thalamus, or cortex (Hanley, et al., 2001). In small case series, positional vertigo and nystagmus have been associated with neurovascular compression of cranial nerve VIII, vestibular schwannoma, Arnold Chiari malformation, and a variety of cerebellar disorders (Brandt, et al., 1994) (Jacobsen, et al., 1995) (Kumar, et al., 2002).

In distinction to standard BPPV, such conditions are quite rare and typically present with additional neurological symptoms in conjunction with the vertigo. Routine neuroimaging has not been recommended to discern these conditions from the more common causes of vertigo (Gizzi, et al., 1996). The costs of routine imaging in cases of BPPV are not justified given that diagnostic neuroimaging does not improve the diagnostic accuracy in the vast majority of BPPV cases. Therefore, neuroimaging should not be routinely used to confirm the diagnosis of BPPV.

Vestibular Function Testing

When patients meet clinical criteria for the diagnosis of BPPV (Table 2.1), no additional diagnostic benefit is obtained from vestibular function testing. Vestibular function testing is indicated when the diagnosis of a vertiginous or dizziness syndrome is unclear or possibly when the patient remains symptomatic following treatment. It may also be beneficial when multiple concurrent peripheral vestibular disorders are suspected (Baloh, et al., 1987) (Kentala, et al., 1996)(Lopez-Escamez, et al., 2003).

Vestibular function testing involves a battery of specialized tests that primarily record nystagmus in response to labyrinthine stimulation and/or voluntary eye movements. Most vestibular function testing relies on the neurological relationship between the regulation of eye movement and the balance organs: the vestibular-ocular reflex. These tests are useful in the evaluation of vestibular disorders that may not be evident from the history and clinical examination, and may provide information for quantification, prognostication, and treatment planning (Gordon, et al., 1996). The components of the vestibular function test battery identify abnormalities in ocular motility as well as deficits in labyrinthine response to position change, caloric stimulation, rotational movement, and static positions (sitting and supine). Caloric testing is an established, widely accepted technique that is particularly useful in determining unilateral vestibular hypofunction. Rotational chair testing is considered the most sensitive and reliable technique for quantifying the magnitude of bilateral peripheral vestibular hypofunction (Fife, et al., 2008) and to assess central compensation after peripheral vestibular loss. Some or all of these test elements may be included in a vestibular test battery.

In cases of BPPV in which the nystagmus findings are suggestive but not clear, it may be beneficial to use video-oculographic recordings of nystagmus associated with posterior canal BPPV. Especially video-recorded eye movements can be analysed in detail using image-processing techniques. for further study or second opinion without the need to repeat the Dix-Hallpike manoeuvre. A second diagnostic procedure often will result in more difficult to asses eye movements because of the typical fatigue of a BPPV. In a small percentage of cases, patients with a history of positional vertigo but unclear nystagmus findings may undergo vestibular function testing. Among complex patients referred for subspecialty evaluation of BPPV, such atypical or unclear nystagmus findings may approach 13 percent in patients with diagnoses suspicious for BPPV (Bath, et al., 2000).

BPPV is relatively frequently associated with additional vestibular pathology. Symptoms associated with chronic vestibular function may persist following appropriate treatment for BPPV, even if the treatment is effective in resolving the specific complaint of positional vertigo. For example, in highly selected subsets of patients referred for subspecialty evaluation of BPPV, additional otopathology and/or vestibulopathy has been identified in 31 to 53 percent of BPPV patients (Baloh, et al., 1987) (Roberts, et al., 2005) (Korres, et al., 2004). This percentage, however, is higher than what might be expected in the nonspecialty population. Vestibular disorders that have been associated with BPPV include Ménière’s disease, viral vestibular neuritis, or labyrinthitis (Hughes, et al., 1997)(Karlberg, et al., 2000). Vestibular function testing may be obtained when these additional diagnoses are suspected on the basis of signs or symptoms in addition to those of BPPV.

In patients with vestibular pathology in addition to BPPV, PRMs appear to be equally effective in resolving the positional nystagmus associated with BPPV, but complete symptom resolution is significantly less likely in those patients with additional vestibular pathology. In one study, 86 percent of patients with BPPV but without associated vestibular pathology reported complete resolution of symptoms after PRMs versus only 37 percent reporting complete resolution when additional vestibular pathology was present (Pollak, et al., 2004).

Thus, patients with suspected associated vestibular pathology in addition to BPPV may be a subset who would benefit from the additional information obtained from vestibular function testing. Similarly, up to 25 percent of patients with separate recurrences of BPPV are more likely to have associated vestibular pathology (Del Rio, et al., 2004); therefore, patients with recurrent BPPV may be candidates for vestibular function testing. In summary, patients with a clinical diagnosis of BPPV according to guideline criteria should not routinely undergo vestibular function testing, because the information provided from such testing adds little to the diagnostic accuracy in these cases, vestibular testing adds significant cost to the diagnosis and management of BPPV, and the information obtained does not alter the subsequent management of BPPV in the vast majority of the cases. Therefore, vestibular function testing should not be routinely obtained when the diagnosis of BPPV has already been confirmed by clinical diagnostic criteria. Vestibular function testing, however,may be warranted in patients with 1) atypical nystagmus, 2) suspected additional vestibular pathology, 3) a failed (or repeatedly failed) response to CRP, or 4) frequent recurrences of BPPV (Rupa, et al., 2004) (Gordon, et al., 2005).