When, where, and why should we look for vestibular dysfunction in people with diabetes mellitus?

The biochemistry of diabetes mellitus results in multi-system tissue compromise that reduces functional mobility and interferes with disease management. Sensory system compromise, such as peripheral neuropathy and retinopathy, are specific examples of tissue compromise detrimental to functional mobility. There is lack of clarity regarding if, when, and where parallel changes in the peripheral vestibular system, an additional essential sensory system for functional mobility, occur as a result of diabetes. Given the systemic nature of diabetes and the plasticity of the vestibular system, there is even less clarity regarding if potential vestibular system changes impact functional mobility in a meaningful fashion. This commentary will provide insight as to when we should employ diagnostic vestibular function tests in people with diabetes, where in the periphery we should look, and why testing may or may not matter. The commentary concludes with recommendations for future research and clinical care.

Case report: Atypical patterns of nystagmus suggest posterior canal cupulolithiasis and short-arm canalithiasis.

Background: Atypical posterior canal (PC) positional nystagmus may be due to the changes in cupular response dynamics from cupulolithiasis (cu), canalithiasis of the short arm (ca-sa), or a partial/complete obstruction-jam. Factors that change the dynamics are the position of the head in the pitch plane, individual variability in the location of the PC attachment to the utricle and the position of the cupula within the ampulla, and the location of debris within the short arm and on the cupula. The clinical presentation of PC-BPPV-cu is DBN with torsion towards the contralateral side in the DH positions and SHHP or no nystagmus in the ipsilateral DH position and no nystagmus upon return to sitting from each position. The clinical presentation of PC-BPPV-ca-sa is no nystagmus in the DH position and upbeat nystagmus (UBN) with torsion lateralized to the involved side upon return to sitting from each position. Case description: A 68-year-old woman, diagnosed with BPPV, presented with DBN associated with vertigo in both DH positions and without nystagmus or symptoms on sitting up. In the straight head hanging position (SHHP), the findings of a transient burst of UBN with left torsion associated with vertigo suggested ipsicanal conversion from the left PC-BPPV-cu to canalithiasis. Treatment included a modified canalith repositioning procedure (CRP), which resulted in complete resolution. BPPV recurred 17 days later. Clinical presentation of BPPV included no nystagmus/symptoms in both the contralateral DH position and SHHP, DBN in the ipsilateral DH position without symptoms, and UBN with left torsion associated with severe truncal retropulsion and nausea on sitting up from provoking position. The findings suggested the left PC-BPPV-cu-sa and PC-BPPV-ca-sa. Treatment included neck extension, a modified CRP, and demi-Semont before complete resolution. Conclusion: An understanding of the biomechanics of the vestibular system is necessary to differentially diagnose atypical PC-BPPV. DH test (DHT) findings suggest that PC-BPPV-cu presents with DBN or no nystagmus in one or two DH positions and sometimes SHHP and without nystagmus or no reversal/reversal of nystagmus on sitting up. The findings suggest PC-BPPV-ca-sa has no nystagmus in DH positions or DBN in the ipsilateral DH position and UBN with torsion lateralized to the involved side on sitting up.

Reliability of two dissociating tests of phoria in artificially created phoria in normal adults.

BACKGROUND: The ability of physical therapists (PTs) to accurately identify and reliably measure phoria/tropia is critical in the differential diagnosis of individuals with acute vestibular syndrome and concussion/mild traumatic brain injury. OBJECTIVES: To determine if PTs may reliably measure phoria and to determine the reliability of two dissociating tests of phoria, the prism neutralized Maddox rod test and modified Thorington method, in normal adults with artificially created phoria. METHODS: Thirty adults (mean age 24.87 ± 4.74 years) were randomly assigned to wear trial lenses (1, 2, 4, or 6 pd prism left, plain glass right) to create phoria. In sitting and supine, phoria was measured using prism neutralized Maddox rod test and modified Thorington method. Mean, SD, and range of first neutral endpoint were calculated for each examiner. Percentage of trials in agreement (≤ 2 and 4 pd); comparisons within the linear mixed effects regression model; and inter-rater reliability between examiners was calculated with the intra-class correlation coefficient (ICC). RESULTS: Participants underwent 20 measurements by each examiner. Trial agreement between examiners was 74% (range 13%-100%) in horizontal and 91% (range 63%-100%) in vertical plane. Maddox rod test had significantly different means between two examiners (P < .05). Modified Thorington test had no significant difference. The Maddox rod test had a significant examiner main effect, examiner 2 always scored lower. Inter-rater correlation coefficient for each test was significant at level of P < .01 (ICC ≥ 0.67 ≤ 0.94) except for modified Thorington test in supine, horizontal plane with P < .05 (ICC ≥ 0.38). CONCLUSION: PTs may reliably measure artificially created phorias using prism neutralized Maddox rod test and modified Thorington method.

Horizontal semicircular canal jam: Two new cases and possible mechanisms.

INTRODUCTION: Benign paroxysmal positional vertigo (BPPV) of the horizontal semicircular canal (hSCC) can present with otoconia blocking its lumen (canalith jam), with signs and symptoms that make it difficult to distinguish from central nervous system pathology. OBJECTIVE: Here we report two cases of canalith jam affecting the hSCC and offer a theoretical mechanism based on known vestibular neurophysiology. METHODS: We use video-oculography to document the canalith jam and show the moment the otoconia loosen. RESULTS: Canalith jam is a rare form of BPPV remedied with repositioning maneuvers. CONCLUSION: Clinicians should consider canalith jam as a mechanism for BPPV when the nystagmus is (a) Direction fixed with fixation removed and during positional testing; (b) Velocity dependent on supine head position; (c) Converts to geotropic directional changing nystagmus.

Peripheral Downbeat Positional Nystagmus: Apogeotropic Posterior Canal or Anterior Canal BPPV.

BACKGROUND AND PURPOSE: Downbeat nystagmus (DBN) during the Dix-Hallpike test (DHT) suggests excitation of the anterior canal (AC) or inhibition of the posterior canal (PC) underlying benign paroxysmal positional vertigo (BPPV). This case series describes 2 individuals presenting with DBN in positional testing suggestive of a PC BPPV variant termed apogeotropic PC-BPPV and due to inhibition of the PC. CASE DESCRIPTIONS: Case 1 illustrates a DBN during positional testing (PC inhibition) that changes to an upbeating nystagmus (PC excitation) representing the otoconial material changing location and direction of movement within the PC. Case 2 describes a canal jam in the nonampullary segment of the PC. DIFFERENTIAL DIAGNOSIS: Apogeotropic PC-BPPV can cause DBN due to inhibition of the vestibular afferent. Apogeotropic PC-BPPV may be due to a canal jam of debris within the nonampullary segment or cupulolithiasis with debris attached to the inferior-most aspect of the cupula within the PC. It can be difficult to differentiate AC-BPPV from the apogeotropic PC-BPPV variant. In both forms, the affected canal may be provoked in 1 or both positions of the DHT and straight head hanging position. However, in AC-BPPV there may only be a slight or absent torsional component toward the involved ear. In apogeotropic PC-BPPV, a strong torsion away from the involved ear is typically observed. The straight head hanging position may resolve AC-BPPV or convert apogeotropic PC-BPPV to typical PC-BPPV. SUMMARY: These 2 cases illustrate atypical variants of BPPV that clinicians must consider in their interpretation of DBN during positional testing, particularly in the absence of other neurological signs.

Test-retest and Interrater Reliability of the Video Head Impulse Test in the Pediatric Population.

OBJECTIVE: Determine reliability of horizontal and vertical video head impulse test (vHIT) and effect of maturation on angular vestibular ocular reflex (AVOR) gain estimations and peak head velocities of individual canals in typically developing children and adolescents. DESIGN: Reliability study. SETTING: University research laboratory SUBJECTS: : Two normal adults mean age 51.5 ±â€Š0.5 years and 28 typically developing children and adolescents mean age 10 ±â€Š3.5 years (range, 4.33-17.25 years). MAIN OUTCOME MEASURES: Mean AVOR gain estimate and peak head impulse velocity for individual canals. RESULTS: In adult sample, mean AVOR gain estimates were 1.00 to 1.04 for lateral and 1.07 to 1.13 for vertical canals. In pediatric sample, mean AVOR gain estimates were 1.00 to 1.04 for lateral and 1.03 to 1.08 vertical canals. Mean AVOR gain intrarater reliability scores (intraclass correlation coefficient [ICC] ≥ 0.821 ≤ 0.945) and interrater reliability scores (ICC ≥ 0.800 ≤ 0.971) had good consistency. For each canal, across each age group, the range of percentage of trials with peak head velocities greater than 100 degrees/s was 32 to 49% right lateral, 31 to 49% left lateral, 0 to 11% right anterior, 3 to 4% left anterior, 1 to 7% right posterior, and 2 to 8% left posterior. Children aged less than 12 years, required 10 to 49% more trials compared with adults to obtain five valid, filtered trials. Adolescents required a similar number of trials compared with adults. CONCLUSION: In pediatric population, vHIT is a reliable clinical test to quantify individual canal function using high velocity head impulses. With children, it was difficult to acquire head impulse velocities of greater than 100 degrees/s especially in the plane of the vertical canals. These higher head velocities are required to reveal asymmetry in compensatory eye movements.

Effectiveness of particle repositioning maneuvers in the treatment of benign paroxysmal positional vertigo: a systematic review.

BACKGROUND: Benign paroxysmal positional vertigo (BPPV) is the most common cause of vertigo. PURPOSE: The purpose of this systematic review was to determine whether patients diagnosed with posterior canal (PC) BPPV, based on positional testing, and treated with a particle repositioning maneuver will show the resolution of benign paroxysmal positional nystagmus (BPPN) on the Dix-Hallpike Test performed 24 hours or more after treatment. DATA SOURCES: Data were obtained from an electronic search of the MEDLINE, EMBASE, and CINAHL databases from 1966 through September 2009. STUDY SELECTION: The study topics were randomized controlled trials (RCTs), quasi-RCTs, the diagnosis of PC BPPV, treatment with the particle repositioning maneuver, and outcome measured with a positional test 24 hours or more after treatment. DATA EXTRACTION: Data extracted were study descriptors and the information used to code for effect size. DATA SYNTHESIS: In 2 double-blind RCTs, the odds in favor of the resolution of BPPN were 22 times (95% confidence interval=3.41-141.73) and 37 times (95% confidence interval=8.75-159.22) higher in people receiving the canalith repositioning procedure (CRP) than in people receiving a sham treatment. This finding was supported by the results reported in 8 nonmasked quasi-RCTs. Studies with limited methodological quality suggested that a liberatory maneuver (LM) was more effective than a control intervention; there was no significant difference in the effectiveness of the LM and the effectiveness of the CRP; the self-administered CRP was more effective than the self-administered LM; and the CRP administered together with the self-administered CRP was more effective than the CRP administered alone. The Brandt-Daroff exercises were the least effective self-administered treatments. LIMITATIONS: The limitations included the methodological quality of the studies, the lack of quality-of-life measures, and confounding factors in reporting vertigo. CONCLUSIONS: Randomized controlled trials provided strong evidence that the CRP resolves PC BPPN, and quasi-RCTs suggested that the CRP or the LM performed by a clinician or with proper instruction at home by the patient resolves PC BPPN. There were no data on the effects of the maneuvers on outcomes relevant to patients.

Daily exercise does not prevent recurrence of benign paroxysmal positional vertigo.

OBJECTIVE: The purpose of this study was to analyze if a daily routine of self-canalith repositioning procedure (CRP) will increase the time to recurrence and reduce the rate of recurrence of benign paroxysmal positional vertigo (BPPV). STUDY DESIGN: Prospective study, nonrandomized control group. SETTING: Outpatient clinic. PATIENTS: Thirty-nine patients diagnosed with posterior canal BPPV successfully treated with the CRP. Based on a convenience sample, 17 (44%) patients were assigned to the treatment group, whereas 22 (56%) were assigned to the no-treatment group. The number of subjects lost at the time of follow-up were 5 (29.4%) of the treatment group and 2 (9%) of the no-treatment group. INTERVENTIONS: Patients assigned to the treatment group performed the self-CRP daily, whereas those assigned to the no-treatment group performed no exercises. Patients were followed for up to 2 years. MAIN OUTCOME MEASURES: The main outcome measures were the rate of recurrence of BPPV and the time for BPPV to recur. RESULTS: Of the 39 subjects, symptoms recurred in 16 (41%) of the total population, 6 (35%) of 17 of the treatment group, and 10 (46%) of 22 of the no-treatment group. There was no difference in the frequency of recurrence (Pearson chi; p = 0.522) or the time to recurrence (survival analysis; log-rank test; p = 0.242). CONCLUSION: Our results suggest that a daily routine of the self-CRP does not affect the time to recurrence and the rate of recurrence of posterior canal-BPPV.

Strategies to prevent recurrence of benign paroxysmal positional vertigo.

OBJECTIVE: To determine if a daily routine of Brandt-Daroff exercises increases the time to recurrence and reduces the rate of recurrence of benign paroxysmal positional vertigo (BPPV). DESIGN: Random sample of convenience and retrospective case review. SETTING: Tertiary referral center and outpatient clinic. PATIENTS: One hundred sixteen patients diagnosed with BPPV involving the posterior semicircular canal (BPPV-PC) who were successfully treated with the canalith repositioning procedure. INTERVENTIONS: Patients in the treatment group (n = 43) performed daily Brandt-Daroff exercises, while patients in the no-treatment group (n = 73) performed no exercises. MAIN OUTCOME MEASURES: Follow-up was as long as 2 years. Every 2 months patients were mailed a questionnaire. If BPPV had recurred, patients contacted the principal investigator within 24 hours. Within 1 to 2 weeks, patients were evaluated in the clinic with the Dix-Hallpike maneuver or, if unable to travel to the clinic, interviewed by telephone. RESULTS: Symptoms recurred in 50 (43%) of the 116 subjects, 34 (47%) of 73 in the no-treatment group and 16 (37%) of 43 in the treatment group. There was no significant difference in the frequency of recurrence (Pearson chi(2), P = .33) or time to recurrence (survival analysis, log-rank test, P = .92). A history of recurrent BPPV-PC did not affect frequency of recurrence (Pearson chi(2), P = .33) or time to recurrence (survival analysis, log-rank test, P = .72). CONCLUSION: Our results suggest that a daily routine of Brandt-Daroff exercises does not significantly affect the time to recurrence or the rate of recurrence of BPPV-PC.

Macaque frontal eye field input to saccade-related neurons in the superior colliculus.

Extracellular recordings were made simultaneously in the frontal eye field and superior colliculus in awake, behaving rhesus monkeys. Frontal eye field microstimulation was used to orthodromically activate the superior colliculus both to locate the depth of the strongest frontal eye field input to the superior colliculus and to identify superior colliculus neurons receiving direct frontal eye field input. The activity of orthodromically driven colliculus neurons was characterized during visuomotor tasks. The purpose of this study was to identify the types of superior colliculus neurons that receive excitatory frontal eye field input. We found that microstimulation of the frontal eye field did not activate the superficial layers of the superior colliculus but did activate the deeper layers. This pattern of activation coincided with the prevalence of visual versus saccade-related activity in the superficial and deep layers. A total of 83 orthodromically driven superior colliculus neurons were identified. Of these neurons, 93% (n = 77) exhibited a burst of activity associated with the onset of the saccade, and 25% (n = 21) exhibited prelude/build-up activity prior to the onset of a saccade. In addition, it was common to see some activity synchronized with the onset of a visual target (30%, n = 25). In single neurons, these activity profiles could be observed alone or in combination. Superior colliculus neurons that were exclusively visual, however, were not excited by frontal eye field stimulation. We compared the activity of superior colliculus neurons that received frontal eye field input to descriptions of saccade-related neurons made in earlier reports and found that the distribution of neuron types in the orthodromically driven population was similar to the distribution within the overall population. This suggests that the frontal eye field does not selectively influence a specific class of collicular neurons, but, instead has a direct influence on all preparatory, and saccade-related activity within the deep layers of the superior colliculus.