SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Pathologic nystagmus

169

Wernicke’s encephalopathy (WE) is a serious medical emergency whose pathogenesis is well understood and reviewed in this paper. Summarizing the evidence for its prophylaxis and management, the authors suggest that, in the UK, there is evidence that many patients identified as being at risk of WE currently do not receive appropriate treatment, despite the availability (not universal) of guidelines and protocols.

Concepts: Illness, United Kingdom, Anarchy in the U.K., Pathologic nystagmus, Encephalopathy, Wernicke's encephalopathy, Act of Parliament, Carl Wernicke

168

Spontaneous nystagmus, which has been considered a typical sign of acute vestibulopathy, has recently been reported in benign paroxysmal positional vertigo involving the lateral semicircular canals (LC-BPPV) without unilateral vestibulopathy (pseudo-spontaneous nystagmus, PSN), but research about its clinical application is still limited. Here we investigate the frequency and characteristics of PSN in LC-BPPV patients, and estimate its prognostic value.

Concepts: Medical terms, Semicircular canal, Prognosis, Ear, Canal, Pathologic nystagmus, Benign paroxysmal positional vertigo, Horizontal semicircular canal

28

PURPOSE OF REVIEW: This review examines the research from 2011 through 2012 on treatment efficacy in two common vestibular disorders - vestibular hypofunction and benign paroxysmal positional vertigo (BPPV). RECENT FINDINGS: Significant numbers of randomized controlled trials now support the use of specific exercises for the treatment of patients with unilateral peripheral vestibular hypofunction. We do not know if some treatment approaches are more effective than others. There is preliminary evidence that head movement may be the component critical to recovered function and decreased symptoms. Some patient characteristics and initial assessment results appear to predict treatment outcome but the evidence is incomplete. Treatment of posterior canal BPPV canalithiasis is well established. New evidence supports certain treatments for horizontal canal BPPV. SUMMARY: Treatments for unilateral vestibular hypofunction and for posterior canal BPPV are effective; however, there are many as yet unanswered questions such as why some patients with vestibular hypofunction do not improve with a course of vestibular exercises. We also do not know what would be the best treatment for anterior canal BPPV or for multiple-canal involvement BPPV.

Concepts: Clinical trial, Critical thinking, Patient, Randomized controlled trial, Effectiveness, Efficacy, Pathologic nystagmus, Benign paroxysmal positional vertigo

28

Meniere’s disease is characterized by sporadic episodes of vertigo, nystagmus, fluctuating sensorineural hearing loss, tinnitus and aural pressure. Since Meniere’s disease can affect different regions of the vestibular labyrinth, we investigated if electrical vestibular stimulation (EVS) which excites the entire vestibular labyrinth may be useful to reveal patchy endorgan pathology. We recorded three-dimensional electrically evoked vestibulo-ocular reflex (eVOR) to transient EVS using bilateral, bipolar 100-ms current steps at intensities of 0.9, 2.5, 5.0, 7.5 and 10.0 mA with dual-search coils in 12 unilateral Meniere’s patients. Their results were compared to 17 normal subjects. Normal eVOR had tonic and phasic spatiotemporal properties best described by the torsional component, which was four times larger than horizontal and vertical components. At EVS onset and offset of 8.9 ms latency, there were phasic eVOR initiation (M = 1,267 °/s(2)) and cessation (M = -1,675 °/s(2)) acceleration pulses, whereas during the constant portion of the EVS, there was a maintained tonic eVOR (M = 9.1 °/s) at 10 mA. However in Meniere’s disease, whilst latency of EVS onset and offset was normal at 9.0 ms, phasic eVOR initiation (M = 1,720 °/s(2)) and cessation (M = -2,523 °/s(2)) were enlarged at 10 mA. The initiation profile was a bimodal response, whilst the cessation profile frequently did not return to baseline. The tonic eVOR (M = 20.5 °/s) exhibited a ramped enhancement of about twice normal at 10 mA. Tonic eVOR enhancement was present for EVS >0.9 mA and disproportionately enhanced the torsional, vertical and horizontal components. These eVOR abnormalities may be a diagnostic indicator of Meniere’s disease and may explain the vertigo attacks in the presence of declining mechanically evoked vestibular responses.

Concepts: Vestibular system, Vestibulo-ocular reflex, Ear, Tinnitus, Ménière's disease, Pathologic nystagmus, Organ of Corti, Endolymph

28

Infantile nystagmus is commonly associated with afferent abnormalities that can be detected using a range of investigative modalities. Optical coherence tomography allows high-resolution in vivo imaging of the retina. Recent studies have shown characteristic foveal abnormalities in patients with albinism, PAX6 mutations, and isolated foveal hypoplasia. Arrested development of the fovea leads to foveal hypoplasia, which causes reduction in visual acuity. Previous studies have shown correlations between visual acuity and the degree of foveal hypoplasia. Furthermore, in achromatopsia a characteristic lesion has been described that is associated with cone photoreceptor degeneration. Patients with achromatopsia also have foveal hypoplasia, however with atypical features. The signs of photoreceptor degeneration were progressive, which suggests that gene therapy is likely to be most beneficial if given within the first few years of life. With the advent of high speed and ultrahigh resolution optical coherence tomography it is now possible to document reliably the stages of foveal development and cone photoreceptor degeneration. This will aid clinicians in diagnosis and predicting prognosis in patients with infantile nystagmus.

Concepts: Optics, Medical terms, Retina, Eye, Photoreceptor cell, Ophthalmology, Color blindness, Pathologic nystagmus

28

INTRODUCTION: Benign paroxysmal positional vertigo (BPPV) is the most common vestibular disorder. However, BPPV in children has been studied less extensively than in the adult population. This is because the observation of benign paroxysmal positional nystagmus (BPPN) in children is technically very difficult and BPPV is rare in children. In this study, we present the only two cases of BPPV in children in which we successfully recorded and analyzed the BPPN. METHODS: One case was an 11-year-old boy and the other was a 3-year-old girl. We analyzed their BPPN three-dimensionally. RESULTS: Apogeotropic positional nystagmus was observed in the first case. We analyzed it to verify the presence of cupulolithiasis in the horizontal semicircular canal (HSCC). Geotropic positional nystagmus was observed in the second case, and the analyzed data indicated the presence of canalolithiasis in HSCC. Over the last decade, we have examined 3341 patients complaining of vertigo or dizziness. Among them, there were 63 children with the same complaint, so that the proportion of cases of BPPV in children was only 3% (2/63). DISCUSSION: Among patients complaining of vertigo or dizziness, children with BPPV are rare (3%). However, we have recorded their BPPN to confirm that BPPV does occur in children and that their characteristics of positional nystagmus are generally identical to those in adults. We emphasize that this is the first report of a child as young as 3 years old being diagnosed with BPPV.

Concepts: Scientific method, Observation, Semicircular canal, Ear, Case, Pathologic nystagmus, Complaint, Benign paroxysmal positional vertigo

27

BACKGROUND: Patients with vestibular migraine (VM) suffer attacks of vertigo that often occur in isolation from headache attacks. We aimed to assess and compare vestibular function interictally in patients with VM and patients with migraine without vertigo (M). METHODS: Thirty-eight patients diagnosed with definite VM according to the Neuhauser criteria, and 32 patients diagnosed with M according to the International Headache Society criteria were examined between attacks using a broad battery of bedside vestibular tests, a caloric test, and videonystagmography. RESULTS: Overall, 70% of the VM patients and 34% of the M patients showed abnormalities on one or more of the 14 performed vestibular tests (P = .006). Abnormal findings were more frequent in VM than in M patients on Romberg’s test, test for voluntary fixation suppression of the vestibular ocular reflex and test for static positional nystagmus (P = .03, .01 and .04, respectively). There were no differences in the distribution of central and peripheral vestibular signs between VM and M patients. CONCLUSIONS: Vestibular abnormalities were present interictally among both VM and M patients, but were found about twice as frequently among VM patients. This may indicate that subclinical vestibular dysfunction is an integral part of migraine pathology in general, and not solely in VM.

Concepts: Comparison, Vestibular system, Vestibulo-ocular reflex, Headaches, Pathologic nystagmus, Romberg's test, Caloric reflex test

27

OBJECTIVE: To characterize reading deficits in infantile nystagmus (IN), to determine optimal font sizes for reading in IN, and to investigate whether visual acuity (VA) and severity of nystagmus are good indicators of reading performance in IN. DESIGN: Prospective cross-sectional study. PARTICIPANTS AND CONTROLS: Seventy-one participants with IN (37 idiopathic, 34 with albinism) and 20 age-matched controls. METHODS: Reading performance was assessed using Radner reading charts and was compared with near logarithm of the minimum angle of resolution (logMAR) VA, nystagmus intensity, and foveation characteristics as quantified using eye movement recordings. MAIN OUTCOME MEASURES: Reading acuity (smallest readable font size), maximum reading speed, critical print size (font size below which reading is suboptimal), near logMAR VA, nystagmus intensity, and foveation characteristics (using the eXpanded Nystagmus Acuity Function). RESULTS: Using optimal reading conditions, maximum reading speeds were 18.8% slower in albinism and 14.7% slower in idiopathic IN patients compared with controls. Reading acuities were significantly worse (P<0.001) in IN patients compared with controls. Also, the range of font sizes over which reading speeds were less than the optimum were much larger in IN patients compared with controls (P<0.001). Reading acuity was correlated strongly to near VA (r2 = 0.74 albinism, r2 = 0.55 idiopathic), but was better than near VA in participants with poor VA. Near VA was a poor predictor of maximum reading speed. Nystagmus intensity and foveation were poor indicators of both reading acuity and maximum reading speed. CONCLUSIONS: Maximum reading speeds can be near normal in IN when optimal font sizes are provided, even in individuals with poor VA or intense nystagmus. However, reading performance in IN is acutely sensitive to font size limitations. Font sizes for optimal reading speeds in IN may be as much as 6 logMAR lines worse than the near VA. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Concepts: Cross-sectional study, Visual acuity, Optimization, Intensity, Maxima and minima, Speed, Pathologic nystagmus

27

OBJECTIVE: The relatively low success rate of the treatment maneuver for horizontal semicircular canal (HSC) benign paroxysmal positional vertigo (BPPV) may be caused by the difficulty determining the affected side. We developed a 180-degree supine roll test (SRT) by modifying the 90-degree SRT to increase diagnostic accuracy and evaluated its significance. STUDY DESIGN: A prospective study. SETTING: Tertiary referral center. PATIENTS: A total of 122 patients with HSC-BPPV performed both the 90- and 180-degree SRTs. INTERVENTIONS: The affected side was determined by the 90- and 180-degree SRTs. The bow and lean (BL) test was also performed in cases with ambiguous or opposite results on both SRTs. MAIN OUTCOME MEASURE: A comparison of the difference in slow phase velocity (SPV) of nystagmus among the 90- and 180-degree SRTs and BL test. RESULTS: The maximum SPV of nystagmus during the 180-degree SRT was significantly greater than that during the 90-degree SRT. The SPV difference was less in the 180-degree SRT than that in the 90-degree SRT. Although the 180-degree SRT showed fewer meaningful results (n = 65) than the 90-degree SRT (n = 71), the affected side was determined by the 180-degree SRT in 15 cases with ambiguous results on the 90-degree SRT. Among 10 cases showing opposite results, 7 were identified by the BL test. Five (71.4%) of 7 cases had consistent affected sides with the 180-degree SRT. CONCLUSION: The 180-degree SRT can be an additional method when it is difficult to determine the affected side from the 90-degree SRT.

Concepts: Measurement, Semicircular canal, Arithmetic, Ear, Determinacy, Pathologic nystagmus, Benign paroxysmal positional vertigo, Horizontal semicircular canal

27

This chapter addresses the important and undertreated problem of balance disorders. The chapter has a simplified summary of the physiology of balance problems in order to set the scene. The issue of assessment is next addressed with discussion of important tests including the Berg Balance Scale and the Get Up and Go Test, and others. Posturography is discussed as well as assessment of the gravitional vertical. The assessment of vestibular function is of key importance and discussed in some detail. The focus of the chapter is on balance rehabilitation. Re-training of postural alignment and of sensory strategies are key but adaptation of the environment and re-training of cognitive strategies are also helpful in individual cases. Vestibular exercises can also be used. The chapter then critically analyses the efficacy of these treatments in specific balance disorders such as in stroke, Parkinson disease, polyneuropathies, multiple sclerosis, and vestibular disorders. Overall, there is a growing body of evidence that balance rehabilitation improves symptoms, function, and quality of life for those troubled by these disabling problems.

Concepts: Stroke, Neurology, Parkinson's disease, Vestibular system, Pathologic nystagmus, Labyrinthitis, Posturography, Balance disorder