Treatment of nystagmus

Botulinum Toxin A Injection in Horizontal Nystagmus: Effect on the Frequency of the Oscillation on a Pediatric Population

PURPOSE

To evaluate the effect of botulinum toxin A injection on the frequency of horizontal nystagmus in children.

METHODS

This was a non-randomized before-and-after clinical trial evaluating a cohort of children with horizontal nystagmus before and after treatment with botulinum toxin A. The toxin was injected under general anesthesia with spontaneous ventilation without intubation using the Mendonça forceps and the effect was evaluated by analyzing the frequency of the oscillation in Hertz (Hz) on video registrations before and after treatment.

RESULTS

The current study found a statistically significant difference on the frequency of the nystagmus in children before and after the injection of botulinum toxin A, with the mean frequency decreasing from 1.55 ± 0.94 Hz before treatment to 1.04 ± 0.87 Hz at 1 month post-injection (P < .001) and to 1.27 ± 0.87 Hz at 6 months post-injection (P = .002). When comparing the data 1 and 6 months post-injection, this study found a significant increase (P = .001) in the frequency of the nystagmus.

CONCLUSIONS

The injection of botulinum toxin A is effective in reducing the frequency of oscillations in children with horizontal nystagmus both 1 and 6 months after the procedure, and can be used as a first-line, less invasive treatment aiming to decrease the frequency of oscillation. [J Pediatr Ophthalmol Strabismus. 20XX;X(X):XXX-XXX.].

Impaired Direction Selectivity in the Nucleus of the Optic Tract of Albino Mice

Purpose

Human albinos have a low visual acuity. This is partially due to the presence of spontaneous erroneous eye movements called pendular nystagmus. This nystagmus is present in other albino vertebrates and has been hypothesized to be caused by aberrant wiring of retinal ganglion axons to the nucleus of the optic tract (NOT), a part of the accessory optic system involved in the optokinetic response to visual motion. The NOT in pigmented rodents is preferentially responsive to ipsiversive motion (i.e., motion in the contralateral visual field in the temporonasal direction). We compared the response to visual motion in the NOT of albino and pigmented mice to understand if motion coding and preference are impaired in the NOT of albino mice.

Methods

We recorded neuronal spiking activity with Neuropixels probes in the visual cortex and NOT in C57BL/6JRj mice (pigmented) and DBA/1JRj mice with oculocutaneous albinism (albino).

Results

We found that in pigmented mice, NOT is retinotopically organized, and neurons are direction tuned, whereas in albino mice, neuronal tuning is severely impaired. Neurons in the NOT of albino mice do not have a preference for ipsiversive movement. In contrast, neuronal tuning in visual cortex was preserved in albino mice and did not differ significantly from the tuning in pigmented mice.

Conclusions

We propose that excessive interhemispheric crossing of retinal projections in albinos may cause the disrupted left/right direction encoding we found in NOT. This, in turn, impairs the normal horizontal optokinetic reflex and leads to pendular albino nystagmus.

Correction of horizontal and torsional compensatory head posture in infantile nystagmus syndrome using horizontal rectus muscle recession and resection with vertical transposition

Infantile nystagmus syndrome (INS) is often characterized by an identifiable null zone. When the null zone is not in the straight-ahead gaze, a compensatory head posture (CHP) is adopted by the patient to achieve best possible vision. Various surgical procedures have been recommended to correct a CHP which is clinically predominant in one dimension of yaw (lateral rotation), pitch (anterior or posterior flexion/extension) or roll (lateral flexion). However, the presence of a complex CHP which is clinically evident in more than one dimension, warrants either a combination of multiple techniques or a stepwise approach. We report the case of a 26-year-old male with INS with an eccentric null and a multi-dimensional complex CHP of 30º left face turn, 20º right head tilt and 10º chin depression. The patient was managed by all four horizontal rectus muscle recession and resection with full tendon vertical transposition to address the face turn and head tilt. He underwent lateral rectus muscle (LR) recession with upward transposition and medial rectus muscle (MR) resection with downward transposition in the right eye. MR recession with upward transposition and LR resection with downward transposition were performed in the left eye. Postoperatively. the head posture improved significantly for both distance and near viewing. The chin depression also reduced after the procedure. He developed transient diplopia due to a small vertical deviation after the surgery, which was managed by prisms and fusional exercises. Thus, horizontal rectus muscle recession and resection combined with vertical transposition may be helpful to simultaneously improve the head tilt associated with the face turn, obviating the need for vertical rectus muscle or oblique muscle surgery.

Surgical interventions for infantile nystagmus syndrome

BACKGROUND

Infantile nystagmus syndrome (INS) is a type of eye movement disorder that can negatively impact vision. Currently, INS cannot be cured, but its effects can potentially be treated pharmacologically, optically, or surgically. This review focuses on the surgical interventions for INS. Despite the range of surgical interventions available, and currently applied in practice for the management of INS, there is no clear consensus, and no accepted clinical guidelines regarding the relative efficacy and safety of the various treatment options. A better understanding of these surgical options, along with their associated side effects, will assist clinicians in evidence-based decision-making in relation to the management of INS.

OBJECTIVES

To assess the efficacy and safety of surgical interventions for INS.

SEARCH METHODS

We searched CENTRAL, MEDLINE Ovid, Embase Ovid, ISRCTN registry, ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) to 3 July 2020, with no language restrictions.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) studying the efficacy and safety of surgical options for treating INS.

DATA COLLECTION AND ANALYSIS

Our prespecified outcome measures were the change from baseline in: binocular best-corrected distance visual acuity; head posture; amplitude, frequency, intensity, and foveation period durations of the nystagmus waveform; visual recognition times; quality of life and self-reported outcome measures; incidence of adverse effects with a probable causal link to treatment; and permanent adverse effects after surgery. Two review authors independently screened titles and abstracts and full-text articles, extracted data from eligible RCTs, and judged the risk of bias using the Cochrane tool. We reached consensus on any disagreements by discussion. We summarised the overall certainty of the evidence using the GRADE approach.

MAIN RESULTS

We only identified one eligible RCT (N = 10 participants), undertaken in India. This trial randomised participants to receive either a large retro-equatorial recession of the horizontal rectus muscle of 9 mm on the medial rectus and 12 mm on the lateral rectus, or a simple tenotomy and resuturing of the four horizontal rectus muscles. We did not identify any RCTs comparing a surgical intervention for INS relative to no treatment. In the single eligible RCT, both eyes of each participant received the same intervention. The participants' age and gender were not reported, nor was information on whether participants were idiopathic or had sensory disorders. The study only included participants with null in primary position and did not explicitly exclude those with congenital periodic alternating nystagmus. The study did not report funding source(s) or author declaration of interests. The evaluation period was six months. We judged this study at low risk for sequence generation and other sources of bias, but at high risk of bias for performance and detection bias. The risk of bias was unclear for selection bias, attrition bias, and reporting bias. There is very uncertain evidence about the effect of the interventions on visual acuity and change in amplitude, frequency, and intensity of the nystagmus waveform. We were unable to calculate relative effects due to lack of data. None of the participants in either intervention group reported adverse effects at six-month follow-up (very low-certainty evidence). There was no quantitative data reported for quality of life, although the study reported an improvement in quality of life after surgery in both intervention groups (very low-certainty evidence). Change in head posture, foveation period durations of the nystagmus waveform, visual recognition times, and permanent adverse effects after surgery were not reported in the included study. We judged the certainty of the evidence, for both the primary and secondary efficacy outcomes, to be very low. Due to a lack of comprehensive reporting of adverse events, there was also very low-certainty of the safety profile of the evaluated surgical interventions in this population. As such, we are very uncertain about the relative efficacy and safety of these interventions for the surgical management of INS.

AUTHORS' CONCLUSIONS

This systematic review identified minimal high-quality evidence relating to the efficacy and safety of surgical interventions for INS. The limited availability of evidence must be considered by clinicians when treating INS, particularly given these procedures are irreversible and often performed on children. More high-quality RCTs are needed to better understand the efficacy and safety profile of surgical interventions for INS. This will assist clinicians, people with INS, and their parents or caregivers to make evidence-based treatment decisions.

A high-affinity, partial antagonist effect of 3,4-diaminopyridine mediates action potential broadening and enhancement of transmitter release at NMJs

3,4-Diaminopyridine (3,4-DAP) increases transmitter release from neuromuscular junctions (NMJs), and low doses of 3,4-DAP (estimated to reach ∼1 μM in serum) are the Food and Drug Administration (FDA)-approved treatment for neuromuscular weakness caused by Lambert–Eaton myasthenic syndrome. Canonically, 3,4-DAP is thought to block voltage-gated potassium (Kv) channels, resulting in prolongation of the presynaptic action potential (AP). However, recent reports have shown that low millimolar concentrations of 3,4-DAP have an off-target agonist effect on the Cav1 subtype (“L-type”) of voltage-gated calcium (Cav) channels and have speculated that this agonist effect might contribute to 3,4-DAP effects on transmitter release at the NMJ. To address 3,4-DAP’s mechanism(s) of action, we first used the patch-clamp electrophysiology to characterize the concentration-dependent block of 3,4-DAP on the predominant presynaptic Kv channel subtypes found at the mammalian NMJ (Kv3.3 and Kv3.4). We identified a previously unreported high-affinity (1–10 μM) partial antagonist effect of 3,4-DAP in addition to the well-known low-affinity (0.1–1 mM) antagonist activity. We also showed that 1.5-μM DAP had no effects on Cav1.2 or Cav2.1 current. Next, we used voltage imaging to show that 1.5- or 100-μM 3,4-DAP broadened the AP waveform in a dose-dependent manner, independent of Cav1 calcium channels. Finally, we demonstrated that 1.5- or 100-μM 3,4-DAP augmented transmitter release in a dose-dependent manner and this effect was also independent of Cav1 channels. From these results, we conclude that low micromolar concentrations of 3,4-DAP act solely on Kv channels to mediate AP broadening and enhance transmitter release at the NMJ.

Reading Performance and Compensatory Head Posture in Infantile Nystagmus after Null Zone Training

This study aimed to assess the visual function, reading performance, and compensatory head posture (CHP) in schoolchildren with infantile nystagmus. A total of 18 participants aged between 13 to 18 years old were divided into spectacle (n = 9) and null zone group (n = 9) based on their visual acuity. Visual acuity (LogMAR), contrast sensitivity (Pelli–Robson), reading time and rate (Tobii TX300), and CHP were measured pre and post null zone reading training. Participants in the null zone group received 10 sessions of training (5 weeks). Visual acuity and contrast sensitivity of participants in the spectacle and null zone groups were not significantly different pre and post training. Reading performance, i.e., reading time (z = −1.36; p = 0.173) and reading rate (z = −0.06; p = 0.953), of participants in the spectacle group was not significantly different after 5 weeks. Reading time (z = −2.55; p = 0.011) and reading rate (z = −2.07; p = 0.038 of participants in the null zone group showed significant improvement post training. After 5 weeks, CHP improved in six out of the nine participants (66.7%) of the null zone group and was unchanged in all participants in the spectacle group. Null zone reading training could benefit children with infantile nystagmus in improving reading performance and compensatory head posture.

Efficacy of topical brinzolamide in children with retinal dystrophies

Background: Inherited retinal dystrophies are a leading cause of irreversible blindness in children in the United States. Topical carbonic anhydrase inhibitors have improved central vision and cystoid macular edema in patients with retinal dystrophies, but few studies have assessed their efficacy in children. Materials and Methods: A retrospective chart review was performed with Institutional Review Board approval to identify pediatric patients with inherited retinal dystrophies who received topical brinzolamide at a single university center between 2008 and 2015. Serial visual acuity and central macular thicknesses were compared to assess the efficacy of brinzolamide. Results: Seven subjects were identified who met the inclusion criteria. Four had juvenile X-linked retinoschisis, two had retinitis pigmentosa, and one had Leber congenital amaurosis. All were prescribed brinzolamide thrice daily; however, one patient was completely non-compliant. Four of the six treated patients exhibited a mild decrease in central macular thickness in both eyes during the study with all six treated patients having significantly improved vision at the first endpoint, 33.2 ± 8.2 months after treatment initiation. For treated patients, average visual acuity (LogMAR) ± standard error of the mean improved from 0.5 ± 0.04 pre-treatment to 0.3 ± 0.1 at the second endpoint, 50.2 ± 7.3 months after treatment initiation. Conclusions: Mild anatomic improvement of macular cysts was seen in pediatric patients using brinzolamide. Visual acuity improvement occurred even without significant reduction in macular cysts. Further studies are needed to determine whether the beneficial effects of carbonic anhydrase inhibitors are sustained in children with inherited retinal degenerations.

Clinical and electrophysiological results of eye muscle surgery in 17 patients with downbeat nystagmus

Purpose

To test the hypothesis that eye muscle surgery in treatment of patients with acquired downbeat nystagmus results in improvement measures of visual and ocular motor function.

Methods

This is a prospective, interventional case series analysis of clinical and electrophyisological data before and after eye muscle surgery in 17 patients with acquired downbeat nystagmus who did not respond to medical treatments. Outcome measures included: 1) routine demography and clinical characteristics, 2) subjective oscillopsia (SO), 3) binocular best-corrected visual acuity in the null position (BVA), 3) primary position strabismic deviation (SD), 5) anomalous head posture (AHP), 6) contrast sensitivity function (CS), and 7) nystagmus slow phase velocity (SPV). All patients were followed at least 12 months. Parametric and non-parametric statistical analysis of outcome measure data above pre- and post-treatment were perfomed using standard software on grouped data using computerized software.

Results

Patients' age ranged from 5 to 85 years (average 27 years). About 59% were male. Follow up ranged from 1-10 years (average 2.0 years). Around 70% had an associated central nervous systemic diagnosis, 100% had an AHP, oscillopsia and decreased CS, 53% had other eye disease, and 59% had strabismus. There were no complications from surgery. There were signficant post-treatment improvements in mean/median group BVA, SO, SD, AHP, CS, and SPV.

Conclusion

This study supports the hypothesis that eye muscle surgery as treatments for patients with acquired downbeat nystagmus can result in improvements in multiple aspects of ocular motor and visual functions.

Friedreich's ataxia: clinical features, pathogenesis and management

INTRODUCTION

Friedreich's ataxia is the most common inherited ataxia.

SOURCES OF DATA

Literature search using PubMed with keywords Friedreich's ataxia together with published papers known to the authors.

AREAS OF AGREEMENT

The last decade has seen important advances in our understanding of the pathogenesis of disease. In particular, the genetic and epigenetic mechanisms underlying the disease now offer promising novel therapeutic targets.

AREAS OF CONTROVERSY

The search for effective disease-modifying agents continues. It remains to be determined whether the most effective approach to treatment lies with increasing frataxin protein levels or addressing the metabolic consequences of the disease, for example with antioxidants.

AREAS TIMELY FOR DEVELOPING RESEARCH

Management of Freidreich's ataxia is currently focussed on symptomatic management, delivered by the multidisciplinary team. Phase II clinical trials in agents that address the abberrant silencing of the frataxin gene need to be translated into large placebo-controlled Phase III trials to help establish their therapeutic potential.

Infantile nystagmus syndrome: clinical characteristics, current theories of pathogenesis, diagnosis, and management

Infantile nystagmus syndrome (INS) is an important clinical diagnosis because it is a common presenting sign of many ocular, neurologic, and systemic diseases. Although INS has been studied for more than a century, its diagnosis and treatment remains a challenge to clinicians because of its varied manifestations and multiple associations, and its pathogenesis continues to rouse considerable scientific debate. Fueled by these challenges, recent basic research and clinical investigations have provided new insights into INS. New genetic discoveries and technological advances in ocular imaging have refined our understanding of INS subtypes and offer new diagnostic possibilities. Unexpected surgical outcomes have led to new understanding of its pathogenesis based on novel hypothesized pathways of ocular motor control. Comparative studies on nonhuman visual systems have also informed models of the neural substrate of INS in humans. This review brings together the classic profile of this disorder with recent research to provide an update on the clinical features of INS, an overview of the current theories on how and why INS develops, and a practical approach to the diagnosis and management of INS.

Myectomy of the Extraocular Muscles Without Reattachment as a Surgical Treatment for Horizontal Nystagmus

PURPOSE

To report the comparative clinical findings for two nystagmus procedures in two consecutive case series: the Sinskey anterior extirpation procedure (SAEP) and a modification, myectomy without reattachment (MWR).

METHODS

Twenty consecutive patients underwent the SAEP and 19 underwent MWR. The SAEP is a snare-assisted unmeasured deep myectomy, whereas MWR is a measured myectomy at posterior Tenon's fascia. All patients underwent comprehensive ophthalmologic and orthoptic examination with infrared videonystagmography. Binocular best corrected visual acuity, nystagmus amplitude, alignment, and versions outcomes were measured.

RESULTS

The highest percentage of patients experiencing two or more lines of improvement in distance and near acuity was in the SAEP group, who were younger than 10 years and had no ocular comorbidity (100%). Distance and near acuity improved at least one line in 71% and 86% of patients in the SAEP group and 72% and 61% in the MWR group, respectively. In both groups, patients younger than 10 years had the best acuity gains. Average nystagmus amplitude was reduced 76.3% (SAEP) and 68% (MWR). Horizontal versions were more compromised in the SAEP group and one patient experienced intraoperative orbital bleeding. Patients requiring reoperation for strabismus numbered 5 of 20 (20%) in the SAEP and 3 of 19 (16%) in the MWR groups.

CONCLUSIONS

Similar to SAEP, the MWR procedure reduces nystagmus amplitudes and improves visual acuity but with less limitation of versions, risk of intraoperative bleeding, and risk of postoperative strabismus. Data suggest that early surgery (for patients younger than 10 years) can have a greater beneficial effect on postoperative visual acuity. [J Pediatr Ophthalmol Strabismus. 2016;53(3):156-166.].

Treatment of Nystagmus in Brainstem Cavernous Malformation with Botulinum Toxin

We report a long-term eye movement study of a 68-year-old female with pontomedullary junction cavernous malformation whose dysconjugate nystagmus was treated with retrobulbar botulinum toxin A injections. Sequential, bilateral retrobulbar injections of botulinum toxin A were performed. Injections immediately decreased oscillopsia and nystagmus, and improved visual acuities. One to three months following injection, three-dimensional infrared oculography measured a significant 39-100% (P = 0.001) decrease in nystagmus amplitudes at multiple dimensions. This improvement diminished by six months in the right eye but sustained for about one year in the left eye. Over two years, botulinum toxin A injections were performed twice in the left eye and five times in the right eye. Our study supported the safe and effective use of repetitive retrobulbar botulinum toxin A injections in symptomatic nystagmus that failed medical therapy.

[Characteristics of dizziness in elderly]

Clinical features of the main diseases that may cause dizziness in elderly and approaches to its treatment are reviewed. The treatment plan and increase of its effectiveness as well as prevention of the complications and improvement of quality of life of patients should be based on these features.

Consensus clinical management guidelines for Friedreich ataxia

Friedreich ataxia (FRDA), a multisystem autosomal recessive condition, is the most common inherited ataxia in Caucasians, affecting approximately 1 in 29,000 individuals. The hallmark clinical features of FRDA include progressive afferent and cerebellar ataxia, dysarthria, impaired vibration sense and proprioception, absent tendon reflexes in lower limbs, pyramidal weakness, scoliosis, foot deformity and cardiomyopathy. Despite significant progress in the search for disease modifying agents, the chronic progressive nature of FRDA continues to have a profound impact on the health and well-being of people with FRDA. At present there is no proven treatment that can slow the progression or eventual outcome of this life-shortening condition. Thirty-nine expert clinicians located in Europe, Australia, Canada and USA critically appraised the published evidence related to FRDA clinical care and provided this evidence in a concise manner. Where no published data specific to FRDA existed, recommendations were based on data related to similar conditions and/or expert consensus. There were 146 recommendations developed to ensure best practice in the delivery of health services to people with FRDA. Sixty-two percent of recommendations are based on expert opinion or good practice indicating the paucity of high-level quality clinical studies in this area. Whilst the development of these guidelines provides a critical first step in the provision of appropriate clinical care for people with FRDA, it also highlights the urgency of undertaking high-quality clinical studies that will ensure the delivery of optimum clinical management and intervention for people with FRDA.

Topical brinzolamide (Azopt) versus placebo in the treatment of infantile nystagmus syndrome (INS)

PURPOSE

To test the hypothesis that the topical carbonic anhydrase inhibitor brinzolamide (Azopt) has beneficial effects versus placebo on measures of nystagmus and visual acuity in adult subjects with infantile nystagmus syndrome (INS).

DESIGN

Prospective, cross-over, double masked clinical trial.

METHODS

SETTING

Single centre.

STUDY POPULATION

Five subjects ≥18 years old with typical INS and best-binocular visual acuity in their primary position null zone ETDRS 55 letters to 85 letters (20/200 to 20/50) and had no previous treatment for nystagmus.

INTERVENTION

In a randomised order, each subject received one drop of Azopt or placebo in both eyes three times a day separated by a washout period of at least a week followed by Azopt or placebo in both eyes three times a day; thus each subject got the drug and placebo, each acting as his or her own control.

OUTCOME MEASURES

The nystagmus acuity function and INS waveforms obtained from eye movement recordings, binocular optotype visual acuity, using the ETDRS protocol analysed individually and as a group before and after Azopt and placebo.

RESULTS

Versus placebo and baseline measures, topical Azopt significantly improved; INS waveform characteristics in the primary position null zone, group mean values of the nystagmus acuity function across gaze (p<0.01) and group mean ETDRS binocular letter visual acuity (p<0.05). There was a predictable decrease in intraocular pressure (IOP) without any systemic or ocular adverse events.

CONCLUSIONS

Although a prospective large-scale clinical trial is needed to prove effectiveness, an eye-drop-based therapy for INS may emerge as a viable addition to optical, surgical, behavioural and systemic drug therapies for INS.

TRIAL REGISTRATION NUMBER

NCT01312402.

A new measure of nystagmus acuity

AIM

To construct a new visual acuity measuring function for congenital nystagmus (CN) patients by studying the relationships between acuity, velocities and positions of the eye.

METHODS

After assessing the relationship between acuity, movement velocities and positions of the eye separately, a new function, which we call the automated nystagmus acuity function (ANAF), was constructed to measure the visual acuity of CN patients. Using a high-speed digital video system working at 500 frames per second, each eye was calibrated during monocular fixation. Twenty-six recorded nystagmus data were selected randomly. Using nystagmus waveforms, the best vision position (foveation period) and visual acuity were analyzed in three groups of subjects, and then all outputs were compared with the well-known expanded nystagmus acuity function (NAFX) and ANAF. Standard descriptive statistics were used to summarize the outputs of the two programs.

RESULTS

Foveation periods were brief intervals in the CN waveform when the image was on or near the fovea and eye velocity was relatively slow. Results showed good visual acuity happened during the period when velocity was low and the eye position was near the zero position, which fitted the foveation periods. The data analyzed with NAFX and ANAF had a correlation coefficient of 0.934276, with an average error of -0.00973.

CONCLUSION

The results from ANAF and NAFX analyses showed no significant difference. The NAFX manually identifies foveation eye positions and produces accurate measurements. The ANAF, however, can be calculated simply using the factors eye position and velocity, and it automatically calculates the ANAF without the need to manually identify foveation eye positions.

Periodic alternating nystagmus caused by a medullary lesion in acute disseminated encephalomyelitis

OBJECTIVE

To document a patient with periodic alternating nystagmus (PAN) caused by acute disseminated encephalomyelitis (ADEM) and suggest a mechanism to explain her PAN.

PATIENT

A 34-year-old woman with PAN caused by ADEM.

INTERVENTION

Diagnostic.

RESULTS

The patient complained of severe disequilibrium from the disease onset. Four years after onset, when she visited us, the patient exhibited prominent PAN consisting of alternating rightward and leftward components, which cycled about every 90 seconds and were accompanied by a 5-second translating phase with downbeating nystagmus. Eye movement analysis that separated the horizontal and vertical components revealed the presence of downbeating movements throughout all phases of the PAN. ENG recordings revealed slightly saccadic pursuit, slightly impaired optokinetic eye movement and an absence of visual suppression of the caloric response. MRI recorded at the onset of the disease revealed lesions in the medulla, the spinal cord at the C2 level, and the frontal horn of the left lateral ventricle, but not the cerebellum.

CONCLUSION

We attribute this patient's PAN to impairment of the nucleus prepositus hypoglossi in the medulla, which plays a role in the velocity storage system. In addition, cerebellar dysfunction is indicated by the occurrence of PAN while fixating.

Oculopalatal tremor: current concepts and new observations

PURPOSE OF REVIEW

Oculopalatal tremor (OPT) is an acquired disorder resulting from the interruption of a specific brainstem circuitry, the dentato-rubro-olivary pathway or Guillain-Mollaret triangle. The recent literature on OPT and olivary hypertrophy was reviewed with specific interest regarding causes, diagnostic procedures, physiopathology and therapies.

RECENT FINDINGS

OPT is associated with inferior olivary hypertrophy, and recent findings have provided a better understanding of its intimate mechanisms. A dual-mechanism model, combining an oscillator (inferior olive) and a modulator/amplifier (cerebellum), best explains the development of OPT. Electrotonic coupling and specific Ca channels contribute to oscillations of inferior olivary nucleus neurons in OPT. Improvement of visual symptoms can be achieved with oral gabapentin or memantine.

SUMMARY

Both the neuronal circuitry and the physiopathology of OPT are now better understood. This opens up an era of specific therapy for this rare cause of disabling oscillopsia.