Combining recessions (nystagmus and strabismus) with tenotomy improved visual function and decreased oscillopsia and diplopia in acquired downbeat nystagmus and in horizontal infantile nystagmus syndrome

Two-muscle surgical treatment of a compensatory head tilt in an adult with acquired downbeat nystagmus

Kestenbaum-Anderson-like operations have proven beneficial in treatment of compensatory head tilt in patients with infantile nystagmus. However, their use in acquired vertical nystagmus in adults with head tilt has rarely been reported. Presented here is a case of a 52-year-old woman with acquired downbeat nystagmus with a significant head tilt who responded to a simple two-muscle surgery involving the superior recti. Cyclovertical muscle surgery should be considered a viable option in such patients who are refractory to medical intervention. Additionally, it appears that four-muscle vertical muscle recessions (two muscles per eye) may not be necessary to dampen vertical nystagmus since good results can be obtained with a single muscle recession bilaterally.

Clinical and Electrophysiological Outcomes After Eye Muscle Surgery in 81 Adults With Infantile Nystagmus Syndrome

PURPOSE

To characterize the effects of eye muscle surgery on patients older than 18 years with infantile nystagmus syndrome (INS) who have had only optical treatment.

METHODS

This was a prospective, single-center, interventional case series analysis of clinical and electro-phyisological data before and after surgery. Outcome measures included: clinical characteristics, surgical procedure, and preoperative and postoperative binocular best corrected visual acuity (BCVA) in the null position, anomalous head posture (AHP), contrast sensitivity, strabismic deviation, and nystagmus acuity function (NAFX). Postoperative data used were collected for a minimum of 12 months after surgery. Parametric and non-parametric statistical analysis of the outcome measures was performed.

RESULTS

Ages ranged from 18 to 72 years (average: 36 years) and follow-up from 12 to 74 months (average: 26 months). A surgical algorithm of nine separate procedures involving at least two recti muscles on each eye was used for each patient. Most patients had associated systemic and/or ocular diagnoses, including albinism (35%), amblyopia (23%), optic nerve or retinal disorders (48%), refractive error (80%), AHP (44%), aperiodicity (27%), and strabismus (69%). There were no serious surgical complications, with a reoperation rate of 12%. There were significant group mean increases in BVCA, AHP, contrast sensitivity, strabismic deviation, and NAFX after surgery. Sixty percent of patients who were legally ineligible for driving prior to surgery became eligible after eye muscle surgery.

CONCLUSIONS

Adult patients with INS showed sustained improvement in many afferent and efferent measures of visual function after eye muscle surgery. [J Pediatr Ophthalmol Strabismus. 2021;58(2):93-104.].

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.

Effects of augmented tenotomy and reattachment in the infantile nystagmus syndrome

PURPOSE

To test the hypothesis that augmented tenotomy and reattachment surgery (AT-R), which involves placing an additional suture in each distal tendon during the 4-muscle tenotomy and reattachment (T-R) or other infantile nystagmus syndrome (INS) procedures, could increase the beneficial effects of many types of extraocular muscle (EOM) surgery to treat INS.

METHODS

Both infrared reflection and high-speed digital video systems were used to record the eye movements in 4 patients with INS before and after AT-R surgery. Data were analyzed using the eXpanded Nystagmus Acuity Function (NAFX) that is part of the OMtools software.

RESULTS

Placement of the augmentation suture did not interfere with Kestenbaum, Anderson, bilateral medial rectus muscle recession, or T-R surgeries. The therapeutic effects of AT-R were similar to but not equal to those from the traditional single-suture surgeries (ie, broadening longest foveation domain [LFD] but no improvement of NAFX peak). The average of the NAFX percent improvements after AT-R was within 31% of those estimated from NAFX values before T-R; the average of the percent broadenings of the LFD values after AT-R was within 16%.

CONCLUSIONS

The AT-R does not improve the foveation quality in INS above the traditional T-R surgery. It is not improved by an additional suture; indeed, some improvements may be diminished by the added suture. The hypothesized augmented-tendon suture technique (sans tenotomy) has been modified and remains to be tested.

Oculomotor neurocircuitry, a structural connectivity study of infantile nystagmus syndrome

Infantile nystagmus syndrome (INS) is one of the leading causes of significant vision loss in children and affects about 1 in 1000 to 6000 births. In the present study, we are the first to investigate the structural pathways of patients and controls using diffusion tensor imaging (DTI). Specifically, three female INS patients from the same family were scanned, two sisters and a mother. Six regions of interest (ROIs) were created manually to analyze the number of tracks. Additionally, three ROI masks were analyzed using TBSS (Tract-Based Spatial Statistics). The number of fiber tracks was reduced in INS subjects, compared to normal subjects, by 15.9%, 13.9%, 9.2%, 18.6%, 5.3%, and 2.5% for the pons, cerebellum (right and left), brainstem, cerebrum, and thalamus. Furthermore, TBSS results indicated that the fractional anisotropy (FA) values for the patients were lower in the superior ventral aspects of the pons of the brainstem than in those of the controls. We have identified some brain regions that may be actively involved in INS. These novel findings would be beneficial to the neuroimaging clinical and research community as they will give them new direction in further pursuing neurological studies related to oculomotor function and provide a rational approach to studying INS.

Fusion maldevelopment (latent/manifest latent) nystagmus syndrome: effects of four-muscle tenotomy and reattachment

PURPOSE

To examine the waveform and clinical effects of the four-muscle tenotomy and reattachment procedure in fusion maldevelopment nystagmus syndrome (FMNS) and to compare them to those documented in infantile nystagmus syndrome (INS) and acquired nystagmus.

METHODS

Both infrared reflection and high-speed digital video systems were used to record the eye movements in a patient with FMNS (before and after tenotomy and reattachment). Data were analyzed using the eXpanded Nystagmus Acuity Function (NAFX) that is part of the OMtools software. Model simulations and predictions were performed using the authors' behavioral ocular motor system model in MATLAB Simulink (The MathWorks, Inc., Natick, MA).

RESULTS

The model predicted, and the patient's data confirmed, that the tenotomy and reattachment procedure produces improvements in FMN waveforms across a broader field of gaze and decreases the Alexander's law variation. The patient's tenotomy and reattachment plots of NAFX after surgery versus gaze angle were higher and had lower slope than before surgery. Clinically, despite moderate improvements in both peak measured acuity and stereoacuity, dramatic improvements in the patient's abilities and lifestyle resulted.

CONCLUSIONS

The four-muscle tenotomy and reattachment nystagmus surgery produced beneficial therapeutic effects on FMN waveforms that are similar to those demonstrated in INS and acquired nystagmus. These results support the authors' prior recommendation that tenotomy and reattachment nystagmus should be added to required strabismus procedures in patients who also have FMNS (ie, perform tenotomy and reattachment on all unoperated muscles in the plane of the nystagmus). Furthermore, when strabismus surgery is not required, four-muscle tenotomy and reattachment may be used to improve FMN waveforms and visual function.

Symptomatic treatment and management of multiple sclerosis

The range of symptoms which occur in multiple sclerosis (MS) can have disabling functional consequences for patients and lead to significant reductions in their quality of life. MS symptoms can also interact with each other, making their management challenging. Clinical trials aimed at identifying symptomatic therapies have generally been poorly designed and have tended to be underpowered. Therefore, the evidence base for the management of MS symptoms with pharmacologic therapies is not strong and tends to rely upon open-label studies, case reports, and clinical trials with small numbers of patients and poorly validated clinical outcome measures. Recently, there has been a growing interest in the management of MS symptoms with pharmacologic treatments, and better-designed, randomized, double-blind, controlled trials have been reported. This chapter will describe the evidence base predominantly behind the various pharmacologic approaches to the management of MS symptoms, which in most, if not all, cases, requires multidisciplinary input. Drugs routinely recommended for individual symptoms and new therapies, which are currently in the development pipeline, will be reviewed. More interventional therapies related to symptoms that are refractory to pharmacotherapy will also be discussed, where relevant.

Treatment of nystagmus

OPINION STATEMENT

Patients with congenital and acquired forms of nystagmus are commonly encountered in clinical practice. Many report visual symptoms, such as oscillopsia and blurred vision, which can be alleviated if the nystagmus can be suppressed. Pharmacologic, optical, and surgical treatments are available, with the choice of treatment depending on the characteristics of the nystagmus and the severity of the associated visual symptoms. Downbeat nystagmus can be treated with 4-aminopyridine, 3,4-diaminopyridine, or clonazepam. Upbeat nystagmus can be reduced with memantine, 4-aminopyridine, or baclofen. Torsional nystagmus may respond to gabapentin. Acquired pendular nystagmus in patients with multiple sclerosis is often partially suppressed by gabapentin or memantine. Acquired pendular nystagmus in patients with oculopalatal tremor can respond to gabapentin, memantine, or trihexyphenidyl. Although acquired periodic alternating nystagmus is often completely suppressed by baclofen, memantine can be effective in refractory cases. Seesaw nystagmus can be reduced with alcohol, clonazepam, or memantine. Infantile nystagmus may not cause significant visual symptoms if "foveation periods" are well developed, but the nystagmus can be treated in symptomatic patients with gabapentin, memantine, acetazolamide, topical brinzolamide, contact lenses, or base-out prisms to induce convergence. Several surgical therapies have also been reported to improve infantile nystagmus syndrome (INS), but selection of the appropriate therapy requires preoperative evaluation of visual acuity and nystagmus intensity in different gaze positions. Other treatment options for nystagmus include botulinum toxin injections into the extraocular muscles or retrobulbar space. Electro-optical devices are currently being developed, in order to noninvasively negate the visual consequences of nystagmus.

What we know about the generation of nystagmus and other ocular oscillations: are we closer to identifying therapeutic targets?

Mechanisms underlying acquired nystagmus are better understood than those leading to infantile nystagmus. Accordingly, further progress has been made in the development of effective therapies for acquired nystagmus, mainly through pharmacological interventions. Some of these therapies have been developed under the guidance of findings from experimental animal models. Although mechanisms behind infantile nystagmus are less understood, progress has been made in determining the genetic basis of nystagmus and characterizing associated sensory deficits. Pharmacological, surgical, and other treatments options for infantile nystagmus are now emerging. Further investigations are required for all forms of nystagmus to produce high-quality evidence, such as randomized controlled trials, upon which clinicians can make appropriate treatment decisions.

Therapy for nystagmus

Pathological forms of nystagmus and their visual consequences can be treated using pharmacological, optical, and surgical approaches. Acquired periodic alternating nystagmus improves following treatment with baclofen, and downbeat nystagmus may improve following treatment with aminopyridines. Gabapentin and memantine are helpful in reducing acquired pendular nystagmus due to multiple sclerosis. Ocular oscillations in oculopalatal tremor may also improve following treatment with memantine or gabapentin. The infantile nystagmus syndrome (INS) may have only a minor impact on vision if "foveation periods" are well developed, but symptomatic patients may benefit from treatment with gabapentin, memantine, or base-out prisms to induce convergence. Several surgical therapies are also reported to improve INS, but selection of the optimal treatment depends on careful evaluation of visual acuity and nystagmus intensity in various gaze positions. Electro-optical devices are a promising and novel approach for treating the visual consequences of acquired forms of nystagmus.

Neural circuit involved in idiopathic infantile nystagmus syndrome based on FMRI

PURPOSE

To identify the neural circuitry of idiopathic infantile nystagmus syndrome (INS), characterized by an early onset alternating series of slow and rapid eye movements that can manifest in different waveforms and genetic lines. The neural circuitry of INS is currently unknown.

METHODS

A novel functional magnetic resonance imaging (fMRI) method, referred to as the null zone fMRI technique, was used to identify the neural circuitry for INS. In the null zone fMRI technique, a gaze position with minimal nystagmus within the null zone was linked to the fMRI "off" condition and a gaze position with robust nystagmus outside of the null zone was linked to the fMRI "on" condition. Eye movements were monitored with an fMRI compatible eye tracker and observed in real time to ensure subject compliance in "on" and "off" states. Subjects with INS (n = 4) included three family members (a mother and two daughters) with presumed autosomal dominant INS, as well as age- and gender-matched normal controls (n = 3).

RESULTS

Three of four subjects with INS demonstrated significant increased activation of the declive of the cerebellum, whereas no normal subjects under identical conditions showed activation of the declive of the cerebellum. Both groups showed significant activation in the occipital lobe (Brodmann areas 17, 18, 19, and cuneus).

CONCLUSION

A novel fMRI method demonstrated that the declive of the cerebellum is actively involved in INS. These are the first results to identify the cerebellum, and specifically the declive, as a possible site involved in the ocular motor dysfunction known as INS.

Improvement in visual acuity following surgery for correction of head posture in infantile nystagmus syndrome

PURPOSE

To report the effect of the abnormal head posture (AHP) correcting procedures on the visual acuity improvement in patients with infantile nystagmus syndrome (INS) and the visual acuity improvement outcomes in different AHP correcting surgeries in INS.

METHODS

This was a prospective, non-randomized, interventional study. Twenty-eight patients underwent the Anderson-Kestenbaum procedure or the modified Anderson procedure with or without tenotomy of at least one horizontal recti for correction of AHP. Best-corrected binocular null zone acuity and degree of AHP was recorded preoperatively and compared with those done 1 month postoperatively.

RESULTS

The average null zone logarithm of the minimum angle of resolution acuity was 0.42 preoperatively, which improved significantly to 0.33 postoperatively (P = .002). The AHP ranged from 10° to 40° (mean: 20.89°), which improved significantly to a mean of 3.21° (P = .000). No significant difference (P = .65) was found in the visual acuity improvement among patients who underwent the Anderson-Kestenbaum procedure or the modified Anderson procedure with or without tenotomy. No significant difference in the visual acuity improvement was seen in patients who underwent tenotomy of at least one horizontal rectus muscle along with the modified Anderson procedure compared to those who underwent the modified Anderson procedure alone (P = .28).

CONCLUSION

The procedures used mainly for correction of AHP in INS do yield significant improvement in the visual acuity. This improvement is seen in patients undergoing surgery for both horizontal and vertical AHP.

Nystagmus and saccadic intrusions

We review current concepts of nystagmus and saccadic oscillations, applying a pathophysiological approach. We begin by discussing how nystagmus may arise when the mechanisms that normally hold gaze steady are impaired. We then describe the clinical and laboratory evaluation of patients with ocular oscillations. Next, we systematically review the features of nystagmus arising from peripheral and central vestibular disorders, nystagmus due to an abnormal gaze-holding mechanism (neural integrator), and nystagmus occurring when vision is compromised. We then discuss forms of nystagmus for which the pathogenesis is not well understood, including acquired pendular nystagmus and congenital forms of nystagmus. We then summarize the spectrum of saccadic disorders that disrupt steady gaze, from intrusions to flutter and opsoclonus. Finally, we review current treatment options for nystagmus and saccadic oscillations, including drugs, surgery, and optical methods. Examples of each type of nystagmus are provided in the form of figures.

Effects of acetazolamide on infantile nystagmus syndrome waveforms: comparisons to contact lenses and convergence in a well-studied subject

AIM

To determine if acetazolamide, an effective treatment for certain inherited channelopathies, has therapeutic effects on infantile nystagmus syndrome (INS) in a well-studied subject, compare them to other therapies in the same subject and to tenotomy and reattachment (T&R) in other subjects.

METHODS

Eye-movement data were taken using a high-speed digital video recording system. Nystagmus waveforms were analyzed by applying an eXpanded Nystagmus Acuity Function (NAFX) at different gaze angles and determining the Longest Foveation Domain (LFD).

RESULTS

Acetazolamide improved foveation by both a 59.7% increase in the peak value of the NAFX function (from 0.395 to 0.580) and a 70% broadening of the NAFX vs Gaze Angle curve (the LFD increased from 20° to 34°). The resulting U-shaped improvement in the percent NAFX vs Gaze Angle curve, varied from ~60% near the NAFX peak to over 1000% laterally. The therapeutic improvements in NAFX from acetazolamide (similar to T&R) were intermediate between those of soft contact lenses and convergence, the latter was best; for LFD improvements, acetazolamide and contact lenses were equivalent and less effective than convergence. Computer simulations suggested that damping the central oscillation driving INS was insufficient to produce the foveation improvements and increased NAFX values.

CONCLUSION

Acetazolamide resulted in improved-foveation INS waveforms over a broadened range of gaze angles, probably acting at more than one site. This raises the question of whether hereditary INS involves an inherited channelopathy, and whether other agents with known effects on ion channels should be investigated as therapy for this condition.

Eye muscle surgery for infantile nystagmus syndrome in the first two years of life

Purpose:

To report visual and elctrophysioloigcal effects of eye muscle surgery in young patients with infantile nystagmus syndrome (INS).

Methods:

Prospective, interventional case cohort of 19 patients aged under 24 months who were operated on for combinations of strabismus, an anomalous head posture, and nystagmus. All patients were followed at least nine months. Outcome measures, part of an institutionally approved study, included Teller acuity, head position, strabismic deviation, and eye movement recordings, from which waveform types and a nystagmus optimal foveation fraction (NOFF). Computerized parametric and nonparametric statistical analysis of data were perfomed using standard software on both individual and group data.

Results:

Age averaged 17.7 months (13.1-month follow-up). Thirteen (68%) patients had associated optic nerve or retinal disease. 42% had amblyopia, 68% had refractive errors. Group means in binocular Teller acuity (P < 0.05), strabismic deviation (P < 0.05), head posture (P < 0.001), and the NOFF measures (P < 0.01) from eye movement recordings improved in all patients. There was a change in null zone waveforms to more favorable jerk types. There were no reoperations or surgical complications.

Conclusions:

Surgery on the extraocular muscles in patients aged less than two years with INS results in improvements in multiple aspects of ocular motor and visual function.

Two hypothetical nystagmus procedures: augmented tenotomy and reattachment and augmented tendon suture (Sans tenotomy)

PURPOSE

To review the hypothetical mechanism and therapeutic benefits of the four-muscle tenotomy and reattachment (T&R) procedure using knowledge accrued over the 10 years since its proposal; to describe an augmented tendon suture (ATS) technique to improve the procedure based on one of the originally suggested alternative methods (mechanical); and to hypothesize a new ATS procedure to achieve the same therapeutic benefits without extraocular muscle tenotomy or reattachment to the globe.

METHODS

Standard surgical methods were used.

RESULTS

The T&R procedure damps and improves infantile nystagmus syndrome (INS) waveforms, improves eXtended Nystagmus Acuity Function (NAFX) values, broadens the NAFX peak versus gaze angle, and damps slow eye movements but not saccades. The T&R procedure also damps acquired pendular and downbeat nystagmus, decreasing the patients' oscillopsia, and lowers the target acquisition time in INS.

CONCLUSION

The T&R procedure directly affects only the enthesis of the tendon; there is idiosyncratic variation in the distribution of afferent fibers in the tendons. The ATS technique consists of placing several additional sutures in the tendon proximal to the tenotomy. Based on the hypothetical proprioceptive mechanism for the beneficial effects of the T&R procedure, the authors hypothesize that the ATS technique will maximize the therapeutic benefits and that an ATS procedure, using only tendon sutures without tenotomy, will duplicate the therapeutic effects of T&R. Eliminating the tenotomy component results in a simpler procedure more suitable for single-session, multi-muscle surgery that may be required for improving the waveforms of multiplanar nystagmus and less prone to cause complications.

Extraocular proprioception and new treatments for infantile nystagmus syndrome

Our goal is to develop the proprioceptive hypothesis for nystagmus damping; and present the resulting therapies for the treatment of infantile nystagmus syndrome (INS) and acquired nystagmus. Contact lenses, cutaneous stimulation, and neck-muscle vibration damped INS. Four-muscle tenotomy and reattachment was hypothesized as a treatment for INS in 1979 and successfully demonstrated to improve foveation in a canine model of INS and seesaw nystagmus in 1998 and in humans with INS (masked-data, NEI Clinical Trial) in 2003. Subsequently, tenotomy successfully damped acquired pendular nystagmus and oscillopsia in two MS patients and downbeat nystagmus in another. Tenotomy, used in isolation or combination with existing nystagmus and strabismus surgeries, damps different types of nystagmus in their plane of action. Recent neuroanatomical and neurophysiological discoveries support the hypothesis that proprioception is the mechanism for INS damping and allow more realistic models of peripheral ocular motor pathways.

An update on acquired nystagmus

Proper evaluation and treatment of acquired nystagmus requires accurate characterization of nystagmus type and visual effects. This review addresses important historical and examination features of nystagmus and current concepts of pathogenesis and treatment of gaze-evoked nystagmus, nystagmus due to vision loss, acquired pendular nystagmus, peripheral and central vestibular nystagmus, and periodic alternating nystagmus.