Randomized trial of bilateral gene therapy injection for m.11778G>A MT-ND4 Leber optic neuropathy.

Leber hereditary optic neuropathy (LHON) is an important example of mitochondrial blindness with the m.11778G>A mutation in the MT-ND4 gene being the most common disease-causing mtDNA variant worldwide. The REFLECT phase 3 pivotal study is a randomized, double-masked, placebo-controlled trial investigating the efficacy and safety of bilateral intravitreal injection of lenadogene nolparvovec in patients with a confirmed m.11778G>A mutation, using a recombinant adeno-associated virus vector 2, serotype 2 (rAAV2/2-ND4). The first-affected eye received gene therapy; the fellow (affected/not-yet-affected) eye was randomly injected with gene therapy or placebo. The primary end point was the difference in change from baseline of best-corrected visual acuity (BCVA) in second-affected/not-yet-affected eyes treated with lenadogene nolparvovec versus placebo at 1.5 years post-treatment, expressed in logarithm of the minimal angle of resolution (LogMAR). Forty-eight patients were treated bilaterally and 50 unilaterally. At 1.5 years, the change from baseline in BCVA was not statistically different between second-affected/not-yet-affected eyes receiving lenadogene nolparvovec and placebo (primary end point). A statistically significant improvement in BCVA was reported from baseline to 1.5 years in lenadogene nolparvovec-treated eyes: -0.23 LogMAR for the first-affected eyes of bilaterally treated patients (P < 0.01); and -0.15 LogMAR for second-affected/not-yet-affected eyes of bilaterally treated patients and the first-affected eyes of unilaterally treated patients (P < 0.05). The mean improvement in BCVA from nadir to 1.5 years was -0.38 (0.052) LogMAR and -0.33 (0.052) LogMAR in first-affected and second-affected/not-yet-affected eyes treated with lenadogene nolparvovec, respectively (bilateral treatment group). A mean improvement of -0.33 (0.051) LogMAR and -0.26 (0.051) LogMAR was observed in first-affected lenadogene nolparvovec-treated eyes and second-affected/not-yet-affected placebo-treated eyes, respectively (unilateral treatment group). The proportion of patients with one or both eyes on-chart at 1.5 years was 85.4% and 72.0% for bilaterally and unilaterally treated patients, respectively. The gene therapy was well tolerated, with no systemic issues. Intraocular inflammation, which was mostly mild and well controlled with topical corticosteroids, occurred in 70.7% of lenadogene nolparvovec-treated eyes versus 10.2% of placebo-treated eyes. Among eyes treated with lenadogene nolparvovec, there was no difference in the incidence of intraocular inflammation between bilaterally and unilaterally treated patients. Overall, the REFLECT trial demonstrated an improvement of BCVA in LHON eyes carrying the m.11778G>A mtDNA mutation treated with lenadogene nolparvovec or placebo to a degree not reported in natural history studies and supports an improved benefit/risk profile for bilateral injections of lenadogene nolparvovec relative to unilateral injections.

Geographic and socioeconomic access disparities to Phase 3 clinical trials in ophthalmology in the United States.

BACKGROUND/OBJECTIVE: To identify geographic and socioeconomic variables associated with residential proximity to Phase 3 ophthalmology clinical trial sites. METHODS: The geographic location of clinical trial sites for Phase 3 clinical trials in ophthalmology was identified using ClinicalTrials.gov. Driving time from each United States (US) census tract centroid to nearest clinical trial site was calculated using real traffic patterns. Travel data were crosslinked to census-tract level public datasets from United States Census Bureau American Community Survey (ACS). Cross-sectional multivariable regression was used to identify associations between census-tract sociodemographic factors and driving time (>60 min) from each census tract centroid to the nearest clinical trial site. RESULTS: There were 2330 unique clinical trial sites and 71,897 census tracts. Shortest median time was to retina sites [33.7 min (18.7, 70.1 min)]. Longest median time was to neuro-ophthalmology sites [119.8 min (48.7, 240.4 min)]. Driving >60 min was associated with rural tracts [adjusted odds ratio (aOR) 7.60; 95% CI (5.66-10.20), p < 0.0001]; Midwest [aOR 1.84(1.15-2.96), p = 0.01], South [aOR 2.57 (1.38-4.79), p < 0.01], and West [aOR 2.52 (1.52-4.17), p < 0.001] v. Northeast; and tracts with higher visual impairment [aOR 1.07 (1.03-1.10), p < 0.001)]; higher poverty levels [4th v.1st Quartile of population below poverty, aOR 2.26 (1.72-2.98), p < 0.0001]; and lower education levels [high school v. Bachelor's degree or higher aOR 1.02 (1.00-1.03), p = 0.0072]. CONCLUSIONS: There are significant geographic and socioeconomic disparities in access to ophthalmology clinical trial sites for rural, non-Northeastern, poorer, and lower education level census tracts, and for census tracts with higher levels of self-reported visual impairment.

Safety of Lenadogene Nolparvovec Gene Therapy Over 5 Years in 189 Patients With Leber Hereditary Optic Neuropathy.

PURPOSE: To evaluate the safety profile of lenadogene nolparvovec (Lumevoq) in patients with Leber hereditary optic neuropathy. DESIGN: Pooled analysis of safety data from 5 clinical studies. METHODS: A total of 189 patients received single unilateral or bilateral intravitreal injections of a recombinant adeno-associated virus 2 (rAAV2/2) vector encoding the human wild-type ND4 gene. Adverse events (AEs) were collected throughout the studies, up to 5 years. Intraocular inflammation and increased intraocular pressure (IOP) were ocular AEs of special interest. Other assessments included ocular examinations, vector bio-dissemination, and systemic immune responses against rAAV2/2. RESULTS: Almost all patients (95.2%) received 9 × 1010 viral genomes and 87.8% had at least 2 years of follow-up. Most patients (75.1%) experienced at least one systemic AE, but systemic treatment-related AEs occurred in 3 patients; none were serious. Intraocular inflammation was reported in 75.6% of lenadogene nolparvovec-treated eyes. Almost all intraocular inflammations occurred in the anterior chamber (58.8%) or in the vitreous (40.3%), and were of mild (90.3%) or moderate (8.8%) intensity; most resolved with topical corticosteroids alone. All IOP increases were mild to moderate in intensity. No AE led to study discontinuation. Bio-dissemination of lenadogene nolparvovec and systemic immune response were limited. The safety profile was comparable for patients treated bilaterally and unilaterally. CONCLUSIONS: Lenadogene nolparvovec had a good overall safety profile with excellent systemic tolerability, consistent with limited bio-dissemination. The product was well tolerated, with mostly mild ocular side effects responsive to conventional ophthalmologic treatments.

Mismatch in Supply and Demand for Neuro-Ophthalmic Care.

BACKGROUND: Previous research suggests the number of neuro-ophthalmologists in the United States may be below a level that provides sufficient access to neuro-ophthalmic care in much of the United States. However, national estimates of the amount of clinical time spent on neuro-ophthalmology are lacking. METHODS: The North American Neuro-Ophthalmology Society administered a survey on professional time allocation to its active members. Survey response was 95%. The survey characterized the hours each week each respondent allocated to overall work, clinical work, clinical work in ophthalmology/neurology, and clinical work in neuro-ophthalmology specifically. The survey additionally collected information regarding demographics, current wait times to be seen for new patients, and the difference in clinical time spent in neuro-ophthalmology spent between the current day compared with that shortly after completing clinical training. Linear regression was used to identify potential relationships between the above and average wait time. RESULTS: On average, responding physicians spent 70% of their clinical time on neuro-ophthalmology. In 6 states, there were no reported practicing neuro-ophthalmologists, and in only 8 states was the clinical full-time equivalent to population ratio below the suggested threshold of 1 for every 1.2 million. The median wait time for a new patient was 6 weeks. This wait time was associated with the fraction of clinical time spent in neuro-ophthalmology (0.2 weeks longer wait for a 10 percentage point increase in the fraction of time spent in neuro-ophthalmology; P = 0.02), and suggestively associated with training (training in ophthalmology was associated with 1.0 week shorter wait time; P = 0.06). CONCLUSION: The survey suggests that neuro-ophthalmologists are unable to see patients in a timely manner and a decreasing number of clinicians are entering the field. Future interventions should be considered to incentivize neuro-ophthalmology training in ophthalmology and neurology residents such that the United States population is able to appropriately access neuro-ophthalmic care.

Lumbar Puncture for Diagnosis of Idiopathic Intracranial Hypertension in Typical Patients.

BACKGROUND: Patients with typical features of pseudotumor cerebri syndrome (PTCS) must undergo lumbar puncture (LP) to demonstrate elevated opening pressure and cerebrospinal fluid (CSF) analysis to rule out alternative diagnoses. As LP may be associated with significant morbidity, this study aims to determine its necessity in diagnosing typical PTCS. METHODS: Retrospective chart review at 3 university-based neuro-ophthalmology practices included women aged 18-45 years with body mass index >25, papilledema, negative neuroimaging, and who met criteria for PTCS or probable PTCS. RESULTS: One hundred fifty-six patients were enrolled. Seven (4.5%) had clinically insignificant CSF abnormalities. No diagnoses or management changed based on LP/CSF results. CONCLUSION: LP may not be routinely required in the initial evaluation of typical patients with PTCS evaluated by experienced clinicians We caution, however, that further prospective study is required to determine potential risks and benefits of LP as a tool in the diagnosis of IIH before recommending general practice changes.

Efficacy and Safety of Intravitreal Gene Therapy for Leber Hereditary Optic Neuropathy Treated within 6 Months of Disease Onset.

PURPOSE: To evaluate the efficacy of a single intravitreal injection of rAAV2/2-ND4 in subjects with visual loss from Leber hereditary optic neuropathy (LHON). DESIGN: RESCUE is a multicenter, randomized, double-masked, sham-controlled, phase 3 clinical trial. PARTICIPANTS: Subjects with the m.11778G>A mitochondrial DNA mutation and vision loss ≤6 months from onset in 1 or both eyes were included. METHODS: Each subject's right eye was randomly assigned (1:1) to treatment with rAAV2/2-ND4 (single injection of 9 × 1010 viral genomes in 90 µl) or to sham injection. The left eye received the treatment not allocated to the right eye. MAIN OUTCOME MEASURES: The primary end point was the difference of the change from baseline in best-corrected visual acuity (BCVA) between rAAV2/2-ND4-treated and sham-treated eyes at week 48. Other outcome measures included contrast sensitivity, Humphrey visual field perimetry, retinal anatomic measures, and quality of life. Follow-up extended to week 96. RESULTS: Efficacy analysis included 38 subjects. Mean age was 36.8 years, and 82% were male. Mean duration of vision loss at time of treatment was 3.6 months and 3.9 months in the rAAV2/2-ND4-treated eyes and sham-treated eyes, respectively. Mean baseline logarithm of the minimum angle of resolution (logMAR) BCVA (standard deviation) was 1.31 (0.52) in rAAV2/2-ND4-treated eyes and 1.26 (0.62) in sham-treated eyes, with a range from -0.20 to 2.51. At week 48, the difference of the change in BCVA from baseline between rAAV2/2-ND4-treated and sham-treated eyes was -0.01 logMAR (P = 0.89); the primary end point of a -0.3 logMAR (15-letter) difference was not met. The mean BCVA for both groups deteriorated over the initial weeks, reaching the worst levels at week 24, followed by a plateau phase until week 48, and then an improvement of +10 and +9 Early Treatment Diabetic Retinopathy Study letters equivalent from the plateau level in the rAAV2/2-ND4-treated and sham-treated eyes, respectively. CONCLUSIONS: At 96 weeks after unilateral injection of rAAV2/2-ND4, LHON subjects carrying the m.11778G>A mutation treated within 6 months after vision loss achieved comparable visual outcomes in the injected and uninjected eyes.

Bilateral visual improvement with unilateral gene therapy injection for Leber hereditary optic neuropathy.

REVERSE is a randomized, double-masked, sham-controlled, multicenter, phase 3 clinical trial that evaluated the efficacy of a single intravitreal injection of rAAV2/2-ND4 in subjects with visual loss from Leber hereditary optic neuropathy (LHON). A total of 37 subjects carrying the m.11778G>A (MT-ND4) mutation and with duration of vision loss between 6 to 12 months were treated. Each subject's right eye was randomly assigned in a 1:1 ratio to treatment with rAAV2/2-ND4 (GS010) or sham injection. The left eye received the treatment not allocated to the right eye. Unexpectedly, sustained visual improvement was observed in both eyes over the 96-week follow-up period. At week 96, rAAV2/2-ND4-treated eyes showed a mean improvement in best-corrected visual acuity (BCVA) of -0.308 LogMAR (+15 ETDRS letters). A mean improvement of -0.259 LogMAR (+13 ETDRS letters) was observed in the sham-treated eyes. Consequently, the primary end point, defined as the difference in the change in BCVA from baseline to week 48 between the two treatment groups, was not met (P = 0.894). At week 96, 25 subjects (68%) had a clinically relevant recovery in BCVA from baseline in at least one eye, and 29 subjects (78%) had an improvement in vision in both eyes. A nonhuman primate study was conducted to investigate this bilateral improvement. Evidence of transfer of viral vector DNA from the injected eye to the anterior segment, retina, and optic nerve of the contralateral noninjected eye supports a plausible mechanistic explanation for the unexpected bilateral improvement in visual function after unilateral injection.

Papilloedema from Dural Venous Sinus Compression by Meningiomas.

Intracranial mass lesions may cause intracranial hypertension secondary to venous hypertension when they compress the dural venous sinuses (DVS) and may present with isolated papilloedema, mimicking idiopathic intracranial hypertension. We report a series of 16 patients with isolated papilloedema related to meningiomas compressing the DVS seen from 2012 to 2016 at three institutions. Correct diagnosis was delayed in 10/16 patients and treatment required a multidisciplinary approach, often with multiple sequential interventions, including combinations of acetazolamide, cerebrospinal fluid-shunt, optic nerve sheath fenestration, surgical resection of the meningioma, radiation therapy, and endovascular venous stenting. Two patients also received anticoagulation for venous thrombosis secondary to venous sinus compression.

Gene therapy in optic nerve disease.

PURPOSE OF REVIEW: Highlight some of the recent advances in gene therapy and gene modification for optic nerve disease to promote axon regeneration, neuroprotection, and increased visual functioning. RECENT FINDINGS: Visual loss secondary to optic nerve damage occurs in numerous ophthalmologic and neurologic conditions. Damaged retinal ganglion cells (RGCs) do not regenerate once they undergo apoptosis after injury. Gene therapy has been studied to replace gene mutations in disorders affecting the optic nerve as well as to alter genes responsible for suppressing or activating pathways of optic nerve growth and regeneration. Recent clinical trials for Leber's Hereditary Optic Neuropathy have demonstrated safety and feasibility as potential future treatment. Animal studies utilizing gene therapy for optic nerve regeneration have shown various degrees of RGC axon regrowth and target reinnervation. Some studies have also successfully demonstrated a state of neuroprotection in RGCs allowing them to survive in greater numbers following injury. SUMMARY: Additional studies will have to evaluate long-term efficacy and safety of these potential treatments, as well as the consequences of manipulating tumor suppressor genes and oncogenes.

Efficacy of Orbital Color Doppler Imaging and Neuroimaging in the Diagnosis of Carotid Cavernous Fistulas.

PURPOSE: To evaluate the diagnostic sensitivity and specificity of orbital color Doppler imaging (CDI) and conventional neuroimaging (CT/MRI) compared with cerebral angiography in patients with carotid-cavernous fistulas (CCFs). METHODS: The study design was a retrospective patient chart and imaging review. The authors reviewed 655 charts of all patients who underwent CDI and neuroimaging (CT/MRI) between 2006 and 2015 at one institution. Sixty patients had a presumptive diagnosis of CCF without thrombosis. Thirty-seven patients with 43 events met the inclusion criteria of the study. The diagnostic sensitivity of the 3 noninvasive imaging modalities (CDI, CT, MRI) for CCF was compared with the gold standard 6-vessel cerebral angiography. Significance testing was performed using the 2-tailed Fisher test. RESULTS: Color Doppler imaging had high sensitivity (96.8%) but low specificity (41.7%) for the diagnosis of CCFs with anterior orbital findings. A negative CDI had more diagnostic value than a positive CDI. While an arterial wave form in the superior ophthalmic vein was the most common finding of CCF on CDI, enlargement of the superior ophthalmic vein was the only statistically significant finding. Posterior cortical venous drainage was noted in about 10% of the patients with indirect (low-flow) fistulas, who presented with unilateral orbital signs and symptoms, a finding not previously reported in the literature. CONCLUSION: Color Doppler imaging is a useful noninvasive, radiation-free modality for diagnosis of CCF with anterior drainage, with higher sensitivity than CT or MRI, but equivalent specificity. A significant limitation of CDI is the lack of usefulness in diagnosing fistulas with posterior cortical venous drainage, which carry a risk of intracerebral hemorrhage and stroke. In this series, 10% of unilateral CCFs with anterior orbital signs and symptoms showed angiographic evidence of posterior cortical venous drainage.

Transient ocular motor nerve palsies associated with presumed cranial nerve schwannomas.

BACKGROUND: Cranial nerve schwannomas are radiologically characterized by nodular cranial nerve enhancement on magnetic resonance imaging (MRI). Schwannomas typically present with gradually progressive symptoms, but isolated reports have suggested that schwannomas may cause fluctuating symptoms as well. METHODS: This is a report of ten cases of presumed cranial nerve schwannoma that presented with transient or recurring ocular motor nerve deficits. RESULTS: Schwannomas of the third, fourth, and fifth nerves resulted in fluctuating deficits of all 3 ocular motor nerves. Persistent nodular cranial nerve enhancement was present on sequential MRI studies. Several episodes of transient oculomotor (III) deficts were associated with headaches, mimicking ophthalmoplegic migraine. CONCLUSIONS: Cranial nerve schwannomas may result in relapsing and remitting cranial nerve symptoms.

Vision loss with bending over.

A 66-year-old African American man presented with episodic transient visual loss triggered by bending forward. The initial examination did not suggest intraocular pathology and the patient was nearly sent for vascular evaluation given his cardiovascular risk factors. Fundus photographs taken during an episode of visual loss suggested an intraocular process, however. Gonioscopy revealed a microhyphema causing a "snow globe" effect in the anterior chamber, most likely related to recent bleb manipulation in the affected eye.

Homonymous hemianopia due to Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis typically affecting multiple organ systems. We report 2 patients who presented with homonymous hemianopia and were ultimately diagnosed with biopsy-confirmed ECD. We review the spectrum of ECD and its treatment as well as histopathological and immunohistochemical differentiation from other histiocytic disorders.

Muscle cramping over the diagnosis.

A 44-year-old man with hypogonadism and adrenal insufficiency presented with transient blurred vision and halos around lights. Visual acuity was 20/20 in both eyes, and he had mild bilateral optic disk edema. Brain imaging was unremarkable, and lumbar puncture showed an opening pressure of 28.5 cm H2O with elevated protein. He also complained of muscle cramping, and magnetic resonance imaging of the spine demonstrated a heterogenous bone marrow signal. Bone survey showed a mixed lytic and sclerotic lesion within the left femur that proved to be a plasmacytoma. Serum protein electrophoresis had a small IgA spike, and plasma vascular endothelial growth factor (VEGF) was elevated. He was diagnosed with POEMS syndrome and underwent radiation to the plasmacytoma. Two years later he had a stable neuro-ophthalmologic exam with no signs of multiple myeloma. POEMS syndrome is a rare paraneoplastic syndrome from a plasma cell dyscrasia that may cause optic disk edema.

Optic nerve biopsy in the management of progressive optic neuropathy.

BACKGROUND: In cases of progressive optic neuropathy, diagnostic uncertainty often persists despite extensive work-up. Optic nerve biopsy (ONB) can be considered, especially when visual decline of the affected or fellow eye ensues despite empiric therapy. We aimed to evaluate both diagnostic and therapeutic utilities of ONB based on the long-term experience at a tertiary care institution. METHODS: This was a retrospective chart review of biopsies over 20 years at a single institution involving intrinsic or adherent optic nerve masses. Main outcome measures included the impact of tissue sampling on reaching a diagnosis and on guiding treatment. Secondary measures included vision in the eye of the ONB and the fellow eye. RESULTS: Fifteen patients with a mean age of 51.7 ± 17.4 years underwent biopsies. At the time of biopsy, visual acuity was no light perception in 8 (53%) eyes, light perception to counting fingers in 5 (33%), and 20/400 or better in 2 (13%). The fellow eye of 7 patients (47%) experienced some degree of sequential vision loss before biopsy. Seven specimens included en bloc biopsy of the nerve, 7 contained the dural sheath (usually with a portion of the optic nerve), and 1 only of the compressive mass. Six patients (40%) had tumors. Six of 8 inflammatory lesions biopsied required further clinical data to arrive at specific diagnoses. In one case, a clinical diagnosis could not be made. No patients experienced further vision loss in the fellow eye at last follow-up (median, 8 months). CONCLUSIONS: In diverse circumstances of progressive optic neuropathy, ONB can be beneficial in establishing the diagnosis. ONB can help direct specific local or systemic treatment, particularly when infectious or inflammatory etiologies are identified. ONB, if considered early in the disease course, can potentially halt or prevent vision loss when the fellow eye is threatened.

Intracranial malignancies occurring more than 20 years after radiation therapy for pituitary adenoma.

A 37-year-old woman developed a left third cranial nerve palsy 28 years after radiation for a nonsecreting pituitary adenoma. Imaging disclosed a left parasellar mass and a midbrain/pontine signal abnormality. Biopsy of the parasellar mass revealed a malignant sarcoma. The brainstem abnormality was presumptively diagnosed as a malignant glioma. A 63-year-old man developed a malignant astrocytoma of the left optic nerve and chiasm 23 years after partial excision and radiation of a nonsecreting pituitary adenoma. Both patients died of their malignancies. Although secondary malignancies have been described in this setting, such long latencies have not been reported.

Functional visual loss in idiopathic intracranial hypertension.

OBJECTIVE: To identify and describe patients with idiopathic intracranial hypertension (IIH) with concurrent functional visual loss (FVL). DESIGN: Observational, retrospective case series. PARTICIPANTS: Seventeen patients with IIH and FVL. METHODS: Clinical features were collected retrospectively. Data from 281 cases of IIH were analyzed for concurrence of FVL. MAIN OUTCOME MEASURES: Occurrence of FVL diagnosed at presentation or on subsequent follow-up. RESULTS: Seventeen patients had FVL and IIH. Of the 17 patients with FVL and IIH, 11 (65%) had FVL on presentation, with the remaining 6 patients developing FVL after initial presentation. Two patients in this cohort had documented recurrence of their IIH. There were several common patterns of FVL. All 17 patients had functional visual fields, with 82% having tubular fields and 71% exhibiting nonphysiologic constriction on perimetry testing. Seventy-six percent of patients had nerve/field mismatch showing no atrophic disc changes. Eighty-eight percent of patients had significant psychiatric, psychosocial, or other medical comorbidities. The majority of patients were managed surgically at some point in their clinical history, with 53% having nerve decompression, shunt, or both. Three patients had optic nerve sheath fenestrations after the diagnosis of FVL. CONCLUSIONS: Results suggest a high prevalence of FVL in IIH with a potential association with psychiatric illness and psychosocial stressors requiring careful consideration before surgical intervention. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Clinical course and prognosis of trochlear nerve schwannomas.

PURPOSE: To delineate the disease course and prognosis of patients with mass lesions of the fourth nerve presumed to be schwannomas. DESIGN: Nonrandomized retrospective case series. PARTICIPANTS: Thirty-seven consecutive cases of presumed trochlear nerve schwannoma from 9 tertiary university neuro-ophthalmology centers. METHODS: Cases were collected, and their clinical characteristics on presentation and follow-up are described. Inclusion criteria were brain magnetic resonance imaging (MRI) with a lesion suggestive of a schwannoma along the course of the fourth nerve. Exclusion criteria were other causes of fourth nerve palsy, such as congenital, traumatic or microvascular; normal (or lack of) initial brain MRI; lack of adequate clinical information; and disappearance of the lesion on subsequent follow-up brain MRI. MAIN OUTCOME MEASURES: Demographics of patients, presence of neurofibromatosis, symptoms on presentation, vertical deviation, lesion size (on presentation and follow-up), length of follow-up, and outcomes of treatment for lesions or diplopia. RESULTS: Seven patients were excluded and of the 30 patients included in our series, patients were predominantly male (77%) with a mean age of 51 years (range 9-102 years). In contrast with prior case reports, almost all of our cases had a fourth nerve palsy on presentation (29/30), often isolated. Mean follow-up was 3.1 years (range 0.2 months to 11.1 years). There was no significant difference between initial and follow-up lesion size (4.4 vs. 5 mm) for patients who did not receive treatment of lesions (P = 0.36). Only 3 patients underwent neurosurgical resection and an additional patient received gamma-knife radiotherapy. The majority of patients (24/30) did not pursue strabismus surgery for vertical diplopia. CONCLUSIONS: Patients with isolated fourth nerve palsy and small lesions of the fourth nerve have a good prognosis and should be followed with serial MRI scans without neurosurgical intervention unless they develop signs of brain stem compression. Most patients with diplopia and benign fourth nerve lesions typical of trochlear nerve schwannoma can adapt with either prism spectacles or no treatment at all, although strabismus surgery can be successful.