Monkeypox-Associated Central Nervous System Disease: A Case Series and Review.

OBJECTIVE: Monkeypox virus (MPXV) disease has been declared a public health emergency by the World Health Organization, creating an urgent need for neurologists to be able to recognize, diagnosis, and treat MPXV-associated neurologic disease. METHODS: Three cases of MPXV-associated central nervous system (CNS) disease occurring during the 2022 outbreak, and their associated imaging findings are presented, with 2 cases previously published in a limited capacity in a public health bulletin. RESULTS: Three previously healthy immunocompetent gay men in their 30s developed a febrile illness followed by progressive neurologic symptoms with presence of a vesiculopustular rash. MPXV nucleic acid was detected by polymerase chain reaction (PCR) from skin lesions of 2 patients, with the third patient having indeterminate testing but an epidemiologic link to a confirmed MPXV disease case. Cerebrospinal fluid demonstrated a lymphocytic pleocytosis, elevated protein, and negative MPXV-specific PCR. In 2 patients, magnetic resonance imaging of the brain and spine demonstrated partially enhancing, longitudinally extensive central spinal cord lesions with multifocal subcortical, basal ganglia, thalamic, cerebellar, and/or brainstem lesions. The third patient had thalamic and basal ganglia lesions. All patients received 14 days of tecovirimat, and 2 patients also received multiple forms of immunotherapy, including intravenous immunoglobulin, pulsed high-dose steroids, plasmapheresis, and/or rituximab. Good neurologic recovery was observed in all cases. INTERPRETATION: MPXV can be associated with CNS disease. It is unclear whether this is from a parainfectious immune-mediated injury or direct CNS viral invasion. ANN NEUROL 2023;93:893-905.

Effect of Head Position and Magnetic Resonance Sequence on Cochlear Implant-Related Artifact Size and Internal Auditory Canal Visibility.

HYPOTHESIS: To assess whether cochlear implant (CI)-related magnetic resonance imaging (MRI) artifact and visibility of the internal auditory canal (IAC) can be improved with head positioning and select MRI sequences. BACKGROUND: CI-related MRI artifact limits the use of CIs in otherwise good candidates because of the need for serial MRIs for monitoring of pathology. This most notably impacts patients with tumors of the cerebellopontine angle and IAC. METHODS: Two cadaver heads were implanted with either a Med-El CONCERT (fixed magnet) or SYNCHRONY (rotating magnet) device. Each head was imaged in a 1.5T scanner in 11 different positions. The SYNCHRONY-implanted head was also imaged in a 3.0T scanner in seven positions. Artifact size and IAC visibility (graded on a Likert scale) were measured for each head position by a neuroradiologist. RESULTS: The CONCERT CI produced significantly smaller artifact than the SYNCHRONY CI (effect size, 14.65 mm; p < 0.001). There was no significant difference between CI models in regard to IAC visibility. No head positions were statistically significantly better than neutral position for minimizing artifact size or IAC visibility, although some positions resulted in significantly larger artifact (effect sizes, 2.1-14.3 mm; p < 0.05) or significantly poorer IAC visibility (effect size, 1.4; p < 0.01). The T2 three-dimensional (CISS/FIESTA) sequence demonstrated significantly smaller artifact than T1 sequences, whereas T1 sequences demonstrated significantly better IAC visibility than T2 sequences. CONCLUSION: Head positioning and magnetic resonance sequence selection impact CI-related artifact size and IAC visibility.

RAPID Aneurysm: Artificial intelligence for unruptured cerebral aneurysm detection on CT angiography.

OBJECTIVES: Cerebral aneurysms may result in significant morbidity and mortality. Identification of these aneurysms on CT Angiography (CTA) studies is critical to guide patient treatment. Artificial intelligence platforms to assist with automated aneurysm detection are of high interest. We determined the performance of a semi-automated artificial intelligence software program (RAPID Aneurysm) for the detection of cerebral aneurysms. MATERIALS AND METHODS: RAPID Aneurysm was used to detect retrospectively the presence of cerebral aneurysms in CTA studies performed between January 2019 and December 2020. The gold standard was aneurysm presence and location as determined by the consensus of three expert neuroradiologists. Aneurysm detection accuracy, sensitivity, specificity, positive predictive value, negative predictive value, and positive and negative likelihood ratios by RAPID Aneurysm were determined. RESULTS: 51 patients (mean age, 56±15; 24 women [47.1%]) with a single CTA were included. A total of 60 aneurysms were identified. RAPID Aneurysm had a sensitivity of 0.950 (95% CI: 0.863-0.983), specificity of 1.000 (95% CI: 0.996-1.000), a positive predictive value (PPV) of 1.000 (95% CI: 0.937-1.000), a negative predictive value (NPV) of 0.997 (95% CI: 0.991-0.999), and an accuracy of 0.997 (95% CI: 0.991-0.999) for cerebral aneurysm detection. CONCLUSIONS: RAPID Aneurysm is highly accurate for the detection of cerebral aneurysms on CTA.

Understanding Patient Experiences, Opinions, and Actions Taken After Viewing Their Own Radiology Images Online: Web-Based Survey.

BACKGROUND: The ability for patients to directly view their radiology images through secure electronic portals is rare in the American health care system. We previously surveyed patients within our health system and found that a large majority wanted to view their own radiology images online, and we have since implemented this new feature. OBJECTIVE: We aim to understand patient experiences, opinions, and actions taken after viewing their own radiology images online. METHODS: We emailed a web-based survey to patients who recently viewed their radiology images via our electronic patient portal. RESULTS: We sent 1825 surveys to patients and received 299 responses (response rate 16.4%). Patients reported a favorable experience (258/299, 86.3% agree) viewing their radiology images online. Patients found value in reading their radiology reports (288/299, 96.3% agree) and viewing their images (267/299, 89.3% agree). Overall, patients felt that accessing and viewing their radiology images online increased their understanding of their medical condition (258/299, 82.9%), made them feel more in control and reassured (237/299, 79.2% and 220/299, 73.6%, respectively), and increased levels of trust (214/299, 71.6%). Only 6.4% (19/299) of the patients indicated concerns with finding errors, 6.4% (19/299) felt that viewing their images online made them worry more, and 7% (21/299) felt confused when viewing their images online. Of patients who viewed their images online, 45.2% (135/299) took no action with their images, 32.8% (98/299) saved a copy for their records, 25.4% (76/299) shared them with their doctor, and 14.7% (44/299) shared them with another doctor for a second opinion. A total of 9 patients (3%) shared their radiology images on Facebook, Instagram, or both, primarily to inform family and friends. Approximately 10.4% (31/299) of the patients had questions about their radiology images after viewing them online, with the majority (20/31, 65%) seeking out a doctor, and far fewer (5/31, 16%) choosing to ask a family member about their images. Finally, respondents viewed their images online using 1 or more devices, including computers, smartphones, tablets, or a combination of these devices. Approximately 26.7% (103/385) of the responses noted technical difficulties, with the highest incidence rate occurring with smartphones. CONCLUSIONS: We report the first known survey results from patients who viewed their own radiology images through a web-based portal. Patients reported high levels of satisfaction and increased levels of trust, autonomy, reassurance, and medical understanding. Only a small minority of patients expressed anxiety or confusion. We suggest that patient access to radiology images, such as patient access to radiology reports, is highly desired by patients and is operationally practical. Other health care institutions should consider offering patients access to their radiology images online in the pursuit of information transparency.

Intracranial meningioma surveillance using volumetrics from T2-weighted MRI.

BACKGROUND AND PURPOSE: The gold standard for imaging of meningiomas is MRI with gadolinium-based contrast agent. Due to increased costs, time, and uncertain chronic effects of gadolinium exposure, use of noncontrast T2-weighted imaging (T2WI) in lieu of contrast-enhanced MRI has been an increasing focus of research across various diagnostic scenarios. The purpose of this study was to evaluate the diagnostic accuracy of T2WI in detecting changes in meningioma tumor volume. METHODS: Imaging and clinical data were reviewed for 82 consecutive patients undergoing MR-surveillance of intracranial meningioma. Using volumetric-T2WI, two neuroradiologists independently calculated tumor volumes. Measurements were compared to a baseline study contrast-enhanced T1 tumor volume. Using contrast-enhanced sequences as the reference standard, statistical analysis was performed to determine the accuracy of T2WI in detecting changes of meningioma volume. RESULTS: Using only T2WI, readers detected meningioma volume change ≥ 20% in 19/82 patients and volume change <20% in 63/82 patients. Reader accuracy for detecting change in tumor volume on T2WI ≥ 20% was 0.85, sensitivity 0.65, specificity 0.93, positive predictive value (PPV) 0.79, and negative predictive value (NPV) 0.87. For meningiomas >1 ml, reader accuracy for detecting change in tumor volume on T2WI ≥20% was 0.90, sensitivity 0.78, specificity 0.95, PPV 0.88, and NPV 0.91. Change in tumor volume on T2WI ≥20% was detected with 100% accuracy for posterior fossa meningiomas. Inter-reader agreement for all meningiomas was moderate (κ = 0.45) improving to substantial agreement (κ = 0.77) with tumor volumes >1 ml. CONCLUSION: Volumetric-T2WI detects changes in meningioma volume with comparable accuracy to gold standard T1 postcontrast imaging, particularly with higher tumor volumes and posterior fossa locations.

Brain atrophy rates in patients with multiple sclerosis on long term natalizumab resembles healthy controls.

BACKGROUND: Clinically stable multiple sclerosis (MS) patients often have negligible inflammatory MRI changes. Brain atrophy may provide insight into subclinical disease progression. The objective was to compare brain atrophy rates in stable patients on long term natalizumab treatment vs. age and gender matched healthy non-MS controls (HC) prospectively over two-years examining brain volume, cognition, and patient reported outcomes (PROs). METHODS: MS patients treated with natalizumab for a minimum of 2 years, age 18-60 were recruited and compared with age- and gender-matched healthy controls (HC). Both groups were followed prospectively to obtain two years of consecutive magnetic resonance imaging, clinical and PRO data. Baseline normalized brain volume (NBV), yearly T2 lesion volume (T2LV), and percent brain volume change (PBVC) were measured using SIENAX, JIM 6.0, and SIENA respectively. Neuropsychological tests from the MACFIMS battery were selected to optimize assessments for impairments in the domains of information processing speed and memory. Patient reported outcomes (PROs) for domains of physical, mental and social quality of life were evaluated using the NeuroQol short forms. RESULTS: Forty-eight natalizumab and 62 HC completed all study visits. At baseline, unadjusted mean NBV (natalizumab=1508.80cm (Popescu et al., 2013) vs. HC=1539.23cm (Popescu et al., 2013); p=0.033) and median baseline T2LV (natalizumab=1724.62mm (Popescu et al., 2013) vs. HC=44.20mm (Popescu et al., 2013); p=<0.0001) were different. The mean PBVC at year 2, adjusted for gender and baseline age was -0.57% (CI: 0.7620, -0.3716) for natalizumab and -0.50% (-0.7208, -0.2831) for HC, but the difference between groups was not statistically significant (0.073%; p=0.62). Over the 2-year period, HC demonstrated mild improvements in some cognitive tests vs. natalizumab subjects. However, PROs were similar between the two groups. CONCLUSION: Stable MS patients on natalizumab have similar brain volume loss as people who do not have MS, suggesting normalization of brain atrophy.

Brain Atrophy Rates for Stable Multiple Sclerosis Patients on Long-Term Fingolimod versus Glatiramer Acetate.

Background: Clinically stable multiple sclerosis (MS) patients on long-term therapy often have negligible acute inflammation on MRI. Brain atrophy may provide insight into subclinical disease progression in such populations. Objective: This study aims to compare brain atrophy for age- and gender-matched MS patients treated for >2 years with fingolimod (FTY) or glatiramer acetate (GA), examining brain volume, cognition, and patient-reported outcomes (PROs). Methods: Stable relapsing-MS patients, age 18-60, on FTY or GA for >2 years were followed up for 2 years. MRI brain and lesion volumes, cognitive measures, and PROs were collected at baseline and annually. Results: Forty-four FTY and forty-three GA patients completed baseline and year 2 visits. No differences in age, gender, or education were observed. Median EDSS was 2.0GA and 2.5FTY (p = 0.22). Treatment duration was longer for GA, 6.50GA vs. 3.73FTY years (p < 0.001). Baseline geometric mean T2LV were different, GA = 1,009.29 cm3 vs. FTY = 2,404.67 cm3 (p = 0.0071). Baseline brain volumes were similar, GA = 1,508 cm3 vs. FTY = 1,489 cm3 (p = 0.2381). Annualized atrophy rates, adjusted for baseline and at mean baseline value, were GA = -0.2775% vs. FTY = -0.2967% (p = 0.7979). No differences in cognitive measures or PROs were observed. Conclusions: Stable MS patients on long-term treatment with FTY and GA have similar brain volume loss rates. Differences in baseline disease severity may suggest patients with more aggressive disease treated with FTY may achieve similar brain volume loss rates as patients with milder baseline disease on GA.

Underlying Mechanisms of Psychological Interventions in Magnetic Resonance Imaging and Image-Guided Radiology Procedures.

Positive patient care and healthcare facility outcomes are associated with using various psychological interventions during magnetic resonance imaging and interventional radiology procedures. Interventions such as hypnosis, relaxation, guided imagery, and empathic communication can improve anxiety, pain, and hemodynamic stability during procedures, as well as improve claustrophobia and anxiety during magnetic resonance imaging. Little is understood as to the potential underlying mechanisms of how these interventions operate and contribute to positive outcomes. Thus, this article seeks to address that question by integrating autonomic nervous system functioning, neuropsychological concepts, and common factors theory of psychotherapy as potential underlying mechanisms. Opportunities for future directions in the field are also included.

The use of intraoperative neurosurgical ultrasound for surgical navigation in low- and middle-income countries: the initial experience in Tanzania.

OBJECTIVE: Neuronavigation has become a crucial tool in the surgical management of CNS pathology in higher-income countries, but has yet to be implemented in most low- and middle-income countries (LMICs) due to cost constraints. In these resource-limited settings, neurosurgeons typically rely on their understanding of neuroanatomy and preoperative imaging to help guide them through a particular operation, making surgery more challenging for the surgeon and a higher risk for the patient. Alternatives to assist the surgeon improve the safety and efficacy of neurosurgery are important for the expansion of subspecialty neurosurgery in LMICs. A low-cost and efficacious alternative may be the use of intraoperative neurosurgical ultrasound. The authors analyze the preliminary results of the introduction of intraoperative ultrasound in an LMIC setting. METHODS: After a training program in intraoperative ultrasound including courses conducted in Dar es Salaam, Tanzania, and Aurora, Colorado, neurosurgeons at the Muhimbili Orthopaedic and Neurosurgical Institute began its independent use. The initial experience is reported from the first 24 prospective cases in which intraoperative ultrasound was used. When possible, ultrasound findings were recorded and compared with postoperative imaging findings in order to establish accuracy of intraoperative interpretation. RESULTS: Of 24 cases of intraoperative ultrasound that were reported, 29.2% were spine surgeries and 70.8% were cranial. The majority were tumor cases (95.8%). Lesions were identified through the dura mater in all 24 cases, with 20.8% requiring extension of craniotomy or laminectomy due to inadequate exposure. Postoperative imaging (typically CT) was only performed in 11 cases, but all 11 matched the findings on post-dural closure ultrasound. CONCLUSIONS: The use of intraoperative ultrasound, which is affordable and available locally, is changing neurosurgical care in Tanzania. Ultimately, expanding the use of intraoperative B-mode ultrasound in Tanzania and other LMICs may help improve neurosurgical care in these countries in an affordable manner.

Cervical Dystonia Is Associated With Aberrant Inhibitory Signaling Within the Thalamus.

Objective: The objective of this study is to investigate whether alterations in the neurotransmission of gamma-aminobutyric acid (GABA) in the thalamus are present in patients with cervical dystonia compared to healthy controls. Methods: GABA magnetic resonance spectroscopy was used to investigate concentration levels of GABA in the thalamus of cervical dystonia patients (n = 17) compared to healthy controls (n = 18). Additionally, a focused post hoc analysis of thalamic GABAA receptor availability data in a similar cohort (n = 15 for both groups) using data from a previously collected 11C-flumazenil positron emission tomography study was performed. Group comparisons for all evaluations were performed using two-sided t-tests with adjustments for age and sex, and Bonferroni correction for multiple comparisons was applied. Spearman's coefficient was used to test correlations. Results: We found significantly reduced GABA+/Cre levels in the thalamus of cervical dystonia patients compared to controls, and these levels positively correlated with disease duration. Although mean thalamic GABAA receptor availability did not differ between patients and controls, GABAA availability negatively correlated with both disease duration and dystonia severity. Conclusions: These findings support that aberrant inhibitory signaling within the thalamus contributes to the pathophysiology of cervical dystonia. Additionally, these results suggest that an inadequate ability to compensate for the loss of GABA through upregulation of GABAA receptors may underlie more severe symptoms.

First MRI With New Cochlear Implant With Rotatable Internal Magnet System and Proposal for Standardization of Reporting Magnet-Related Artifact Size.

OBJECTIVE: To report on the first known magnetic resonance imaging (MRI) with a new cochlear implant (CI) with rotatable internal magnet system, to review the literature on MRI in cochlear implantees, and to advocate for standardization of reporting magnet-related artifact size. STUDY DESIGN: Case report and review of literature. SETTING: Tertiary care hospital. RESULTS: A patient with congenital rubella and bilateral profound hearing loss was incidentally found to have a petroclival meningioma. After resection and radiosurgery, she underwent cochlear implantation with the Advanced Bionics HiRes Ultra 3D device (Advanced Bionics LLC, Valencia, CA) with rotatable internal magnet system, due to need for imaging surveillance of residual meningioma. During 1.5 T MRI brain scan without a head wrap, she experienced no adverse events. The images obtained were adequate for visualization of residual tumor. Implant recipients with non-rotatable magnets who undergo MRI, with or without recommended head wrap, may suffer various complications. All images in patients with retained internal magnets are subject to magnet-related artifact, but reports regarding its size are variable and lack detail on how measurements are made. CONCLUSIONS: MRI in patients with a new CI device with rotatable magnet system may be performed without discomfort or device dislodgement at 1.5 T, even without a head wrap, though external magnet replacement may require multiple attempts due to internal magnet realignment. Despite significant artifact, the structure of interest may still be visualized for accurate diagnosis. Measuring magnet-related artifact size should be standardized by reporting artifact in radii at the image level of maximal signal loss.

Subjective cognitive concern in multiple sclerosis is associated with reduced thalamic and cortical gray matter volumes.

OBJECTIVE: Brain atrophy has been correlated with objective cognitive dysfunction in multiple sclerosis but few studies have explored self-reported subjective cognitive concerns and their relationship to brain volume changes. This study explores the relationship between subjective cognitive concerns in multiple sclerosis and reduced brain volume in regions of interest implicated in cognitive dysfunction. METHODS: A total of 158 patients with multiple sclerosis completed the Quality of Life in Neurologic Disorders Measures (Neuro-QoL) short forms to assess subjective cognitive concerns and underwent brain magnetic resonance imaging. Regional brain volumes from regions of interest implicated in cognitive dysfunction were measured using NeuroQuant automated volumetric quantitation. Linear regression was used to analyze the relationship between subjective cognitive concerns and brain volume. RESULTS: Controlling for age, disease duration, gender, depression and fatigue, increased subjective cognitive concerns were associated with reduced thalamic volume (standardized ß = 0.223, t150 =2.406, P = 0.017) and reduced cortical gray matter volume (standardized ß = 0.240, t150 = 2.777, P = 0.006). Increased subjective cognitive concerns were not associated with any other regions of interest that were analyzed. CONCLUSIONS: Subjective cognitive concern in MS is associated with reduced thalamic and cortical gray matter volumes, areas of the brain that have been implicated in objective cognitive impairment. These findings may lend neuroanatomical significance to subjective cognitive concerns and patient-reported outcomes as measured by Neuro-QoL.

Rituximab vs placebo induction prior to glatiramer acetate monotherapy in multiple sclerosis.

OBJECTIVE: To examine whether rituximab induction followed by glatiramer acetate (GA) monotherapy is more effective than GA alone for the treatment of relapsing multiple sclerosis with active disease. METHODS: This was a single-center, double-blind, placebo-controlled study. Fifty-five participants were randomly assigned (1:1 ratio) to either rituximab (R-GA) or placebo (P-GA) induction, followed by GA therapy initiated in all participants. Participants were followed up to 3 years. The primary endpoint was the number of participants with no evidence of disease activity (NEDA): those without relapse, new MRI lesions, and sustained change in disability. RESULTS: Twenty-eight and 27 participants received rituximab and placebo induction, respectively, with one participant in each arm withdrawing before 6-month MRI. There were no significant differences in baseline characteristics. At end of study, 44.44% of R-GA participants demonstrated NEDA vs 19.23% of P-GA participants (p = 0.049). Treatment failed for a smaller proportion of R-GA participants (37.04% R-GA vs 69.23% P-GA, p = 0.019), and time to treatment failure was longer (23.32 months R-GA vs 11.29 months P-GA, p = 0.027). Fewer participants in the R-GA arm had new lesions (25.93% R-GA vs 61.54% P-GA, p = 0.009), and there were fewer new T2 lesions (0.48 R-GA vs 1.96 P-GA, p = 0.027). Probability of demonstrating NEDA in the R-GA arm returned to baseline within the study period. There were no differences in adverse events. CONCLUSIONS: Induction therapy with rituximab followed by GA may provide superior efficacy in the short term than GA alone in relapsing multiple sclerosis, but this benefit appears to wane within the study period. Larger studies are needed to assess sustainability of results. CLINICALTRIALSGOV IDENTIFIER: NCT01569451.

Multiple Sclerosis, Cannabis Use, and Clinical Disability: A Preliminary [18F]-Fluorodeoxyglucose Positron Emission Tomography Study.

Introduction: Long-term consequences of medicinal cannabis use in people with multiple sclerosis (PwMS) are unknown. This study investigated whether PwMS using cannabis had lower resting brain glucose uptake (GU) and worse clinical test results compared with nonusers. Methods: Sixteen PwMS, eight users, underwent clinical testing followed by [18F]-Fluorodeoxyglucose positron emission tomography/computed tomography imaging. Results: Users had lower cognitive function test scores, but performed similarly on the other clinical evaluations. Accounting for disease duration, resting brain GU was similar between the groups. Conclusions: Lower cognitive function was not associated with resting brain GU. Cognitive dysfunction may be a contraindication or consequence of cannabis use in PwMS.

Isolated focal dystonia phenotypes are associated with distinct patterns of altered microstructure.

Objective: Isolated adult-onset focal dystonia is considered a network disorder with disturbances to the motor basal ganglia and cerebellar circuits playing a pathophysiological role, but why specific body regions become affected remains unknown. We aimed to use diffusion tensor imaging to determine if the two most common phenotypes of focal dystonia are associated with distinguishing microstructural changes affecting the motor network. Methods: Fifteen blepharospasm patients, 20 cervical dystonia patients, and 30 age- and sex-matched healthy controls were recruited. Maps of fractional anisotropy and mean diffusivity were analyzed using a voxel-based approach and an automated region-of-interest technique to evaluate deep gray matter nuclei. Correlations between diffusion measures and dystonia severity were tested, and post hoc discriminant analyses were conducted. Results: Voxel-based analyses revealed significantly reduced fractional anisotropy in the right cerebellum and increased mean diffusivity in the left caudate of cervical dystonia patients compared to controls, as well as lower fractional anisotropy in the right cerebellum in cervical dystonia patients relative to blepharospasm patients. In addition to reduced fractional anisotropy in the bilateral caudate nucleus of cervical dystonia patients relative to controls and blepharospasm patients, region-of-interest analyses revealed significantly reduced fractional anisotropy in the right globus pallidus internus and left red nucleus of blepharospasm patients compared to both controls and cervical dystonia patients. Diffusivity measures in the red nucleus of blepharospasm patients correlated with disease severity. In a three-group discriminant analysis, participants were correctly classified with only modest reliability (67-75%), but in a two-group discriminant analysis, patients could be distinguished from each other with high reliability (83-100%). Conclusions: Different focal dystonia phenotypes are associated with distinct patterns of altered microstructure within constituent regions of basal ganglia and cerebellar circuits.

The impact of very short transition times on switching from Natalizumab to Fingolimod on imaging and clinical effectiveness outcomes in multiple sclerosis.

BACKGROUND: Due to the recurrence of disease activity in multiple sclerosis (MS) patients, a washout period of <3 months has been suggested for the transition from natalizumab (NTZ) to fingolimod (FTY). However, very short transition periods of <1 month may be more beneficial. METHODS: Retrospective analysis of patients from the Rocky Mountain MS Center at the University of Colorado who were: a) on NTZ for ≥6 months prior to switching to FTY; b) had a transition period ≤ 6 months; and c) initiated FTY treatment prior to November 2013. Transition periods were grouped as follows: <1 month, 1-2 months, and 3-6 months. Outcomes assessed include clinical and MRI measures within one year of FTY initiation. RESULTS: Thirty-seven, 56 and 24 patients had a transition period < 1 month, 1-2 months and 3-6 months, respectively. Baseline characteristics were well matched: mean age 45-49 years (p = 0.17), disease duration 11-13 years (p = 0.42), and ~70% women (p = 1.00). Following the switch (including transition period), clinical relapses were observed in 0% (<1 month), 12.5% (1-2 months), 37.5% (3-6 month) (p < 0.001) of patients. New gadolinium enhancing lesions occurred in 3.3% (<1 month), 13% (1-2 months), 21.4% (3-6 months) (p = 0.13) patients. New T2 lesions were observed in 11.1% (<1 month), 16.3% (1-2 months), 33.3% (3-6 months) (p = 0.28) of patients. There were no unexpected adverse events or PML observed. CONCLUSIONS: Minimizing transition times from NTZ to FTY was beneficial and safe.