ET is associated with action tremor of the upper extremities that can complicate activities of daily life. Neurosurgical intervention can improve tremor in cases where patients are refractory to first-line pharmacological treatments. Thalamic ablation using MRgFUS is among the surgical approaches most rapidly being embraced to address medication-refractory tremor. ^{Reference Iorio-Morin, Hodaie and Lozano1} Briefly, targeted ultrasound energy guided by real-time imaging and thermometry is used to heat and ablate the ventral intermedius nucleus of the thalamus, disrupting tremor signaling. MRgFUS thalamotomy provides significant tremor abatement and an associated improvement in quality of life. ^{Reference Elias, Lipsman and Ondo2} The procedure was granted Health Canada approval in 2016, ³ and in 2018, became publicly funded in Ontario, home to 38.5% of Canada’s population. ⁴

Given the recentness of provincial funding committed for MRgFUS thalamotomy, along with the reported variability in accessing complex care across Ontario, ^{Reference Ge, Jaffe, Tsoh and Varma5} awareness and accessibility to this neuromodulatory procedure may vary across the province. Geographic and socioeconomic differences in patient access to MRgFUS thalamotomy have yet to be investigated in Ontario. To explore these factors, we reviewed the demographics of referrals submitted to Sunnybrook Health Sciences Centre, one of two institutions routinely performing MRgFUS thalamotomies for ET in the province. Historically, referrals to specialists have been influenced by factors, including financial status, ^{Reference Chan and Austin6} community size ^{Reference Chan and Austin6} and medical specialty. ^{Reference Liddy, Arbab-Tafti, Moroz and Keely7} Here, we benchmarked the patients and referring medical specialties across Ontario who were interested in our program between 2018 and 2023, and used jurisdictional data to identify socioeconomic variables associated with referral patterns for MRgFUS thalamotomy for ET.

Since the inception of the MRgFUS program, Sunnybrook has undertaken several outreach and public awareness initiatives to promote availability of the procedure, including advertisements in local public transit, radio, national newspapers, clinic spaces and online platforms. Referrals received for the program were grouped by fiscal year (FY), which begins on April 1 and ends on March 31 of the following year. Those with missing data or from locations outside of Ontario were excluded. The first three characters of the patient’s postal code, known as the forward sortation area (FSA), were extracted from referral demographics. The FSA indicates the provincial region and rurality status of the address. FSAs beginning with the letters K, L, M, N and P denote Eastern Ontario, Central Ontario, Metropolitan Toronto, Southwestern Ontario and Northern Ontario, respectively (Figure 1). The second character of the FSA denotes the jurisdiction as a rural (0) or urban (1–9) setting. Pearson correlations were used to investigate relations between referral frequency and measures of socioeconomics by FSA. In particular, population size, mean total income for the 2021 tax year and highest level of education for adults aged between 25 and 64 years were sourced from publicly available data from the most recent Canadian census in 2021. ⁴ Euclidean distance to the hospital was calculated by comparing the FSA of the referral to the postal code of Sunnybrook using the ZipCodeBase zip code distance API (zipcodebase.com).

Figure 1. Referrals by population. FSAs in Ontario begin with either K, L, M, N or P (map). Referral incidence was calculated using the population of each region as per the 2021 Canadian census. FSA = forward sortation area.

Between FY2018–2019 and FY2022–2023, the MRgFUS program received a total of 890 referrals, including 794 from 303 of the FSAs across Ontario. Seventy-eight Ontario-based referrals were received in FY2018–2019, and 182 in FY2019–2020 (Figure 2). This upward trend was disrupted by a decline to 95 referrals in FY2020–2021, likely attributable to the COVID-19 pandemic. The number of referrals rebounded, with 163 in FY2021–2022 and 276 in FY2022–2023. Notably, while neurologists accounted for approximately half of the total referrals (n = 395), family physicians contributed closely with 46.3% (n = 368) (Figure 3). The remaining 3.9% of referrals (n = 31) came from other specialties, including nurse practitioners (n = 13), neurosurgeons (n = 7), internal medicine (n = 7), anesthesiology (n = 1), endocrinology (n = 1), plastic surgery (n = 1) and orthopedic surgery (n = 1). Neurologists submitted more referrals than other specialties in FY2018–2019 (n = 47; 60.2%), FY2020–2021 (n = 57; 60.0%) and FY2021–2022 (n = 87; 53%). In contrast, family physicians had a higher referral count in FY2019–2020 (n = 91; 50%) and FY2022–2023 (n = 146; 52.9%).

Figure 2. Regional referral frequency. Choropleth maps of Ontario with borders defining FSAs. No referrals were received from regions shaded in gray. (A) shows frequency of referrals received across all FYs, ranging from 1 per FSA (pale yellow) to 16 (red). (B–F) show frequency of referrals received in individual FY, ranging from 1 per FSA (pale yellow) to 7 (dark green). FSAs in the Toronto region are enlarged in inset circles. Choropleth maps were generated using the Datawrapper choropleth mapping tool (Datawrapper GmbH, Berlin). FSA = forward sortation area; FY = fiscal year.

Figure 3. Referrals by medical specialty. Pie charts depict the relative distribution of referrals by specialty across all regions (A), and in urban (B) and rural (C) settings. Medical specialty/accreditation of referring clinicians was obtained either from the CPSO website or the CNO website. CPSO = College of Physicians and Surgeons of Ontario; CNO = College of Nurses of Ontario.

Rural Ontario submitted 6.7 referrals per 100,000 individuals between FY2018–2019 and FY2022–2023, while urban regions submitted 5.4 per 100,000. In rural settings, neurologists submitted 48.8% (n = 63) of referrals, and family physicians submitted 45.0% (n = 58). In urban settings, neurologists and family physicians were responsible for 49.9% (n = 332) and 46.6% (n = 310) of referrals, respectively. Regionally, Metropolitan Toronto submitted referrals most frequently at a rate of 8.2 referrals per 100,000 individuals (Figure 1), and Northern Ontario followed closely at rate of 6.7 referrals per 100,000 individuals. Southwestern Ontario exhibited the lowest referral rate, submitting only 2.7 referrals per 100,000 individuals. There was no significant relationship between referral rate and the absolute distance to Sunnybrook (R = −0.19). There was a weak correlation between the number of referrals received per FSA and FSA income (R = 0.32). Referral rate showed no significant correlation with the percentage of the population with no high school diploma (R = −0.14), holding a bachelor’s degree or higher (R = −0.10) or holding an apprenticeship certificate (R = 0.15).

MRgFUS thalamotomy is a novel, publicly funded surgical modality for refractory ET. Referral rates to our program at Sunnybrook have risen over time despite some slowing during the pandemic. The overall increase in referrals highlights the growing popularity of MRgFUS, a trend underscored by its minimal invasiveness, capability for real-time assessments and effective marketing. ^{Reference Elias, Lipsman and Ondo2} Over the course of the study period, 213 cases of MRgFUS thalamotomy were publicly funded at our center. The typical interval between referral and treatment was 6 to 12 months, depending on case complexity and scheduling capacity. Family physicians contributed nearly half of the referrals, suggesting a firm interest in MRgFUS thalamotomy among primary care clinicians province-wide. Increased awareness among family physicians creates an opportunity for accelerated access to our multidisciplinary program, wherein a pre-procedural neurology consultation to ascertain diagnosis and eligibility is included. Typically, a diagnosis of ET is confirmed, and patients do well following treatment, expressing a high degree of satisfaction. ^{Reference Rabin, Gopinath and McSweeney8} Infrequently, patients are diagnosed with alternative causes of tremulousness, including functional neurological disorders, Parkinson’s disease, dystonia or ALS, and are managed accordingly.

Access to our program is not limited by distance. While the highest referral rate was detected in Metropolitan Toronto (the region home to Sunnybrook), Northern Ontario’s referral rate followed closely behind. These findings align with the observation that Ontarians living large distances from care centers appear highly willing to travel for specialist care. ^{Reference Sapru, Cassidy and Sibbald9} Indeed, MRgFUS thalamotomy requires only a few visits to Sunnybrook, and long-term follow-up is managed through a combination of local and virtual care. The popularity of MRgFUS in Northern Ontario may likewise be supported by effective knowledge translation and provincial reimbursement for long-distance travel and lodging. Given the lower density of referring physicians in northern regions, a founder effect, whereby a few physicians refer most of the patients, may also be at play. Notably, patterns of referral did not differ greatly across rural and urban settings.

On a whole, no glaring socioeconomic disparities were associated with referral patterns. The modest relationship between referral rate and income in our study is consistent with the finding that patients with higher income in Ontario are slightly more likely to be referred to a specialist. ^{Reference Ge, Jaffe, Tsoh and Varma5} Individuals from higher-income families might have greater flexibility and financial resources for transportation and lodging, facilitating travel to distant care centers. By extension, regions with higher household incomes, typically found in more populous areas such as Metropolitan Toronto, may naturally generate higher referral volumes. Regional rates of referral do not appear to be substantially influenced by patients’ level of education.

Our findings, while informative, are constrained by the retrospective nature of the analysis. This design did not permit collection of self-identified race and gender data, and consequently, we were unable to assess whether demographic factors may have contributed to observed referral patterns. Incorporating self-reported demographic data in future prospective studies will be critical to understanding and addressing any potential disparities in access. In addition, the analysis relied on referral data collected in only one of two MRgFUS centers in Ontario. This may result in limited generalizability of referral counts and geographic inferences. A lower referral rate was seen in Southwestern Ontario, which may be related to a referral bias to the second provincial MRgFUS center or due to a potentially larger proportion of ET patients treated with other surgical modalities in this region. Indeed, Southwestern Ontario has a well-established Deep Brain Stimulation network for movement disorders. ^{Reference Crispo, Lam and Le10} Future research should aim to include data from multiple institutions and incorporate additional socioeconomic and healthcare system variables.

Mapping accessibility to publicly funded neuromodulatory procedures informs the decision-making process for health authorities, administrators and policymakers who monitor the use of medical services across the province. Here, we provide a preliminary overview of regional and socioeconomic variations in referral patterns for MRgFUS thalamotomy to manage ET in Ontario. Enhancing awareness through targeted outreach and optimizing referral pathways will be useful to address potential disparities and support equitable access to this innovative treatment across all regions of Ontario.