Ontario Court of Appeal quashes appeal in negligence case arising from brain aneurysm

In a medical malpractice action regarding a brain aneurysm, the Ontario Court of Appeal quashed an appeal against an order adding defendants upon determining that the appeal lay to the Divisional Court with leave because the order was interlocutory. 

In July and August 2013, the plaintiff in Zimmerman v. McNaull, 2026 ONCA 307, visited her family physician’s office and her local hospital’s emergency department multiple times with complaints of severe headaches and other symptoms. 

The plaintiff received various diagnoses, including musculoskeletal neck pain, vertigo, and migraines. On July 29, 2013, she had a computerized tomography (CT) scan, which the reviewing radiologist found unremarkable. 

A second CT scan on Aug. 3, 2015 revealed a subarachnoid hemorrhage due to a burst aneurysm. Despite having surgery on Aug. 4, 2015, she kept experiencing short-term memory issues, confusion, headaches, fatigue, depression, and gait instability. 

Through a statement of claim dated Aug. 21, 2015, the plaintiff alleged that the defendants who assessed or treated her from July to August 2013 failed to meet the required standard of care and caused her injuries due to their negligence. The action sought damages of $5 million. 

The plaintiff then moved for leave to add physicians as defendants to the medical malpractice action. The proposed defendants sought specific information to challenge her assertion about when she discovered or should have discovered the possible claim against them. 

On May 11, 2021, the Ontario Superior Court of Justice found much of the requested documentation irrelevant to the leave motion’s issues. 

However, given the implied partial or total waiver of the litigation privilege over some of the relevant and material documents, the Superior Court directed their disclosure to the proposed defendants. 

On Aug. 6, 2025, the motion judge allowed the plaintiff to amend the statement of claim and add new defendants based on their involvement with her care in December 2009 and March 2010. The judge awarded her costs. 

The judge determined that the plaintiff discovered the claim on June 20, 2018, and could not have done so earlier. The judge added that she had established that the limitation period to add the new defendants had not expired. 

Before the Ontario Court of Appeal, the newly added defendants appealed the Aug. 6, 2025 order. They argued that the claim was discoverable against them in April 2018. 

The plaintiff moved to quash the appeal. She asserted that the appeal lay to the Divisional Court, with leave, under s. 19(1)(b) of Ontario’s Courts of Justice Act, 1990, as the appealed order was interlocutory. 

The new defendants countered that the order subject to appeal was final because the judge had finally determined and thus precluded their substantive limitation period defence. 

Appeal quashed

Last May 1, the Court of Appeal for Ontario transferred the proceeding to the Divisional Court to enable the new defendants to move for leave to appeal. The appeal court ordered the new defendants to pay the plaintiff all-inclusive costs of $7,500. 

The appeal court ruled that the motion judge had not finally determined the limitation period issue or precluded the defence. The appeal court explained that the judge had made preliminary factual findings only to determine the plaintiff’s amendment motion. 

The appeal court pointed out that the judge had not acceded to the plaintiff’s attempt to preclude the new defendants from relying on a limitation period defence. 

The appeal court acknowledged that it would have been clearer if the judge had made the following express statements, which would have avoided uncertainty and additional costs: 

• He was ruling on the limitation period issue only to resolve the amendment motion 
• He was denying the plaintiff’s request to finally determine the limitation period 
• The new defendants could still rely on that defence 

However, the appeal court reiterated that the order under appeal did not preclude the new defendants from asserting a limitation period defence.