From the DOL website FAQ for FMLA:
"Q. Can I continue to use FMLA for leave due to my chronic serious health condition?
A. Under the regulations, employees continue to be able to use FMLA leave for any period of incapacity or treatment due to a chronic serious health condition. The regulations continue to define a chronic serious health condition as one that (1) requires “periodic visits” for treatment by a health care provider or nurse under the supervision of the health care provider, (2) continues over an extended period of time, and (3) may cause episodic rather than continuing periods of incapacity. The regulations clarify this definition by defining “periodic visits” as at least twice a year.
Q. Are there any changes to the definition of a serious health condition under the regulations?
A. A “serious health condition” is defined as an illness, injury, impairment, or physical or mental condition that involves inpatient care or continuing treatment by a health care provider. The “continuing treatment” test for a serious health condition under the regulations may be met through (1) a period of incapacity of more than three consecutive, full calendar days plus treatment by a health care provider twice, or once with a continuing regimen of treatment, (2) any period of incapacity related to pregnancy or for prenatal care, (3) any period of incapacity or treatment for a chronic serious health condition, (4) a period of incapacity for permanent or long-term conditions for which treatment may not be effective, or (5) any period of incapacity to receive multiple treatments (including recovery from those treatments) for restorative surgery, or for a condition which would likely result in an incapacity of more than three consecutive, full calendar days absent medical treatment.
The regulations specify that if an employee asserts a serious health condition under the requirement of a “period of incapacity of more than three consecutive, full calendar days and any subsequent treatment or period of incapacity relating to the same condition,” the employee’s first treatment visit (or only visit, if coupled with a regimen of continuing treatment) must take place within seven days of the first day of incapacity. Additionally, if an employee asserts that the condition involves “treatment two or more times,” the two visits to a health care provider must occur within 30 days of the first day of incapacity. Finally, the regulations define “periodic visits” for treatment of a chronic serious health condition as at least twice a year."
Without knowing all the details, seems like a stroke could meet the requirement of chronic serious health condition. You should definitely seek the advice of an actual lawyer rather than the assumptions of anyone on this forum.