Chow announced Friday she has been diagnosed with a "very very mild" form of Ramsay Hunt syndrome type 2, which occurs when a shingles infection affects the facial nerve near the ear.
Chow said she's pain-free and that the virus has been eradicated after an initial run of medication.
She said the only remaining impact of the syndrome is the paralysis of the left side of her face.
"I have absolutely no symptoms other than this very funny smile," Chow joked during an upbeat news conference.
Symptoms of Hunt syndrome can include vertigo, dizziness and changed or lost taste perception. It stems from the varicella zoster virus, which also causes chickenpox.
Chow said her doctor has informed her it could take weeks or months for the damaged nerves to grow back and the condition to clear.
Ramsay Hunt syndrome is relatively uncommon, affecting about five in every 100,000 people.
Dr. Allison McGeer, an infectious disease specialist at Mount Sinai Hospital in Toronto, said prompt treatment with antiviral drugs and steroids to reduce nerve-damaging swelling can help prevent facial paralysis from becoming permanent.
Chow said she was diagnosed over the holidays after waking up with some discomfort on her face.
"I think what happened was that I had a cough and then I took some antibiotics for six or seven days, and by the sixth or seventh day my immune system was quite low and that's when this thing kicked in," she said.
As a result, Chow said she is having trouble smiling, laughing and putting in her contact lens on the left side of her face.
But the widow of former NDP leader Jack Layton stressed the condition won't hinder her job in Parliament, noting that former Liberal prime minister Jean Chretien dealt with a permanent paralysis of the left side of his face from Bell's palsy.
"I don't need my facial expressions to do my work," Chow said before rattling off a list of issues she's pushing forward in the House of Commons.
"I want to get back to work immediately without having to explain many, many times about why I look slightly different."
Chow, a former Toronto councillor, said she is still reviewing her options on a possible bid for the city's top job, following a court ruling that ordered Mayor Rob Ford removed from office for violating conflict of interest rules.
Chow said the outcome of Ford's appeal next week of the expulsion ruling and whether council decides to hold a byelection — or appoint a new mayor — will guide her decision.
"I am seriously listening to people and when the time comes, if there is a decision (on a byelection), I will consider what role I might play," she said.
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