The Dead to Me star has experienced numbness and tingling in her extremities – hallmarks of the neurological condition – insomnia and she is unable to move around without a walking stick, an aid she previously said is "now part of my new normal".
WATCH: Christina Applegate stars in hit Netflix show Dead to Me
While Christina has support from her family during her difficult health battle, one person who has really been there for her is her close friend Selma Blair, who revealed her own MS diagnosis in 2018.
In fact, Selma – who starred with Christina in 2002's The Sweetest Thing – admitted that they are both a strong support system for each other.
"Christina still supports me. She's just a strong one. She really is. She's such a nurturer," Selma told Entertainment Tonight. "If you need something she's at your house. There have been things that I had been unglued, and she's like, 'I'm outside. Answer the door.' She's just amazing and strong and fun."
Christina and Selma are both battling MS
Selma added: "But I'm more like, 'OK, if you need help with canes,' and that stuff, 'cause I'm like, really into all of that, like all the things that help me get around, but she's getting it locked down.
"She has a lot on her plate. It's a lot, but she's as brilliant and beautiful as ever."
Before Christina was diagnosed with MS, she admitted that she began experiencing symptoms years before – such as numbness and a tingling sensation in her limbs – but was unaware of the connection to the disease.
"I wish I had paid attention," she said during an interview with the New York Times. "But who was I to know?"
Christina needs a walking stick to move around
Once diagnosed, Christina admitted: "There was the sense of, 'Well, let's get her some medicine so she can get better.' And there is no better. But it was good for me. I needed to process the loss of my life, my loss of that part of me."
Christina also revealed that she has gained 40lbs over the last 18 months due to her declined mobility but admitted that her change in appearance is not lost on her. "This is the first time anyone's going to see me the way I am. I put on 40 pounds," she said ahead of Dead to Me's final season.
"I can't walk without a cane. I want people to know that I am very aware of all of that," she added. The actress has also shared how her MS symptoms have left her struggling to sleep, noting on Twitter in May: "MS is weird that way."
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