Multiple sclerosis (MS) symptoms worsen if you become overheated. When elevated body temperature impairs vision or other MS symptoms, it’s called Uhthoff’s phenomenon.
Uhthoff’s occurs because of previous damage to myelinated nerves due to MS. It interferes with the transmission of nerve signals to the brain. Symptoms include blurry or reduced vision.
Uhthoff’s phenomenon is sometimes called “Uhthoff’s syndrome” or “Uhthoff’s sign.” The condition was named for Wilhelm Uhthoff, a German professor of ophthalmology who lived from 1853 to 1927.
Read on to learn more about Uhthoff’s phenomenon, what to do when it occurs, and more.
A 2018 study reported that between 60% and 80% of people with MS experience heat sensitivity.
Demyelinated fibers in the CNS are hypersensitive to a rise in body temperature. This makes it more difficult for the body to receive internal signals. This can result in a worsening of MS-related symptoms and cause blurred vision.
Heat sensitivity and the related worsening of MS symptoms are usually temporary. This is called pseudo-exacerbation. It doesn’t mean new lesions, lasting neurological damage, or a more rapid progression of MS.
MS-related heat sensitivity doesn’t cause new symptoms, but it can aggravate existing symptoms. Besides vision problems, these can include:
- fatigue
- numbness
- weakness
- bladder problems
Learn about how MS affects the body.
Uhthoff’s phenomenon is temporary and usually lasts
If your vision is seriously impaired, ask someone to help you find a safe place to rest and cool off.
Other tips include:
- cooling your body temperature
- finding a shady area outdoors or an air-conditioned room indoors
- keeping hydrated with cool water
- taking a cool bath or shower
- applying a cool compress to your neck, wrists, and feet
- eating cold foods rather than hot foods
Medical intervention isn’t usually necessary for symptoms of Uhthoff’s phenomenon. However, you should seek medical advice if:
- you’ve never experienced heat-related symptoms of MS before
- you’re uncertain that your symptoms are Uhthoff’s or MS-related
- you have accompanying symptoms unrelated to MS
- your symptoms don’t improve after you’ve cooled down
Avoiding overheating can help to prevent Uhthoff’s phenomenon
When indoors, use an air conditioner or fan during times of extreme heat and humidity. This is especially helpful when exercising.
Avoid hot showers, baths, and saunas. Avoiding vigorous exercise in hot weather can also help.
When outdoors, you can:
- try to stay in the shade and avoid intense exercise
- use cooling products such as cooling vests, neck wraps, and portable fans
- drink icy beverages
- avoid hot tubs and swimming pools heated above 85ºF (29ºC)
While heat and humidity can trigger a wide range of MS-related symptoms, so can cold weather. Cold temperatures can trigger involuntary muscle spasms or stiffness, called spasticity.
If you have heat- or cold-related symptoms of MS, it’s best to avoid exposure to any extreme temperature, if you can. If you’re thinking of relocating for health reasons, you may want to spend some time in a different climate first to see if it makes a difference for you.
Uhthoff’s phenomenon can happen in people with multiple sclerosis (MS) as a result of overheating. It can worsen existing symptoms and affect vision.
Uhthoff’s phenomenon is usually temporary and does not require specific treatment. However, cooling your body temperature, drinking cool drinks, and taking a cool shower may help.
Contact a doctor if you think you are experiencing Uhthoff’s phenomenon for the first time. You should also seek medical advice if symptoms do not improve after cooling down or if you’re unsure whether you’re experiencing Uhthoff’s phenomenon.