Multiple Sclerosis(MS) Symptoms- Uhthoff Phenomenon

Also known as heat intolerance

It is a transient worsening of neurological function lasting less than 24 hours that can occur in multiple sclerosis patients due to increases in core body temperature. Knowledge of this phenomenon and its pathophysiology, therefore, is essential for recognition and appropriate treatment.

This phenomenon is named after Wilhelm Uhthoff, a German ophthalmologist who described it. In 1890, Uhthoff first described exercise-induced amblyopia in multiple sclerosis patients.

Between 60%-80% of patients living with MS exhibit Uhthoff’s phenomenon with heat exposure. It is usually applied to optic neuritis and other visual symptoms but can also refer to fatigue, pain, balance, weakness, bladder issues, cognitive or sensory symptoms.

Uhthoff’s phenomenon is most observed in multiple sclerosis but may occur in other optic neuropathies or disorders of afferent pathways for example neuromyelitis Optica. In multiple sclerosis, several factors including the blockade of ion channels, heat shock proteins, circulatory changes, effects of serum calcium, and unidentified humoral substance have been hypothesized and investigated as a cause of Uhthoff’s phenomenon. Temperature-sensitive conduction blockade of partially demyelinated axons in the demyelinated plaques is the most widely accepted mechanism. Several other factors including perimenstrual period, exercise, fever, sun-tanning, hot shower, sauna, psychological stress, and even hot meal and smoking of cigarettes have been reported in the literature as triggers for Uhthoff’s phenomenon.

The precise mechanisms of Uhthoff’s phenomenon are not completely understood but are likely due to a combination of structural and physiological changes within the demyelinated axons in the central nervous system (CNS) in the setting of the elevated core body temperature.

Events preceding the worsening of neurological symptoms should be analyzed during history taking. Factors including exercise, taking a hot bath or shower, exposure to the sun, menstrual cycle, psychological stress, hot meals, fever, and infection should be addressed as any of these can precipitate worsening of the symptoms in MS patients. The transient worsening of the symptoms induced by such factors is termed 'pseudo exacerbation' or 'pseudo-relapse' as opposed to a true relapse or exacerbation in MS patients. This worsening typically should last less than 24 hours. Relapse or exacerbation is the hallmark of relapsing MS and is characterized by new focal neurological deficits lasting for at least 24 hours in the absence of fever or infection. Often, a detailed history can differentiate a true relapse from a pseudo-relapse.

Episodes of Uhthoff's phenomenon is generally considered to be the result of established demyelinating plaques in the setting of thermal stress. The key to making a diagnosis is detailed history from the patient regarding the circumstances in which the symptoms appeared. In patients with pseudo-relapse, care should be taken to rule out common precipitating factors like urinary tract infection, upper respiratory tract infection, or metabolic abnormalities through laboratory tests. Thus, the workup should include a detailed history and physical examination in addition to laboratory investigations to rule out metabolic, toxic, and infectious disorders. An MRI brain MRI C-spine, MRI T-spine with and without contrast to assess for any new contrast-enhancing lesions that could reveal a new clinical attack for the demyelinating condition the patient suffers. For new diagnosis, a lumbar puncture may be indicated to pinpoint the demyelinating or inflammatory condition including basic CSF studies, meningoencephalitis panel, oligoclonal bands, IgG Index, NMO Aquaporin-4 or MOG antibodies, among others.

It is crucial in the prevention and treatment of Uhthoff's phenomena to be familiar with the triggers that can result in elevation of core body temperature, and their corresponding impact on the patient's neurological functioning and safety. Patients should be counseled about the stimulating effects of taking hot showers?or baths regarding reducing appendicular and core muscle strength leading to profound weakness and thereby placing them in grave danger of drowning. Also, they should be cautioned against sauna, exposure to the sun when the outside temperature is greater than 30C, hydrotherapy with water at high temperatures, short-wave radiotherapy, and paraffin application. Patients should be advised about performing an exercise during early morning and late evening hours when the temperature is cooler.

Uhthoff phenomenon fully resolves following variable periods of rest (generally ranging from minutes to an hour), and under circumstances where heat stressors are removed, or active cooling measures are applied. Simple and convenient strategies such as taking cold showers, application of ice packs, use of regional cooling devices, and cold beverages can also be tried for heat sensitivity. Cooling garments have been shown to improve neurological function (motor performance and visual acuity) and perceived subjective benefits (feeling less fatigued) in MS patients with Uhthoff's phenomenon.

The prognosis of this phenomenon is good if pseudo exacerbation triggers are avoided. Treating the underlying neuroimmunological disorder is instrumental to avoid recurrence.

Education and reassurance about the symptoms and the underlying etiology should be provided to patients. This includes avoiding triggers such as hot baths or exposure to excessive heat. Education about what new and old symptoms can be related to a demyelinating disease such as multiple sclerosis can empower patients to report them to the physician for further workup, including the presence of possible new lesions or exacerbation. This could alert physicians of loss of effectiveness of the patient's current treatment and progression.

Takeaways:?

1) The exact science of Uhthoff’s phenomenon is not yet understood. However, some studies have shown that even a slight increase in core body temperature can slow or block the conduction of nerve impulses in demyelinated nerves. In simple?terms, this means your body has a difficult time sending and receiving internal signals.

2) Uhthoff’s phenomenon is temporary. Once the body’s core temperature returns to normal, symptom flares subside.

3) Uhthoff’s phenomenon does not signal you have new lesions, lasting neurological damage, or a rapid progression of MS.

4) Uhthoff’s phenomenon is not the same as a relapse or exacerbation. In fact, it is considered a pseudo-exacerbation.

5) Not everyone with MS is heat sensitive. Some people do not experience Uhthoff’s phenomenon when their core body temperature rises.

6) For those who are heat sensitive, any source of heat can trigger Uhthoff’s phenomenon. Some examples are hot and humid weather, a blow dryer, fever, a sauna, hot (or even warm) baths and showers, and hormonal changes.

7) Prevention is the key to avoiding Uhthoff’s phenomenon. Stay away from triggers and prepare for instances when you know you’ll be exposed to heat. Equip yourself with cold packs, cooling accessories, cold water and other hydration drinks, misting bottles, and portable fans. Loose, cotton clothing is best for good ventilation.

8) Individuals who are susceptible to Uhthoff’s phenomenon do not need to avoid exercise. Studies show exercise can be helpful in managing MS symptoms, reducing the risk of comorbidities, and promoting overall wellness. They should, however, take necessary precautions such as exercising in a cool environment and wearing cooling accessories.

9) Consider pre-cooling the body before exercise. In one study, heat-sensitive individuals with MS immersed their lower bodies in 62-degree Fahrenheit water for 30 minutes before exercising. They reported exercising in greater comfort and with fewer side effects than usual.

10) Hydrotherapy is another exercise option for heat-sensitive individuals. The recommended water temperature is a moderately cool 80 to 84 degrees F (~26-28 degree Celsius. Temperatures lower than 80 degrees F (~26 degree Celsius) are not recommended because of the risk of triggering spasticity.

11) If, despite your best efforts to prevent overheating, you believe you’re experiencing Uhthoff’s phenomenon, the best remedy is to cool down as quickly as possible.

12) In general, medical intervention isn’t necessary for Uhthoff’s phenomenon, as symptoms will subside after your core body temperature returns to normal. Recovery is not always immediate and can take several hours or more to fully resolve.

13) You may want to seek medical attention 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

To be continued ……?

References:?

https://www.ncbi.nlm.nih.gov/books/NBK470244/#:~:text=and%20Other%20Issues-,Uhthoff's%20phenomenon%20(also%20known%20as%20Uhthoff%20sign%20or%20Uhthoff%20syndrome,%2C%20saunas%2C%20or%20hot%20tubs.

https://mstrust.org.uk/a-z/uhthoffs-phenomenon?

https://msfocusmagazine.org/Magazine/Magazine-Items/Understanding-and-avoiding-Uhthoff%E2%80%99s-phenomenon?