Uhthoff's phenomenon

Uhthoff's phenomenon
Uhthoff's phenomenon
Other names	Uhthoff's syndrome, Uhthoff's sign, Uhthoff's symptom
Specialty	Neurology
Symptoms	fatigue, pain, urinary urgency, worse optic neuritis
Causes	high body temperature, causes longer inactivation of voltage-gated sodium channels
Diagnostic method	based on symptoms
Differential diagnosis	degeneration of condition of multiple sclerosis
Prevention	keeping cool, use of cool clothing
Treatment	cool clothing
Medication	none
Prognosis	typically completely reversible
Frequency	60-80% of people with multiple sclerosis
Deaths	0

Uhthoff's phenomenon (also known as Uhthoff's syndrome,^[1] Uhthoff's sign,^[1] and Uhthoff's symptom) is the worsening of neurologic symptoms in multiple sclerosis (MS) and other demyelinating diseases when the body is overheated. This may occur due to hot weather, exercise, fever, saunas, hot tubs, hot baths, and hot food and drink. Increased temperature slows nerve conduction, but the exact mechanism remains unknown. With an increased body temperature, nerve impulses are either blocked or slowed in a damaged nerve. Once the body temperature is normalized, signs and symptoms typically reverse.^{[citation needed]}

Signs and symptoms

Symptoms of Uhthoff's phenomenon occur when exposed to heat, and include:

fatigue^[2]
pain^[2]
concentration difficulties^[2]
urinary urgency^[2]^[3]
worsen of existing optic neuropathy^[4] (although optic neuropathy may occur for the first time)^[3]
muscle stiffness^[3]
dizziness and unsteadiness^[3]

Causes

Uhthoff's phenomenon is caused by a raised body temperature.^[1] This may be caused by:

hot weather^[3]
exercise^[1]^[5]
fever^[1]
saunas^[1]
sun tanning^[1]
hot tubs, and hot baths and showers^[1]^[5]
hot food and drink^[1]^[5]
menstruation (which may raise body temperature)^[1]
sitting near a radiator^[3]

Mechanism

The exact mechanism of Uhthoff's phenomenon is unknown. It causes a decrease in the speed of action potentials in the central nervous system (CNS).^[1]^[6] Heat may increase the time when voltage-gated sodium channels are inactivated, which delays further action potentials.^[6]^[7] This is worsened by the demyelination caused by MS.^[7] Other theories have considered the role of heat shock proteins and changes to blood flow.^[1]

Peripheral nerve studies have shown that even a 0.5 °C increase in body temperature can slow or block the conduction of nerve impulses in demyelinated nerves. With greater levels of demyelination, a smaller increase in temperature is needed to slow down the nerve impulse conduction.^[8] Exercising and normal daily activities can cause a significant increase in body temperature in individuals with MS, especially if their mechanical efficiency is poor due to the use of mobility aids, ataxia, weakness, and spasticity.^[9] However, exercise has been shown to be helpful in managing MS symptoms, reducing the risk of comorbidities, and promoting overall wellness.^[10]

Diagnosis

Diagnosis of Uhthoff's phenomenon is clinical and based on symptoms when it occurs in a person who is already diagnosed with MS.^[1] The main differential diagnosis is a more serious worsening of MS symptoms.^[1]

Prevention and management

Many patients with MS tend to avoid saunas, warm baths, and other sources of heat. They may wear ice or evaporative cooling clothes, such as vests, neck wraps, armbands, wristbands, and hats. Taking advantage of the cooling properties of water may help attenuate the consequences of heat sensitivity. Exercise pre-cooling via lower body immersion in water of 16–17 °C for 30 minutes may allow heat sensitive individuals with MS to exercise more comfortably with fewer side effects by minimizing body temperature increases during exercise.^[9] Hydrotherapy exercise in moderately cool water of 27–29 °C water can also be advantageous to individuals with MS. Temperatures lower than 27 °C are not recommended because of the increased risk of invoking spasticity.^[10]

Prognosis

Uhthoff's phenomenon is a temporary problem, and typically completely reverses once body temperature returns to normal.^[2]^[8] This may take up to 24 hours.^[1]

Epidemiology

Uhthoff's phenomenon may affect any person with a demyelinating disease.^[1] This is most commonly MS, but it may also occur with neuromyelitis optica spectrum disorder^[1]^[3] or Guillain-Barré Syndrome. It affects between 60% and 80% of people with MS.^[1]^[3]

History

Uhthoff's phenomenon was first described by Wilhelm Uhthoff in 1890 as a temporary worsening of vision with exercise in patients with optic neuritis.^[1]^[11] Later research revealed the link between neurological signs such as visual loss and increased heat production and Uhthoff's belief that exercise was the etiology of visual loss was replaced by the conclusions of these later researchers stating that heat was the prime etiology.^[12]

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s Panginikkod, Sreelakshmi; Rayi, Appaji; Cabrero, Franklyn Rocha; Rukmangadachar, Lokesh A. (January 2021). "Uhthoff phenomenon". StatPearls. PMID 29261916 – via PubMed.
^ ^a ^b ^c ^d ^e Flensner, G.; Ek, A.C.; Soderhamn, O.; Landtblom, A.M. (2011). "Sensitivity to heat in MS patients: a factor strongly influencing symptomology-an explorative survey". BMC Neurol. 11: 27. doi:10.1186/1471-2377-11-27. PMC 3056752. PMID 21352533.
^ ^a ^b ^c ^d ^e ^f ^g ^h Park, Kwiyoung; Tanaka, Keiko; Tanaka, Masami (2014). "Uhthoff's Phenomenon in Multiple Sclerosis and Neuromyelitis Optica". European Neurology. 72 (3–4): 153–156. doi:10.1159/000361045. ISSN 0014-3022. PMID 25195501. S2CID 46704524 – via Karger Publishers.
^ Thurtell, M. J. (2014). "Visual Loss, Transient". Encyclopedia of the Neurological Sciences (2nd ed.). Academic Press. pp. 698–703. doi:10.1016/B978-0-12-385157-4.00168-8. ISBN 978-0-12-385158-1.
^ ^a ^b ^c Khanh Vu, T.H.; Zhu, R.; Yang, L.; Chen, D. F. (2014). "Optic Nerve Structure and Pathologies". Pathobiology of Human Disease - A Dynamic Encyclopedia of Disease Mechanisms. Academic Press. pp. 2115–2125. doi:10.1016/B978-0-12-386456-7.04707-9. ISBN 978-0-12-386457-4.
^ ^a ^b Davis SL, Frohman TC, Crandall CG, et al. (March 2008). "Modeling Uhthoff's phenomenon in MS patients with internuclear ophthalmoparesis". Neurology. 70 (13 Pt 2): 1098–106. doi:10.1212/01.wnl.0000291009.69226.4d. PMID 18287569. S2CID 24002003.
^ ^a ^b Johns, Paul (2014-01-01). "Chapter 14 - Multiple Sclerosis". Clinical Neuroscience. Churchill Livingstone. pp. 181–196. doi:10.1016/B978-0-443-10321-6.00014-X. ISBN 978-0-443-10321-6.{{cite book}}: CS1 maint: date and year (link)
^ ^a ^b Davis, Scott L.; Jay, Ollie; Wilson, Thad E. (2018). "Thermoregulatory dysfunction in multiple sclerosis". Handbook of Clinical Neurology. Vol. 157. Elsevier. pp. 701–714. doi:10.1016/B978-0-444-64074-1.00042-2. ISBN 9780444640741. ISSN 0072-9752. PMID 30459034.
^ ^a ^b White, A.T.; Wilson, T.E.; Davis, S.L.; Petajan, J.H. (2000). "Effect of precooling on physical performance in multiple sclerosis". Mult Scler. 6 (3): 176–180. doi:10.1177/135245850000600307. PMID 10871829. S2CID 41165079.
^ ^a ^b White, L.J.; Dressendorfer, L.H. (2004). "Exercise and multiple sclerosis". Sports Med. 34 (15): 1077–1100. doi:10.2165/00007256-200434150-00005. PMID 15575796. S2CID 27787579.
^ W. Uhthoff: Untersuchungen über die bei der multiplen Herdsklerose vorkommenden Augenstörungen. Archiv für Psychiatrie und Nervenkrankheiten, Berlin, 1890, 21: 55-116 and 303-410.
^ Guthrie, T.C.; Nelson, D.A. (1995). "Influence of temperature changes on multiple sclerosis: critical review of mechanisms and research potential". J Neurol Sci. 129 (1): 1–8. doi:10.1016/0022-510x(94)00248-m. PMID 7751837. S2CID 12555514.