Introduction
Restless legs syndrome (RLS) and peripheral neuropathy (PN) may sound like abstract, big words but they are terms used to describe surprisingly common conditions affecting the nervous system. They might sound unrelated but often overlap in the symptoms they cause and the discomfort they bring. They are so similar that doctors usually take special care to diagnose accurately. This article will delve into how these two conditions are related, their impact on people’s lives, and what can be done to help anyone suffering from them.
What is restless legs syndrome (RLS)?
Restless legs syndrome (also called Willis-Ekbom disease) is a surprisingly common disease.1 In fact, studies have revealed that it affects 2 to 5% of the European and United States general population.1,2,3 As defined by the International Restless Legs Syndrome Study Group (IRLSSG)4, RLS is a reflexive condition primarily characterised by a compulsive urge to move the legs due to pins and needles or even shock-like sensations, exacerbated by rest and temporarily relieved by activity.
While its cause is largely unknown, it has been linked to an imbalance in dopamine, the hormone that makes us “feel good”, in the brain, and genetic factors.2
Symptoms of RLS
The major symptom of RLS is the urge to move the legs, usually accompanied by uncomfortable sensations while at rest.1,2,3,4 These uncomfortable sensations have been described by patients as uncomfortable using terms such as creeping, crawling, twitching, throbbing, and pulling sensations. Some have even more distressing symptoms such as aches and feelings of electric shocks. These symptoms typically worsen in the evening or at night. This might be because the night, for most people, is associated with long hours of rest and respite, which may in turn trigger leg twitching and discomfort that brings significant difficulty in both falling asleep or remaining asleep. Few cases have been documented of RLS also affecting the mouth, neck, arms, abdomen, and genitals.5
Risk factors for RLS
Like dozens of conditions, the exact cause of RLS largely remains unknown. However, some risk factors may predispose an individual to RLS including genetic factors, iron deficiency, chronic or long-term diseases, and certain medications.
Genetic predisposition
You may be at an increased risk of RLS if your parents have suffered or are sufferers of the condition.
Iron deficiency
Heavy menstrual bleeding, chronic kidney disease, frequent blood donation, and prolonged bleeding from the gut are among the common causes of iron deficiency. This refers to not enough iron in the blood and has been found in individuals who suffer from RLS.
Diabetes and peripheral neuropathy
Many individuals with poorly controlled diabetes eventually suffer damage to the nerves in their hands and feet, resulting in peripheral neuropathy which predisposes them to RLS.
Medication side effects
Certain medications known as dopamine agonists used in the treatment of Parkinson’s disease have been linked to an increased risk of RLS.
Impact of RLS on quality of life
- Sleep disturbances: RLS has been named one of the main causes of insomnia.2,6,7
- Daytime fatigue and cognitive impacts
- Emotional and psychological distress
What is peripheral neuropathy (PN)?
On the other hand, peripheral neuropathy is a condition that develops due to damage to the nerves that are found outside the brain and spinal cord (peripheral nerves, as opposed to central).5,8
To understand peripheral neuropathy, it may be necessary to understand that the human body possesses a nervous system that is broadly categorised into the central and peripheral nervous systems.8 The central nervous system is made up of the brain and spinal cord which are the “backbone” of the nervous system. On the other hand, the peripheral nervous system consists of sensory and motor nerves found all over the body. While sensory nerves help in the transmission of impulses such as temperature, touch and pain, the motor nerves control muscular activity. Damage to these sensory and motor nerves from conditions like diabetes, results in poor coordination of the impulses/sensations and muscular activity, thereby resulting in the phenomenon known as peripheral neuropathy.5
Symptoms of PN
- Tingling, numbness, and pain in the hands and feet
- Increased sensitivity to touch
- Burning, shooting or stabbing pain in affected areas
- Muscle weakness, loss of balance or coordination
Causes and risk factors of PN
There are several causes and risk factors for peripheral neuropathy, and some of the common ones are as follows:
Diabetes mellitus
In advanced countries such as the UK and the US, diabetes (both type 1 and type 2) is the major cause of peripheral neuropathy. Approximately 1 in 10 people over 55 years in the UK and 30 million people in the US with diabetes have been reported to suffer from PN.6 Nerve damage among diabetic patients results from poorly controlled high blood sugar levels.
Viral infections: shingles and HIV
Shingles is a painful skin rash caused by the same virus that causes chickenpox which also leads to damage of the peripheral nerves.8 Other viral infections such as HIV have also been found to cause peripheral neuropathy.
Exposure to medications
Certain medications such as chemotherapy drugs, antibiotics, antiretrovirals (HIV drugs), anti-seizure drugs, and antihypertensives have been linked to peripheral neuropathy.8
Impact of PN on quality of life
- Challenges with mobility and daily activities
- Chronic pain and discomfort
- Increased risk of injury due to loss of sensation
How are RLS and PN related?
Overlapping symptoms
It is unsurprising that people, and sometimes doctors, often get the two conditions confused due to the overlap in their symptoms such as tingling, burning, leg discomfort, and sleep disturbances; similarities in their risk factors such as diabetes.2,5,6 In fact, patients with diabetes are more likely to develop RLS, which is also the case for PN. According to a study, about 21% of diabetic patients also have RLS.6 Patients have been observed to present with or provide ambiguous descriptions of their symptoms which often contribute to the diagnostic dilemma doctors have to work through.5,6,7
Despite this overlap, the experience of PN differs from RLS in that it happens at any time of the day, can affect any part of the body (although the limbs are the most affected), there is typically no related urge to move the legs, and the level of activity of the patient hardly matters.2,5,6,8
In addition, PN is more associated with conditions such as diabetes, alcoholism, infections, and toxins on the nerves, while RLS has a close relationship with genetic factors, low blood iron levels, pregnancy, and kidney failure.1,2
Involvement of the nerves
Both conditions affect the peripheral nerves and may cause a significant impact on movement, however, unlike PN, RLS does not cause nerve damage.1,2,5,6 Instead, it only involves the transmission of abnormal signals in the legs.
Diagnosis
Of course, diagnosing RLS and PN is not a walk in the park. It is not enough that you feel leg tingling, twitching, or sleeplessness for either of them to be diagnosed. Diagnosis is done at the GP or hospital following a careful consideration of your symptoms, extensive physical examinations, and the application of specialised tests.
Diagnostic criteria for RLS
International Restless Legs Syndrome Study Group (IRLSSG) criteria have been generally accepted as the most standardised yardstick for RLS diagnosis as there is no special lab test for diagnosis.1,4 It includes five criteria that must be satisfied to conclude whether a patient has RLS or not.
Diagnostic approaches for PN
- Careful history and physical examination
- Nerve function tests (e.g., electromyography, nerve conduction studies)
- Blood tests to identify underlying conditions such as diabetes
Treatment and management
There is an importance in treating both conditions to improve overall quality of life such as using a multi-disciplinary approach involving neurologists, primary care physicians, and possibly a pain specialist.1,3,8
Treatment options for RLS
- Medications (dopamine agonists, benzodiazepines, etc.)
- Lifestyle changes and home remedies such as the restriction of caffeine and tobacco, massage and adopting relaxation techniques, and discontinuing medications that oppose dopamine in the body.
- Iron supplementation if necessary
Treatment options for PN
- Managing underlying causes such as controlling blood sugar in diabetes
- Adequate pain relief
- Medications
- Physical therapy and safety measures to prevent injury
Summary
- PN and RLS both involve abnormal nerve function causing significant discomfort and sleep disruption
- PN results from nerve damage due to conditions such as diabetes, affecting various body parts, while RLS primarily affects the legs due to dopamine pathway dysfunction
- Treatments for PN focus on the underlying cause and pain relief, whereas RLS treatments aim to alleviate symptoms and improve sleep
- This warrants the importance of early diagnosis and integrated care to improve quality of life
References
- Gossard TR, Trotti LM, Videnovic A, St Louis EK. Restless legs syndrome: contemporary diagnosis and treatment. Neurotherapeutics [Internet]. 2021 Jan;18(1):140–55. Available from:https://pubmed.ncbi.nlm.nih.gov/33880737/
- Anyfantakis D, Katsanikaki F, Symvoulakis EK. Diabetic neuropathy and restless legs syndrome: can a known chronic condition slow down our diagnostic way of thinking? A case report and a short literature overview. Med Pharm Rep [Internet]. 2020 Jul [cited 2024 Jun 16];93(3):297–300. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7418840/
- nhs.uk [Internet]. 2017 [cited 2024 Jun 16]. Restless legs syndrome. Available from: https://www.nhs.uk/conditions/restless-legs-syndrome/
- Allen RP, Picchietti DL, Garcia-Borreguero D, Ondo WG, Walters AS, Winkelman JW, et al. Restless legs syndrome/Willis-Ekbom disease diagnostic criteria: updated International Restless Legs Syndrome Study Group (Irlssg) consensus criteria--history, rationale, description, and significance. Sleep Med [Internet]. 2014 Aug;15(8):860–73. Available from: https://pubmed.ncbi.nlm.nih.gov/25023924/
- Jiménez-Jiménez FJ, Alonso-Navarro H, García-Martín E, Agúndez JAG. Association between restless legs syndrome and peripheral neuropathy: A systematic review and meta-analysis. Eur J Neurol. 2021 Jul;28(7):2423–42. Available from: https://pubmed.ncbi.nlm.nih.gov/25023924/
- Cuellar NG, Dorn JM. Peripheral diabetic neuropathy or restless legs syndrome in persons with type 2 diabetes mellitus: Differentiating diagnosis in practice. J Am Assoc Nurse Pract [Internet]. 2015 Dec;27(12):671–5. Available from: https://pubmed.ncbi.nlm.nih.gov/26465658/
- Ohayon MM, O’Hara R, Vitiello MV. Epidemiology of restless legs syndrome: A synthesis of the literature. Sleep Medicine Reviews [Internet]. 2012 Aug [cited 2024 Jun 16];16(4):283–95. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1087079211000578
- nhs.uk [Internet]. 2017 [cited 2024 Jun 16]. Peripheral neuropathy. Available from: https://www.nhs.uk/conditions/peripheral-neuropathy/