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16 Articles in Volume 20, Issue #5
20/20 with Drs. Carmen R. Green and Johnathan Goree: Racial Disparities in Pain Care
A Kratom Primer: Miracle Medicine or Herb of Abuse?
A Pilot Study: Incidence and Prediction of Diversion among Opioid Therapy Patients
Analgesics of the Future: G-Protein Biased Mu-Opioid Receptor Ligands
Application Note: Decellularized Human Placenta in the Treatment of Infracalcaneal Heel Pain
Are Clinicians Effectively Counseling Patients on Safe Opioid Storage and Disposal? Survey Results
Ask the PharmD: How to Manage Pain Meds During Pregnancy?
Behavioral Medicine: Managing Anxiety and Maladaptive Behaviors
Case Report: Spinal Cord Stimulation for the Treatment of Pain Associated with Chronic Pancreatitis
Differential Diagnoses: Inflammatory or Non-inflammatory Chronic Back Pain?
Pelvic Inflammatory Disease: Diagnosis, Education, and Treatment Options
Product Review: Non-Invasive Neuromodulation for the Treatment of the Most Difficult Pain Conditions
Provider Perspective: Carpal Tunnel's Association with Hypothyroidism
Research Insights: Opioid Use During the Peripartum Period – What to Expect
Special Report: Race, Pain Management, and the System
When Patients Become Pregnant: How to Maintain Chronic Pain Management

Provider Perspective: Carpal Tunnel's Association with Hypothyroidism

Patients with carpal tunnel symptoms are not routinely tested for thyroid disease despite hypothyroidism being among its common etiologies. How clinicians can avoid a missed diagnosis.

Carpal tunnel syndrome is the most common and widely studied nerve entrapment syndrome, accounting for 90% of all such disorders.1 The syndrome is caused by compression of the median nerve as it travels through the wrist at the carpal tunnel.2 Patients with carpal tunnel syndrome (CTS) may experience pain and paresthesia in the distribution of the median nerve, which includes the palmar aspects of the thumb, index finger, middle finger, and the radial half of the ring finger.3 This pain may be a detriment the patient’s ability to work and quality of life.

Although the etiology is not completely known, repetitive use of the wrist, advanced age, obesity, pregnancy, trauma, amyloidosis, diabetes mellitus, kidney disease, osteoarthritis, and thyroid disease are considered to be risk factors for the development of CTS.4 The syndrome can occur secondarily with these diverse conditions, but most cases of CTS are idiopathic. Early diagnosis is important to prevent disability as a result of entrapment neuropathy.

Although electrophysiological studies remain the “gold-standard” to identify CTS, ultrasonography (US) has been shown to be useful in diagnosis5,6 in combination with clinical history and symptoms and physical exam findings.7,8  Once a diagnosis is made, conservative treatment options include wrist splinting, steroid injections, and stretching. Cases that fail conservative management or involve extensive nerve damage warrant surgical release. 

Current recommendations from the American Academy of Orthopaedic Surgeons (AAOS) for diagnosis and treatment of CTS utilize a relatively standard approach to address neurologic symptoms, regardless of the etiology.9

Although the etiology is not completely known, repetitive use of the wrist, advanced age, obesity, pregnancy, trauma, amyloidosis, diabetes mellitus, kidney disease, osteoarthritis, and thyroid disease are considered to be risk factors for the development of carpal tunnel syndrome. (Image: iStock

 

Carpal Tunnel and Thyroid Disease

As described, thyroid disease is one of the many conditions known as etiologies of CTS. Despite the number of cases of carpal tunnel syndrome that are associated with underlying thyroid disease, patients complaining of CTS symptoms are not routinely tested for thyroid disease.9

However, CTS may be the presenting symptom or complaint in patients with undiagnosed hypothyroidism. There is increasing evidence for identifying hypothyroid-related CTS and treating the CTS primarily with thyroid hormone.3 Doing so may avoid unnecessary surgical intervention and provide long-term relief or resolution of symptoms. In addition, the efficacy of surgical management may be reduced in patients with untreated hypothyroidism.10

The following discussion will navigate diagnostic and treatment approaches to carpal tunnel syndrome, with a focus on the considerations in hypothyroid-related cases.

 

Diagnosing Carpal Tunnel Syndrome (CTS)

Physical Exam

Clinical symptoms along with a thorough history and physical exam aid in the diagnosis of CTS.  Common physical findings include positive Phalen and Tinel Sign. The Phalen sign, described as paresthesia after 60 seconds of wrist flexion, is 85% sensitive and 90% specific for CTS.11 Tinel sign, or paresthesia after repeated tapping on the median nerve, has a sensitivity of 62% and a specificity of 93%.11 Both tests aid in the initial assessment of CTS, but may need to be paired with electrodiagnostic or ultrasonographic studies for definitive diagnosis.

Electromyography (EMG)

The confirmatory test for diagnosis of CTS is neurophysiological testing (EDX). This includes a nerve conduction study, which determines the distal motor latency and distal sensory latency using the average cutoff values of 4.28 ms and 3.37 ms respectively for diagnosis.12 Needle EMG of the abductor pollicis brevis muscle is also performed to evaluate nerve function and quantify the severity of carpal tunnel syndrome.13 The procedure is painful and is not a necessary step in diagnosis, but it remains the only definitive method to quantify motor axon loss.13,14 With a sensitivity of 85% to 90% and a specificity of 82% to 90%, EDX is used for evaluating the extent of nerve damage to determine the best treatment plan for the patient.

EDX can also help to rule out other diagnoses. Although uncommon, a number of reported CTS cases stem from a conversion disorder or neurological disorder that warrants a different treatment regimen altogether.13,15

However, while EMG remains a helpful diagnostic tool, it is considered to be less accessible and less convenient compared to other diagnostic methodologies, such as ultrasound.

Ultrasound

Musculoskeletal ultrasound is growing in use as an additional diagnostic option for CTS. Ultrasonography can help clinicians visualize the nerve inside the canal, along with the surrounding structures. The changes in volume and structure of the nerve can be detected using this technique as well.

As the nerve cross-sectional anatomy (CSA) increases at the inlet due to a narrowed tunnel, measuring CSA at this level may increase the suspicion.16,17 A median nerve CSA of at least 9 is the current diagnostic criterion for diagnosing carpal tunnel syndrome.18 Because the CSA measurement correlates to the severity of the syndrome, ultrasound can determine the efficacy of different treatment approaches.18 A significantly large CSA may suggest the need for a surgical approach.18

Treating Carpal Tunnel Syndrome

In general, patients with mild to moderate nerve damage resulting from carpal tunnel syndrome may benefit from conservative treatments and should explore nonsurgical options before considering surgical release.13 Patients with severe nerve damage, including those with severe axon loss, however, will benefit from immediate surgery to avoid irreversible nerve damage.9,13 Below are treatment approaches and considerations for each.

Wrist Splinting

Management of CTS typically begins with noninvasive interventions such as wrist splinting. The splint maintains the wrist in a neutral position, preventing excessive flexion and extension of the wrist in order to decrease positional impingement of the median nerve. Neutral-angle wrist splinting has a success rate of 37% at curing carpal tunnel syndrome symptoms.19,20 Additionally, the duration of symptoms and EMG results do not correlate with the success of wrist splinting in relieving symptoms.21 Therefore, unless severe or irreversible damage is suspected, a trial of wrist splinting at night is warranted as the initial treatment approach for patients experiencing symptoms.21

After 2 weeks of splinting at night, evaluating improvement in symptom severity and in the number of paresthesia episodes may sufficiently predict the long term benefit of splinting for the patient.21 For patients that lack improvement, continued splinting may not provide relief, and alternative treatment options may need to be considered as described below.

Corticosteroid Injections

When splinting fails to relieve the symptoms of carpal tunnel syndrome, corticosteroid injections may be considered as an alternative nonsurgical treatment. Corticosteroid injections reduce inflammation and have a 70% success rate of relieving symptoms initially, but recurrences in CTS symptoms are common.19

A 2018 randomized clinical trial conducted by So, et al, compared the effectiveness of wrist splinting with corticosteroid injections after one month of treatment.22 At 1-month follow-up, both wrist splinting and corticosteroid injections yielded significant improvement per the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) scoring, recommended assessment by the AAOS, with the corticosteroid injection group showing higher patient satisfaction scores. Only the corticosteroid injection group demonstrated significant improvement in objective hand function. Thus, the results support the effectiveness of corticosteroid injections as an alternative to splinting for short-term relief of symptoms.

Although injections may provide symptomatic relief, important factors such as long-term effectiveness and cost of steroid injections were not considered in the above study and may impact the patient’s decision to receive corticosteroid injections.

Ly-Pen, et al, conducted a clinical trial to assess the long-term effectiveness of steroid injections compared to surgical intervention.23 After 3 months of treatment, steroid injections were found to be more effective than surgical intervention. However, at 12 months, both steroid injections and surgery proved to be effective with no significant difference between either treatment options. It is possible that the discrepancy at 3 months may be accounted for by post-surgical inflammation in the wrist. Nonetheless, steroid injections proved to be effective at relieving symptoms for up to 1 year and may be as effective as surgical intervention.  

Yoga

Yoga has been proposed as an effective method to relieve CTS symptoms due to its ability to cause musculoskeletal relaxation.20 To examine the effect of a yoga-based treatment regimen for CTS, Garfinkel, et al, conducted an 8-week preliminary controlled trial.24 A yoga group was assigned stretches and strengthening exercises, while the control group was assigned a wrist splint, the standard treatment approach.

Both yoga and wrist splinting reduced sleep disturbance, and median nerve motor and sensory conduction time.

The yoga group showed statistically significant improvement in grip strength, pain intensity, and Tinel sign when compared to the wrist splint subjects. The results of this study supported yoga as an effective treatment for CTS; however, the findings were limited due to small sample size (n = 62) and failure to account for compliance among the wrist splint subjects.

Further research exploration on this topic may prove yoga to be an excellent treatment option for CTS. Potential benefits include that the practice requires only simple stretches, incurs mobility and relaxation, and is an affordable alternative to surgical approaches.

Surgery

For patients who have severe nerve damage or no success with conservative treatments, surgical decompression may be considered. The standard surgical procedure involves an incision through the transverse carpal tunnel ligament in order to relieve pressure in the canal that the median nerve courses through.25

Gerritsen et al, performed an RCT to compare the success rates of surgical release with splinting.25 It was found that after 3 months of treatment, the splinting group had a success rate of 54% (46/86)based on general improvement of CTS symptoms, while the surgery group had a success rate of 80% (62/78). At 18 months, the success rate for the splinting group was 75% (59/79) while the success rate for the surgery group was 90% (61/68).

Although surgery was shown to be more successful than splinting at treating the symptoms of carpal tunnel syndrome, the severity of nerve damage prior to treatment group assignment may have affected the patients’ response to surgery vs. conservative splinting.     

In general, surgery can be very successful in treating CTS, with any persistence of symptoms likely due to incomplete surgical decompression.26 Still, it is estimated that 58% of patients who undergo surgery will report at least one complication during the first 18 months post-operation.25Possible adverse effects include painful scars, stiffness, skin irritation, wound hematoma, wound infection, pillar pain, and reflex sympathetic dystrophy.

Due to the risk of complications, surgery should be considered only after patients fail conservative approaches or when severe median nerve damage is identified through appropriate diagnostic tests.27

 

Considering Hypothyroidism in Carpal Tunnel Presentation

As noted, laboratory testing is typically not performed as part of CTS diagnosis, yet 41% of CTS cases occur with an underlying disease, such as thyroid disease, diabetes, or arthritis.28 It is estimated that 29% of patients with hypothyroidism develop carpal tunnel syndrome.

Initial symptomatic management for CTS without laboratory testing can lead to missed diagnosis of hypothyroidism.29 Proper diagnosis and effective thyroid hormone regulation in the treatment of CTS in patients with underlying thyroid diseases are explored below.

The CTS-Thyroid Connection

Hypothyroidism is diagnosed based on laboratory tests revealing a low thyroid hormone level and a high thyroid-stimulating hormone (TSH) level. Thyroid hormone is a very important regulator of the central and peripheral nervous system, and imbalance in this hormone is commonly associated with neuropathy.

The likely pathogenesis of CTS is aminoglycan and mucin deposition, which increases pressure in the canal and causes demyelination of the median nerve.30 The progression to CTS in hypothyroidism is fairly common and supports the notion that unregulated levels of thyroid hormone are a major risk factor for CTS.

Presence of underlying thyroid disease can affect the clinical presentation and diagnostic efficacy among patients with hypothyroidism. For instance, only 38% of thyroid-associated cases of CTS fit the EDX diagnostic criteria despite clinical symptoms and physical exam suggesting CTS.31

Hypothyroidism can also influence the efficacy of common CTS treatments. Roshanzamar et al, performed a case-controlled study to compare the outcome of surgical decompression in hypothyroid vs euthyroid patients, or patients with normal T4 and TSH levels.10 In both groups, post-surgical improvement was noted by a decrease in BCTQ scores, however, there was a larger reduction in scores in euthyroid patients. As evidenced by this study, a well-regulated thyroid hormone level can help to ensure better treatment results, demonstrating the importance of proper diagnosis and treatment of thyroid disease in CTS.

Several additional studies on hypothyroid-related CTS have focused on the effectiveness of levothyroxine for thyroid hormone replacement.

Adessive et al, compared nerve conduction in controlled hypothyroidism being treated with levothyroxine vs uncontrolled hypothyroidism. The groups showed little differences in motor nerve conduction velocity, but a significantly lower sensory nerve conduction velocity in the uncontrolled hypothyroid patients was noted.32 Furthermore, statistically significant improvement in EDX values for median motor distal latency and median sensory nerve conduction have also been demonstrated after 3 months of hormone replacement treatment.33 Similarly, ultrasonographic comparison in patients with newly diagnosed hypothyroidism before and after 3 months of thyroxine treatment revealed a significant reduction in CSA along with improvement of symptoms.34,35

The Obesity Connection

In addition to growing evidence that thyroid hormone plays a role in many carpal tunnel syndrome cases, associated patient obesity has been proposed as a confounding factor as well. This largely stems from the understanding of weight gain as a common symptom in hypothyroidism. Fatty deposition from obesity is recognized as a risk factor for CTS by creating pressure on the median nerve.36 The extra adipose tissue is also a source of inflammation and free radicals, which can directly damage the median nerve and lead to CTS.32

Studies have shown that CTS symptoms in patients with hypothyroidism can be completely reversed with thyroid hormone replacement,33 and while weight gain can play a role in the development of CTS, obesity alone does not explain the effectiveness of levothyroxine in treating CTS. 

Subclinical Hypothyroidism

While several researchers have investigated hypothyroid-related CTS, there are a limited number of studies on the relationship between subclinical hypothyroidism and CTS. The diagnosis of subclinical hypothyroidism is made upon laboratory testing that reveals a normal free T4 level with an elevated TSH level.37 There are some cases that remain asymptomatic, but cases associated with cognitive impairment, depression, and nerve function have been identified.38-41

Similar to the results of the hypothyroid-related CTS studies, it has been shown that symptoms of subclinical hypothyroidism significantly improved after initiation of levothyroxine treatment.39,41

Currently, there is no widely accepted explanation for the manifestation of symptoms, including CTS, in subclinical hypothyroidism. The treatment of subclinical hypothyroidism with levothyroxine remains controversial. Yet, because thyroid hormone treatment has been shown to reverse symptoms of CTS, treatment with levothyroxine may be warranted even in subclinical hypothyroid cases.

Of note, current theories suggest that the uncontrolled level of T4 in hypothyroidism may play a role in causing CTS, yet, this does not address the reported cases of CTS in patients with subclinical hypothyroidism, where levels of free T4 are normal. These special cases may suggest that the CTS and additional symptoms in subclinical hypothyroidism may be caused by TSH itself. Additional studies that investigate CTS cases in subclinical hypothyroidism may shed light on the physiologic role of TSH in the body and the relationship between TSH and clinical symptoms.

Continue Reading:
Carpal Tunnel Syndrome: Chronic Overuse and Clinical Management
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