Carpal tunnel in both wrists may be ‘red flag’ for ATTR: Study
Imaging results may also show abnormalities linked to condition
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Carpal tunnel syndrome (CTS) in both wrists may be a red flag of transthyretin amyloidosis (ATTR), including hereditary transthyretin amyloidosis with polyneuropathy (hATTR-PN), a study showed.
The researchers also identified imaging abnormalities in the wrist that may point to ATTR.
“These preliminary findings can provide a foundation for future research aimed at validating these patterns and developing a diagnostic tool to facilitate early detection in ATTR patients,” the researchers wrote.
The study, “Ultra High-Resolution Ultrasound Features of Carpal Tunnel Syndrome in Transthyretin Amyloidosis: A Cross-Sectional Study,” was published in Muscle & Nerve.
ATTR refers to a group of progressive diseases caused by the buildup of toxic clumps of an abnormal transthyretin protein in tissues throughout the body, causing damage. It can occur because of mutations in the TTR gene (hereditary ATTR) or as a result of aging (wild-type ATTR).
Damage seen in both nerves and heart
The hereditary form of ATTR is commonly classified into two main types, depending on whether the toxic clumps build up mainly in the nerves outside the brain and spinal cord (hATTR-PN) or in the heart (hereditary transthyretin amyloid cardiomyopathy). The wild-type form usually affects older adults and mainly involves the heart.
However, increasing evidence suggests that most people with ATTR will develop damage in both the nerves and the heart, a form known as a mixed profile.
CTS, a condition characterized by abnormal pressure on the median nerve in the wrist, can cause numbness and tingling in the affected hand. It is often an early symptom of hATTR-PN and ATTR in general, and it frequently precedes an ATTR diagnosis by several years.
Because CTS is also common in the general population, clinicians are unlikely to suspect hATTR-PN as the cause. This can lead to delays in diagnosis and treatment.
To identify potential imaging markers of CTS in patients with hereditary ATTR, a team of researchers in the U.S. and Canada analyzed wrist ultrasound scans from 14 people with hereditary ATTR and six with wild-type ATTR, regardless of CTS symptoms. Wrist ultrasound uses sound waves to visualize the median nerve and other structures within the wrist.
Most participants were in their 70s, and 75% were men. Damage to multiple nerves, indicative of hATTR-PN, was present in 65% of patients. Still, a high proportion of participants (60%) showed heart damage.
A total of 17 patients (85%) had symptoms of CTS, and in all of them, both wrists were affected. This can happen in the general population, but it’s not as common as having CTS in just one wrist.
“Importantly, all symptomatic patients exhibited bilateral [both-sides] CTS symptoms … suggesting that bilateral involvement may serve as a potential red flag” of ATTR, the researchers wrote.
Electrodiagnostic testing, which evaluates whether there are abnormalities in median nerve electrical function, confirmed CTS in most (85%) of these 17 symptomatic patients.
Wrist ultrasound results showed that participants with CTS (either based on symptoms or electrodiagnostic testing) had a significantly thicker median nerve than those without clinical or electrodiagnostic CTS.
This is a common feature of CTS in the general population, where the syndrome is usually associated with the nerve becoming inflamed and swollen. However, some of the patients had normal-sized median nerves despite having CTS symptoms, and most also had electrical abnormalities.
This suggests a “dissociation between sonographic and clinical/electrodiagnostic findings,” the researchers wrote, adding that this could be another potential red flag of ATTR.
A few other imaging anomalies were reported in ATTR patients with CTS. For example, thickening of the tissue surrounding the nerve and increased brightness on ultrasound were observed in 15 of the 40 evaluated wrists (37.5%), all with CTS symptoms and moderate to severe electrodiagnostic CTS.
The researchers postulated that these imaging features might be signs of ATTR, but they stressed that further studies with more patients — including direct comparisons against people with CTS unrelated to ATTR — will be needed to definitively define such imaging markers.
“These observations highlight the need for further [tissue health] correlation and larger, [follow-up] studies to clarify their diagnostic value and assess the impact of emerging therapies,” the researchers concluded.
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