Carpal Tunnel Ultrasound and Injection

Authors: Dr Iain Duncan*
                            Dr Wes Cormick *

What are the generally accepted indications for a carpal tunnel ultrasound and injection?

There are two main indications for carpal tunnel ultrasound:

• diagnosis of the condition; and
• an aid for guiding therapeutic injection.

Diagnosis of carpal tunnel syndrome is usually clinical, but might need to be confirmed in patients who are being considered for surgery or in patients where the diagnosis is uncertain, or there are atypical features.

Ultrasound for carpal tunnel syndrome has been carried out over the past 20 years and is considered accurate as a diagnostic test.¹ It is also able to show pathology of the adjacent structures that might be contributing to compression of the median nerve, such as synovitis or ganglia.

Ultrasound has the additional benefit of guiding an injection, which is recommended in managing carpal tunnel syndrome (level A evidence).² It can provide temporary or occasionally longer lasting relief. Injection of the carpal tunnel is helpful in confirming reversible symptoms before surgery, delaying surgical treatment, avoiding surgical treatment in some cases and providing symptomatic relief particularly where the long-term prognosis is good. It is less likely to help in longstanding and chronic cases, or cases where there is motor weakness and significant nerve dysfunction.

What are the prerequisites for having a carpal tunnel ultrasound and injection done?

Any patients who are on coumarin anticoagulants need to have an up-to-date INR before the injection. Diabetics should be warned about the possibility of a temporary elevation in blood glucose levels. Patients with motor weakness might require further evaluation by a specialist before the injection.

What are the absolute contraindications for a carpal tunnel ultrasound and injection?

Uncontrolled anticoagulation or active local infection are the only absolute contraindications.

What are the relative contraindications for a carpal tunnel ultrasound and injection?

Uncontrolled diabetes, clotting disorders and uncontrolled therapeutic anticoagulation.

What are the adverse effects of a carpal tunnel ultrasound and injection?

This is a very safe procedure with few significant risks. Very few patients complain of side-effects, but occasionally problems are experienced.

Immediate: Local bruising and bleeding can occur. A temporary aggravation of symptoms for between 1–3 days might be seen in some patients. There is a remote risk of the needle passing through the nerve, which would cause severe pain or nerve symptoms. In the author’s experience of over 25,000 guided carpal tunnel injections, this has never happened, but is a particular risk when injections are carried out without ultrasound guidance. Allergic reactions are uncommon, but can occur. The exact risk of this is not known.

Delayed: There is a risk of infection, which is very small, and probably lies between 1 in 20,000 and 1 in 75,000 injections carried out.

Is there any specific post-procedural care required after a carpal tunnel ultrasound and injection?

The affected limb or part should generally be rested completely for 6 hours, and then use of the part minimised for between 1 and 3 days.

The corticosteroid does not start working for at least 24 hours, and sometimes up to 7 days. Numbness and weakness generally take longer to respond to corticosteroid than pain or when compared to the more rapid symptom improvement in bursal/joint injections.

A major flare of symptoms generally indicates a local reaction is occurring to a part of the injected material or simply to the trauma of the procedure. Anti-inflammatories, rest (use of a splint) and cold packs can be helpful. The injection site should be reviewed for infection, although this is less likely than a local reaction.

Are there alternative imaging tests, interventions or surgical procedures to a carpal tunnel ultrasound and injection?

Nerve conduction tests and MRI can also be used for diagnosis.

Anti-inflammatories, simple analgesia, wrist splints and rest can all provide relief from carpal tunnel syndrome in some patients.

Depending on the possible underlying cause and contributing factors of the carpal tunnel syndrome, other medical management might be indicated. The more commonly-associated medical conditions are hypothyroidism, rheumatoid arthritis and diabetes.

Surgical decompression (open or key-hole) is commonly carried out for carpal tunnel syndrome.

Further information about carpal tunnel ultrasound and injection:

Carpal tunnel ultrasound and injection is operator dependent, and is not available at all radiology practices. It is best carried out only at sites where a radiologist experienced in the procedure is in attendance.

References:

1. Evidence-based Guideline: Neuromuscular Ultrasound for the Diagnosis of Carpal Tunnel Syndrome www.aanem.org/getmedia/1a029bcf-81df-48d4-839a-f0bdda6128f4/NMUS-for-DX-of-CTS-for-web.pdf [accessed September 2016]
2. National Guidance Clearing House
   guideline.gov/content.aspx?id=34436&search=carpal+tunnel+syndrome [accessed September 2016]

*The author has no conflict of interest with this topic.

Page last modified on 26/7/2017.