A 36-year-old male software professional presented with complaints of pain in the left wrist and lateral half of the hand for 20 days. The patient suggests worsening of pain during activity. No history of trauma was elicited. He was referred for ultrasound of the left wrist to assess the median nerve.
On ultrasound the median nerve appears unremarkable. Axial images of distal forearm depict a hypoechoic rounded structure adjacent to the median nerve. On sagittal sections it corresponds to a tubular hypoechoic structure extending from the forearm into the carpal tunnel. This characteristic course coupled with arterial flow pattern on Doppler imaging clinches the diagnosis of a persistent median artery (PMA).Within the carpal tunnel this artery appears distended with echogenic contents and shows no colour flow confirming thrombosis.
Contrast enhanced MR angiography depicts an additional artery in the forearm between the radial and ulnar arteries originating from the anterior interosseous artery and extending into the carpal tunnel confirming a PMA. Absence of normal flow void and hyperintense signal within the artery on T1W/PD fat saturated images and rim enhancement with a central filling defect on contrast enhanced images confirm thrombosis of the PMA within the carpal tunnel. The thrombosed PMA is seen indenting the median nerve.
Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy of the upper extremity and occurs due to compression of the median nerve within the carpal tunnel. Various idiopathic, traumatic, inflammatory, infective, endocrine and congenital conditions as well as mass lesions (eg, ganglion cyst, neurogenic tumours) can cause CTS [1].
The median artery, a branch of the axial artery is the dominant blood supply to the developing hand in early fetal life and normally involutes before birth.
A persistent median artery (PMA) is one of the rare congenital conditions implicated as a cause of CTS [2]. The approximate incidence of PMA as a cause of CTS is 6% [3]. A persistent median artery (PMA) is commonly a branch of one of the forearm arteries and courses through the carpal tunnel, usually adjacent to the median nerve [4]. Thrombosis of the PMA within the carpal tunnel probably occurs due to repeated stress and vibration [5]. A thrombosed PMA likely causes CTS due to mass effect on the median nerve and possible irritation of the nerve by inflammatory changes surrounding the area of thrombosis. The cause of thrombosis in our patient, a software professional, was probably prolonged dorsiflexion at the wrist during work.
Ultrasound and MRI of the wrist are commonly requested in suspected cases of CTS. Apart from assessing the median nerve, a diligent search for abnormal structures occupying the carpal tunnel should be made in all cases. It is imperative to trace any abnormal structure within the carpal tunnel proximally, to assess possible extension into the forearm. A tubular structure in the forearm extending into the carpal tunnel separate from the median nerve is suggestive of a PMA with colour Doppler and contrast enhanced MR angiography aiding in confirmation [6]. A bifid median nerve (two nerve bundles within a common perineurium) in the carpal tunnel is a common association with a PMA and can be easily be easily detected on ultrasound to avoid inadvertent injury during surgery [7].
Treatment of a thrombosed PMA involves medical therapy to aid thrombolysis with surgery reserved for failed cases. Release of the transverse carpal ligament and resection of the artery are possible surgical options [2, 8]. Before resection it is essential to make sure that the PMA does not substantially contribute to hand circulation. Contrast enhanced MR angiography offers a relatively non-invasive means of visualising the extent of involvement of the artery in forming the palmar arch.
Thrombosed persistent median artery causing carpal tunnel syndrome.
1. Ultrasound Examination: On the palmar side of the left wrist, adjacent to the median nerve, a tubular structure is visible, showing anechoic lumen with local blood flow signals. A low-echo area suggestive of thrombus formation is noted, indicating possible lumen narrowing with heterogeneous echoes. The median nerve from the proximal transverse carpal ligament to the carpal tunnel segment appears thickened with increased cross-sectional area, consistent with common findings of Carpal Tunnel Syndrome (CTS).
2. MRI Examination: Axial images of the wrist reveal an enlarged median nerve within the carpal tunnel, with T2WI showing high signal intensity changes. A tubular vascular structure is seen adjacent to the median nerve, correlating with ultrasound findings. Contrast-enhanced images demonstrate this tubular structure is connected to the forearm arterial system, suggesting it could be a Persistent Median Artery (PMA). Some sequences show low-signal filling suggestive of thrombus formation.
Considering the patient’s occupational factors (sedentary work, prolonged fixed wrist posture), clinical symptoms (left wrist pain, exacerbation with activity, sensory disturbances in the median nerve distribution), and imaging findings (thickened median nerve within the carpal tunnel, adjacent persistent median artery with thrombosis), the most likely final diagnosis is “Carpal Tunnel Syndrome (CTS) caused by a thrombosed Persistent Median Artery.”
Based on the above diagnosis, the following treatment and rehabilitation recommendations are provided:
During the rehabilitation period, it is crucial to avoid maintaining the wrist in a prolonged hyperextended or flexed position. Take regular breaks for wrist rest and gentle stretching to reduce continuous compression risk.
Disclaimer: This report is based on the provided medical history and imaging data for reference only and does not replace an in-person consultation or a professional doctor's diagnosis and treatment advice. If you have any questions or changes in your condition, please consult a specialist and undergo further examinations in a timely manner.
Thrombosed persistent median artery causing carpal tunnel syndrome.
