A 45-year-old woman presented with persisting pain and numbness in the right wrist and hand for months. She had previously undergone an urgent percutaneous transluminal coronary angioplasty with stenting of the right circumflex artery for a non-STEMI infarction 8 months before, for which follow-up was uncomplicated.
Radiography did not show any abnormalities.
Focused ultrasound showed a tubular hypo-echogenic structure, which could be visualised at the ulnar side of the median nerve. This structure had a slight compressive effect on the median nerve. There was peripheral vascularisation around this structure on duplex ultrasound investigation, but no major blood flow was noted. The radial artery and ulnar artery had a patent aspect. There was no visualisation of musculotendinous pathology.
Further investigation with magnetic resonance imaging (MRI) was performed.
3-Tesla MR showed a linear structure lying ulnar to the median nerve with discrete contrast enhancement and surrounding oedema. The median nerve had a bifid configuration.
Background
The carpal tunnel is formed by the flexor retinaculum and the carpal bones. The flexor retinaculum is a continuation of the antebrachial fascia and is attached to the pisiform, hamate, scaphoid and trapezium. It contains nine tendons: four flexor digitorum superficialis tendons, four flexor digitorum profundus tendons, and the flexor pollicis longus tendon. The median nerve itself lies between the flexor digitorum profundus and the flexor digitorum superficialis tendons and gradually progresses to a more superficial volar position in the axial plane in around two out of three cases. In one-third of subjects the nerve exhibits either a radial or ulnar curve. [1] It has a mixed motoric-sensory function. Motoric branches innervate the thenar eminence: the opponens pollicis and abductor pollicis brevis muscles are innervated by the thenar branch of the median nerve, whereas the flexor pollicis brevis is normally innervated by the ulnar nerve, though sometimes with a mixed innervation by the ulnar and the median nerve. Sensory branches innervate the radial side of the 4th digit, as well as digits one till three.
Imaging perspective
Normally there are no vascular structures within the carpal tunnel. Two known variants, however, do have vascular structures coursing the carpal tunnel.
- Normally the superficial palmar arch and the deep palmar arch supply blood to the digits. Respectively, they branch from the ulnar and the radial artery. The superficial palmar arch lies volar to the flexor retinaculum, although a known variant of the normal anatomy with a superficial position under the antebrachial fascia is seldom reported.
- An embryological remnant of the axial artery can persist as a side-branch of the ulnar artery: the so-called persistent median artery. This is often associated with a high division of the median nerve, which then divides into two separate branches, both passing through the carpal tunnel: the so-called bifid median nerve. If a bifid median nerve is present, the artery lies in between the two branches. If not, then the artery lies ulnar to the median nerve. [2]
Take-home message
The above-mentioned vascular structures should always be reported when incidentally found on ultrasound examination. Not only are they surgically relevant, but they also have pathological potential as demonstrated by the case above.
Complete relief of the symptoms has been achieved after open carpal tunnel release.
Written informed patient consent for publication has been obtained.
Persistent median artery thrombosis
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Based on the provided ultrasound and magnetic resonance imaging (MRI), the following important features can be observed:
1. An aberrant vascular signal is visible in the carpal tunnel region (formed by the flexor retinaculum and the carpal bones). On the color Doppler ultrasound, this structure appears as a tubular formation exhibiting detectable blood flow signals.
2. Normally, the carpal tunnel contains only the flexor tendons and the median nerve; there should not be additional arteries or veins. In the current images, there is a suspected “persistent median artery” or a variant branch of the superficial/deep palmar arch traversing the carpal tunnel, closely associated with the median nerve.
3. MRI sagittal and axial images also indicate evidence of nerve compression in the carpal tunnel area. Some images show mild edema or signal changes in the soft tissue around the median nerve, suggesting inflammatory or edematous changes resulting from prolonged compression.
4. In the surgical images, the abnormal vascular course within the carpal tunnel and direct exposure of the median nerve are also observed, clearly showing the close proximity of the vessel to the nerve.
Based on the imaging and clinical history, the possible diagnoses or differential diagnoses include:
1. Carpal Tunnel Syndrome (CTS): Caused by compression of the median nerve within the carpal tunnel. Patients typically present with numbness and pain in the wrist and fingers, especially affecting the thumb, index finger, middle finger, and the radial half of the ring finger. Imaging may show thickening or edema of the nerve.
2. Persistent Median Artery with Median Nerve Compression: A rare congenital vascular variation in which a persistent median artery (PMA) travels through the carpal tunnel, potentially exacerbating the compression on the median nerve. In patients with such a variation who exhibit carpal tunnel syndrome symptoms, arterial-nerve co-compression should be considered.
3. Other Lesions Within the Carpal Tunnel: For instance, tendon sheath cysts, lipomas, or adjacent joint diseases can also cause nerve compression. However, given the current images highlighting abnormal vascular courses, compression due to vascular variation is more consistent with the findings.
Considering the patient’s age, months of persistent pain and numbness, and imaging findings indicative of a likely persistent median artery traversing the carpal tunnel and compressing the median nerve, the most likely diagnosis is: “Carpal Tunnel Syndrome combined with a vascular variation (persistent median artery) causing compression of the median nerve.”
The patient’s marked symptom improvement following surgery further supports this diagnosis. If there is still uncertainty or a need for detailed identification of the vascular variation, vascular angiography or additional intraoperative investigation can be performed to clarify the artery’s source and course.
1. Treatment Strategy:
- Conservative Treatment: For patients with mild carpal tunnel syndrome symptoms, approaches such as wearing a wrist splint, local immobilization, and oral or local corticosteroid injections can be attempted. However, in this case, where the patient has had symptoms for several months and experiences anatomical compression due to a vascular variation, conservative measures often have limited effectiveness.
- Surgical Treatment: For persistent symptoms with evident structural compression (e.g., persistent median artery or significantly thickened tendon sheath), open or minimally invasive transection of the transverse carpal ligament is the primary choice. In this case, an open carpal tunnel release was performed to expose and decompress the structures near the median nerve, resulting in significant relief of symptoms.
2. Rehabilitation/Exercise Prescription Recommendations (FITT-VP Principle):
- Frequency: During the first 1-2 weeks after surgery, perform gentle wrist mobility exercises 2-3 times a day, avoiding high loads or excessive extension.
- Intensity: Begin with low-intensity activities, focusing on mild joint range-of-motion exercises and finger grip-relaxation drills; gradually increase intensity. When pain or swelling subsides, introduce moderate weight-bearing or resistance band exercises.
- Time: Each session of exercises should last about 5-10 minutes, divided into short segments. As rehabilitation progresses, this can be extended to 10-15 minutes per session.
- Type:
• Early Stage: Finger flexion-extension exercises and active/passive range-of-motion training for the wrist;
• Intermediate Stage: Light resistance training, such as using a small grip ball or resistance band for gripping, and wrist rolling exercises;
• Late Stage: Incorporate functional training, such as simulating daily gripping and holding activities to enhance wrist and finger flexibility.
- Progression: As pain and numbness improve, gradually increase the range of motion and resistance. If there are concerns regarding cardiopulmonary function or bone health, consult a rehabilitation physician for evaluation and a phased strengthening program to ensure safety.
Disclaimer: This report serves as a reference analysis and cannot replace an in-person consultation or professional medical advice. If you have any questions or discomfort, please make sure to consult a healthcare professional or visit a hospital for further examination and treatment.
Persistent median artery thrombosis
