Introduction

Pain of the dorsal aspect of the distal forearm and wrist is common. Symptoms may arise from either joint structure or periarticular soft tissue. The most frequent differential diagnosis includes wrist ligament sprain, ganglion cyst, tendinitis and muscle sprain.^{[1] .}History and physical examination often provide a specific diagnosis or limit the differential, but the diagnosis remains uncertain in a subset of patients because of an atypical presentation that rarely encountered. MRI can help to narrow the differential and improve the evaluation of forearm and wrist symptoms. Its incidence is reported between 0.2% and 0.37%.^[2]

The distal intersection syndrome relates to tenosynovitis of the extensor pollicis longus (EPL) tendon (3^rd extensor compartment), where it crosses the extensor carpi radialis longus (ECRL) and brevis (ECRB) tendons (2^nd extensor compartment).^[3] It is distinct from intersection syndrome which occurs more proximally in the forearm at the intersection of the first and second extensor compartments.

The crossing of the second extensor compartment is typically located just distal to Lister’s tubercle. The tendon sheaths of the EPL and the ECRB are connected by a communicating foramen.^[4] This is probably why inflammation of the EPL tendon spreads to the second compartment or vice versa [Figure 1].

Case Presentation

A 55 yrs old male presented with the history of chronic pain and swelling of the dorsal aspect of the left distal forearm and wrist. MRI of left wrist shows the proximal, mid and distal intercarpal joints are normal with smooth and parallel cortical bones constituting joints. No evidence of fluid collection. Carpal arch appears normal. Thickening of tendon sheath due to edema around the second and third extensor compartment tendons which appears isointense on T-1 [Figure 2] & hyperintense on T2 & STIR sequence [Figure 3]. Tenosynovitis involving tendon of second and third extensor compartments.

Discussion

Intersection Syndrome is a specific painful disorders of the forearm. First described in 1841 by Velpeau, it has also been referred to in literature by the terms “peritendinitis crepitans”, “oarsmen’s wrist”, “crossover syndrome”, “subcutaneous perimyositis”, “squeaker’s wrist”, “bugaboo forearm”, and “abductor pollicis longus syndrome”.^[5]

Dobyns et al.^[6] introduced the term “intersection syndrome,” an anatomic designation related to the area in which the musculo-tendinous junctions of the first extensor compartment tendons (abductor pollicis longus and extensor pollicis brevis tendons) intersect the second extensor compartment tendons (extensor carpi radialis longus and extensor carpi radialis brevis tendons), at an angle of approximately 60 [Figure 1] and which is approximately 4cm far from the Lister´s tubercle.^[5] Concerning the distal intersection syndrome there is tenosynovitis particularly of the extensor pollicis longus (EPL) tendon, where it crosses the extensor carpi radialis longus (ECRL) and brevis (ECRB) tendons. It is distinct from proximal intersection syndrome which occurs more proximally in the forearm at the intersection of the first and second extensor compartments. The particularity of our case is distal intersection syndrome which shows Tenosynovitis involving tendon of second and third extensor compartments .

There is no consensus about the pathophysiology of this condition, but this syndrome usually develops in patients involved with sports-related activities, such as rowing, canoeing, playing racket sports, horseback riding, and skiing.^[7,8] In 1994, Palmer and Lane-Larsen reported a prevalence of 11.9% in a group of 42 skiers,^[9] developing typical symptoms within the first 2 days of activity. Presentation is pain and swelling in a region about 4–8 cm proximal to the Lister tubercle, where the first and second extensor compartment tendons cross. In more severe cases, wrist motion and direct palpation may produce crepitus.

MRI is well suited to show the findings of intersection syndrome, especially with fluid-sensitive sequences. The most important finding is the presence of peritendinous edema concentrically surrounding the second and the first extensor compartments, beginning at the point of crossover, 4–8 cm proximal to the Lister tubercle and extending proximally. Peritendinitis may be a more appropriate broader term, given that there may not be tendon sheath fluid found in this location.^[10]

 Symptoms resolve within 2-3 weeks in 60 % patient with rest and nonsteroid anti-inflammatory drugs, and splinting. Surgery is indicated for patients not responding to therapy. Tenosynovectomy and fasciotomy of abductor pollicis longus can be performed.

The main differential diagnosis is de Quervain's tenosynovitis, which may require an earlier surgical intervention.^[11]

Conclusion

Intersection syndrome is an overuse disorder of the dorsal distal forearm, presenting with particular symptoms and signs that may be clinically misdiagnosed. The diagnosis is made on the basis of clinical findings, which must be confirmed by imaging studies. It may be discovered only after an MRI especially during acute or sub acute periods. Thus, radiologists must keep in mind this possibility while diagnosing wrist pains because a clinical diagnosis could be difficult in such cases.