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Dual intersection syndrome of the forearm: a case report

The intersection syndrome, described since the 19th century, is an uncommon disorder associated with rubbing at the crossing point between the first dorsal compartment muscles and the radial wrist extensor muscles. Imaging modalities used to diagnosis this syndrome includes ultrasonography and magnetic resonance imaging. We reported a case of a 60-year-old man presented to our formation with painful swelling on the dorsum of the wrist and forearm. An MRI and an ultrasound were performed, and objectified a dual cross syndrome of the forearm.


Introduction
Multiple conditions can cause wrist and forearm pain; the most common are de Quervain tenosynovitis and thumb carp metacarpal arthritis. Intersection syndrome (tenosynovitis of the radial wrist extensors) is common cause of wrist pain but under diagnosed, because of an atypical presentation of symptoms or because of a rarely unrecognized entity. It is a non-infectious inflammatory pathology located at the crossing point between the first and the second dorsal compartment muscles and the radial wrist extensor muscles. Its incidence is reported to be between 0,2% and 0,37% [1]. Patients with intersection syndrome complain of radial wrist or forearm pain. Symptoms may be exacerbated by repetitive wrist flexion and extension. The diagnosis is often made clinically but may also be found thanks to sonography and MRI.

Patient and observation
A 60-year-old man was admitted to our hospital suffering from pain and swelling on the dorsal forearm, 3 cm from the wrist (Figure 1).
He sometimes feels a local crepitation while moving his thumb. The ultrasonographic and MRI exploration of the radial forearm (

Discussion
The intersection syndrome was described for the first time in 1841 by Velpeau, and it is also referred as adventitial bursitis, subcutaneous perimyositis, Abductor pollicislongus syndrome, peritendinitiscrepitans, cross-over syndrome, and oarsmen's wrist [2]. Yet most authors, believing that these names misstate the pathologic abnormality, prefer intersection syndrome. This term makes a clear statement about the location of the physical findings without being mislead about the pathologic anatomy [3].
It is common cause of wrist pain but under diagnosed, because of an atypical presentation of symptoms or because of a rarely unrecognized entity. It is a non-infectious inflammatory pathology located at the crossing point between the first and the second dorsal compartment muscles and the radial wrist extensor muscles [1]. There is no consensus about the pathophysiology of this condition, but this syndrome usually develops in patients involved in activities, such as rowing, canoeing, playing racket sports, horseback riding, and skiing, or occupations that require repetitive forceful flexion and extension of the wrist [3]. The prevalence of intersection syndrome was found to be 0.37%, in a study looking at 8,000 patients who presented with arm or hand pain in Thailand. In the general population, the prevalence varies between 0.20% and 0.37%.Another study by Palmer, looking at wrist injuries related to helicopter skiing in the Bugaboo mountains of British Columbia, suggested an incidence of intersection syndrome of 21% in that population of skiers [1].
At first we should define the proximal intersection syndrome, and principally a peritendinous phenomenon [3].
The treatment is similar to the one given for overuse injuries.
Conservative measures are the first line of treatment. Symptoms resolve within 2 to 3 weeks for 60% of patients with rest, administration of non-steroidanti-inflammatory drugs, and splinting.
Surgery is indicated typically only for patients not responding to therapy. When conservative treatment fails, a tenosynovectomy and a fasciotomy of abductor pollicislongus can be performed.

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 (US and MRI).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.

Competing interests
The authors declare no competing interests.

Authors' contributions
All the authors contributed to the writing of the manuscript. They have read and approved the final version of the manuscript.