Superior oblique tendon sheath syndrome. An electromyographical study.

The superior oblique tendon sheath syndrome was first described by Brown (I950), who noted that many cases of apparent congenital paresis of the inferior oblique muscle had restricted elevation in adduction on passive duction testing. At operation he observed thickening of the anterior part of the superior oblique tendon sheath, and whern this was stripped away a full range of passive movements was possible. Several reports have since appeared in the literature confirming these initial findings (Nutt, I955; Girard, I956; Folk, I957; Esterly, Nadbath, and Russell, I960). Spontaneous recovery was recorded by Costenbader and Albert (1958) and Lowe (I969). Impeded elevation in adduction was found to be associated in some cases with an audible click by Mein (I964) and Sandford-Smith (I969), who suggested local thickening of the superior oblique tendon as the causative factor. Electromyography of the inferior oblique muscles in this syndrome revealed normal firing patterns (Breinin, 1957), but a further investigation of both oblique muscles of the affected side showed discharges indicative of an innervation disorder (Stein and Papst, I968). Because of these conflicting opinions concerning the aetiology of this condition the authors carried out electromyography (EMG) on three adult patients with the superior oblique tendon sheath syndrome, and the results are reported below.