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SPECIAL FORMS

DUANE'S RETRACTION SYNDROME

Duane's retraction syndrome is typically characterized by marked limitation of abduction, mild limitation of adduction, retraction of the globe and narrowing of the palpebral fissure on attempted adduction, and, frequently, upshoot or downshoot of the eye in adduction. Usually it is monocular, with the left eye more often affected. Most cases are sporadic, although some families with dominant inheritance have been described. A variety of other anomalies may be associated, such as dysplasia of the iris stroma, heterochromia, cataract, choroidal coloboma, microphthalmos, Goldenhar's syndrome, Klippel-Feil syndrome, cleft palate, and anomalies of the face, ear, or extremities. The causes of the motility defects are varied, and some anomalies of muscle structure have been found. Most cases can be explained by inappropriate innervation to the lateral rectus and sometimes to other muscles as well. Sherrington's law of reciprocal innervation is not obeyed, because nerve fibers to the medial rectus may also go to the lateral rectus. This accounts for simultaneous contraction of the medial and lateral rectus muscles (co-contraction), causing retraction of the globe. Cases with proved absence of the abducens nucleus and nerve have been documented.

Treatment

Only when a primary position misalignment or a significant compensatory head turn exists is surgical treatment indicated. The goal is to obtain straight eyes in the primary position and to horizontally expand the field of single vision. Recession of the medial rectus on the affected side is performed if any esotropia is present in the primary position. For more severe cases, temporal transposition of the vertical rectus muscles accompanied by weakening of the medial rectus muscle, either by adjustable recession or botulinum toxin A, is often indicated.

DISSOCIATED VERTICAL DEVIATION

Dissociated vertical deviation is frequently associated with congenital esotropia and rarely with an otherwise normal muscle balance. The exact cause is not known, though it is logical to assume it is from faulty supranuclear innervation of extraocular muscles.

Clinical Findings

Each eye drifts upward under cover, frequently with extorsion and a small exotropic shift, and then returns to its resting binocular position when the cover is removed. Occasionally, the upward drifting will occur spontaneously, causing a noticeable vertical misalignment. Most cases are bilateral, though asymmetry of involvement is common. There are usually no symptoms.

Treatment

Treatment is indicated if the frequency of the intermittent manifest vertical deviation is unacceptable. Nonsurgical treatment is limited to refractive correction to maximize the potential of motor fusion and therapy for amblyopia. Surgical results have been variable and can be disappointing. Currently, the most popular and successful procedures are very large recession of the superior rectus or recession of the superior rectus combined with the Faden procedure. A new procedure that involves transposing anteriorly the insertion of the inferior oblique muscle has also been effective.

BROWN'S SYNDROME (Superior Oblique Tendon Sheath Syndrome)

Brown's syndrome is due to fibrous adhesions in the superior nasal quadrant involving the superior oblique tendon and trochlea, which mechanically limit elevation of the eye. Limitation of elevation is most marked in the adducted position, and improvement in elevation occurs gradually as the eye is abducted. Differential diagnosis is concerned mainly with paresis of the inferior oblique muscle. Forced duction testing is diagnostic, since there is an upward restriction to elevation in adduction when Brown's syndrome is present. The condition is usually unilateral and idiopathic, though rarely it may be due to trauma or inflammation.

Surgical treatment is limited to those cases where there is an abnormal head position to compensate for hypotropia or cyclotropia of the involved eye. The objective is to free the mechanical adhesions and weaken the superior oblique muscle. Although controversial as to its timing, weakening of the ipsilateral inferior oblique may compensate for the induced fourth nerve palsy. Normalization of the head position may occur, but restoration of full motility is seldom achieved.

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