The möbius sequence: a relook

The constellations of findings often referred to as Mobius syndrome might be better described as Mobius sequence, because the term sequence defines a cascade of secondary events after an embryonic insult from heterogeneous causes. Classic clinical findings include evidence of sixth and seventh cranial nerve involvement, often with associated malformations of limbs, craniofacial structures, and other cranial nerves.

A prospective study was undertaken in Sweden of 25 patients who showed characteristic findings of Mobius sequence.

Of the patients who did not have strabismus surgery, 10 patients had straight eyes in the primary position, 7 had esotropia, 2 had exotropia, and 1 had hypertropia. All had significant limitation of abduction, except 1 patient with exotropia who showed minimal underaction on abduction but a large limitation of adduction. In the description in these early cases, some patients manifested a clinical pattern resembling a horizontal gaze paresis. Narrowing of the palpebral fissure on adduction similar to that seen in Duane syndrome was observed in a few cases. Two patients had ptosis. Nineteen patients had diminished facial expression bilaterally, often asymmetric, and 6 cases appeared to be unilateral. Seven patients had abnormal tearing. Associated systemic findings included Poland anomaly (2), club feet or other limb anomalies (8), micrognathia (8), tongue malformations (17), cleft palate (5), and speech problems (18). An unusual finding was autism syndrome (6) or autism-like syndrome (1).

The associated findings in Mobius sequence may give further clues to the location and timing of the developmental disturbance. The wide range of ocular motility patterns suggests that the previous concept of a lesion solely in the sixth nerve nucleus is an inadequate explanation for these findings.