Duane syndrome

Duane syndrome, also known as Duane retraction syndrome, is a rare congenital disease characterized by non-progressive strabismus. It is caused by a variable degree of abnormal development of one or both of the abducens nerves (CN VI).

Epidemiology

It presents during childhood and it accounts for less than 5% of cases of strabismus ¹.

Associations

• Duane-radial ray syndrome (Okihiro syndrome)

• Goldenhar syndrome

• Wildervanck syndrome

Clinical presentation

Three types of Duane syndrome are described, each with a different clinical presentation ^4,5:

• type I: most common

  • strabismus with esotropia at rest

  • head tilt to affected side

  • absent to markedly restricted abduction

  • normal to mildly restricted adduction

  • induced ptosis on adduction

• type II

  • strabismus with exotropia at rest

  • head tilt to unaffected side

  • normal to mildly restricted abduction

  • absent to markedly restricted adduction

  • induced ptosis on adduction

• type III 

  • strabismus with either esotropia or exotropia at rest

  • head tilt to the affected side

  • absent to markedly restricted abduction

  • absent to markedly restricted adduction

  • induced ptosis on adduction

The majority of cases are unilateral, but it can be bilateral in up to 20% of patients.

Pathology

Duane syndrome results from absent or abnormal development of the abducens nerve or nucleus ^4,5. Thus, the lateral rectus muscle becomes abnormally innervated by branches from the oculomotor nerve ^4,5.

Most cases (90%) are sporadic, however, a minority of cases may have a genetic bases ⁵. Pathogenic variants in the CHN1, MAFB, or SALL4 genes have been implicated in inherited forms ⁵. Syndromic associations are also present, as aforementioned.

Radiographic features

MRI

MRI findings consist of the following ^2,3:

• hypoplasia/atrophy of the lateral rectus muscle

  • the degree of atrophy is variable as the lateral rectus muscle may be reinnervated by aberrant branches from the oculomotor cranial nerve (CN III)

• hypoplasia or absence of CN VI

Hypoplasia of other extra-ocular muscles have been described, depending on the type of the disease, especially the superior oblique muscle (types I and II) ³.

Treatment and prognosis

Management can be non-surgical (e.g. wearing prisms) or surgical (e.g. correcting strabismus) ⁵.

History and etymology

The condition is named after Alexander Duane (1858-1926), American ophthalmologist, who described it in 1905 ⁶.

Differential diagnosis

• abducens nerve palsy