Paralytic Strabismus: Third, Fourth, and Sixth Nerve Palsy

Paralytic Strabismus 825
Mobius syndrome describes congenital facial diplegia that is frequently associated
with sixth nerve palsy (Fig. 17). 74 Conjugate gaze paresis may be present, typically in
cases with more severe abduction deficit. Other abnormalities such as complete
external ophthalmoplegia, third nerve palsy, or ptosis occur less frequently. The cause
of these deficits is believed to be hypoplasia of the relevant brainstem structures.
Other inflammatory, infectious, and neoplastic processes that may affect the sixth
nerve in the subarachnoid space are the same as those that can cause third and fourth
nerve palsies and other cranial nerve deficits, and are discussed later.
Diagnostic Testing
Many patients with acute sixth nerve palsy require MRI to exclude structural, inflammatory,
or neoplastic causes. All children and young adults with sixth nerve palsy
should undergo imaging because of a higher prevalence of tumors and demyelinating
Fig. 22. A 75-year-old man with right CCF who presented with several months of left retroorbital
headache and 2 days of horizontal binocular diplopia. (A) Slight esotropia in primary
gaze. (B) Normal right gaze. (C) Limited left abduction. (D) CT angiogram revealed dilation
and tortuosity of the right superior ophthalmic vein (arrow). Catheter angiography revealed
a cavernous sinus dural arteriovenous fistula (type D indirect CCF) supplied by bilateral internal
and external carotid artery branches (arrow) with dominant venous drainage through the
right superior ophthalmic vein. The right external carotid supply (via an accessory meningeal
artery) was successfully embolized with Onyx 18. Other supplying branches were not
amenable to embolization.