Oculomotor synkinesis

Oculomotor synkinesis (aberrant regeneration of the oculomotor nerve) is a regenerative phenomenon of the third cranial nerve that occurs as a result of both misdirection of sprouting axons and of ephaptic transmission - cross-talk between axons without covering sheaths. Features are variable and may include:

• lid elevation on attempted downgaze - levator palpebrae superioris fires as inferior rectus fires
• adduction on attempted up gaze - medial rectus fires as superior rectus fires
• retraction on attempted up gaze - recti act as retractors and fire together
• pseudo-Argyll Robertson pupil - pupil constricts when eye is adducted - pupillary innervation from medial rectus
• pseudo-Von Graefe's sign - no lid lag on downgaze but lid retraction due to innervation of levator palpebrae superioris from fibres distributed to inferior rectus
• monocular vertical optokinetic nystagmus response

Reference:

1. Weber E. Aberrant regeneration of the oculomotor nerve: implications for neurosurgeons. Neurosurg Focus. 2007;23(5):E14.