Congenital abducens-oculomotor dysinnervation: A novel congenital cranial dysinnervation disorder phenotype

In a boy aged 6 years left unilateral congenital ptosis with medial rectus-levator palpebrae superioris (MR-LPS) synkinesis; the coexisting hitherto unreported likely lateral rectus-superior rectus (LR-SR) dysinnervation is reported. Ocular movements were full and cover test did not reveal any ocular misalignment. Such a presentation can only arise from two concurrent dysinnervations: first one between inferior and superior divisions of third nerve and second one between third and sixth cranial nerve. The dysinnervation may conform to a forme-fruste TUBB3 (Tubulin, Beta 3 Class III Gene) pathogenic variant phenotype and may be classed as a novel congenital cranial dysinnervation disorder (CCDD).