Also called 6th cranial<unk>  (CN VI) or abducens<unk><unk> 
Most common ocular<unk><unk> 
Innervates the ipsilateral lateral rectus muscle controlling eye abduction
Esotropia (eye moves inward) of the affected eye due to the unopposed action of the medial rectus muscle, innervated by the oculomotor<unk>  (CN III) 
Nuclear lesion
Congenital, demyelinating, ischemia, traumatic
Inflammatory
Vasculitis
Sarcoidosis
Systemic lupus erythematosus
Infectious
Lyme disease
Syphilis 
Tuberculosis
Meningitis 
Orbital lesions
Neoplastic
Inflammatory
Infectious
Congenital, demyelinating, ischemia, traumatic
Vasculitis
Sarcoidosis
Systemic lupus erythematosus
Lyme disease
Syphilis 
Tuberculosis
Meningitis
Neoplastic
Inflammatory
Infectious
Sixth nerve palsy
Increased intracranial pressure 
Third nerve palsy
Vascular: Aneurysm, central venous sinus thrombosis
Fourth nerve palsy
Inflammatory: Post-viral, demyelinating, sarcoidosis, giant cell arteritis, Miller-Fisher Syndrome variant of Guillian-Barre Syndrome
Ulnar neuropathy
Neoplastic: Lesions in the cerebellopontine angle. In children – pontine glioma