A mnemonic to remember the nerve supply to the extraocular muscles:
- LR6SO4O3 (mock 'chemical formula')
The letters represent the extraocular muscles and numbers represent their respective cranial nerve supply:
- LR6: lateral rectus, innervated by the 6th (abducens) nerve
- SO4: superior oblique, innervated by the 4th (trochlear) nerve
- O3: other muscles (superior, inferior, medial recti and inferior oblique), innervated by the 3 rd (oculomotor) nerve
The nerves enter the ocular surface of the respective muscles. The trochlear nucleus of one side supplies the superior oblique of the contralateral side due to decussation of fibers of the trochlear nerve in the midbrain.