By: Varsha Kumari
INTRODUCTION:
Abducens nerve is the sixth paired cranial nerve, purely motor in function. It is one of the 3 nerves responsible for controlling extraocular eye movements along with the oculomotor and trochlear nerve (Nguyen et al., 2022).
STRUCTURE AND FUNCTION:
The abducens nerve (cranial nerve VI) originates from the pons, close to the facial nerve (CN VII). It exits the brainstem at the junction of pons and medulla and enters the subarachnoid space, travelling along a part of the skull base known as the clivus. From there, it continues toward the petrous apex of the temporal bone, eventually reaching the cavernous sinus. Inside the cavernous sinus, the abducens nerve is located medial to the internal carotid artery and exits the sinus through the superior orbital fissure to enter the orbit, where it supplies the lateral rectus muscle, responsible for abduction (lateral movement) of the eye on the ipsilateral side (Graham et al., 2023). The abducens nerve is also indirectly involved in coordinating horizontal eye movements by facilitating innervation of the contralateral medial rectus muscle via the medial longitudinal fasciculus (MLF) (Nguyen et al., 2022).
ABDUCENS NERVE PALSY:
Abducens nerve palsy can be caused by any structural pathology or space-occupying lesion that can compress the nerve such as tumors, aneurysms, fractures, or increased intracranial pressure (ICP). Other general causes include damage to the nerve’s blood supply (diabetic neuropathy), demyelinating syndromes, infectious processes such as meningitis, or thrombophlebitis of the cavernous sinus (Graham et al., 2023).
Clinical features of abducens nerve palsy include binocular horizontal diplopia, which refers to double vision and inability to abduct the eye. It primarily affects distant vision rather than near vision. The other symptoms accompanying sixth nerve palsy depend on the underlying etiology. Patients with raised intracranial pressure present with headache, ocular pain, nausea, vomiting, and tinnitus (Abducens Nerve Palsy (Sixth Cranial Nerve Palsy): Background, Pathophysiology, Epidemiology, n.d.).
DIAGNOSIS:
Assessing a patient with abducens nerve palsy requires a detailed history and thorough clinical examination which involves visual acuity testing and ocular movements evaluation. In order to identify the underlying cause, neuroimaging (MRI being the preferred modality) is performed. If benign intracranial hypertension is suspected; Lumbar puncture is the diagnostic test of choice. Additional Laboratory investigations include HBA1C, erythrocyte sedimentation rate (ESR), antinuclear antibodies, and rheumatoid factor to screen for diabetes and vasculitis (Sixth Cranial (Abducens) Nerve Palsy – Neurologic Disorders – MSD Manual Professional Edition, n.d.; Sixth Nerve Palsy: Causes, Symptoms & Treatment, n.d.).
MANAGEMENT:
Management involves treating the underlying cause. Other options to alleviate the symptoms of abducens nerve palsy include wearing an eye patch or filter, injecting Botulinum toxin to manage misalignment, strabismus surgery to correct the esotropia and prism glasses (Sixth Nerve Palsy: Causes, Symptoms & Treatment, n.d.).
REFERENCES:
- Abducens Nerve Palsy (Sixth Cranial Nerve Palsy): Background, Pathophysiology, Epidemiology. (n.d.). Retrieved June 12, 2025, from https://emedicine.medscape.com/article/1198383-overview
- Graham, C., Gurnani, B., & Mohseni, M. (2023). Abducens Nerve Palsy. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK482177/
- Nguyen, V., Reddy, V., & Varacallo, M. A. (2022). Neuroanatomy, Cranial Nerve 6 (Abducens). StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK430711/
- Sixth Cranial (Abducens) Nerve Palsy – Neurologic Disorders – MSD Manual Professional Edition. (n.d.). Retrieved June 12, 2025, from https://www.msdmanuals.com/professional/neurologic-disorders/neuro-ophthalmologic-and-cranial-nerve-disorders/sixth-cranial-abducens-nerve-palsy#Etiology_v1042818
- Sixth Nerve Palsy: Causes, Symptoms & Treatment. (n.d.). Retrieved June 12, 2025, from https://my.clevelandclinic.org/health/diseases/sixth-nerve-palsy
