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Abducens Nerve

nervus abducens (CN VI)

The abducens nerve has the longest intracranial course of any cranial nerve, making it the most frequently involved nerve in raised intracranial pressure as it is stretched over the petrous apex. Because it supplies only the lateral rectus muscle, its palsy produces a convergent squint (esotropia) with inability to abduct the affected eye — the patient reports horizontal diplopia that worsens on gaze toward the affected side.

Region: Head & Skull

Anatomical Data

Origin, Insertion & Supply

Origin	Abducens nucleus in the caudal pons (near the facial nerve genu — explaining combined CN VI and VII palsies in pontine lesions)

Clinical Relevance

Clinical Notes

A unilateral CN VI palsy is a false localising sign in raised intracranial pressure because the stretched nerve produces a palsy that does not localise the responsible lesion to the abducens nucleus. True pontine CN VI lesions involve the ipsilateral facial nerve genu producing combined CN VI and CN VII palsies. Cavernous sinus pathology (thrombosis, tumour, aneurysm) typically involves multiple cranial nerves including III, IV, V1, V2, and VI producing painful ophthalmoplegia.

Pathology

Common Injuries & Conditions

Abducens Nerve Palsy

Lateral rectus paralysis producing convergent squint and horizontal diplopia from raised ICP, cavernous sinus pathology, or pontine lesion, managed by treating the underlying cause with prism glasses for persistent diplopia.