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298 Clinical Pathways in Neuro-Ophthalmology, second edition
Table 13–3. The Localization of Abducens Nerve Lesions
Structure Involved Clinical Presentation
Nuclear lesions
Abducens nucleus Horizontal gaze palsy
Möbius syndrome (gaze palsy with facial diplegia)
Duane’s retraction syndrome (gaze palsy with globe
retraction and narrowing of palpebral fissure with
adduction)
Dorsolateral pons Ipsilateral gaze palsy, facial paresis, dysmetria;
occasionally with contralateral hemiparesis (Foville
syndrome)
Lesions of the abducens fascicle
Abducens fascicle Isolated CN VI palsy
Anterior paramedial pons Ipsilateral CN VI palsy, ipsilateral CN VII palsy,
contralateral hemiparesis (Millard-Gubler)
Prepontine cistern May have contralateral hemiparesis
Lesion of abducens nerve (subarachnoid, petrous)
Petrous apex (Dorello’s canal) CN VI palsy, deafness, facial (especially retro-orbital) pain
(Gradenigo)
Cavernous sinus Isolated CN VI palsy; CN VI palsy plus Horner’s
syndrome; also may affect CN III, IV, VI
Superior orbital fissure syndrome CN VI palsy with variable affection of CN III, IV, VI;
proptosis
Orbit CN VI palsy; visual loss; variable proptosis, chemosis, lid
swelling
Source: Modified from Brazis, 2001, with permission from Lippincott Williams & Wilkins.
Is the SNP Due to a Subarachnoid Space
Lesion?
Lesions of the subarachnoid space may result in unilateral or bilateral SNP. This SNP is
a nonlocalizing finding because any cause of increased intracranial pressure may result
in an SNP (see Table 13–3). Patients with a subarachnoid space lesion should undergo
neuroimaging directed to this location followed by a lumbar puncture (LP) as needed
(class III–IV, level B).
Is the SNP the Result of a Lesion of the
Petrous Apex?
Lesions of the petrous apex causing SNP are associated with other neurologic findings,
including involvement of other cranial nerves (e.g., fifth, seventh, and eighth) or facial
pain. Neuroimaging should be directed toward the petrous apex (MRI or computed
tomography [CT] for bone involvement) (class III–IV, level B).