Differential Diagnosis in Lateral Rectus Palsy

Differential Diagnosis in Lateral Rectus Palsy/Abducens Palsy

CN VI (Abducens Nerve)Longest subarachoid courseRuns from brainstem in posterior fossa, through middle fossa (especially the petrous apex) and orbitLesions can affect the nerve via:

VI1: the brainstem syndrome

VI2: the elevated intracranial pressure syndromeVI3: the petrous apex syndrome

VI4: the cavernous sinus syndrome

VI5: the orbital syndrome

Anatomical ConcernsCourse of the Abducens Nerve

Brainstem Sources of Abducens PalsyMillard Gubler Syndrome

A unilateral lesion of the ventrocaudal pons may involve the basis pontis and the fascicles of cranial nerves VI and VII. Symptoms include:1.Contralateral hemiplegia (sparing the face) due to pyramidal tract involvement2.Ipsilateral lateral rectus palsy with diplopia that is accentuated when the patient looks toward the lesion, due to cranial nerve VI involvement.3.Ipsilateral peripheral facial paresis, due to cranial nerve VII involvement.

Millard Gubler Syndrome

Foville Syndrome: Inferior Medial Pontine Syndrome (Foville Syndrome) Fovilles syndrome:Sixth nerve paresisHorizontal conjugate gaze palsyIpsilateral V, VII, VIII cranial nerve palsyIpsilateral Horners syndrome

Foville SyndromeIpsi PPRF --> Horizontal Gaze palsy Ipsi CNVII --> LMN facial paresis contra UMN paralysis of body contra sensory loss of body internuclear opthalmoplegia

Anatomical Consideration of the Petrous Apex

Petrous Apex Syndrome (Grandenigos Syndrome)retroorbital pain due to pain in the area supplied by the ophthalmic branch of the trigeminal nerve (fifth cranial nerve),abducens nerve palsy (sixth cranial nerve),[3] andotitis media

Intracranial Abducens

Dorello canal channels the abducens nerve (CN VI) from the pontine cistern to the cavernous sinus

Increased Intracranial PressureBrainstem displacement inferiorlyDiffuse pressure along the subarachnoid courseTraction on CN VI while it is anchored in Dorellos canal

Diplopia--> Horizontal

Extracranial course of CN VINote the Abducens in within the cavernous sinus while the CNIII, V1, V2 and Trochlear nerves are in the wall

CN VI exists the eye at the superior orbital fissure

Superior Orbital Fissure

LearnFaunaToSeeNumerousInvertebrate Animals

In adults, the most likely etiology of isolated sixth nerve palsy is ischemic mononeuropathy that may be due to diabetes mellitus, arteriosclerosis, hypertension, temporal arteritis or anemiaIsolated 6th Nerve Palsy

Six Mimics of a CN VI Palsy Thyroid eye diseases

Myasthenia gravis

Duanes syndrome

Spasm of the near reflex

Delayed break in fusion

Old blowout fracture of the orbit

Duanes Retraction SyndromeDefect in genesis of Abducens nucleusThree componentsDefect AB ductionSome defect in AD ductionPalpebral fissue narrowing and globe retraction often with upshoot