Eye movements in Locked-in Syndrome

Q: In Locked-in syndrome, which of the eye movements remain intact? - select one

A) Horizontal

B) Vertical

Answer: B

Focal injury to the base of the pons, usually caused by embolic occlusion of the basilar artery, means the patient cannot move muscles in the limbs, trunk, or face.The only viable and intact function left is voluntary blinking and vertical eye movements. 

Horizontal eye movements are usually impaired due to damage to the paramedian pontine reticular formation (PPRF). In fact, early smooth horizontal eye movement is considered a favorable prognostic sign in locked-in syndrome.

#neurology

References:

1. Schnetzer L, McCoy M, Bergmann J, Kunz A, Leis S, Trinka E. Locked-in syndrome revisited. Ther Adv Neurol Disord. 2023 Mar 29;16:17562864231160873. doi: 10.1177/17562864231160873. PMID: 37006459; PMCID: PMC10064471.

2. Yang CC, Lieberman JS, Hong CZ. Early smooth horizontal eye movement: a favorable prognostic sign in patients with locked-in syndrome. Arch Phys Med Rehabil. 1989 Mar;70(3):230-2. PMID: 2923543.

3. Smith E, Delargy M. Locked-in syndrome. BMJ. 2005 Feb 19;330(7488):406-9. doi: 10.1136/bmj.330.7488.406. PMID: 15718541; PMCID: PMC549115.