Alcohol Abuse and Horizontal Gaze Nystagmus (HGN): What You Need to Know

Yes, acute alcohol intoxication causes horizontal gaze nystagmus (HGN). HGN is an involuntary, jerk-type oscillation of the eyes during lateral gaze.

Mechanism

Alcohol suppresses the inhibitory influence of the lateral vestibular nucleus on the medial longitudinal fasciculus (MLF). The MLF coordinates conjugate eye movements via the abducens (CN VI) and oculomotor (CN III) nuclei. Disinhibition → velocity-storage mismatch → jerk nystagmus (fast phase toward gaze direction).

Clinical/Legal Use

• Standardized Field Sobriety Test (SFST): HGN is the most reliable component (88% sensitivity at 0.08% BAC).
• Officer checks: smooth pursuit, distinct nystagmus at max deviation, onset prior to 45°.
• Not specific to alcohol (also: sedatives, PCP, vestibular lesions, congenital).

Chronic Alcoholism

May cause gaze-evoked nystagmus from cerebellar degeneration (flocculus/vestibular nuclei), not acute HGN.

HGN resolves as BAC falls. It is a sign of acute cerebellar/vestibular dysfunction, not permanent damage (unless chronic).