Periodic Alternating Gaze (PAG) on Physical Exam Periodic Alternating Gaze (PAG) is an involuntary continuous cyclic horizontal sustained conjugate deviation of the eyes, which alternates sides with a cycle of 1–2 min. Periodic alternating nystagmus (PAN) is a spontaneous horizontal nystagmus that periodically reverses every 1–2 min, with fast phases alternating between left and right sides, separated by null phases. PAG & PAN are rarely seen together. However, PAG and PAN share a similar time constant and a common pathological mechanism (instability of the velocity‑storage mechanism [VSM]) of the cerebellum. The VSM is like a wind up clock that stores rotational information beyond the capacity of the semicircular canals and releases it after prolonged rotation. Dr. Boby Varkey Maramattom @bobvarkey #PAG #Periodic #Alternating #Gaze #neurology #clinical #video #physicalexam #ocular #ophthalmology #eyes
