From the Guidelines
Cogan lid twitch sign is a clinical finding characterized by a brief upward twitch of the upper eyelid when the patient shifts their gaze from a downward position back to primary position, often associated with myasthenia gravis, as noted in the adult strabismus preferred practice pattern 1. This sign is most commonly associated with myasthenia gravis, an autoimmune neuromuscular disorder that causes muscle weakness.
- The lid twitch occurs because the levator palpebrae superioris muscle, which raises the upper eyelid, briefly contracts excessively before weakening again.
- To properly elicit this sign, ask the patient to look downward for about 15-20 seconds and then quickly return their gaze to the primary position while you observe their upper eyelids.
- The sign is considered positive if you see a momentary overshoot or twitch of the upper eyelid before it settles or begins to droop. While Cogan lid twitch is not pathognomonic for myasthenia gravis, it is a useful clinical tool that should prompt further investigation, including acetylcholine receptor antibody testing, repetitive nerve stimulation studies, or single-fiber electromyography 1. The physiological basis for this sign relates to the brief recovery of neuromuscular transmission that occurs when the affected muscles are briefly rested in the downward gaze position, followed by fatigue when sustained contraction is again required.
- A complete sensorimotor examination and external examination is critical, with attention to the presence of strabismus, which changes over the course of prolonged examination, and variable ptosis with possible Cogan lid-twitch sign, and slow saccades 1.
From the Research
Definition and Purpose of the Cogan Lid Twitch Sign
- The Cogan lid twitch sign is a clinical test used to assess for myasthenia gravis, particularly in patients with unexplained ptosis 2.
- It is characterized by a brief upward twitch of the upper eyelid when the patient looks straight ahead after looking up and down 3.
Sensitivity and Specificity
- The sensitivity and specificity of the Cogan lid twitch sign have been found to be relatively low in some studies, with other conditions also causing a lid twitch 2.
- However, another study found the Cogan lid twitch test to be a specific and sensitive test for myasthenia gravis, with a specificity of 99% and a sensitivity of 75% 3.
Clinical Application
- The Cogan lid twitch sign is often used in conjunction with other clinical tests, such as the lid fatigability test and forced eyelids closure test, to evaluate for ocular myasthenia gravis 4.
- It has been found to be a reliable test, particularly when performed by neuro-ophthalmologists, with moderate-to-substantial interobserver reliability 4.
Association with Myasthenia Gravis
- The presence of a Cogan lid twitch may increase suspicion of myasthenia gravis, but it is not diagnostic and does not exclude other etiologies of ptosis 2, 5.
- The Cogan lid twitch sign has been observed in patients with ocular myasthenia gravis, and its presence can be an important diagnostic clue 5, 6.