Ptosis is a significant physical finding in the MRCP PACES examination. When you notice ptosis, it is essential to conduct a thorough assessment by considering the following factors:
Ptosis, or drooping of the upper eyelid, is a significant clinical finding in various medical examinations, including the MRCP PACES. It can result from a variety of underlying conditions affecting the muscles, nerves, or anatomical structures of the eyelid. Understanding the causes and implications of ptosis is essential for accurate diagnosis and management.
A comprehensive examination is crucial for determining the underlying cause of ptosis. Key aspects to assess include:
Type of Ptosis | Causes |
Unilateral | 3rd Cranial Nerve Palsy, Horner Syndrome, Myasthenia Gravis, Congenital |
Bilateral | Myasthenia Gravis, Myotonic Dystrophy, Tabes Dorsalis, Bilateral Horner Syndrome, Oculopharyngeal Muscular Dystrophy, Chronic Progressive External Ophthalmoplegia, Nuclear Third Nerve Palsy |
Myasthenia gravis (MG) is characterized by various ocular signs that can aid in diagnosis. Below are key eye signs associated with MG:
Cogan’s lid twitch is a phenomenon observed in patients with myasthenia gravis. After the patient looks down for a short period, the upper eyelid may overshoot when they return to the primary position, appearing slightly retracted for an instant. This sign indicates fatigability of the levator muscle and is a classic finding in MG.
Lid hopping refers to the fluttering of the ptotic eyelid during eye movements. This sign is indicative of the weakness of the extraocular muscles and can be observed when the patient attempts to move their eyes. It highlights the variable muscle strength in patients with MG.
The myasthenic snarl is a characteristic facial expression seen in patients with MG. When asked to smile, the patient may exhibit contraction of the middle portion of the upper lip, while the corners of the mouth fail to contract. This sign reflects the weakness of the facial muscles and is often associated with bulbar involvement.
The curtain sign is observed when there is enhanced ptosis in one eyelid after manually elevating the more affected lid. According to Hering’s law of reciprocal innervation, both eyelids receive equal innervation. In MG, the less affected lid may open wider when the more affected lid is elevated, leading to increased ptosis in the previously less affected lid. This sign is significant in demonstrating the asymmetrical involvement of extraocular muscles in MG.
Patients with myasthenia gravis often furrow their foreheads as a compensatory mechanism to counteract ptosis. This is achieved by utilizing the frontalis muscle to elevate the eyebrows and improve the visual field. The presence of forehead furrowing can indicate the severity of ptosis and the patient’s effort to compensate for muscle weakness.
In MG, weakness of the extraocular muscles can lead to a condition known as pseudo INO. This occurs when there is asymmetrical weakness affecting more than one extraocular muscle, particularly the medial and lateral rectus muscles. The result is a characteristic eye movement abnormality that mimics true INO but is due to muscle fatigue rather than a central nervous system lesion.
Inter-saccadic fatigue refers to the slowing of saccadic eye movements due to fatigability. Patients may experience difficulty maintaining rapid eye movements, leading to a noticeable delay or reduction in the speed of saccades. This sign is indicative of the neuromuscular transmission defect seen in MG.
The peek sign is observed when the eyes drift open, revealing the sclera during an attempted eye closure. This sign indicates weakness of the orbicularis oculi muscle, which is responsible for closing the eyelids. The presence of the peek sign can be a helpful diagnostic clue in assessing ocular involvement in MG.
