From the Guidelines
The peek sign in myasthenia gravis refers to the momentary improvement in ptosis when a patient is asked to look upward and then quickly returns their gaze to the primary position, which is a useful clinical examination finding to diagnose myasthenia gravis, particularly in patients with ocular symptoms. This brief improvement occurs because the levator palpebrae muscle receives a burst of neural stimulation during the downward movement of the eye, temporarily overcoming the neuromuscular junction defect characteristic of myasthenia gravis 1. To elicit this sign, ask the patient to look up at a fixed point for about 15-20 seconds, which fatigues the already compromised muscle, and then have them quickly return their gaze to the primary position. Watch carefully for a momentary improvement in the ptosis before it returns. The peek sign is an important diagnostic tool, as myasthenia gravis involves antibodies that block acetylcholine receptors at the neuromuscular junction, leading to muscle fatigue and weakness, but the muscle can briefly overcome this blockade with the strong neural impulse generated during the change in gaze direction.
Clinical Significance
The peek sign is a valuable clinical examination finding that can help diagnose myasthenia gravis, particularly in patients with ocular symptoms such as ptosis and diplopia. According to recent guidelines, treatment of myasthenia gravis is goal-directed and targeted outcomes may include recognition of the disease, prevention of morbidity and mortality, reduction of diplopia, and restoration of normal ocular alignment and binocular function 1. The peek sign can be an important tool in achieving these outcomes by facilitating early diagnosis and treatment.
Diagnostic Approach
To diagnose myasthenia gravis, a comprehensive clinical examination should be performed, including assessment of ocular symptoms such as ptosis and diplopia. The peek sign can be elicited by asking the patient to look up at a fixed point for about 15-20 seconds and then quickly return their gaze to the primary position. A momentary improvement in ptosis suggests the presence of myasthenia gravis. Further diagnostic testing, such as electromyography and acetylcholine receptor antibody testing, may be necessary to confirm the diagnosis.
Treatment Implications
The diagnosis of myasthenia gravis has significant implications for treatment, as patients may require immunosuppressive therapy, such as corticosteroids or azathioprine, to manage their symptoms 1. In some cases, thymectomy may be indicated, particularly in patients with thymoma. The peek sign can be an important tool in monitoring the response to treatment and adjusting the treatment plan as needed.
From the Research
Definition and Characteristics of Myasthenia Gravis (MG)
- Myasthenia Gravis (MG) is a chronic autoimmune disorder of the neuromuscular junction, characterized clinically by muscle weakness and abnormal fatigability on exertion 2.
- MG is associated with circulating antibodies to AChR, modification of the synaptic cleft, and destruction of the postsynaptic neuromuscular membrane 3.
- The hallmark of MG is fluctuating muscular weakness and fatigability of muscles on sustained repeated activity 3.
Treatment of Myasthenia Gravis
- Available therapies for MG include oral acetylcholinesterase (AChE) inhibitors for symptomatic treatment, and short- and long-term disease-modifying treatments 2.
- Pyridostigmine is the most commonly used AChE inhibitor and is recommended as first-line therapy for MG 2.
- Immunomodulating agents, such as corticosteroids, azathioprine, cyclosporine A, and cyclophosphene, are also used in the treatment of MG 4.