A 45 year old woman, presenting with the history of diplopia and dysphagia worsening as the day progresses, can be diagnosed to have: (AIIMS Nov 2010)
Disorders Of The Neuromuscular Junction (Myasthenia gravis)
1). Etiology. Antibodies directed against the acetylcholine receptor on the motor end plate cause an increased rate of receptor destruction and lead to weakness.
2). Clinical signs. Patients are often young women or older men.
a. Complaints of fatigue in the evening time, double vision, difficulty swallowing and speaking, and limb weakness are common, snarling face appearance. Deep tendon reflexes are normal.
b. On examination, ptosis, bilateral eye movement abnormalities, and proximal weakness may be seen. Cranial nerve involved are 3, 4, 6, 9, 10, 12).
c. Bulbar palsy is common in MuSK antibody positive MG.
d. In MG
i. Pupillary & accommodation reactions are normal
ii. Proptosis is not feature.
e. A thymoma is present in 10%-25% of cases.
f. CPK levels are typically normal.
Extra Edge: Cranial nerve which is not involve is 5th Nerve.
Cogan’s Lid Twitch sign - pt. looks down for 10-20 seconds and then rapidly looks upto primary position, the upper lids often overshoot (retract) and then settle back into a stable position or drift downward. This sign demonstrate fatigability (Fluctuating weakness), which is characteristic of myasthenia.
Useful clinical Tests to assess the effect of treatment.
1). Forward arm abduction
2). Range of eye movement
4). Time of development of ptosis on upward eye movement