Ptosis refers to drooping of eyelids. Ptosis occurs due to weakness of levator palpebrae superioris, the muscle responsible for eyelid elevation. Ptosis can occur due to a variety of causes, including nuclear, infranuclear and supranuclear causes.
The commonest causes of ptosis are infranuclear due to involvement of oculomotor nerve (3rd nerve palsy), the LPS muscle itself (muscular dystrophy, mechanical ptosis, etc), neuromuscular junction disorders (myasthenia gravis). Horner’s syndrome due to involvement of sympathetic nerve fibres can also cause ptosis.
Nuclear lesion due to midbrain disease causes bilateral ptosis. This is because central caudal subnucleus subserves LPS of both sides.
Supranuclear lesions causing ptosis is not common. However, ptosis has previously been described in cases of hemispheric strokes. Bilateral ptosis was found more commonly with right hemispheric strokes (as compared to left hemispheric strokes). In another cases, bilateral ptosis with restriction of vertical upward gaze was found in a case of right putaminal hemorrhage. Another report suggested that bilateral ptosis in an otherwise alert patient with hemispheric stroke could suggesting an impending herniation.
Our patient, a 59-year old man, known diabetic and hypertensive, presented with acute onset let hemiplegia and bilateral ptosis. Extraocular movements were normal and he was fully alert. CT scan showed a large infarct in right MCA territory. He was conservatively managed and did not require decompressive hemicraniectomy.
Salient features of cerebral ptosis
- Cerebral ptosis is usually bilateral.
- Ptosis is of sudden onset and there is no diurnal variation.
- Patient is usually alert and fully conscious.
- Extraocular movements are normal, however, there may be restriction of upward gaze in some cases.
- Bilateral cerebral ptosis is most commonly seen with right hemispheric strokes (ischemic or hemorrhagic).
- Cerebral ptosis is transient and recovery starts within four days of onset. Most patients completely recover within 10 days.
- Cerebral ptosis expresses the inhibition of the voluntary eyelid elevation center, of prefrontal location in the non-dominant hemisphere.