Double Depressor Palsy

Question 1

What deviation and features will be present in a double depressor palsy

Answer 1

(SO + IR, 3rd + 4th ? Cavernous sinus)
The affected eye is hypertrophic and may cause over-elevation in adduction and abduction
may also have chin depression if bilateral

Question 2

Aetiology : double depressor palsy

Answer 2

Double Depressor Palsy’s are rare
Usually congenital absence of that muscle in which the spread of concomitance has resulted in limitation of down-gaze in both adduction and abduction
Acquired double depressor palsy is usually caused by cerebrovascular disease affecting the pons or cerebellum

Question 3

diff dx: double depressor palsy

Answer 3

Traumatic orbital blow-out fracture with associated IR paresis or entrapment
TED with SR contracture
skew deviation
myasthenia gravis
Previous strabismus surgery with excessive recession of the IR, a large resection of the SR, or scar tissue formation may cause diminished downgaze.

Question 4

features of double depressor palsy

Answer 4

Initially Inferior Rectus Palsy with concomitance spreading to limitation of down gaze in both adduction and abduction
The FDT on down-gaze may indicate mechanical restriction from secondary contracture of the ipsilateral superior rectus muscle
When the unaffected eye fixes, the paretic eye may have upper eye lid retraction
Pseudoptosis may occur on attempted downgaze when the paretic eye does not depress, but the lids lower bilaterally, and pseudoptosis of the non-involved eye may also occur when patient fixates with involved eye (right eye) in primary gaze.
Vestibulo–ocular reflexes (doll’s head maneuvers) are usually intact on downgaze, indicating a supranuclear etiology with preservation of the nuclear reflexes.

Supranuclear lesions affect the saccadic, smooth pursuit, optokinetic, or vergence inputs in the brainstem, whereas nuclear–infranuclear lesions affect ocular motor nuclei, nerves, neuromuscular junction, or extraocular muscles themselves. The distinction can be made at the bedside by checking if the weakness can be overcome with the VOR, as elicited with head movements i.e., doll’s head.
Doll’s head intact = supranuclear?

Question 5

surgical tx double depressor palsy

Answer 5

Surgical management consists of inferior transposition of the horizontal rectus muscles (inverse Knapp procedure) combined with a recession of the ipsilateral superior rectus muscle if the FDT indicates mechanical restriction on down-gaze.