Kenneth Ricker (1935–2004) (photo)
Hans Georg Mertens (1921–2006)
Definition
"intermittent, tonic spasms of one or more of the EOM, resulting in strabismus & paroxysmal diplopia"
-delayed relaxion of EOM makes eye temporarily get 'stuck' after eccentric gaze
- AKA "locking-eye"
Etiology
-MC post-RXT of parasellar area
> 2 monhts to 18 years, mean 5y
-Others: autoimmune disorders (MG & thyroid disease)
-Rare: chemotherapy(cisplatin, 5-FU), Vit B12/D def, thorium myelography, botox injection, alcohol, and cataract surgery
Pathophysiology
-May relate to focal demyelination causing ephaptic transmission
-Eggenberger suggest “reflecting nerve circuit”
-Dysfunction of potassium channels
-Mucopolysaccharide deposition after thyroid-associated orbitopathy
Presentation
-Transient diplopia/strabismus
Neuro-exam
-Prolonged eccentric gaze (1 min)
-Advanced test: electromyography, electrooculography, and videotaping
Investigation
-bMRI and oMRI w/wo contrast
-TFT
Ddx
-ONM = Triggered by sustained eccentric gaze + brief tonic deviation
-SOM = Torsional micro-oscillations (tremor)
-Cyclic 3rd = Cyclic (predicted) weakness/spasm in a fixed rhythm
-Convergence spasm = Miosis + accommodation
-MG = Fatigues
-Graves = Restrictive pattern + orbital signs
-Decomp phoria = Fatigue‑dependent misalignment without spasm
Therapy
-Carbamazepine & oxcarbazepine
*lower dose
-Others: gabapentin, phenytoin, lacosamide
-Tx hypovitamins
-If refractory, surgery→ binocular fusion w/ strabismus surgery
-Behavioral change, if pt has a AM clock to one side change to other
Videos
ONM
-Nasopharyngeal CA, ttx w/ cisplatin + 5-FU, 9y later transient diplopia
*Worse w/ prolonged eccentric gaze
-Tx CBZ
ONM
-Midbrain glioma, RXT 20y before, now R CN III palsy
-ONM observed during ptosis surgery
ONM
-Full resolution within 1y
-Difficult to atrtibute only to ONM
>Pt does not have tonic spasm
ONM
-Remote hx of pituitary macroadenoma
-Referral for intermittent diplopia for several years