Nitrous Oxide Impairs Axon Regeneration after Nervous System Injury in Male Rats.

BACKGROUND: Nitrous oxide can induce neurotoxicity. The authors hypothesized that exposure to nitrous oxide impairs axonal regeneration and functional recovery after central nervous system injury. METHODS: The consequences of single and serial in vivo nitrous oxide exposures on axon regeneration in four experimental male rat models of nervous system injury were measured: in vitro axon regeneration in cell culture after in vivo nitrous oxide administration, in vivo axon regeneration after sharp spinal cord injury, in vivo axon regeneration after sharp optic nerve injury, and in vivo functional recovery after blunt contusion spinal cord injury. RESULTS: In vitro axon regeneration 48 h after a single in vivo 70% N2O exposure is less than half that in the absence of nitrous oxide (mean ± SD, 478 ± 275 um; n = 48) versus 210 ± 152 um (n = 48; P < 0.0001). A single exposure to 80% N2O inhibits the beneficial effects of folic acid on in vivo axonal regeneration after sharp spinal cord injury (13.4 ± 7.1% regenerating neurons [n = 12] vs. 0.6 ± 0.7% regenerating neurons [n = 4], P = 0.004). Serial 80% N2O administration reverses the benefit of folic acid on in vivo retinal ganglion cell axon regeneration after sharp optic nerve injury (1277 ± 180 regenerating retinal ganglion cells [n = 7] vs. 895 ± 164 regenerating retinal ganglion cells [n = 7], P = 0.005). Serial 80% N2O exposures reverses the benefit of folic acid on in vivo functional recovery after blunt spinal cord contusion (estimate for fixed effects ± standard error of the estimate: folic acid 5.60 ± 0.54 [n = 9] vs. folic acid + 80% N2O 5.19 ± 0.62 [n = 7], P < 0.0001). CONCLUSIONS: These data indicate that nitrous oxide can impair the ability of central nervous system neurons to regenerate axons after sharp and blunt trauma.

Orbital Septum Fibrosis in Congenital Ptosis Correlates With Eyelid Function: A Clinicopathologic Study.

PURPOSE: Congenital ptosis can threaten visual function and is usually treated with surgical correction. This study tests the hypothesis that congenital ptosis involves not only the levator muscle but also the orbital septum, which may tether the eyelid in the primary position. METHODS: A retrospective chart review was performed on 30 patients (41 eyelids) with congenital ptosis who underwent surgical correction that included partial septum excision. Histologic analysis was performed by a masked pediatric pathologist, with grading of septal tissue disorganization and fibrosis based on standard histologic criteria. An independent comparison of histologic grading with clinical ptosis measures was then performed. RESULTS: Fifteen eyelids demonstrated significant septal fibrosis, 19 were mild, and 7 were not fibrotic. Thirty-six eyelids demonstrated histologic disorganization. Mildly fibrotic eyelids were found to have reduced preoperative levator function than those that were not fibrotic (2.84 ± 1.92 vs. 9.57 ± 4.76 mm; p < 0.0001). Samples that demonstrated significant fibrosis were also found to have reduced preoperative levator function (4.67 ± 2.12 vs. 9.57 ± 4.76 mm; p = 0.0007). Histologically disorganized samples were also found to have a lower preoperative levator function (9.50 ± 6.04 vs. 3.99 ± 2.49; p = 0.0052). CONCLUSIONS: Orbital septae in patients with congenital ptosis demonstrate histologic disorganization and fibrosis. When decreased levator function is observed clinically, septal fibrosis and/or disorganization is likely present. These observations suggest that debulking the fibrotic septum during congenital ptosis surgery may improve outcomes by releasing the eyelid from its congenitally tethered position, improving eyelid elasticity.

An Aesthetic Orbicularis Oculi Myectomy Technique for Blepharospasm: Use of Topical 5-Fluorouracil and Fibrin Sealant.

PURPOSE: To describe a modified technique of orbicularis oculi myectomy for refractory blepharospasm. This technique includes removal of orbicularis muscle, reformation of the eyelid crease and pretarsal platform using fibrin sealant (Tisseel), and topical 5-fluorouracil to reduce scar formation and improve aesthetic outcome. METHODS: Retrospective chart review of 7 patients who underwent bilateral orbicularis oculi myectomy with our technique from 2013 to 2016. Outcome measures were postoperative botulinum toxin dose, frequency, duration between treatments, the amount of lagophthalmos, severity of dry eye, and patient satisfaction with aesthetic and functional outcome. RESULTS: Patients who underwent the aesthetic myectomy technique had significantly decreased botulinum toxin use with relief of symptoms postoperatively. Only 1 of 7 patients experienced mild dry eye symptoms postoperatively, managed with artificial tears. All patients were satisfied with the aesthetic and functional outcome. CONCLUSIONS: The aesthetic myectomy technique provides effective treatment for blepharospasm with good functional and aesthetic outcome.

Modified full-thickness anterior blepharotomy for upper eyelid retraction in children.

Graded full-thickness anterior blepharotomy has been used to treat eyelid retraction in adult patients with thyroid eye disease. We report 2 children diagnosed with upper eyelid retraction who underwent a modified full-thickness anterior blepharotomy. In both cases, symptoms resolved and cosmetically acceptable outcomes were achieved.