The Study On Clinic And Pathophysiology Of Traumatic Optic Neuropathy

Traumatic optic neuropathy (TON) is the most popular kind of optic nerve injury, which accounts for 0.5%～5% in head closing injury. The visual acuity is damaged seriously. Its prognosis is adverse, and 50% left permanent visual acuity loss. In clinic, part patients can recover automatically without treatment, part patients can't recover with any treatments, and part patients can obtain a good result with timely and effective treatment. The selection of treatment has been controversial, of which the common treatment methods are drug therapy with corticosteroid and operation. Optic canal decompression by transnasal endoscopic approach is the main operative way. But the effects of operation were greatly different in some reports.We developed a series of study to investigate the mechanism of TON for the guidance of clinical diagnosis and treatment.Part One: The clinic analysis of traumatic optic neuropathyObjective: To evaluate the therapeutic efficacy of operative and conservative treatment and analyze the clinical factors affecting the efficacy in traumatic optic neuropathy (TON).Methods: A retrospective study of 95 patients (100 eyes) with TON was conducted. 47 cases (48 eyes) under combined treatment of optic canal decompression by transnasal endoscopic approach and drug were grouped into operation group. 48 cases (52 eyes) under drug therapy were grouped into conservative group. The visual acuity was divided into 5 grades: no light perception(NLP), light perception(LP), hand move, count finger, >0.02 , marked asⅠ～Ⅴrespectively. Postoperative follow-up lasted 3～12 months to observe the recovery of visual acuity.Results:1. In operation group, 40 eyes (40/48) were confirmed optic canal fracture by operation; 23 cases by CT. The diagnosis rate of CT was 57.5% (23/40).2. Significant difference existed between the therapeutic efficacy of operation and conservative group in patients with the visual acuity ofⅡ～Ⅳ.3. In operation group, the therapeutic efficacy of the patients whose visual acuity was improved from NLP after glucocorticoid therapy was better than that of the patients with no improvement.4. In operation and conservative group, the therapeutic efficacy of patients with the visual acuity ofⅡ～Ⅳwas better than that ofⅠ.5. In operation and conservative group with the visual acuity ofⅡ～Ⅳ, the therapeutic efficacy of patients with duration shorter than seven days before operation was better than that of patients with duration longer than seven days.Conclusion:1. The imaging findings of optic canal fracture can't be determinants of operation.2. To the patients with visual acuity of LP and above LP, the therapeutic efficacy of patients under combined treatment of optic canal decompression by transnasal endoscopic approach and drug is better than drug treatment.3. To the patients with visual acuity of NLP, after glucocorticoid therapy, the patients with visual acuity improved is suitable for aggressive surgical treatment; the patients without visual acuity improved should abandon surgical treatment unless they require strongly.4. To the patients with visual acuity of LP and above LP, after glucocorticoid therapy, the patients with visual acuity improved obviously are suitable for conservative treatment; the patients without visual acuity improved or improved unobviously are suitable for operation treatment.5. Disease course is an important influential factor. The patients should be operated within 7d.Part two: The establishment and study of an experimental animal model of traumatic optic neuropathyObjective: To establish animal model of TON that resemble to clinical state and study mechanical principle and change of pathophysiology of its nerve injury for clinical diagnosis and treatment.Method: 10 rabbit heads were dissected to find the relationship of optic nerve and orbit, skull base. New Zealand white rabbits were regarded as the research objects. The method of Wang Yi was repeaded and improved. Mild and severe animal models of TON were established by Wang Yi reformative operation separately. After the spring gun struck, all animals were observed on pupil and direct light reflex and received the examinations of pattern reversal visual evoked potentials (PR-VEP) and the observation of pathophysiology of normal and injury optic nerve.Results:1. After recovery from anesthesia, the mydriasis and disappearance or dullness of direct light reflex hanppened in all injury eyes. No brain contusion, no infection, no orbital fracture, no death. 1 optic nerve was broken with complete tunica vaginalis.2. The difference of latency and amplitude between the right and left eyes before struck showed no statistical significance (p>0.05).In group A, the latency and amplitude of injury eyes deteriorated gradually. The amplitude of 1d was above 50% of normal. In group B, the waves became flat rapidly. The amplitude of 1d was lower than 50% of normal. The waves disappeared completely in 1 week after struck. The difference between control eyes and injury eyes at each point showed statistical significance.3. In control eyes, the optic nerve fiber was intensive, regular and stained evenly with a few oligodendrocytes (OLs). The edema, vacuolar degeneration and telangiectasis happened on 1 day after struck. Serious edema and hyperplasia of Ols were seen at 1 week. At 2 weeks, edema reduced, interspersed necrosis appeared. At 4 week after struck, a lot of necrosis and glial scar appeared. The pathomorphological changes of injury eye in group B showed more serious than that in group A in any time.Conclusion:1. The reformative operation with high success rate can establish constant nerve injury. The animal model with little trauma and low mortality is resembled to clinical state.2. After injury, optic nerve goes through 3 stages: edema, hyperplasia and atrophy. The treatment can get better therapeutic efficacy in edema stage.3. In mild injury eyes, the injury deteriorated gradually. However, part visual function remained. In severe injury eyes, pathomorphological changes were irreversible sooner after struck, and the visual function lost completely.3. There is a good correlation between PR-VEP and pathomorphology. PR-VEP can guide the clinical diagnosis and treatment. The patients whose amplitude of 1d was above 50% can obtain good efficacy with normative treatment.