Histopathology and ultrastructural examination of optic nerve sheath biopsies after optic nerve sheath decompression with and without mitomycin

PURPOSE: We chose to compare histologically and ultrastructurally changes in the optic nerve sheath after optic nerve sheath decompression, initially after a second surgery and after treatment with mitomycin-C. The mechanism by which optic nerve sheath decompression alleviates papilledema can be further understood in consideration of the results. METHODS: Tissue was obtained by biopsy from 3 first-time surgical and 4 reoperative cases with and without mitomycin-C in patients with idiopathic intracranial hypertension. The sheaths were fixed in a mixture of 2% paraformaldehyde and 2% glutaraldehyde, osmicated and dehydrated in a series of ethanol, and finally embedded in epon. Tissue blocks were sectioned at 1 microm and stained with both PPD and toluidine blue. Thin sections were examined by transmission electron microscopy. RESULTS: Normal meningeal tissue obtained at the time at optic nerve sheath decompression consisted mainly of collagen, closely packed and roughly parallel to the axis of the optic nerve. Collagen deposition seen in scar tissue after secondary optic nerve sheath decompression was extremely disorganized and irregular, with the individual fibers laid down seemingly at random. There was little sense of layering or of parallel arrays. Mitomycin-C appeared to influence collagen deposition in such a way that the collagen was more regularly packed and more closely resembled unoperated tissue. CONCLUSIONS: The regular well-organized collagen packing seen in normal sheath tissue is disrupted and replaced by less organized but compact scar tissue after optic nerve sheath decompression. With mitomycin use, more regular collagen packing closely approximating that found in unoperated sheath occurs. This configuration of fibers lends support for the filtration mechanism of optic nerve sheath decompression in treating papilledema.     

Treatment of pseudotumor cerebri by primary and secondary optic nerve sheath decompression

We performed optic nerve sheath decompression in 53 patients (101 eyes) with pseudotumor cerebri and visual loss. Sixty-nine eyes (85 patients) with acute papilledema uniformly had improved visual function after optic nerve sheath decompression. Of 32 eyes with chronic papilledema (18 patients), only ten had improved visual function after optic nerve sheath decompression. This difference was significant (P = .0001). Thirteen eyes required secondary or tertiary optic nerve sheath decompression after an initial successful result. Eleven of 13 eyes had improved visual function after repeat optic nerve sheath decompression. We believe that patients with acute papilledema and visual loss should be offered optic nerve sheath decompression, and if symptoms recur, repeat optic nerve sheath decompression is a safe and effective treatment option.     

Farris–Tang retractor in optic nerve sheath decompression surgery

Purpose: Our purpose is to introduce the use of the Farris–Tang retractor in optic nerve sheath decompression surgery.Methods: The procedure of optic nerve sheath fenestration was reviewed at our tertiary care teaching hospital, including the use of the Farris–Tang retractor.Results: Pseudotumor cerebri is a syndrome of increased intracranial pressure without a clear cause. Surgical treatment can be effective in cases in which medical therapy has failed and disc swelling with visual field loss progresses. Optic nerve sheath decompression surgery (ONDS) involves cutting slits or windows in the optic nerve sheath to allow cerebrospinal fluid to escape, reducing the pressure around the optic nerve. We introduce the Farris-Tang retractor, a retractor that allows for excellent visualization of the optic nerve sheath during this surgery, facilitating the fenestration of the sheath and visualization of the subsequent cerebrospinal fluid egress. Utilizing a medial conjunctival approach, the Farris–Tang retractor allows for easy retraction of the medial orbital tissue and reduces the incidence of orbital fat protrusion through Tenon’s capsule.Conclusion: The Farris–Tang retractor allows safe, easy, and effective access to the optic nerve with good visualization in optic nerve sheath decompression surgery. This, in turn, allows for greater surgical efficiency and positive patient outcomes.     

Management of traumatic optic neuropathy--a study of 23 patients.

Twenty three patients with traumatic optic neuropathy were managed by medical and surgical treatment as follows. High dose intravenous steroids were initiated in all patients. If visions did not improve significantly after 24 to 48 hours decompression of an optic nerve sheath haematoma by medial orbitotomy and neurosurgical decompression of the optic canal were considered based on computed tomographic scan findings. Nine of 16 patients who received steroids only showed significant improvement. One of three showed improvement on optic nerve decompression after steroid failure; three or four showed improvement on optic nerve decompression after steroid failure; three or four showed improvement with combined optic nerve sheath decompression by the medial orbitotomy and decompression of the optic canal by frontal craniotomy. A lucid interval of vision after injury and an enlarged optic nerve sheath were associated with an improved prognosis. Five of the 23 patients had a lucid interval and all five had a final improved vision, while only five of 18 patients without a lucid interval improved. Similarly seven of the nine with an enlarged optic nerve sheath showed improvement while only three of 10 patients (three bilateral cases) who presented with no light perception improved with medical and surgical treatment. While a prospective controlled study of the management of traumatic optic neuropathy is necessary this preliminary study suggests that treatment of traumatic optic nerve sheath haematoma by optic nerve sheath decompression should be considered in selected patients.     

Arachnoid cyst of the intraorbital portion of the optic nerve with unilateral disc oedema and transient shallowing of the anterior chamber. A case report

An unusual occurrence of chronic monocular disc oedema, visual loss and shallowing of the anterior chamber in a patient with an arachnoid cyst involving a portion of the intraorbital optic nerve was reported. Decompression of the optic nerve sheath through a Kr?nlein approach was followed by prompt deepening of the anterior chamber and a gradual, delayed relief of the disc oedema. It is concluded that orbitotomy and decompression of the optic nerve sheath should be done before atrophic changes of the optic nerve and visual loss begin to develop.     

管内段视神经间接损伤20例疗效分析

目的 评价视神经鞘减压术的疗效。方法 ２０例管内段视神经间接损伤患者（视力光感者３例,无光感者１７例）５例施视神经管减压开放术,９例施视神经鞘减压术,６例拒绝接受手术,使用药物治疗。结果 ５例视神经管减压开放术,治疗效果均不明显。９例视神经鞘减压术中,３例治疗效果显著。６例药物治疗者,治疗效果均不明显。结论 视神经鞘减压术治疗管内段视神经间接损伤,此方法有效可行。     

Diagnosis of optic nerve sheath meningioma during optic nerve sheath decompression

Optic nerve sheath meningioma (ONSM) is typically diagnosed based on clinical suspicion and imaging characteristics and is most often treated with radiation. Historically, biopsy, optic nerve sheath decompression, and debulking surgeries have been avoided for fear of optic nerve vascular disruption and tumor spread into the orbit. This is a case of a 48-year-old man who presented with unilateral optic disc edema, declining visual acuity, and a visual field defect. Despite an initial improvement with acetazolamide, his vision subsequently worsened. With an elevated lumbar puncture opening pressure and imaging showing right optic nerve sheath enhancement, the differential diagnosis included ONSM, perineuritis and idiopathic intracranial hypertension (IIH). Optic nerve sheath decompression (ONSD) with biopsy was performed, simultaneously decompressing the nerve and yielding a sample for pathologic analysis. A pathologic diagnosis of ONSM was made and treatment with radiation was subsequently initiated, but vision began to improve after the surgical decompression alone.     

Vertical lid split approach for optic nerve sheath decompression

We describe a vertical lid split orbitotomy approach to perform optic nerve sheath fenestration which was done in a patient with idiopathic intracranial hypertension. A vertical lid split incision was used to enter the superomedial orbit and approach the optic nerve sheath. This approach resulted in a successful nerve sheath fenestration, with improvement in the patient''s symptoms. The vertical lid split incision provides access to the optic nerve sheath with minimal morbidity and may be an option for optic nerve sheath decompression.     

Optic canal decompression: a cadaveric study of the effects of surgery

PURPOSE: To simulate a transphenoidal medial optic canal decompression and determine the anatomic effect on the optic nerve. METHODS: A medial optic canal decompression was performed on 5 cadaveric optic canals within 12 hours of death. Two canals were decompressed under direct visualization and 3 were decompressed by a transphenoidal endoscopic approach. The optic canal was subsequently removed en bloc, beginning at the annulus of Zinn and extending to the optic chiasm. Each specimen was processed and examined grossly. Serial coronal step sections of the entire length of the intracanalicular optic nerve were assessed histologically. RESULTS: Microscopic examination of the intracanalicular portion of optic nerve revealed incision in an extraocular muscle at the annulus, incomplete bone removal, fraying of the dural sheath, incomplete dural/arachnoid release, and incision in the pia and optic nerve. CONCLUSIONS: Transphenoidal medial wall decompression of the optic nerve canal with dural sheath opening may induce physical damage to the nerve. Any hypothetical value in dural-arachnoid sheath opening must be weighed against the potential for harm to the optic nerve caused by the surgical intervention.     

视神经鞘减压术的疗效与风险

视神经鞘减压术(ONSD),也称视神经鞘开窗术(ONSF),是一种通过在视神经鞘上开窗以释放视神经周围蛛网膜下液、为视神经减压的外科手术。该手术是为了缓解颅高压所致威胁视力的视乳头水肿(papilledema),常用于药物降颅压无效或不能耐受药物、进行性视力丧失的大脑假瘤综合征(PTCS)患者。本文综述了视神经鞘减压术的适应证、禁忌证、手术方式及其疗效与并发症。