gms | German Medical Science

Permanent visual loss or blindness is a hazardous complication of traumatic optic neuropathy (TON). Direct traumatic blindness is usually due to penetrating injuries to the area of the optic nerve while indirect TON is due to blunt head traumas. Recommendations for management of traumatic injuries to the optic nerve in the literature include expectant management, medical therapy, surgical treatment and medical therapy combined with surgical decompression, but a generally accepted standardized modality for therapy is not establish as of today.

The preference for the therapy regime of indirect TON patients is still individual and more or less based on personal opinions and / or surgical skills.

Since 1991 an endonasal endoscopic approach for decompression of the optic nerve (OND) including sheath slitting combined with intravenously applied high dose corticoid therapy (30 mg/kg loading dose and then 5,5 mg/h to 36 to 48 hours; Boston scheme) has been the therapy modality of choice in patients requiring surgery for indirect TON in our hospital. Meanwhile 51 indirect TON patients have undergone this procedure.

During a 14-year period since 1991 fifty-one patients with indirect TON were referred to us for endoscopic OND by ophthalmologist or neurosurgeon following blunt head traumas.

We retrospectively evaluated epidemiologic data, indications, surgical outcome and complication rates.

If surgical intervention was indicated we performed an endoscopic sphenoethmoidectomy with preservation of the middle turbinate under general anaesthesia. The bulge of the internal carotid artery (ICA) and the optic nerve were identified as they course through the lateral wall of the sphenoid sinus. 7 to 10 mm anterior to the optic tubercle the lamina papyracea was then removed and the bone covering the optic canal was thinned by a modified diamond drill. Using a dissector the thinned bony canal was removed from over the optic nerve. Roughly half of the circumference, the medial and inferior part of the bony optic nerve canal could be removed in this way, for a distance of 1 up to a maximum of 2 cm. Afterwards the optic nerve sheath and the annulus of Zinn were incised with a sickle knife. To avoid a potential cerebrospinal fluid fistula the opening of the optic nerve sheath was covered by fibrin glue.

If orbital decompression because of an orbital haematoma was demanded, it could easily be performed now. Whenever feasible, the patients were treated with intravenous applied high dose corticoid therapy as well, 30 mg/kg as a loading dose and then 5,5 mg/h to 36 to 48 hours following the Boston scheme.

Fifty-one patients with indirect TON have undergone endoscopic OND since 1991. Their ages ranged from 7 to 86 years (mean 36 years), 42 (80%) were male, 10(20%) were female.

12 of 51 patients (23.5%) were victims of traffic accidents, 12 (23.5%) of downfalls, 1 (1,9%) had an affray and for 26 (52,9%) the original trauma history was not available any more. 29 right (52%), 21 left (46%) and 1 (2%) bilateral effected sides were operated. Indications for surgical intervention were complete loss of vision in 37 of 51 patients (72.5%). 10 patients (19.7%) deteriorated or had no improvement of their visual acuity under medical therapy with visual loss <0,2, constriction of their visual field, afferent pupillary defect in the swinging flash light test and either 1 unconscious patient of these 10 was indicated by missing recordable Visual Evoked Potentials (VEP). All patients showed a fracture line in the optic canal and an optic nerve compression in computer tomography. Pre-operative ophthalmologic data of 4 Pts. (7.8%) were not available any more.

The posttraumatic period until surgery ranged from 6 hours to 15 days (mean 50 hours).

One to six months after OND 6 patients (11.7 %) had recovered full visual acuity up from 0.8 to 1.0. 17 patients (33.4 %) could see dark/light, count fingers, with vision up to 0.5; however with persisting impairment of their visual field. 20 patients (39.2 %) showed no improvement or blindness. Retrospectively data of 8 patients (15.7 %) were not available.

Together we had 19 patients (37.3%) with positive results (defined as upgrade of visual acuity more than 0.1), 23 (45.1%) negative results (defined as steady state of visual acuity) 9 (17.6%) could not be specified because of missing preoperative or postoperative data. No patient disclaimed on worsening of his visual acuity, only 1 patient died 30 days after surgery because of accompanying cerebral problems. No direct complications like postoperative bleeding, liquorrhea or meningitis due to the surgery occurred.

Clear statements of the ophthalmologist or neurologist about the visual acuity of the traumatized patients should be available before performing endoscopic OND. If possible, adequate objective investigations, like VEP should be performed before surgery as otherwise the success of the interventional method cannot exactly be qualified.

The advantages of endonasal endoscopic procedures include, but are not restricted to decreased morbidity, preservation of olfaction, rapid recovery time, and no external scars e.g., compared to more traditional approaches like a craniotomy or extranasal transethmoidal, transorbital or transantral approaches are well known. But only accurate preoperative exploration and radiographic investigation, e.g. including CT scans with contrast fluid or MRA to rule out aneurysm of internal carotid artery allow the experienced endoscopic endonasal surgeon to operate on TON patients without complications.

Endonasal endoscopic OND is an elegant and – in experienced hands – non traumatizing surgical technique. As of today, however, clear indications are yet to be established.