Nasal endoscopic optic nerve decompression
Zhang Liqiang
Applied Anatomy
The medial wall of the orbit consists of the sieve cardboard, the lacrimal bone, and the thicker posterior pterygoid bone, of which the pterygoid bone forms the orbital apex. The degree of pneumatization of the pterygoid sinus determines whether the optic nerve is embedded or exposed in its lateral wall. If a supraparietal septum is present, the degree of pneumatization of the posterior septum will likewise determine the degree of exposure of the optic nerve. The optic nerve is divided into 4 parts: the intracranial segment, the canal segment, the intraorbital segment, and the intraglobular segment. (1) Intracranial segment: from the optic cross to the optic nerve canal. It is about 15 mm long, protected by skull and brain tissue, and generally not easily subjected to indirect injury; (2) canal segment: about 8 mm long, located in the lateral wall of the posterior group of septal and pterygoid sinuses, fixed in the bony canal, with blood supply from the soft meningeal branch of the internal carotid artery. The posterior foramen of the optic canal is wider, with a diameter of about 5.0-9.5 mm, averaging 7.1 mm. the optic canal is located in the upper and lower pterygoid winglets where the two roots meet the body of the pterygoid bone, and is approximately circular in cross-section. The medial wall of the optic nerve canal is adjacent to the pterygoid sinus and the posterior group of septal sinus air spaces, which can cause a mound-like or semi-tubular elevation of the outer superior bony wall of the pterygoid sinus, where the bone wall is thin, about 0.2-0.3 mm. The optic nerve canal is lateral to the root of the anterior bed process, with the upper boundary at the base of the anterior cranial fossa and the lower wall at the root of the pterygoid winglet, separated from the supraorbital fissure. The optic nerve is surrounded by a sheath formed by the extension of the dura mater. In the optic nerve canal, the three layers of meninges surrounding the optic nerve fuse with each other above and are closely connected to the periosteum above. Therefore, the optic nerve has no room for movement in the canal segment, and it is easy to suffer indirect injury during head trauma; (3) intraorbital segment (posterior segment): it is located deep in the orbit outside the optic nerve, about 23~30mm long, and is protected by fat and extraocular muscles, and has some room for movement, so it is not easy to suffer indirect injury. However, orbital hematoma can cause compressive optic neuropathy with protrusion of the eyeball and increased intraorbital pressure; (4) intraorbital segment (intraocular segment): located in the eye, about lmm long, easily caused by twisting or displacement of the eyeball resulting in avulsion injury of the optic nerve in the intraorbital segment. The optic canal is composed of the upper root of the pterygoid pallidum forming the upper wall, the lower root forming the outer lower wall, and the sinus wall between them forming the medial wall, of which the medial wall is the longest. The key to successful and effective nerve canal decompression under nasal endoscopy is to find the inner wall of the optic nerve canal in the sinus and fully resect the inner wall of the optic nerve canal to reach the full length of the bone wall. Zhang Liqiang, Department of Otolaryngology, Qilu Hospital, Shandong University
Overview
Most traumatic optic neuropathies are caused by fracture of the optic nerve canal resulting in compression of the optic nerve, but also by subsheath hemorrhage and clot compression of the optic nerve, and in a few patients, permanent blindness is caused by optic nerve fracture or axonal dissection. Traumatic optic neuropathy is the most important indication for nasal endoscopic optic nerve decompression. Currently, there is controversy as to which treatment is more effective for traumatic optic neuropathy receiving high-dose hormone shock therapy or optic nerve decompression. In a meta-analysis of the published literature, Cook et al. concluded that high-dose hormone shock therapy, surgical decompression therapy, or both were more effective than no treatment at all. 111 patients with traumatic optic neuropathy were divided into two groups: one group was treated with high-dose hormone shock therapy and then underwent optic nerve decompression if there was no improvement in visual acuity; the other group was treated with hormone therapy only. The results of the study showed that the treatment effect of the first group was significantly better than that of the second group.
Indications and contraindications for surgery
Indications for nasal endoscopic optic nerve canal decompression: 1. closed cranial trauma, no damage to the eye, severe ipsilateral visual loss or blindness; 2. dilated pupils, diminished or absent direct light reflex, presence of indirect light reflex (Marcus-Gunn pupil); 3. visual field defects if the patient has residual vision; 4. normal fundus; 5. a small number of patients may have nasal bleeding or cerebrospinal fluid Nasal leakage.
Generally speaking, blindness immediately after injury is often caused by optic nerve breakage or optic nerve axon dissection, with poor surgical results; if post-injury vision loss occurs gradually. If the post-injury vision loss occurs gradually, it is often caused by optic nerve compression and entrapment, and early surgery is more effective. According to domestic data, the efficiency of surgery within 10 days after the injury is 72%, and the efficiency of surgery more than 10 days is only 15%; according to foreign data, optic nerve canal decompression should be performed within a few hours after the injury, and the effect of surgery for complete vision loss more than 24 hours is often poor. Therefore, surgery should be performed as early as possible, and high-dose intravenous methylprednisolone should be applied before and after surgery.
Contraindications to nasal endoscopic optic canal decompression: fracture of the optic canal combined with a pseudoaneurysm of the internal carotid artery.
Preoperative preparation
1. detailed ophthalmologic examination, including visual acuity, visual field and fundus.
2. neurological examination. Attention to the presence of cerebrospinal fluid leakage and the presence of cranial injury.
3. Coronal and axial CT scans of the sinuses can observe the morphology, anatomical variation and pathological changes of the septal and pterygoid sinuses.
Patient position and anesthesia
General anesthesia. 1% bupivacaine/epinephrine swabs are used to contract and surface anesthetize the nasal mucosa. The patient is placed in the supine position, routinely disinfected, and sterile towels are placed.
Surgical points
Intranasal septopalpebral sinus excision is performed first. The hooks are removed, the septal vesicles are opened, and all of the anterior and posterior groups of septal sinus air spaces are removed in the same manner as the septal sinus resection. During this procedure, it is often possible to see the posterior septal sinus air spaces broken. There is old blood accumulation in the sinus. When combined with skull base and cardboard displacement, the operator is easily disoriented intraoperatively. In the posterior septal sinus, two important anatomic landmarks, the posterior part of the cardboard and the septal recess, must be identified.
After septal sinus resection, the sieve apex, orbital cardboard and anterior wall of the pterygoid sinus are examined in detail, noting any fracture lines or bone destruction. The sieve apex, if fractured, should be carefully observed for cerebrospinal fluid leakage. The thicker bone located on the surface of the connection between the orbital apex and the pterygoid sinus is called the optic rongeur. Any fracture of the anterior wall of the pterygoid sinus is mostly comminuted and involves the optic rongeur.
The anterior wall of the anterior pterygoid sinus should be fully enlarged and the upper end of the anterior wall of the pterygoid sinus should be removed as much as possible so that the parietal wall of the pterygoid sinus and the parietal wall of the posterior group of septal sinuses continue. At this point, the pterygoid sinus is often seen to be filled with old blood or blood clots, which are carefully aspirated with a suction device. Strict hemostasis.
The walls of the pterygoid sinus are carefully examined and the optic nerve, carotid artery, and pituitary fossa are identified. A bulge formed by the maxillary branch of the trigeminal nerve can often be seen in the lower third of the lateral wall of the pterygoid sinus. It is possible to mistake this area for the optic nerve. The optic nerve is usually located at the junction of the upper middle 1/3 of the lateral wall of the pterygoid sinus. Note the inspection of the optic canal bulge, which is the most frequent site of fracture, as evidenced by displacement of the fracture fragment into the sinus or orbit, often with some accumulation of clots. This area is the closest to the optic nerve, and minor fracture fragment compression or intraorbital clot buildup can affect optic nerve function. The bone of the optic ridge is thick and difficult to peel with conventional surgical instruments, requiring the use of a diamond drill to thin the bone until it is nearly clear. A blunt stripper is used to start stripping the cardboard posteriorly at a point approximately 1.5 cm anterior to the junction of the posterior septal airspace and the pterygoid sinus. Care should be taken to maintain the integrity of the orbital fascia at this point, because if the orbital fascia is torn, the orbital fat will detach from the orbit and interfere with the surgical operation. The posterior orbital apical bone fragment is also peeled off. After stripping the orbital apical bone, the optic canal should be reached. In most patients, the bony wall of the optic canal is thin and can be easily peeled from the surface of the optic nerve. However, in some cases, the bone wall of the optic canal is thick, and the bone wall needs to be thinned with a diamond drill before it can be peeled off. In case the fracture fragment is connected to the bone of the optic nerve-internal carotid artery septum, it should not be removed rashly to avoid damaging the internal carotid artery and the ophthalmic artery. In this case, a sharp small biting forceps or hawkbill forceps can be used to bite away under accurate observation, preserving the optic nerve-internal carotid artery septum without treatment. Rotating the biting forceps from side to side in an attempt to break the bone fragment is contraindicated. It is not necessary to remove fragments of bone from the lateral wall of the pterygoid sinus beyond the extent of the optic canal.
The optic nerve can be seen after opening the bony wall of the ramus of the optic nerve canal and cutting the optic nerve sheath, which is usually grayish in color, and the optic nerve can be congested and edematous if it has been under pressure for a long time. The elasticity and toughness of the nerve can be felt by gentle touch with a blunt probe. Before dissecting the sheath, it is important to know the location of the ophthalmic artery, which usually travels posteriorly and inferiorly to the optic nerve; in rare cases, it may travel inferiorly to the optic nerve. Therefore, incising the sheath from the medial aspect of the optic nerve reduces the chance of damaging the ophthalmic artery. The sheath of the optic nerve is incised with a sharp sickle blade, and the incision is continued to the fascia posterior to the orbital apex, at which point the intraorbital fatty tissue is dislodged. Since the fat overlying the medial rectus muscle is very thin, it is important to avoid damaging the medial rectus muscle during surgery. It has also been advocated that the optic nerve sheath need not be incised.
After careful hemostasis and confirmation of no active bleeding, the pterygoid and septal sinus cavities are flushed with saline containing antibiotics. The pterygoid sinus and posterior group of septal sinuses are gently filled with gelatin sponges impregnated with antibiotics. The anterior septal sinus and nasal cavity are gently filled with iodoform gauze or Vaseline gauze, not too tightly.
Postoperative treatment
1. semi-sitting position for 3 days and restriction of water intake.
2. Apply broad-spectrum antibiotics systemically. Prevent the occurrence of infectious meningitis, and apply high-dose hormones, energy combination, neurotrophic drugs, etc. at the same time.
3. check eye conditions such as pupil size, direct and indirect light reflex, visual acuity, etc. Follow up for more than six months.
4. On the third day after surgery, the intranasal gauze was withdrawn and the gelatin sponge was cleaned after 1 week. The surgical cavity was flushed with saline with antibiotics and hormones.
Complication control
1. cerebrospinal fluid nasal leakage and meningitis; often due to the severity of the injury, or due to incision of the optic nerve sheath during surgery.
2. hemorrhage: rupture of the anterior sieve artery or internal carotid artery can cause severe or even fatal hemorrhage. When encountering this situation. A large amount of blood should be transfused. Carotid artery ligation, or detachable balloon embolization with an arterial catheter.
Evaluation
Optic nerve decompression must be performed by an experienced and skilled nasal endoscopist. Intraoperative damage to the skull base may be complicated by cerebrospinal fluid nasal leakage, and the internal carotid artery may be damaged. Therefore, failure to properly handle the fractured fragments of bone can have catastrophic consequences. Great care must be taken when exposing the optic nerve, especially when stripping the optic canal of bone. The use of inappropriate surgical instruments may further damage the patient’s vision.