Optic tube top abrasion during saddle nodule meningioma

J.
Cromenius University School of Medicine and University Hospital of Bratislava, Slovakia, Department of Neurosurgery.
Kozák et al.
reported a case of microsurgical treatment of saddle nodular meningioma with visual impairment in the left eye
.

The results were published in the May 2022 issue
of Acta Neurochir.

——Excerpt from the article chapter

【Ref: Kozák J, et al.
Acta Neurochir (Wien).
2022 May; 164(5):1397-1400.
doi: 10.
1007/s00701-021-05083-9.
Epub 2022 Jan 30.
】

Research background

Treatment of saddle nodular meningioma (TSM) with optic nerve compression is challenging
.

Most of these tumors are benign, so they must be fully resected and retain good function
.

Saddle nodular meningioma originates from the butterfly margin, optic groove, and saddle nodules, and is usually located in the middle of the saddle, with the optic cross pushed posteriorly and upwards and the optic nerve laterally
.

Even if the compression of the tumor itself is not enough to cause visual dysfunction, the compressed optic nerve is pushed into peripheral structures, such as the optic neural tube, the A1 segment of the anterior cerebral artery, and especially the sharp edges of the sickle ligament, which can still lead to visual field defects and decreased
vision.

The optic neural tube is 5 mm long on average, conical in cross-section, separated from the medial edge of the supraorbital fissure by the optic column
.

The lateral side of the optic neural tube is bounded by the anterior bed process, the upper part is the sphenoid winglet, and the medial boundary is the sphenoid sinus
.

The optic nerve and ophthalmic artery travel inside the optic neural tube, and the ophthalmic artery is usually located below the optic nerve and turns outward into the orbit
.

At the cranial inlet port of the optic neural tube, the optic nerve is covered by a sickle ligament extending from the anterior bed process to the saddle nodule (Figure 1), and
the length of the covered nerve varies from 1 mm to 1 cm.

The blood supply to the optic chiasm comes from the branches of the internal carotid-superior pituitary artery, the anterior cerebral artery, the
anterior choroidal artery, and the posterior communication artery.

Figure 1.
Optic neural tube and surrounding structures
.

Tuberc.
:Saddle nodules;Falc.
Lig.
:sickle ligament;Ant.
Clin.
: Anterior bed protrusion
.

The stripping ions are located between
the sickle ligament and the optic nerve.

J.
Cromenius University School of Medicine and University Hospital of Bratislava, Slovakia, Department of Neurosurgery.
Kozák et al.
reported a case of microsurgical treatment of saddle nodular meningioma with visual impairment in the left eye
.

The results were published in the May 2022 issue
of Acta Neurochir.

Research Methods

The article describes the surgical process: the patient is in a supine position, the head is slightly extended, rotated 20-30° to the opposite side; Secured
using the Mayfield headstand.

Indwells in a lumbar large pool drainage tube at the start of surgery
.

The surgical incision is within the hairline of the left forehead and is curved; Separated subfascia, the frontotemporal branch of the facial nerve is retained, the temporal muscle is stripped and turned backwards
.

Holes are drilled at key holes to make the frontotemporal bone window, and the frontal bone window margin reaches the orbital apex
as much as possible.

Smooth the orbital margins with a high-speed grinding drill and remove the sphenoid crest to the orbital meningeal band
.

Suspension dura mater
.

Cut the dura membrane, sharply separate the lateral fissures, release cerebrospinal fluid to reduce brain tone for dynamic traction
.

Expose the optic nerve, olfactory nerve, and internal carotid artery
.

Keep a safe distance from the optic nerve and undergo intratumor resection
.

After removing a sufficient amount of tumor, begin to grind off the top of the
optic neural tube.

Cut the dura above the optic tube and grind the bone of the optic neural tube using a 3 mm emery drill
.

The process of grinding bone is intermittent, usually lasting no more than 3 seconds, and should be continuously rinsed with normal saline to cool down and protect the optic nerve
.

When only a thin layer of bone remains, it is broken
with peeling ions.

The width of the top of the optic neural tube should reach both sides of the optic neural tube, and the length is determined
according to the specific situation.

The sickle ligament and nerve sheath are then incised for optic nerve decompression
.

The optic nerve at the sickle ligament usually shows signs of compression, marked folds, and discoloration
.

After the completion of optic nerve decompression, recognize the arachnoid surface and preserve the blood supply to the optic nerve, optic chiasm, and pituitary stalk; Further excision of the residual tumor around the optic nerve achieves total resection
.

Finally, carefully check whether the worn bone is connected
to the sinuses.

If connected, depending on the size of the notch, it is repaired
with bone wax or autologous muscle or fat along with fibrin gum.

The dura mater is tightly sutured, and the bone foramen is filled with autologous bone chips; Cover the surface of the bone aperture with temporal muscle and suture the scalp in layers
.

Results of the study

The authors argue that for saddle tumors, particularly saddle nodular meningiomas, optic tube top wear is an important step
in improving vision and total resection of the tumor.

However, there may be a risk of
damage to peripheral nerve tissue.

For large TSMs, the forebed protrusion should be removed
at the same time.

Previous literature reported that the visual improvement rate after this procedure was 42.
4%-91.
7%, and the worsening rate was 10%-25%.


Factors affecting postoperative visual function, including tumor size, preoperative visual function, duration of visual symptoms, and surgical modality
.

Diabetes insipidus is the most common endocrine complication, occurring in 0%-8.
1%, mostly transient; The incidence of cerebrospinal fluid leakage is 3.
9%.


Overall, in the treatment of saddle nodular meningioma surgery that compresses the optic nerve, abrasion of the optic neural tube top is safe and necessary
.