Micro-osseous approach (keyho1e approach)
In the second half of the 20th century, minimally invasive surgery emerged with the newer diagnostic tools, the pursuit of perfect surgery, and the emergence of sophisticated surgical equipment. It is one of the important symbols of minimally invasive neurosurgery and has been used in neurosurgery since 1990. In 1971, Wilsono, an American neurosurgeon, first proposed “keyhole surgery”. In 1991, Fukushima, a Japanese neurosurgeon, reported the experience of micro-osseous maneuvering through unilateral longitudinal fissure to treat anterior artery aneurysm. In the last decade, reports of microsurgery with micro-osseous maneuvers for intracranial lesions have appeared. After the modern mature microsurgical techniques for navigating the surgery, the micro-osseous maneuver technique has been widely performed. In recent years, this technique has been widely used among neurosurgeons in Europe and the United States, and is also gradually recognized and accepted in China with satisfactory results.
1.Concept
During craniotomy, it is harmful to expose brain tissue in a wide range in a non-physiological environment. Reducing the scope of craniotomy can reduce the chance of complications such as postoperative epilepsy and postoperative hematoma. The microbony foramen maneuver is a hallmark of minimally invasive surgery, which does not simply emphasize small incisions. Perneczky, a German neurosurgeon, points out that the connotation of the locked-hole approach is to accurately individualize the design of the cranial site and scope according to the location and nature of each patient’s lesion so that the surgical path is shortest and precise in reaching the lesion, making full use of the natural gaps in the brain tissue, and after adjusting the patient’s head position and the angle of the operating microscope to obtain enough surgical space to complete the surgery and minimize surgical trauma. This is the same principle as that of passing through the hilaroscope, where the hilaroscope hole is small, but the distant field of view obtained is not small, and the further away from the hilaroscope, the larger the visual (operative) field. Minimally invasive craniotomy technique includes the scope of skin preparation, location and length of scalp incision, muscle and periosteal separation, location and size of bone window, incision of dural site, form, precise location of transventricular and cortical access, protection of arachnoid and nerves and blood vessels, reduction of brain tissue pulling degree, and adequate removal of lesions. The ultimate goal of minimally invasive craniotomy technique is to achieve postoperative neurological deficits without aggravating the patient. The micro-osseous maneuver can be used for intracranial tumors, surgery for cerebrovascular diseases, especially for the treatment of lesions at the skull base, such as intracranial aneurysms, pituitary aneurysms, craniopharyngiomas, auditory neuromas and cavernous hemangiomas. In the acute stage of ruptured aneurysm bleeding, a micro-osseous maneuver is not advisable because of severe cerebral edema, which makes it difficult to obtain sufficient surgical space and to accomplish the necessary external decompression. In addition, massive subarachnoid hemorrhage causes unclear anatomic relationships and compromises surgical exposure. When dealing with an anterior anterior communicating aneurysm from a longitudinal approach, the proximal end of the aneurysm-carrying artery should be exposed before separating the aneurysm to prevent the unpredictable sudden rupture of the aneurysm. In addition, huge arteriovenous malformations and resection of epileptic foci that require EEG monitoring during surgery are not suitable for choosing the micro-osseous approach.
2.Surgical method
The patient is placed in supine position. After intubation with general anesthesia, a lumbar puncture is performed and a drainage tube is placed in the subarachnoid space for backup. Generally, before cutting the dura, the subarachnoid drainage tube is released to release the cerebrospinal fluid and reduce the intracranial pressure. During surgery, when the brain retraction is satisfactory, the cerebral pressure plate can also be used without retraction to save operating space. Generally, the bone flap of the microperforated approach is about 2.5cm×3.0cm.
(1) Longitudinal fissure approach
(1) Longitudinal fissure approach: 10° of head droop and 10° of head turn to the opposite side of the tumor-carrying artery; 35° of head turn to the opposite side of the lesion in the pterygoid approach, and l0° of head droop and posterior extension, which facilitates the frontal lobe base to leave the skull base and reduce the intraoperative strain on the brain tissue. The bony window of the frontal longitudinal approach was located next to the right sagittal sinus, and the anterior edge of the window was against the base of the anterior cranial fossa. In this group, a traditional skin incision was used to turn over the skin (muscle) flap. After drilling a hole, the skull was opened with a milling knife micro-osseous. With the longitudinal fissure approach, the bone window is as close to the midline as possible; patients with large frontal sinuses are appropriately avoided to make full use of the longitudinal fissure space to expose the bilateral anterior arteries and anterior communicating arteries. If the frontal sinus is opened intraoperatively, it must be closed with bone wax and the frontal fascia is flipped and repaired.
(2) Inferior temporal locking foramen approach (pterygoid point approach)
The bone window is immediately adjacent to the skull base. After drilling the hole, the bone flap is cut with a milling knife. The operative field is flushed and the dura is cut along the base of the skull in an arc. The dura is draped over the soft tissue surrounding the bone window. Exploration is performed along the longitudinal or lateral fissure. To reduce the strain on the brain tissue, continuous drainage is performed via lumbar puncture while the lateral fissure pool is opened to release the cerebrospinal fluid and further reduce the cranial pressure.
(3) Supraorbital locking foramen approach (brow arch approach)
The patient is placed supine with the head frame fixed. The head is tilted back by l0° to 15° according to the lesion site, and the angle of rotation to the opposite side is 10° to 60° according to the lesion site, and a skin incision is made in the outer 2/3 of the brow arch, from the lateral aspect of the supraorbital foramen to the zygomatic process. The rotundus muscle was separated and pulled forward and downward, and the temporalis fascia and temporalis muscle were incised in the temporal line. The frontal fascia and periosteum were incised and separated toward the orbital rim. A hole is drilled in the frontal bone angle and a bone flap 2 to 3.5 cm long and 1.5 to 2 cm wide is formed with a milling knife. For basilar aneurysms, the orbital crest can be sawed off along with part of the orbital plate. The inner plate of the superior orbital rim window is smoothed to expand the field of view and facilitate surgical manipulation. The dura is cut in an arc and draped toward the superior orbital rim. The cerebrospinal fluid is released by opening the subarachnoid space or ventricles to reduce cerebral pressure, and the endoscope is placed under direct microscopic view and secured with a fixation device. The endoscope should be placed under direct microscopic view and secured with a fixation device. A surgical microscope should be used if possible, supplemented by a neuroendoscope only if necessary. After surgery, the dura should be tightly sutured to reposition and fix the bone flap and sutured in layers. The supraorbital foramen approach is suitable for anterior skull base, saddle area and interpeduncular pool lesions.
(4) Individualized surgical approach (personal approach)
The application of navigation technology provides a reliable guarantee for determining the surgical approach before surgery, especially for resection or biopsy of small intracerebral lesions, which cannot be done in traditional surgery. What is more critical is that the navigation technology can select the best surgical approach according to the different conditions (size and nature) of each patient’s lesion, narrowing the scope of craniotomy, reducing surgical injury, and completely changing the concept of traditional surgical craniotomy, which can be considered as designing a surgical approach for each patient, a hallmark of minimally invasive neurosurgery. Both the longitudinal approach and the pterygoid approach should first reach the saddle area under the operating microscope to identify the optic nerve and the internal carotid artery, and open the arachnoid membrane of the crossing pool to search for important anatomical structures such as the anterior and anterior communicating arteries, the internal and posterior communicating arteries and the middle cerebral artery along the internal carotid artery. During the exposure process, the angle of the operating microscope and the operating bed can be adjusted to obtain a satisfactory surgical field requirement.
3.Advantages of micro-osseous craniotomy
Compared with the traditional craniotomy, the advantages of micro-osseous maneuver are.
①Reducing the scope of craniotomy and reducing the exposure and disturbance to normal brain tissue.
②Use of normal intracranial anatomical gaps, such as the lateral fissure pool Longitudinal fissure approach, reducing the strain on the brain.
(3) Less surgical damage, thus reducing complications associated with traditional craniotomy, such as postoperative epilepsy and postoperative hematoma, and improving surgical safety.
④Shorten the opening and closing time of the skull and reduce surgical bleeding; ⑤Faster postoperative recovery of patients, shorten the postoperative hospitalization time and reduce medical costs.
4. Matters that should be noted when choosing the micro-osseous approach
The micro-osseous manway is a sign of minimally invasive surgery after the development of mature micro-neurosurgery technology, which makes micro-neurosurgery develop to a new height. The neurosurgeon who chooses the micro-osseous approach must have rich experience in microsurgery. Solid basic skills in microsurgery and the ability to independently handle accidents that may occur during surgery. In particular, intracranial aneurysm surgery requires basic experience in dealing with intraoperative aneurysm rupture. When choosing the micro-osteotomy approach, we should strictly follow the basic technical requirements of microsurgery and must have perfect microsurgical equipment and instruments, such as controlled surgical bed, high-speed cranial drill, head frame and fine surgical microscope. In order to adapt to the micro-osseous craniotomy operation, some special microdissectors and Perneczky aneurysm clips are required. These instruments are slender, take up little space and are easy to use. The micro-osseous maneuver demonstrates its advantages for improving the results of micro-neurosurgery and has a wide range of prospects, especially when applied to the removal of intracranial tumors with the support of new navigation techniques.