Following the maturation of classical neurosurgery in the 1950s, microscopic neurosurgery techniques rapidly developed and became popular in the second half of the twentieth century. In the 1990s, neurosurgery entered the era of minimally invasive surgery.
In 2001, at the “Seminar on New Concept of Minimally Invasive Surgery” held by the Chinese Academy of Engineering, experts proposed that minimally invasive surgery is the sublimation of surgery in the twenty-first century, and “minimally invasive” is the new realm pursued by surgery. Minimally invasive surgery is the new frontier of surgery. Any treatment measures to minimize the surgical damage of tissues, to release the patient’s lesions to the greatest extent possible, and to preserve the patient’s physiological functions to the greatest extent possible should belong to minimally invasive surgery. As a branch of neurosurgery, neurosurgeons treat neurological patients while minimizing trauma to the patient’s body surface and internal tissues, and make the utmost effort to pursue the belief of “minimally invasive” surgery, which is a new progress in the field of neurosurgery.
The rapid development of computer information technology, the research and application of the human genome project and neural stem cells have provided the material basis for the renewal of the concept of neurosurgery, providing new ideas and new means for neurosurgery and promoting the development of modern neurosurgery.
At present, minimally invasive neurosurgery includes techniques such as micro-osseous approach, neuronavigation surgery, neuroendoscopy, intravascular intervention, radiosurgery, neural stem cell research and application, and gene therapy.
I. Micro-osseous approach.
The micro-osseous approach uses a small incision (3.0 cm long) and a small bone window (2.5 cm × 3.0 cm), which does not affect the patient’s appearance and is the hallmark of minimally invasive surgery. This approach requires as precise as a keyhole for the localization of intracranial lesions. The surgical access is individualized to each patient and is designed to reach the intracerebral lesion area to achieve minimally invasive surgery. Minimal stretching of the brain tissue is the key to the minimally invasive technique. The cerebral cortex is very sensitive to strain, and when the pressure exceeds 20 mm Hg, cerebral blood flow is severely affected, leading to cortical ischemic infarction and cerebral edema, resulting in permanent postoperative neurological impairment such as hemiplegia and aphasia, and in severe cases, death of the patient. If the patient’s preoperative neurological status and imaging data are used to avoid important brain functional areas, open the arachnoid and ventricular brain pools to release cerebrospinal fluid, and make full use of the natural brain sulcus to separate the vascular nerves to reach the lesion area, the strain on the brain will be reduced and the medically induced brain tissue damage during surgery will be significantly reduced. Due to the small bone window, the opening and closing cranial time is shortened, intraoperative bleeding is less, postoperative complication rate is low, and patients recover quickly. It shortens the patient’s hospital stay and saves medical costs.
In recent years, high-quality imaging examinations such as CT, MR, positron emission tomography (PET), and super-selective catheterography (DSA) have made the localization and qualitative diagnosis of intracranial lesions more accurate, and can show the anatomical relationship around the lesions in detail. The high-tech achievements of related disciplines constantly update microsurgical instruments, which provide reliable technical support for micro-osseous access. The accurate positioning, orientation and real-time guidance of neuronavigation surgery provide reliable technical equipment for the micro-osseous approach. Since 1999, the Department of Neurosurgery of Tiantan Hospital of Capital Medical University has carried out more than 400 cases of micro-osseous approach and gained experience in the treatment of cerebral aneurysm, saddle area tumor and pontocerebellar tumor.
The application of minimally invasive neurosurgical approach requires a surgeon with rich clinical experience in microsurgery, as well as sophisticated and complete microsurgical equipment and a set of special surgical instruments designed for the microsurgical approach. The microforaminal approach is most suitable for extracerebral lesions, such as asymptomatic brain tumors and aneurysms. It is not suitable for huge cerebral arteriovenous malformation and epilepsy surgery.
Neuronavigation surgery
In 1998, the Department of Neurosurgery of Titan Hospital of Capital Medical University introduced navigation technology and performed more than 600 cases of intracranial tumor, cerebrovascular malformation and spinal surgery, which can safely remove lesions less than 2.0cm deep in the cerebral hemisphere without causing any neurological damage. It can safely remove lesions less than 2.0 cm deep in the cerebral hemisphere without causing neurological damage, and has accumulated experience in expanding minimally invasive neurosurgery.
The application value of neuronavigation surgery.
(1) Designing the surgical approach: Preoperatively, 3D images of the scalp, lesion, vessels and ventricular structures are obtained at the workstation to select the most ideal individualized surgical approach with the shortest possible surgical access, using the natural sulcus and fissure of the brain, reducing the flap area or using a micro-osseous approach to reduce brain exposure. The design of the approach can also be trained for young surgeons.
(2) Accurate excision of deep lesions: The navigation system can precisely locate small deep lesions preoperatively and guide discovery in real time intraoperatively, reducing blind probing damage to brain tissue and reducing postoperative neurological function damage.
(3) Displaying important intracranial structures: during craniotomy, especially skull base surgery, real-time understanding of the relationship between tumor and surrounding important neurovascular such as brainstem, internal carotid artery and basilar artery; when removing meningioma, glioma and pituitary tumor in cerebral hemisphere, probing the tumor boundary and verifying the resection range; displaying the position of frontal sinus and dural sinus to ensure the safety of craniotomy.
(4) Application in cerebral arteriovenous malformation and aneurysm surgery: Navigation can determine the vascular range of huge arteriovenous malformation and guide the separation and resection along the border of arteriovenous malformation, which can avoid hemorrhage of inadvertent lesions and prevent damage to brain tissue. Intraoperative navigation system provides real-time position of internal carotid artery and II and III cranial nerves; guides ventricular puncture when brain retraction is unsatisfactory; assists in judging the relationship between giant aneurysm and aneurysm-carrying artery to ensure the safety of aneurysm-carrying artery when clamping the artery.
(5) Biopsy and taking intracranial foreign body: the system is more convenient for positioning than those with frames, and can be used for biopsy, puncture of cyst (hematoma); positioning to take traumatic bone, foreign body.
Intraoperative drift of brain tissue can affect the navigation effect, which can be corrected by applying ultrasound and open MR to provide compensatory images. Magnetic Resonance Guided Intervention (MRI) is a procedure that uses an open MRI machine to provide real time guidance of MR images during craniotomy. Intraoperative imaging can be performed in real time, so that the operator is always aware of the surgical situation and can guide the direction and depth of the procedure. The magnet of the newly designed MRI machine gives the surgeon the space to operate directly within the magnetic field; the surgeon can not only operate directly or under a microscope, but also “see” the structures around the operative field through real-time MRI. The imaging characteristics of MRI allow the operator to instantly distinguish between normal and diseased tissue that is not readily identifiable to the naked eye; the operator can use an indicator to obtain interactive-real-time MRI images anywhere in the operative field. MRI combined with single photon scanning (SPECT), magnetoencephalography, and real-time ultrasound guidance for functional neurosurgery provides a comprehensive understanding of the biochemical changes in the tumor bed, a presumption of postoperative cerebral circulation, and an effective reduction of surgical complications. It has a broader prospect in terms of understanding the biochemical changes in the tumor bed, predicting the postoperative cerebral circulation status, and effectively reducing complications. At present, MRI-guided interventional techniques are still in the early stage of clinical application, and more than 1000 cases of open MRI surgery have been reported by 15 research centers worldwide.
Third, the auxiliary role of neuroendoscopy in minimally invasive surgery
Endoscopic-assisted microsurgery can be used to treat intracranial arachnoid cysts, intraventricular cystic lesions, intracerebral parenchymal cystic lesions, and transsphenoidal resection of intra-saddle lesions, which can achieve good results.
The endoscope is suitable for operating in narrow cavities and orifices; the clarity of the deep surgical field of the endoscope is significantly better than that of the operating microscope, which can observe the nerves and blood vessels more clearly; the endoscopic view tube itself can have a lateral view, so that the internal lateral structures of the lesion can be identified when reaching the lesion, and the residual tumor in the blind area of microsurgery can be observed, which expands the visualization range and increases the accuracy of surgery, and plays an auxiliary role for minimally invasive surgery. The procedure can be performed with the aid of a minimally invasive surgery. The use of neuroendoscopy during direct craniotomy for aneurysm clamping provides the operator with a view of the aneurysm and the dorsal aspect of the aneurysm-planted artery, avoiding inadvertent injury to important arteries. In the case of cholesteatoma growing between the nerve and the blood vessel, neuroendoscopy can fill in the gap of residual tumor in the corners that cannot be seen by conventional microsurgery. The application of neuroendoscopic-assisted surgery only requires cranial drilling or small craniotomy and placement of the neuroendoscope, which is simple to operate, with little surgical damage, minimal postoperative reaction, and quick recovery of the patient.
However, neuroendoscopic surgery has a small field, little space for operation, and poor ability to cope with surgical accidents, especially when there is more bleeding in the operating area, which is more difficult to handle and extremely risky. Surgical guidance is also a problem that needs attention. Therefore, it is difficult to remove intracranial tumors by neuroendoscopy alone. There are only case reports of transsphenoidal resection of saddle node meningioma in foreign countries. When applying neuroendoscopic-assisted surgery, the operator is required to first have proficient microsurgical skills and be well trained in endoscopic operation.
IV. Gene therapy
The greatest project in human history, the Human Genome Project, is not only to decipher the code of human genes, but more importantly to find ways to prevent and treat diseases at the molecular level. The development of cellular and molecular biology has made gene therapy possible in the central nervous system, called cellular molecular neurosurgery. On the one hand, there is the identification of genes responsible for neurosurgical diseases. Neurological disorders that have been identified as genetic disorders such as lysosomal storage disorders, Sandhoff’ syndrome, Lesch-Nyhan’ syndrome, Mucopolysaccharidosis ‘syndrome, cerebral cavernous hemangioma, neurofibromatosis, etc. Beijing Tiantan Hospital has explored the causative genes of human cerebrovascular diseases such as cerebral aneurysm and cerebral cavernous hemangioma, and has now found mutation loci for the causative genes of cerebral cavernous hemangioma in Han Chinese.
On the other hand, gene therapy for neurological disorders is mainly in the following areas.
1. Total gene replacement of cells in the central nervous system for the correction of hereditary neurodegenerative pathologies such as enzyme dysfunction, such as the treatment of lysosomal storage disorders. Whole gene replacement for enzyme dysfunction requires a viral vector system capable of non-toxic long-term gene expression in neuronal and glial cells, neural stem cells capable of acting as a vector for gene therapy, and gene replacement with normal alleles, which can effectively eliminate dominant manifestations of disease in the CNS caused by recessive mutations in a single gene.
2. Gene therapy to restore cellular functions at specific locations in the CNS is used to restore the functions of specific subpopulations of neural cells that were lost during neurodegeneration. The transfer of viral vector-mediated therapeutic genes to site-specific subpopulations of neuronal cells in the brain, with tight regulation of gene transcription and protein expression, can be used to restore function to specific sites of neurodegenerative lesions. Alternatively, transplantation of genetically altered cells or embryonic grafts can produce specific neurotransmission or growth factors to restore neurological deficits in specific parts of the central nervous system caused by neurological dysfunction. For example, gene therapy for Parkinson’s disease and Alzheimer’s disease.
3. Gene therapy for brain tumors. Gene therapy for brain tumors requires that the transferred genes have special anti-tumor effects, which can selectively express toxic genes, cause lysis and necrosis of tumor cells, inhibit tumor growth, and finally kill the tumor without causing damage to normal brain tissue. Compared with traditional tumor treatment methods, the combination of surgery, radiotherapy and gene therapy can prolong the survival of patients with certain tumors, and immunotherapy can also be used to improve the efficacy of treating certain specific tumors.
4. Gene therapy for stroke. Gene therapy for stroke introduces therapeutic genes that can protect ischemically damaged nerve cells from apoptosis and genes that control the expression of different inflammatory regulators in the brain. 3-5 weeks of transient gene expression is beneficial for the normal repair process and angiogenesis in ischemic diseases and can achieve therapeutic goals.
V. Research and application of neural stem cells. Neural stem cells have two distinctive features: first, they have a high degree of self-renewal ability and can repeatedly undergo mitosis to produce a large number of daughter cells; second, they can differentiate into neural cells and glial cells under certain conditions. Currently, neural stem cells have three uses. First, they are used for replacement therapy of damaged neural cells. Transplanting neural stem cells into the central nervous system to replace nerve cells that are missing due to injury or disease is important for restoring their functions. The second is to act as a vehicle for gene therapy. Third, it is applied to research in life sciences. At present, it has been possible to expand human neural stem cells to a considerable number in vitro and maintain their ability to add value for a certain period of time, but the regeneration of cells in the central nervous system is a very complex process, and the application of neural stem cells in the clinic still requires a lot of preliminary work.
The emergence of new knowledge and new technology has promoted the change of the concept of neurosurgical treatment, and the change of the concept of neurosurgeons will certainly enrich the knowledge and experience of neuroscience and will promote the progress of the discipline of neurosurgery. It is believed that in the new century, with the rapid development of our economy, the neurosurgery in China will reach the advanced level in the world.