Neuroendoscope can be a safe and helpful adjunct in many microneurosurgical procedures. Lespinasse[1] and Dandy[2] both reported their early experiences utilizing endoscopic methods as a means of diagnosing intracranial pathology. In different periods, technological capabilities of the time, have led to renewed interest in expanding the possible applications of endoscopic methods in neurosurgery. This was evident in the 1970s when Fukushima developed a motorized, steerable, flexible endoscope and explored the cerebellopontine angle.[3,4] Again, in the late 1980s and early part of this decade, equipment designed to handle the problems of hemostasis and improved optics has led to another resurgence of interest in these methods.[5-9] The introduction of the endoscope has revolutionized the approach to certain tumour types by allowing safe and radical removal. In fact, poor visualisation is what limits adequate and safe removal of tumour. With the endoscope the occult parts of the tumour can be removed under vision making this part of the tumour as accessible as the directly visualised portion. Because the prognosis for a number of tumours depends on the adequacy of tumour removal, the use of the endoscope in this fashion to obtain the best removal possible and to document that removal is highly recommended. The development of fine endoscopes with strikingly clear optics is currently leading to interesting possibilities in their use as adjuncts to procedures utilizing the microscope.[8,9] Intrigued by the possible adjunctive uses of the endoscope during micro neurosurgical procedures, we undertook this study to evaluate the advantages of endoscopy assisted cranial microneurosurgery in neoplastic lesions.

This prospective observational study was carried out in the Department of Neurosurgery, over a period of 24 months, after obtaining approval from the Institutional ethical Committee. Study included all the admitted patients with intracranial space occupying lesions and intracranial aneurysms who underwent which micro neurosurgical techniques during study period. Patients with contraindications to various radiological investigations which are necessary for endoscopy assisted micro neurosurgery, and unwilling patients were excluded from the study. Written informed consent was obtained from each patient prior to their enrolment in the study. Sociodemographic data of patients were noted in a predesigned proforma. Study parameters included size of craniotomy, complex anatomy incidence and identification, visualization of inaccessible parts of tumours and confirmation of contralateral extent of tumour resection (in cases of intracranial tumours). All the patients had undergone MRI brain (plain + contrast) and MR spectroscopy of the brain lesion and Neuro navigation DICOM protocol in cases of intracranial space occupying lesions. Data thus collected was subjected to statistical analysis and results were drawn.

In this study, majority of patients were below 40 years of age (21), with median age of 38.5 years. Amongst the study group 55% (n = 22/40) of the patients were females, with a Male: Female ratio of 1: 1.22. Most of the pathologies were found in posterior (17) and middle cranial fossa (10). Of 40 patients, pathology was neoplastic in nature in 29 patients, who were further analysed. (Table 1)

Table 1: Demographic and Clinical Profile of Study Patients

Cerebello-pontine angle was the most common radiological location of tumor, (Figure 1,2) and Meningioma was the commonest pathological diagnosis (7), followed by glioma (5). Most common anatomical position of ventricular tumor was 3^rd and 4^th ventricle.  (Table 2)

Table 2: Radiological and Pathological Details of Neoplastic lesions in Study Patients

Neuronavigation was utilized in 15 patients, and angiogram/venogram were used in 21 patients in this study. Early post-operative MRI enhancement was observed in 13 patients, while residual tumor on late post-operative MRI was observed in 10 patients. (Table 3)

Table 3: Intra-operative and Post-operative Parameters in Study Patients

Intra-operative injury and associated post-operative deficit were observed in total 8 patients, among which 6 patients had neoplastic lesion and 2 patients had non-neoplastic lesions. Details of intra-operative injury and associated post-operative deficit associated with neoplastic lesions are presented in Table 4.

 Table 4: Details of Intra-operative injury and associated post-operative Neuro-deficit in Patients with Neoplastic lesion

Gross total resection was performed in a total of 14 patients with Endoscopic assisted resection done in 12 cases. (Figure 3)

Apuzzo M et al[10] were the first to apply neuroendoscopic techniques to craniotomy. Deep structures can be seen through the endoscope with minimal or no brain retraction. By alternating the use of endoscope with the operating microscope, one can improve the visualisation of the deep anatomy during craniotomy. It is prudent to inspect the position of the endoscope frequently during the dissection to maintain overview of the entire operative field and avoid complications of injuring the surrounding structures by the endoscope itself. The use of a picture in picture device allows the operator to view both the images on one screen. Taneda M et al[11] developed a display system that permits the surgeon to watch the endoscopic image through one of the ocular lenses of the surgical microscope. This study was done to evaluate the advantages of endoscope assisted cranial microneurosurgery in neoplastic lesions.

In our study, a wide range of neurosurgical diseases were included with the median age of study patients being 38.5 years, and majority were ≤40 years.  Galzio RJ et al[12] have observed a mean age of 49.5 years in their results from a 10-year long study observing 181 patients, which is higher than our study. This may be because their study did not

include any pediatric patients.. The male: female ratio in our study was 1:1.22, suggesting female dominance. Similar observations were made in the study by Takaishi Y et al[13].

In our study, 54.80% had isolated posterior cranial fossa diseases, followed by middle cranial fossa lesions (32.25%), 22.5% of patients had anterior cranial fossa lesions, while 12.90% had pathology occupying middle as well as posterior cranial fossa. Thus, majority of patients (77.5%) had middle and posterior cranial fossa lesions. However, Attia M et al[14], found equal distribution of lesions in each of the anterior, middle and posterior cranial fossae in their study, which was focused on middle and posterior cranial fossa lesions. In our study, neoplastic lesions were found in majority of patients (72.5%) and non-neoplastic lesions (vascular and others) were found in only 27.5% of patients. Patients with neoplastic lesions were further analysed in detail.

We evaluated 29 neoplastic lesions of brain including skull base as well as cortical and ventricular pathologies. The most commonly observed location in our study was Cerebello–Pontine angle (24.13%). Yang Shi-Ming et al[15] observed 25 cases in their study over 6 years and found a total of 19 cases of vestibular schwannomas and other 6 cases pertained to Cerebello–pontine region meningiomas and epidermoid tumors in this region. In this study, two tumors were in lateral ventricle, 5 tumors were in 3rd ventricle and pineal region. Among the Lateral ventricular tumors, one was central neurocytoma and one was astrocytoma, whereas 3rd ventricular and pineal tumors included Germ cell tumors, meningioma, anaplastic ependymoma, etc. in a similar study, Kamal HM et al[16] found that of 23 cases, 8 cases were 3rd ventricular tumors and 15 cases were lateral ventricular tumors. They came across most cases of ependymomas followed by oligodendroglioma and astrocytoma. Their study did not involve any intra ventricular meningiomas unlike us.

In our study, the cohort consisted of 29 neoplastic lesions with variable distribution in the skull. It was observed that the most common location was the Cerebello – Pontine angle, contributing to 24.13% (n = 7) cases. Yang Shi-Ming et al[15] observed 25 cases in their study over 6 years and found a total of 19 cases of vestibular schwannomas and other 6 cases pertained to Cerebello – pontine region meningiomas and epidermoid tumors in this region. Authors have observed a total of 2 tumors in the lateral ventricle and 5 tumors in the 3rd ventricle and pineal region. Lateral ventricular tumors were found to be one case of central neurocytoma and one case of astrocytoma. 3rd ventricular and pineal tumors were found to include Germ cell tumors, meningioma, anaplastic ependymoma, etc. Kamal HM et al[16] studied the role of endoscopic-assisted transcortical microsurgery in resections of 3rd ventricle tumors and in their course of retrospective study, they analyzed 23 patients with 8 cases of 3rd ventricular tumors and 15 cases of lateral ventricular tumors. They came across most cases of ependymomas followed by oligodendroglioma and astrocytoma. Their study did not involve any intra ventricular meningiomas unlike us.

In our study, we observed 29 cases of neoplastic diseases, with Meningiomas being the most common diagnosis (24.13%). One analysis of 380 patients treated with endoscopic-assisted micro neurosurgery showed 53.94% had tumors,[17] which is lower than our study's 72.5%, highlighting variability in neurosurgical classifications. Meningiomas were the most common tumors in our study. In the study by Gardner PA et al[18], of  the 35 patients with anterior skull base meningiomas 33% had olfactory groove, 33% had sellar and suprasellar, and 33% had petro-clival meningiomas.

In our study, neuronavigation was utilized in 37.5% of cases, primarily for deep-seated conditions such as lateral and third ventricular tumors and sellar tumors, resulting in reduced patient morbidity. Schroeder HW et al[19] emphasized the advantages of frameless neuronavigation, suggesting it enhances surgical outcomes by improving accuracy and minimizing patient morbidity. The authors addressed a wide range of pathologies involving various surgical corridors, with Pterional Craniotomy being the most frequently used approach (30%). Patra Charalampki et al[20] reported on 35 patients with tumors in the lateral and third ventricles, noting that endoscopic-assisted micro neurosurgery improved outcomes using trans-cortical, trans-callosal, sub-occipital, trans-tentorial, or supra-cerebellar infratentorial approaches.

We found that endoscopic-assisted surgeries not only enhanced pathology delineation but also revealed anatomical variations, which were present in 30% of the study patients. Our study also included five cases of posterior third ventricle or pineal region tumors, two of which had a steep tent. Liu JK noted that the angle of the straight sinus and tentorium cerebelli often influences the surgical approach to the pineal region.[21] In addition to various clinical and radiological parameters, the authors focused on an important variable relevant to modern neuro-oncology: gross total resection, which was achieved in 48.27% of the 29 neoplastic cases, with 85.71% of these cases underwent endoscopic-assisted resection. Another key finding was the identification of intra-operative injuries to adjacent structures, with an injury rate of 25%. Giorgio F et al[22] found that compared to the open surgery cohort, the endoscopic group had a significantly higher percentage of gross total resection (61.0% vs. 48.1%; p=0.010) and fewer cranial nerve deficits (1.3% vs. 24.2%, p<0.001).

Attempts by neurosurgeons to preserve function may lead to residual lesions or early recurrence. In our study, contrast-enhanced MRI was performed within the first 48 hours post-surgery to check for early post-operative enhancement. Early enhancement was observed in 44.82% of patients, while late enhancement suggesting residual tumor was seen in 43.47%, with six cases awaiting delayed scans. Vidiri A et al[23] studied 42 glioblastomas and 5 anaplastic astrocytomas operated by the same surgeon and found that 63.82% of cases showed enhancement within 24 hours of surgery.

Improved illumination and vision of endoscopes has led to the possibility of working in the brain parenchyma. The concept of a keyhole craniotomy combined with a selected trajectory enables the endoscopic approach of intra-parenchymal lesions with an assisted navigation system. Partial or total lesion removal may be achieved depending on the nature of tumor. The endoscope is a useful adjunct to the microscope in anterior skull base surgeries, posterior fossa approaches, and aneurysm surgery. The microscopic approach makes dissected structures visible in a straight line with the great advantages of high resolution, excellent color fidelity, and stereoscopic vision. For working “around a corner,” the endoscope is applied to reduce retraction and skull base drilling.

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