Asymmetric hydrocephalus, also known as unilateral lateral ventricular dilatation, is caused by unilateral lateral ventricular dilatation following unilateral interventricular foramen occlusion, or “unilateral lateral ventricular hydrocephalus”. This is a less common complication after lateral ventricular tumor resection. Classical treatment often involves making a small incision in the cerebral cortex and then accessing the ventricles with the help of a microscope to open up the pellucid septum. Although it is not too traumatic with the help of a microscope, can it be any smaller? The application of neuroendoscopy for hyaloid septal fistula by Zhou Yan of the Department of Neurosurgery at the Air Force General Hospital is a minimally invasive method for treating this disease. Of course, it is important to make sure that the contralateral interventricular foramen is patent before the procedure is performed. So, is this procedure really less invasive than microscopic surgery? Can it achieve the same results as microscopic surgery? Is this minimally invasive neuroendoscopic surgery risky? I will first describe the procedure as usual, from which the answer may be found. The head is placed in the supine position with 30° of forward flexion. The cranial borehole should be located 5-6 cm anterior to the coronal suture and next to the midline. neuronavigation helps to determine it more precisely. The position of the hyaline septal fistula is not fixed and needs to be set according to individual anatomical features. In patients with chronic hydrocephalus, the septum is generally thin and transparent, allowing for easy identification of the avascular area suitable for fistulae. In patients with acute hydrocephalus, the septum is thick and opaque. The intermittent perfusion shock method helps to identify the thinnest part of the septum. Care is taken to avoid damage to the fornix. Circumferential cautery with bipolar electrocoagulation is performed on the septal fistula area. The tissue “bridge” between the cauterized areas is then cut with microscissors, but one intact “bridge” (and only one) needs to be preserved as a “tip” to avoid intracerebroventricular drift of the fistula flap. This is to avoid intracerebroventricular drift. Finally, the fistula flap is removed by grasping it with microscopic forceps and cutting the last “bridge”. The circumference of the fistula is cauterized to stop the bleeding. The diameter of the fistula should be 7-10 mm to avoid closure of the fistula due to scarring (especially for thicker hyaline septa). Here is a case to better understand this surgical approach: 47-year-old male patient with a diagnosis of “right thalamic fibroblastic astrocytoma”. He was discharged from the hospital with a good recovery. However, one month after surgery, the patient developed severe progressive walking instability, headache, and fine motor deficits, and MR showed significant dilation of the temporal and occipital horns of the right lateral ventricle. The ideal surgical path was determined with the help of neuro-navigation. The neuroendoscope was introduced into the dilated occipital horn of the lateral ventricle, and the only anatomical landmark that could be identified was the internal cerebral vein. With the guidance of neuronavigation, the optimal location zone for a hyaloid septal fistula is identified. The thinnest location of the septum pellucidum is then identified using intermittent perfusion shocks. The fistula opening is cauterized with bipolar electrocoagulation, and then a 30° endoscope is introduced through the fistula opening to probe the contralateral ventricular cavity, and the exact location of the fistula is determined by identifying the choroid plexus in the contralateral ventricle. The fistula can now be enlarged with bipolar electrocoagulation in a circumferential cautery fashion. The tissue “bridge” between the cautery sites is then cut with microscissors, but one intact “bridge” (and only one) needs to be preserved as a “tip” to avoid intraventricular drift of the fistula flap This is to avoid intracerebroventricular drift. Finally, the fistula flap is grasped with microscopic forceps and the final “bridge” is cut to remove the fistula flap intact. The circumference of the fistula is cauterized to stop the bleeding. A 30° neuroendoscope was introduced through the fistula into the contralateral lateral ventricle to visualize the choroid plexus and choroid plexus veins. Postoperatively, the patient’s symptoms improved significantly. Postoperative MR clearly showed a significant reduction in the dilatation of the right lateral ventricle and satisfactory opening of the hyaloid septal fistula.