Introduction of several experiences in the treatment of secondary hydrocephalus
Hydrocephalus is a common and frequent disease in neurosurgery and can be primary or secondary to other intracranial diseases. When hydrocephalus exists or is expected to occur in combination with intracranial tumors or other diseases, physicians should consider hydrocephalus treatment strategies when formulating treatment plans. The following is the author’s experience in the treatment of several types of secondary hydrocephalus for the reference of fellow physicians.
I. Transparent septal fistula during resection of deep tumors near the interventricular foramen or in the midline
Tumors in the deep intracranial midline area, especially near the interventricular foramen, often lead to unilateral ventricular enlargement and asymmetric hydrocephalus after surgery due to edema or blood clot blockage of the interventricular foramen on one side. Sometimes, when the interventricular foramen is blocked bilaterally, the contralateral ventricle may not be able to drain the cerebrospinal fluid while the ventricle is still dilated when a ventriculoperitoneal shunt is performed. In this case, the contralateral ventricular-peritoneal shunt should be performed again, or the contralateral ventricular tube should be connected to the ventral tube of the original ventricular-peritoneal shunt system with a “Y” shaped connector. This can be avoided by performing a septal fistula incidentally to the tumor resection. The fistula site should be chosen in the clear septum without veins, and the double membrane of the clear septum should be opened, and the fistula opening should be about 2-3 mm in diameter. The average anterior and posterior diameter of the septum pellucidum is 41 mm, with an average height of 14 mm at the interventricular foramen, 10 mm at the frontal horn, and 8 mm at the atrium of the lateral ventricle; one to three septal veins are visible on the surface of the septum pellucidum, and there are no arteries. It is important to identify the anatomical landmarks of the interventricular foramen, choroid plexus, thalamic vein, and septal vein during the operation, and not to injure the veins, especially the thalamic vein, as this can have serious consequences.
After a hyaline septal fistula, hydrocephalus will not occur as long as the interventricular foramen on one side remains patent. If both interventricular foramina are blocked and hydrocephalus occurs, only a lateral ventriculo-abdominal shunt should be performed without worrying about asymmetric hydrocephalus.
Torkildsen shunt in the first stage of modified Poppen approach surgery for pineal tumor
Tumors in the pineal region often lead to obstructive hydrocephalus, and even if the tumor is removed, the hydrocephalus still cannot be relieved in 12%-81% of patients after surgery, and further surgical intervention is needed. The reasons for this are.
(1) bleeding in the operative field and surrounding brain tissue edema.
(2) Incomplete tumor resection or postoperative recurrence.
(3) adhesions of the midbrain aqueduct due to tumor compression.
In addition, common tumors in the pineal region are germ cell tumors, pineal cell tumors, and glial tumors, which vary in malignancy and have the possibility of recurrence even with total resection, and lead to the reappearance of hydrocephalus. To date, it is still controversial how and when to deal with secondary hydrocephalus in pineal region tumors. Preoperative ventriculo-abdominal shunts have been performed, but about 20% of patients require shunt adjustment after surgery; others perform extraventricular drainage and remove the drain after a few days. The problem with this is that if the obstruction is not relieved, the hydrocephalus cannot be relieved and a second stage ventriculo-abdominal shunt is forced to be performed.
The author’s conventional surgical approach to deal with pineal tumor is: a modified Poppen approach to remove the tumor and a stage I Torkildsen shunt (i.e. lateral ventricle-occipital pool shunt).
The patient is placed in a prone position with the head staple in place and a small surgical tray placed on the right side of the patient’s head, which allows the operator to change position between the top and left side of the patient’s head. A horseshoe-shaped flap was made in the left occipital region, and the medial incision was extended along the midline down to the occipital foramen magnum, the occipital free bone flap was made, the sagittal sinus was revealed medially, the transverse sinus was revealed on the inferior edge, the dura was cut, and the ventricle was punctured 3 cm lateral to the midline in the posterior part of the parietal lobe before the tumor was revealed. After entering the ventricle and removing the needle core, the catheter enters the cortex at a depth of about 10 cnl, the cephalic end is in the frontal horn, and the cerebrospinal fluid is released. After the tumor is removed, the dura is sutured, then the occipital foramen is revealed, the bone at the posterior margin of the occipital foramen is removed, the dura and arachnoid are incised, and the dura and arachnoid are clamped at the same time with vascular forceps on both sides.
Torkildsen shunt is performed in the first stage of modified Poppen approach for pineal region tumors with the following advantages.
(1) Torkildsen shunt drains cerebrospinal fluid from the lateral ventricle to the occipital pool, simulating the natural circulation of cerebrospinal fluid.
(2) Simultaneous surgery can effectively relieve postoperative hydrocephalus and avoid acute worsening of the patient’s condition due to acute hydrocephalus after surgery, and the cost and risk are greatly reduced compared to secondary surgery.
(3) The shunt is placed in the frontal horn, which is less likely to be infiltrated by blood and tumor, and the shunt is less likely to be wrapped by the choroid plexus.
(4) The remission rate of hydrocephalus is higher than other surgical procedures. From 1997 to 2010, Torkildsen shunts were performed in 35 patients with tumors in the pineal region at the same time during tumor resection with good results.
III. Direct ventriculo-ventricular shunt for intracerebroventricular hemorrhage combined with hydrocephalus
The risk of shunt blockage is the most common complication of ventriculo-abdominal shunt, especially when the cerebrospinal fluid contains more red blood cells or proteins. reddy reported that 51.9% of patients required shunt adjustment after hemorrhagic-associated hydrocephalus shunt, while only 18% of patients required shunt adjustment after spontaneous hydrocephalus shunt. brydon et al. Brydon et al. examined 43 valves replaced during shunt adjustment and found that 80% of the valves with metal had debris deposits, while 20% of the valves without metal had debris deposits, thus suggesting that all valves should be replaced during shunt adjustment. In fact, many clinicians base the timing of shunt procedures on the number of erythrocytes in the cerebrospinal fluid. The Cleveland Clinical Center considers erythrocytes <2 000/μl to be a safe indicator for performing ventriculo-abdominal shunts.
Cranial trauma, cerebral hemorrhage, smog, ruptured aneurysm, and intracerebroventricular tumor resection can lead to intracerebroventricular blood accumulation, blocking cerebrospinal fluid circulation pathways, which in turn can cause acute hydrocephalus and endanger life. In this case, the conventional treatment is extraventricular drainage, sometimes even intracerebroventricular injection of urokinase is required to accelerate the dissipation of the clot. However, it is difficult to predict when the clot will completely dissipate, when the cerebrospinal fluid circulation will be restored, and whether the external drainage and intracerebroventricular injection will be complicated by central nervous system infection. In Kang et al, it took 6.4 d to convert the external drainage to ventriculo-abdominal shunt. In general, extraventricular drains should not be placed for more than 1 week, and if the cerebrospinal fluid circulation system is still not opened after 1 week, the extraventricular drain needs to be repositioned on the affected side. However, as the duration of extraventricular drainage increases, the likelihood of infection increases, and Bota et al. reported that the rate of infection associated with extraventricular drainage ranged from 0% to 22%, with a linear increase in the rate of infection from 3 to 9 d postoperatively. Once hydrocephalus is combined with CNS infection, treatment is quite challenging and there are no particularly effective control options. If a ventriculoperitoneal shunt is performed early to reduce the risk of infection, the possibility of blockage is very high due to the high level of erythrocyte breakdown and high protein in the cerebrospinal fluid.
In order to perform ventriculo-abdominal shunt as early as possible to avoid infection caused by external drainage and to reduce the risk of shunt blockage, the author performed direct shunt in patients with intraventricular hemorrhage combined with hydrocephalus, i.e., the valve was removed and the shunt at the ventricular end and the abdominal end were directly connected, so that the cerebrospinal fluid in the shunt could maintain a certain flow rate and flow, so that the cerebrospinal fluid could not be retained in the shunt and red blood cells and proteins This greatly reduces the risk of shunt blockage. It usually takes 40–50 days for the cerebrospinal fluid to return to normal, at which time the valve can be installed under local anesthesia. This has been shown to be a proven method for resolving intraventricular hemorrhage combined with obstructive hydrocephalus. Most of the patients who need direct shunts are very sick and have difficulty getting up in the short term, so the possibility of hypocranial pressure syndrome is not too high. And if hypocranial pressure syndrome occurs, getting up can be minimized and valve placement can be performed as soon as possible when cerebrospinal fluid properties are approximately normalized.