| objetive:Currently, endoscopic third ventriculostomy (ETV) is widely used to treat hydrocephalus due to aqueduct obstruction. However, it still carries a risk of such serious complications as rupture of the basilar artery and injuries to the hypothalamus. A failure of ETV occurred more often in infants younger than6months of age. Endoscopic aqueductoplasty (EA) has gradually become an alternative treatment for obstructive hydrocephalus. However, there have been very few studies on aqueductoplasty. There have been fewer than50reported cases since the1990s and the average follow-up period was less than3years and the success rate ranged from30-100%. EA candidates must be selected very carefully and longer follow-up periods are necessary to evaluate long-term aqueductal patency after aqueductoplasty. Endoscopic aqueductoplasty may become an alternative option for patients with obstructive hydrocephalus due to aqueduct stenosis. However, it is essential to establish an appropriate method to control surgical indications before the operation and to evaluate effectiveness after the operation. In patients with hydrocephalus due to aqueduct obstruction, errors may inevitably occur with general imaging tests for preoperative assessment. Additionally, determination of aqueduct obstruction status by relief of clinical symptoms following treatment is not reliable. Over the past2decades, the technology of phase-contrast cine magnetic resonance imaging (MRI) has been used to study the physiological state of the cerebrospinal fluid (CSF) circulation, to diagnose hydrocephalus, and to evaluate the efficacy of third ventriculostomy. It has been widely embraced by clinicians because it is non-invasive and highly sensitive. We used phase-contrast cine MRI for preoperative diagnosis of obstructive hydrocephalus and postoperative follow-up, and achieved a satisfactory outcome.Materials and methods23patients underwent aqueduct reconstruction. The standards for choosing the acqueductoplasty are the followings:1:all aqueduct membranous obstruction or short stenosis cases.2:the cases with the floor of the ventricle structure showed unclear or the floor thickens significantly (tough and not easy to penetrate).21cases were simple membranous obstruction at the aqueduct fistula level or short aqueduct stenosis and2cases were hydrocephalus due to intraventricular hemorrhage. In these latter2cases, symptoms could not be relieved by third ventriculostomy and consequently the aqueduct was reconstructed by endoscopic aqueductoplasty. In total, there were10male patients and13female patients with an average age of10.5years (3months to67years). Before surgery, clinical symptoms included headache, nausea, vomiting, blurred vision, instability of movement, increased head circumference, and loss of consciousness. A preoperative phase-contrast cine MRI scan confirmed aqueduct obstruction and cessation of CSF flow in the aqueduct.2. Phase-contrast cine MRI scan All subjects underwent conventional head MRI examination, including T1WI, T2WI, and FLAIR sequence (GE1.5T Signa Horizon MRI system GE Healthcare in US). TSurgical equipmentSurgical equipment included a3.8-mm Rudolf-Fujinon soft electronic endoscope (Fujifilm Corporation in Japan)and matched single and bipolar coagulation devices, biopsy forceps and scissors, and a2F Fogarty balloon catheter.4. Surgical procedureUnder general anesthesia patients were placed supine with a30°head tilt. A scalp incision was made above the forehead hairline and2cm from both sides of the median line. The skull was drilled a2cm hole and a sheath was used to puncture the lateral ventricle. A ventriculoscope was inserted into the ventricle to view the aqueduct fistula. The catheter was pushed through the membranous obstruction and short aqueduct stenosis so that the balloon part was placed at the lower fistula of the aqueduct. The balloon was filled with0.1-0.2ml of normal saline to expand the aqueduct up to a diameter of4mm(Fig1). Then the endoscope was inserted further into the fourth ventricle to explore whether the fourth ventricle opening was obstructed.ResultsComplete aqueduct obstruction was revealed by preoperative phase-contrast cine MRI in23patients During surgery, membranous obstruction at the upper aqueduct stenosis and short aqueduct stenosis were found in21patients. In2patients with intraventricular hemorrhage, the opening of the upper aqueduct was occluded by old blood clots. About one week following surgery, the CSF flow volume and velocity at the aqueduct opening level measured by phase-contrast cine MRI showed smooth CSF flow.The postoperative image CSF flow signal-void phenomenon was found in14patients.The average peak flow velocity was4.74±1.77cm/s and the typical flow velocity waveform for each cardiac cycle was two-way flow. In21patients with simple membranous obstruction or short aqueduct stenosis symptoms did not recur during follow-up. Ventricular size, especially regarding the third ventricle, was reduced in8patients;there was no change in15patients. Sixteen patients were followed up for more than one year and MRI scans in these patients after one year suggested that the CSF flow was smooth. The average peak flow velocity was4.28±2.17cm/s. The flow velocity waveform for each cardiac cycle was bi-directional. Symptoms recurred during follow-up in2patients with hydrocephalus due to intraventricular hemorrhage. One had symptoms of intracranial hypertension one month after aqueductoplasty. MRI showed that there was no CSF flow in the aqueduct and a second endoscopic examination revealed that the aqueduct opening was covered by old blood clots and proliferative ventricular membrane. After the obstruction was relieved, the aqueduct was observed as clear on repeated phase-contrast cine MRI. In another patient, symptoms of intracranial hypertension recurred3months after aqueductoplasty. Cerebrospinal fluid flow in the aqueduct was not be seen on phase-contrast cine MRI and a second endoscopy examination revealed that restenosis had occurred in the aqueduct. The aqueduct was expanded and then a stent was placed in the aqueduct and the symptoms were relieved. DiscussionIn conclusion, endoscopic aqueductoplasty is an important alternative in the treatment of obstructive hydrocephalus when third ventriculostomy is difficult. However, due to the lack of large sample size and long-term postoperative follow-up, it is necessary to evaluate and follow up every patient. The technology of phase-contrast MRI has been used to study CSF circulation for more than20years and has also been widely used for clinical diagnosis of hydrocephalus.The magnetic resonance cine imaging can determine whether the aqueduct is opened after the acqueductoplasty, with the nontraumatic, simple, reliable characteristics. |
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