Use of a simple intraoperative hydrostatic pressure test to assess the relationship between mobility of the ventricular stoma and success of third ventriculostomy

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Neuroendoscopists often note pulsatility or flabbiness of the floor of the third ventricle during endoscopic third ventriculostomy (ETV) and believe that either is a good indication of the procedure's success. Note, however, that this belief has never been objectively measured or proven in a prospective study. The authors report on a simple test—the hydrostatic test—to assess the mobility of the floor of the third ventricle and confirm adequate ventricular flow. They also analyzed the relationship between a mobile floor (a positive hydrostatic test) and prospective success of ETV.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>During a period of 3 years between July 2001 and July 2004, 30 ETVs for obstructive hydrocephalus were performed in 22 male and eight female patients. Once the stoma had been created, the irrigating Ringer lactate solution was set at a 30-cm height from the external auditory meatus, and the irrigation valve was opened while the other ports on the endoscope were closed. The ventricular floor ballooned downward and stabilized. The irrigation valve was then closed and ports of the endoscope were opened. The magnitude of the upward displacement of the floor was then assessed. Funneling of the stoma was deemed to be a good indicator of floor mobility, adequate flow, and a positive hydrostatic test. All endoscopic procedures were recorded using digital video and recordings were subsequently assessed separately by two blinded experienced neuroendoscopists. Patients underwent prospective clinical follow up during a mean period of 11.2 months (range 1 month–3 years), computerized tomography and/or magnetic resonance imaging studies of the brain, and measurements of cerebrospinal fluid pressure through a ventricular reservoir when present. Failure of ETV was defined as the subsequent need for shunt implantation. The overall success rate of the ETV was 70% and varied from 86.9% in patients with a mobile stoma and a positive hydrostatic test to only 14.2% in patients with a poorly mobile floor and a negative test (p &lt; 0.05). The positive predictive value of the hydrostatic test was 86.9%, negative predictive value 85.7%, sensitivity 95.2%, and specificity 66.6%.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The authors concluded that the hydrostatic test is an easy, brief test. A positive test result confirms a mobile ventricular floor and adequate flow through the created ventriculostomy. Mobility of the stoma is an important predictor of ETV success provided that there is no obstruction at the level of the arachnoid granulations or venous outflow. A thin, redundant, mobile third ventricle floor indicates a longstanding pressure differential between the third ventricle and the basal cisterns, which is a crucial factor for ETV success. A positive hydrostatic test may avert the need to insert a ventricular reservoir, thus avoiding associated risks of infection.</jats:p></jats:sec>

Cine Phase-Contrast MR Images Failed to Predict Clinical Outcome Following ETV

“…25 The hypothesis of decreased brain CSF absorption by granular villi and venous pressure was supported by a hydrostatic test, showing mobility of the stoma as an important predictor of ETV success provided that there is no obstruction at the level of the arachnoid granulations or venous outflow. 26 Further study is needed to investigate the hypothesis that the obliteration of cerebrospinal fluid pathways, the deteriorated CSF absorption, or increased venous pressure can be responsible for the failure of ETV-treated OHCP.…”

The constant flow ventricular infusion test: a simple and useful study in the diagnosis of third ventriculostomy failure

“…30 Several intraoperative factors have also been associated with an increased likelihood of ETV failure, including the presence of intraventricular or cisternal scarring, distorted intraventricular anatomy, absence of third ventricular floor pulsation, and negative results on a funnel test. 24,31 These factors, however, do not shed any light on patients with recurrent symptoms after initially successful ETV.…”

“…3,20,21,25,27,36,40,48 Intraoperative findings have not consistently correlated with ETV success. 31,34 The ETV may fail early or late, and delayed failures have at times been fatal. 8,15,16,28 Changes in ventricular volume postoperatively are not always a reliable indicator of a functioning ETV, particularly in patients with chronic hydrocephalus, and clinical improvement is the only clear guide to success or failure of ETV.…”