- Division of Neurosurgery, Department of Surgery, University of Toledo Medical Center, Toledo, Ohio, USA
- Department of Neurology, University of Toledo Medical Center, Toledo, Ohio, USA
Division of Neurosurgery, Department of Surgery, University of Toledo Medical Center, Toledo, Ohio, USA
DOI:10.4103/2152-7806.125860Copyright: © 2014 Chotai S. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Chotai S, Medel R, Herial NA, Medhkour A. External lumbar drain: A pragmatic test for prediction of shunt outcomes in idiopathic normal pressure hydrocephalus. Surg Neurol Int 27-Jan-2014;5:12
How to cite this URL: Chotai S, Medel R, Herial NA, Medhkour A. External lumbar drain: A pragmatic test for prediction of shunt outcomes in idiopathic normal pressure hydrocephalus. Surg Neurol Int 27-Jan-2014;5:12. Available from: http://sni.wpengine.com/surgicalint_articles/external-lumbar-drain-a-pragmatic-test-for-prediction-of-shunt-outcomes-in-idiopathic-normal-pressure-hydrocephalus/
Background:The consensus on most reliable supplemental test to predict the shunt responsiveness in patients with idiopathic normal pressure hydrocephalus (iNPH) is lacking. The aim of this study is to discuss the utility of external lumbar drain (ELD) in evaluation of shunt responsiveness for iNPH patients.
Methods:A retrospective review of 66 patients with iNPH was conducted. All patients underwent 4-day ELD trial. ELD-positive patients were offered ventriculoperitoneal shunt (VPS) surgery. The primary outcome evaluation parameters were gait and mini mental status examination (MMSE) assessment. The family and patient perception of improvement was accounted for in the outcome evaluation.
Results:There were 38 male and 28 female with mean age of 74 years (range 45-88 years). ELD trial was positive in 86% (57/66) of patients. No major complications were encountered with the ELD trial. A total of 60 patients (57 ELD-positive, 3 ELD-negative) underwent VPS insertion. The negative ELD trial (P = 0.006) was associated with poor outcomes following shunt insertion. The positive ELD trial predicted shunt responsiveness in 96% patients (P P = 0.02, CI = 0.52-1.0). The mean follow-up period was 12-months (range 0.3-3 years). The significant overall improvement after VPS was seen in 92% (55/60). The improvement was sustained in 76% of patients at mean 3-year follow-up. The number of comorbid conditions (P = 0.034, OR = 4.15, CI = 1.2-9.04), and a history of cerebrovascular accident (CVA) (P = 0.035, OR = 4.4, CI = 1.9-14.6) were the predictors of poor outcome following shunt surgery.
Conclusion:The positive ELD test predicted shunt responsiveness in 96% of patients. With adequate technique, maximal results with minimal complications can be anticipated. The number of comorbidities, history of CVA and negative ELD test were significantly associated with poor shunt outcomes.
Keywords: CSF tap test, external lumbar drain, idiopathic normal pressure hydrocephalus, supplemental test, valve pressure, ventriculoperitoneal shunt
Since the seminal description of classical symptom triad by Hakim and Adams; gait disturbance, urinary incontinence, and cognitive impairment, the definition of normal pressure hydrocephalus (NPH) has evolved.[
A retrospective review of medical records for 108 patients presenting with NPH to our institution between August 2000 and July 2011 was conducted. The institutional review board approved the study. The inclusion criteria for study were: (1) Presence of any one of the symptom triad; gait disturbance, urinary incontinence, and cognitive impairment (2) normal CSF pressure (60-240 mm H2O) (3) radiographic evidence of ventriculomegaly (Evan's index > 0.3); and (4) No antecedent disorder that can be causally related to the secondary NPH.
The ELD trial was the main supplemental test employed in all patients with clinical diagnosis of iNPH. Other supplemental tests, including radionuceliotide cisternography, and high volume lumbar CSF TT were employed in the patients presenting early in the series.
Following initial examination, a lumbar puncture was performed employing sterile technique and a lumbar catheter was inserted. After demonstration of adequate drainage, the catheter was connected to an external CSF collection system and secured in place at the mattress level of patients’ bed. The ELD bag utilized in the trial was equipped with a control valve that allowed the drainage of CSF at 10 ml/h; which could be readjusted as needed. Nursing staff was trained to adjust the valve as necessary in order to obtain an average drainage of 10 ml of CSF per hour. If the amount of 10 ml/h was not reached, the level of drainage system was lowered to obtain drainage of 10 ml/h. This was required in 11% of the patients (7/66). This technique provided better control over the drainage. For assessment of ELD response, baseline videographic gait assessment, balance, muscle strength, fluency of speech, general behavior, and mini mental status examination (MMSE) were compiled on the day of admission. The gait assessment was performed by a physical therapist (PT) or occupational therapist (OT), a neurosurgeon, and a nurse practitioner. The assessment was based on balance and number of steps required to traverse a specified distance, valuated by timed 10-15 meter trial. The inputs on the balance, stance, and stride length were video recorded and noted on the patient's chart. No sophisticated grading of these parameters was employed. The assessment of patients, as on the day of admission, was repeated subsequently for 3 days and the final assessment was conducted on Day 4 following removal of the lumbar drain. The findings were recorded in the patient's chart. Patients were then discharged with instruction to follow up in the neurosurgery clinic 1-2 weeks later. The patient was considered positive on ELD trial if there was an increase of two or more points on the MMSE from the baseline to final exam or improvement in gait, changes in manner of sitting and standing up, balance and fluency of speech, which was assessed based on the videotape assessment and PT/OT documentation. The outcomes were evaluated after the 4-day ELD trial and the patients with positive ELD trial were then offered surgical treatment [
(a) Subdural hygroma on right measuring 1.8 cm in greatest thickness and on the left measuring 9 mm in greatest thickness. Regression of these hygromas was achieved by readjustment of the opening pressure of valve to a higher level (b) Enlarged ventricles with right lateral ventricle slightly larger than left, ventriculoperitoneal shunt in place in the medial aspect of the left lateral ventricle
VPS insertion was carried out by posterior parietal approach. The programmable valve with antisiphon technology (Medtronic Strata, MN, USA) was installed in 31/60 patients shunted between March 2005 and February 2009. The valve was programmed to initial settings of 1.5, which corresponds to the opening pressure of 85-105 mm H2O. Codman valve (Codman, Johnson and Johnson, MA, USA), set to an initial value of 120 mm H2O, was installed in 13 patients before March 2005 and the new Codman programmable valve with initial pressure set to 200 mm H2O was installed in 16 patients after February 2009. Patients were discharged following shunt insertion and the follow-up was adjusted according to the symptomatology and need to modify the valve settings.
Follow-up and outcome assessment after VPS
The outcomes after VPS insertion were evaluated at each follow-up visit based on the clinical and functional assessment. The primary clinical criteria were gait improvement and cognitive evaluation. The functional outcome was assessed based on the patient and family perception of improvement in daily activity. Patients and families were interviewed regarding the degree of independence in terms of daily activities, improvement in overall general behavior, improvement in cognition, urinary control, changes in the dependence on assisted devices or person for movement, changes in balance and increase in the stride length. Follow up was conducted initially at 1 month after valve pressure modification. Later on, changes in valve pressure were made every 2-3 months until the maximal response is reached and was sustained during subsequent visits. Prior to each office visit the patients received head CT scan to look for changes in the ventricular size, transependymal CSF resorption and rule out any subdural collections [
All descriptive statistics calculated for categorical variable are reported as percentages and continuous variable as medians. Fisher exact test was used for testing association between two categorical variables. Mann-Whitney test was used for examining differences in continuous measures with deviation from the normality, and for the ordinal measures (MMSE scores) between the independent groups. Repeated measure analysis using Friedman's test was performed to test for change in the MMSE scores and steps/meter recorded during the ELD trial and for the final outcome evaluation. Logistic regression analysis was performed to examine the association of the outcome (improvement with VPS insertion) with the predictors, adjusting for age and gender of patients. Hosmer-Lemeshow statistic was used to assess the fit of the models. A receiver operating characteristic (ROC) curve was used to evaluate the prognostic performance of ELD trial as supplemental test for shunt responsiveness. All hypotheses were tested at 0.05 level of significance and the analysis was performed using the SPSS version 20 (IBM, Chicago, Inc).
Sixty-six patients met inclusion criteria for the study. There were 38 male and 28 female patients, with mean age of 74 years (range 45-88 years).
A total of 66 patients underwent ELD trial; 86% (57/66) of the patients were ELD positive. The mean age at presentation (P = 0.04), presence or absence of any comorbidity (P = 0.028), and positive history of hypertension (P = 0.016) was significantly different between ELD positive and negative patients [
No major complications were encountered with the ELD trial, however, 6/66 (10%) patients developed transient nerve root irritation. Catheter withdrawal of 5-10 mm followed by pain medication resolved the symptoms in all patients, and improvement in gait was noted on the third day of trial. One patient became agitated and confused subsequently removing the drain prematurely; however, the trial was completed successfully 2 months later. Another patient became disoriented after administration of the antihistamine confounding the precise trial findings; however, after careful evaluation the patient demonstrated definite improvement and was ultimately shunted.
Other supplemental tests
The patients managed during earlier years in the series (22/66) underwent radionuclide cisternogram as the supplemental test. Findings indicated type II activity (no ventricular activity with delayed migration) in 2 (9%); type IIIa (transient ventricular activity with clearance by usual migration) in 10 (45%); type IIIb (transient ventricular activity without normal clearance) in 3 (14%); and type IV activity (persistent ventricular activity without adequate clearance) in 7 (32%) patients. Those patients in categories III-IV were considered to have findings consistent with NPH. None of these patterns were significantly associated with outcome following VPS insertion.
High-volume CSF TT was employed earlier in the series and a total of 64% (42/66) patients underwent high volume TT. Symptomatic improvement was found in 97% (39/42) of patients. Gait was the most common domain to demonstrate improvement. The positive TT was not significantly associated with shunt outcomes; however, all the patients with poor outcomes had positive TT [
VPS insertion was carried out in all 57 ELD trial positive and 3 ELD negative patients. With older valve, the overdrainage complications were encountered with setting at 1.5 (valve allowed setting from 0.5 to 2.5) and 120 mm H2O (the first generation Codman valve). To prevent complications including subdural hygroma and hematoma, and to have a unified start the initial opening pressure was set to 200 mm H2O with the newer valve. This allowed for adjustment to lower or higher valve settings based on the CT scan findings, videographic gait assessment, MMSE, general behavior of the patient, urinary control, and the patient and family perception of improvement. At the follow-up visit if the evaluation by clinical team, patient and family revealed a decline in functional status, the valve pressure was adjusted such that the maximum alleviation of symptoms could be obtained, at the same time minimizing the incidence of subdural fluid collections and other low pressure side effects. For instance, if a patient demonstrated decline in gait and/or cognition at valve setting of 200 mm H2O, the opening pressure of the valve was modified to 180 mm H2O and, in subsequent follow-up visits, the valve pressure was further lowered as needed. Although, with this methodology, more outpatient visits are anticipated, we found this as the safest measure that reduced the incidence of subdural hygromas to negligible. This was particularly seen in those patients who underwent VPS between 2009 and 2011, with the newer programmable Codman valves.
The over-drainage complication including subdural hygroma was present in 17% (10/60), which was treated by valve pressure adjustment. One patient (1.7%) patient had a subdural hematoma that required surgical intervention. Fifteen percent (9/60) patients with shunt obstruction (3) and subdural fluid collection (6) underwent revision surgery to change the shunt configuration. The patients who underwent VPS between 2009 and 2011 with new programmable Codman valve had lower incidence of subdural fluid collections (5%, 3/60). No cases of subdural hygroma requiring surgical intervention were encountered in the later group. No other major complications such as intraventricular or intraparenchymal hemorrhage or meningitis were encountered. The outcomes did not significantly differ between patients with or without over-drainage symptoms following shunt insertion.
Follow-up and outcome
The primary outcomes were assessed over a mean follow up of 12 months (0.3-3 years). The overall improvement in outcome after VPS insertion was evident in 55/60 (92%) patients and these were identified as shunt responders. The rate of improvement in patients with ELD trial positive and undergoing shunt surgery was 96% (55/57) [
Long-term follow-up (>3 years) was available in 29/60 (48%) patients. The improvement was sustained in 76% (22/29) of the patients. Fifty-nine percent (17/29) of the patients improved substantially compared with their last follow-up; 21% (6/29) patients had improvement in both gait and MMSE (two points or more) and 38% (11/29) had gait improvement but no change in MMSE. In one patient, the overall improvement after VPS was maintained for 9 years. Forty-one percent (12/29) demonstrated no further improvement in symptoms at mean 3 year follow-up compared with the last post-VPS follow-up. Five patients (5/29;17%) demonstrated no change in gait and MMSE while 7/29 (24%) patients showed no change in gait but there was two points or more decline in MMSE compared with the last follow up. However, it was still higher than the preshunt MMSE.
Various supplemental tests have been employed to increase the predictive accuracy for shunt responsiveness to greater than 90%.[
Another test used routinely for diagnosing iNPH is high volume CSF TT or Miller–Fisher test. The high volume TT is often adopted with the caveat that candidates for shunt surgery should not be excluded solely based on negative TT, because of its low sensitivity (26-61%).[
One of the major setbacks of ELD is the high rate of complications reported in the literature. An overall rate of complication reported in the early literature was as high as 40%. The recent study reports the rate of major complications (meningitis, retained catheter, intracranial subdural collections, and traumatic pattern subarachnoid hemorrhage) ranging from 0% to 5% and that of minor complications (local infection, headaches substantial enough to warrant drain removal, and nerve root irritation) ranging from 5.2% to 13%.[
Outcomes after VPS
The iNPH guidelines have reported favorable outcome rates ranging from 30% to 96% after VPS surgery.[
Finally, the ideal cost-effective supplementary test to predict the shunt responsiveness in patients with iNPH is still evolving. The present study provides preliminary results and demonstrates that ELD trial is the optimal supplemental test with high sensitivity, NPV, and PPV. However, the results of this study should be interpreted with caution due to retrospective study design with a relatively smaller number of patients. Further randomized prospective study with large sample size, where the patients undergoes a VPS regardless of ELD results are necessary to confirm the findings of this study and fully address the accuracy of ELD as the sole supplemental test for shunt responsiveness.
The overall outcome following VPS mainly depends on the selection of patients for CSF diversion surgery. The positive ELD trial predicted shunt responsiveness in 96% patients. The overall rate of improvement in patients undergoing VPS insertion was 92%. The number of comorbidities, history of CVA and negative ELD were significantly associated with poor outcome. The overall improvements were sustained in 76% of patients at mean 3 years follow-up. The ELD trial demonstrated reasonable prognostic accuracy for prediction of shunt-responsiveness in iNPH patients. In addition, low to negligible complications encountered in patients undergoing ELD trial is encouraging. However, further prospective randomized clinical trials are required to assess with certainty the predictive value of ELD.
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