Journal of Neurosurgery
Andrew Tarnaris, Neil D. Kitchen and Laurence D. Watkins
Normal pressure hydrocephalus (NPH) represents a treatable form of dementia. Recent estimates of the incidence of this condition are in the region of 5% of patients with dementia. The symptoms of NPH can vary among individuals and may be confused with those of patients with multi-infarct dementia, dementia of the Alzheimer type, or even Parkinson disease. Traditionally the diagnosis of NPH could only be confirmed postoperatively by a favorable outcome to surgical diversion of CSF. The object of this literature review was to examine the role of structural and functional imaging in providing biomarkers of favorable surgical outcome.
A Medline search was undertaken for the years 1980–2006, using the following terms: normal pressure hydrocephalus, adult hydrocephalus, chronic hydrocephalus, imaging, neuroimaging, imaging studies, outcomes, surgical outcomes, prognosis, prognostic value, sensitivity, specificity, positive predictive value, negative predictive value, and accuracy.
The query revealed 16 studies that correlated imaging with surgical outcomes offering accuracy results. Three studies fulfilled the statistical criteria of a biomarker. A dementia Alzheimer-type pattern on SPECT in patients with idiopathic NPH, the presence of CSF flow void on MR imaging, and the N-acetylaspartate/choline ratio in patients with the secondary form are able to predict surgical outcomes with high accuracy.
There is at present Level A evidence for using MR spectroscopy in patients with secondary NPH, and Level B evidence for using SPECT and phase-contrast MR imaging to select patients with idiopathic NPH for shunt placement. The studies, however, need to be repeated by other groups. The current work should act as a platform to design further studies with larger sample sizes.
Claudia L. Craven, Roshini Ramkumar, Linda D’Antona, Simon D. Thompson, Lewis Thorne, Laurence D. Watkins and Ahmed K. Toma
Chronic ventriculomegaly in the absence of raised intracranial pressure (ICP) is a known entity in adult hydrocephalus practice. The natural history and indication for treatment is, however, poorly defined. A highly heterogeneous group, some adults with ventriculomegaly are asymptomatic, while others have life-threatening deteriorations. The authors hypothesized that the various presentations can be subtyped and represent different stages of decompensation. A cluster analysis was performed on a cohort of patients with chronic ventriculomegaly with the aim of elucidating typical clinical characteristics and outcomes in chronic ventriculomegaly in adults.
Data were collected from 79 patients with chronic ventriculomegaly referred to a single center, including demographics, presenting symptoms, and 24-hour ICP monitoring (ICPM). A statistical cluster analysis was performed to determine the presence of subgroups.
Four main subgroups and one highly dissimilar group were identified. Patients with ventriculomegaly commonly have a perinatal event followed by one of four main presentations: 1) incidental ventriculomegaly with or without headache; 2) highly symptomatic presentation (including reduced consciousness) and raised ICP; 3) early presenting with symptoms of headache and nausea (with abnormal pulsatility); and 4) late presenting with features common to normal pressure hydrocephalus. Each symptomatic group has characteristic radiological features, ICPM, and responses to treatment.
Cluster analysis has identified subgroups of adult patients with ventriculomegaly. Such groups may represent various degrees of decompensation. Surgical interventions may not be equally effective across the subgroups, presenting an avenue for further research. The identified subtypes provide further insight into the natural history of this lesser studied form of hydrocephalus.
Ahmed K. Toma, Muhammad Dherijha, Neil D. Kitchen and Laurence D. Watkins
The lumboperitoneal (LP) shunt with the adjustable PS Medical Strata NSC LP valve and small lumen peritoneal catheter was introduced in the authors' unit in 2007. The object of this study was to audit the unit's experience with this new shunt system.
The authors performed a retrospective review of the clinical records of patients who underwent Strata NSC LP shunt insertion. Demographic and clinical data as well as information about complications and revisions were reported.
Between August 2007 and November 2009, 20 patients underwent placement of an LP shunt with an adjustable Strata NSC valve and small lumen peritoneal catheter at the authors' institution. Their mean age was 40.3 years and the mean duration of follow-up was 12 months. Preoperatively, 18 patients had headache and 15 patients had visual signs and symptoms. Fourteen of the 18 patients with preoperative headache did not complain of headache postoperatively, and 4 had headache that was found not to be related to shunt function. Two of the patients with preoperative visual complaints had ongoing visual problems postoperatively. None of the patients had infection or subdural hematoma. The only overdrainage symptoms occurred in association with spontaneous readjustment of the valve and resolved when the valve was reset.
Thirteen patients (65%) did not require shunt revision. Seven patients (35%) required 13 shunt exploration or revision procedures, mainly due to distal obstruction. Placement of an LP shunt failed to completely resolve the raised intracranial pressure problem in 2 patients.
The use of the Strata NSC valve and small lumen peritoneal catheter is effective in treating pseudotumor cerebri and is beneficial in terms of markedly reducing overdrainage complications compared with other reported series of cases in which an LP shunt has been placed. However, the use of the Strata NSC valve and small lumen peritoneal catheter did not have a marked impact on other causes of shunt failure, particularly distal obstruction.
Ahmed K. Toma, Andrew Tarnaris, Neil D. Kitchen and Laurence D. Watkins
Managing symptomatic ventriculoperitoneal shunts with no clear evidence of shunt malfunction either clinically or radiologically can be a difficult task. The aim of this study was to assess intracranial pressure (ICP) monitoring as a method of investigating shunt function.
The authors performed a retrospective analysis of 38 continuous ICP monitoring procedures done in patients with ventriculoperitoneal shunts and suspected shunt malfunction.
Thirty-eight procedures were performed in 31 patients between January 2005 and October 2008. Sixteen recordings were normal, 6 revealed overdrainage or low pressure, 11 indicated underdrainage or high pressure, and 5 showed variable shunt function. Based on the findings after 20 procedures (53%), patients were treated conservatively: 4 by readjusting the valve setting and 16 by referral to the headache neurologist for medical treatment. Forty-five percent of the conservatively treated patients improved. Surgical exploration was undertaken following 18 procedures (47%); 72% of the surgically treated patients improved.
Continuous ICP monitoring using an intraparenchymal probe is a safe and effective method of investigating adult hydrocephalus.
Debayan Dasgupta, Linda D’Antona, Daniel Aimone Cat, Ahmed K. Toma, Carmel Curtis, Laurence D. Watkins and Lewis Thorne
Temporary CSF diversion through an external ventricular drain (EVD) comes with the risk of EVD-related infections (ERIs). The incidence of ERIs varies from 0.8% to 22%. ERIs increase mortality, morbidity, length of stay, and costs; require prolonged courses of antibiotics; and increase the need for subsequent permanent CSF diversion. The authors report the results of a quality improvement project designed to improve infection rates and EVD placement using simulation training in addition to a standardized perioperative care bundle. This project resulted not only in a decrease in ERIs, but also a significant improvement in surgical outcomes.
A best-practice standardized perioperative approach and care bundle was approved by consensus among the senior neurosurgeons at the authors’ institution, and a standardized operative note was designed to encourage adherence to policy and improve documentation. This approach was adapted from the bundle previously described by Kubilay et al. Simulation workshops were introduced to teach safe sampling technique, administration of intrathecal drugs, and a standardized operative technique using the Rowena head surgical model. Effects of the interventions on placement, infection rates, and displacement were measured at two distinct time points over a 2-year period.
Baseline audits demonstrated satisfactory EVD placement in 74%, an infection rate of 8.5%, and displacement occurring in 20%. In the 2 years following the interventions, satisfactory placement improved to 96%, infection rate fell to 4.8%, and inadvertent displacement occurred in only 1.7%.
Simulation training and standardizing the perioperative care of patients requiring EVDs dramatically improved placement accuracy, reduced infection rates, and reduced EVD displacement rate.
Andrew Tarnaris, Ahmed. K. Toma, Miles D. Chapman, Geoff Keir, Neil D. Kitchen and Laurence D. Watkins
The prognostic value of CSF biomarkers in patients with idiopathic normal pressure hydrocephalus (iNPH) has not been adequately studied to date. The aim of this study was to identify CSF markers of favorable surgical outcome in patients with iNPH undergoing the insertion of a ventriculoperitoneal shunt.
Ventricular CSF was collected intraoperatively from 22 patients with iNPH and enzyme-linked immunosorbent assay was used to analyze the levels of amyloid-β 1–42 (Aβ1–42) and total tau protein. The Black grading scale was used to assess outcomes at 6 months. Receiver operating characteristic (ROC) curves were obtained and discriminant function analysis was undertaken to provide sensitivity and specificity figures for each marker as well as their combination.
The mean age of the patients was 71.45 years (± 9.5 years [SD]). Follow-up was achieved in 21 patients. Seventeen patients had a favorable outcome and 4 patients had unfavorable outcome at 6 months. An Aβ1–42 level of 180 pg/ml had a sensitivity of 35% and a specificity of 20% for predicting a favorable outcome at 6 months. A total tau level of 767 pg/ml will have a sensitivity of 17% and a specificity of 20% for predicting a favorable outcome at 6 months. A combination of Aβ1–42 and total tau levels predicted favorable outcomes with a sensitivity of 80% and specificity of 82.4%.
In this pilot study a combination of Aβ1–42 levels and total tau protein levels predicted favorable surgical outcomes at 6 months with adequate accuracy to be of clinical use. Further study in a larger group with longer follow-up is warranted.
Ahmed K. Toma, Andrew Tarnaris, Joan P. Grieve, Laurence D. Watkins and Neil D. Kitchen
In this paper, the authors' goal was to compare the artifact induced by implanted (in vivo) adjustable shunt valves in spin echo, diffusion weighted (DW), and gradient echo MR imaging pulse sequences.
The MR images obtained in 8 patients with proGAV and 6 patients with Strata II adjustable shunt valves were assessed for artifact areas in different planes as well as the total volume for different pulse sequences.
Artifacts induced by the Strata II valve were significantly larger than those induced by proGAV valve in spin echo MR imaging pulse sequence (29,761 vs 2450 mm3 on T2-weighted fast spin echo, p = 0.003) and DW images (100,138 vs 38,955 mm3, p = 0.025). Artifacts were more marked on DW MR images than on spin echo pulse sequencse for both valve types.
Adjustable valve–induced artifacts can conceal brain pathology on MR images. This should influence the choice of valve implantation site and the type of valve used. The effect of artifacts on DW images should be highlighted pending the development of less MR imaging artifact–inducing adjustable shunt valves.