Placebo-Controlled Effectiveness of Idiopathic Normal Pressure Hydrocephalus Shunting

Neurosurgery 92:481–489, 2023

Multiple prospective nonrandomized studies have shown 60% to 70% of patients with idiopathic normal pressure hydrocephalus (iNPH) improve with shunt surgery, but multicenter placebo-controlled trial data are necessary to determine its effectiveness.

OBJECTIVE: To evaluate the effectiveness of cerebrospinal fluid shunting in iNPH through comparison of open vs placebo shunting groups at 4 months using a pilot study.

METHODS: Patients were randomized to a Codman Certas Plus valve (Integra LifeSciences) set at 4 (open shunt group) or 8 (“virtual off”; placebo group). Patients and assessors were blinded to treatment group. The primary outcome measure was 10-m gait velocity. Secondary outcome measures included functional scales for bladder control, activities of daily living, depression, and quality of life. Immediately after 4-month evaluation, all shunts were adjusted in a blinded fashion to an active setting and followed to 12months after shunting.

RESULTS: A total of 18 patients were randomized. At the 4-month evaluation, gait velocity increased by 0.28 ± 0.28m/s in the open shunt group vs 0.04 ± 0.17m/s in the placebo group. The estimated treatment difference was 0.22 m/s ([P = .071], 95% CI 0.02 to 0.46). Overactive Bladder Short Form symptom bother questionnaire significantly improved in open shunt vs placebo (P = .007). The 4-month treatment delay did not reduce the subsequent response to active shunting, nor did it increase the adverse advents rate at 12 months.

CONCLUSION: This multicenter, randomized pilot study demonstrates the effectiveness, safety, and feasibility of a placebo-controlled trial in iNPH, and found a trend suggesting gait velocity improves more in the open shunt group than in the placebo group.

First Experience With Postoperative Transcranial Ultrasound Through Sonolucent Burr Hole Covers in Adult Hydrocephalus Patients

Neurosurgery 92:382–390, 2023

Managing patients with hydrocephalus and cerebrospinal fluid (CSF) disorders requires repeated head imaging. In adults, it is typically computed tomography (CT) or less commonly magnetic resonance imaging (MRI). However, CT poses cumulative radiation risks and MRI is costly. Ultrasound is a radiation-free, relatively inexpensive, and optionally point-of-care alternative, but is prohibited by very limited windows through an intact skull.

OBJECTIVE: To describe our initial experience with transcutaneous transcranial ultrasound through sonolucent burr hole covers in postoperative hydrocephalus and CSF disorder patients.

METHODS: Using cohort study design, infection and revision rates were compared between patients who underwent sonolucent burr hole cover placement during new ventriculoperitoneal shunt placement and endoscopic third ventriculostomy over the 1-year study time period and controls from the period 1 year before. Postoperatively, trans-burr hole ultrasound was performed in the clinic, at bedside inpatient, and in the radiology suite to assess ventricular anatomy.

RESULTS: Thirty-seven patients with sonolucent burr hole cover were compared with 57 historical control patients. There was no statistically significant difference in infection rates between the sonolucent burr hole cover group (1/37, 2.7%) and the control group (0/57, P = .394). Revision rates were 13.5% vs 15.8% (P = 1.000), but no revisions were related to the burr hole or cranial hardware.

CONCLUSION: Trans-burr hole ultrasound is feasible for gross evaluation of ventricular caliber postoperatively in patients with sonolucent burr hole covers. There was no increase in infection rate or revision rate. This imaging technique may serve as an alternative to CT and MRI in the management of select patients with hydrocephalus and CSF disorders.

Extra-axial endoscopic third ventriculostomy: preliminary experience with a technique to circumvent conventional endoscopic third ventriculostomy complications

J Neurosurg 138:503–513, 2023

Endoscopic third ventriculostomy (ETV) is mostly safe but may have serious complications. Most of the complications are inherent to the procedure’s intra-axial nature. This study aimed to explore an alternative route to overcome inherent issues with conventional ETV. The authors performed supraorbital, subfrontal extra-axial ETV (EAETV) via the lamina terminalis.

METHODS This prospective study began in October 2021 and included patients with obstructive triventricular hydrocephalus with a Glasgow Coma Scale score of 8 or more and a minimum follow-up of 3 months. Patients with multiloculated hydrocephalus and those younger than 1 year of age were excluded. The preoperative parameters etiology, symptoms, Evans’ Index, frontal occipital horn ratio (FOHR), and third ventricle index were recorded. The surgical procedure is described. Postoperative evaluation included clinical (modified Rankin Scale [mRS]) and radiological assessment with CT and cine phase-contrast MRI. Preoperative and postoperative parameters were compared statistically.

RESULTS Ten patients were included in this study. Six patients had acute hydrocephalus, and 4 had chronic hydrocephalus. After EAETV, all patients showed clinical improvement. An mRS score of 0 or 1 was achieved in 9 patients, but the mRS score remained at 4 in a patient with tectal tuberculoma. There was a significant reduction in Evans’ Index, FOHR, and third ventricle index after EAETV (p < 0.05). The mean percent reduction in Evans’ Index was 20.80% ± 13.89%, the mean percent reduction in FOHR was 20.79% ± 12.98%, and the mean percent reduction in the third ventricle index was 37.45% ± 14.74%. CSF flow voids were seen in all cases. The results of CSF flow quantification parameters were as follows: mean peak velocity 3.82 ± 0.93 cm/sec, mean average velocity 0.10 ± 0.05 cm/sec, mean average flow rate 46.60 ± 28.58 μL/sec, mean forward volume 39.90 ± 23.29 μL, mean reverse volume 34.10 ± 15.98 μL, mean overall flow amplitude 74.00 ± 27.61 μL, and mean stroke volume 37.00 ± 13.80 μL. One patient developed a minor frontal lobe contusion. The frontal air sinus was breached in 5 patients, but none had CSF rhinorrhea. Transient supraorbital hypesthesia was seen in 3 patients. No patient had electrolyte disturbance or change in thirst or fluid intake habits.

CONCLUSIONS EAETV is a feasible, safe, and effective surgical alternative to conventional ETV.

Vascular risk profiles for predicting outcome and long-term mortality in patients with idiopathic normal pressure hydrocephalus: comparison of clinical decision support tools

J Neurosurg 138:476–482, 2023

Vascular risk factors (VRFs) may act synergistically, and clinical decision support tools (CDSTs) have been developed that present vascular risk as a summarized score. Because VRFs are a major issue in patients with idiopathic normal pressure hydrocephalus (INPH), a CDST may be useful in the diagnostic workup. The objective was to compare 4 CDSTs to determine which one most accurately predicts short-term outcome and 10-year mortality after CSF shunt surgery in INPH patients.

METHODS One-hundred forty INPH patients who underwent CSF shunt surgery were included. For each patient, 4 CDST scores (Systematic Coronary Risk Evaluation–Older Persons [SCORE-OP], Framingham Risk Score [FRS], Revised Framingham Stroke Risk Profile, and Kiefer’s Comorbidity Index [KCI]) were estimated. Short-term outcome (3 months after CSF shunt surgery) was defined on the basis of improvements in gait, Mini-Mental State Examination score, and modified Rankin Scale score. The 10-year mortality rate after surgery was noted. The CDSTs were compared by using Cox regression analysis, receiver operating characteristic curve analysis, and the chi-square test.

RESULTS For 3 CDSTs, increased score was associated with increased risk of 10-year mortality. A 1-point increase in the FRS indicated a 2% higher risk of death within 10 years (HR 1.02, 95% CI 1.003–1.035, p = 0.021); SCORE-OP, 5% (HR 1.05, 95% CI 1.019–1.087, p = 0.002); and KCI, 12% (HR 1.12, 95% CI 1.03–1.219, p = 0.008). FRS predicted short-term outcome of surgery (p = 0.024). When the cutoff value was set to 32.5%, the positive predictive value was 80% and the negative predictive value was 48% (p = 0.012).

CONCLUSIONS The authors recommend using FRS to predict short-term outcome and 10-year risk of mortality in INPH patients. The study indicated that extensive treatment of the risk factors of INPH may decrease risk of mortality.

Failure of Internal Cerebrospinal Fluid Shunt: A Systematic Review and Meta-Analysis of the Overall Prevalence in Adults

World Neurosurg. (2023) 169:20-30

Reported rates of failures of internal cerebrospinal fluid shunt (ICSFS) vary greatly from less than 5% to more than 50% and no meta-analysis to assess the overall prevalence has been performed. We estimated the failure rate after ICSFS insertion and searched for associated factors.

METHODS: Six databases were searched from January 1990 to February 2022. Only original articles reporting the rate of adult shunt failure were included. Random-effects meta-analysis with a generalized linear mixed model method and logit transformation was used to compute the overall failure prevalence. Subgroup analysis and meta-regression were implemented to search for associated factors.

RESULTS: Of 1763 identified articles, 46 were selected, comprising 70,859 ICSFS implantations and 13,603 shunt failures, suggesting an accumulated incidence of 19.2%. However, the calculated pooled prevalence value and its 95% confidence interval (CI) were 22.7% (95% CI, 19.8e5.8). The CI of the different estimates did not overlap, indicating a strong heterogeneity confirmed by a high I 2 of 97.5% (95% CI, 97.1e97.8; P < 0.001; s 2 [ 0.3). Ninety-five percent prediction interval of shunt failure prevalence ranged from 8.75% to 47.36%. A meta-regression of prevalence of publication found a barely significant decreasing failure rate of about 2% per year (e2.11; 95% CI, e4.02 to e0.2; P [ 0.031).

CONCLUSIONS: Despite being a simple neurosurgical procedure, ICSFS insertion has one of the highest risk of complications, with failure prevalence involving more than 1 patient of 5. Nonetheless, all efforts to lower this high level of shunt failure seem to be effective.

Surgical management of colloid cysts of the third ventricle: a single-institution comparison of endoscopic and microsurgical resection

J Neurosurg 137:905–913, 2022

Colloid cysts of the third ventricle are histologically benign lesions that can cause obstructive hydrocephalus and death. Historically, colloid cysts have been removed by open microsurgical approaches. More recently, minimally invasive endoscopic and port-based techniques have offered decreased complications and length of stay, with improved patient satisfaction.

METHODS A single-center retrospective analysis of patients with colloid cysts who underwent surgery at a large tertiary care hospital was performed. The cohort was assessed based on the surgical approach, comparing endoscopic resection to open microsurgical resection. The primary endpoint was rate of perioperative complications. Univariate analysis was used to assess several procedure-related variables and the cost of treatment. Multivariate analysis was used to assess predictors of perioperative complications. Total inpatient cost for each case was extracted from the health system financial database.

RESULTS The study included 78 patients with colloid cysts who underwent resection either via an endoscopic approach (n = 33) or through a craniotomy (n = 45) with an interhemispheric-transcallosal or transcortical-transventricular approach. Nearly all patients were symptomatic, and half had obstructive hydrocephalus. Endoscopic resection was associated with reduced operative time (3.2 vs 4.9 hours, p < 0.001); lower complication rate (6.1% vs 33.1%, p = 0.009); reduced length of stay (4.1 vs 8.9 days, p < 0.001); and improved discharge to home (100% vs 75.6%, p = 0.008) compared to microsurgical resection. Coagulated residual cyst wall remnants were more common after endoscopic resection (63.6% vs 19.0%, p < 0.001) although this was not associated with a significantly increased rate of reoperation for recurrence. The mean follow-up was longer in the microsurgical resection group (3.1 vs 4.9 years, p = 0.016). The total inpatient cost of endoscopic resection was, on average, one-half (47%) that of microsurgical resection. When complications were encountered, the total inpatient cost of microsurgical resection was 4 times greater than that of endoscopic resection where no major complications were observed. The increased cost-effectiveness of endoscopic resection remained during reoperation.

CONCLUSIONS Endoscopic resection of colloid cysts of the third ventricle offers a significant reduction in perioperative complications when compared to microsurgical resection. Endoscopic resection optimizes nearly all procedure-related variables compared to microsurgical resection, and reduces total inpatient cost by > 50%. However, endoscopic resection is associated with a significantly increased likelihood of residual coagulated cyst wall remnants that could increase the rate of reoperation for recurrence. Taken together, endoscopic resection represents a safe and effective minimally invasive approach for removal of colloid cysts.

Transseptal interforniceal endoscopic removal of superiorly recessed colloid cysts

J Neurosurg 137:813–819, 2022

Transforaminal endoscopic colloid cyst resection is well described. However, some anatomical colloid cyst variants may warrant a modified approach. Rarely, colloid cysts separate the forniceal columns and grow superiorly within the leaflets of the septum pellucidum. Thus, the authors’ goal was to characterize the imaging features, clinical presentation, surgical strategy, and outcomes of patients with this superiorly recessed colloid cyst variant.

METHODS A retrospective evaluation of patients who underwent endoscopic resection of colloid cysts from 1999 to 2020 was performed. The patients were dichotomized depending on whether the cyst was located predominately below the forniceal columns or was superiorly recessed (forniceal column separation with variable intraseptal extension). This comparative cohort study focused on clinical presentation, imaging features, operative technique, and patient outcome.

RESULTS In total, 182 patients were identified. Seventeen patients had colloid cysts that were defined as superiorly recessed and underwent transseptal interforniceal removal, and 165 patients underwent a standard transforaminal approach. Patients had similar demographic characteristics. However, transseptal cysts were on average larger (17.8 mm vs 11.4 mm, p < 0.0001), and these patients had a greater frontal-occipital horn ratio (0.45 vs 0.41, p = 0.012). They were also more likely to have undergone a previous resection (p = 0.02). The two cohorts had similar surgical outcomes, with no differences in extent of resection, recurrence, or complications.

CONCLUSIONS Superiorly recessed intraseptal colloid cysts are larger and tend to splay the bodies of the fornix, thus requiring a parasagittal transseptal interforniceal endoscopic approach. This achieves complete removal with comparatively negligible morbidity or rare recurrence (5.9%).

Review of Cerebrospinal Fluid Physiology and Dynamics: A Call for Medical Education Reform

Neurosurgery 91:1–7, 2022

The flow of cerebrospinal fluid (CSF) has been described as a unidirectional system with the choroid plexus serving as the primary secretor of CSF and the arachnoid granulations as primary reabsorption site. This theory of neurosurgical forefathers has been universally adopted and taught as dogma. Many neuroscientists have found difficulty reconciling this theory with common pathologies, and recent studies have found that this “classic” hypothesis may not represent the full picture.

OBJECTIVE: To review modern CSF dynamic theories and to call formedical education reform.

METHODS: We reviewed the literature from January 1990 to December 2020. We searched the PubMed database using key terms “cerebrospinal fluid circulation,” “cerebrospinal fluid dynamics,” “cerebrospinal fluid physiology,” “glymphatic system,” and “glymphatic pathway.” We selected articles with a primary aim to discuss either CSF dynamics and/or the glymphatic system.

RESULTS: The Bulat–Klarica–Oreˇskovi´c hypothesis purports that CSF is secreted and reabsorbed throughout the craniospinal axis. CSF demonstrates similar physiology to that of water elsewhere in the body. CSF “circulates” throughout the subarachnoid space in a pulsatile to-and-fro fashion. Osmolarity plays a critical role in CSF dynamics. Aquaporin-4 and the glymphatic system contribute to CSF volume and flow by establishing osmolarity gradients and facilitating CSF movement. Multiple studies demonstrate that the choroid plexus does not play any significant role in CSF circulation.

CONCLUSION: We have highlighted major studies to illustrate modern principles of CSF dynamics. Despite these, the medical education system has been slow to reform curricula and update learning resources.

Motor skills, cognitive impairment, and quality of life in normal pressure hydrocephalus: early effects of shunt placement

Traditionally, clinical findings of normal pressure hydrocephalus are mainly characterized by the Hakim triad. The aim of this study is to evaluate the performance of patients suffering from idiopathic normal pressure hydrocephalus (iNPH) in a more holistic manner regarding motor skills, cognitive impairment, and quality of life.

Methods In total, 30 individuals diagnosed with iNPH as well as a reference group with another 30 individuals were included. The iNPH patients and the reference group were age, educational, and morbidity matched. A standardized test battery for psychomotor skills, gait, neuropsychological abilities as well as questionnaires for quality of life was applied. The iNPH group was tested prior to surgery, at 6 weeks, and 3 months postoperatively. The reference group was tested once.

Results Patients showed a significant improved performance in various items of the test battery during the first 3 months postoperatively. This included neuropsychological evaluation, motor skills including gait and upper motor function as well as the quality of life of the patients. Compared to reference individuals, neuropsychological aspects and quality of life of iNPH patients improved in some parts nearly to normal values.

Conclusion Our findings underline that shunt surgery does not only improve the symptoms in iNPH patients but also ameliorates the quality of life to a great extent close to those of age and comorbidity matched reference individuals. This data enables an optimized counseling of iNPH patients regarding the expectable outcome after shunt surgery especially regarding cognitive performance, motor skills as well as life quality.

Cerebrospinal fluid shunting protocol for idiopathic intracranial hypertension for an improved revision rate

J Neurosurg 136:1790–1795, 2022

Cerebrospinal fluid (CSF) shunting in idiopathic intracranial hypertension (IIH) is associated with high complication rates, primarily because of the technical challenges that are related to small ventricles and a large body habitus. In this study, the authors report the benefits of a standardized protocol for CSF shunting in patients with IIH as relates to shunt revisions.

METHODS This was a retrospective study of consecutive patients with IIH who had undergone primary insertion of a CSF shunt between January 2014 and December 2020 at the authors’ hospital. In July 2019, they implemented a surgical protocol for shunting in IIH. This protocol recommended IIH shunt insertion by neurosurgeons with expertise in CSF disorders, a frontal ventriculoperitoneal (VP) shunt with an adjustable gravitational valve and integrated intracranial pressure monitoring device, frameless stereotactic insertion of the ventricular catheter, and laparoscopic insertion of the peritoneal catheter. Thirty-day revision rates before and after implementation of the protocol were compared in order to assess the impact of standardizing shunting for IIH on shunt complications.

RESULTS The 81 patients included in the study were predominantly female (93%), with a mean age of 31 years at primary surgery and mean body mass index (BMI) of 37 kg/m2. Forty-five patients underwent primary surgery prior to implementation of the protocol and 36 patients after. Overall, 12 (15%) of 81 patients needed CSF shunt revision in the first 30 days, 10 before and 2 after introduction of the protocol. This represented a significant reduction in the early revision rate from 22% to 6% after the protocol (p = 0.036). The most common cause of shunt revision for the whole cohort was migration or misplacement of the peritoneal catheter, occurring in 6 of the 12 patients. Patients with a higher BMI were significantly more likely to have a shunt revision within 30 days (p = 0.022).

CONCLUSIONS The Birmingham standardized IIH shunt protocol resulted in a significant reduction in revisions within 30 days of primary shunt surgery in patients with IIH. The authors recommend standardization for shunting in IIH as a method for improving surgical outcomes. They support the notion of subspecialization for IIH shunts, the use of a frontal VP shunt with sophisticated technology, and laparoscopic insertion of the peritoneal end. https:

Reducing the risks of proximal and distal shunt failure in adult hydrocephalus

J Neurosurg 136:877–886, 2022

Patient outcomes of ventriculoperitoneal (VP) shunt surgery, the mainstay treatment for hydrocephalus in adults, are poor because of high shunt failure rates. The use of neuronavigation or laparoscopy can reduce the risks of proximal or distal shunt catheter failure, respectively, but has less independent effect on overall shunt failures. No adult studies to date have combined both approaches in the setting of a shunt infection prevention protocol to reduce shunt failure. The goal of this study was to determine whether combining neuronavigation and laparoscopy with a shunt infection prevention strategy would reduce the incidence of shunt failures in adult hydrocephalic patients.

METHODS Adult patients (age ≥ 18 years) undergoing VP shunt surgery at a tertiary care institution prior to (pre–Shunt Outcomes [ShOut]) and after (post-ShOut) the start of a prospective continuous quality improvement (QI) study were compared. Pre-ShOut patients had their proximal and distal catheters placed under conventional freehand approaches. Post-ShOut patients had their shunts inserted with neuronavigational and laparoscopy assistance in placing the distal catheter in the perihepatic space (falciform technique). A shunt infection reduction protocol had been instituted 1.5 years prior to the start of the QI initiative. The primary outcome of interest was the incidence of shunt failure (including infection) confirmed by standardized criteria indicating shunt revision surgery.

RESULTS There were 244 (115 pre-ShOut and 129 post-ShOut) patients observed over 7 years. With a background of shunt infection prophylaxis, combined neuronavigation and laparoscopy was associated with a reduction in overall shunt failure rates from 37% to 14%, 45% to 22%, and 51% to 29% at 1, 2, and 3 years, respectively (HR 0.44, p < 0.001). Shunt infection rates decreased from 8% in the pre-ShOut group to 0% in the post-ShOut group. There were no proximal catheter failures in the post-ShOut group. The 2-year rates of distal catheter failure were 42% versus 20% in the pre- and post-ShOut groups, respectively (p < 0.001).

CONCLUSIONS Introducing a shunt infection prevention protocol, placing the proximal catheter under neuronavigation, and placing the peritoneal catheter in the perihepatic space by using the falciform technique led to decreased rates of infection, distal shunt failure, and overall shunt failure.

Surgical treatment of symptomatic pineal cysts without hydrocephalus—meta‑analysis of the published literature

Acta Neurochirurgica (2022) 164:61–77

To examine published data and assess evidence relating to safety and efficacy of surgical management of symptomatic pineal cysts without hydrocephalus (nhSPC), we performed a systematic review of the literature and meta-analysis.

Methods Following the PRISMA guidelines, we searched Pubmed and SCOPUS for all reports with the query ‘Pineal Cyst’ AND ‘Surgery’ as of March 2021, without constraints on study design, publication year or status (PROSPERO_ CRD:42,021,242,517). Assessment of 1537 hits identified 26 reports that met inclusion and exclusion criteria.

Results All 26 input studies were either case reports or single-centre retrospective cohorts. The majority of outcome data were derived from routine physician-recorded notes. A total of 294 patients with surgically managed nhSPC were identified. Demographics: Mean age was 29 (range: 4–63) with 77% females. Mean cyst size was 15 mm (5–35). Supracerebellar infratentorial approach was adopted in 90% of cases, occipital-transtentorial in 9%, and was not reported in 1%. Most patients were managed by cyst resection (96%), and the remainder by fenestration. Mean post-operative follow-up was 35 months (0–228). Presentation: Headache was the commonest symptom (87%), followed by visual (54%), nausea/vomit (34%) and vertigo/dizziness (31%). Other symptoms included focal neurology (25%), sleep disturbance (17%), cognitive impairment (16%), loss of consciousness (11%), gait disturbance (11%), fatigue (10%), ‘psychiatric’ (2%) and seizures (1%). Mean number of symptoms reported at presentation was 3 (0–9). Outcomes: Improvement rate was 93% (to minimise reporting bias only consecutive cases from cohort studies were considered, N = 280) and was independent of presentation. Predictors of better outcomes were large cyst size (OR = 5.76; 95% CI: 1.74–19.02) and resection over fenestration (OR = 12.64; 3.07–52.01). Age predicted worse outcomes (OR = 0.95; 0.91–0.99). Overall complication rate was 17% and this was independent of any patient characteristics. Complications with long-term consequences occurred in 10 cases (3.6%): visual disturbance (3), chronic incisional pain (2), sensory disturbance (1), fatigue (1), cervicalgia (1), cerebellar stroke (1) and mortality due to myocardial infarction (1).

Conclusions Although the results support the role of surgery in the management of nhSPCs, they have to be interpreted with a great deal of caution as the current evidence is limited, consisting only of case reports and retrospective surgical series. Inherent to such studies are inhomogeneity and incompleteness of data, selection bias and bias related to assessment of outcome carried out by the treating surgeon in the majority of cases. Prospective studies with patient-reported and objective outcome assessment are needed to provide higher level of evidence.


Ventriculoperitoneal Shunt Drainage Increases With Gravity and Cerebrospinal Fluid Pressure Pulsations: Benchtop Model

Neurosurgery 89:1141–1147, 2021

There have been few improvements in cerebrospinal fluid (CSF) shunt technology since John Holter introduced the silicon valve, with overdrainage remaining a major source of complications.

OBJECTIVE: To better understand why valves are afflicted by supra-normal CSF flow rates. We present in Vitro benchtop analyses of flow through a differential pressure valve under simulated physiological conditions.

METHODS: The pseudo-ventricle benchtop valve testing platform that comprises a rigid pseudo-ventricle, compliance chamber, pulsation generator, and pressure sensors was used to measure flow rates through a differential pressure shunt valve under the following simulated physiological conditions: orientation (horizontal/vertical), compliance (low/medium/high), and pulsation generator force (low/medium/high).

RESULTS: Our data show that pulse pressures are faithfully transmitted from the ventricle to the valve, that lower compliance and higher pulse generator forces lead to higher pulse pressures in the pseudo-ventricle, and that both gravity and higher pulse pressure lead to higher flow rates. The presence of a valve mitigates but does not eliminate these higher flow rates.

CONCLUSION: Shunt valves are prone to gravity-dependent overdrainage, which has motivated the development of gravitational valves and antisiphon devices. This study shows that overdrainage is not limited to the vertical position but that pulse pressures that simulate rhythmic (eg, cardiac) and provoked (eg, Valsalva) physiological CSF pulsations increase outflow in both the horizontal and vertical positions and are dependent on compliance. A deeper understanding of the physiological parameters that affect intracranial pressure and flow through shunt systems is prerequisite to the development of novel valves.

Permanent Cerebrospinal Fluid Diversion in Adults With Posterior Fossa Tumors: Incidence and Predictors


Neurosurgery 89:987–996, 2021

Posterior fossa tumors (PFTs) can cause hydrocephalus. Hydrocephalus can persist despite resection of PFTs in a subset of patients requiring permanent cerebrospinal fluid (CSF) diversion. Characteristics of this patient subset are not well defined.

OBJECTIVE: To define preoperative and postoperative variables that predict the need for postoperative CSF diversion in adult patients with PFTs.

METHODS: We surveyed the CNS (Central Nervous System) Tumor Outcomes Registry at Emory (CTORE) for patients who underwent PFT resection at 3 tertiary-care centers between 2006 and 2019. Demographic, radiographic, perioperative, and dispositional data were analyzed using univariate and multivariate models.

RESULTS:We included 617 patients undergoing PFT resection for intra-axial (57%) or extraaxial (43%) lesions. Gross total resection was achieved in 62% of resections. Approximately 13% of patients required permanent CSF diversion/shunting. Only 31.5% of patients who required pre- or intraop external ventricular drain (EVD) placement needed permanent CSF diversion. On logistic regression, size, transependymal flow, use of perioperative EVD, postoperative intraventricular hemorrhage (IVH), and surgical complications were predictors of permanent CSF diversion. Preoperative tumor size was only independent predictor of postoperative shunting in patients with subtotal resection. In patients with intra-axial tumors, transependymal flow (P = .014), postoperative IVH (P = .001), surgical complications (P = .013), and extent of resection (P = .03) predicted need for shunting. In extra-axial tumors, surgical complications were the major predictor (P = .022).

CONCLUSION: Our study demonstrates that presence of preoperative hydrocephalus in patients with PFT does not necessarily entail the need for permanent CSF diversion. We report the major predictive factors for needing permanent CSF diversion.

Comparison Between Flow-Regulated and Gravitational Shunt Valves in the Treatment of Normal Pressure Hydrocephalus: Flow-Grav Study

Neurosurgery 89:413–419, 2021

Normal pressure hydrocephalus (NPH) is frequently treated with ventriculoperitoneal shunt (VPS) surgery. However, VPS implantation can lead to overdrainage and complications such as headaches, hygroma, and subdural hematoma due to a siphon effect in an upright position. Gravitational valves prevent overdrainage through positiondependent adjustment of valve resistance. Flow-regulated valves that increase resistance in presence of high cerebrospinal fluid flow may provide similar protection against overdrainage and present an alternative to gravitational valves.

OBJECTIVE: To compare gravitational and flow-regulated shunt valves in patients with symptomatic NPH.

METHODS: We performed a retrospective analysis of 97 patients suffering from NPH who underwent VPS implantation with a gravitational or a flow-regulated valve. The primary endpoint was the occurrence of hygroma or subdural hematoma. Secondary endpoints were neurological outcome (Kiefer score, Stein and Langfitt score, and NPH recovery rate), frequency of valve adjustments, and reoperations.

RESULTS: No significant differences in the occurrence of hygroma and subdural hematoma (11.4% for flow-regulated valves vs 5.7% for gravitational valves, P = .462) or response to treatment (77.3% vs 81.1%, P = .802) were found. Patients with flow-regulated valves required fewer valve adjustments (1.12 vs 2.02, P < .001) to reach their optimal neurological outcome and underwent fewer surgical revisions (11.4% vs 28.3%, P = .047).

CONCLUSION: Our data suggest that shunt therapy in NPH patients with a flow-regulated instead of a gravitational valve is safe and effective with a comparable clinical outcome and risk of overdrainage complications. Moreover, patients with flow-regulated valves may need fewer valve adjustments and reoperations.

CSF shunt valve occlusion—does CSF protein and cell count matter?

Acta Neurochirurgica (2021) 163:1991–1996

Shunt obstruction is a common cause of shunt failure in the treatment of hydrocephalus. Valve occlusion is traditionally believed to originate from elevated CSF protein or cellular components, although detailed evidence is scarce and contradictory. Therefore, this study aimed to examine CSF protein and cell count as risk factors for valve obstruction.

Methods We retrospectively examined 274 patients who underwent shunt placement for hydrocephalus between 2009 and 2018 and had at least 1 year follow-up. Age, aetiology of hydrocephalus, valve type, occurrence of revision, reason for revision and CSF protein and cell count at the time of shunt insertion and revision surgery were analysed.

Results Thirty-two of 274 patients (11.7%) required revision surgery due to valve occlusion. Mean time to revision was 143 days. CSF white blood cell (WBC) count but not protein was associated with valve occlusion overall. Of all obstructed valve patients, 25% showed CSF protein level within the normal range, whereas 13.6% of the patients overall showed greatly elevated CSF protein level without evidence of valve obstruction. Persistently elevated CSF protein level at the time of shunt revision was significantly associated with valve obstruction within 90 days of initial insertion (early occlusion). Children with congenital malformations and post-haemorrhagic patients were significantly overrepresented in the occlusion group, particularly in the early occlusion group.

Conclusion Pathological CSF values such as WBC count and persistently elevated protein level serves as a risk factor for early valve obstruction. Late obstruction occurs independent of normal CSF values. Infants are particularly prone to early and late valve obstructions. CSF protein level at shunt insertion is not predictive of valve occlusion.

Freehand stereotactic ventricular catheter insertion for ventriculoperitoneal shunts based on individualized radio-anatomical landmarks

Acta Neurochirurgica (2021) 163:1103–1112

The accurate placement of the ventricular catheter (VC) is critical in reducing the incidence of proximal failure of ventriculoperitoneal shunts (VPSs). The standard freehand technique is based on validated external anatomical landmarks but remains associated with a relatively high rate of VC malposition. Already proposed alternative methods have all their specific limitations. Herein, we evaluate the accuracy of our adapted freehand technique based on an individualized radio-anatomical approach. Reproducing the preoperative imaging on the patient’s head using common anatomical landmarks allows to define stereotactic VC coordinates to be followed at surgery.

Material and methods Fifty-five consecutive patients treated with 56 VPS between 11/2005 and 02/2020 fulfilled the inclusion criteria of this retrospective study. Burr hole coordinates, VC trajectory, and length were determined in all cases on preoperative computed tomography (CT) scan and were accurately reported on patients’ head. The primary endpoint was to evaluate VC placement accuracy. The secondary endpoint was to evaluate the rate and nature of postoperative VC-related complications.

Results Our new technique was applicable in all patients and no VC-related complications were observed. Postoperative imaging showed VC optimally placed in 85.7% and sub-optimally placed in 14.3% of cases. In all procedures, all the holes on the VC tip were found in the ventricular system.

Conclusions This simple individualized technique improves the freehand VC placement in VPS surgery, making its accuracy comparable to that of more sophisticated and expensive techniques. Further randomized controlled studies are required to compare our results with those of the other available techniques.

Readmission and reoperation for hydrocephalus: a population-based analysis across the spectrum of age

J Neurosurg 134:1210–1217, 2021

Hydrocephalus is a common, chronic illness that generally requires lifelong, longitudinal, neurosurgical care. Except at select research centers, surgical outcomes in the United States have not been well documented. Comparative outcomes across the spectrum of age have not been studied.

METHODS Data were derived for the year 2015 from the Nationwide Readmissions Database, a product of the Healthcare Cost and Utilization Project of the Agency for Healthcare Research and Quality. In this data set patients are assigned state-specific codes that link repeated discharges through the calendar year. Discharges with diagnostic codes for hydrocephalus were extracted, and for each patient the first discharge defined the index admission. The study event was readmission. Observations were censored at the end of the year. In a similar fashion the first definitive surgical procedure for hydrocephalus was defined as the index operation, and the study event was reoperation for hydrocephalus or complications. Survival without readmission and survival without reoperation were analyzed using life tables and Kaplan- Meier plots.

RESULTS Readmission rates at 30 days ranged between 15.6% and 16.8% by age group without significant differences. After the index admission the first readmission alone generated estimated hospital charges of $2.25 billion nationwide. Reoperation rates at 30 days were 34.9% for infants, 39.2% for children, 47.4% for adults, and 32.4% for elders. These differences were highly significant. More than 3 times as many index operations were captured for adults and elders as for infants and children. Estimated 1-year reoperation rates were 74.2% for shunt insertion, 63.9% for shunt revision, but only 34.5% for endoscopic third ventriculostomy. Univariate associations with survival without readmission and survival without reoperation are presented.

CONCLUSIONS In the United States hydrocephalus is predominantly a disease of adults. Surgical outcomes in this population-based study were substantially worse than outcomes reported from research centers. High reoperation rates after CSF shunt surgery accounted for this discrepancy.

Free-hand stereotactic ventricular catheter insertion technique based on radio-anatomical landmarks

Acta Neurochirurgica (2021) 163:1097–1102

Accurate ventricular catheter (VC) placement plays an important role in reducing the risk of ventriculoperitoneal shunt failure. Free-hand VC insertion is associated with a significant misplacement rate. Consequently, several expensive alternative methods that are unfortunately not available worldwide have been used. To overcome these limitations, we developed a simple surgical technique based on radio-anatomical landmarks aimed at reducing VC’s misplacements.

Method We reproduce the preoperative imaging on the patient’s head using common anatomical landmarks. This allows defining stereotactic VC coordinates to be followed during the surgical procedure.

Conclusion This simple and cost-effective method improves VC insertion accuracy.

The endoscopic supraorbital translaminar approach

Acta Neurochirurgica (2021) 163:635–641

Resection of lesions located within the third ventricle presents a surgical challenge. Several approaches have been developed in an attempt to obtain maximal resection, while minimizing brain retraction. In this work, we assess the surgical exposure and maneuverability of the endoscopic supraorbital translaminar approach (ESTA), a potential alternative to fenestrate the lamina terminalis and approach the third ventricle by using the endoscope through a keyhole supraorbital-eyebrow craniotomy.

Methods Five cadaveric heads were used to assess the corridor depth, area of exposure, and viewing angles offered by the ESTA. One additional utilized specimen provided a stepwise dissection of the approach.

Results The ESTA was successfully performed in all specimens. Depth of the surgical corridor from the craniotomy to the ipsilateral internal carotid artery (ICA), lamina terminalis, and contralateral carotid were 70.7 ± 2.9 mm, 73.2 ± 2.9 mm, and 78.9 ± 4.1 mm, respectively. Viewing angle referenced to the ipsilateral ICA was 6.5 ± 4.2°, while the viewing angle for the lamina terminalis was 25.8 ± 4.3°. The surgical exposure provided by the ESTA was 1655 ± 255 mm2.

Conclusions The ESTA provides a wide surgical view of the lamina terminalis and may be potentially used to approach lesions located in the anterior third of the third ventricle. As a pure endoscopic approach, the ESTA requires minimal brain retraction, while affords good visualization of targeted lesions around the lamina terminalis. The ESTA uses an anterolateral approach and so provides a short and straightforward approach to these structures.

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