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Aswin Chari, Marek Czosnyka, Hugh K. Richards, John D. Pickard, and Zofia H. Czosnyka


The Cambridge Shunt Evaluation Laboratory was established 20 years ago. This paper summarizes the findings of that laboratory for the clinician.


Twenty-six models of valves have been tested long-term in the shunt laboratory according to the expanded International Organization for Standardization 7197 standard protocol.


The majority of the valves had a nonphysiologically low hydrodynamic resistance (from 1.5 to 3 mm Hg/[ml/min]), which may result in overdrainage related to posture and during nocturnal cerebral vasogenic waves. A long distal catheter increases the resistance of these valves by 100%–200%. Drainage through valves without a siphon-preventing mechanism is very sensitive to body posture, which may result in grossly negative intracranial pressure. Siphon-preventing accessories offer a reasonable resistance to negative outlet pressure; however, accessories with membrane devices may be blocked by raised subcutaneous pressure. In adjustable valves, the settings may be changed by external magnetic fields of intensity above 40 mT (exceptions: ProGAV, Polaris, and Certas). Most of the magnetically adjustable valves produce large distortions on MRI studies.


The behavior of a valve revealed during testing is of relevance to the surgeon and may not be adequately described in the manufacturer's product information. The results of shunt testing are helpful in many circumstances, such as the initial choice of shunt and the evaluation of the shunt when its dysfunction is suspected.

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Mehdi Khan, Jaber Paktiawal, Rory J. Piper, Aswin Chari, and Martin M. Tisdall


In children with drug-resistant epilepsy (DRE), resective, ablative, and disconnective surgery may not be feasible or may fail. Neuromodulation in the form of deep brain stimulation (DBS) and responsive neurostimulation (RNS) may be viable treatment options, however evidence for their efficacies in children is currently limited. This systematic review aimed to summarize the literature on DBS and RNS for the treatment of DRE in the pediatric population. Specifically, the authors focused on currently available data for reported indications, neuromodulation targets, clinical efficacy, and safety outcomes.


PRISMA guidelines were followed throughout this systematic review (PROSPERO no. CRD42020180669). Electronic databases, including PubMed, Embase, Cochrane Library, OpenGrey, and CINAHL Plus, were searched from their inception to February 19, 2021. Inclusion criteria were 1) studies with at least 1 pediatric patient (age < 19 years) who underwent DBS and/or RNS for DRE; and 2) retrospective, prospective, randomized, or nonrandomized controlled studies, case series, and case reports. Exclusion criteria were 1) letters, commentaries, conference abstracts, and reviews; and 2) studies without full text available. Risk of bias of the included studies was assessed using the Cochrane ROBINS-I (Risk of Bias in Non-randomised Studies - of Interventions) tool.


A total of 35 studies were selected that identified 72 and 46 patients who underwent DBS and RNS, respectively (age range 4–18 years). Various epilepsy etiologies and seizure types were described in both cohorts. Overall, 75% of patients had seizure reduction > 50% after DBS (among whom 6 were seizure free) at a median (range) follow-up of 14 (1–100) months. In an exploratory univariate analysis of factors associated with favorable response, the follow-up duration was shorter in those patients with a favorable response (18 vs 33 months, p < 0.05). In the RNS cohort, 73.2% of patients had seizure reduction > 50% after RNS at a median (range) follow-up of 22 (5–39) months. On closer inspection, 83.3% of patients who had > 50% reduction in seizures actually had > 75% reduction, with 4 patients being seizure free.


Overall, both DBS and RNS showed favorable response rates, indicating that both techniques should be considered for pediatric patients with DRE. However, serious risks of overall bias were found in all included studies. Many research needs in this area would be addressed by conducting high-quality clinical trials and establishing an international registry of patients who have undergone pediatric neuromodulation, thereby ensuring robust prospective collection of predictive variables and outcomes.

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Aswin Chari, Angelos G. Kolias, Thomas Santarius, Simon Bond, and Peter J. Hutchinson


The incidence of chronic subdural hematoma (CSDH) is expected to increase substantially over the next 25 years. Continuing refinement of techniques for surgical evacuation is essential for optimizing patient outcomes. A novel technique involving a hollow screw, which is threaded through a twist-drill hole in the cranium and then connected to a closed drainage system, has been increasing in popularity. The aim of this systematic review is to collate and analyze the published experience with this novel technique and to evaluate its efficacy in comparison with the other surgical treatment methods.


This systematic review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and has been registered with the PROSPERO International Prospective Register of Systematic Reviews (registration number CRD42013003544). MEDLINE, Web of Knowledge, EMBASE, and the Cochrane Database of Systematic Reviews were searched for published series involving more than 10 patients treated with these new techniques.


Nine eligible studies were found (6 case series and 3 case-control studies) comprising 796 patients treated with these new techniques. Pooled analysis showed a “success rate” of 77.6% (95% CI 74.6%–80.4%), recurrence rate of 22.4%, and in-hospital mortality of 1.4%.


This systematic review adds further evidence to the pool of data assessing the safety and efficacy of the use of this novel, minimally invasive technique for the treatment for CSDH. Overall, twist-drill craniostomy with hollow screws appears to be safe and effective. Class I evidence is necessary to optimize the surgical management of patients with CSDH.

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Aswin Chari, Martin M. Tisdall, and Hani J. Marcus