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Fulltext Pneumocephalus and air travel: an experimental investigation on the effects of aircraft cabin pressure on intracranial pressure

Lim E, Lan BL, Ooi EH, Low HL

Sci Rep, 2020 08 12;10(1):13626.
PMID: 32788610 DOI: 10.1038/s41598-020-70614-w

This study investigates the effects of aircraft cabin pressure on intracranial pressure (ICP) elevation of a pneumocephalus patient. We propose an experimental setup that simulates the intracranial hydrodynamics of a pneumocephalus patient during flight. It consists of an acrylic box (skull), air-filled balloon [intracranial air (ICA)], water-filled balloon (cerebrospinal fluid and blood) and agarose gel (brain). The cabin was replicated using a custom-made pressure chamber. The setup can measure the rise in ICP during depressurization to levels similar to that inside the cabin at cruising altitude. ΔICP, i.e. the difference between mean cruising ICP and initial ICP, was found to increase with ICA volume and ROC. However, ΔICP was independent of the initial ICP. The largest ΔICP was 5 mmHg; obtained when ICA volume and ROC were 20 ml and 1,600 ft/min, respectively. The postulated ICA expansion and the subsequent increase in ICP in pneumocephalus patients during flight were successfully quantified in a laboratory setting. Based on the quantitative and qualitative analyses of the results, an ICA volume of 20 ml and initial ICP of 15 mmHg were recommended as conservative thresholds that are required for safe air travel among pneumocephalus patients. This study provides laboratory data that may be used by doctors to advise post-neurosurgical patients if they can safely fly.
Posterior subthalamic area deep brain stimulation for treatment of tremor and dystonia in Wilson's disease

Low HL, Alexander SK, Misbahuddin A, Gillett GT

Brain Stimul, 2019 05 21;12(5):1304-1306.
PMID: 31138489 DOI: 10.1016/j.brs.2019.05.014
Comparison of posterior subthalamic area deep brain stimulation for tremor using conventional landmarks versus directly targeting the dentatorubrothalamic tract with tractography

Low HL, Ismail MNBM, Taqvi A, Deeb J, Fuller C, Misbahuddin A

Clin Neurol Neurosurg, 2019 Oct;185:105466.
PMID: 31466022 DOI: 10.1016/j.clineuro.2019.105466

OBJECTIVE: To compare posterior subthalamic area deep brain stimulation (PSA-DBS) performed in the conventional manner against diffusion tensor imaging and tractography (DTIT)-guided lead implantation into the dentatorubrothalamic tract (DRTT).
PATIENTS AND METHODS: Double-blind, randomised study involving 34 patients with either tremor-dominant Parkinson's disease or essential tremor. Patients were randomised to Group A (DBS leads inserted using conventional landmarks) or Group B (leads guided into the DRTT using DTIT). Tremor (Fahn-Tolosa-Marin) and quality-of-life (PDQ-39) scores were evaluated 0-, 6-, 12-, 36- and 60-months after surgery.
RESULTS: PSA-DBS resulted in marked tremor reduction in both groups. However, Group B patients had significantly better arm tremor control (especially control of intention tremor), increased mobility and activities of daily living, reduced social stigma and need for social support as well as lower stimulation amplitudes and pulse widths compared to Group A patients. The better outcomes were sustained for up to 60-months from surgery. The active contacts of Group B patients were consistently closer to the centre of the DRTT than in Group A. Speech problems were more common in Group A patients.
CONCLUSION: DTIT-guided lead placement results in better and more stable tremor control and fewer adverse effects compared to lead placement in the conventional manner. This is because DTIT-guidance allows closer and more consistent placement of leads to the centre of the DRTT than conventional methods.
Is There An Optimal Time for Performing Cranioplasties? Results from a Prospective Multinational Study

Quah BL, Low HL, Wilson MH, Bimpis A, Nga VDW, Lwin S, et al.

World Neurosurg, 2016 Oct;94:13-17.
PMID: 27368511 DOI: 10.1016/j.wneu.2016.06.081

BACKGROUND: The optimal timing of cranioplasty remains uncertain.
OBJECTIVE: We hypothesized that the risk of infections after primary cranioplasty in adult patients who underwent craniectomies for non-infection-related indications are no different when performed early or delayed. We tested this hypothesis in a prospective, multicenter, cohort study.
METHODS: Data were collected prospectively from 5 neurosurgical centers in the United Kingdom, Malaysia, Singapore, and Bangladesh. Only patients older than 16 years from the time of the non-infection-related craniectomy were included. The recruitment period was over 17 months, and postoperative follow-up was at least 6 months. Patient baseline characteristics, rate of infections, and incidence of hydrocephalus were collected.
RESULTS: Seventy patients were included in this study. There were 25 patients in the early cranioplasty cohort (cranioplasty performed before 12 weeks) and 45 patients in the late cranioplasty cohort (cranioplasty performed after 12 weeks). The follow-up period ranged between 16 and 34 months (mean, 23 months). Baseline characteristics were largely similar but differed only in prophylactic antibiotics received (P = 0.28), and primary surgeon performing cranioplasty (P = 0.15). There were no infections in the early cranioplasty cohort, whereas 3 infections were recorded in the late cohort. This did not reach statistical significance (P = 0.55).
CONCLUSIONS: Early cranioplasty in non-infection-related craniectomy is relatively safe. There does not appear to be an added advantage to delaying cranioplasties more than 12 weeks after the initial craniectomy in terms of infection reduction. There was no significant difference in infection rates or risk of hydrocephalus between the early and late cohorts.