MHFP Publications

Translational Research

Translation is the process of turning observations in the laboratory, clinic and community into interventions that improve the health of individuals and the public — from diagnostics and therapeutics to medical procedures and behavioral changes.

Skull base drilling: How coolants can reduce thermal and physical damage?

Thermal and physical damage in skull base drilling using gas cooling modes: FEM simulation and experimental evaluation

Highlights

  • The FEM simulation indicated that the efficiency of CO2 gas coolants in reducing the maximum temperature, thrust force and torque was more than conventional cooling modes.
  • CO2 gas coolants had minimum cracks and the slightest surface defects after skull drilling.
  • The similar effect of repeated drillings on thrust force and torque was less than the temperature in all cooling modes.
  • The repeated drillings did not have considerable effects on the maximum and durability of temperature in the CO2 cooling modes.
  • The external CO2 gas coolant was led to an optimal skull base drilling with minimum risks of thermal and physical damages and drill bit breakage.
The role of operating variables in improving the performance of skull base grinding

Control of the thermal and physical damage during skull base grinding is of great importance. We assess the effects of bur material (3 materials), angle of the bur (10 angles), bur diameter (10 diameters), gas coolant (4 coolants), and grinding time (10 times) to evaluate the role of operating variables in thermal and physical damage during skull bone grinding. After validation of finite element analysis (FEA) results with experimental data, the temperature in the grinding site and axial force are calculated using FEA. The use of a diamond bur leads to at least 24.48 and 12.9% reduction in thermal and physical damage, respectively. A change in angle of the bur from 0º to 90º leads to a 19.76–31.62 times increment in axial force. An increase in bur diameter from 1 to 5.5 mm led to 10.78–14.36% and 23.43–43.90% increase in maximum temperature and axial force, respectively. However, a bur diameter between 2.5 and 4 mm could provide enough grinding force with less thermal damage. Skull base grinding with dry (D) and normal saline (NS) coolants was always accompanied with thermal damage. The results of maximum and duration of temperature, axial force, and surface defect evaluation show CO2 coolants (especially internal CO2 coolant) are the best options to decrease thermal damage. The equations of temperature and axial force were estimated by regression analysis. This may be used as a guideline for neurosurgeons to control damage during skull base grinding and can also be helpful for the programming of robot-assisted skull grinding during surgery.

Hydrocephalus: Can intracranial compliance predict clinical oscillations?

Cerebrospinal fluid hydrocephalus shunting: cisterna magna, ventricular frontal, ventricular occipital

Despite advances in cerebrospinal fluid shunting technology, complications remain a significant concern. There are some contradictions about the effectiveness of proximal catheter entry sites that decrease shunt failures. We aim to compare efficiency of shunts with ventricular frontal, ventricular occipital, and cisterna magna entry sites. The systemic search was conducted in the database from conception to February 16, 2022 following guidelines of PRISMA. Between 2860 identified articles, 24 articles including 6094 patients were used for data synthesis. The aggregated results of all patients showed that “overall shunt failure rate per year” in mixed hydrocephalus with ventricular frontal and occipital shunts, and cisterna magna shunt (CMS) were 9.0%, 12.6%, and 30.7%, respectively. The corresponding values for “shunt failure rate” due to obstruction were 15.3%, 31.5%, and 10.2%, respectively. The similar results for “shunt failure rate” due to infection were 11.3%, 9.1%, and 27.2%, respectively. The related values for “shunt failure rate” due to overdrainage were 2.9%, 3.9%, and 13.6%, respectively. CMS was successful in the immediate resolution of clinical symptoms. Shunting through an occipital entry site had a greater likelihood of inaccurate catheter placement and location. Contrary to possible shunt failure due to overdrainage, the failure likelihood due to obstruction and infection in pediatric patients was higher than that of mixed hydrocephalus patients. In both mixed and pediatric hydrocephalus, obstruction and overdrainage were the most and least common complications of ventricular frontal and occipital shunts, respectively. The most and least common complications of mixed CMS were infection and obstruction, respectively.

A New Definition for Intracranial Compliance to Evaluate Adult Hydrocephalus After Shunting

The clinical application of intracranial compliance (ICC), ∆V/∆P, as one of the most critical indexes for hydrocephalus evaluation was demonstrated previously. We suggest a new definition for the concept of ICC (long-term ICC) where there is a longer amount of elapsed time (up to 18 months after shunting) between the measurement of two values (V1 and V2 or P1 and P2). The head images of 15 adult patients with communicating hydrocephalus were provided with nine sets of imaging in nine stages: prior to shunting, and 1, 2, 3, 6, 9, 12, 15, and 18 months after shunting. In addition to measuring CSF volume (CSFV) in each stage, intracranial pressure (ICP) was also calculated using fluid–structure interaction simulation for the noninvasive calculation of ICC. Despite small increases in the brain volume (16.9%), there were considerable decreases in the ICP (70.4%) and CSFV (80.0%) of hydrocephalus patients after 18 months of shunting. The changes in CSFV, brain volume, and ICP values reached a stable condition 12, 15, and 6 months after shunting, respectively. The results showed that the brain tissue needs approximately two months to adapt itself to the fast and significant ICP reduction due to shunting. This may be related to the effect of the “viscous” component of brain tissue. The ICC trend between pre-shunting and the first month of shunting was descending for all patients with a “mean value” of 14.75 ± 0.6 ml/cm H2O. ICC changes in the other stages were oscillatory (nonuniform). Our noninvasive long-term ICC calculations showed a nonmonotonic trend in the CSFV–ICP graph, the lack of a linear relationship between ICC and ICP, and an oscillatory increase in ICC values during shunt treatment. The oscillatory changes in long-term ICC may reflect the clinical variations in hydrocephalus patients after shunting.

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