Regional pressure and temperature differences across the injured human brain : comparisons between intraparenchymal and ventricular measurements

Introduction: Intraparenchymal, multimodality sensors are commonly used in the management of patients with severe traumatic brain injury (TBI). The ‘gold standard’, based on accuracy, reliability and cost for intracranial pressure (ICP) monitoring is within the cerebral ventricle (external strain gauge). There are no standards yet for intracerebral temperature monitoring and little is known of temperature differences between brain tissue and ventricle. The aim of the study therefore was to determine pressure and temperature differences at intraparenchymal and ventricular sites during five days of continuous neurominitoring. Methods: Patients with severe TBI requiring emergency surgery. Inclusion criteria: patients who required ICP monitoring were eligible for recruitment. Two intracerebral probe types were used: a) intraventricular, dual parameter sensor (measuring pressure, temperature) with inbuilt catheter for CSF drainage: b) multiparameter intraparenchymal sensor measuring pressure, temperature and oxygen partial pressure. All sensors were inserted during surgery and under aseptic conditions. Results: Seventeen patients, 12 undergoing neurosurgery (decompressive craniectomy n=8, craniotomy n=4) aged 21–78 years were studied. Agreement of measures for 9540 brain tissue-ventricular temperature ‘pairs’ and 10,291 brain tissue-ventricular pressure ‘pairs’ were determined using mixed model to compare mean temperature and pressure for longitudinal data. There was no significant overall difference for mean temperature (p=0.92) or mean pressure readings (p=0.379) between tissue and ventricular sites. With 95.8% of paired temperature readings within 2SD (−0.4 to 0.4°C) differences in temperature between brain tissue and ventricle were clinically insignificant. For pressure, 93.5% of readings pairs fell within the 2SD range (−9.4756 to 7.8112 mmHg) (Fig. 2). However, for individual patients, agreement for mean tissue-ventricular pressure differences was poor on occasions. Conclusions: There is good overall agreement between paired temperature measurements obtained from deep white matter and brain ventricle in patients with and without early neurosurgery. For paired ICP measurements, 93.5% of readings were within 2SD of mean difference. Whilst the majority of paired readings were comparable (within 10mmHg) clinically relevant tissue-ventricular dissociations were noted. Further work is required to unravel the events responsible for short intervals of pressure dissociation before tissue pressure readings can be definitively accepted as a reliable surrogate for ventricular pressure.</p

Growth of Asymptomatic Intracranial Fusiform Aneurysms

PurposeGrowth of intracranial fusiform aneurysms (IFA) may become clinically problematic through a mass effect or rupture. We investigated the growth rate and factors contributing to growth in asymptomatic untreated IFA.MethodAs a retrospective review, we assessed patients diagnosed with asymptomatic IFA between August 2000 and September 2014, all untreated. No acute or symptomatic dissecting lesions were considered. Clinical and serial angiographic follow-up data were analyzed, defining growth as expansion&gt;2mm in one or more dimensions. A binary logistic regression model and Kaplan-Meier method were applied for statistical analysis.ResultsThe mean follow-up in the 82 eligible patients was 47.7 months (range 12-190 months). Among them, 7 aneurysms (8.5%, 2.1% per aneurysm year) demonstrated growth (in any dimension). In univariate analysis, height and multiplicity of aneurysms emerged as significant factors in terms of growth. Height remained an independent risk factor in the binary logistic regression model, with receiver operating curves indicating a threshold of 6.9mm initial height in determining IFA growth (area under the curve 0.804). Of the patients six (except one who underwent endovascular treatment) were observed during continued follow-up monitoring. All six lesions were stable in serial imaging tests, without further detectable growth or rupture (mean 33 months).ConclusionMost (91.5%) of the asymptomatic and untreated IFAs studied proved to be stable, with no continued growth; however, because aneurysm height proved to be independently predictive of growth (lesions&gt;6.9mm being at risk), periodic imaging is required in those left untreated. Growing but still asymptomatic aneurysms call for the utmost caution and care in decision-making.N