Relationship between the shape of intracranial pressure pulse waveform and computed tomography characteristics in patients after traumatic brain injury
Authors: Kazimierska Agnieszka , Uryga Agnieszka , Mataczyński Cyprian , Czosnyka Marek , Lang Erhard W. , Kasprowicz Magdalena ,   CENTER-TBI high-resolution sub-study participants and investigators, Anke Audny , Beer Ronny , Bellander Bo-Michael , Beqiri Erta , Buki Andras , Cabeleira Manuel , Carbonara Marco , Chieregato Arturo , Citerio Giuseppe , Clusmann Hans , Czeiter Endre , Depreitere Bart , Ercole Ari , Frisvold Shirin , Helbok Raimund , Jankowski Stefan , Kondziella Daniel , Koskinen Lars-Owe , Kowark Ana , Menon David K. , Meyfroidt Geert , Moeller Kirsten , Nelson David , Piippo-Karjalainen Anna , Radoi Andreea , Ragauskas Arminas , Raj Rahul , Rhodes Jonathan , Rocka Saulius , Rossaint Rolf , Sahuquillo Juan , Sakowitz Oliver , Smielewski Peter , Stocchetti Nino , Sundstrom Nina , Takala Riikka , Tamosuitis Tomas , Tenovuo Olli , Unterberg Andreas , Vajkoczy Peter , Vargiolu Alessia , Vilcinis Rimantas , Wolf Stefan , Younsi Alexander , Zeiler Frederick A. 
Published: November 2023

Abstract
Background
Midline shift and mass lesions may occur with traumatic brain injury (TBI) and are associated with higher mortality and morbidity. The shape of intracranial pressure (ICP) pulse waveform reflects the state of cerebrospinal pressure–volume compensation which may be disturbed by brain injury. We aimed to investigate the link between ICP pulse shape and pathological computed tomography (CT) features.

Methods
ICP recordings and CT scans from 130 TBI patients from the CENTER-TBI high-resolution sub-study were analyzed retrospectively. Midline shift, lesion volume, Marshall and Rotterdam scores were assessed in the first CT scan after admission and compared with indices derived from the first 24 h of ICP recording: mean ICP, pulse amplitude of ICP (AmpICP) and pulse shape index (PSI). A neural network model was applied to automatically group ICP pulses into four classes ranging from 1 (normal) to 4 (pathological), with PSI calculated as the weighted sum of class numbers. The relationship between each metric and CT measures was assessed using Mann–Whitney U test (groups with midline shift > 5 mm or lesions > 25 cm3 present/absent) and the Spearman correlation coefficient. Performance of ICP-derived metrics in identifying patients with pathological CT findings was assessed using the area under the receiver operating characteristic curve (AUC).

Results
PSI was significantly higher in patients with mass lesions (with lesions: 2.4 [1.9–3.1] vs. 1.8 [1.1–2.3] in those without; p << 0.001) and those with midline shift (2.5 [1.9–3.4] vs. 1.8 [1.2–2.4]; p < 0.001), whereas mean ICP and AmpICP were comparable. PSI was significantly correlated with the extent of midline shift, total lesion volume and the Marshall and Rotterdam scores. PSI showed AUCs > 0.7 in classification of patients as presenting pathological CT features compared to AUCs ≤ 0.6 for mean ICP and AmpICP.

Conclusions
ICP pulse shape reflects the reduction in cerebrospinal compensatory reserve related to space-occupying lesions despite comparable mean ICP and AmpICP levels. Future validation of PSI is necessary to explore its association with volume imbalance in the intracranial space and a potential complementary role to the existing monitoring strategies.