# Transcranial Doppler Pulsatility Index and MRI Findings in Meningoencephalitis: A Pilot Observational Retrospective Cohort Study in Critically Ill Patients

## TL;DR

This study explores how TCCD pulsatility index and MRI can help monitor and predict outcomes in critically ill patients with meningoencephalitis.

## Contribution

The study introduces the integration of TCCD pulsatility index with MRI for early prognostic assessment in meningoencephalitis.

## Key findings

- TCCD pulsatility index ≤ 1.25 was linked to favorable outcomes and symmetrical MRI findings.
- PI > 1.25 correlated with poor prognosis and preceded MRI-detectable damage.
- Combining PI with ASL MRI improved understanding of perfusion asymmetries and prognosis.

## Abstract

Background: Meningoencephalitis is a complex inflammatory condition of the CNS that can result in significant morbidity and mortality in critically ill adults. Accurate and timely neuromonitoring is essential for guiding management and improving outcomes. This study aimed to descriptively evaluate the prognostic value of early TCCD monitoring, particularly the pulsatility index, and its integration with conventional and perfusion MRI in patients with meningoencephalitis. Methods: We present an observational, retrospective, cohort study involving ten adult patients (median age 56 years, IQR 45.5–68.5; mean 55.9, range 35–76) with neurological syndromes caused by suspected or confirmed infectious meningoencephalitis. Etiologies included bacterial meningitis/meningoencephalitis (50%), viral meningoencephalitis (10%), neurotoxoplasmosis (10%), progressive multifocal leukoencephalopathy (10%), and undetermined origin (20%). Patients underwent TCCD and MRI within 24 h. In five cases, standard MRI sequences were acquired, while in the remaining five, perfusion imaging was performed using Arterial Spin Labelling (ASL). A favorable outcome was defined as survival with neurological recovery (Glasgow Outcome Scale > 5) at ICU discharge. Results: TCCD-derived PI provided valuable information on cerebral hemodynamics. PI values ≤ 1.25 were associated with favorable clinical outcomes and symmetrical MRI findings. Conversely, PI > 1.25 correlated with poor prognosis and often preceded MRI-detectable structural damage. When combined with ASL, PI mirrored the detected perfusion asymmetries and was associated with poor prognosis in fatal cases. Conclusions: Bedside TCCD can offer real-time assessment of cerebrovascular dynamics and, when integrated with conventional and ASL MRI, could enhance the understanding of pathophysiological processes in meningoencephalitis, supporting timely and informed decisions in neurocritical care.