TCD diastolic velocity decay and pulsatility index increment in PVS cases

Area of Science:

• Neurology
• Neurophysiology
• Medical Imaging

Background:

• Persistent vegetative state (PVS) assessment benefits from functional neuroimaging.
• Previous studies used PET and SPECT, showing reduced metabolism and perfusion in PVS patients.
• Trans cranial Doppler (TCD) is a noninvasive bedside technique for intracranial blood flow assessment, with limited application in PVS.

Observation:

• TCD was used to assess intracranial circulation in five PVS patients.
• Four patients had hypoxic encephalopathy; one had a basilar artery top embolic infarct.
• Internal carotid artery siphon was assessed via orbital insonation when temporal bone windows were unsuitable.

Findings:

• Systolic velocity remained within normal limits (44-62 cm/s) in all PVS patients.
• Diastolic amplitude and end-diastolic velocity were reduced across all patients.
• Pulsatility index (PI) was elevated in all assessed PVS patients.

Implications:

• Reduced TCD diastolic velocity and increased PI in PVS may suggest uncoupling of cerebral blood flow and metabolic rate.
• This uncoupling could stem from decreased cerebral glucose consumption and oxygen uptake post-brain injury.
• TCD offers a valuable, noninvasive method for evaluating cerebrovascular dynamics in PVS patients.