Clinical applications of ultrasound in neurosurgery and neurocritical care: A narrative review

Abstract

Ultrasonography (USG) has become an invaluable tool in the assessment of neurocritical patients in the operating theaters and critical care units. Due to its easy availability, reliability, safety, and repeatability, neuro-intensivists and neuro-anesthesiologists utilize USG to make a diagnosis, assess prognosis, and decide upon treatment. In neurocritical care units, USG has myriad indications for use, both systemic and neurologic. The neurological indications include the assessment of stroke, vasospasm, traumatic brain injury, brain death, acute brain damage, optic nerve sheath diameter, and pupillary reflexes to name a few. The systemic indications range from assessment of cardio-pulmonary function and intravascular volume status to detection of deep venous thromboses, vocal cord assessment in intubated patients, placement of central venous catheters, and percutaneous tracheostomy. In this narrative review, we iterate the clinical applications of USG in neuroanesthesia and neurocritical care, which we penned after searching relevant databases in PubMed, Medline, Ovid, and Google Scholar by using terms such as ‘applications of transcranial Doppler’, ‘optic nerve sheath diameter’, ‘USG applications in the critical care unit’, and so on. Our search database includes several research papers, neurocritical care books, review articles, and scientific databases. This article reviews various applications of USG in neuroanesthesia, neurosurgery, and neurocritical care.

Fig. 1

Transcranial Doppler image of vasospasm. Note the high mean flow velocity of 141 cm/s, indicating mild vasospasm (red box).

Fig. 2

Transcranial Doppler findings in brain death. A: Normal flow pattern. B: Oscillating flow pattern and absence of diastolic flow. C: Short systolic spikes.

Fig. 3

Use of TEE in sitting position craniotomy. A: Positioning of patient for a sitting craniotomy. B: TEE showing the presence of hyperechoic normal saline bubbles inside RA (blue arrow) after injection through CVC, signifying the location of the tip of central line. C: TEE showing the presence of PFO (blue circle). D: TEE with color doppler showing shunting of blood from RA to LA via PFO. E: Agitation of saline between two syringes before injection through CVC for the detection of PAE. F: The presence of hyperechoic air bubbles in the LA (blue arrow) after injection of agitated saline through the CVC. Note the full opacification of RA due to injection of agitated saline. Abbreviations: TEE: transesophageal echocardiography: PFO: patent foramen ovale; LA: left atrium; RA: right atrium; CVC: central venous catheter.

Fig. 4

Ocular ultrasound. A: Optic nerve sheath diameter measured 3 mm behind the globe. B: Ultrasound of pupils.

Fig. 5

Lung ultrasound. A: Normal lung ultrasound showing sea-shore pattern on M-mode (right) and A-lines (left). B: The presence of consolidation, and tissue shred-sign (arrow mark). C: Barcode or stratosphere sign on M-mode in pneumothorax (arrow mark).

Fig. 6

Ultrasound for deep vein thrombosis. A. Hyperechoic thrombus (white arrow) seen inside the lumen of femoral vein (blue circle). B. Note the flow in femoral artery and lack of flow in femoral vein (blue circle) in Doppler mode.

Fig. 7

Airway ultrasound showing the cricothyroid membrane (blue arrow).