"Point of care transcranial Doppler (TCD) ultrasound has been described as a tool to supplement the physical exam in patients with suspected neurologic catastrophes 4. The most commonly cited method for measuring midline shift with transcranial Doppler utilises the transtemporal window to sequentially measure the distance from the ipsilateral temporal bone to the third ventricle followed by the distance from the contralateral temporal bone to the third ventricle; subtraction of the latter value from the former divided by two is then conventionally reported as the midline shift (MLS) measurement, with zero being the expected value in a nonpathological state. A negative value implies a shift toward the observer, and positive values represent a midline shift away from one's point of insonation 3."
"A midline shift of 5 mm or more is significant and is an indication for surgery; especially for operating on a mass or lesion or evacuating brain haematoma. Midline shift of less than 5 mm may be treated conservatively for those who are alert, without any neurological deficit, but requires close monitoring. A repeat CT brain is justified if there is any neurological deterioration 6."