Cushing Reflex - Research Directions

Research Directions

Although a lot of progress has been made since 1901 when Harvey Cushing first expanded knowledge of what is now known as the Cushing reflex, there are still many aspects of the research that remain to be seen. The exact pathogenesis of the disease has yet to be determined. The possibility that intracranial pressure (ICP) may not be the sole cause of the Cushing reflex per se came from an occurrence of Cushing blood pressure response occurring before increased ICP. Some research observed symptoms of Cushing reflex, without the usual increased ICP and medullary anemia, suggesting other causes that still require research. Axial brain stem distortion could be the pathogenesis of Cushing reflex.

The nature of receptors mediating the Cushing response is also unknown. Some research suggests the existence of intracranial baroreceptors to trigger specific Cushing baroreceptor reflex. Experiments by Schmidt and his fellow researchers showed that the Cushing reflex is directed by autonomic nervous system, since its physiological change has to do with the balance of the sympathetic nervous system and parasympathetic nervous system. However, the specific relation between the autonomic nervous system response and the Cushing reflex and its symptoms has yet to be identified.

It has been determined that rate of respiration is affected by the Cushing reflex, though the respiratory changes induced are still an area which can use more research. Some researchers have reported apnea, while others have reported increased respiratory rates. Other researchers have found that increases in respiratory rate follow ICP decreases, while others say it is a response to ICP increase. One must also take into account the use of anesthetics in early experimentation. Research was initially performed on animals or patients under anesthesia. The anesthesia used in experiments have led to respiratory depression, which might have had effect on the results. Early experiments also put animal subjects under artificial ventilation, only allowing for limited conclusions about respiration in the Cushing reflex. The use of anesthetics proposes ideas for future research, since the creation of the Cushing response has been difficult to create under basal conditions or without anesthesia.

Some researchers have also suggested a long-term effect of the Cushing reflex. Thus far it has only been observed as an immediate acute response, but there has been some evidence to suggest that its effects could be prolonged, such as a long-term raise in blood pressure. Heightened sensitivity of neurological response systems leading to arterial hypertension is also possible, but has not been examined.

Although the Cushing reflex was primarily identified as a physiological response when blood flow has almost ceased, its activity has also been seen in fetal life. This activity has not been thoroughly investigated, so there is a need for more research in this area.

The underlying mechanisms of the reflex on a cellular level are yet to be discovered, and will likely be the next area of research if scientists and/or doctors chose to do so.