User:Cepedac

As a Boston College junior enrolled in the BI481 Introduction to Neuroscience course, I have joined a group to undertake the class assignment of improving an existing Wikipedia article. It will be our endeavor to edit and expand the incomplete neuroscience-related article, by adding relevant information to it throughout the semester, under the supervision of our professor Joseph Burdo.

The class link is User:NeuroJoe/BI481 Spring 2011

I will be working in a group with Philip Johnson and Sean Dikdan. The topic my group and I have decided to research is the Cushing reflex.

Our project proposal, The Cushing Reflex, details what information we plan to add to the existing article.

Signs and Symptoms
The Cushing reflex is characterized by increased intracranial pressure. . Its classical symptoms are an increase in systolic and pulse pressure, bradycardia, and irregular respiration. These physiological symptoms can be indicative of cerebral ischemia as well as compression of arterioles.

In response to rising ICP, respiratory rate increases. The increase in ventilation is exhibited as an increase in rate rather than depth of ventilation, so the Cushing reflex is often associated with slow, irregular breathing. Mayer waves are also a sign of the Cushing reflex, as can be observed from blood pressure traces or ECGs. Mayer waves are the symptoms of a physiological response to falling blood flow, responding with an increase in blood pressure.

Research
Though 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 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 et al. showed that Cushing reflex directed by autonomic nervous system, since its physiological change has to do with the sympathetic nervous system and parasympathetic nervous system balance. 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 decrease, 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 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. The possibility that heightened sensitivity of neurological response system leading to arterial hypertension is 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.