Brain stem death

The concept of brain and brain stem death developed from the observation of apnoeic comatose patients. In the UK, the diagnosis of brain stem death is made by clinically testing brain stem function once specific pre-conditions have been met. The exact definition of brain death and some details regarding the tests required to make this diagnosis vary across the globe. However, the majority of tests carried out are similar to those in the UK. In this review we define brain stem death and the clinical tests used to confirm it. The use of ancillary testing can have a role in patients where clinical tests are not possible and this is also discussed.     

Brain death

Summary Following the research of Giessen Neurosurgery on primary and secondary lesions of the hypothalamo-pituitary system and the brainstem over a period of more than 30 years, cerebral failure and death does not represent a uniform syndrome but consists of several, well characterized syndromes of irreversible hypothalamo-pituitary, mesencephalic and bulbar failure. The specific syndromes are described in detail. The diagnosis is based on establishing complete irreversible damage of specific vital basal functions such as hypothalamo-pituitary transmission, water-and electrolyte metabolism, temperature regulation, circulation and respiration. The common feature of all types is the irreversible break-down of the complex central neurogenous and/or neurohumoral regulatory system. The permanent and irreversible loss of central regulation and modulation means at the same time the complete cessation of the specific human cortical function, the death of the whole brain. Only in bulbar failure with primary irreversible cessation of respiration artificial respiration can maintain the autonomous functions of the heart for a limited time. It is indicated when organ explantation is to be considered. Complete and irreversible isolated loss of cortical function abolishes the normal human life, but does not mean death of the remaining vegetating human being.Presented at the meeting of the Working Group of the Pontificia Academia Scientiarum on The artificial prolongation of life and the exact determination of the moment of death, Vatican City, October 19–21, 1985.Dedicated to Prof. Dr. Jean Brihaye at the occasion of his 65th anniversary.     

Medical and legal considerations of brain death

Brain death was first defined in 1968, and since then laws on determining death have been implemented in all countries with active organ transplantation programs. As a prerequisite, the aetiology of brain death has to be known, and all reversible causes of coma have to be excluded. The regulations for the diagnosis of brain death are most commonly given by the national medical associations, and they vary between countries. Thus, the guidelines given in the medical textbooks are not universally applicable. The diagnosis is based on clinical examination, but confirmatory tests, such as angiography or EEG, are allowed on most occasions. Brain death is followed by cardiovascular and hormonal changes, which have implications in the management of a potential organ donor. Spinal reflexes are preserved, and motor and haemodynamic responses are frequently observed in brain dead patients.     

Reversibility of severe brain stem dysfunction in children

Summary The very popular concept of brain death can lead to a defeatist attitude when confronted by a patient with severe brain stem dysfunction. This problem is compounded by the constant controversy surrounding the establishing of criteria to determine brain death. Many young doctors tend to accept the precondition of irreversibility as being any condition that is not explicitly listed in the examples of potentially reversible conditions. In children, however, with compressive brain stem dysfunction, decompressive surgery can lead to a reversal of the dysfunction.In the last three years, we have had the opportunity to observe 5 children who were deeply comatose and apnoeic. All were suffering from compression of the brain stem and experienced dramatic return of brain stem function following emergency decompression.The implications of these findings on the therapeutic attitude towards compressive brain stem lesions in children are exposed. In children with severe brain stem dysfunction, and no evidence of brain stem destruction, decompressive surgery should be undertaken before a diagnosis of brain death is considered.     

Brain stem necrosis after irradiation of pituitary adenoma

A case of late delayed necrosis in the left temporal lobe, midbrain, and pons following irradiation of a pituitary adenoma is reported. In this patient, disturbance of consciousness appeared just after removal of the necrosis of the temporal lobe which had been considered preoperatively to be a temporal lobe tumor; autopsy also revealed radiation necrosis in the midbrain and pons. Radiation necrosis, especially of the brain stem, after pituitary irradiation is reviewed, and the mechanism of development of disturbance of consciousness after removal of the necrosis of the temporal lobe in this case is discussed.     

The use of cerebral computed tomographic angiography as an ancillary investigation to support a clinical diagnosis of death using neurological criteria: a consensus guideline

This multidisciplinary consensus statement was produced following a recommendation by the Faculty of Intensive Care Medicine to develop a UK guideline for ancillary investigation, when one is required, to support the diagnosis of death using neurological criteria. A multidisciplinary panel reviewed the literature and UK practice in the diagnosis of death using neurological criteria and recommended cerebral CT angiography as the ancillary investigation of choice when death cannot be confirmed by clinical criteria alone. Cerebral CT angiography has been shown to have 100% specificity in supporting a diagnosis of death using neurological criteria and is an investigation available in all acute hospitals in the UK. A standardised technique for performing the investigation is described alongside a reporting template. The panel were unable to make recommendations for ancillary testing in children or patients receiving extracorporeal membrane oxygenation.     

Brain death: Determination with brain stem evoked potentials and radionuclide isotope studies

Summary Thirty-three patients fulfilling the clinical criteria for brain death were tested by Brainstem Auditory Evoked Potentials (BAEP) and Radionuclide Cerebral Angiography and Brain Perfusion Studies. There was a significant correlation between the BAEP and radionuclide study outcomes. All patients with absence of BAEP showed no cerebral perfusion. These findings, added to the clinical findings, resulted in a final diagnosis of brain death in all patients. It is concluded that BAEP and Radionuclide Cerebral Perfusion studies are useful adjuncts for proving that brain death has really occurred.     

Brain death: practicability of evoked potentials

Multimodally evoked potentials were registered in 85 patients who fulfilled the criteria for brain death. While samatosensory and visual evoked potentials have been found to be of limited value for the diagnosis of brain death, the stepwise abolition of brain stem auditory evoked potentials (BAEP) confirmed brain death in 26 out of 85 patients, i. e. 31%.Registration of the abolition of BAEP is concluded to be a safe and acceptable confirmatory test. It is, however, more feasible for institutions, in which BAEP are analysed routinely. In spite of all efforts sequential BAEP could not be used for the diagnosis of brain death in the majority of cases either because of absence of reproducible responses at the initial registration or because the patient was already apnoic at the time of the initial BAEP. Assuming that bilateral preservation of wave I has the same significance as the stepwise abolition of BAEP, since it also proves the integrity of the peripheral receptor, BAEP are relevant for the declaration of brain death in approximately 30% of patients.     

Brain death and intraocular pressure

The authors report on the behavior of the intraocular pressure of 20 patients who had sustained severe head injury. The 8 patients who retained normal intraocular pressure all survived. The 12 patients who developed intraocular hypotony all suffered brain death. Although optic disc edema was not noted in any brain-dead patients, we did find signs of fundus ischemia in most.     

Epidermoid Cyst Involving the Brain Stem

Brain stem epidermoid cysts are extremely rare. We describe an unusual case of prepontine epidermoid cyst with a large part of the tumour insinuating itself into the pons. Microsurgical total excision of tumour was done without producing any new neurological deficits. Cases reported in the literature either had high mortality/morbidity or were only subtotally removed. Relevant literature is reviewed.     

Post-traumatic brain stem distortion: a case report

BACKGROUND

Primary traumatic brain stem injury (BSI) lesions are found most frequently in the dorsal or dorsolateral midbrain, whereas distortion of the brain stem itself is exceedingly rare.

CASE REPORT

We present a 20-year-old woman with a rare brain stem injury caused by a violent motor vehicle collision. Magnetic resonance imaging at 2 months after injury revealed marked brain stem distortion with loss of the normal shape at the midbrain and pons, which were displaced anteriorly in association with the fracture of the clivus. Moreover, the medulla oblongata showed a loose winding configuration. At discharge about 5 months after injury, the Glasgow Outcome Scale was severe disability.

CONCLUSION

This BSI was caused by reciprocal actions of fracture of the clivus and the direct effect on the brain stem caused by acceleration or rotational forces.     

Permanent brain arrest as the sole criterion of death in systemic circulatory arrest

Historically, there has been a tendency to think that there are two types of death: circulatory and neurological. Holding onto this tendency is making it harder to navigate emerging resuscitative technologies, such as extracorporeal membrane oxygenation and the recent well-publicised experiment that demonstrated the possibility of restoring cellular function to some brain neurons 4 h after normothermic circulatory arrest (decapitation) in pigs. Attempts have been made to respond to these difficulties by proposing a unified brain-based criterion for human death, which we call ‘permanent brain arrest’. The clinical characteristics of permanent brain arrest are the permanent loss of capacity for consciousness and permanent loss of all brainstem functions, including the capacity to breathe. These losses could arise from a primary brain injury or as a result of systemic circulatory arrest. We argue that permanent brain arrest is the true and sole criterion for the death of human beings and show that this is already implicit in the circulatory-respiratory criterion itself. We argue that accepting the concept of permanent cessation of brain function in patients with systemic permanent circulatory arrest will help us better navigate the medical advances and new technologies of the future whilst continuing to provide sound medical criteria for the determination of death.     

基于器官捐献视角论我国脑死亡标准的立法

近年来我国器官捐献事业快速发展,然而我国尚未对脑死亡标准进行立法确认。本文介绍了国内外脑死亡标准立法现状和我国现阶段公民逝世后器官捐献实行的死亡判定标准,从器官捐献视角探讨了我国进行脑死亡标准立法的必要性,并基于实际国情对脑死亡标准立法的形式和内容提出了建议,旨在为开展脑死亡标准立法工作提供参考。