Prognosis in Coma and Related Disorders of Consciousness and Mechanisms Underlying Outcomes

This chapter looks at the difficulty in predicting the outcome for patients with severe brain damage. Brain death, in principle, is conceptually a single biologic state with an unequivocal future, while severe brain injuries span a wide range of outcomes depending on a number of variables that include not only the degree of neurologic injury, but also the presence and severity of medical complications. The chapter looks in detail at the process of recovery after coma. It examines the various factors that influence recovery, such as duration of coma, presence of secondary injuries, age, motor findings, biochemical markers, electrophysiological markers, and multivariate modeling. It looks at a number of underlying causes of coma and how they relate to prognosis.

Management of Frequently Encountered Causes of Unconsciousness

This chapter presents a diagnostic and management outline to approach commonly encountered conditions associated unconsciousness. Once the specific cause is identified, attention should turn to dealing with the set of problems inherent to the underlying disorder. As it is not possible to cover all aspects of treatment of all possible causes of stupor and coma comprehensively, this chapter focuses instead on the management of frequently encountered pathologies within each of the main categorical clinical diagnoses: supratentorial or infratentorial compressive lesions; supratentorial or infratentorial destructive lesions; metabolic, diffuse, or multifocal coma. Management of psychogenic coma is discussed in Chapter 6.

Psychogenic Unresponsiveness

Chapter 6 explores psychiatric causes of unresponsiveness, which must be differentiated from organic causes of stupor and coma. The chapter notes that several psychiatric disorders can result in psychogenic unresponsiveness. These include conversion reaction, catatonic stupor, a dissociative or “fugue” state, and factitious disorder or malingering. The chapter looks at these in turn. Various diagnostic tests are described in detail, including the electroencephalogram, magnetic resonance imaging, computed tomographic imaging, caloric testing, and the “Amytal interview.” Sections describes the diagnosis and treatment of catatonia, psychogenic seizures (which must be differentiated from epileptic seizures), and cerebellar mutism. The authors emphasize the importance of treating patients with psychiatric causes of unresponsiveness with compassion and understanding.

Structural Causes of Stupor and Coma

Chapters 3 is the first of two chapters to discuss pathophysiology and specific causes of structural injury to the brain that result in defects of consciousness. It divides structural lesions causing coma into compressive and destructive lesions. It further indicates that lesions could be supratentorial, compressing, or destroying the diencephalon and upper midbrain, or infratentorial, directly affecting the pons and cerebellum. A physician attempting to determine the cause of coma resulting from a structural lesion must establish, first, the site of the lesion, determining whether the lesion is supratentorial or infratentorial, and, second, whether the lesion is causing its symptoms by compression or destruction or both.

Disorders of Consciousness in Clinical Practice

“Disorders of Consciousness in Clinical Practice” considers the ethical, legal, and policy considerations of working with patients and families with severe brain injury. Topics include professional obligations to patients with disorders of consciousness and the ethical implications of coma, brain death and the vegetative and minimally conscious state as well as their diagnostic classification based on behavioral and neuroimaging assessment. The normative challenge of covert consciousness is considered. Clinical, ethical and communication strategies for working with patients with impaired decision-making capacity and their families and surrogates are presented along a typical trajectory of care from initial presentation, intensive care, and discharge to rehabilitation and/or long-term care. End-of-life care, neuropalliation, and bereavement are also discussed as are ancillary care obligations to this marginalized and vulnerable population. Broader policy needs such as access to care is discussed in the context of civil and disability rights.

Metabolic and Diffuse Encephalopathies: Disruption of the Internal Milieu

Chapter 5 examines the broad range of metabolic causes of unconsciousness and the specific treatments they require. The main feature distinguishing diffuse or metabolic impairment of consciousness is that it is normally not associated with focal neurological findings that would suggest a structural lesion of the brain. However, there are some features of the neurological examination of patients with metabolic encephalopathies that can help to pinpoint the cause of the disturbance. In addition, there are some findings on examination that may appear to be due to focal lesions, but which can be due to diffuse or metabolic disease. The chapter first examines the diagnostic features of metabolic encephalopathies. It then looks at the internal metabolic milieu in which the brain functions normally. It also considers specific types of metabolic and diffuse disturbances of that internal milieu that can cause encephalopathy. Finally, it considers various endogenous and exogenous toxins that produce toxic encephalopathies.

Examination of the Comatose Patient

Chapter 2 defines a brief but informative neurologic examination that is necessary to determine if reduced consciousness has a structural cause (and therefore may require immediate imaging and perhaps surgical treatment) or a metabolic cause (in which case the diagnostic approach can be more lengthy and extensive). The authors stress that a coma or any alteration of consciousness is a medical emergency, and, as such, the physician must begin examination and treatment simultaneously. The examination must be thorough, but brief. The chapter also describes some of the physical findings that distinguish structural from nonstructural causes of stupor and coma.

Pathophysiology of Signs and Symptoms of Coma

Chapter 1 provides some important background information on the pathophysiology of impaired consciousness, as well as on the signs and symptoms that accompany it. It starts with definitions of key terms: consciousness, acutely altered states of consciousness, and subacute or chronic alterations of consciousness, as well as the definitions for stupor, coma, and other states of altered consciousness. It looks at how to approach the diagnosis of the comatose patient, and it then explains the physiology and pathophysiology of consciousness and coma. Finally, it describes three types of brain damage that may lead to altered consciousness or coma: bilateral hemispheric damage, diencephalic injury, and upper brainstem injury.

Brain Death

This chapter considers the issue of brain death. The cornerstone of the diagnosis of brain death is a careful and sure clinical neurologic examination. In addition, a thorough evaluation of clinical history, neuroradiologic studies, and laboratory tests needs to be carried out to rule out potential confounding variables. The diagnosis of brain death rests on two major and indispensable tenets. The first is that the cause of brain nonfunction must be inherently irreversible. The second is that the vital structures of the brain necessary to maintain consciousness and independent vegetative survival are damaged beyond all possible recovery. It looks at how to determine that brain death has occurred. It goes on to outline the clinical signs for brain death. The chapter also looks at the differences between brain death and prolonged coma. Finally, it explains the management of the brain dead patient.

Initial Management of Patients with Stupor and Coma

This chapter provides a general approach to the emergency care of comatose patients. It presents a clinical regimen for the diagnosis and management of patients suffering from stupor or coma. Of all the acute problems in clinical medicine, as the chapter explains, none is more challenging than the prompt diagnosis and effective management of the patient in coma. This is largely because the causes of coma are so many and the physician possesses only a limited time in which to make the appropriate diagnostic and therapeutic judgments. The authors detail basic emergency procedures to evaluate and support the essential airway, breathing, and circulation, and then move through a methodical, step-by-step examination and evaluation of all body systems, focusing on eye and pupillary reactions, motor responses, reflexes, and muscle tone.