Book contents
- Frontmatter
- Dedication
- Contents
- PREFACE
- Acknowledgments
- Part II Neurological Disorders
- 3 Public Health
- 4 Epilepsy
- 5 Stroke
- 6 Neurological Infections
- 7 Protozoal Andhelminthic Infections
- 8 Neurological Illness in HIV Disease
- 9 Coma and Transient Loss of Consciousness
- 10 Paraplegia Non Traumatic
- 11 Disorders of Peripheral Nerves
- 12 Cranial Nerve Disorders
- 13 Myopathies and Myasthenia Gravis
- 14 Movement Disorders and Motor Neurone Disease
- 15 Headache and Facial Pain
- 16 Intracranial Tumours
- 17 Dementia
- 18 Inherited Neurological Disorders
- 19 Head and Spinal Injury
- 20 Care in Neurology
- INDEX
- ABBREVIATIONS
- USEFUL WEBSITES
9 - Coma and Transient Loss of Consciousness
from Part II - Neurological Disorders
- Frontmatter
- Dedication
- Contents
- PREFACE
- Acknowledgments
- Part II Neurological Disorders
- 3 Public Health
- 4 Epilepsy
- 5 Stroke
- 6 Neurological Infections
- 7 Protozoal Andhelminthic Infections
- 8 Neurological Illness in HIV Disease
- 9 Coma and Transient Loss of Consciousness
- 10 Paraplegia Non Traumatic
- 11 Disorders of Peripheral Nerves
- 12 Cranial Nerve Disorders
- 13 Myopathies and Myasthenia Gravis
- 14 Movement Disorders and Motor Neurone Disease
- 15 Headache and Facial Pain
- 16 Intracranial Tumours
- 17 Dementia
- 18 Inherited Neurological Disorders
- 19 Head and Spinal Injury
- 20 Care in Neurology
- INDEX
- ABBREVIATIONS
- USEFUL WEBSITES
Summary
Loss or alteration in consciousness is a very common clinical disorder. This can be transient lasting seconds or minutes as occurs in syncope and seizures or more prolonged as occurs in coma. Coma is by definition a state of impaired consciousness during which the patient is unrousable by external stimuli. In states of coma the patient remains in a sleep like state with no purposeful movements or response to any external stimuli. These can be measured by the Glasgow Coma Scale which defines coma as a GCS ≤ 8/15. Coma can be caused by disorders that affect either a part of the brain focally or the whole brain diffusely (Figs. 9.1-4). The causes of coma are generally classified as intracranial or extracranial and are outlined in Table 9.1. Episodes of transient loss of consciousness are by definition intermittent and usually sudden events from which the patient recovers fully. These arise either from the disorders of the cardiovascular system with an acute reduction of blood flow to the brain (syncope) or a disruption in brain electrical activity (seizure). The chapter outlines the main mechanisms, causes, investigations and management of coma and syncope. The student should aim to be familiar with these and be able to investigate and manage a patient presenting with loss of consciousness.
Pathophysiology
Consciousness is a person's awareness of themselves and their surroundings. Normal consciousness is maintained by an intact reticular activating system in the brain stem and its central connections to the thalamus and cerebral hemispheres. The reticular activating system keeps us awake and alert during the waking hours. Disorders that physically affect these areas can lead to disordered arousal, awareness and to altered states of consciousness. A focal brain lesion occurring below the tentorium (Figs.9.1 & 2) interfering with the reticular activating system can result in coma whereas a focal lesion occurring above the tentorium in one cerebral hemisphere results in coma only if the contralateral side of the brain is simultaneously involved or compressed (Fig.9.3) Diffuse lesions which affect the function of the brain as a whole including the reticular activating system can result in coma (Fig.9.4).
ASSESSMENT
Acute
Coma is an acute life threatening condition and evaluation needs to be quick, comprehensive and may involve starting emergency management even before the cause is established.
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- Neurology in AfricaClinical Skills and Neurological Disorders, pp. 211 - 228Publisher: Cambridge University PressPrint publication year: 2015