Absent CORNEAL REFLEX
Absent VESTIBULO-OCULAR REFLEX
No cranial motor response to somatic (physical) stimulation
Absent gag and cough re?exes
No respiratory e?ort in response to APNOEA despite adequate concentrations of CARBON DIOXIDE in the arterial blood.... Medical Dictionary
The control centre of the whole nervous system is the brain, which is located in the skull or cranium. As well as controlling the nervous system it is the organ of thought, speech and emotion. The central nervous system controls the body’s essential functions such as breathing, body temperature (see HOMEOSTASIS) and the heartbeat. The body’s various sensations, including sight, hearing, touch, pain, positioning and taste, are communicated to the CNS by nerves distributed throughout the relevant tissues. The information is then sorted and interpreted by specialised areas in the brain. In response these initiate and coordinate the motor output, triggering such ‘voluntary’ activities as movement, speech, eating and swallowing. Other activities – for example, breathing, digestion, heart contractions, maintenance of BLOOD PRESSURE, and ?ltration of waste products from blood passing through the kidneys – are subject to involuntary control via the autonomic system. There is, however, some overlap between voluntary and involuntary controls.... Medical Dictionary
Severe head injuries cause unconsciousness for hours or many days, followed by loss of memory before and after that period of unconsciousness. The skull may be fractured; there may be ?ts in the ?rst week; and there may develop a blood clot in the brain (intracerebral haematoma) or within the membranes covering the brain (extradural and subdural haematomata). These clots compress the brain, and the pressure inside the skull – intracranial pressure – rises with urgent, life-threatening consequences. They are identi?ed by neurologists and neurosurgeons, con?rmed by brain scans (see COMPUTED TOMOGRAPHY; MRI), and require urgent surgical removal. Recovery may be complete, or in very severe cases can be marred by physical disabilities, EPILEPSY, and by changes in intelligence, rational judgement and behaviour. Symptoms generally improve in the ?rst two years.
A minority of those with minor head injuries have complaints and disabilities which seem disproportionate to the injury sustained. Referred to as the post-traumatic syndrome, this is not a diagnostic entity. The complaints are headaches, forgetfulness, irritability, slowness, poor concentration, fatigue, dizziness (usually not vertigo), intolerance of alcohol, light and noise, loss of interests and initiative, DEPRESSION, anxiety, and impaired LIBIDO. Reassurance and return to light work help these symptoms to disappear, in most cases within three months. Psychological illness and unresolved compensation-claims feature in many with implacable complaints.
People who have had brain injuries, and their relatives, can obtain help and advice from Headwat and from www.neuro.pmr.vcu.edu and www.biausa.org... Medical Dictionary
Tumours All masses cause varying combinations of headache and vomiting – symptoms of raised pressure within the inexpansible bony box formed by the skull; general or localised epileptic ?ts; weakness of limbs or disordered speech; and varied mental changes. Tumours may be primary, arising in the brain, or secondary deposits from tumours arising in the lung, breast or other organs. Some brain tumours are benign and curable by surgery: examples include meningiomas and pituitary tumours. The symptoms depend on the size and situation of the mass. Abscesses or blood clots (see HAEMATOMA) on the surface or within the brain may resemble tumours; some are removable. Gliomas ( see GLIOMA) are primary malignant tumours arising in the glial tissue (see GLIA) which despite surgery, chemotherapy and radiotherapy usually have a bad prognosis, though some astrocytomas and oligodendronogliomas are of low-grade malignancy. A promising line of research in the US (in the animal-testing stage in 2000) suggests that the ability of stem cells from normal brain tissue to ‘home in’ on gliomal cells can be turned to advantage. The stem cells were chemically manipulated to carry a poisonous compound (5-?uorouracil) to the gliomal cells and kill them, without damaging normal cells. Around 80 per cent of the cancerous cells in the experiments were destroyed in this way.
Clinical examination and brain scanning (CT, or COMPUTED TOMOGRAPHY; magnetic resonance imaging (MRI) and functional MRI) are safe, accurate methods of demonstrating the tumour, its size, position and treatability.
Strokes When a blood vessel, usually an artery, is blocked by a clot, thrombus or embolism, the local area of the brain fed by that artery is damaged (see STROKE). The resulting infarct (softening) causes a stroke. The cells die and a patch of brain tissue shrinks. The obstruction in the blood vessel may be in a small artery in the brain, or in a larger artery in the neck. Aspirin and other anti-clotting drugs reduce recurrent attacks, and a small number of people bene?t if a narrowed neck artery is cleaned out by an operation – endarterectomy. Similar symptoms develop abruptly if a blood vessel bursts, causing a cerebral haemorrhage. The symptoms of a stroke are sudden weakness or paralysis of the arm and leg of the opposite side to the damaged area of brain (HEMIPARESIS), and sometimes loss of half of the ?eld of vision to one side (HEMIANOPIA). The speech area is in the left side of the brain controlling language in right-handed people. In 60 per cent of lefthanders the speech area is on the left side, and in 40 per cent on the right side. If the speech area is damaged, di?culties both in understanding words, and in saying them, develops (see DYSPHASIA).
Degenerations (atrophy) For reasons often unknown, various groups of nerve cells degenerate prematurely. The illness resulting is determined by which groups of nerve cells are a?ected. If those in the deep basal ganglia are a?ected, a movement disorder occurs, such as Parkinson’s disease, hereditary Huntington’s chorea, or, in children with birth defects of the brain, athetosis and dystonias. Modern drugs, such as DOPAMINE drugs in PARKINSONISM, and other treatments can improve the symptoms and reduce the disabilities of some of these diseases.
Drugs and injury Alcohol in excess, the abuse of many sedative drugs and arti?cial brain stimulants – such as cocaine, LSD and heroin (see DEPENDENCE) – can damage the brain; the e?ects can be reversible in early cases. Severe head injury can cause localised or di?use brain damage (see HEAD INJURY).
Cerebral palsy Damage to the brain in children can occur in the uterus during pregnancy, or can result from rare hereditary and genetic diseases, or can occur during labour and delivery. Severe neurological illness in the early months of life can also cause this condition in which sti? spastic limbs, movement disorders and speech defects are common. Some of these children are learning-disabled.
Dementias In older people a di?use loss of cells, mainly at the front of the brain, causes ALZHEIMER’S DISEASE – the main feature being loss of memory, attention and reasoned judgement (dementia). This a?ects about 5 per cent of the over-80s, but is not simply due to ageing processes. Most patients require routine tests and brain scanning to indicate other, treatable causes of dementia.
Response to current treatments is poor, but promising lines of treatment are under development. Like Parkinsonism, Alzheimer’s disease progresses slowly over many years. It is uncommon for these diseases to run in families. Multiple strokes can cause dementia, as can some organic disorders such as cirrhosis of the liver.
Infections in the brain are uncommon. Viruses such as measles, mumps, herpes, human immunode?ciency virus and enteroviruses may cause ENCEPHALITIS – a di?use in?ammation (see also AIDS/HIV).
Bacteria or viruses may infect the membrane covering the brain, causing MENINGITIS. Viral meningitis is normally a mild, self-limiting infection lasting only a few days; however, bacterial meningitis – caused by meningococcal groups B and C, pneumococcus, and (now rarely) haemophilus – is a life-threatening condition. Antibiotics have allowed a cure or good control of symptoms in most cases of meningitis, but early diagnosis is essential. Severe headaches, fever, vomiting and increasing sleepiness are the principal symptoms which demand urgent advice from the doctor, and usually admission to hospital. Group B meningococcus is the commonest of the bacterial infections, but Group C causes more deaths. A vaccine against the latter has been developed and has reduced the incidence of cases by 75 per cent.
If infection spreads from an unusually serious sinusitis or from a chronically infected middle ear, or from a penetrating injury of the skull, an abscess may slowly develop. Brain abscesses cause insidious drowsiness, headaches, and at a late stage, weakness of the limbs or loss of speech; a high temperature is seldom present. Early diagnosis, con?rmed by brain scanning, is followed by antibiotics and surgery in hospital, but the outcome is good in only half of a?ected patients.
Cerebral oedema Swelling of the brain can occur after injury, due to engorgement of blood vessels or an increase in the volume of the extravascular brain tissue due to abnormal uptake of water by the damaged grey (neurons) matter and white (nerve ?bres) matter. This latter phenomenon is called cerebral oedema and can seriously a?ect the functioning of the brain. It is a particularly dangerous complication following injury because sometimes an unconscious person whose brain is damaged may seem to be recovering after a few hours, only to have a major relapse. This may be the result of a slow haemorrhage from damaged blood vessels raising intracranial pressure, or because of oedema of the brain tissue in the area surrounding the injury. Such a development is potentially lethal and requires urgent specialist treatment to alleviate the rising intracranial pressure: osmotic agents (see OSMOSIS) such as mannitol or frusemide are given intravenously to remove the excess water from the brain and to lower intracranial pressure, buying time for de?nitive investigation of the cranial damage.... Medical Dictionary
All reversible pharmacological, metabolic, endocrine and physiological causes must be excluded, and there should be no doubt that irreversible brain damage has occurred. Two senior doctors carry out diagnostic tests to con?rm that brain-stem re?exes are absent. These tests must be repeated after a suitable interval before death can be declared. Imaging techniques are not required for death to be diag-... Medical Dictionary
It usually begins at puberty – although young children can be a?ected – and tends to stop in middle age: in women, for example, attacks often cease after MENOPAUSE. It frequently disappears during pregnancy. The disorder tends to run in families. In susceptible individuals, attacks may be provoked by a wide variety of causes including: anxiety, emotion, depression, shock, and excitement; physical and mental fatigue; prolonged focusing on computer, television or cinema screens; noise, especially loud and high-pitched sounds; certain foods – such as chocolate, cheese, citrus fruits, pastry; alcohol; prolonged lack of food; irregular meals; menstruation and the pre-menstrual period.
Anything that can provoke a headache in the ordinary individual can probably precipitate an attack in a migrainous subject. It seems as if there is an inherited predispostion that triggers a mechanism whereby in the migrainous subject, the headache and the associated sickness persist for hours, a whole day or even longer.
The precise cause is not known, but the generally accepted view is that in susceptible individuals, one or other of these causes produces spasm or constriction of the blood vessels of the brain. This in turn is followed by dilatation of these blood vessels which also become more permeable and so allow ?uid to pass out into the surrounding tissues. This combination of dilatation and outpouring of ?uid is held to be responsible for the headache.
Two types of migraine have been recognised: classical and common. The former is relatively rare and the headache is preceded by a slowly extending area of blindness in one or both eyes, usually accompanied by intermittent ‘lights’. The phenomenon lasts for up to 30 minutes and is followed by a bad, often unilateral headache with nausea, sometimes vomiting and sensitivity to light. Occasionally, passing neurological symptoms such as weakness in a limb may accompany the attack. The common variety has similar but less severe symptoms. It consists of an intense headache, usually situated over one or other eye. The headache is usually preceded by a feeling of sickness and disturbance of sight. In 15–20 per cent of cases this disturbance of sight takes the form of bright lights: the so-called AURA of migraine. The majority of attacks are accompanied by vomiting. The duration of the headache varies, but in the more severe cases the victim is usually con?ned to bed for 24 hours.
Treatment consists, in the ?rst place, of trying to avoid any precipitating factor. Patients must ?nd out which drug, or drugs, give them most relief, and they must always carry these about with them wherever they go. This is because it is a not uncommon experience to be aware of an attack coming on and to ?nd that there is a critical quarter of an hour or so during which the tablets are e?ective. If not taken within this period, they may be ine?ective and the unfortunate victim ?nds him or herself prostrate with headache and vomiting. In addition, su?erers should immediately lie down; at this stage a few hours’ rest may prevent the development of a full attack.
When an attack is fully developed, rest in bed in a quiet, darkened room is essential; any loud noise or bright light intensi?es the headache or sickness. The less food that is taken during an attack the better, provided that the individual drinks as much ?uid as he or she wants. Group therapy, in which groups of around ten migrainous subjects learn how to relax, is often of help in more severe cases, whilst in others the injection of a local anaesthetic into tender spots in the scalp reduces the number of attacks. Drug treatment can be e?ective and those a?icted by migraine may ?nd a particular drug or combination of drugs more suitable than others. ANALGESICS such as PARACETAMOL, aspirin and CODEINE phosphate sometimes help. A combination of buclizine hydrochloride and analgesics, taken when the visual aura occurs, prevents or diminishes the severity of an attack in some people. A commonly used remedy for the condition is ergotamine tartrate, which causes the dilated blood vessels to contract, but this must only be taken under medical supervision. In many cases METOCLOPRAMIDE (an antiemetic), followed ten minutes later by three tablets of either aspirin or paracetamol, is e?ective if taken early in an attack. In milder attacks, aspirin, with or without codeine and paracetamol, may be of value. SUMATRIPTAN (5-hydroxytryptamine [5HT1] AGONIST – also known as a SEROTONIN agonist) is of value for acute attacks. It is used orally or by subcutaneous injection, but should not be used for patients with ischaemic heart disease. Naratriptan is another 5HT1 agonist that is an e?ective treatment for acute attacks; others are almotriptan, rizariptan and zolmitriptan. Some patients ?nd beta blockers such as propranolol a valuable prophylactic.
People with migraine and their relatives can obtain help and guidance from the Migraine Action Association.... Medical Dictionary
II. Optic, to the eye (sight).
Trochlear, to eye-muscles.
VI. Trigeminal, to skin of face.
VII. Facial, to muscles of face.
VIII. Vestibulocochlear, to ear (hearing and balancing).
IX. Glossopharyngeal, to tongue (taste).
X. Vagus, to heart, larynx, lungs, and stomach.
XI. Spinal accessory, to muscles in neck.
XII. Hypoglossal, to muscles of tongue.... Medical Dictionary