Ocular lesions these include marked ocular hypotony, acutely raised intraocular pressure, central retinal vein occlusion, anterior ischaemic optic neuropathy and uveitis. It is due to venous stasis which results in the compression of the central retinal vein as it crosses the subdural and subarachnoid spaces. Unilateral versus Bilateral Papilloedema In majority of the cases with raised intracranial pressure, it is bilateral. However, unilateral cases as well as of unequal size do occur with raised intracranial pressure. General symptoms include headache which is made worse by coughing, sneezing or straining. Projectile vomiting (without nausea) is suggestive of raised intracranial pressure. Malignant hypertension, toxemia of pregnancy Head injury-cerebral oedema Meningitis, encephalitis Intracranial vascular lesion-subarachnoid haemorrhage, cavernous sinus thrombosis, etc. Pseudotumour cerebri-with toxicity of drugs, like tetracycline, nalidixic acid, vitamin-A, oral contraceptives and corticosteroids 1. There is a difference of 2-6 D between the vessels at the top and those on the retina. General fundus-Cotton wool soft exudates and both flame-shaped and punctate haemorrhages appear around the optic disc. The Optic Nerve 345 Early changes Late changes Differential Diagnosis Blurring of the optic disc margin is seen commonly in cases of: 1. Pseudoneuritis-In hypermetropia the lamina cribrosa is small and the nerve fibres are heaped up. Etiology It is due to the involvement of posterior ciliary artery and may be central retinal artery causing infarcts of the anterior part of the optic nerve and retina. Marked hyperaemia Venous dilatation and exudates are less marked Macular fan may be present occasionally. Minimum leakage of dye Presence of numbness, paresthesia, weakness and incoordination of limbs (demyelinating disease) Demyelinating disorder can be seen ii. Pathogenesis There are inflammatory changes in the nerve (true optic neuritis) or in the sheath (perineuritis). Pupil-Direct light reflex is sluggish or absent as the afferent path is involved. Neuroretinitis-When the serious inflammation spreads from the disc towards the neighbouring retina, it is called neuroretinitis. Visual Field Defects-A generalized depression of the visual field is the most common of visual defect. There is no effective treatment for idiopathic and hereditary optic neuritis and that associated with demyelinating disorders. Oral prednisolone therapy alone is contraindicated in the treatment of acute optic neuritis, since it was not shown to improve visual outcome and recurrence rate is high with this regime. If the brain shows lesions supportive of multiple sclerosis, the patient should receive immediate intravenous methylprednisolone (1 gm daily) for 3 days followed by oral prednisolone (1 mg/kg/day) for 11 days. Marcus Gunn pupil-There is lack of sustained constriction of the pupil to light in swinging flashlight test. Swinging flashlight test-A bright light is thrown on to one pupil and its constriction is noted. This process of swinging of light to and fro across the pupils is repeated several times so that there are equal impulses sent to the midbrain via the optic nerves. Field of vision-Central, paracentral, sectorial scotomas or ring-shaped scotoma around fixation point may be present 5.
They are distinguished from illusions by their complexity and the vivid colours and detail with which they are reported. They are first- or secondperson, non-distinct, like voices in a crowd, and not generally threatening. It is rare for a visual hallucination to be the source of any auditory hallucination (Inzelberg et al. An unexpected increase in sexual drive was noted by several authors soon after the introduction of levodopa (Barbeau 1969; Jenkins & Groh 1970). On occasions this might take the form of paraphilias (Harvey 1988; Cummings 1991; Quinn 1996). No particular feature of the disease has been shown to be associated with the emergence of psychosis (Friedman 1991). Several authors have noted that a number of their psychotic patients had a past psychiatric history of both affective and psychotic disorders (Mendis 1996; Sanchez-Ramos et al. Movement Disorders 769 That reports of psychoses became more frequent after the introduction of levodopa has led to a perception that there is a direct relationship between the two, i. Most obviously, despite the high prevalence of psychosis, most patients tolerate levodopa for many years without becoming psychotic. Psychosis has also been reported to complicate treatment with dopamine agonists, including bromocriptine (Burton et al. Recent evidence shows that psychosis is two to three times more likely with dopamine agonists than with levodopa (Rinne et al. Several authors claim that the psychoses seen with dopamine agonists are more florid and persistent than those seen with levodopa (Lieberman et al. High rates of vivid and abnormal dreams are seen in patients who had hallucinations or delusions (Moskovitz et al. Double vision, reduced visual acuity, impaired colour vision, impaired spatial contrast discrimination and impaired facial recognition have all been associated with hallucinations (Diederich et al. One conclusion might be that psychotic symptoms are related to the density of cortical Lewy bodies. There is evidence for the involvement of the dopamine, serotonin and acetylcholine neurotransmitter systems. Clearly, there is a role for the dopaminergic system, although the simple explanation of receptor hypersensitivity must be questioned. No differences were found between the two groups, suggesting equal levels of dopamine sensitivity. They suggested that hallucinations might arise from an imbalance of serotonin and dopamine. The association of cognitive impairment with hallucinations suggests a role for the cholinergic system. Reduced levels of cortical choline acetyltransferase have been found in psychotic patients (Perry et al. With advancing disease the burden of 770 Chapter 12 caring for the patient increases (Carter et al. Psychosis is the single greatest factor precipitating nursing home placement in parkinsonian patients (Goetz & Stebbins 1993; Aarsland et al. Goetz and Stebbins (1995) showed higher mortality in hallucinating patients, but a more recent study from the same group showed that prognosis has improved (Factor et al. The introduction of atypical antipsychotic medication brought hope that effective drug treatment would be possible. Despite an early randomised controlled trial showing disappointing results (Wolters et al. The Parkinson Study Group (1999) and the French Clozapine Parkinson Study Group (1999) performed randomised controlled trials which showed that clozapine was safe and effective at doses very much smaller than those used in the treatment of schizophrenia.
Decalcification or erosion of the posterior clinoid processes is an important indication of raised intracranial pressure, or the fossa may be enlarged due to a pituitary or suprasellar lesion. The pineal is calcified in approximately 50% of adults and may display shifts of the midline structures. Calcification within the body of a tumour can be of direct localising value, similarly calcification within the walls of a large cerebral aneurysm. Other rare conditions include calcification within the basal ganglia in hypoparathyroidism (see Chapter 10), calcification within the nodules in tuberose sclerosis or in the cysts of cysticercosis. The system is approximately 100 times more sensitive than conventional radiography systems, yet exposes the patient to no greater radiation dosage than a standard series of ordinary skull radiographs. There is no need for anaesthesia or any form of invasive procedure, rendering it entirely safe for patients who might be unfit for contrast neuroradiology. Within the cerebral substance variations in soft tissues of nearly similar absorption density may be displayed; thus the thalami and heads of the caudate nuclei are generally identifiable as discrete structures, also the internal capsule and optic radiations. The cortical grey matter mantle is visible over the surface of the cerebral hemispheres. Progressive refinements incorporated into more Clinical Assessment 133 recent machines have considerably increased the amount of detail displayed. In investigating cerebral pathology the scan may show displacements of normal intracranial contents, but in addition many focal pathological processes produce changes in brain absorption density that enable lesions to be displayed directly. Space-occupying lesions are readily shown, including tumours, abscesses and haematomas. Local cerebral oedema is demonstrated, and infarction is revealed as a region of low absorption density. A diffuse increase in absorption density is seen with meningiomas, colloid cysts and pituitary adenomas, whereas gliomas and metastases may be hyperdense or hypodense. A special advantage is the capacity to distinguish tumours from infarctions at an early stage, and in cases where angiography might well have been contraindicated. Intravenous injection of sodium iothalamate (Conray) can be used in doubtful cases to enhance the contrast between the tumour and surrounding brain tissue. In the management of strokes the differentiation between infarction and haemorrhage is relatively simple. This can be especially important if the patient is taking or due to take anticoagulants (Sandercock et al. The location, size and direction of propagation of intracerebral haematomas can be defined. After head injuries various important forms of cerebral pathology are displayed (see Chapter 4). High-speed imaging is performed during the bolus administration of intravenous contrast. From a single pass of contrast medium, a threedimensional reconstruction of the cerebral vasculature (including aneurysms and malformations) may be obtained that may then be inspected from any angle (Mazziotta 2000). Cerebral atrophy shows as enlargement of the ventricles, broadening of the sylvian and interhemispheric fissures, and widening of the cerebral sulci, much as after air encephalography. Significance of cerebral atrophy Sometimes neuroimaging shows changes that are hard to interpret, particularly where cerebral atrophy is concerned. It is often easier to assess distortion by a space-occupying lesion than to decide on the significance of minor ventricular enlargement. Occasionally, moreover, the ventricles may prove to be enlarged or the sulci prominent in patients who show no evidence of cerebral disorder. Such examples raise obvious diagnostic difficulties, and are a reminder that a range of normal variation must be allowed where the appearances of the brain are concerned. With regard to dementia there is usually an obvious association with evidence of atrophy, although this is not absolute in every case. Younger demented patients are more likely to show decisively abnormal findings, in comparison with their peers, whereas in the elderly there may be considerable overlap with healthy persons of equivalent age. Interestingly, however, patients over the age of 80 were significantly less likely to have large ventricles compared with those a decade or so younger, perhaps reflecting the more benign course of dementia in the very elderly. Hubbard and Anderson (1981) were able to show by detailed autopsy measurements that the ventricles were of normal size for age in approximately 40% of patients with senile dementia.
Further discussion is needed among researchers working with blindsight patients and among philosophers who desire to clean up our choice of words for describing the blindsight phenomenon. That direction of research needs to be extended beyond detection to object discrimination, as discussed in the preceding paragraph. Acknowledgments I thank Scott Slotnick and students in my freshman-sophomore seminar, "Will Robots See? This research was partly supported by grant R01 04776 from the National Eye Institute. Extrageniculate vision in hemianopic humans: Saccade inhibition by signals in the blind field. Signal detection analysis of residual vision in a field defect due to a post-geniculate lesion. In fact, in every realm of disorders in cognitive achievement, in impairments of perception, recognition memory and recall, language, problem solving, meaning, and motor-skill learning, robust hidden processes can be found. Striking dissociations separate that which can be processed and which aspect of that process is available to awareness (Weiskrantz 1991, 1997). It may also be the most promising example for analyzing the brain mechanisms involved, because much background neuroscience is known about of the intact visual system. Residual Visual Capacity via Extrastriate Pathways the problem started with primate animal research. It is not always appreciated that the eye sends a projection via the optic nerve not only along the well-studied geniculostriate pathway, but over parallel pathways to nine other targets in the brain (Cowey and Stoerig 1991), such as the superior colliculus and the pretectum in the midbrain. The geniculostriate pathway is certainly the largest, but the nongeniculate components are not trivial -they comprise about 150,000 fibers from each eye in the primate. Therefore, when the striate cortical target is removed in monkeys, good visual capacity can still be demonstrated, although of course it is altered both quantitatively and qualitatively in ways that are not our topic here (cf. Visual information has various routes by which it can reach not only the midbrain and diencephalon but also, via relays, the remaining visual "association" cortices, V2, V3. Moreover, the lateral geniculate itself does not degenerate absolutely as classically thought, but retains some intralaminar cells that project to the visual association cortex. Page 372 the paradox is then that human subjects-whose visual system is highly similar to that of the monkey-report that they are blind after visual-cortex damage in the part of the visual field affected by the damage (typically, after unilateral damage, in the larger part or all of the contralateral half visual field). The strategy requires one to abandon the typical approach to visual testing with human beings, which stems from the typical oral instruction (even if not explicitly stated): "Tell me what [or whether] you see". Rather, a forced-choice discrimination, or a reaching action with a limb, or an eye movement to an event is required even if the event is not seen. In other words, the testing had to have a basis similar to that actually used in animal visual testing, where we cannot ask the animal to report what it sees, but we do ask that it make a discriminative choice and we reward choices selectively. Of course, we normally assume that the animal "sees"-has visual experience-but that is only an assumption. Some patients could perform quite well on various visual discriminations even though they reported not actually "seeing" the stimuli projected to their "blind" fields. Subjects could reach for stimuli with reasonable accuracy, discriminate their orientation, their rough shape, and even discriminate between colors. The incidence and variations in blindsight are complex and far from settled; we discuss the subject elsewhere (Weiskrantz 1995, 1996). As in other areas of neuropsychology, much of the research has been focused on intensively studying a few patients who have a relatively pure defect, a reasonably restricted lesion (brain damage does not always conform to the analytical limits that would suit the experimenter), and are also willing to submit to the tens of thousands of testing trials that are entailed. He has been studied by several groups in the United Kingdom and the United States and in continental Europe. He was brain-damaged in a road accident more than 30 years ago, when he was 8 years old. Although the subject never "sees" or experiences in any way stimuli in the affected field, color can be discriminated. Blindsight Type 2 versus Type 1 the special status afforded in the blind field to rapidly transient events, which may well reflect their importance as danger signals in an evolutionary context, I call blindsight type 2. This mode includes discrimination (typically by "guessing") of color, orientation, reaching, and discrimination of slow movement or gradual onset of stimuli.
The abscess is revealed after scan enhancement and has a characteristic appearance: the capsule shows as a ring-shaped area of increased density surrounded by cerebral oedema. Treatment of cerebral abscess involves aspiration and excision followed by antibiotic therapy (Bernardini 2004; Moorthy & Rajshekhar 2008). With modern management the mortality has fallen progressively and the success rate for treatment is around 90%. Some degree of permanent incapacity may nonetheless persist, and epilepsy is liable to develop in up to 70% of cases. Intraventricular rupture and low initial Glasgow Coma Scale score are associated with poor outcomes (Takeshita et al. Cerebral anoxia often appears to be responsible, or the influence of toxins derived from the infecting microorganisms. More complex metabolic disturbances or the accumulation of toxic intermediate products must sometimes be postulated. However, in the infections considered below, there is more definite evidence of cerebral involvement by the disease process itself. The conditions are dealt with briefly, and textbooks of general medicine should be consulted for further details. Other infective processes Acute organic reactions may accompany many systemic infections, especially at the extremes of life. An obvious Lyme disease Lyme disease is caused by the spirochaete Borrelia burgdorferi, which is transmitted to humans through tick bites. It can lead to cutaneous, neurological, arthritic and cardiac manifestations, although the course is usually benign and self-limiting. The tick bite is followed by a characteristic rash (erythema migrans), which develops after some days or weeks and is often the pointer to the diagnosis. This consists of a spreading annular erythema that extends slowly outwards, usually on the trunk or limbs. It may be accompanied by systemic disturbances such as fever, headache or backache. Neurological manifestations develop in some 15% of cases during the ensuing weeks or months, or can be the presenting feature. Occasional patients are left with chronic fatigue and sometimes mild neuropsychological impairments. False negatives and false positives can occur, but rising titres over several weeks may give definitive evidence of the infection. Treatment consists of penicillin or tetracycline and should be given promptly once the skin rash is detected. In the presence of neurological complications penicillin must be given parenterally, and cefotaxime may be required (Muhlemann 1992). Typhus fever Of the several varieties of typhus, that due to Rickettsia prowazekii is the most common. Epidemics are intimately associated with famines and wars and the infection is transmitted by the body louse. Mental and neurological manifestations are usually prominent, and there is abundant evidence that the causative organism invades the nervous system directly. The rickettsiae invade the endothelial cells of small blood vessels, producing foci of thrombosis and necrosis in various organs including the brain. Symptoms consist of pyrexia, delirium, malaise, severe headache, cough and generalised aching. More definite nervous system manifestations appear towards the end of the febrile period and are of serious import. Headache becomes continuous and periods of delirium alternate with stupor or coma. Focal signs appear in the form of hemiplegia, ataxia, bulbar dysfunction, deafness or optic neuritis. Trypanosomiasis (sleeping sickness) the South African forms of trypanosomiasis are due to the protozoans Trypanosoma brucei gambiense and T.
Adjectives-perfect, faultless; indefective, indeficient, indefectible; immaculate, spotless, impeccable; unblemished, sound, scatheless, unscathed, intact; right as rain; consummate, finished, best, model, standard, state-ofthe-art; inimitable, unparalleled, nonpareil; superhuman, divine, fit for the gods; sans peur et sans reproche. Phrases-trifles make perfection, but perfection is no trifle; practice makes perfect. Quotations-Faultless to a fault (Robert Browning), Perfection of means and confusion of goals seem, in my opinion, to characterize our age (Albert Einstein), What is so rare as a day in June? Adjectives-permanent, stable, fixed, standing, immovable, immutable, established, settled, steadfast; constant, eternal, lifelong, lasting, durable, persistent, unending, perpetual, monotonous; unfading, unfailing, etc. Adverbs-in statu quo, as usual; at a standstill, permanently, finally, for permanent [588] perpetuity good, forever. Adjectives-permitting, permissive, indulgent; permitted, permissible, allowable, lawful (see legality); unconditional. Adverbs-permissibly, by leave, with leave, on leave; under favor of; ad libitum, freely; with no holds barred. Verbs-last or endure forever, have no end, never end or die; perpetuate, eternalize, eternize, immortalize, continue, preserve. Adjectives-perpetual, everlasting, unceasing, endless, ageless, unending, having no end; [co-]eternal, everliving, everflowing, sempiternal, continual, ceaseless, incessant, uninterrupted, interminable, infinite, neverending; unfailing, evergreen, amaranthine; deathless, immortal, undying, imperishable, perdurable; permanent, lasting, enduring; perennial, long-lived, dateless, illimitable, continued, constant. Adverbs-perpetually, in perpetuity, always, ever[more], aye; forever, forevermore, for aye, forever and a day, forever and ever; in all ages, from age to age, without end, world without end, time without end; to the end of time, to the crack of doom; till death [do us part], till doomsday, till kingdom come; constantly. Informal, for keeps, for good [and all], until hell freezes over, till the cows come home. Gramophone, Graphophone, Panatrope, Victrola, record player; pickup, playback, turntable; dictating machine. Verbs-photograph, take a picture (of), snap; X-ray, radiograph; develop, process, print, blow up, enlarge; project. Quotations-The camera is an instrument that teaches people how to see without a camera (Dorothea Lange); Photography is a moment of embarrassment and a lifetime of pleasure (Tony Benn). Adjectives-pious, religious, devout, devoted, reverent, godly, humble, pure, holy, spiritual, pietistic; saintly, saintlike; seraphic, sacred, solemn; believing, faithful, Christian, Catholic; holier-than-thou; elected, adopted, justified, sanctified, beatified, canonized, regenerate[d], inspired, consecrated, converted, unearthly, inexpressible. Mencken), And I could wish my days to be bound each to each by natural piety (William Wordsworth), My atheism. Adjectives-pitying, piteous, pitiful, pitiable; compassionate, sympathetic, affected, touched; merciful, clement, ruthful; humane; humanitarian, philanthropic, tenderhearted, softhearted, lenient; melting, weak. Quotations-Then cherish pity, lest you drive an angel from your door (William Blake), Pity is the virtue of the law (Shakespeare), One cannot weep for the entire world. One must choose (Jean Anouilh), No beast so fierce but knows some touch of pity (Shakespeare). Verbs-1, plan, scheme; design, frame, diagram, sketch, map, lay off, delineate, figure, represent. Adjectives-1, pleased, glad[some]; pleased as Punch; happy as a king, as a lark, or as the day is long; thrice blest; in clover, in paradise, in raptures, on top of the world; overjoyed, entranced, etc. Quotations-Poetry is eloquent painting (Simonides), All poets are mad (Robert Burton), That willing suspension of disbelief for the moment, which constitutes poetic faith (Samuel Taylor Coleridge), Poets are the unacknowledged legislators of the world (Percy Bysshe Shelley), Poetry is the achievement of the synthesis of hyacinths and biscuits (Carl Sandburg), A poem should not mean but be (Archibald MacLeish), Writing a book of poetry is like dropping a rose petal down the Grand Canyon and waiting for the echo (Don Marquis), Genuine poetry can communicate before it is understood (T. Eliot), If poetry comes not as naturally as the pogrom [603] polish leaves to a tree, it had better not come at all (John Keats). Grundy, Philistine, Babbitt; Joe Blow, Joe Doakes, John or Jane Doe, John or Jane Q. Adjectives-popular; plebeian, proletarian, common, democratic; homely, homespun; vulgar, lowborn, ignoble, illbred, baseborn, earthy; unknown to fame, obscure, untitled; rustic, countrified, provincial; loutish, boorish, clownish, churlish; barbarous, barbarian, barbaric. Quotations-In the common people there is no wisdom, no penetration, no power of judgment (Cicero), All the world over, I will back the masses against the classes (William Gladstone), There is not a more mean, stupid, dastardly, pitiful, selfish, spiteful, envious, ungrateful animal than the public. It is the greatest of cowards, for it is afraid of itself (William Hazlitt), the people are a many-headed beast (Horace), the people are the only sure reliance for the preservation of our liberty (Thomas Jefferson), the people, and the people alone, are the motive force in the making of world history (Mao Zedung). Phrases-a bird in the hand is worth two in the bush; easy come easy go; you cannot lose what you never had; possession is nine points of the law. Quotations-For we brought nothing into this world, and it is certain we can carry nothing out (Bible), Things are in the saddle, and ride mankind (Emerson), Property is organized robbery (G. Verbs-be possible, stand a chance or show; admit of, bear; put in the way of; open up.
First admissions to hospital with the condition have ranged from 65 per million population in Queensland, Australia to 8 per million in New York. No obvious correlations can be discerned with the per-capita consumptions of alcohol in these different countries. Numerous factors are likely to be involved: the beverage consumed, its thiamine content, patterns of drinking and patterns of dietary neglect. However, there may be an important additional factor by way of personal susceptibility. Thiamine is important in relation to several key enzyme systems of the body and brain. This applies to enzymes such as transketolase, which is essential for the maintenance and synthesis of myelin, and the pyruvate dehydrogenase complex and -ketoglutarate dehydrogenase complex, both of which play key roles in brain glucose metabolism and energy production (Langlais 1995). Certain variants have seemed to be specific to Korsakoff patients (Blass & Gibson 1977; Nixon 1984). Reductions in -ketoglutarate dehydrogenase were particularly severe, and Butterworth et al. During the Second World War, however, experience in prisoner of war camps gave ample opportunity for observing relatively acute deficiency syndromes in large numbers of subjects. In epidemics of beriberi psychological changes were often found to be prominent, with irritability, depression and disturbance of memory (Cruickshank 1961). The authors proposed that the encephalopathy appeared when particularly acute and severe thiamine depletion was superimposed on partial deficiency, whereas other forms of beriberi generally resulted from less severe and more prolonged lack of the vitamin. In almost all their cases the encephalopathy had set in when Addictive and Toxic Disorders 701 some other factor, such as epidemic diarrhoea, had intensified the vitamin deficiency. The situation was thus analogous to that seen with nicotinic acid, where severe acute depletion produces profound evidence of cerebral dysfunction and more chronic deficiency leads to pellagra. In addition to objective signs there were often subjective complaints of weakness, paraesthesiae and pain. Common signs were redness or papillary atrophy of the tongue, cheilosis, angular stomatitis, telangiectases, and dryness and discoloration of the skin. Two-thirds of the patients showed evidence of liver disorder and one-quarter were bedridden when first seen. Overt signs of beriberi were rare but resting tachycardia and dyspnoea on effort were common. Abstinence syndrome was found at inception in 13%, with epileptic fits, hallucinoses or delirium tremens. Mental abnormalities were observed in 90% of patients, the rest presenting with ataxia and ophthalmoplegia but remaining lucid throughout. The commonest mental disturbance was a state of quiet global confusion, with disorientation, apathy and derangement of memory. Many were drowsy, sometimes falling asleep in mid-sentence, while others showed marked indifference and inattention to their surroundings. Against the prevailing view, however, almost all were readily rousable and impairment of consciousness was rarely profound or persistent. In the typical case, spontaneous activity and speech were minimal, and remarks irrational and inconsistent. Physical and mental fatiguability was pronounced, and concentration was difficult for the simplest task. In contrast, a small proportion were alert, responsive and voluble, despite obvious confusion and defects of memory. Evidence of delirium was sometimes seen, with perceptual distortions, vivid hallucinations, insomnia, agitation and autonomic overactivity. In a small number this amounted to frank delirium tremens, but was always evanescent and usually not severe. Loosely knit delusions appeared occasionally and sometimes persisted for weeks after the confusion had cleared.
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