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Neuropsychiatric disorders 

Neuropsychiatric disorders

Chapter:
Neuropsychiatric disorders
Author(s):

Mervi L.S. Pitkanen

, Tom Stevens

, and Michael D. Kopelman

DOI:
10.1093/med/9780199204854.003.2604
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date: 27 April 2017

Neuropsychiatry is concerned with disorders of affect, cognition, and behaviour that arise from overt disorder in cerebral function, or from indirect effects of extracerebral disease.

The clinician needs to have a practical approach to the assessment, investigation, and management of patients manifesting cognitive and behavioural change, and to be aware of the specific cerebral and extracerebral disorders that commonly involve or are accompanied by cognitive or behavioural change.

In the assessment and classification of mental and behavioural disorders it is crucial to: (1) distinguish between acute and chronic disorders—particularly between delirium and dementia; (2) distinguish between cognitive and psychiatric disorder—misdiagnosis of depression presenting as a ‘pseudodementia’, or of delirium as psychosis, are errors that can have dire consequences for the patient; (3) determine whether cognitive impairment is specific or generalized—specific impairments are more likely to be due to a focal brain lesion; and (4) determine whether any underlying condition is reversible or irreversible.

Acute cognitive and behavioural disturbance

Delirium—can be caused by a very wide range of conditions and needs to be distinguished from acute psychosis, which can be difficult. Features that support the diagnosis of delirium are: (1) deficits of attention that may range from distractibility and inability to follow complicated conversations, through an almost complete inability to register information or to concentrate (manifest poor performance on serial subtraction test), progressing in the extreme case to diminished consciousness and coma; (2) attentional difficulties that tend to have a sudden onset and to fluctuate over time; (3) muddled thinking and speech showing considerable perseveration; (4) illusions and hallucinations that tend to include a strong visual component, although auditory hallucinations and misperceptions are common; and (5) delusions are usually simple, persecutory in nature, fluctuating, and transient.

Psychiatric disorders—a past history of psychiatric contact or treatment should be sought in all those with behavioural disturbance. In patients with an underlying psychiatric disorder there is usually a background of insidious behavioural disturbance or personality change. Delusions in psychotic disorders tend to be complex, bizarre, and consistently held, visual hallucinations are rare, and marked attentional and memory deficits are not typical (see Chapter 26.5.7).

Alcohol and substance misuse—about one-quarter of all male medical admissions have a current or previous alcohol problem, and such patients are vulnerable to a large number of complications that may precipitate delirium.

Clinical approach—it is necessary to consider a wide range of factors and medical conditions that can both predispose to and precipitate delirium. A history of alcohol and/or illicit substance misuse is of particular importance. Although not always easy, a thorough physical examination with particular attention to the neurological system is essential. A routine screen—including full blood count, electrolyte, and γ‎-glutamyl transferase (GGT) measurements, liver and thyroid function tests, glucose estimation, and C-reactive protein (CRP)/erythrocyte sedimentation rate (ESR)—is required, as this might indicate delirium where the diagnosis is in doubt. Infection is implicated in around one-third of hospital inpatients who are delirious, and a midstream urine sample (MSU) and chest radiograph are usually warranted. Relevant history and findings on physical examination determine the need for more specific investigation, e.g. brain CT, lumbar puncture, malarial blood film.

Management—delirium is a medical emergency. Management consists of treating the underlying causes and containment of any behavioural disturbance with general measures in the first instance, including nursing in a bright, simple room with minimal changes in staff and good lighting at night. Where sedation is required, then a regular oral antipsychotic such as haloperidol can be administered (see Chapter 26.3).

Chronic and subacute cognitive and behavioural disturbance

The diagnostic challenges in this group of patients are exemplified by the complex differentiation between dementia and depression or ‘depressive pseudodementia’.

Dementia—this is a progressive neurodegenerative syndrome involving a pervasive impairment of higher cortical functions resulting from widespread brain pathology. Reversible causes must be excluded. A typical diagnostic screen will include a full blood count, electrolyte and metabolic screen, thyroid screen, vitamin B12 and folate levels, syphilis serology, urinalysis, chest radiography, electrocardiography, and CT/MRI brain imaging. In some cases, lumbar puncture, electroencephalography, and (rarely) brain biopsy will be required. Functional brain imaging is likely to assume greater importance in the future.

Focal cognitive disorders—a variety of neuropsychiatric syndromes may arise from regional cerebral impairments of diverse cause and may present in the absence of generalized cognitive impairment: frontal lobe, temporal lobe, parietal lobe, and diencephalic syndromes are recognized.

Organic comorbidity in psychiatric disorders

Missing an underlying ‘organic’ diagnosis remains a continuing concern for clinicians responsible for the assessment and treatment of new cases of an apparent psychiatric disorder. (1) Organic psychotic disorder—debate remains over the degree of investigation appropriate at the onset of psychosis. Patients with cognitive impairment, abnormal neurological signs, atypical illnesses not responding to treatment, or other indications from the history, certainly warrant further investigations. Where appropriate, this should include neuroimaging, electroencephalography, syphilis serology, and other investigations indicated by the clinical picture. (2) Organic mood disorder—a variety of medical conditions are associated with prominent affective disorder. (3) Organic personality disorder—insidious changes in personality may reflect frontal lobe pathology.

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