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Neurological disorders include many diseases and conditions of acute and chronic development. The etiology of these disorders can be infectious, toxic, genetic, traumatic, and ischemic, and related to other chronic pathophysiologies. The occurrence may be at birth, which may confer a lifelong disability, or may occur in middle or late life, which may result in progressive disability and death. Neurological disorders may have an insidious onset or have symptoms that are nonspecific, making classification difficult. Early stages of some disorders are characterized by a variable presentation or by subtle signs and symptoms that are difficult to detect or that go unrecognized. Individuals often ignore symptoms until function is impaired. Some disorders in children may be developmental and may go undetected until the children reach the age at which deficits could be assessed. Hence, recognition, diagnosis, and progression of neurological symptoms may affect the true magnitude and onset of neurological disorders.
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Diagnoses of neurological disorders requires not only recognition of symptoms but confirmation with a neurological examination. The neurological examination may be specific to symptoms and to onset. Diagnostic tests have changed with advances in imaging and electrophysiological testing. The use of computerized tomography (CT) scanning, magnetic resonance imaging (MRI), cerebral blood flow measurement and positron emission tomography (PET) have increased the certainty of diagnoses. Additional cognitive tests developed by neuropsychologists have aided in the diagnosis of cognitive decline. Hence the evaluation of incidence and prevalence over time is difficult due to changing diagnostic criteria and the likelihood of changing classifications and inclusion of milder or early-onset disease.
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The burden of neurological disease is increasingly important as a determinant of health policy in costs and services. The Global Burden of Disease Study utilized the Disability Adjusted Life Years (DALYs) as an estimate of magnitude or burden of diseases.1,2,3 Brain diseases encompass a broad spectrum including neurological, neurosurgical, and psychiatric conditions. Thirty-three percent of the years lived with disability and 13% of the DALYs are from neurological and psychiatric disorders. The major impact of the aging related disorders of Parkinson's disease, Alzheimer's disease, and other dementias and cerebrovascular disease on the global burden is evident world-wide and also in North America (Table 67-1).
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