LETTERS TO THE EDITOR it is only a fraction of the $38 billion spent for direct medical and nursing services for demented elderly and an even smaller proportion of the estimated $88 billion (more likely $140 billion) in medical and social costs of these disorders. The only approximation of a population study of cases of dementia pre-CT was the 1,000 consecutive autopsies of Jellinger,’ among whom 1 % had hydrocephalus and 5% had brain tumors. If, due to the older population and consequently greater incidence of Alzheimer’s disease now, only 2% (rather than 6%) were to have structural lesions, that would still be 4 to 8 thousand individuals who might be misdiagnosed clinically. Our analysis of the first 2,097 cases seen at nine State of California Alzheimer’s Disease Diagnostic and Treatment Centers (ADDTC) found an incidence of 0.5% for spaceoccupying lesions alone as the cause of dementia. Three quarters of cases (9/12) had neither focal neurologic exams nor histories of falls or recent trauma, and 9/12 had also previously been diagnosed as Alzheimer’s disease. Given that all of these patients had prior medical evaluations for dementia (median duration of dementia 3 years, range 0-12 years), we must conclude that even skilled clinicianswill miss spaceoccupying lesions that cause dementia. 3. In addition, new criteria for the diagnosis of vascular dementia will require evidence by CT or MRI of the presence of one or more infarcts. Among the 2,097 ADDTC patients, 98/424 with a diagnosis of vascular dementia also had nonfocal neurologic examinations. This diagnosis has become more important as evidence accumulates that vigorous treatment of risk factors can stop progression or even lead to improvement. Less aggressive control of these cardiovascular risk factors might be indicated for the Alzheimer’s patients. 4.Although the clinical criteria suggested by Drs. Clarfield and Larson may be so good that no imaging procedure is required, this has not been proven in a prospective study. Certainly the patient reported by Friedland, a severely demented individual who responded dramatically to shunting, would not have met these criteria if first examined at the REFERENCES time the shunt was p l a ~ e d . ~ 1. Katzman R, JacksonJE.Alzheimer’s disease: Basic and clinical advances. J We continue to be concerned that, in the absence of an Am Geriatr SOC1991;39:516-525. imaging procedure, truly treatable cases of dementia will be 2. Katzman R. Should a major neuroimaging procedure (CT or MRI) be required in the workup of dementia? An affirmative view. J Fam Pract inadvertently missed, with tragic human consequences as 1990;31:401-405. well as increased cost to society. 3. Clarfield AM, Larson EB. Should a major imaging procedure (CT or MRI) ROBERTKATZMAN,MD be required in the workup of dementia? An unopposing view. J Fam Pract 1990;31:405-410. J. EDWARD JACKSON, MD 4. Clarfield AM, Bass MJ,Cohen C et al. Assessing dementia: The Canadian University of California, San Diego consensus (Editorial).Can Med Assoc J 1991;144:851-853. San Diego, CA 5. Canadian Consensus Conference on the Assessment of Dementia. Cana-
Advances in Alzheimer‘s Disease To the Editor:-I very much enjoyed the comprehensive review by Drs. Katzman and Jackson on advances in Alzheimer’s disease.’ 1 was, however, disappointed with their treatment of the question as to whether neuroimaging was required for the diagnosis of all patients with dementia. Dr. Katzman has eloquently presented his side of the argument elsewhere,’ and to their credit, Katzman and Jackson did point out that “some geriatricians have argued that a very typical case of AD may be diagnosed without the use of scans.” Unfortunately, they do not reference this statement and so the interested reader cannot easily be directed to the appropriate literature dealing with this point of view. I and a colleague3and others (hardly only ”some geriatrician~“)~, have argued that, as for all laboratory tests, there are specific conditions suggesting referral for neuroimaging. These include: (1) age < 60 years, (2) the use of anticoagulants and/or history of bleeding disorders, (3) recent head trauma, (4)previous history of carcinoma (from sites that metastasize to brain-eg lung, breast), (5) unexplained neurological symptoms(eg new onset headaches, seizures),(6) rapid unexplained decline (eg over 1-2 months) in cognition and/or function status, (7) ”short”duration of dementia (
Advances in Alzheimer‘s Disease To the Editor:-I very much enjoyed the comprehensive review by Drs. Katzman and Jackson on advances in Alzheimer’s disease.’ 1 was, however, disappointed with their treatment of the question as to whether neuroimaging was required for the diagnosis of all patients with dementia. Dr. Katzman has eloquently presented his side of the argument elsewhere,’ and to their credit, Katzman and Jackson did point out that “some geriatricians have argued that a very typical case of AD may be diagnosed without the use of scans.” Unfortunately, they do not reference this statement and so the interested reader cannot easily be directed to the appropriate literature dealing with this point of view. I and a colleague3and others (hardly only ”some geriatrician~“)~, have argued that, as for all laboratory tests, there are specific conditions suggesting referral for neuroimaging. These include: (1) age < 60 years, (2) the use of anticoagulants and/or history of bleeding disorders, (3) recent head trauma, (4)previous history of carcinoma (from sites that metastasize to brain-eg lung, breast), (5) unexplained neurological symptoms(eg new onset headaches, seizures),(6) rapid unexplained decline (eg over 1-2 months) in cognition and/or function status, (7) ”short”duration of dementia (
